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Tibia and fibula
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Tibia and fibula
K. Voss, S.J. Langley-Hobbs, P.M. Montavon
Fractures of the tibia and/or fibula are common, accounting for about 10–20% of fractures in cats (1, 2). Usually both the tibia and fibula are fractured. The fractures are often caused by falls from a height, but may occur after any type of trauma (3–5). Most of the fractures of the feline tibia involve the middle and distal diaphysis (2–4). The diaphysis of the tibia is surrounded by minimal soft tissue, and many tibial fractures are comminuted and/or open. The incidence of open fractures of the tibial diaphysis has been reported to be as high as 21–46% (3, 4). Cats with high-rise syndrome sustain open fractures more commonly than cats with other causes of trauma (4). The high incidence of comminuted and open fractures, and the limited extraosseous blood supply and soft-tissue envelope, is likely to account for the higher rate of complications, such as delayed union, non-union, and osteomyelitis, when compared to fractures of other bones.
39.1 Surgical anatomy The tibia is a straight bone with a triangular shape in the proximal third and a round to oval shape in the distal twothirds. The fibula is very thin in cats and does not contribute to weight-bearing, but it is important for stifle and tarsal joint stability because it serves as the attachment site for the lateral collateral ligaments of both joints. The distal fibula has a ligamentous connection to the tibia, the inferior tibiofibular ligament. This ligament is important for stability of the tarsal joint, because the medial and lateral malleolus are not only the sites of origin of the tarsal collateral ligaments but also serve as a medial and lateral restraint for the trochlea of the talus (Chapter 40).
39.2 Stabilization techniques Many stabilization methods can be used to treat tibial fractures. The reader is referred to Chapters 13 and 24 to review the factors influencing the choice of treatment and implants for different fracture types. External coaptation with a cast is successful for stabilization of certain tibial fractures in young cats, such as greenstick, simple transverse fractures, and tibial fractures with an intact fibula. Indications and application techniques for external coaptation are described in Chapter 22. The tibia is the ideal bone for closed reduction and external skeletal fixation, because it is surrounded by
minimal soft tissue. This technique is most useful for comminuted and open fractures. Fracture types occurring in the proximal tibia, the diaphysis, and the distal bone, and possible options for treating them are summarized in Table 39-1.
39.2.1 Intramedullary pinning Although the straight form of the tibia is ideal for inserting intramedullary pins, they are not used as commonly in the tibia, as compared to the humerus and femur. Intramedullary pins should always be inserted in a normograde fashion into the tibia because retrograde pinning in cats invariably results in penetration of the patellar tendon (6). Intramedullary pins must be used in conjunction with implants resistant to rotation and axial compression, dependent on the fracture type. The size of the pin is selected according to the smallest diameter of the distal medullary cavity. If the pin is combined with a plate or an external fixator, the size selected should be around 30% of the diameter of the distal medullary canal to leave room for insertion of the screws or pins. Selecting too large a pin and then trying to pass pins or screws past the pin can result in cortical fissures. Kirschner wires of a diameter of 1.2–2.0 mm are usually adequate. A medial parapatellar approach to the stifle is performed for normograde intramedullary pin insertion. The pin entry point is located on the medial aspect of the tibial plateau, between the insertion of the patellar tendon and medial collateral ligament, cranial to the intermeniscal ligament (Fig. 39-1). Holding the stifle joint in 90° of flexion facilitates insertion of the pin. The pin is then advanced along the medial cortex using a Jacobs chuck until its tip is located close to the fracture. The fracture is reduced, and the pin is further advanced until resistance is felt at the distal epiphysis. The distal tibial epiphysis is a short piece of bone, so great care must be taken not to push the pin into the tibiotarsal joint. The proximal end of the pin is cut as short as possible to avoid irritation of the patellar tendon and parapatellar tissue.
39.2.2 Interlocking nailing The use of an interlocking nail for stabilization of feline tibial fractures has been described as part of a large
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Fracture localization
Fracture type
Stabilization methods
Proximal tibia
Salter and Harris type II
Parallel or cross pinning IM pin and antirotational K wire Lag screw and antirotational K wire External coaptation IM pin and: – ESF – plate – internal fixator Plate and tension band Internal fixator and tension band IM pin and: – ESF – plate – internal fixator IM pin and ESF Compression plate Internal fixator External coaptation Lag screw and neutralization plate Lag screw and internal fixator IM pin and ESF IM pin and cerclage wire ESF (closed reduction) ESF ± IM pin Buttress plate Internal fixator Interlocking nail ESF and IM pin Plate ± IM pin Internal fixator ± IM pin IM pin and: – ESF – plate – internal fixator Cross pinning
Simple metaphyseal
Comminuted metaphyseal
Diaphysis
Simple transverse or short oblique
Simple long oblique and reducible multifragmentary Comminuted
Distal tibia
Simple metaphyseal
Comminuted metaphyseal
Salter and Harris type I
Table 39-1. A summary of feline tibial fractures and selected treatment options
IM pin, intramedullary pin; ESF, external skeletal fixator.
retrospective study involving nail use in dogs and cats (7). The interlocking nail was applied infrequently in the tibia in the cat, when compared to other long bones, but from the information obtained from the study no complications occurred with its use. With the current range of interlocking nail sizes, the nail can only be used in large cats with fractures involving the mid to proximal third of the tibial diaphysis. The 4.0-mm nail with 2.0-mm screws or bolts is the most appropriate size to use, and the length of the nail is deter-
mined by using the templates and the preoperative radiographs of the intact contralateral limb. The nail is inserted in a normograde fashion, as described in Figure 39-1. A small medial approach is made to the tibial diaphysis for fracture reduction and directing the nail into the distal bone. The distal tibial epiphysis in the cat is very short and there is a risk of inadvertent penetration of the tibiotarsal joint while seating the nail in the distal metaphyseal bone. Removing the sharp point from the end of the nail and therefore making a blunter end can help prevent penetration.
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39: Tibia and fibula Figure 39-1 (A) Normograde pinning of the tibia. (B) The pin entry point on the medial edge of the tibial plateau is reached through a small medial parapatellar incision, and the pin is inserted along the medial cortex of the tibia.
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Figure 39-2 Diagram showing positioning of a centrally threaded transosseous pin in the caudal aspect of the triangularshaped proximal tibia. Screws are also inserted in this position.
type I configuration provides sufficient stability for moderately comminuted fractures, and fractures in younger cats. Stability of a type I external skeletal fixator can be improved by using fixator systems with large connecting bars, or by using a double bar. The tubular external fixator is a valuable implant for distally located fractures (Chapter 24). A type II external fixator is applied for severely comminuted or open fractures with longer anticipated healing times. Its configuration provides more stability, and reduces the risk of premature failure. Positive-threaded pins and the employment of a correct pin insertion technique (Chapter 24) are also crucial for prevention of premature pin loosening. Type II external fixators, or very occasionally type III fixators, are also indicated if the size of the proximal or distal fragment only allows insertion of one or two pins. The type III fixator frame has the advantage of allowing insertion of additional pins from a different direction.
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39.2.4 Plating 39.2.3 External skeletal fixation The main indications for external skeletal fixation are comminuted and open fractures, and fractures located in the distal diaphysis or metaphysis. Either a closed or an open reduction can be used. If open reduction is chosen, only a minimal approach should be performed to preserve the blood supply. Closed reduction and application of external fixation is the treatment of choice for comminuted fractures with significant soft-tissue damage, and for open fractures. Closed reduction and external skeletal fixation were associated with a higher rate of malunion compared to closed reduction in one study (4), so care has to be taken to align the main fragments adequately. Older cats can have brittle bones, and iatrogenic fractures could be created if oversized transosseous pins, especially positive-threaded pins, or incorrect insertion techniques are applied. Pin size is usually 2.0 mm for the proximal tibia, and 1.6 mm for the distal tibia. Because the proximal tibia has a triangular shape, transosseous pins are inserted into the broader caudal aspect of the proximal tibia to obtain more bone purchase (Fig. 39-2). Both type I and type II configurations can be used. A type I external fixator applied on the medial side of the bone is the best choice, as the pins only penetrate the skin and do not interfere with the laterally located extensor muscles. A
Bone plates can be applied to repair closed fractures of the tibial diaphysis. Plates are positioned along the caudomedial border of the proximal tibia, because its triangular shape allows more bone purchase caudally (Fig. 39-2). The 2.7/2.0mm veterinary cuttable plate (VCP) and the 2.7-mm dynamic compression plate (DCP) are often used, although 2.7-mm screws are at the upper range of size for the feline tibia, especially in the distal diaphysis. A thick 2.0-mm DCP or a 2.0/2.7 VCP with 2.0-mm screws is more appropriate for the diameter of the distal tibia in cats. However, the 2.0-mm DCP has a limited length, which is often insufficient, and the VCP is relatively weak, unless applied in a stacked fashion (8). Another useful plate for the tibia is the 2.4-mm limited contact-DCP (LC-DCP). In summary, simple transverse fractures are anatomically reduced and stabilized with a DCP or LC-DCP applied in compression function, or with a single VCP. Long oblique fractures are reduced and stabilized with lag screws, before applying a plate in neutralization function. A plate applied in buttress function is used to treat comminuted fractures. The 2.0/2.7-mm VCP should be stacked for this purpose. A minimally invasive approach is performed without disturbing the soft-tissue attachment of the fragments in the comminuted area. The plate and rod technique is also feasible in cats, if a small intramedullary pin and 2.0-mm screws are used.
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Comminuted tibial fractures are also amenable to minimally invasive plate osteosynthesis (MIPO), in which the fracture site is not approached at all (9). Two small skin incisions are made over the medial proximal and distal metaphysis. A precontoured plate is inserted through the proximal incision and is slid along the medial surface of the bone towards distally. It is first fixed to the proximal main fragment through the local incision. The main fragments are aligned, and the plate is secured to the distal main fragment. Care is taken to avoid outward rotation.
Fractures of the proximal tibia and fibula are rare. They include Salter and Harris fractures of the proximal tibial physis in immature animals, or fractures of the tibial metaphysis in adult cats. Other fractures are exceedingly rare, but avulsion fractures of the tibial tuberosity or metaphyseal fractures extending into the stifle joint can occur.
39.3.1 Approaches to the proximal tibia and fibula
39.2.5 Internal fixators Internal fixators can be used in neutralization or buttress function instead of conventional plates to repair fractures of the tibial diaphysis. When used for diaphyseal fractures, the main advantage is the preservation of the periosteal blood supply, and the prevention of cortical necrosis, which is most beneficial in the treatment of comminuted fractures with poor vascularity. Another good indication for internal fixators are fractures near the stifle or tarsal joint, where the size of the proximal or distal main fragment only allows insertion of two screws. The 2.4-mm Unilock mandible locking plates (Chapter 24) are of sufficient strength for the tibial diaphysis. The thick 2.0-mm plates can be applied to repair distal tibial fractures, where there is little room for screw insertion. The 2.0-mm plates should be combined with an intramedullary nail if used in buttress function.
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39.3 Fractures of the proximal tibia and fibula
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The proximal tibia is approached through a medial incision (10). The combined fascia of the sartorius, gracilis, and semitendinosus muscles is sharply incised medial to the patellar ligament along the craniomedial tibial crest, and elevated from the medial aspect of the proximal tibia in a caudal direction. Care is taken not to damage the medial collateral ligament of the stifle joint.
39.3.2 Salter and Harris fractures The immature proximal tibia has two separate growth plates, one for the proximal epiphysis and one for the tibial tuberosity. These two growth plates fuse to each other between 36 and 44 weeks of age, forming a cap that sits on the metaphysis (11). This combined growth center then fuses to the
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Figure 39-3 (A, B) Preoperative and (C, D) 4-week follow-up radiographs of a 5-month-old cat with a Salter and Harris type II fracture of the proximal tibial physis. The fracture was repaired with cross pins.
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Box 39-1. Stabilization of Salter and Harris type I, II, and III fractures of the proximal tibia A medial approach to the proximal tibia is performed. Fracture reduction is assisted by holding the stifle joint in extension. The proximal fracture fragment is levered forward and medially with the help of a periosteal elevator or a mini Hohmann retractor. Delicate handling of the epiphyseal fragment is mandatory to prevent iatrogenic damage of the small bone fragment and the growth plate. A small local lateral approach is needed for insertion of Kirschner wires from the lateral side. Cross pinning: A 0.8–1.2-mm Kirschner wire is inserted from the medial edge of the tibial plateau, and is advanced in a distolateral direction to penetrate the lateral cortex. A second Kirschner wire is inserted from the lateral edge of the tibial plateau into the medial cortex (Fig. 39-4a). Unless the bone is very soft, the pin ends should be bent over to prevent pin migration. Intramedullary nail and antirotational Kirschner wire: This technique may be advantageous in Salter and Harris type II fractures with a large lateral metaphyseal fragment. The intramedullary nail is inserted first, as described above. A small Kirschner wire is then driven from the lateral edge of the tibial tuberosity across the fracture in a distomedial direction, until it engages the medial cortex (Fig. 39-4b). An additional tension band or a positional screw can be applied across the tibial tuberosity physis into the caudal
metaphysis between 50 and 76 weeks of age (11). Before fusion of the two growth centers has taken place, the two physes can fracture individually, and a Salter and Harris type I or II fracture of the proximal epiphysis (Fig. 39-3) or an avulsion fracture of the tibial tuberosity can result. Fractures occurring after fusion of the two growth centers are also classified as Salter and Harris type I or II fractures. The proximal epiphyseal fragment has a tendency to displace in a caudolateral direction relative to the tibia. The resulting change in angle of the tibial plateau compromises biomechanics of the stifle joint, and impairs its function if left untreated. The majority of cases therefore require open reduction and internal stabilization. Possible repair options for Salter and Harris type I, II, and III fractures include cross pinning (Fig. 39-3) or combining an intramedullary pin with an antirotational pin (Box 39-1). Fixation stability can be enhanced by placing an additional tension band wire across the tibial tuberosity in Salter and Harris type I and II fractures. The tension band should only be applied in older cats without further growth potential. Undisplaced proximal physeal fractures are occasionally encountered, and can be treated with external coaptation.
cortex in Salter and Harris type I and II fractures with either technique. This should only be performed in cats without further growth potential.
Figure 39-4 Options for stabilization of Salter and Harris type I and II fractures of the proximal tibia. (A) Repair of a Salter and Harris type I fracture with cross pins. (B) Internal fixation of a Salter and Harris type II fracture with an intramedullary pin and Kirschner wire, inserted from lateral.
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39.3.3 Metaphyseal fractures Metaphyseal fractures of the proximal tibia usually occur in adult cats, and are more frequent than Salter and Harris fractures (3). The proximal fragment has a tendency to tilt in a proximocranial direction because of the tension exerted by the patellar tendon. The main surgical challenge lies in being able to insert a sufficient number of screws or pins into the small proximal fragment. Treatment options for simple transverse fractures include an intramedullary pin and a simple external skeletal fixator, or a medial plate (Box 39-2). T- or L-plates allow insertion of two screws even in very small proximal fragments (Fig. 39-6). A cranial tension band fixation is added in cases with marked distraction of the cranial aspect of the fracture. Comminuted fractures usually extend into the tibial diaphysis and are treated like comminuted diaphyseal fractures, which are described later. Type II or III external skeletal fixators are advisable if the size of the proximal fragment only allows insertion of one or two pins. One author has seen several proximal transverse tibial fractures in older cats with concurrent chronic patellar fractures.
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Box 39-2. Stabilization of a simple transverse fracture of the proximal tibial metaphysis A medial approach to the proximal metaphysis is performed. The approach is extended proximally, parallel to the patellar tendon if an intramedullary pin is inserted. Intramedullary pin and type I external skeletal fixator: This repair is preferred in young cats. A 1.4–1.6-mm intramedullary pin is inserted in a normograde manner. For the medially applied external skeletal fixator, 1.4–2.0-mm transosseous pins are driven into the proximal fragment, and 1.4–1.6-mm pins are used in the distal tibial shaft (Fig. 39-5a). Smooth pins should be angled 70° to the long axis of the bone to enhance pull-out resistance. A cranial tension band wire as described in Figure 39-5b can also be applied. Plate and tension band repair: This repair is preferred in older cats. A 2.0-mm T-plate or dynamic compression plate in compression function can be used if the proximal fragment allows insertion of three screws. The plate is applied at the caudomedial edge of the tibia in order to benefit from the increased bone purchase. A 0.6–0.8-mm figure-of-eight wire is positioned across the cranial fracture line as a tension band (Fig. 39-5b). A 2.0-mm internal fixator is a good alternative if only two screws can be inserted into the proximal fragment.
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Figure 39-5 Options for stabilization of a simple transverse fracture of the proximal tibial metaphysis. (A) Repair of a simple proximal transverse fracture with an intramedullary pin and a medial type I external skeletal fixator. (B) Stabilization of a simple proximal transverse fracture using a sixhole plate and a cranial tension band wire.
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Figure 39-6 (A, B) Preoperative and (C, D) postoperative radiographs of a 2-year-old cat with a proximal metaphyseal tibial fracture. Use of a 2.0mm T-plate allowed insertion of two screws into the proximal fragment.
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39: Tibia and fibula These fractures showed remodeling of the cranial cortex of the tibia, and are thought to be stress fractures related to decreased flexion in the stifle joint, resulting in the bending force in the hindlimb being transferred to the proximal tibia. Fractures will often occur bilaterally several months apart, and most cats have a history of other non-traumatic fractures of the acetabulum, ischium, or humeral condyle. An underlying bone abnormality is suspected but unproven. The tibial fractures in these cats seem to heal best when repaired with a pin and tension band, or plate and screw and tension band technique.
39.4 Diaphyseal fractures of the tibia and fibula Fracture healing of diaphyseal tibial fractures tends to be slow, probably caused by the lack of surrounding soft tissue and the sparse blood supply. Careful tissue handling, preservation of blood supply, and respecting the principles of osteosynthesis are crucial for success. The choice of treatment for diaphyseal tibia and fibula fractures is mainly based on fracture severity and location, age, body weight, temperament of the patient, and implants available (Chapters 13 and 24). The various implant systems have their own advantages and disadvantages. Closed reduction and external skeletal fixation of severe tibial fractures seem to reduce the incidence of osteomyelitis, when compared to open reduction and internal fixation methods (4). It is therefore often the method of choice for severely comminuted and open fractures. Plate osteosynthesis has the advantage of easier postoperative management compared to external skeletal fixation, making it more suitable for cats that are difficult to handle. On the other hand, plate osteosynthesis causes more iatrogenic damage to the sparse blood supply, and tibial fractures stabilized with bone plates had the longest healing times in two studies (2, 4).
39.4.1 Approach to the tibial diaphysis The tibial diaphysis is approached via a medial skin incision. The saphenous vein is spared. It can be gently dissected free and retracted with a Penrose drain.
39.4.2 Simple transverse and short oblique fractures Simple transverse and short oblique fractures may be treated with a cast after reduction. Tibial fractures with an intact fibula are also amenable to be treated with external coaptation because the fibula acts as an internal splint. The disadvantage of external coaptation is the prolonged immobilization of adjacent joints, which can cause cartilage degeneration, periarticular fibrosis, and muscle contractures. Therefore,
only fractures expected to have achieved clinical union within 4 weeks should be treated with external coaptation. Incomplete and undisplaced fractures in very young kittens may be treated with a splinted bandage. For complete fractures and fractures in older cats a full cast provides more stability. Application and maintenance of bandages and casts are described in Chapter 22. It is important to immobilize the tarsus in a flexed position to prevent contracture of the gastrocnemius muscle. Contraction of the gastrocnemius muscle can occur within days in immature cats. Internal stabilization or external skeletal fixation results in faster return to function and allows immediate weightbearing and motion of adjacent joints. Simple fractures of both the tibia and fibula in adult cats are therefore usually treated surgically. A type I external skeletal fixator, with or without intramedullary pin, a medially applied 2.7- or 2.0mm DCP in compression function, a single 2.0/2.7-mm VCP, or a 2.4-mm LC-DCP are all implants that could be used (Box 39-3). Open fractures are treated with external skeletal fixation.
39.4.3 Long oblique and multifragmentary reducible fractures Simple long oblique or reducible multifragment fractures of the tibia are not very common. They are usually treated with anatomic reduction and stable internal fixation. Anatomic fracture reduction enhances fixation stability by creating load sharing of the cortex, but has the disadvantage of causing soft-tissue trauma and bone devascularization. It should only be attempted in long oblique fractures, and fractures with one large reducible butterfly fragment. If it seems questionable from preoperative radiographs that anatomic reduction is possible, the fracture is treated as a comminuted fracture (section below). Intramedullary pinning and cerclage wires, and interfragmentary lag screws with a neutralization plate, are treatment options for anatomic reduction of long oblique fractures. Stabilization with a lag screw and a neutralization plate is preferred over fixation with an intramedullary pin and cerclage wires in the tibia (Fig. 39-8 and Box 39-4). Application of cerclage wires around the tibia requires additional softtissue dissection between the tibia and fibula, and has the potential for further diminution of the blood supply. Long oblique fractures can also be stabilized with an intramedullary pin and external skeletal fixator (Box 39-4). The intramedullary pin enhances bending stability, and the external skeletal fixation pins prevent axial collapse and rotation. This type of fixation does not provide interfragmentary compression, but fracture healing should be faster because of preservation of local blood supply. Open fractures are also treated with external skeletal fixation.
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Box 39-3. Stabilization of a simple transverse or short oblique fracture of the tibial diaphysis Simple fractures treated with intramedullary pin and external skeletal fixator can be reduced and stabilized in a closed manner. A medial approach to the tibial shaft is performed for plate osteosynthesis. The fracture is anatomically reduced. Intramedullary pin and type I external skeletal fixator: This combination is commonly used to treat simple fractures of the tibia in young cats. An intramedullary pin is inserted in a normograde manner to align the fracture fragments. Two transosseous pins are then placed in each fracture fragment to provide rotational stability (Fig. 397a). Usually, 1.4–2.0-mm pins are used in the proximal tibia, and 1.4–1.6-mm pins in the distal tibia. Plate osteosynthesis: The plate is applied to the medial tibial surface. Interfragmentary compression is exerted if a dynamic compression plate (DCP) or limited contact-DCP (LC-DCP) is used. One screw on each side of the fracture is applied eccentrically for interfragmentary compression. Overall, at least three screws are required per fragment. It is advisable to select a longer plate and leave some holes empty, rather than taking a short plate and filling all holes (Fig. 39-7b). Care must be taken not to leave a single empty plate hole at the level of the fracture.
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Figure 39-7 Options for stabilization of simple transverse or short oblique fractures of the tibial diaphysis. (A) Repair of a transverse diaphyseal tibial fracture with an intramedullary pin and a type I external skeletal fixator. (B) Internal fixation of a short oblique tibial fracture with a medially applied plate. Anatomic reduction is important.
Spiral fractures of the tibia with an intact fibula can be successfully treated with external coaptation in immature cats (12). External coaptation for long oblique fractures is not recommended in adult cats.
39.4.4 Comminuted fractures
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Figure 39-8 A 10-month-old cat with a long oblique fracture of the tibia. (A) Preoperative radiograph showing a long oblique fracture of the distal tibial shaft. (B) The fracture was stabilized with a 2.0-mm lag screw and a 1.5/2.0mm veterinary cuttable plate in neutralization function. This relatively weak and short plate could be used because the fibula was intact. (C) The fracture was healed after 5 weeks.
Comminuted and open fractures of the tibia are common. Open fractures are commonly located in the distal diaphysis. Closed, mildly comminuted fractures can be treated with a plate in buttress function, if the main fragments allow insertion of a sufficient number of screws. Internal fixators can also be used as buttress implants, and have the advantage of preserving cortical blood supply and requiring only two screws per fragment (Fig. 39-10). External skeletal fixation is the treatment of choice for open fractures and is also commonly used to stabilize comminuted fractures. A type I or II external skeletal fixator is used depending on fracture location and severity. A type I external skeletal fixator with three transosseous pins per fragment is adequate for mild to moderate comminuted fractures in younger cats. Healing can take several months in severely comminuted and open tibia fractures (4) (Fig. 39-11), and
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Box 39-4. Stabilization of long oblique or reducible butterfly fractures of the tibial diaphysis A medial approach to the tibial shaft is performed if anatomic fracture reduction and interfragmentary compression are planned. Closed reduction or a minimally invasive approach can be used for external skeletal fixation. Lag screws and neutralization plate: The fracture is anatomically reduced and reduction is maintained with pointed reduction forceps. One or two 2.0-mm lag screws are inserted perpendicular to the fracture line(s). A long plate is then applied in neutralization function (Fig. 39-9a). At least three screws should be inserted proximal and distal to the limit of the fracture. If fracture configuration allows, the lag screws can also be inserted directly through the plate. Intramedullary pin and external skeletal fixator: An intramedullary pin is inserted normograde. The fracture can be held in reduction with pointed reduction forceps while transosseous pins are inserted. Two to three transosseus pins are inserted per fragment (Fig. 39-9b). Size 2.0mm pins are usually used in the proximal metaphysis, and 1.4–1.6-mm pins in the diaphysis and distal metaphysis.
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Figure 39-9 Options for stabilization of long oblique fractures, or reducible fractures with a butterfly fragment, of the tibial diaphysis. (A) Stabilization of a tibial fracture with a butterfly fragment with lag screws and a neutralization plate. (B) Repair of a long oblique fracture in the tibial shaft with an intramedullary pin and a type I external skeletal fixator.
Figure 39-10 (A) Preoperative, (B) postoperative, and (C) 1-year follow-up radiographs of a cat with a comminuted fracture of the distal shaft of the tibia, stabilized with an internal fixator (2.4-mm Unilock plate). Note the small gap between plate and bone, and that only two screws were inserted in the small distal fragment.
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Figure 39-11 Delayed healing of a comminuted fracture of the tibia. (A, B) Preoperative radiographs show a highly comminuted fracture. (C, D) Radiographs taken 3 months after closed reduction and stabilization with a type II external skeletal fixator. The most proximal pin is broken, there is a non-union of the most proximal part of the fracture, and the proximal fragment is tilted cranially. (E, F) Radiographs taken another 3 months after replacement of proximal pins, insertion of a cancellous bone graft, and application of a tension band to pull the proximal fragment distally and caudally. Callus formation is now evident. (G, H) Radiographs after 11 months finally show healing. The type I external skeletal fixator was left in place for another month.
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Box 39-5. Stabilization of comminuted fractures of the tibial diaphysis Closed reduction can be used to apply an external skeletal fixator. A surgical approach is usually performed for plating, but care is taken to disturb the soft-tissue attachments of the fragments and local blood supply minimally. The least invasive approach to apply a plate is the minimally invasive plate osteosynthesis (MIPO) technique. Bone grafting is indicated if large fracture gaps or devitalized fracture fragments are present. External skeletal fixation: Type I and II external fixators are mostly used with 2.0-mm transosseous pins proximally, and 1.6-mm pins distally. The most proximal and most distal positive-threaded transosseous pins are inserted first, parallel to the stifle and tarsal joint. These pins are end-threaded for a type I fixator (Fig. 39-12a), and centrally threaded for a type II fixator (Fig. 39-12b). The fracture is reduced indirectly by bringing the two pins parallel to each other, and connecting them with the external bar. This relies on accurate pin positioning, and overall alignment should also be checked by flexing and extending the hock and stifle to ensure that they are bending in the same plane. Care is taken to avoid valgus, outward rotation, craniocaudal malalignment, and overdistraction of
the main fragments. Two additional positive end-threaded or smooth pins are then added from medial per main fragment as half pins. Buttress plate: A 2.7-mm dynamic compression plate (DCP), a 2.4-mm limited contact-DCP (LC-DCP) or a stacked 2.0/2.7-mm veterinary cuttable plate can be used. The plate should span the whole length of the tibia, and should allow insertion of at least three screws proximally and distally (Fig. 39-12c). Minimal plate contouring is necessary. The plate is fixed to the proximal fragment first. Then reduction is achieved by securing the distal fragment to the plate. The intervening fracture fragments are not manipulated. An intramedullary pin can give additional bending stability, especially if the proximal or distal fragments are too short to allow insertion of three screws. The intramedullary pin is inserted prior to plate application, and helps in obtaining alignment. The disadvantage is that it may be difficult to pass the screws in the narrow distal diaphysis. Internal fixator: An internal fixator, for example the 2.4-mm Unilock plate, can be applied in buttress function, as shown in the radiographs of Figure 39-10. Figure 39-12 Options for stabilization of comminuted fractures of the tibial shaft. (A) Stabilization of a mildly comminuted mid diaphyseal fracture with a type I external skeletal fixator. Three transosseous pins are inserted per fragment. (B) Repair of a severely comminuted fracture of the tibia with a type II external skeletal fixator. At least two pins should be inserted per fragment. (C) Internal fixation of a comminuted fracture using a buttress plate.
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pin loosening is likely to occur during such long healing times if simple frames are used. Severely comminuted fractures, especially in older cats, are therefore best stabilized with a type II configuration. A type II or even type III configuration is also used if a small proximal or distal metaphyseal segment
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only allows insertion of the minimum number of pins from two sides or planes (Box 39-5). An interlocking nail is another treatment option for comminuted fractures in the proximal or mid diaphyseal area in larger cats. The tibia and its intramedullary canal
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Part 7: Treatment of selected surgical diseases and injuries Figure 39-13 (A) Preoperative, (B) postoperative, and (C) 3month follow-up radiographs of a cat with a very distal oblique metaphyseal fracture of the tibia and fibula. A hybrid circular external fixator was used for stabilization. The fracture had healed 3 months after surgery.
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Distal fractures of the tibia and fibula include metaphyseal fractures in adult cats, Salter and Harris fractures in growing cats, and tarsal joint fractures. Lateral and medial malleolar fractures are common distal tibial and fibular fractures, and are associated with tarsal instability.
fragment can make it difficult to insert a sufficient number of screws or transosseous pins. External skeletal fixators can often be used after closed reduction. The tubular external skeletal fixator is especially suitable for distal metaphyseal fractures because it allows insertion of a larger number of transosseous pins over a small distance than other external skeletal fixator systems (14) (Chapter 24). A hybrid construct with a circular external skeletal fixator (15, 16) (Fig. 39-13) or a fixator with an acrylic bar also allows fixation of very small fragments, and is useful for distally located fractures. The small distal fragment does not usually allow insertion of a sufficient number of screws with a 2.7-mm DCP. A 2.0mm thick DCP or a 2.0/2.7 or 1.5/2.0 VCP are therefore used. To compensate for the lower stability of these shorter and weaker plates, an intramedullary pin can be inserted prior to plate application if there is concern about construct stability. The cuttable plate can be used in sandwich function to enhance bending stability. Internal fixators can also be used in fractures close to joints where it is only possible to insert two screws per fragment (Box 39-6).
39.5.1 Approaches to the distal tibia and fibula
39.5.3 Salter and Harris fractures
A medial approach is used to access the distal tibial diaphysis and the medial malleolus. The fibula is approached from laterally.
The distal physis of the tibia closes between 40 and 52 weeks of age in intact cats (11). Fractures of the distal tibia are usually Salter and Harris type I or II fractures (Fig. 39-15). Salter and Harris type III fractures have also been reported (17). Salter and Harris type I and II fractures are best stabilized with cross pins (Box 39-7). Conservative treatment with a cast is an option in undisplaced Salter and Harris type I or II fractures, particularly in young kittens. Cats younger than 6 or 7 months with further growth potential are at risk of development of growth disturbances if premature physeal closure occurs.
narrow distally, so with the current range of interlocking nail sizes, the nail can only be used in large cats with fractures involving the mid to proximal third diaphysis (7). Fractures with devitalized fracture fragments and fractures with large fracture gaps are at risk of developing non-union and should be grafted. Excessive distraction of the main fragments creating large fracture gaps should be avoided during external skeletal fixation repair. Cancellous bone grafting has been shown to be capable of preventing non-unions of the tibia in the presence of large fracture gaps (13). Autogenous or allogenous cancellous bone graft, or a combination of the two, can be used. Open fractures may require delay of the grafting until the wound is considered to be free of infection.
39.5 Fractures of the distal tibia and fibula
39.5.2 Metaphyseal fractures of the distal tibia Distal metaphyseal tibial fractures occur commonly in cats, and the incidence of open fractures is relatively high. Closed fractures can be stabilized with plate osteosynthesis or external skeletal fixation. The treatment of choice for open fractures is an external skeletal fixator. The small size of the distal
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Box 39-6. Stabilization of metaphyseal fractures of the distal tibia Although closed reduction is possible with external skeletal fixation, a small medial approach to the distal fragment is often performed for ease of pin positioning. A medial approach is also used for plate application. Tubular external skeletal fixator: The distal transosseous pin is inserted first, close to and perpendicular to the tarsal joint. A 1.6-mm, or maximally a 2.0 positive endthreaded pin, is used. The direction of this first pin is critical, as it will determine the position of the connecting tube, perpendicular to the pin. A 6.0-mm tube is secured to the pin. The fracture is reduced and a transosseous pin is inserted into the proximal fragment. If the distal pin is placed correctly, the tube will be positioned parallel to the long axis of the tibia. At least three pins are inserted into the proximal fragment, and at least two or three are inserted into the distal fragment (Fig. 39-14a). If an intramedullary pin is also used it is inserted prior to application of the fixator. Intramedullary pin and plate: An intramedullary pin, comprising approximately 30% of the diameter of the distal medullary canal, is inserted in a normograde fashion. A long 2.0-mm dynamic compression plate or a 1.5/2.0 veterinary cuttable plate (VCP) is then applied in neutralization or buttress function. If used in buttress function, consider stacking or sandwiching the VCP. Screws must engage at least four cortices in the distal and proximal fragment (Fig. 39-14b), but six or even eight cortices are preferred, especially in the proximal bone.
A
B
Internal fixator: A 2.0-mm locking plate can be used as a neutralization or buttress implant, with two screws in the distal fragment, and three in the proximal fragment.
A
B
Figure 39-14 Stabilization options for distal metaphyseal fractures of the tibia. (A) Repair of a simple transverse fracture with a 6.0-mm tubular external skeletal fixator. (B) Internal fixation of an oblique fracture with an intramedullary pin and a 12-hole 2.0-mm dynamic compression plate.
C
D
Figure 39-15 (A, B) A 5-month-old cat with a Salter and Harris type I fracture of the distal tibia, and a fracture of the distal fibula. (C, D) Postoperative radiographs show reduction and stabilization with two Kirschner wires inserted as cross pins.
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Box 39-7. Stabilization of Salter and Harris type I and II fractures of the distal tibia An approach to the distal tibia and medial malleolus is performed. The fracture is carefully reduced, using distal traction on the flexed tarsus and manipulation of the foot and careful levering with a freer periosteal elevator. Anatomic reduction is mandatory for fixation stability. A 0.9–1.2-mm Kirschner wire is driven from the medial malleolus in a proximolateral direction to be seated in the lateral cortex of the distal tibia. Care has to be taken not to enter the tibiotarsal joint. A second Kirschner wire is then inserted from the distal fibula across the tibia, exiting through the medial cortex (Fig. 39-16). A separate lateral skin incision is required for pin placement. It is important that both pins are securely engaged in the distal tibial fragment. If one or both pins are inserted subperiostally, loss of reduction and instability may occur. Figure 39-16 Cross pinning of a Salter and Harris type II fracture of the distal tibia with one pin inserted from the medial malleolus, and one from the lateral malleolus.
39.5.4 Fractures of the distal tibia involving the tarsal joint Epiphyseal fractures include malleolar fractures, cranial slab fractures, and complex articular fractures. Fractures of the lateral or medial malleolus are the most common type of distal tibia and fibula fractures. The malleoli serve as a medial and lateral restraint to the talus, and they are the insertion sites for the tarsal collateral ligaments. Malleolar fractures result in talocrural instability, and are covered in Chapter 40. Cranial slab fractures of the distal tibia are encountered occasionally in cats. These fractures cause tarsal instability,
because the dorsal rim of the tibia is part of the insertion of the joint capsule. If the fragment is large enough, it is stabilized with a small lag screw or a small threaded pin to restore congruity of the joint surface and joint stability. If the fragment is too small to be reattached, it is probably best removed, followed by external immobilization of the tarsus for 2–3 weeks in order to allow healing of the insertion of the joint capsule. Fortunately, complex fractures of the epiphysis of the tibia are rare, but they may occur after falls and gunshot wounds. If comminution precludes anatomic and stable repair of the tibiotalar joint surface, pantarsal arthrodesis is the only treatment option (Chapter 40).
39.6 Postoperative treatment and prognosis External coaptation is usually not necessary after stable fixation of metaphyseal and diaphyseal fractures. Follow-up radiographs are generally performed after 4–6 weeks. Fractures of the tibial diaphysis are more prone to develop complications than fractures of other bones, possibly due to the high incidence of comminuted and open fractures, and the poor soft-tissue covering. Both fracture-healing disorders and osteomyelitis can occur. Fracture healing is slower for comminuted and high-grade open fractures (4), and some severely comminuted fractures may take several months to heal. The tibia has been reported to be predisposed to non-unions, with an incidence of approximately 15% (18). Non-unions are most likely to develop after comminuted fractures and open fractures, in older and overweight cats (18). Osteomyelitis occurs in up to 15% of tibial diaphyseal fractures (2, 4). Predisposing factors include wound contamination or infection in the presence of open fractures, and poor vascularity caused by soft-tissue trauma. Proximal and distal physeal fractures are expected to heal rapidly, but a splinted bandage should be applied for approximately 2 weeks to protect the repair. Radiographs are performed after 2–3 weeks to detect premature physeal closure, and to evaluate fixation stability. The Kirschner wire ends may cause irritation of periarticular structures, and should be removed in the presence of local swelling, seroma formation, or radiographic evidence of implant migration. Prognosis after distal tibial fractures depends mainly on the ability to achieve anatomic reduction of the fragments and a stable fracture repair. Malalignment or instability will cause dysfunction and degenerative joint disease of the tibiotarsal joint. One study reported a suboptimal outcome in 18% of distal physeal fractures, perceptible as continued lameness, malunion, and reduced range of motion of the tarsal joint (3).
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References and further reading 1. Hill FWG. A survey of bone fractures in the cat. J Small Anim Pract 1977;18:457–463. 2. Boone EG, et al. Fractures of the tibial diaphysis in dogs and cats. J Am Vet Med Assoc 1986;188:41–45. 3. Brunnberg L. Tibia and fibular fractures in the cat. Kleintierpraxis 2003;48:9–23. 4. Richardson EF, Thacher CW. Tibial fractures in cats. Compend Continuing Educ 1993;15:383–394. 5. Whitney WO, Mehlhaff CJ. High-rise syndrome in cats. J Am Vet Med Assoc 1987;191:1399–1403. 6. Payne J, et al. Comparison of normograde and retrograde intramedullary pinning of feline tibias. J Am Anim Hosp Assoc 2005;41:56–60. 7. Duhautois B. Use of veterinary interlocking nails for diaphyseal fractures in dogs and cats: 121 cases. Vet Surg 2003;32:8–20. 8. Fruchter AM, Holmberg DL. Mechanical analysis of veterinary cuttable plate. Compend Continuing Educ 1991;4:116–119. 9. Schmökel HG, et al. Percutaneous plating of tibial fractures in two dogs. Vet Comp Orthop Traumatol 2003;16:191–195. 10. Piermattei DL, Johnson KA. An atlas of surgical approaches to the bones and joints of the dog and the cat, 4th edn. Philadelphia: WB Saunders; 2004.
505 11. Smith RN. Fusion of ossification centres in the cat. J Small Anim Pract 1969;10:523–530. 12. Zaal MD, Hazewinkel HAW. Treatment of isolated tibial fractures in cats and dogs. Vet Q 1997;119:191–194. 13. Toombs JP, Wallace LJ. Evaluation of autogeneic and allogeneic cortical chip grafting in a feline tibial nonunion model. Am J Vet Res 1985;46:519–528. 14. Haas B, et al. Use of the tubular external fixator in the treatment of distal radial and ulnar fractures in small dogs and cats. Vet Comp Orthop Traumatol 2003;16:132–137. 15. Farese JP, et al. Use of IMEX SK-circular external fixator hybrid constructs for fracture stabilization in dogs and cats. J Am Anim Hosp Assoc 2002;38:279–289. 16. Clarke SP, Carmichael S. Treatment of distal diaphyseal fractures using hybrid external skeletal fixation in three dogs. J Small Anim Pract 2006;47:98–103. 17. Boone EG, et al. Distal tibial fractures in dogs and cats. J Am Vet Med Assoc 1986;188:36–40. 18. Nolte DM, et al. Incidence of and predisposing factors for nonunion of fractures involving the appendicular skeleton in cats: 18 cases (1998–2002). J Am Vet Med Assoc 2005;226:77–82.
39
Tibia and fibula
K. Voss, S.J. Langley-Hobbs, P.M. Montavon
Fractures of the tibia and/or fibula are common, accounting for about 10–20% of fractures in cats (1, 2). Usually both the tibia and fibula are fractured. The fractures are often caused by falls from a height, but may occur after any type of trauma (3–5). Most of the fractures of the feline tibia involve the middle and distal diaphysis (2–4). The diaphysis of the tibia is surrounded by minimal soft tissue, and many tibial fractures are comminuted and/or open. The incidence of open fractures of the tibial diaphysis has been reported to be as high as 21–46% (3, 4). Cats with high-rise syndrome sustain open fractures more commonly than cats with other causes of trauma (4). The high incidence of comminuted and open fractures, and the limited extraosseous blood supply and soft-tissue envelope, is likely to account for the higher rate of complications, such as delayed union, non-union, and osteomyelitis, when compared to fractures of other bones.
39.1 Surgical anatomy The tibia is a straight bone with a triangular shape in the proximal third and a round to oval shape in the distal twothirds. The fibula is very thin in cats and does not contribute to weight-bearing, but it is important for stifle and tarsal joint stability because it serves as the attachment site for the lateral collateral ligaments of both joints. The distal fibula has a ligamentous connection to the tibia, the inferior tibiofibular ligament. This ligament is important for stability of the tarsal joint, because the medial and lateral malleolus are not only the sites of origin of the tarsal collateral ligaments but also serve as a medial and lateral restraint for the trochlea of the talus (Chapter 40).
39.2 Stabilization techniques Many stabilization methods can be used to treat tibial fractures. The reader is referred to Chapters 13 and 24 to review the factors influencing the choice of treatment and implants for different fracture types. External coaptation with a cast is successful for stabilization of certain tibial fractures in young cats, such as greenstick, simple transverse fractures, and tibial fractures with an intact fibula. Indications and application techniques for external coaptation are described in Chapter 22. The tibia is the ideal bone for closed reduction and external skeletal fixation, because it is surrounded by
minimal soft tissue. This technique is most useful for comminuted and open fractures. Fracture types occurring in the proximal tibia, the diaphysis, and the distal bone, and possible options for treating them are summarized in Table 39-1.
39.2.1 Intramedullary pinning Although the straight form of the tibia is ideal for inserting intramedullary pins, they are not used as commonly in the tibia, as compared to the humerus and femur. Intramedullary pins should always be inserted in a normograde fashion into the tibia because retrograde pinning in cats invariably results in penetration of the patellar tendon (6). Intramedullary pins must be used in conjunction with implants resistant to rotation and axial compression, dependent on the fracture type. The size of the pin is selected according to the smallest diameter of the distal medullary cavity. If the pin is combined with a plate or an external fixator, the size selected should be around 30% of the diameter of the distal medullary canal to leave room for insertion of the screws or pins. Selecting too large a pin and then trying to pass pins or screws past the pin can result in cortical fissures. Kirschner wires of a diameter of 1.2–2.0 mm are usually adequate. A medial parapatellar approach to the stifle is performed for normograde intramedullary pin insertion. The pin entry point is located on the medial aspect of the tibial plateau, between the insertion of the patellar tendon and medial collateral ligament, cranial to the intermeniscal ligament (Fig. 39-1). Holding the stifle joint in 90° of flexion facilitates insertion of the pin. The pin is then advanced along the medial cortex using a Jacobs chuck until its tip is located close to the fracture. The fracture is reduced, and the pin is further advanced until resistance is felt at the distal epiphysis. The distal tibial epiphysis is a short piece of bone, so great care must be taken not to push the pin into the tibiotarsal joint. The proximal end of the pin is cut as short as possible to avoid irritation of the patellar tendon and parapatellar tissue.
39.2.2 Interlocking nailing The use of an interlocking nail for stabilization of feline tibial fractures has been described as part of a large
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Fracture localization
Fracture type
Stabilization methods
Proximal tibia
Salter and Harris type II
Parallel or cross pinning IM pin and antirotational K wire Lag screw and antirotational K wire External coaptation IM pin and: – ESF – plate – internal fixator Plate and tension band Internal fixator and tension band IM pin and: – ESF – plate – internal fixator IM pin and ESF Compression plate Internal fixator External coaptation Lag screw and neutralization plate Lag screw and internal fixator IM pin and ESF IM pin and cerclage wire ESF (closed reduction) ESF ± IM pin Buttress plate Internal fixator Interlocking nail ESF and IM pin Plate ± IM pin Internal fixator ± IM pin IM pin and: – ESF – plate – internal fixator Cross pinning
Simple metaphyseal
Comminuted metaphyseal
Diaphysis
Simple transverse or short oblique
Simple long oblique and reducible multifragmentary Comminuted
Distal tibia
Simple metaphyseal
Comminuted metaphyseal
Salter and Harris type I
Table 39-1. A summary of feline tibial fractures and selected treatment options
IM pin, intramedullary pin; ESF, external skeletal fixator.
retrospective study involving nail use in dogs and cats (7). The interlocking nail was applied infrequently in the tibia in the cat, when compared to other long bones, but from the information obtained from the study no complications occurred with its use. With the current range of interlocking nail sizes, the nail can only be used in large cats with fractures involving the mid to proximal third of the tibial diaphysis. The 4.0-mm nail with 2.0-mm screws or bolts is the most appropriate size to use, and the length of the nail is deter-
mined by using the templates and the preoperative radiographs of the intact contralateral limb. The nail is inserted in a normograde fashion, as described in Figure 39-1. A small medial approach is made to the tibial diaphysis for fracture reduction and directing the nail into the distal bone. The distal tibial epiphysis in the cat is very short and there is a risk of inadvertent penetration of the tibiotarsal joint while seating the nail in the distal metaphyseal bone. Removing the sharp point from the end of the nail and therefore making a blunter end can help prevent penetration.
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39: Tibia and fibula Figure 39-1 (A) Normograde pinning of the tibia. (B) The pin entry point on the medial edge of the tibial plateau is reached through a small medial parapatellar incision, and the pin is inserted along the medial cortex of the tibia.
B
Figure 39-2 Diagram showing positioning of a centrally threaded transosseous pin in the caudal aspect of the triangularshaped proximal tibia. Screws are also inserted in this position.
type I configuration provides sufficient stability for moderately comminuted fractures, and fractures in younger cats. Stability of a type I external skeletal fixator can be improved by using fixator systems with large connecting bars, or by using a double bar. The tubular external fixator is a valuable implant for distally located fractures (Chapter 24). A type II external fixator is applied for severely comminuted or open fractures with longer anticipated healing times. Its configuration provides more stability, and reduces the risk of premature failure. Positive-threaded pins and the employment of a correct pin insertion technique (Chapter 24) are also crucial for prevention of premature pin loosening. Type II external fixators, or very occasionally type III fixators, are also indicated if the size of the proximal or distal fragment only allows insertion of one or two pins. The type III fixator frame has the advantage of allowing insertion of additional pins from a different direction.
A
39.2.4 Plating 39.2.3 External skeletal fixation The main indications for external skeletal fixation are comminuted and open fractures, and fractures located in the distal diaphysis or metaphysis. Either a closed or an open reduction can be used. If open reduction is chosen, only a minimal approach should be performed to preserve the blood supply. Closed reduction and application of external fixation is the treatment of choice for comminuted fractures with significant soft-tissue damage, and for open fractures. Closed reduction and external skeletal fixation were associated with a higher rate of malunion compared to closed reduction in one study (4), so care has to be taken to align the main fragments adequately. Older cats can have brittle bones, and iatrogenic fractures could be created if oversized transosseous pins, especially positive-threaded pins, or incorrect insertion techniques are applied. Pin size is usually 2.0 mm for the proximal tibia, and 1.6 mm for the distal tibia. Because the proximal tibia has a triangular shape, transosseous pins are inserted into the broader caudal aspect of the proximal tibia to obtain more bone purchase (Fig. 39-2). Both type I and type II configurations can be used. A type I external fixator applied on the medial side of the bone is the best choice, as the pins only penetrate the skin and do not interfere with the laterally located extensor muscles. A
Bone plates can be applied to repair closed fractures of the tibial diaphysis. Plates are positioned along the caudomedial border of the proximal tibia, because its triangular shape allows more bone purchase caudally (Fig. 39-2). The 2.7/2.0mm veterinary cuttable plate (VCP) and the 2.7-mm dynamic compression plate (DCP) are often used, although 2.7-mm screws are at the upper range of size for the feline tibia, especially in the distal diaphysis. A thick 2.0-mm DCP or a 2.0/2.7 VCP with 2.0-mm screws is more appropriate for the diameter of the distal tibia in cats. However, the 2.0-mm DCP has a limited length, which is often insufficient, and the VCP is relatively weak, unless applied in a stacked fashion (8). Another useful plate for the tibia is the 2.4-mm limited contact-DCP (LC-DCP). In summary, simple transverse fractures are anatomically reduced and stabilized with a DCP or LC-DCP applied in compression function, or with a single VCP. Long oblique fractures are reduced and stabilized with lag screws, before applying a plate in neutralization function. A plate applied in buttress function is used to treat comminuted fractures. The 2.0/2.7-mm VCP should be stacked for this purpose. A minimally invasive approach is performed without disturbing the soft-tissue attachment of the fragments in the comminuted area. The plate and rod technique is also feasible in cats, if a small intramedullary pin and 2.0-mm screws are used.
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Comminuted tibial fractures are also amenable to minimally invasive plate osteosynthesis (MIPO), in which the fracture site is not approached at all (9). Two small skin incisions are made over the medial proximal and distal metaphysis. A precontoured plate is inserted through the proximal incision and is slid along the medial surface of the bone towards distally. It is first fixed to the proximal main fragment through the local incision. The main fragments are aligned, and the plate is secured to the distal main fragment. Care is taken to avoid outward rotation.
Fractures of the proximal tibia and fibula are rare. They include Salter and Harris fractures of the proximal tibial physis in immature animals, or fractures of the tibial metaphysis in adult cats. Other fractures are exceedingly rare, but avulsion fractures of the tibial tuberosity or metaphyseal fractures extending into the stifle joint can occur.
39.3.1 Approaches to the proximal tibia and fibula
39.2.5 Internal fixators Internal fixators can be used in neutralization or buttress function instead of conventional plates to repair fractures of the tibial diaphysis. When used for diaphyseal fractures, the main advantage is the preservation of the periosteal blood supply, and the prevention of cortical necrosis, which is most beneficial in the treatment of comminuted fractures with poor vascularity. Another good indication for internal fixators are fractures near the stifle or tarsal joint, where the size of the proximal or distal main fragment only allows insertion of two screws. The 2.4-mm Unilock mandible locking plates (Chapter 24) are of sufficient strength for the tibial diaphysis. The thick 2.0-mm plates can be applied to repair distal tibial fractures, where there is little room for screw insertion. The 2.0-mm plates should be combined with an intramedullary nail if used in buttress function.
A
39.3 Fractures of the proximal tibia and fibula
B
The proximal tibia is approached through a medial incision (10). The combined fascia of the sartorius, gracilis, and semitendinosus muscles is sharply incised medial to the patellar ligament along the craniomedial tibial crest, and elevated from the medial aspect of the proximal tibia in a caudal direction. Care is taken not to damage the medial collateral ligament of the stifle joint.
39.3.2 Salter and Harris fractures The immature proximal tibia has two separate growth plates, one for the proximal epiphysis and one for the tibial tuberosity. These two growth plates fuse to each other between 36 and 44 weeks of age, forming a cap that sits on the metaphysis (11). This combined growth center then fuses to the
C
D
Figure 39-3 (A, B) Preoperative and (C, D) 4-week follow-up radiographs of a 5-month-old cat with a Salter and Harris type II fracture of the proximal tibial physis. The fracture was repaired with cross pins.
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Box 39-1. Stabilization of Salter and Harris type I, II, and III fractures of the proximal tibia A medial approach to the proximal tibia is performed. Fracture reduction is assisted by holding the stifle joint in extension. The proximal fracture fragment is levered forward and medially with the help of a periosteal elevator or a mini Hohmann retractor. Delicate handling of the epiphyseal fragment is mandatory to prevent iatrogenic damage of the small bone fragment and the growth plate. A small local lateral approach is needed for insertion of Kirschner wires from the lateral side. Cross pinning: A 0.8–1.2-mm Kirschner wire is inserted from the medial edge of the tibial plateau, and is advanced in a distolateral direction to penetrate the lateral cortex. A second Kirschner wire is inserted from the lateral edge of the tibial plateau into the medial cortex (Fig. 39-4a). Unless the bone is very soft, the pin ends should be bent over to prevent pin migration. Intramedullary nail and antirotational Kirschner wire: This technique may be advantageous in Salter and Harris type II fractures with a large lateral metaphyseal fragment. The intramedullary nail is inserted first, as described above. A small Kirschner wire is then driven from the lateral edge of the tibial tuberosity across the fracture in a distomedial direction, until it engages the medial cortex (Fig. 39-4b). An additional tension band or a positional screw can be applied across the tibial tuberosity physis into the caudal
metaphysis between 50 and 76 weeks of age (11). Before fusion of the two growth centers has taken place, the two physes can fracture individually, and a Salter and Harris type I or II fracture of the proximal epiphysis (Fig. 39-3) or an avulsion fracture of the tibial tuberosity can result. Fractures occurring after fusion of the two growth centers are also classified as Salter and Harris type I or II fractures. The proximal epiphyseal fragment has a tendency to displace in a caudolateral direction relative to the tibia. The resulting change in angle of the tibial plateau compromises biomechanics of the stifle joint, and impairs its function if left untreated. The majority of cases therefore require open reduction and internal stabilization. Possible repair options for Salter and Harris type I, II, and III fractures include cross pinning (Fig. 39-3) or combining an intramedullary pin with an antirotational pin (Box 39-1). Fixation stability can be enhanced by placing an additional tension band wire across the tibial tuberosity in Salter and Harris type I and II fractures. The tension band should only be applied in older cats without further growth potential. Undisplaced proximal physeal fractures are occasionally encountered, and can be treated with external coaptation.
cortex in Salter and Harris type I and II fractures with either technique. This should only be performed in cats without further growth potential.
Figure 39-4 Options for stabilization of Salter and Harris type I and II fractures of the proximal tibia. (A) Repair of a Salter and Harris type I fracture with cross pins. (B) Internal fixation of a Salter and Harris type II fracture with an intramedullary pin and Kirschner wire, inserted from lateral.
A
B
39.3.3 Metaphyseal fractures Metaphyseal fractures of the proximal tibia usually occur in adult cats, and are more frequent than Salter and Harris fractures (3). The proximal fragment has a tendency to tilt in a proximocranial direction because of the tension exerted by the patellar tendon. The main surgical challenge lies in being able to insert a sufficient number of screws or pins into the small proximal fragment. Treatment options for simple transverse fractures include an intramedullary pin and a simple external skeletal fixator, or a medial plate (Box 39-2). T- or L-plates allow insertion of two screws even in very small proximal fragments (Fig. 39-6). A cranial tension band fixation is added in cases with marked distraction of the cranial aspect of the fracture. Comminuted fractures usually extend into the tibial diaphysis and are treated like comminuted diaphyseal fractures, which are described later. Type II or III external skeletal fixators are advisable if the size of the proximal fragment only allows insertion of one or two pins. One author has seen several proximal transverse tibial fractures in older cats with concurrent chronic patellar fractures.
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Box 39-2. Stabilization of a simple transverse fracture of the proximal tibial metaphysis A medial approach to the proximal metaphysis is performed. The approach is extended proximally, parallel to the patellar tendon if an intramedullary pin is inserted. Intramedullary pin and type I external skeletal fixator: This repair is preferred in young cats. A 1.4–1.6-mm intramedullary pin is inserted in a normograde manner. For the medially applied external skeletal fixator, 1.4–2.0-mm transosseous pins are driven into the proximal fragment, and 1.4–1.6-mm pins are used in the distal tibial shaft (Fig. 39-5a). Smooth pins should be angled 70° to the long axis of the bone to enhance pull-out resistance. A cranial tension band wire as described in Figure 39-5b can also be applied. Plate and tension band repair: This repair is preferred in older cats. A 2.0-mm T-plate or dynamic compression plate in compression function can be used if the proximal fragment allows insertion of three screws. The plate is applied at the caudomedial edge of the tibia in order to benefit from the increased bone purchase. A 0.6–0.8-mm figure-of-eight wire is positioned across the cranial fracture line as a tension band (Fig. 39-5b). A 2.0-mm internal fixator is a good alternative if only two screws can be inserted into the proximal fragment.
A
B
A
B
Figure 39-5 Options for stabilization of a simple transverse fracture of the proximal tibial metaphysis. (A) Repair of a simple proximal transverse fracture with an intramedullary pin and a medial type I external skeletal fixator. (B) Stabilization of a simple proximal transverse fracture using a sixhole plate and a cranial tension band wire.
C
D
Figure 39-6 (A, B) Preoperative and (C, D) postoperative radiographs of a 2-year-old cat with a proximal metaphyseal tibial fracture. Use of a 2.0mm T-plate allowed insertion of two screws into the proximal fragment.
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39: Tibia and fibula These fractures showed remodeling of the cranial cortex of the tibia, and are thought to be stress fractures related to decreased flexion in the stifle joint, resulting in the bending force in the hindlimb being transferred to the proximal tibia. Fractures will often occur bilaterally several months apart, and most cats have a history of other non-traumatic fractures of the acetabulum, ischium, or humeral condyle. An underlying bone abnormality is suspected but unproven. The tibial fractures in these cats seem to heal best when repaired with a pin and tension band, or plate and screw and tension band technique.
39.4 Diaphyseal fractures of the tibia and fibula Fracture healing of diaphyseal tibial fractures tends to be slow, probably caused by the lack of surrounding soft tissue and the sparse blood supply. Careful tissue handling, preservation of blood supply, and respecting the principles of osteosynthesis are crucial for success. The choice of treatment for diaphyseal tibia and fibula fractures is mainly based on fracture severity and location, age, body weight, temperament of the patient, and implants available (Chapters 13 and 24). The various implant systems have their own advantages and disadvantages. Closed reduction and external skeletal fixation of severe tibial fractures seem to reduce the incidence of osteomyelitis, when compared to open reduction and internal fixation methods (4). It is therefore often the method of choice for severely comminuted and open fractures. Plate osteosynthesis has the advantage of easier postoperative management compared to external skeletal fixation, making it more suitable for cats that are difficult to handle. On the other hand, plate osteosynthesis causes more iatrogenic damage to the sparse blood supply, and tibial fractures stabilized with bone plates had the longest healing times in two studies (2, 4).
39.4.1 Approach to the tibial diaphysis The tibial diaphysis is approached via a medial skin incision. The saphenous vein is spared. It can be gently dissected free and retracted with a Penrose drain.
39.4.2 Simple transverse and short oblique fractures Simple transverse and short oblique fractures may be treated with a cast after reduction. Tibial fractures with an intact fibula are also amenable to be treated with external coaptation because the fibula acts as an internal splint. The disadvantage of external coaptation is the prolonged immobilization of adjacent joints, which can cause cartilage degeneration, periarticular fibrosis, and muscle contractures. Therefore,
only fractures expected to have achieved clinical union within 4 weeks should be treated with external coaptation. Incomplete and undisplaced fractures in very young kittens may be treated with a splinted bandage. For complete fractures and fractures in older cats a full cast provides more stability. Application and maintenance of bandages and casts are described in Chapter 22. It is important to immobilize the tarsus in a flexed position to prevent contracture of the gastrocnemius muscle. Contraction of the gastrocnemius muscle can occur within days in immature cats. Internal stabilization or external skeletal fixation results in faster return to function and allows immediate weightbearing and motion of adjacent joints. Simple fractures of both the tibia and fibula in adult cats are therefore usually treated surgically. A type I external skeletal fixator, with or without intramedullary pin, a medially applied 2.7- or 2.0mm DCP in compression function, a single 2.0/2.7-mm VCP, or a 2.4-mm LC-DCP are all implants that could be used (Box 39-3). Open fractures are treated with external skeletal fixation.
39.4.3 Long oblique and multifragmentary reducible fractures Simple long oblique or reducible multifragment fractures of the tibia are not very common. They are usually treated with anatomic reduction and stable internal fixation. Anatomic fracture reduction enhances fixation stability by creating load sharing of the cortex, but has the disadvantage of causing soft-tissue trauma and bone devascularization. It should only be attempted in long oblique fractures, and fractures with one large reducible butterfly fragment. If it seems questionable from preoperative radiographs that anatomic reduction is possible, the fracture is treated as a comminuted fracture (section below). Intramedullary pinning and cerclage wires, and interfragmentary lag screws with a neutralization plate, are treatment options for anatomic reduction of long oblique fractures. Stabilization with a lag screw and a neutralization plate is preferred over fixation with an intramedullary pin and cerclage wires in the tibia (Fig. 39-8 and Box 39-4). Application of cerclage wires around the tibia requires additional softtissue dissection between the tibia and fibula, and has the potential for further diminution of the blood supply. Long oblique fractures can also be stabilized with an intramedullary pin and external skeletal fixator (Box 39-4). The intramedullary pin enhances bending stability, and the external skeletal fixation pins prevent axial collapse and rotation. This type of fixation does not provide interfragmentary compression, but fracture healing should be faster because of preservation of local blood supply. Open fractures are also treated with external skeletal fixation.
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Box 39-3. Stabilization of a simple transverse or short oblique fracture of the tibial diaphysis Simple fractures treated with intramedullary pin and external skeletal fixator can be reduced and stabilized in a closed manner. A medial approach to the tibial shaft is performed for plate osteosynthesis. The fracture is anatomically reduced. Intramedullary pin and type I external skeletal fixator: This combination is commonly used to treat simple fractures of the tibia in young cats. An intramedullary pin is inserted in a normograde manner to align the fracture fragments. Two transosseous pins are then placed in each fracture fragment to provide rotational stability (Fig. 397a). Usually, 1.4–2.0-mm pins are used in the proximal tibia, and 1.4–1.6-mm pins in the distal tibia. Plate osteosynthesis: The plate is applied to the medial tibial surface. Interfragmentary compression is exerted if a dynamic compression plate (DCP) or limited contact-DCP (LC-DCP) is used. One screw on each side of the fracture is applied eccentrically for interfragmentary compression. Overall, at least three screws are required per fragment. It is advisable to select a longer plate and leave some holes empty, rather than taking a short plate and filling all holes (Fig. 39-7b). Care must be taken not to leave a single empty plate hole at the level of the fracture.
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Figure 39-7 Options for stabilization of simple transverse or short oblique fractures of the tibial diaphysis. (A) Repair of a transverse diaphyseal tibial fracture with an intramedullary pin and a type I external skeletal fixator. (B) Internal fixation of a short oblique tibial fracture with a medially applied plate. Anatomic reduction is important.
Spiral fractures of the tibia with an intact fibula can be successfully treated with external coaptation in immature cats (12). External coaptation for long oblique fractures is not recommended in adult cats.
39.4.4 Comminuted fractures
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Figure 39-8 A 10-month-old cat with a long oblique fracture of the tibia. (A) Preoperative radiograph showing a long oblique fracture of the distal tibial shaft. (B) The fracture was stabilized with a 2.0-mm lag screw and a 1.5/2.0mm veterinary cuttable plate in neutralization function. This relatively weak and short plate could be used because the fibula was intact. (C) The fracture was healed after 5 weeks.
Comminuted and open fractures of the tibia are common. Open fractures are commonly located in the distal diaphysis. Closed, mildly comminuted fractures can be treated with a plate in buttress function, if the main fragments allow insertion of a sufficient number of screws. Internal fixators can also be used as buttress implants, and have the advantage of preserving cortical blood supply and requiring only two screws per fragment (Fig. 39-10). External skeletal fixation is the treatment of choice for open fractures and is also commonly used to stabilize comminuted fractures. A type I or II external skeletal fixator is used depending on fracture location and severity. A type I external skeletal fixator with three transosseous pins per fragment is adequate for mild to moderate comminuted fractures in younger cats. Healing can take several months in severely comminuted and open tibia fractures (4) (Fig. 39-11), and
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Box 39-4. Stabilization of long oblique or reducible butterfly fractures of the tibial diaphysis A medial approach to the tibial shaft is performed if anatomic fracture reduction and interfragmentary compression are planned. Closed reduction or a minimally invasive approach can be used for external skeletal fixation. Lag screws and neutralization plate: The fracture is anatomically reduced and reduction is maintained with pointed reduction forceps. One or two 2.0-mm lag screws are inserted perpendicular to the fracture line(s). A long plate is then applied in neutralization function (Fig. 39-9a). At least three screws should be inserted proximal and distal to the limit of the fracture. If fracture configuration allows, the lag screws can also be inserted directly through the plate. Intramedullary pin and external skeletal fixator: An intramedullary pin is inserted normograde. The fracture can be held in reduction with pointed reduction forceps while transosseous pins are inserted. Two to three transosseus pins are inserted per fragment (Fig. 39-9b). Size 2.0mm pins are usually used in the proximal metaphysis, and 1.4–1.6-mm pins in the diaphysis and distal metaphysis.
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Figure 39-9 Options for stabilization of long oblique fractures, or reducible fractures with a butterfly fragment, of the tibial diaphysis. (A) Stabilization of a tibial fracture with a butterfly fragment with lag screws and a neutralization plate. (B) Repair of a long oblique fracture in the tibial shaft with an intramedullary pin and a type I external skeletal fixator.
Figure 39-10 (A) Preoperative, (B) postoperative, and (C) 1-year follow-up radiographs of a cat with a comminuted fracture of the distal shaft of the tibia, stabilized with an internal fixator (2.4-mm Unilock plate). Note the small gap between plate and bone, and that only two screws were inserted in the small distal fragment.
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Figure 39-11 Delayed healing of a comminuted fracture of the tibia. (A, B) Preoperative radiographs show a highly comminuted fracture. (C, D) Radiographs taken 3 months after closed reduction and stabilization with a type II external skeletal fixator. The most proximal pin is broken, there is a non-union of the most proximal part of the fracture, and the proximal fragment is tilted cranially. (E, F) Radiographs taken another 3 months after replacement of proximal pins, insertion of a cancellous bone graft, and application of a tension band to pull the proximal fragment distally and caudally. Callus formation is now evident. (G, H) Radiographs after 11 months finally show healing. The type I external skeletal fixator was left in place for another month.
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Box 39-5. Stabilization of comminuted fractures of the tibial diaphysis Closed reduction can be used to apply an external skeletal fixator. A surgical approach is usually performed for plating, but care is taken to disturb the soft-tissue attachments of the fragments and local blood supply minimally. The least invasive approach to apply a plate is the minimally invasive plate osteosynthesis (MIPO) technique. Bone grafting is indicated if large fracture gaps or devitalized fracture fragments are present. External skeletal fixation: Type I and II external fixators are mostly used with 2.0-mm transosseous pins proximally, and 1.6-mm pins distally. The most proximal and most distal positive-threaded transosseous pins are inserted first, parallel to the stifle and tarsal joint. These pins are end-threaded for a type I fixator (Fig. 39-12a), and centrally threaded for a type II fixator (Fig. 39-12b). The fracture is reduced indirectly by bringing the two pins parallel to each other, and connecting them with the external bar. This relies on accurate pin positioning, and overall alignment should also be checked by flexing and extending the hock and stifle to ensure that they are bending in the same plane. Care is taken to avoid valgus, outward rotation, craniocaudal malalignment, and overdistraction of
the main fragments. Two additional positive end-threaded or smooth pins are then added from medial per main fragment as half pins. Buttress plate: A 2.7-mm dynamic compression plate (DCP), a 2.4-mm limited contact-DCP (LC-DCP) or a stacked 2.0/2.7-mm veterinary cuttable plate can be used. The plate should span the whole length of the tibia, and should allow insertion of at least three screws proximally and distally (Fig. 39-12c). Minimal plate contouring is necessary. The plate is fixed to the proximal fragment first. Then reduction is achieved by securing the distal fragment to the plate. The intervening fracture fragments are not manipulated. An intramedullary pin can give additional bending stability, especially if the proximal or distal fragments are too short to allow insertion of three screws. The intramedullary pin is inserted prior to plate application, and helps in obtaining alignment. The disadvantage is that it may be difficult to pass the screws in the narrow distal diaphysis. Internal fixator: An internal fixator, for example the 2.4-mm Unilock plate, can be applied in buttress function, as shown in the radiographs of Figure 39-10. Figure 39-12 Options for stabilization of comminuted fractures of the tibial shaft. (A) Stabilization of a mildly comminuted mid diaphyseal fracture with a type I external skeletal fixator. Three transosseous pins are inserted per fragment. (B) Repair of a severely comminuted fracture of the tibia with a type II external skeletal fixator. At least two pins should be inserted per fragment. (C) Internal fixation of a comminuted fracture using a buttress plate.
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pin loosening is likely to occur during such long healing times if simple frames are used. Severely comminuted fractures, especially in older cats, are therefore best stabilized with a type II configuration. A type II or even type III configuration is also used if a small proximal or distal metaphyseal segment
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only allows insertion of the minimum number of pins from two sides or planes (Box 39-5). An interlocking nail is another treatment option for comminuted fractures in the proximal or mid diaphyseal area in larger cats. The tibia and its intramedullary canal
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Distal fractures of the tibia and fibula include metaphyseal fractures in adult cats, Salter and Harris fractures in growing cats, and tarsal joint fractures. Lateral and medial malleolar fractures are common distal tibial and fibular fractures, and are associated with tarsal instability.
fragment can make it difficult to insert a sufficient number of screws or transosseous pins. External skeletal fixators can often be used after closed reduction. The tubular external skeletal fixator is especially suitable for distal metaphyseal fractures because it allows insertion of a larger number of transosseous pins over a small distance than other external skeletal fixator systems (14) (Chapter 24). A hybrid construct with a circular external skeletal fixator (15, 16) (Fig. 39-13) or a fixator with an acrylic bar also allows fixation of very small fragments, and is useful for distally located fractures. The small distal fragment does not usually allow insertion of a sufficient number of screws with a 2.7-mm DCP. A 2.0mm thick DCP or a 2.0/2.7 or 1.5/2.0 VCP are therefore used. To compensate for the lower stability of these shorter and weaker plates, an intramedullary pin can be inserted prior to plate application if there is concern about construct stability. The cuttable plate can be used in sandwich function to enhance bending stability. Internal fixators can also be used in fractures close to joints where it is only possible to insert two screws per fragment (Box 39-6).
39.5.1 Approaches to the distal tibia and fibula
39.5.3 Salter and Harris fractures
A medial approach is used to access the distal tibial diaphysis and the medial malleolus. The fibula is approached from laterally.
The distal physis of the tibia closes between 40 and 52 weeks of age in intact cats (11). Fractures of the distal tibia are usually Salter and Harris type I or II fractures (Fig. 39-15). Salter and Harris type III fractures have also been reported (17). Salter and Harris type I and II fractures are best stabilized with cross pins (Box 39-7). Conservative treatment with a cast is an option in undisplaced Salter and Harris type I or II fractures, particularly in young kittens. Cats younger than 6 or 7 months with further growth potential are at risk of development of growth disturbances if premature physeal closure occurs.
narrow distally, so with the current range of interlocking nail sizes, the nail can only be used in large cats with fractures involving the mid to proximal third diaphysis (7). Fractures with devitalized fracture fragments and fractures with large fracture gaps are at risk of developing non-union and should be grafted. Excessive distraction of the main fragments creating large fracture gaps should be avoided during external skeletal fixation repair. Cancellous bone grafting has been shown to be capable of preventing non-unions of the tibia in the presence of large fracture gaps (13). Autogenous or allogenous cancellous bone graft, or a combination of the two, can be used. Open fractures may require delay of the grafting until the wound is considered to be free of infection.
39.5 Fractures of the distal tibia and fibula
39.5.2 Metaphyseal fractures of the distal tibia Distal metaphyseal tibial fractures occur commonly in cats, and the incidence of open fractures is relatively high. Closed fractures can be stabilized with plate osteosynthesis or external skeletal fixation. The treatment of choice for open fractures is an external skeletal fixator. The small size of the distal
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Box 39-6. Stabilization of metaphyseal fractures of the distal tibia Although closed reduction is possible with external skeletal fixation, a small medial approach to the distal fragment is often performed for ease of pin positioning. A medial approach is also used for plate application. Tubular external skeletal fixator: The distal transosseous pin is inserted first, close to and perpendicular to the tarsal joint. A 1.6-mm, or maximally a 2.0 positive endthreaded pin, is used. The direction of this first pin is critical, as it will determine the position of the connecting tube, perpendicular to the pin. A 6.0-mm tube is secured to the pin. The fracture is reduced and a transosseous pin is inserted into the proximal fragment. If the distal pin is placed correctly, the tube will be positioned parallel to the long axis of the tibia. At least three pins are inserted into the proximal fragment, and at least two or three are inserted into the distal fragment (Fig. 39-14a). If an intramedullary pin is also used it is inserted prior to application of the fixator. Intramedullary pin and plate: An intramedullary pin, comprising approximately 30% of the diameter of the distal medullary canal, is inserted in a normograde fashion. A long 2.0-mm dynamic compression plate or a 1.5/2.0 veterinary cuttable plate (VCP) is then applied in neutralization or buttress function. If used in buttress function, consider stacking or sandwiching the VCP. Screws must engage at least four cortices in the distal and proximal fragment (Fig. 39-14b), but six or even eight cortices are preferred, especially in the proximal bone.
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Internal fixator: A 2.0-mm locking plate can be used as a neutralization or buttress implant, with two screws in the distal fragment, and three in the proximal fragment.
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Figure 39-14 Stabilization options for distal metaphyseal fractures of the tibia. (A) Repair of a simple transverse fracture with a 6.0-mm tubular external skeletal fixator. (B) Internal fixation of an oblique fracture with an intramedullary pin and a 12-hole 2.0-mm dynamic compression plate.
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Figure 39-15 (A, B) A 5-month-old cat with a Salter and Harris type I fracture of the distal tibia, and a fracture of the distal fibula. (C, D) Postoperative radiographs show reduction and stabilization with two Kirschner wires inserted as cross pins.
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Box 39-7. Stabilization of Salter and Harris type I and II fractures of the distal tibia An approach to the distal tibia and medial malleolus is performed. The fracture is carefully reduced, using distal traction on the flexed tarsus and manipulation of the foot and careful levering with a freer periosteal elevator. Anatomic reduction is mandatory for fixation stability. A 0.9–1.2-mm Kirschner wire is driven from the medial malleolus in a proximolateral direction to be seated in the lateral cortex of the distal tibia. Care has to be taken not to enter the tibiotarsal joint. A second Kirschner wire is then inserted from the distal fibula across the tibia, exiting through the medial cortex (Fig. 39-16). A separate lateral skin incision is required for pin placement. It is important that both pins are securely engaged in the distal tibial fragment. If one or both pins are inserted subperiostally, loss of reduction and instability may occur. Figure 39-16 Cross pinning of a Salter and Harris type II fracture of the distal tibia with one pin inserted from the medial malleolus, and one from the lateral malleolus.
39.5.4 Fractures of the distal tibia involving the tarsal joint Epiphyseal fractures include malleolar fractures, cranial slab fractures, and complex articular fractures. Fractures of the lateral or medial malleolus are the most common type of distal tibia and fibula fractures. The malleoli serve as a medial and lateral restraint to the talus, and they are the insertion sites for the tarsal collateral ligaments. Malleolar fractures result in talocrural instability, and are covered in Chapter 40. Cranial slab fractures of the distal tibia are encountered occasionally in cats. These fractures cause tarsal instability,
because the dorsal rim of the tibia is part of the insertion of the joint capsule. If the fragment is large enough, it is stabilized with a small lag screw or a small threaded pin to restore congruity of the joint surface and joint stability. If the fragment is too small to be reattached, it is probably best removed, followed by external immobilization of the tarsus for 2–3 weeks in order to allow healing of the insertion of the joint capsule. Fortunately, complex fractures of the epiphysis of the tibia are rare, but they may occur after falls and gunshot wounds. If comminution precludes anatomic and stable repair of the tibiotalar joint surface, pantarsal arthrodesis is the only treatment option (Chapter 40).
39.6 Postoperative treatment and prognosis External coaptation is usually not necessary after stable fixation of metaphyseal and diaphyseal fractures. Follow-up radiographs are generally performed after 4–6 weeks. Fractures of the tibial diaphysis are more prone to develop complications than fractures of other bones, possibly due to the high incidence of comminuted and open fractures, and the poor soft-tissue covering. Both fracture-healing disorders and osteomyelitis can occur. Fracture healing is slower for comminuted and high-grade open fractures (4), and some severely comminuted fractures may take several months to heal. The tibia has been reported to be predisposed to non-unions, with an incidence of approximately 15% (18). Non-unions are most likely to develop after comminuted fractures and open fractures, in older and overweight cats (18). Osteomyelitis occurs in up to 15% of tibial diaphyseal fractures (2, 4). Predisposing factors include wound contamination or infection in the presence of open fractures, and poor vascularity caused by soft-tissue trauma. Proximal and distal physeal fractures are expected to heal rapidly, but a splinted bandage should be applied for approximately 2 weeks to protect the repair. Radiographs are performed after 2–3 weeks to detect premature physeal closure, and to evaluate fixation stability. The Kirschner wire ends may cause irritation of periarticular structures, and should be removed in the presence of local swelling, seroma formation, or radiographic evidence of implant migration. Prognosis after distal tibial fractures depends mainly on the ability to achieve anatomic reduction of the fragments and a stable fracture repair. Malalignment or instability will cause dysfunction and degenerative joint disease of the tibiotarsal joint. One study reported a suboptimal outcome in 18% of distal physeal fractures, perceptible as continued lameness, malunion, and reduced range of motion of the tarsal joint (3).
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References and further reading 1. Hill FWG. A survey of bone fractures in the cat. J Small Anim Pract 1977;18:457–463. 2. Boone EG, et al. Fractures of the tibial diaphysis in dogs and cats. J Am Vet Med Assoc 1986;188:41–45. 3. Brunnberg L. Tibia and fibular fractures in the cat. Kleintierpraxis 2003;48:9–23. 4. Richardson EF, Thacher CW. Tibial fractures in cats. Compend Continuing Educ 1993;15:383–394. 5. Whitney WO, Mehlhaff CJ. High-rise syndrome in cats. J Am Vet Med Assoc 1987;191:1399–1403. 6. Payne J, et al. Comparison of normograde and retrograde intramedullary pinning of feline tibias. J Am Anim Hosp Assoc 2005;41:56–60. 7. Duhautois B. Use of veterinary interlocking nails for diaphyseal fractures in dogs and cats: 121 cases. Vet Surg 2003;32:8–20. 8. Fruchter AM, Holmberg DL. Mechanical analysis of veterinary cuttable plate. Compend Continuing Educ 1991;4:116–119. 9. Schmökel HG, et al. Percutaneous plating of tibial fractures in two dogs. Vet Comp Orthop Traumatol 2003;16:191–195. 10. Piermattei DL, Johnson KA. An atlas of surgical approaches to the bones and joints of the dog and the cat, 4th edn. Philadelphia: WB Saunders; 2004.
505 11. Smith RN. Fusion of ossification centres in the cat. J Small Anim Pract 1969;10:523–530. 12. Zaal MD, Hazewinkel HAW. Treatment of isolated tibial fractures in cats and dogs. Vet Q 1997;119:191–194. 13. Toombs JP, Wallace LJ. Evaluation of autogeneic and allogeneic cortical chip grafting in a feline tibial nonunion model. Am J Vet Res 1985;46:519–528. 14. Haas B, et al. Use of the tubular external fixator in the treatment of distal radial and ulnar fractures in small dogs and cats. Vet Comp Orthop Traumatol 2003;16:132–137. 15. Farese JP, et al. Use of IMEX SK-circular external fixator hybrid constructs for fracture stabilization in dogs and cats. J Am Anim Hosp Assoc 2002;38:279–289. 16. Clarke SP, Carmichael S. Treatment of distal diaphyseal fractures using hybrid external skeletal fixation in three dogs. J Small Anim Pract 2006;47:98–103. 17. Boone EG, et al. Distal tibial fractures in dogs and cats. J Am Vet Med Assoc 1986;188:36–40. 18. Nolte DM, et al. Incidence of and predisposing factors for nonunion of fractures involving the appendicular skeleton in cats: 18 cases (1998–2002). J Am Vet Med Assoc 2005;226:77–82.