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Etiology, Diagnosis, and Treatment of Long Bone Fractures in Foals
Etiology, Diagnosis, and Treatment of Long Bone Fractures in Foals J.P. Watkins, DVM, MS, DACVS Long bone fractures in foals are common and in many cases are amenable to current fixation techniques. The goals of management are first and foremost, appropriate first aid in the field to protect the bone and soft tissues from further trauma. An envelope of intact skin overlying the fracture is a major contributor to a successful outcome. Case selection for open reduction and internal fixation should be based on an understanding of the mechanical characteristics and biologic environment of the fracture zone. With few exceptions, double plate fixation is the treatment of choice to ensure a fixation with the requisite stability and strength to allow unrestricted weight bearing on the repaired fracture immediately after surgery. Major complications include problems of the fracture construct, most commonly infection or instability, and axial limb deformities secondary to reduced weight bearing on the injured limb or direct injury to the growth plate following a physeal fracture. Clin Tech Equine Pract 5:296-308 © 2006 Elsevier Inc. All rights reserved. KEYWORDS long bone fractures, physeal fractures, internal fixation, intramedullary nailing
F
ractures are common injuries in foals. They are often the result of either a direct traumatic injury such as being kicked by another horse or a fall. In addition entrapment injuries, when the affected limb has been caught under something substantial, are often implicated. Fortunately, many of the fractures encountered in foals are amenable to open reduction and internal fixation (ORIF). Providing a bone implant construct with adequate stability and strength to allow full weight bearing in the immediate postoperative period is much more likely in a foal than an adult with a comparable fracture. The smaller size of the patient, combined with fracture configurations that are often more reliably reconstructed, and implants more suited to patient size, are factors that biomechanically favor fracture reconstruction in foals. In addition, healing time is markedly reduced in foals compared with adults. Biomechanical and biological factors considered, foal fractures are attractive opportunities for applying the principles of internal fixation.
Fracture Management Concepts The goal of fracture management is to provide a mechanical and biologic environment at the fracture site conducive to healing that, at the same time, will allow an early return to full
Department of Large Animal Medicine and Science, College of Veterinary Medicine, Texas A&M University, College Station, TX. Address reprint requests to Dr. J.P. Watkins, Texas A&M University, College of Veterinary Medicine, Department of Large Animal Medicine and Science, MS 4475, College Station, TX 77843. E-mail: [email protected]. edu
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1534-7516/06/$-see front matter © 2006 Elsevier Inc. All rights reserved. doi:10.1053/j.ctep.2006.09.004
weight bearing on the injured limb. If these goals are not achieved, the likely outcome is failure of the construct and/or the support limb. There are numerous mechanical limitations to successfully repairing an equine fracture, not the least of which is that most of the available implants are designed for use in humans where fracture forces are substantially less and can be controlled by limiting the amount of weight bearing during the immediate postoperative period. In equine fracture patients, we rely on the implants and repaired bone to share the loads during healing and require that full weight bearing on the injured limb commences as soon as possible following surgery. For best results, fractures must be repaired with adequate purchase in the fracture fragments to allow the bone and implants to share responsibility for transmitting forces through the construct. Certain principles are well defined and should be adhered to: anatomic reduction; double plate fixation (with some exceptions) applying AO (arbeitgemeinshaft für osteosynthesefragen) principles; fixation spanning the maximal length of the bone, filling all screw holes in the plates with screws and placing as many screws as possible across the fracture in lag fashion; and making use of 5.5-mm screws through the end holes of the plate(s) as well as on either side of the fracture. Difficulties arise when a fracture segment is insufficient in length to allow adequate purchase using standard implants. With standard plates we strive for bicortical purchase with a minimum of 7 screws (usually divided between 2 plates) in the major proximal and distal fracture segments. If this is not possible, consideration should be given to using special implant systems designed to increase purchase in the short fracture segment such as the
Long bone fractures dynamic condylar screw plate (DCS), Cobra head, or condylar buttress plates. Comminution adds another dimension of difficulty to the repair. Large fragments, which allow multiple lag screws for interfragmentary compression, and those that can be positioned beneath plates are most easily managed. Small fragments, which cannot be stabilized by multiple lag screws or trapped beneath a plate, as well as fragments located in the cortex subjected to compressive loads, increase the risk of construct failure. Double plate fixation, using a combination of a broad and narrow limited contact dynamic compression plate (LC-DCP), as described previously, has long been considered the standard construct for equine fracture fixation. (Please note that the LC-DCP has replaced the DCP in the United States since 2005). However, high risk repairs require stronger, more fatigue-resistant constructs. Indications for such constructs include: patients whose body weight exceeds 200 kg, especially for fractures above the carpus and tarsus; fractures with significant comminution as described previously; and simple fractures with significant compromise to the soft tissue envelope. Methods to increase the strength and resistance to fatigue failure of the construct include: using 5.5-mm cortex screws throughout the length of one or both plates; using stronger plates, either two broad LC-DCPs or using the stronger DCS or Cobra head plate in place of one of the broad LC-DCPs; luting one or both plates with polymethylmethacrylate (PMMA); and for lower limb fractures, using a cast in conjunction with internal fixation. Large plates, with both plates luted and applied using as many 5.5-mm bone screws as possible, are the strongest, most fatigue-resistant constructs currently available and are strongly advocated for high risk repairs in larger patients. Recently the locking compression plate (LCP) was introduced to human and veterinary surgery.1 This plate, which contains combi holes (Fig. 1), where either a regular cortex screw or a locking screw can be inserted, has a lot of potential in equine fracture repair.2 The locking screws contain threads at the screw head that interlock in the matching threads within the plate hole and result in a solid and very stiff construct. The locking screws must be inserted perpendicular relative to the long axis of the plate. While being completely accepted in human trauma surgery, the new plate is presently gaining popularity among veterinary surgeons. Fracture healing relies on the favorable interaction between the mechanical environment discussed previously and the biologic environment provided by the soft tissues enveloping the fracture. If the biologic environment is substantially compromised, healing is unlikely, even if the mechanical limitations to healing have been minimized. Complete disruption of the neurovascular supply at the fracture site is obviously the most devastating compromise to healing and affected horses should be euthanatized. Fortunately this degree of soft tissue compromise is rare. However, infection is not uncommon and is arguable the most clinically important biologic limitation to fracture healing in the equine patient. Infection is a consequence of bacterial contamination, either from a penetrating injury at the fracture site or acquired during open reduction and internal fixation, and is directly
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Figure 1 Graphic representation of the combi hole, which is found in the locking compression plate (LCP) (Synthes Inc. Westchester, PA). A standard cortex screw can be implanted through the left (nonthreaded) side of the combi hole, which represents one-half of a dynamic compression unit (DCU) hole (below left). A special locking screw with complementary threads manufactured over the screw head threads into the right (threaded) sided of the combi hole (below right). Obviously only one screw can be inserted through one combi hole.
related to the degree of soft tissue injury and the surgery time. Soft tissue injury arises from three sources: the initial trauma, which resulted in the fracture, trauma caused by sharp bone fragments while the fracture is unstable, and trauma resulting from surgical invasion to repair the fracture. Although many long bone fractures can now be successfully repaired, some are outside the domain of feasibility and necessitate humane destruction of the patient. A list of the various factors contributing to a decision for euthanasia is long and varied. Clearly, certain fractures dictate humane destruction of the patient because the mechanical and biological environment requisite for healing cannot be achieved. Unfortunately, there are a number of fractures where fixation and healing are well within the capabilities of current fixation techniques, but other considerations necessitate destroying the patient. These include monetary constraints placed on therapy by the owner as well as the owner’s expectations for future performance once healing has occurred.
Specific Long Bone Fractures Ulna/Olecranon Olecranon fractures are the most common foal long bone fracture repaired in our hospital. These fractures frequently result from the foal falling on the affected limb. It is likely that when the foal falls and the point of the elbow impacts the ground, shear forces initiate the fracture at the caudal aspect of the physis and the forceful contraction of the triceps muscle propagates the fracture cranially. In neonates, the fracture remains confined to the physis (type 1a), but in older foals, the fracture also involves the metaphyseal bone and propagates craniodistally toward the anconeal process (type 1b). The cranial aspect of the fracture may remain nonarticular,
298 but more commonly violates the articular surface in the proximal aspect of the trochlear notch. It is important to note that because the olecranon process is an apophysis and not a true pressure epiphysis, the use of the Salter-Harris scheme for categorizing these fractures is inappropriate. Another common fracture, likely the result of a kick injury to the caudolateral aspect of the olecranon, is a type 2 fracture, where the body of the olecranon distal to the physis is fractured in a transverse manner into the articulation. Foals with these injuries are usually presented as nonweight bearing lame with the limb typically held in flexion. With displaced fractures there is a dropped elbow appearance and there may be moderate to severe swelling in the region of the elbow. Inability to support weight on the affected limb stems from incapacitation of the triceps apparatus and the inability to fix the carpus in extension. Differential diagnoses include fracture of the humerus, radial nerve injury, and scapular neck fractures. The latter two are rare; however, it is imperative to delineate between fractures of the humerus and olecranon, as emergency coaptation in the former is contraindicated (see discussion on humeral fractures). Radiographic examination provides the definitive diagnosis with the most diagnostic view obtained by extending the limb and taking a medial to lateral projection. However, it is important to obtain a craniocaudal view as well, especially with fractures located more distally in the olecranon to ascertain if there is an accompanying injury to the proximal radial physis (see discussion on physeal fractures). Emergency coaptation consists of a well-padded bandage with a rigid splint affixed to the caudal aspect of the limb, extending from the ground to near the point of the elbow. Splinting the carpus in extension allows the foal to bear weight and will minimize further fragment distraction as well as reduce patient fatigue and stress associated with inability to bear weight on the fractured limb during transport and in the preoperative period. In cases of nonarticular nondisplaced fractures, conservative management using elbow to ground splintage and stall confinement can be considered. However, the degree and duration of lameness associated with conservative therapy predispose to complications in both the fractured and support limbs. Attempting to manage a displaced or articular fracture by conservative methods will almost always result in complications and is not recommended. The majority of olecranon fractures are best managed by open reduction and internal fixation (ORIF). The tensile forces of the triceps attachment on the olecranon apophysis result in a reliable biomechanical configuration and fixation using the tension band principle provides a dependable bone implant construct. Surgical fixation restores the weight-bearing function of the limb by reestablishing the triceps mechanism and allows restoration of articular congruency in fractures that enter the humeroulnar joint. The author prefers to use a narrow DCP or LC-DCP applied to the proximal and caudal aspect of the olecranon process (Fig. 2). The bone is approached using a standard caudolateral approach with dissection between the ulnaris lateralis and ulnar head of the deep digital flexor muscles. Fracture reduction is facilitated by grasping the apophysis with pointed reduction forceps and applying caudodistal traction. With the fracture held in reduction an appropriate
J.P. Watkins
Figure 2 Tension band fixation of type 1b olecranon fracture. A narrow 11-hole DCP has been contoured over the proximal aspect of epiphysis and 2 screws through the plate were placed in lag fashion across the oblique fracture. Note the screws were only placed into the ulna.
length plate is applied to the proximal and caudal aspect of the olecranon process. The proximal aspect of the plate is contoured to curl over the apophyseal fragment to allow purchase with 3 plate screws. Depending on the fracture configuration, one or two plate screws are placed across the fracture in lag fashion engaging the cranial cortex of the metaphysis, with the remainder of the plate screws engaging only the olecranon. Screws in the region of the trochlear notch are monocortical and care is taken with the distal screws to avoid transfixing the radius and ulna. If the radius is inadvertently engaged, incongruence of the humeroulnar articulation will occur, particularly in young foals. In general, the prognosis for healing is excellent with plate fixation, and once healed, most patients are able to function as intended. In a review of our patient population, there were 41 fractures of the olecranon in patients less than 1 year of age.3 Twenty-four fractures (59%) were classified as type 1b. Twenty of the type 1b fractures were repaired as described previously. Sixteen fractures were articular and 10 had some degree of comminution. Nineteen of the 20 patients were discharged from the hospital. One patient was euthanatized postoperatively as a result of a ruptured cecum. Sixteen patients were available for long-term follow-up. Twelve patients were more than 2 years of age at follow-up and 9 were being used as intended in a variety of performance activities with-
Long bone fractures out problems related to the fracture. Four patients were less than 2 years of age and were reported to be free of lameness. Overall, plate fixation was deemed successful in 16 of 20 patients, with an excellent outcome in 13. In contrast, a report detailing conservative management of type 1b fractures listed only 6 of 18 patients with a successful outcome, clearly demonstrating the superiority of ORIF in managing this injury.4 Similar results have been reported with plate fixation of type 2 fractures. Although less common in our patient population, type 2 fractures have been the subject of a number of reports.5,6 Overall, 17 of 20 type 2 fractures treated by plate fixation had successful outcomes compared with only 1 of 6 managed conservatively. Pins and wires have also been used successfully. The author has limited experience with this fixation method, but in one report, 4 foals with type 1a fractures and 3 of 4 foals with type 1b fractures were treated successfully.7 Potential advantages of pin and wire fixation include less dissection of the triceps insertion on the olecranon apophysis and reduced likelihood of secondary fracture of the apophysis. In addition, penetration of the articulation by implants and radioulnar transfixation are not likely. However, in vitro mechanical studies have shown the strength and fatigue life of the fixation to be significantly lower than plate fixation. It is the author’s opinion that pin and wire fixation should be reserved for use in neonates with markedly displaced, nonarticular apophyseal fractures in which there is an increased potential for secondary apophyseal failure and the small size of the patients reduces the likelihood of implant failure.
Humerus In our hospital the humerus is the second most common foal long bone fracture encountered. In neonates a direct blow from a kick is the common cause of injury. More commonly, the affected foal is older and has a history of falling on the affected limb. The resultant short oblique or spiral fracture configuration likely occurs when the fall occurs with the limb in adduction. Clinical signs are similar to an olecranon fracture, that is, dropped elbow stance with the limb held in flexion. Swelling is more consistent with humeral fractures and is best viewed from the cranial aspect where thickening of the brachial region is very apparent. A medial to lateral radiograph taken with slight cranial to caudal obliquity best defines the fracture. In addition, a caudal to cranial view with the radiographic beam directed slightly from proximolateral to distomedial further delineates the fracture configuration and relative position of the fragments. First aid measures aimed at stabilizing the fracture and minimizing secondary soft tissue and bone trauma are not possible. It should be noted that splinting the distal limb in extension, as described for olecranon fractures, will allow limited weight bearing on the affected limb, but in the author’s opinion is contraindicated. Encouraging the foal to use the affected limb will result in further damage to the soft tissues, primarily the brachialis muscle and radial nerve, by the sharp fracture fragments. Additionally the splinting adds weight to the limb distal to the fracture and induces increased leverage forces, causing further trauma in the fracture region.
299 Alternatives for definitive therapy include stall confinement, plate fixation using a cranial approach, stacked pin fixation, and interlocking nail fixation. Fractures most suited for conservative management are minimally displaced, long oblique fractures in which overriding imparts some degree of stability to the fracture. Fracture healing with conservative management of up to 50% has been reported.8 Complications include mal-union, ipsilateral flexural deformity, especially in the carpal region, and contralateral varus deformity and fetlock hyperextension secondary to the prolonged convalescence. Short oblique and spiral fractures of the mid to distal humerus are typically displaced, markedly overriding, and very unstable and are not good candidates for conservative therapy. Stacked pin fixation, where multiple 1/4 inch and 1/16 inch Steinmann pins are used to fill the medullary canal, has been successful in some instances. Limitations with this form of fixation include poor rotational stability and the tendency for pin loosening and migration. Cranial plating is an alternative, and if needed a second plate can be applied laterally.9 Limitations to plate application include the complex surface anatomy of the humerus and the closely applied soft tissue investment, including the brachialis muscle and radial nerve in the musculospiral groove. Implant loosening with subsequent instability is also a major concern. The majority of the author’s experience has been with interlocking nail fixation using a custom designed implant system. Selecting a modified lateral approach, the fracture is reduced following reaming of the medullary canal of the proximal and distal fracture segments. The nail is placed in the medullary canal and the proximal and distal fracture segments are transfixed to the intramedullary nail by positioning 5.5-mm cortex bone screws through preplaced holes in the nail (Fig. 3). Biomechanically this form of fixation is capable of preventing collapse at the fracture site and neutralizing bending and rotational forces. Furthermore, implant migration is prevented. As with all forms of fixation, the location and configuration of the fracture significantly affects the strength and stability of the construct. Ideally, three interlocking screws are positioned on either side of the fracture. In large foals or when the fracture configuration does not allow adequate screw fixation in either the proximal or distal fracture segments, a bone plate is applied to the cranial surface of the humerus to augment the fixation. Results with interlocking nail fixation of humeral fractures in foals at our institution have been encouraging. In our initial report of 10 foals with humeral fractures, 50% of the foals treated—some weighing as much as 220 kg— healed their fractures.10 Foals that healed their fractures attained athletic soundness and fulfilled their intended purpose without complications related to the fractured humerus. Further experience with this technique in a substantial number of additional cases has produced better results.
Femur Diaphyseal fractures of the femur in foals usually result from the foal falling with the affected limb in adduction. In neonates a direct blow from a kick is a more common cause of injury. Clinical signs are highly indicative of a diaphyseal
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J.P. Watkins minimizing secondary soft tissue and bone trauma are not possible. Instability at the fracture and the risk of further soft tissue trauma and hemorrhage are indications for surgical intervention as soon as feasible. The fracture is confirmed by radiographic evaluation, which in some instances can be accomplished on survey films with the patient standing. If surgical intervention is considered, it is advisable to get detailed films once the foal is anesthetized. A medial to lateral and cranial to caudal view with slight lateral to medial obliquity are advised. Most diaphyseal fractures have a spiral or oblique configuration and are often accompanied by some degree of comminution. Comminution of the caudal cortex is of particular concern, as it will negatively affect the prognosis. Neonates often have a mid-diaphyseal transverse configuration when the fracture has resulted from a kick injury. Currently, double plate fixation is considered by most sur-
Figure 3 Intramedullary, interlocking nail fixation of a mid-body humeral fracture in a foal. Each fracture segment has been transfixed to the intramedullary nail by three 5.5-mm cortex screws. No countersinking was conducted but screws inserted through washers increasing contact surface without weakening the bone. Targeting was accomplished using a custom designed targeting device. The radiodense chips are antibiotic impregnated PMMA beads, which were placed along the bone.
fracture and include non-weight-bearing lameness accompanied by substantial soft tissue swelling. Medullary bleeding and damage to the femoral or popliteal artery often result in a massive hematoma and can be life-threatening. Although obvious from a lateral perspective, the swelling is most appreciated when viewed from behind the foal, where the thickness of the thigh region is often twice that of the unaffected limb. First aid measures aimed at stabilizing the fracture and
Figure 4 Double plate fixation of a femur fracture in a foal. One plate was applied to the cranial, the other to the lateral aspect of the bone without involving the physis.
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geons as the technique of choice for definitive management of these injuries.11 A standard lateral approach with dissection between the biceps femoris and vastus lateralis muscles is used to expose the femoral shaft. Reconstruction of the bony column, with emphasis on achieving abutment at the caudal cortex, is important to success. Once the fracture is reduced, a broad DCP or LC-DCP is applied to the lateral aspect of the femur. A second plate is applied cranially to increase the strength and stability of the fixation (Fig. 4). In large foals or foals with complex fractures, it is advisable to use a DCS plate laterally and a broad plate cranially. Using 5.5-mm screws and luting one or both plates will maximize strength and stability of the construct. Success in the range of 50% can be expected with careful case selection in foals weighing less than 250 kg. Postoperative infection is the most significant contributor to failure and appears to be predisposed to by seroma formation. Closed suction drainage in the immediate postoperative period can be used if deemed necessary, to evacuate the seroma. The author has successfully used interlocking nail fixation for femur fractures in foals. In neonates with simple transverse, mid-diaphyseal fractures, interlocking nail fixation, with 3 screws transfixing the nail to the proximal and distal fracture segments, has been used with good results (Fig. 5). In older foals, interlocking nail fixation augmented by a cranial plate has also been successful. Although in vitro testing using a femoral ostectomy model revealed double plate fixation to provide greater strength and stiffness, it has been the author’s experience in a limited number of clinical cases, that nail/plate fixation offers at least equal, if not better, success rates when compared with published results of double plate fixation.
Radius Radial fractures in foals are most commonly encountered in the diaphysis of the bone and often result from a kick injury. Blows to the cranial aspect of the radius result in a middiaphyseal, transverse fracture, whereas a kick to the lateral radius will cause an oblique fracture near the junction of the proximal and middle one-thirds of the diaphysis. Clinically affected foals are presented with a flail limb that tends to displace in a valgus manner at the fracture site during attempts of applying weight on the limb. Soft tissue swelling is usually significant and may be accompanied by a wound in the medial antebrachial region. It is in this location that fracture fragments are likely to penetrate the skin because of the limited soft tissue cover and tendency for the sharp fracture fragments to displace into this area when the distal limb deviates laterally. Immediate first aid measures include appropriate wound therapy and broad-spectrum antibiotic administration for open fractures and external coaptation to provide stability to the fracture and protect the bone and soft tissues from further trauma. A full limb, modified RobertJones bandage, applied in successive well-compressed layers, is recommended. A caudal splint extending from the level of the hoof to the olecranon process, in conjunction with a lateral splint extending from the hoof beyond the proximal end of the bandage and over the lateral aspect of the shoulder region, will provide stability and prevent abduction of the distal limb, thereby minimizing medial displacement of the
Figure 5 Intramedullary, interlocking nail fixation of a femoral fracture in a foal. The distal aspect crosses the physis perpendicularly to its orientation and penetrates the epiphysis. No detrimental effect was discovered.
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Figure 6 Postoperative radiographic views of a double plate fixation of a radius fracture in a foal. The cranial plate covers the entire bone and the plates were applied perpendicular relative to each other. PMMA beads were applied to prevent infection.
fracture fragments. In small foals the splints can be affixed to the bandage using inelastic tape. In larger foals, two rolls of fiberglass cast material work well in place of tape. Plate fixation is the best method for managing radial fractures. A craniolateral approach to the radius, with dissection between the extensor carpi radialis and common digital extensor muscles, allows plate application on either the cranial or lateral aspect of the bone. A medial approach to the radius is used only in exceptional circumstances. The lack of overlying musculature medially and the tendency for more extensive damage to the soft tissues overlying the fracture in this area make a medial approach less desirable in the author’s opinion. Transverse fractures of the mid-diaphysis in small foals can be managed with a single broad DCP or LC-DCP applied to the cranial aspect of the radius. With anatomic reconstruction, the plate is loaded in tension because of the strong cranial curvature of the radius. Double plate fixation is recommended for all other diaphyseal fractures including proximal oblique fractures where the number of screws in the smaller proximal fragment should be maximized (Fig. 6). In small foals, a cranial broad plate and lateral narrow plate may suffice. As the size of the patient increases or with more complex fracture configurations, two broad plates are recommended. Using 5.5-mm screws and luting one or both plates will maximize strength and stability of the construct. Anatomic reconstruction of the fracture, with particular attention given to the caudal cortex, is a prerequisite for successful fixation.
Displaced radial fractures in foals, particularly if comminution is not present and the fracture is closed, have a relatively good prognosis for fracture healing with the majority of healed patients achieving athletic function.12 In one case series 7 of 7 foals with mid-diaphyseal transverse fractures had successful outcomes following single plate fixation.12 In the same report, 4 of 7 foals with proximal oblique fractures healed their fracture, with 3 able to perform athletically following double plate fixation. Success for double plate fixation with comminuted fractures was achieved in 2 of 3 foals.
Tibia Diaphyseal fractures of the tibia in foals are not common in our practice. However, those presented are usually oblique or spiral fractures of the mid to distal tibial shaft and result primarily from a kick injury. Clinically affected foals are presented with a flail limb that tends to displace in a valgus manner at the fracture when the limb is loaded. Soft tissue swelling is usually significant and may be accompanied by a wound at the medial aspect of the gaskin. It is in this location that fracture fragments are likely to penetrate the skin because of the limited soft tissue cover and tendency for the sharp fracture fragments to displace into this area when the distal limb deviates laterally. Immediate first aid measures are identical to the ones described for the radius. A lateral splint extending from the hoof beyond the proximal end of the bandage and over the lateral aspect of the hip region will provide stability and prevent abduction
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303 proach to the tibia because of the lack of overlying musculature and the tendency for more extensive damage to the soft tissues medially. A broad plate is appropriately contoured and applied to extend from the cranial distal end of the tibia to the craniomedial aspect of the proximal tibia. The second plate is then applied to the lateral aspect. Long spiral fractures, which allow many of the screws to be placed in lag fashion through the plate and across the fracture line, are ideal candidates for fixation. In small foals, a cranial broad plate and lateral narrow plate may suffice. As the size of the patient increases or with more complex fracture configurations, two broad plates are recommended. Using 5.5-mm screws and luting one or both plates will maximize strength and stability of the construct. Long oblique and spiral fractures of the tibial diaphysis, which are closed, have a relatively good prognosis for fracture healing, with the majority of healed patients achieving athletic function.13 Fractures with comminution and short oblique fractures have been reported to be associated with more postoperative complications.
Third Metacarpal/Metatarsal Bone
Figure 7 Double plate fixation of a tibia fracture in a foal. Note the axially twisted cranial plate needed for good bone-plate contact along its entire length.
of the distal limb, thereby minimizing medial displacement of the fracture fragments. In small foals the splint can be affixed to the bandage using inelastic tape. In larger foals, two rolls of fiberglass cast material work well in place of tape. When adequate bone stock exists both proximal and distal to the fracture, double plate fixation can be used to successfully stabilize the fracture (Fig. 7). A craniolateral approach to the tibia, in which the skin and deep fascial incisions overly the cranial tibial muscle followed by dissection medially to the bone, is favored. The author rarely uses a medial ap-
Diaphyseal third metacarpal/metatarsal (McIII/MtIII) fractures in foals are often the result of a direct blow but also occur from a misstep during vigorous activity. Because of the limited soft tissue envelope in this area, open fractures are common, frequently the result of the sharp fracture fragments penetrating the skin. Diagnosis is usually straightforward: non-eight-bearing lameness accompanied by obvious instability. Immediate efforts must be made to provide emergency coaptation to protect the soft tissues and bone from further damage. In the forelimb, a full limb, modified Robert Jones bandage with rigid splints applied to the caudal and lateral aspects and extending the length of the bandage should be applied. In the hind limb, the bandage and splints should extend from the hoof to the tuber calcis. Dorsopalmar (plantar), lateral to medial, and both oblique views are taken to radiographically characterize the fracture. A major limitation in managing fractures of McIII/MtIII is the lack of overlying musculature and the limited amount of soft tissues available for coverage of space occupying implants and to provide an extraosseous blood supply to support healing. Soft tissue damage and the relatively poor blood supply to the area predispose to infection, particularly if the fracture was open. If infection does occur there appears to be an increased risk of nonunion because of osteomyelitis and the development of large areas of devascularized bone (Fig. 8). Options for managing McIII/MtIII fractures include ORIF using bone plates, external coaptation with either a standard or transfixation cast, or a combination of internal fixation and external coaptation. The method of choice is determined by the mechanical and biological attributes of the injury. In general, plate fixation is preferred, as it provides the most stability to the fracture, thereby promoting an early return to unprotected weight bearing on the fractured limb. However, highly comminuted and open fractures may be better managed by alternative methods.
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J.P. Watkins indicated. McIII is loaded axially, allowing placement of plates on either the dorsal, lateral, or medial surfaces. The dorsolateral cortex of MtIII is loaded in tension and one of the plates should be applied to that surface when possible. In small foals with simple fractures, a broad and narrow plate are adequate. In larger foals or with more complex fractures, two broad plates are advocated. Open fractures and those with substantial comminution are poor candidates for open reduction and plate fixation. The risk of further compromising vascularity to the fracture fragments and promoting infection are too great in these circumstances. If plate fixation is elected it should be performed using minimally invasive techniques and the use of an LCP should be considered. Alternatively, a cast or transfixation cast can be used. Closed fractures managed by double plate fixation have a good prognosis for healing.14,15 Unfortunately, the limb is often noticeably thickened and owners should be made aware that the cosmetic appearance will be impaired. Fractures complicated by infection are much less likely to have a favorable outcome.
Figure 8 Infected fracture construct following single plate fixation of a metacarpal fracture in a foal. Note the large devascularized area in the mid-diaphysis.
Double plate fixation is the method of choice for managing closed diaphyseal fractures, which are not highly comminuted (Fig. 9). A major concern is the ability to reconstruct the soft tissues over the implants; therefore, a transtendinous approach along the common/long digital extensor tendon is
Figure 9 Double plate fixation of a metacarpal fracture in a foal. The plates span the entire bone down to the physis and are applied perpendicular relative to each other. All plate holes were filled with screws.
Long bone fractures
Physeal Fractures Physeal fractures may affect either traction or pressure epiphyses. Traction epiphyses serve as sites of attachment for tendons or ligaments and are subjected primarily to tensile forces. Compression is the major force affecting pressure epiphyses that comprise the articular ends of long bones. The most common traction epiphyseal injury affects the physis of the olecranon process as previously discussed. Injuries to physes associated with pressure epiphyses in the foal occur throughout the appendicular skeleton and account for roughly 20% of foal long bone fractures.16 These fractures result primarily from shear and bending forces concentrated at or near the affected physis and epiphysis. Type I injuries are confined to the physis. Type II injuries traverse along the physis and exit the physis into the metaphysis. Type III and IV injuries involve the epiphysis and adjacent articulation. Type III injuries involve only the epiphysis and physis while type IV injuries cross into the metaphysis. Type V injuries are actually compression fractures of the physis and bone immediately adjacent to the physis. The Salter-Harris classification scheme described above should be reserved to describe only fractures associated with pressure epiphyses. The scheme describes the relationship of the fracture relative to the epiphysis, physis, and metaphysis. In children, as the assigned number increases, the likelihood of a growth disturbance increases and therefore the prognosis decreases. However, in foals the most important aspect of prognosis is potential to restore the weight-bearing function of the limb and therefore the foal’s life. Foals with type I and II injuries, the most common physeal fractures, usually present with non-weight-bearing lameness. Mal-alignment of the bony column and soft tissue swelling are usually evident, dependent on the location of the injury. Manipulation of the limb usually demonstrates instability at the fracture site and induces a painful response. In most cases there is adequate displacement at the fracture site to delineate the type and severity of the fracture with routine radiographic projections. However, if displacement is minimal, particularly with type I injuries, stress radiographs may be necessary to definitively diagnose the fracture. It may also be helpful to take radiographs of the contralateral physis for comparison. Type III and IV injuries are rare, but will present with significant lameness accompanied by effusion in the affected joint. Gross mal-alignment and instability of the limb may or may not be evident with these injuries. With displacement and instability, the injury may appear as a luxation. Radiographs readily define the injury. Type V injuries are rare as well, but are presented with a primary complaint of progressive angular limb deformity. Lameness may not be evident at the time of examination. Radiographs may fail to delineate the injury until transphyseal callus has formed and evidence of partial or complete premature closure of the physis or peripheral bone bridge formation is evident. Differential diagnoses of pain localized to the physis accompanied by swelling and lameness should include septic physitis, direct trauma to the physis, and occasionally severe physeal dysplasia. History, physical and radiographic examination, and in septic physitis, needle aspiration will aid in arriving at the proper diagnosis. When the above clinical signs are accompanied by instability and joint effusion, luxation should be considered.
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Management Management guidelines for physeal fractures in foals are based on the classification of the injury. For type I and II injuries the major emphasis is to reestablish the bony column, usually by ORIF using either screws, wires, pins, or plates. With type III and IV fractures the objective is to realign the articular surface. In these instances lag screws placed parallel to the physis across the fracture lines in the epiphysis and metaphysis may be adequate. Preventing the development of a significant angular deformity is the goal when managing type V injuries. In these cases growth plate retardation on the side of the physis opposite to the transphyseal bone bridge is indicated. If the deformity is noted near the end of prospective growth for the physis then a corrective osteotomy may be necessary if the deformity is severe. The most significant factor reported to influence the prognosis for life following a physeal fracture is the age of the foal.17 Significantly better results were obtained in foals less than 4.5 months of age at the time of injury. In these cases 25% of the foals were sound following treatment, with an additional 25% salvaged for breeding purposes. For the specific fractures discussed below, too few cases have been reported to provide a reasonable prognosis.
Specific Physeal Fractures Femur Fractures affecting the capital femoral physis are usually type I injuries. They usually result from a fall and direct impact on the proximal femoral area. Although affected foals are severely lame immediately after the injury, there is often a significant time interval between injury and presentation because of the lack of obvious instability and swelling. This delay promotes eburnation of the physeal cartilage along the fracture and muscle contracture, both of which markedly complicate surgical management. Care must be taken during the radiographic examination to ensure that the full extent of the injury is delineated. Frequently there will be accompanying fractures of the femoral head and neck or acetabulum.18 In some cases there is an associated coxofemoral luxation. Cases with isolated physeal injury are reasonable candidates for ORIF. Numerous techniques have been described, including stacked pin fixation, dynamic hip screw (DHS) fixation, and lag screw fixation. Lag screw fixation using multiple large screws, either 6.5-mm cancellous or 7.0- or 7.3-mm cannulated screws is recommended. Exposure is achieved via a trochanteric osteotomy and screws are directed from the proximal femoral metaphysis into the femoral head. The procedure is technically demanding and anatomic alignment is difficult to achieve because of muscle contracture and eburnation of the fracture fragments. Most distal femoral physeal fractures are type II injuries. Non-weight-bearing lameness accompanied by substantial swelling in the distal femoral and stifle regions is typical. Radiographs delineate the fracture, most of which have a cranial metaphyseal fragment. The femoral diaphysis overrides caudally and distally. ORIF using plate fixation is advised but difficult in most cases. The degree of overriding and strength of the musculature in the area make reduction particularly challenging. Furthermore, inability to gain substantial purchase in the epiphyseal segment makes it difficult to provide a fracture construct with adequate strength and sta-
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Figure 10 (A) Distal femoral type 2 physeal fracture in a foal. (B) The fracture was repaired using a DCS plate laterally and two narrow DCPs applied cranially, with their most distal screws directed into the femoral condyles.
bility. Plate fixation, using a laterally positioned DCS plate, in conjunction with one or two cranial plates with screws directed across the physis and into the medial and lateral condyles can be successful, but is technically challenging (Fig. 10). Tibia Most physeal fractures of the tibia affect the proximal physis and are of the type II configuration. They usually result from a blow to the lateral aspect of the limb, or in some cases, when a recumbent foal’s limb becomes entrapped and the foal attempts to stand. These injuries are characterized by a lateral metaphyseal fragment and lateral displacement of the distal tibia. Neonates and foals weighing between 100 and 200 kg are most commonly presented to our hospital. Numerous small case series have described a variety of management techniques including: application of a Charnley apparatus, plate fixation,19 lag screw fixation,20 and cross pin fixation.21 The author prefers to manage neonates with a transphyseal bridge using screws and either wires or a cable across the medial aspect of the physis. Once the epiphyseal and metaphyseal screws are in place, a figure-8 wire is applied and tightened, bringing the fracture into alignment. It is advisable to place a second transphyseal bridge to supplement the fixation. In larger foals, we use a narrow DCP or LC-DCP applied medially, with a 6.5-mm cancellous or 5.5-mm cortex screw in the epiphysis (Fig. 11). If possible one or two plate screws distal to the physis are placed into the lateral metaphyseal
fragment, in lag fashion. It is useful to first position a transphyseal bridge with screws and wire (or cable) to achieve fracture reduction, then position the plate. The screws and wire (cable) can either be left in place to supplement the plate fixation, or when deemed necessary, can be replaced by a second narrow DCP or LC-DCP to further augment the strength of the fixation. Radius Most physeal fractures of the radius affect the proximal physis and are associated with a fracture of the ulna at the level of the radial physis. Types I and II injuries are most common and the degree and direction of displacement are variable. It should be noted that if the distal radial fracture segment is displaced cranially, the radial nerve may be injured and result in low radial paresis during the convalescent period (Fig. 12). Nondisplaced fractures can heal with conservative therapy; however, the degree of discomfort and potential for displacement often warrant internal fixation. Displaced fractures require open reduction and plate fixation. In general, a caudal plate is applied to the ulna with the distal plate screws engaging the proximal radius and the plate extending proximally to the olecranon. A second plate is positioned laterally with fixation in the radial epiphysis and proximal metaphysis (Fig. 13). In small foals, a transphyseal bridge using screws and wires may be used in place of the lateral plate. The lateral transphyseal bridge or plate will increase the strength and stability of the fixation. In addition, it helps ensure that transfixation of the olecranon and radius by the caudal plate
Long bone fractures
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Figure 11 (A) Craniocaudal radiographic view of a proximal tibial type 2 physeal facture. (B) Postoperative lateromedial radiographic view of the repaired fracture. One broad 7-hole—and a narrow 9-hole DCP was applied with the proximal most screw of each plate engaging the epiphysis. Additionally a fixation consisting of one epiphyseal and one metaphyseal screw connected with two figure-8 cerclage wires was applied. (C) A craniocaudal follow-up radiographic view shows good healing.
will not cause elbow incongruence by preventing growth at the proximal radial physis.
avoid cast coaptation, a bone plate may be applied as a bridge to the physis opposite the metaphyseal fragment.
Distal McIII/MtIII Physeal fractures of the distal McIII/MtIII are rarely encountered, but appear to occur most frequently in draft foals. They are nearly always a type II injury and occur secondary to the foal being stepped on. These injuries are readily managed in most cases by lag screw fixation of the metaphyseal fragment to the parent bone combined with external stabilization in a short limb cast. In large foals, or if the surgeon wishes to
Proximal Phalanx Rarely fractures of the proximal physis of the proximal phalanx are encountered. Because of the limited amount of longitudinal bone growth, transphyseal bridging techniques using screws and plates can be applied. In minimally displaced type I fractures conservative management with cast application is a valid option.
Complications
Figure 12 Type 2 physeal fracture of the proximal radius with cranial displacement of the distal fragment. The foal was successfully repaired, however suffered from low radial nerve paresis (mild inability to extend the digit) for approximately 2 months following surgery.
Complications associated with fracture management in foals include problems related to the fracture construct and axial deformities. Problems affecting the fracture construct include infection and fixation failure. Infection is directly correlated to the degree of damage to the soft tissues enveloping the fracture. Every effort must be made during the initial assessment phase of management to provide temporary stabilization of the fracture fragments and minimize further injury before definitive therapy. In addition, appropriate antiinfective measures must be taken when the skin overlying the fracture is compromised. Perioperative broad-spectrum antimicrobials and careful monitoring during the postoperative phase of therapy are essential aspects of the prevention and early identification of infection. If infection occurs, early aggressive therapy aimed at preventing accumulation of exudate and definitively identifying offending organisms and their antimicrobial susceptibilities are important. Systemic and local antimicrobial therapy in conjunction with maintenance of fracture stability are prerequisites for success. If instability accompanies infection or a significant portion of the fracture becomes avascular, the fixation is doomed to failure. Construct failure is usually the result of inadequate fixation. In some instances, particularly in very young foals, the quality of bone purchased by the implants predisposes to failure, especially true of the olecranon apophysis in neonates. If bone quality is suspect, implants designed for fixation in osteopenic bone,
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support limb at the time of fracture fixation that provides both lateral and palmar/plantar extension of the solar surface of the hoof. When the physis suffers direct injury, transphyseal bone formation may result in shortening or angular deformity of the affected bone. In most instances of physeal fracture, shortening of the bone as a result of cessation of growth at the fractured physis is an expected consequence. The end result is often not clinically apparent because adjacent joints can increase their degree of extension and maintain overall limb length. Although uncommon, if an angular deformity develops as a result of a peripheral physeal injury, management is directed at retarding physeal growth on the unaffected side of the physis to minimize progression of the deformity.
References
Figure 13 (A) Radiographic views of a type 2 physeal fracture of the proximal radius combined with a multifragment fracture of the ulna in a foal. (B) The fractures were repaired by means of two plates. The caudal 12-hole narrow DCP uses the olecranon to provide plate purchase proximal to the fracture and the remaining distal screws engage the radius distal to the fracture. The fifth screw from the top penetrates the proximal epiphysis of the radius, while the next two screws distally were implanted in lag fashion across the main fracture line. The lateral 6-hole narrow DCP has a single 5.5-mm cortex screw in the proximal radial physis, with the next 2 screws engaging the metaphyseal fragment. On the lateral view several broken screws are seen in the radius. PMMA beads are applied around the repaired fracture.
such as the LCP system, or alternative fixation methods should be used in place of standard plate fixation techniques. Axial deformities result from tendinous disorders or physeal growth disturbances. They usually are secondary and result from prolonged lameness associated with the injury, with the exception of physeal fractures where the growth cartilage of the physis is damaged primarily. Prolonged lameness predisposes the support limb to fetlock hyperextension and varus angular deformity. Flexor contracture may occur in the fractured limb. Preventing these complications is primarily dependent on providing a stable fracture construct, which encourages full weight bearing on the affected limb as soon after surgery as possible. In addition, glue on hoof plates can be a useful adjunct. The author routinely places a hoof plate on the
1. Frigg R: Locking compression plate (LCP): an osteosynthesis plate based on the dynamic compression plate and the point contact fixator (PC-Fix). Injury 32:B63-66, 2001 2. Florin M, Arzdorf M, Linke B, et al: Assessment of stiffness and strength of four different implants available for equine fracture treatment: a study on a 20 degree oblique long bone fracture model using a bone substitute. Vet Surg 34:231-238, 2005 3. Swor TM, Watkins JP, Bahr A, et al: Results of plate fixation of type 1b olecranon fractures in 24 horses. Equine Vet J 35:670-675, 2003 4. Wilson DG, Riedesel E: Nonsurgical management of ulnar fractures in the horse: a retrospective study of 43 cases. Vet Surg 14:283-286, 1985 5. Donecker JM, Bramlage LR, Gabel AA: Retrospective analysis of 20 fracture of the olecranon process of the equine ulna. J Am Vet Med Assoc 185:183-189, 1984 6. Denny HR: The surgical treatment of fracture of the olecranon in the horse. Equine Vet J 19:319-325, 1987 7. Martin F, Richardson DW, Nunamaker DM, et al: Use of tension band wires in horses with fractures of the ulna. 22 cases (1980-1992). J Am Vet Med Assoc 207:1085-1089, 1995 8. Carter BG, Schneider RK, Hardy J, et al: Assessment and treatment of equine humeral fracture: retrospective study of 54 cases (1972-1990). Equine Vet J 25:203-207, 1993 9. Rakestraw PC, Nixon AJ, Kaderly RE, et al: Cranial approach to the humerus for repair of fractures in horses and cattle. Vet Surg 20:1-8, 1991 10. Watkins JP: Intramedullary, interlocking nail fixation of humeral fractures: results in ten foals (1989-1995). Proc Am Assoc Equine Pract 42:172-173, 1996. 11. Hance SR, Bramlage LR, Schneider RK, et al: Retrospective study of 38 cases of femur fractures in horses less than one year of age. Equine Vet J 24:357-363, 1992 12. Sanders-Shamis M, Bramlage LR, Gable AA: Radius fractures in the horses: 47 cases. Equine Vet J 18:432-437, 1986 13. Young DR, Richardson DW, Nunamaker DM, et al: Use of dynamic compression plates for treatment of tibial diaphyseal factures in foals: 9 cases. J Am Vet Med Assoc 194:1755-1760, 1989 14. McClure SR, Watkins JP, Glickman NW, et al: Complete fractures of the third metacarpal or metatarsal bone in horses: 25 cases (19801996). J Am Vet Med Assoc 213:847-850, 1998 15. Beinlich CP, Bramlage LR: Results of plate fixation of third metacarpal and metatarsal diaphyseal fractures. Proc Am Assoc Equine Pract 48: 247-248, 2002 16. Embertson RM, Bramlage LR, Herring DS, et al: Physeal fractures in the horse I: classification and incidence. Vet Surg 15:223-229, 1986 17. Embertson RM, Bramlage LR, Herring DS, et al: Physeal fractures in the horse II: management and outcome. Vet Surg 15:230-236, 1986 18. Hunt DA, Snyder JR, Morgan JP, et al: Femoral capital physeal fractures in 25 foals. Vet Surg 19:41-49, 1990 19. White NA, Blackwell RB, Hoffman PE: Use of a bone plate for repair of proximal physeal fractures of the tibia in two foals. J Am Vet Med Assoc 181:252-254, 1982 20. Wagner PC, DeBowes RM, Grant BD, et al: Cancellous bone screws for repair of proximal growth plate fractures of the tibia in foals. J Am Vet Med Assoc 184:688-691, 1984 21. Watkins JP, Auer JA, Taylor TS: Crosspin fixation of fractures of the proximal tibia in three foals. Vet Surg 14:153-159, 1985
F
ractures are common injuries in foals. They are often the result of either a direct traumatic injury such as being kicked by another horse or a fall. In addition entrapment injuries, when the affected limb has been caught under something substantial, are often implicated. Fortunately, many of the fractures encountered in foals are amenable to open reduction and internal fixation (ORIF). Providing a bone implant construct with adequate stability and strength to allow full weight bearing in the immediate postoperative period is much more likely in a foal than an adult with a comparable fracture. The smaller size of the patient, combined with fracture configurations that are often more reliably reconstructed, and implants more suited to patient size, are factors that biomechanically favor fracture reconstruction in foals. In addition, healing time is markedly reduced in foals compared with adults. Biomechanical and biological factors considered, foal fractures are attractive opportunities for applying the principles of internal fixation.
Fracture Management Concepts The goal of fracture management is to provide a mechanical and biologic environment at the fracture site conducive to healing that, at the same time, will allow an early return to full
Department of Large Animal Medicine and Science, College of Veterinary Medicine, Texas A&M University, College Station, TX. Address reprint requests to Dr. J.P. Watkins, Texas A&M University, College of Veterinary Medicine, Department of Large Animal Medicine and Science, MS 4475, College Station, TX 77843. E-mail: [email protected]. edu
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weight bearing on the injured limb. If these goals are not achieved, the likely outcome is failure of the construct and/or the support limb. There are numerous mechanical limitations to successfully repairing an equine fracture, not the least of which is that most of the available implants are designed for use in humans where fracture forces are substantially less and can be controlled by limiting the amount of weight bearing during the immediate postoperative period. In equine fracture patients, we rely on the implants and repaired bone to share the loads during healing and require that full weight bearing on the injured limb commences as soon as possible following surgery. For best results, fractures must be repaired with adequate purchase in the fracture fragments to allow the bone and implants to share responsibility for transmitting forces through the construct. Certain principles are well defined and should be adhered to: anatomic reduction; double plate fixation (with some exceptions) applying AO (arbeitgemeinshaft für osteosynthesefragen) principles; fixation spanning the maximal length of the bone, filling all screw holes in the plates with screws and placing as many screws as possible across the fracture in lag fashion; and making use of 5.5-mm screws through the end holes of the plate(s) as well as on either side of the fracture. Difficulties arise when a fracture segment is insufficient in length to allow adequate purchase using standard implants. With standard plates we strive for bicortical purchase with a minimum of 7 screws (usually divided between 2 plates) in the major proximal and distal fracture segments. If this is not possible, consideration should be given to using special implant systems designed to increase purchase in the short fracture segment such as the
Long bone fractures dynamic condylar screw plate (DCS), Cobra head, or condylar buttress plates. Comminution adds another dimension of difficulty to the repair. Large fragments, which allow multiple lag screws for interfragmentary compression, and those that can be positioned beneath plates are most easily managed. Small fragments, which cannot be stabilized by multiple lag screws or trapped beneath a plate, as well as fragments located in the cortex subjected to compressive loads, increase the risk of construct failure. Double plate fixation, using a combination of a broad and narrow limited contact dynamic compression plate (LC-DCP), as described previously, has long been considered the standard construct for equine fracture fixation. (Please note that the LC-DCP has replaced the DCP in the United States since 2005). However, high risk repairs require stronger, more fatigue-resistant constructs. Indications for such constructs include: patients whose body weight exceeds 200 kg, especially for fractures above the carpus and tarsus; fractures with significant comminution as described previously; and simple fractures with significant compromise to the soft tissue envelope. Methods to increase the strength and resistance to fatigue failure of the construct include: using 5.5-mm cortex screws throughout the length of one or both plates; using stronger plates, either two broad LC-DCPs or using the stronger DCS or Cobra head plate in place of one of the broad LC-DCPs; luting one or both plates with polymethylmethacrylate (PMMA); and for lower limb fractures, using a cast in conjunction with internal fixation. Large plates, with both plates luted and applied using as many 5.5-mm bone screws as possible, are the strongest, most fatigue-resistant constructs currently available and are strongly advocated for high risk repairs in larger patients. Recently the locking compression plate (LCP) was introduced to human and veterinary surgery.1 This plate, which contains combi holes (Fig. 1), where either a regular cortex screw or a locking screw can be inserted, has a lot of potential in equine fracture repair.2 The locking screws contain threads at the screw head that interlock in the matching threads within the plate hole and result in a solid and very stiff construct. The locking screws must be inserted perpendicular relative to the long axis of the plate. While being completely accepted in human trauma surgery, the new plate is presently gaining popularity among veterinary surgeons. Fracture healing relies on the favorable interaction between the mechanical environment discussed previously and the biologic environment provided by the soft tissues enveloping the fracture. If the biologic environment is substantially compromised, healing is unlikely, even if the mechanical limitations to healing have been minimized. Complete disruption of the neurovascular supply at the fracture site is obviously the most devastating compromise to healing and affected horses should be euthanatized. Fortunately this degree of soft tissue compromise is rare. However, infection is not uncommon and is arguable the most clinically important biologic limitation to fracture healing in the equine patient. Infection is a consequence of bacterial contamination, either from a penetrating injury at the fracture site or acquired during open reduction and internal fixation, and is directly
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Figure 1 Graphic representation of the combi hole, which is found in the locking compression plate (LCP) (Synthes Inc. Westchester, PA). A standard cortex screw can be implanted through the left (nonthreaded) side of the combi hole, which represents one-half of a dynamic compression unit (DCU) hole (below left). A special locking screw with complementary threads manufactured over the screw head threads into the right (threaded) sided of the combi hole (below right). Obviously only one screw can be inserted through one combi hole.
related to the degree of soft tissue injury and the surgery time. Soft tissue injury arises from three sources: the initial trauma, which resulted in the fracture, trauma caused by sharp bone fragments while the fracture is unstable, and trauma resulting from surgical invasion to repair the fracture. Although many long bone fractures can now be successfully repaired, some are outside the domain of feasibility and necessitate humane destruction of the patient. A list of the various factors contributing to a decision for euthanasia is long and varied. Clearly, certain fractures dictate humane destruction of the patient because the mechanical and biological environment requisite for healing cannot be achieved. Unfortunately, there are a number of fractures where fixation and healing are well within the capabilities of current fixation techniques, but other considerations necessitate destroying the patient. These include monetary constraints placed on therapy by the owner as well as the owner’s expectations for future performance once healing has occurred.
Specific Long Bone Fractures Ulna/Olecranon Olecranon fractures are the most common foal long bone fracture repaired in our hospital. These fractures frequently result from the foal falling on the affected limb. It is likely that when the foal falls and the point of the elbow impacts the ground, shear forces initiate the fracture at the caudal aspect of the physis and the forceful contraction of the triceps muscle propagates the fracture cranially. In neonates, the fracture remains confined to the physis (type 1a), but in older foals, the fracture also involves the metaphyseal bone and propagates craniodistally toward the anconeal process (type 1b). The cranial aspect of the fracture may remain nonarticular,
298 but more commonly violates the articular surface in the proximal aspect of the trochlear notch. It is important to note that because the olecranon process is an apophysis and not a true pressure epiphysis, the use of the Salter-Harris scheme for categorizing these fractures is inappropriate. Another common fracture, likely the result of a kick injury to the caudolateral aspect of the olecranon, is a type 2 fracture, where the body of the olecranon distal to the physis is fractured in a transverse manner into the articulation. Foals with these injuries are usually presented as nonweight bearing lame with the limb typically held in flexion. With displaced fractures there is a dropped elbow appearance and there may be moderate to severe swelling in the region of the elbow. Inability to support weight on the affected limb stems from incapacitation of the triceps apparatus and the inability to fix the carpus in extension. Differential diagnoses include fracture of the humerus, radial nerve injury, and scapular neck fractures. The latter two are rare; however, it is imperative to delineate between fractures of the humerus and olecranon, as emergency coaptation in the former is contraindicated (see discussion on humeral fractures). Radiographic examination provides the definitive diagnosis with the most diagnostic view obtained by extending the limb and taking a medial to lateral projection. However, it is important to obtain a craniocaudal view as well, especially with fractures located more distally in the olecranon to ascertain if there is an accompanying injury to the proximal radial physis (see discussion on physeal fractures). Emergency coaptation consists of a well-padded bandage with a rigid splint affixed to the caudal aspect of the limb, extending from the ground to near the point of the elbow. Splinting the carpus in extension allows the foal to bear weight and will minimize further fragment distraction as well as reduce patient fatigue and stress associated with inability to bear weight on the fractured limb during transport and in the preoperative period. In cases of nonarticular nondisplaced fractures, conservative management using elbow to ground splintage and stall confinement can be considered. However, the degree and duration of lameness associated with conservative therapy predispose to complications in both the fractured and support limbs. Attempting to manage a displaced or articular fracture by conservative methods will almost always result in complications and is not recommended. The majority of olecranon fractures are best managed by open reduction and internal fixation (ORIF). The tensile forces of the triceps attachment on the olecranon apophysis result in a reliable biomechanical configuration and fixation using the tension band principle provides a dependable bone implant construct. Surgical fixation restores the weight-bearing function of the limb by reestablishing the triceps mechanism and allows restoration of articular congruency in fractures that enter the humeroulnar joint. The author prefers to use a narrow DCP or LC-DCP applied to the proximal and caudal aspect of the olecranon process (Fig. 2). The bone is approached using a standard caudolateral approach with dissection between the ulnaris lateralis and ulnar head of the deep digital flexor muscles. Fracture reduction is facilitated by grasping the apophysis with pointed reduction forceps and applying caudodistal traction. With the fracture held in reduction an appropriate
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Figure 2 Tension band fixation of type 1b olecranon fracture. A narrow 11-hole DCP has been contoured over the proximal aspect of epiphysis and 2 screws through the plate were placed in lag fashion across the oblique fracture. Note the screws were only placed into the ulna.
length plate is applied to the proximal and caudal aspect of the olecranon process. The proximal aspect of the plate is contoured to curl over the apophyseal fragment to allow purchase with 3 plate screws. Depending on the fracture configuration, one or two plate screws are placed across the fracture in lag fashion engaging the cranial cortex of the metaphysis, with the remainder of the plate screws engaging only the olecranon. Screws in the region of the trochlear notch are monocortical and care is taken with the distal screws to avoid transfixing the radius and ulna. If the radius is inadvertently engaged, incongruence of the humeroulnar articulation will occur, particularly in young foals. In general, the prognosis for healing is excellent with plate fixation, and once healed, most patients are able to function as intended. In a review of our patient population, there were 41 fractures of the olecranon in patients less than 1 year of age.3 Twenty-four fractures (59%) were classified as type 1b. Twenty of the type 1b fractures were repaired as described previously. Sixteen fractures were articular and 10 had some degree of comminution. Nineteen of the 20 patients were discharged from the hospital. One patient was euthanatized postoperatively as a result of a ruptured cecum. Sixteen patients were available for long-term follow-up. Twelve patients were more than 2 years of age at follow-up and 9 were being used as intended in a variety of performance activities with-
Long bone fractures out problems related to the fracture. Four patients were less than 2 years of age and were reported to be free of lameness. Overall, plate fixation was deemed successful in 16 of 20 patients, with an excellent outcome in 13. In contrast, a report detailing conservative management of type 1b fractures listed only 6 of 18 patients with a successful outcome, clearly demonstrating the superiority of ORIF in managing this injury.4 Similar results have been reported with plate fixation of type 2 fractures. Although less common in our patient population, type 2 fractures have been the subject of a number of reports.5,6 Overall, 17 of 20 type 2 fractures treated by plate fixation had successful outcomes compared with only 1 of 6 managed conservatively. Pins and wires have also been used successfully. The author has limited experience with this fixation method, but in one report, 4 foals with type 1a fractures and 3 of 4 foals with type 1b fractures were treated successfully.7 Potential advantages of pin and wire fixation include less dissection of the triceps insertion on the olecranon apophysis and reduced likelihood of secondary fracture of the apophysis. In addition, penetration of the articulation by implants and radioulnar transfixation are not likely. However, in vitro mechanical studies have shown the strength and fatigue life of the fixation to be significantly lower than plate fixation. It is the author’s opinion that pin and wire fixation should be reserved for use in neonates with markedly displaced, nonarticular apophyseal fractures in which there is an increased potential for secondary apophyseal failure and the small size of the patients reduces the likelihood of implant failure.
Humerus In our hospital the humerus is the second most common foal long bone fracture encountered. In neonates a direct blow from a kick is the common cause of injury. More commonly, the affected foal is older and has a history of falling on the affected limb. The resultant short oblique or spiral fracture configuration likely occurs when the fall occurs with the limb in adduction. Clinical signs are similar to an olecranon fracture, that is, dropped elbow stance with the limb held in flexion. Swelling is more consistent with humeral fractures and is best viewed from the cranial aspect where thickening of the brachial region is very apparent. A medial to lateral radiograph taken with slight cranial to caudal obliquity best defines the fracture. In addition, a caudal to cranial view with the radiographic beam directed slightly from proximolateral to distomedial further delineates the fracture configuration and relative position of the fragments. First aid measures aimed at stabilizing the fracture and minimizing secondary soft tissue and bone trauma are not possible. It should be noted that splinting the distal limb in extension, as described for olecranon fractures, will allow limited weight bearing on the affected limb, but in the author’s opinion is contraindicated. Encouraging the foal to use the affected limb will result in further damage to the soft tissues, primarily the brachialis muscle and radial nerve, by the sharp fracture fragments. Additionally the splinting adds weight to the limb distal to the fracture and induces increased leverage forces, causing further trauma in the fracture region.
299 Alternatives for definitive therapy include stall confinement, plate fixation using a cranial approach, stacked pin fixation, and interlocking nail fixation. Fractures most suited for conservative management are minimally displaced, long oblique fractures in which overriding imparts some degree of stability to the fracture. Fracture healing with conservative management of up to 50% has been reported.8 Complications include mal-union, ipsilateral flexural deformity, especially in the carpal region, and contralateral varus deformity and fetlock hyperextension secondary to the prolonged convalescence. Short oblique and spiral fractures of the mid to distal humerus are typically displaced, markedly overriding, and very unstable and are not good candidates for conservative therapy. Stacked pin fixation, where multiple 1/4 inch and 1/16 inch Steinmann pins are used to fill the medullary canal, has been successful in some instances. Limitations with this form of fixation include poor rotational stability and the tendency for pin loosening and migration. Cranial plating is an alternative, and if needed a second plate can be applied laterally.9 Limitations to plate application include the complex surface anatomy of the humerus and the closely applied soft tissue investment, including the brachialis muscle and radial nerve in the musculospiral groove. Implant loosening with subsequent instability is also a major concern. The majority of the author’s experience has been with interlocking nail fixation using a custom designed implant system. Selecting a modified lateral approach, the fracture is reduced following reaming of the medullary canal of the proximal and distal fracture segments. The nail is placed in the medullary canal and the proximal and distal fracture segments are transfixed to the intramedullary nail by positioning 5.5-mm cortex bone screws through preplaced holes in the nail (Fig. 3). Biomechanically this form of fixation is capable of preventing collapse at the fracture site and neutralizing bending and rotational forces. Furthermore, implant migration is prevented. As with all forms of fixation, the location and configuration of the fracture significantly affects the strength and stability of the construct. Ideally, three interlocking screws are positioned on either side of the fracture. In large foals or when the fracture configuration does not allow adequate screw fixation in either the proximal or distal fracture segments, a bone plate is applied to the cranial surface of the humerus to augment the fixation. Results with interlocking nail fixation of humeral fractures in foals at our institution have been encouraging. In our initial report of 10 foals with humeral fractures, 50% of the foals treated—some weighing as much as 220 kg— healed their fractures.10 Foals that healed their fractures attained athletic soundness and fulfilled their intended purpose without complications related to the fractured humerus. Further experience with this technique in a substantial number of additional cases has produced better results.
Femur Diaphyseal fractures of the femur in foals usually result from the foal falling with the affected limb in adduction. In neonates a direct blow from a kick is a more common cause of injury. Clinical signs are highly indicative of a diaphyseal
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J.P. Watkins minimizing secondary soft tissue and bone trauma are not possible. Instability at the fracture and the risk of further soft tissue trauma and hemorrhage are indications for surgical intervention as soon as feasible. The fracture is confirmed by radiographic evaluation, which in some instances can be accomplished on survey films with the patient standing. If surgical intervention is considered, it is advisable to get detailed films once the foal is anesthetized. A medial to lateral and cranial to caudal view with slight lateral to medial obliquity are advised. Most diaphyseal fractures have a spiral or oblique configuration and are often accompanied by some degree of comminution. Comminution of the caudal cortex is of particular concern, as it will negatively affect the prognosis. Neonates often have a mid-diaphyseal transverse configuration when the fracture has resulted from a kick injury. Currently, double plate fixation is considered by most sur-
Figure 3 Intramedullary, interlocking nail fixation of a mid-body humeral fracture in a foal. Each fracture segment has been transfixed to the intramedullary nail by three 5.5-mm cortex screws. No countersinking was conducted but screws inserted through washers increasing contact surface without weakening the bone. Targeting was accomplished using a custom designed targeting device. The radiodense chips are antibiotic impregnated PMMA beads, which were placed along the bone.
fracture and include non-weight-bearing lameness accompanied by substantial soft tissue swelling. Medullary bleeding and damage to the femoral or popliteal artery often result in a massive hematoma and can be life-threatening. Although obvious from a lateral perspective, the swelling is most appreciated when viewed from behind the foal, where the thickness of the thigh region is often twice that of the unaffected limb. First aid measures aimed at stabilizing the fracture and
Figure 4 Double plate fixation of a femur fracture in a foal. One plate was applied to the cranial, the other to the lateral aspect of the bone without involving the physis.
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geons as the technique of choice for definitive management of these injuries.11 A standard lateral approach with dissection between the biceps femoris and vastus lateralis muscles is used to expose the femoral shaft. Reconstruction of the bony column, with emphasis on achieving abutment at the caudal cortex, is important to success. Once the fracture is reduced, a broad DCP or LC-DCP is applied to the lateral aspect of the femur. A second plate is applied cranially to increase the strength and stability of the fixation (Fig. 4). In large foals or foals with complex fractures, it is advisable to use a DCS plate laterally and a broad plate cranially. Using 5.5-mm screws and luting one or both plates will maximize strength and stability of the construct. Success in the range of 50% can be expected with careful case selection in foals weighing less than 250 kg. Postoperative infection is the most significant contributor to failure and appears to be predisposed to by seroma formation. Closed suction drainage in the immediate postoperative period can be used if deemed necessary, to evacuate the seroma. The author has successfully used interlocking nail fixation for femur fractures in foals. In neonates with simple transverse, mid-diaphyseal fractures, interlocking nail fixation, with 3 screws transfixing the nail to the proximal and distal fracture segments, has been used with good results (Fig. 5). In older foals, interlocking nail fixation augmented by a cranial plate has also been successful. Although in vitro testing using a femoral ostectomy model revealed double plate fixation to provide greater strength and stiffness, it has been the author’s experience in a limited number of clinical cases, that nail/plate fixation offers at least equal, if not better, success rates when compared with published results of double plate fixation.
Radius Radial fractures in foals are most commonly encountered in the diaphysis of the bone and often result from a kick injury. Blows to the cranial aspect of the radius result in a middiaphyseal, transverse fracture, whereas a kick to the lateral radius will cause an oblique fracture near the junction of the proximal and middle one-thirds of the diaphysis. Clinically affected foals are presented with a flail limb that tends to displace in a valgus manner at the fracture site during attempts of applying weight on the limb. Soft tissue swelling is usually significant and may be accompanied by a wound in the medial antebrachial region. It is in this location that fracture fragments are likely to penetrate the skin because of the limited soft tissue cover and tendency for the sharp fracture fragments to displace into this area when the distal limb deviates laterally. Immediate first aid measures include appropriate wound therapy and broad-spectrum antibiotic administration for open fractures and external coaptation to provide stability to the fracture and protect the bone and soft tissues from further trauma. A full limb, modified RobertJones bandage, applied in successive well-compressed layers, is recommended. A caudal splint extending from the level of the hoof to the olecranon process, in conjunction with a lateral splint extending from the hoof beyond the proximal end of the bandage and over the lateral aspect of the shoulder region, will provide stability and prevent abduction of the distal limb, thereby minimizing medial displacement of the
Figure 5 Intramedullary, interlocking nail fixation of a femoral fracture in a foal. The distal aspect crosses the physis perpendicularly to its orientation and penetrates the epiphysis. No detrimental effect was discovered.
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Figure 6 Postoperative radiographic views of a double plate fixation of a radius fracture in a foal. The cranial plate covers the entire bone and the plates were applied perpendicular relative to each other. PMMA beads were applied to prevent infection.
fracture fragments. In small foals the splints can be affixed to the bandage using inelastic tape. In larger foals, two rolls of fiberglass cast material work well in place of tape. Plate fixation is the best method for managing radial fractures. A craniolateral approach to the radius, with dissection between the extensor carpi radialis and common digital extensor muscles, allows plate application on either the cranial or lateral aspect of the bone. A medial approach to the radius is used only in exceptional circumstances. The lack of overlying musculature medially and the tendency for more extensive damage to the soft tissues overlying the fracture in this area make a medial approach less desirable in the author’s opinion. Transverse fractures of the mid-diaphysis in small foals can be managed with a single broad DCP or LC-DCP applied to the cranial aspect of the radius. With anatomic reconstruction, the plate is loaded in tension because of the strong cranial curvature of the radius. Double plate fixation is recommended for all other diaphyseal fractures including proximal oblique fractures where the number of screws in the smaller proximal fragment should be maximized (Fig. 6). In small foals, a cranial broad plate and lateral narrow plate may suffice. As the size of the patient increases or with more complex fracture configurations, two broad plates are recommended. Using 5.5-mm screws and luting one or both plates will maximize strength and stability of the construct. Anatomic reconstruction of the fracture, with particular attention given to the caudal cortex, is a prerequisite for successful fixation.
Displaced radial fractures in foals, particularly if comminution is not present and the fracture is closed, have a relatively good prognosis for fracture healing with the majority of healed patients achieving athletic function.12 In one case series 7 of 7 foals with mid-diaphyseal transverse fractures had successful outcomes following single plate fixation.12 In the same report, 4 of 7 foals with proximal oblique fractures healed their fracture, with 3 able to perform athletically following double plate fixation. Success for double plate fixation with comminuted fractures was achieved in 2 of 3 foals.
Tibia Diaphyseal fractures of the tibia in foals are not common in our practice. However, those presented are usually oblique or spiral fractures of the mid to distal tibial shaft and result primarily from a kick injury. Clinically affected foals are presented with a flail limb that tends to displace in a valgus manner at the fracture when the limb is loaded. Soft tissue swelling is usually significant and may be accompanied by a wound at the medial aspect of the gaskin. It is in this location that fracture fragments are likely to penetrate the skin because of the limited soft tissue cover and tendency for the sharp fracture fragments to displace into this area when the distal limb deviates laterally. Immediate first aid measures are identical to the ones described for the radius. A lateral splint extending from the hoof beyond the proximal end of the bandage and over the lateral aspect of the hip region will provide stability and prevent abduction
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303 proach to the tibia because of the lack of overlying musculature and the tendency for more extensive damage to the soft tissues medially. A broad plate is appropriately contoured and applied to extend from the cranial distal end of the tibia to the craniomedial aspect of the proximal tibia. The second plate is then applied to the lateral aspect. Long spiral fractures, which allow many of the screws to be placed in lag fashion through the plate and across the fracture line, are ideal candidates for fixation. In small foals, a cranial broad plate and lateral narrow plate may suffice. As the size of the patient increases or with more complex fracture configurations, two broad plates are recommended. Using 5.5-mm screws and luting one or both plates will maximize strength and stability of the construct. Long oblique and spiral fractures of the tibial diaphysis, which are closed, have a relatively good prognosis for fracture healing, with the majority of healed patients achieving athletic function.13 Fractures with comminution and short oblique fractures have been reported to be associated with more postoperative complications.
Third Metacarpal/Metatarsal Bone
Figure 7 Double plate fixation of a tibia fracture in a foal. Note the axially twisted cranial plate needed for good bone-plate contact along its entire length.
of the distal limb, thereby minimizing medial displacement of the fracture fragments. In small foals the splint can be affixed to the bandage using inelastic tape. In larger foals, two rolls of fiberglass cast material work well in place of tape. When adequate bone stock exists both proximal and distal to the fracture, double plate fixation can be used to successfully stabilize the fracture (Fig. 7). A craniolateral approach to the tibia, in which the skin and deep fascial incisions overly the cranial tibial muscle followed by dissection medially to the bone, is favored. The author rarely uses a medial ap-
Diaphyseal third metacarpal/metatarsal (McIII/MtIII) fractures in foals are often the result of a direct blow but also occur from a misstep during vigorous activity. Because of the limited soft tissue envelope in this area, open fractures are common, frequently the result of the sharp fracture fragments penetrating the skin. Diagnosis is usually straightforward: non-eight-bearing lameness accompanied by obvious instability. Immediate efforts must be made to provide emergency coaptation to protect the soft tissues and bone from further damage. In the forelimb, a full limb, modified Robert Jones bandage with rigid splints applied to the caudal and lateral aspects and extending the length of the bandage should be applied. In the hind limb, the bandage and splints should extend from the hoof to the tuber calcis. Dorsopalmar (plantar), lateral to medial, and both oblique views are taken to radiographically characterize the fracture. A major limitation in managing fractures of McIII/MtIII is the lack of overlying musculature and the limited amount of soft tissues available for coverage of space occupying implants and to provide an extraosseous blood supply to support healing. Soft tissue damage and the relatively poor blood supply to the area predispose to infection, particularly if the fracture was open. If infection does occur there appears to be an increased risk of nonunion because of osteomyelitis and the development of large areas of devascularized bone (Fig. 8). Options for managing McIII/MtIII fractures include ORIF using bone plates, external coaptation with either a standard or transfixation cast, or a combination of internal fixation and external coaptation. The method of choice is determined by the mechanical and biological attributes of the injury. In general, plate fixation is preferred, as it provides the most stability to the fracture, thereby promoting an early return to unprotected weight bearing on the fractured limb. However, highly comminuted and open fractures may be better managed by alternative methods.
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J.P. Watkins indicated. McIII is loaded axially, allowing placement of plates on either the dorsal, lateral, or medial surfaces. The dorsolateral cortex of MtIII is loaded in tension and one of the plates should be applied to that surface when possible. In small foals with simple fractures, a broad and narrow plate are adequate. In larger foals or with more complex fractures, two broad plates are advocated. Open fractures and those with substantial comminution are poor candidates for open reduction and plate fixation. The risk of further compromising vascularity to the fracture fragments and promoting infection are too great in these circumstances. If plate fixation is elected it should be performed using minimally invasive techniques and the use of an LCP should be considered. Alternatively, a cast or transfixation cast can be used. Closed fractures managed by double plate fixation have a good prognosis for healing.14,15 Unfortunately, the limb is often noticeably thickened and owners should be made aware that the cosmetic appearance will be impaired. Fractures complicated by infection are much less likely to have a favorable outcome.
Figure 8 Infected fracture construct following single plate fixation of a metacarpal fracture in a foal. Note the large devascularized area in the mid-diaphysis.
Double plate fixation is the method of choice for managing closed diaphyseal fractures, which are not highly comminuted (Fig. 9). A major concern is the ability to reconstruct the soft tissues over the implants; therefore, a transtendinous approach along the common/long digital extensor tendon is
Figure 9 Double plate fixation of a metacarpal fracture in a foal. The plates span the entire bone down to the physis and are applied perpendicular relative to each other. All plate holes were filled with screws.
Long bone fractures
Physeal Fractures Physeal fractures may affect either traction or pressure epiphyses. Traction epiphyses serve as sites of attachment for tendons or ligaments and are subjected primarily to tensile forces. Compression is the major force affecting pressure epiphyses that comprise the articular ends of long bones. The most common traction epiphyseal injury affects the physis of the olecranon process as previously discussed. Injuries to physes associated with pressure epiphyses in the foal occur throughout the appendicular skeleton and account for roughly 20% of foal long bone fractures.16 These fractures result primarily from shear and bending forces concentrated at or near the affected physis and epiphysis. Type I injuries are confined to the physis. Type II injuries traverse along the physis and exit the physis into the metaphysis. Type III and IV injuries involve the epiphysis and adjacent articulation. Type III injuries involve only the epiphysis and physis while type IV injuries cross into the metaphysis. Type V injuries are actually compression fractures of the physis and bone immediately adjacent to the physis. The Salter-Harris classification scheme described above should be reserved to describe only fractures associated with pressure epiphyses. The scheme describes the relationship of the fracture relative to the epiphysis, physis, and metaphysis. In children, as the assigned number increases, the likelihood of a growth disturbance increases and therefore the prognosis decreases. However, in foals the most important aspect of prognosis is potential to restore the weight-bearing function of the limb and therefore the foal’s life. Foals with type I and II injuries, the most common physeal fractures, usually present with non-weight-bearing lameness. Mal-alignment of the bony column and soft tissue swelling are usually evident, dependent on the location of the injury. Manipulation of the limb usually demonstrates instability at the fracture site and induces a painful response. In most cases there is adequate displacement at the fracture site to delineate the type and severity of the fracture with routine radiographic projections. However, if displacement is minimal, particularly with type I injuries, stress radiographs may be necessary to definitively diagnose the fracture. It may also be helpful to take radiographs of the contralateral physis for comparison. Type III and IV injuries are rare, but will present with significant lameness accompanied by effusion in the affected joint. Gross mal-alignment and instability of the limb may or may not be evident with these injuries. With displacement and instability, the injury may appear as a luxation. Radiographs readily define the injury. Type V injuries are rare as well, but are presented with a primary complaint of progressive angular limb deformity. Lameness may not be evident at the time of examination. Radiographs may fail to delineate the injury until transphyseal callus has formed and evidence of partial or complete premature closure of the physis or peripheral bone bridge formation is evident. Differential diagnoses of pain localized to the physis accompanied by swelling and lameness should include septic physitis, direct trauma to the physis, and occasionally severe physeal dysplasia. History, physical and radiographic examination, and in septic physitis, needle aspiration will aid in arriving at the proper diagnosis. When the above clinical signs are accompanied by instability and joint effusion, luxation should be considered.
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Management Management guidelines for physeal fractures in foals are based on the classification of the injury. For type I and II injuries the major emphasis is to reestablish the bony column, usually by ORIF using either screws, wires, pins, or plates. With type III and IV fractures the objective is to realign the articular surface. In these instances lag screws placed parallel to the physis across the fracture lines in the epiphysis and metaphysis may be adequate. Preventing the development of a significant angular deformity is the goal when managing type V injuries. In these cases growth plate retardation on the side of the physis opposite to the transphyseal bone bridge is indicated. If the deformity is noted near the end of prospective growth for the physis then a corrective osteotomy may be necessary if the deformity is severe. The most significant factor reported to influence the prognosis for life following a physeal fracture is the age of the foal.17 Significantly better results were obtained in foals less than 4.5 months of age at the time of injury. In these cases 25% of the foals were sound following treatment, with an additional 25% salvaged for breeding purposes. For the specific fractures discussed below, too few cases have been reported to provide a reasonable prognosis.
Specific Physeal Fractures Femur Fractures affecting the capital femoral physis are usually type I injuries. They usually result from a fall and direct impact on the proximal femoral area. Although affected foals are severely lame immediately after the injury, there is often a significant time interval between injury and presentation because of the lack of obvious instability and swelling. This delay promotes eburnation of the physeal cartilage along the fracture and muscle contracture, both of which markedly complicate surgical management. Care must be taken during the radiographic examination to ensure that the full extent of the injury is delineated. Frequently there will be accompanying fractures of the femoral head and neck or acetabulum.18 In some cases there is an associated coxofemoral luxation. Cases with isolated physeal injury are reasonable candidates for ORIF. Numerous techniques have been described, including stacked pin fixation, dynamic hip screw (DHS) fixation, and lag screw fixation. Lag screw fixation using multiple large screws, either 6.5-mm cancellous or 7.0- or 7.3-mm cannulated screws is recommended. Exposure is achieved via a trochanteric osteotomy and screws are directed from the proximal femoral metaphysis into the femoral head. The procedure is technically demanding and anatomic alignment is difficult to achieve because of muscle contracture and eburnation of the fracture fragments. Most distal femoral physeal fractures are type II injuries. Non-weight-bearing lameness accompanied by substantial swelling in the distal femoral and stifle regions is typical. Radiographs delineate the fracture, most of which have a cranial metaphyseal fragment. The femoral diaphysis overrides caudally and distally. ORIF using plate fixation is advised but difficult in most cases. The degree of overriding and strength of the musculature in the area make reduction particularly challenging. Furthermore, inability to gain substantial purchase in the epiphyseal segment makes it difficult to provide a fracture construct with adequate strength and sta-
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Figure 10 (A) Distal femoral type 2 physeal fracture in a foal. (B) The fracture was repaired using a DCS plate laterally and two narrow DCPs applied cranially, with their most distal screws directed into the femoral condyles.
bility. Plate fixation, using a laterally positioned DCS plate, in conjunction with one or two cranial plates with screws directed across the physis and into the medial and lateral condyles can be successful, but is technically challenging (Fig. 10). Tibia Most physeal fractures of the tibia affect the proximal physis and are of the type II configuration. They usually result from a blow to the lateral aspect of the limb, or in some cases, when a recumbent foal’s limb becomes entrapped and the foal attempts to stand. These injuries are characterized by a lateral metaphyseal fragment and lateral displacement of the distal tibia. Neonates and foals weighing between 100 and 200 kg are most commonly presented to our hospital. Numerous small case series have described a variety of management techniques including: application of a Charnley apparatus, plate fixation,19 lag screw fixation,20 and cross pin fixation.21 The author prefers to manage neonates with a transphyseal bridge using screws and either wires or a cable across the medial aspect of the physis. Once the epiphyseal and metaphyseal screws are in place, a figure-8 wire is applied and tightened, bringing the fracture into alignment. It is advisable to place a second transphyseal bridge to supplement the fixation. In larger foals, we use a narrow DCP or LC-DCP applied medially, with a 6.5-mm cancellous or 5.5-mm cortex screw in the epiphysis (Fig. 11). If possible one or two plate screws distal to the physis are placed into the lateral metaphyseal
fragment, in lag fashion. It is useful to first position a transphyseal bridge with screws and wire (or cable) to achieve fracture reduction, then position the plate. The screws and wire (cable) can either be left in place to supplement the plate fixation, or when deemed necessary, can be replaced by a second narrow DCP or LC-DCP to further augment the strength of the fixation. Radius Most physeal fractures of the radius affect the proximal physis and are associated with a fracture of the ulna at the level of the radial physis. Types I and II injuries are most common and the degree and direction of displacement are variable. It should be noted that if the distal radial fracture segment is displaced cranially, the radial nerve may be injured and result in low radial paresis during the convalescent period (Fig. 12). Nondisplaced fractures can heal with conservative therapy; however, the degree of discomfort and potential for displacement often warrant internal fixation. Displaced fractures require open reduction and plate fixation. In general, a caudal plate is applied to the ulna with the distal plate screws engaging the proximal radius and the plate extending proximally to the olecranon. A second plate is positioned laterally with fixation in the radial epiphysis and proximal metaphysis (Fig. 13). In small foals, a transphyseal bridge using screws and wires may be used in place of the lateral plate. The lateral transphyseal bridge or plate will increase the strength and stability of the fixation. In addition, it helps ensure that transfixation of the olecranon and radius by the caudal plate
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Figure 11 (A) Craniocaudal radiographic view of a proximal tibial type 2 physeal facture. (B) Postoperative lateromedial radiographic view of the repaired fracture. One broad 7-hole—and a narrow 9-hole DCP was applied with the proximal most screw of each plate engaging the epiphysis. Additionally a fixation consisting of one epiphyseal and one metaphyseal screw connected with two figure-8 cerclage wires was applied. (C) A craniocaudal follow-up radiographic view shows good healing.
will not cause elbow incongruence by preventing growth at the proximal radial physis.
avoid cast coaptation, a bone plate may be applied as a bridge to the physis opposite the metaphyseal fragment.
Distal McIII/MtIII Physeal fractures of the distal McIII/MtIII are rarely encountered, but appear to occur most frequently in draft foals. They are nearly always a type II injury and occur secondary to the foal being stepped on. These injuries are readily managed in most cases by lag screw fixation of the metaphyseal fragment to the parent bone combined with external stabilization in a short limb cast. In large foals, or if the surgeon wishes to
Proximal Phalanx Rarely fractures of the proximal physis of the proximal phalanx are encountered. Because of the limited amount of longitudinal bone growth, transphyseal bridging techniques using screws and plates can be applied. In minimally displaced type I fractures conservative management with cast application is a valid option.
Complications
Figure 12 Type 2 physeal fracture of the proximal radius with cranial displacement of the distal fragment. The foal was successfully repaired, however suffered from low radial nerve paresis (mild inability to extend the digit) for approximately 2 months following surgery.
Complications associated with fracture management in foals include problems related to the fracture construct and axial deformities. Problems affecting the fracture construct include infection and fixation failure. Infection is directly correlated to the degree of damage to the soft tissues enveloping the fracture. Every effort must be made during the initial assessment phase of management to provide temporary stabilization of the fracture fragments and minimize further injury before definitive therapy. In addition, appropriate antiinfective measures must be taken when the skin overlying the fracture is compromised. Perioperative broad-spectrum antimicrobials and careful monitoring during the postoperative phase of therapy are essential aspects of the prevention and early identification of infection. If infection occurs, early aggressive therapy aimed at preventing accumulation of exudate and definitively identifying offending organisms and their antimicrobial susceptibilities are important. Systemic and local antimicrobial therapy in conjunction with maintenance of fracture stability are prerequisites for success. If instability accompanies infection or a significant portion of the fracture becomes avascular, the fixation is doomed to failure. Construct failure is usually the result of inadequate fixation. In some instances, particularly in very young foals, the quality of bone purchased by the implants predisposes to failure, especially true of the olecranon apophysis in neonates. If bone quality is suspect, implants designed for fixation in osteopenic bone,
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support limb at the time of fracture fixation that provides both lateral and palmar/plantar extension of the solar surface of the hoof. When the physis suffers direct injury, transphyseal bone formation may result in shortening or angular deformity of the affected bone. In most instances of physeal fracture, shortening of the bone as a result of cessation of growth at the fractured physis is an expected consequence. The end result is often not clinically apparent because adjacent joints can increase their degree of extension and maintain overall limb length. Although uncommon, if an angular deformity develops as a result of a peripheral physeal injury, management is directed at retarding physeal growth on the unaffected side of the physis to minimize progression of the deformity.
References
Figure 13 (A) Radiographic views of a type 2 physeal fracture of the proximal radius combined with a multifragment fracture of the ulna in a foal. (B) The fractures were repaired by means of two plates. The caudal 12-hole narrow DCP uses the olecranon to provide plate purchase proximal to the fracture and the remaining distal screws engage the radius distal to the fracture. The fifth screw from the top penetrates the proximal epiphysis of the radius, while the next two screws distally were implanted in lag fashion across the main fracture line. The lateral 6-hole narrow DCP has a single 5.5-mm cortex screw in the proximal radial physis, with the next 2 screws engaging the metaphyseal fragment. On the lateral view several broken screws are seen in the radius. PMMA beads are applied around the repaired fracture.
such as the LCP system, or alternative fixation methods should be used in place of standard plate fixation techniques. Axial deformities result from tendinous disorders or physeal growth disturbances. They usually are secondary and result from prolonged lameness associated with the injury, with the exception of physeal fractures where the growth cartilage of the physis is damaged primarily. Prolonged lameness predisposes the support limb to fetlock hyperextension and varus angular deformity. Flexor contracture may occur in the fractured limb. Preventing these complications is primarily dependent on providing a stable fracture construct, which encourages full weight bearing on the affected limb as soon after surgery as possible. In addition, glue on hoof plates can be a useful adjunct. The author routinely places a hoof plate on the
1. Frigg R: Locking compression plate (LCP): an osteosynthesis plate based on the dynamic compression plate and the point contact fixator (PC-Fix). Injury 32:B63-66, 2001 2. Florin M, Arzdorf M, Linke B, et al: Assessment of stiffness and strength of four different implants available for equine fracture treatment: a study on a 20 degree oblique long bone fracture model using a bone substitute. Vet Surg 34:231-238, 2005 3. Swor TM, Watkins JP, Bahr A, et al: Results of plate fixation of type 1b olecranon fractures in 24 horses. Equine Vet J 35:670-675, 2003 4. Wilson DG, Riedesel E: Nonsurgical management of ulnar fractures in the horse: a retrospective study of 43 cases. Vet Surg 14:283-286, 1985 5. Donecker JM, Bramlage LR, Gabel AA: Retrospective analysis of 20 fracture of the olecranon process of the equine ulna. J Am Vet Med Assoc 185:183-189, 1984 6. Denny HR: The surgical treatment of fracture of the olecranon in the horse. Equine Vet J 19:319-325, 1987 7. Martin F, Richardson DW, Nunamaker DM, et al: Use of tension band wires in horses with fractures of the ulna. 22 cases (1980-1992). J Am Vet Med Assoc 207:1085-1089, 1995 8. Carter BG, Schneider RK, Hardy J, et al: Assessment and treatment of equine humeral fracture: retrospective study of 54 cases (1972-1990). Equine Vet J 25:203-207, 1993 9. Rakestraw PC, Nixon AJ, Kaderly RE, et al: Cranial approach to the humerus for repair of fractures in horses and cattle. Vet Surg 20:1-8, 1991 10. Watkins JP: Intramedullary, interlocking nail fixation of humeral fractures: results in ten foals (1989-1995). Proc Am Assoc Equine Pract 42:172-173, 1996. 11. Hance SR, Bramlage LR, Schneider RK, et al: Retrospective study of 38 cases of femur fractures in horses less than one year of age. Equine Vet J 24:357-363, 1992 12. Sanders-Shamis M, Bramlage LR, Gable AA: Radius fractures in the horses: 47 cases. Equine Vet J 18:432-437, 1986 13. Young DR, Richardson DW, Nunamaker DM, et al: Use of dynamic compression plates for treatment of tibial diaphyseal factures in foals: 9 cases. J Am Vet Med Assoc 194:1755-1760, 1989 14. McClure SR, Watkins JP, Glickman NW, et al: Complete fractures of the third metacarpal or metatarsal bone in horses: 25 cases (19801996). J Am Vet Med Assoc 213:847-850, 1998 15. Beinlich CP, Bramlage LR: Results of plate fixation of third metacarpal and metatarsal diaphyseal fractures. Proc Am Assoc Equine Pract 48: 247-248, 2002 16. Embertson RM, Bramlage LR, Herring DS, et al: Physeal fractures in the horse I: classification and incidence. Vet Surg 15:223-229, 1986 17. Embertson RM, Bramlage LR, Herring DS, et al: Physeal fractures in the horse II: management and outcome. Vet Surg 15:230-236, 1986 18. Hunt DA, Snyder JR, Morgan JP, et al: Femoral capital physeal fractures in 25 foals. Vet Surg 19:41-49, 1990 19. White NA, Blackwell RB, Hoffman PE: Use of a bone plate for repair of proximal physeal fractures of the tibia in two foals. J Am Vet Med Assoc 181:252-254, 1982 20. Wagner PC, DeBowes RM, Grant BD, et al: Cancellous bone screws for repair of proximal growth plate fractures of the tibia in foals. J Am Vet Med Assoc 184:688-691, 1984 21. Watkins JP, Auer JA, Taylor TS: Crosspin fixation of fractures of the proximal tibia in three foals. Vet Surg 14:153-159, 1985