Treatment of Growth Deformities with External Skeletal Fixation

EXTERNAL SKELETAL FIXATION

0195-5616/92 $0.00

+ .20

TREATMENT OF GROWTH DEFORMITIES WITH EXTERNAL SKELETAL FIXATION Ann L. Johnson, DVM, MS

Deformities of the limbs in the growing animal are usually caused by damage to the physis, which results in premature cessation of long bone growth.2, 3, 4, 7, 10, 14, 15,19,24 Complete premature closure of the physis in a single bone leads to shortening of the bone. Complete premature closure of the physis in a paired bone system, such as the radius and ulna, causes shortening of the affected bone and may contribute to shortening, angular, and rotational deformity of the paired bone. Partial premature closure of a physis also causes shortening and angular deformity of the bone. Any deviation from normal anatomy of a long bone may cause degenerative changes in the adjacent joints. The severity of the deformity is directly proportional to the growth potential of the animal at the time of physeal injury. The most common angular bone deformities are a result of premature closure of the distal ulnar physis and distal radial physis. 4, 7, 14, 15, 18, 24 Deformities of the rear limb after injury to the femoral or tibial physes are seen less frequently.7, 19 Treatment of growth deformities is directed toward removing the impediment to growth of the normal physis or portions of the physis in the immature animal and corrective osteotomy in the mature animal.4, 7, 12, ]3, 16, 21, 23 Corrective osteotomy involves creating a fracture of the affected long bone, correcting the deformity, and stabilizing the bone in the proper position to allow fracture healing. External skeletal fixation (ESF) is an excellent method for rigid stabilization of an osteotomy, especially of the radius and ulna or tibia. This article describes the From the Department of Veterinary Clinical Medicine, University of Illinois College of Veterinary Medicine, Urbana, Illinois

VETERINARY CLINICS OF NORTH AMERICA: SMALL ANIMAL PRACTICE VOLUME 22· NUMBER 1 • JANUARY 1992

209

210

JOHNSON

pathophysiology of several common growth deformities and the use of corrective osteotomy stabilized with ESF for treatment of these deformities. CORRECTIVE OSTEOTOMY

Corrective osteotomies are performed -for one or several of the following reasons: (1) correct limb angulation, (2) realign joint surfaces, (3) increase limb or bone length, (4) correct rotational deformity, and (5) improve articular configuration. The objective of a corrective osteotomy is to return the limb to near normal function. In the process, limb cosmetics are improved and development of osteoarthritis diminished or halted. In the mature dog, growth deformities of the radius and ulna and tibia can be treated by corrective osteotomy because of bone shortening, angular and rotational deformities, or joint incongruence. 7 It is important for the proximal radial or tibial joint surface to be parallel to the distal radial or tibial joint surface for normal weight bearing and maintenance of articular cartilage health. It is also important to reestablish articular contact in cases of luxation of the elbow to stop the development of osteoarthritis and increase limb function. 7, 11, 23 A corrective osteotomy is similar to a fracture in that it must be stabilized to allow healing of the fracture site. In addition, the treated bone must be repositioned correctly to achieve the objectives of the procedure. ESF is excellent for stabilization of corrective osteotomies of the radius and ulna or the tibia. Bilateral frames can be constructed to give rigid fixation to the fracture site and allow postoperative weight bearing on the limb (Fig. 1). In addition, the transfixation pins can serve as guide pins for realigning the bone. The ESF frame can be manipulated after surgery to correct any residual mal alignment of the bone or joint. Finally the fixation is easily removed after healing of the osteotomy. The disadvantages of ESF include the aftercare for fixation pins and the effects of the fixation pins on the adjacent soft tissues. GROWTH DEFORMITIES OF THE RADIUS AND ULNA

The most common growth deformities diagnosed in small animals and treated with corrective osteotomy are caused by premature closure of the distal ulnar or distal radial physis. The radius and ulna are paired bones whose growth must be synchroriized for the correct development of the long bones and adjacent joints. The distal ulnar physis is responsible for 85% of the length of the ulna, the distal radial physis is responsible for 60% of the length of the radius, and the proximal radial physis is responsible for 40% of the length of the radius. 7, 21 Growth rate varies with the breed of dog. Large-breed dogs tend to mature at a slower rate than small-breed dogs. In most dogs, there is a growth spurt from 5 to 7 months of age, and growth tapers off during the ninth to tenth month of age.

TREATMENT OF GROWTH DEFORMITIES

211

Figure 1. Stability achieved with bilateral external skeletal fixation allows postoperative weight-bearing on the limb.

The canine distal ulnar physis is susceptible to injury to the growing cells because of its cone shape, which predisposes the cells to crushing when a force is directed across the physis. I, 7, 22 Closure of the distal ulnar physis results in shortening of the ulna and shortening, cranial bowing, valgus angulation, and external rotation of the radius (see Fig. 2). The severity of the deformity depends on the growth potential of the animal when the initial injury occurs. Incongruent growth of the radius and ulna affects the anatomy of the elbow and the carpus leading to degenerative joint disease. I, 7,14,15,20,21 Injuries also occur to the distal and proximal physes of the radius. Again the sequelae to the premature closure of the physis are exacerbated because of the paired bone anatomy. Symmetrical closure of the distal or proximal physis results in shortening of the radius with separation of the humeroradial joint. 11, 23 This elbow dislocation is the primary cause of lameness. The ulna may also be shortened; there is little angular or rotational deformity, however (Fig. 2).17 Asymmetrical closure of the distal radial physis results in shortening and angular deformity of the radius (Fig. 2). The direction of the angulation depends on the portion of the physis that is initially affected. 23 The angulation of the radius also causes incongruence of the carpus and development of degenerative joint disease. 23 , Treatment of premature closure of the radial or ulnar physis in the immature dog is aimed at removing the restraint to normal growth of the unaffected physis or portion of the physis. This is done with

212

JOHNSON

/

A

B

I

c

Figure 2. Deformities associated with premature closiJre of the physes of the radius and ulna. A, Premature closure of the distal iJlriar physis results in shortening of the ulna and shortening, cranial bowing, valgus angulation, and. external rotation of the radius. B, Asymmetric closure of the distal radial physis results in angular deformity of the radius. C, Symmetric premature closure of the distal radial physis results in shortening of the radius and luxation of the humeroradial joint. (From Johnson AL: Correction of radial and ulnar growth deformities resulting from premature physeal closure. In Bojrab MJ (ed): Current Techniques in Small Animal Surgery, ed. 3. Philadelphia, Lea & Febiger, 1990, p 795; with permission.)

ostecWmies of the affected bone or portion of the physis and filling the defects with free autogenous fat grafts to prevent bone union. 4, 7 Treatment of the mature dog is corrective osteotomy of the radius and ulna to realign the joints and prevent further development of osteoarthritis.4, 7, 12 PREMATURE CLOSURE OF THE DISTAL ULNAR PHYSIS

Premature closure of the distal ulnar physis, causing shortening of the ulna and shortening, cranial bowing, valgus angulation, and exter-

TREATMENT OF GROWTH DEFORMITIES

213

nal rotation of the radius, is an indication for corrective osteotomy in the mature animal. An oblique osteotomy of the radius with a release osteotomy of the ulna will allow the surgeon to correct the angulation and rotation of the radius in three dimensions while preserving or increasing bone length. 7, 21 Stabilization of the radial osteotomy is achieved with bilateral or type II ESF. Diagnosis of the deformity is made with physical examination and confirmed with radiographic examination of the affected limb. Radiographs are also obtained of the contralateral radius and ulna to establish the normal anatomy for each animal. The radiographs of the affected radius and ulna are evaluated to determine the point of greatest curvature of the radius, which will be the osteotomy site. The prognosis for the outcome of corrective osteotomy varies with the severity of the deformity. The prognosis is good for improved function and appearance of the limb. The owner is warned, however, that the surgery may not return the dog to a normal condition. 4 The affected limb and an appropriate site for harvesting cancellous bone grafts are prepared for aseptic surgery. The proximal humerus of the affected limb is convenient and usually chosen for the graft site. The proximal transfixation pin is driven from the lateral surface of the proximal radial metaphysis and exits the medial side of the limb. The pin is positioned parallel to the proximal radial articular surface and in the lateral transverse plane of the proximal radius. The distal transfixatiort pin is placed parallel to the distal radial articular surface and in the lateral transverse plane of the distal radial metaphysis. The pins will not be parallel to each other if external rotation exists (Fig. 3). The lateral surface of the distal ulna is surgically approached and an osteotomy of the ulna performed. An incision is made on the cranial medial portion of the limb over the area of greatest curvature of the radius. The subcuticular tissues are separated to expose the radius. An oblique osteotomy line is identified parallel to the distal radial articular surface . An osteotomy is made with an osteotome and mallet or an oscillating bone saw cooled with a saline flush. The distal radius is aligned using the transfixation pins as a guide to determine when the proximal and distal joint surfaces are parallel, correcting the angular deformity, and when the lateral surfaces of the radius are aligned, correcting the rotational deformity. If possible, the distal point of the proximal .radial segment is inserted into the medullary canal of the distal radial segment to increase the stability of the osteotomy site. Connecting bars are placed on the transfixation pins on the medial and lateral sides of the limb. At least two additional single pin-grippers are placed on the lateral bar. A second pin is placed through the pingripper into the proximal segment of the radius. The pin is placed at 45 degrees to the long axis of the radius and driven toward the proximal transfixation pin, completely penetrating the medial cortex. The procedure is repeated for the distal segment. The reduction of the osteotomy is verified and the pin-grippers tightened (Fig. 3). Additional fixation pins can be added if necessary. An autogenous cancellous bone

214

JOHNSON

Figure 3. A and B. Placement of transfixation pins and location of the oblique osteotomy for correction of shortening and angular and rotational deformities of the radius. Illustration continued on opposite page

graft is harvested from the proximal humerus and placed at the osteotomy site. The subcutaneous tissues and the skin are sutured. 7 Radiographs of the radius and ulna made after surgery are evaluated to determine if the joint surfaces appear parallel in both the lateral and the cranial caudal views. Some correction can be made by loosening the pin-grippers and repositioning the distal radial segment. Care of the limb after surgery includes daily hydrotherapy to clean the area around the fixation pins, monthly radiographic evaluation to determine healing of the osteotomy site and stability of the fixation device, and exercise limitations until there is radiographic evidence of bone union. When the osteotomy has healed, the fixation device is removed. Fixation pins may be loose and easily removed without sedation of the animal or in some cases tranquilization will be required. Most corrective osteotomies are done in young animals, and the healing rate is rapid, resulting in a healed osteotomy site 6 to 8 weeks after surgery.

TREA lMENT OF GROWTH DEFORMITIES

215

o Figure 3 (Continued). C and D, Alignment of the proximal and distal radial joint surfaces and placement of the bilateral on Type II external fixation frame. (From Johnson AL: Correction of radial and ulnar growth deformities resulting from premature physeal closure. In Bojrab MJ (ed): Current Techniques in Small Animal Surgery, ed. 3. Philadelphia, Lea & Febiger, 1990; with permission.)

PREMATURE CLOSURE OF THE DISTAL OR PROXIMAL RADIAL PHYSIS

Symmetrical premature closure of the proximal or distal radial physis, causing shortening of the radius and luxation of the humeroradial joint (Fig. 4), is an indication for a lengthening osteotomy of the radius to reestablish articular congruency. A transverse osteotomy of the radius is distracted until the radial head contacts the capitulum of the humerus and stabilized with bilateral or type II ESF. An animal with symmetrical premature closure of the proximal or distal radial physis presents with a straight limb or a slight varus deformity of the carpus. The animal · is lame and exhibits a painful

216

JOHNSON

Figure 4. Shortening and angular and rotational deformity of the radius after premature closure of the distal ulnar physis. A, Preoperative radiographs. B, Postoperative radiographs. Illustration continued on opposite page

response when the elbow is palpated. Radiographs of the radius and ulna reveal a shortened radius and luxation of the humeroradial joint (Fig. 5). A corrective osteotomy is indicated to lengthen the radius and restore elbow joint congruity, thereby preventing degenerative joint disease.3, 13, 16, 23 The affected limb and an appropriate site for harvesting cancellous bone graft are prepared for aseptic surgery. A transfixation pin is placed from the lateral side through the proximal radial metaphysis, exiting from the medial aspect of the limb. A second transfixation pin is placed in a similar manner in the distal radial metaphysis. An approach to the mid diaphysis of the radius is made. The radius is isolated, and a transverse middiaphyseal osteotomy is made with an osteotome and mallet or an oscillating bone saw cooled with a saline flush. The radial segments are distracted with an Inge laminectomy retractor until the

TREATMENT OF GROWTH DEFORMITIES

217

Figure 4 (Continued). C, Six weeks after surgery, showing a healed osteotomy site.

radial head contacts the capitulum of the humerus. The joint contact may be confirmed by approaching the lateral aspect of the elbow and visualizing the structures. 23 Alternatively postoperative radiographs followed by additional radial distraction with the external fixation pins may be used to seat the radial head correctly. Medial and lateral connecting bars are placed on the proximal and distal transfixation pins. Two additional single pin-grippers are placed on the lateral connecting bar. A second pin is driven through the pin-gripper into the proximal radial segment at a 45 degree angle to the long axis of the bone toward the proximal transfixation pin. The pin must completely penetrate the medial cortex. The procedure is repeated for the distal segment. Additional pin-grippers and pins may be placed in each segment of the radius in large dogs. Positioning of the radius is confirmed and the pin-grippers tightened. Autogenous cancellous bone is harvested and placed in the osteotomy gap (Fig. 6). The subcutaneous tissue and skin are sutured. 7 Postoperative radiographs are made to evaluate the position of the

218

JOHNSON

Figure 5. Symmetric premature closure of the distal radial physis resulting in shortening of the radius and luxation of the humeroradial joint. A, Preoperative radiographs. B, Postoperative radiographs showing continued luxation of the radial head. Illustration continued on opposite page

radial head. If the radial head does not contact the capitulum of the humerus, a transfixation pin is placed through the olecranon, proximally to the proximal transfixation pin in the radius. The pin-grippers in the proximal radial segment are loosened and the proximal radial transfixation pin linked to the ulnar transfixation pin with rubber bands placed on the medial and lateral side of the limb (Figs. 5 and 7). The limb is radiographed again in 24 to 48 hours after surgery. If the radial head has seated, the rubber bands and ulnar transfixation pin are removed and the pin-grippers tightened (Fig. 5). Additional time may be needed for seating the radial head. 11 Asymmetrical closure of the distal radial physis will cause angular deformity of the radius in addition to or instead of shortening, which causes humeroradial luxation. 23 Correction of the angular deformity is done by placing the distal transfixation pin parallel to the distal radial joint surface and positioning the proximal and distal transfixation pins parallel to each other after the osteotomy, as described for the oblique osteotomy of the radius. Postoperative care is the same as described for the oblique osteotomy.

TREATMENT OF GROWTH DEFORMITIES

219

Figure 5 (Continued). C, Seventy-two hours after corrective osteotomy of the radius and placement of a pin through the olecranon, connected with rubber bands to the proximal radial transfixation pin, showing a decrease in the humeroradial joint space. D, Four weeks after surgery, showing a healing osteotomy site and excellent reduction of the humeroradial joint.

PREMATURE CLOSURE OF THE DISTAL ULNAR AND RADIAL PHYSIS

Occasionally complete closure of both the distal ulnar and distal radial physis will occur in the immature dog. If the dog is very young with much growth potential, there will be severe limb length discrepancy when the dog matures. A distraction osteotomy of the radius and ulna is indicated to allow the affected limb to achieve the length of the contralateral limb. In addition, there may be rotational and angular deformities that must be corrected. A transverse or oblique osteotomy and ESF can be used to correct the angular and rotational deformities and distract the limb to achieve the correct length. The Charnley apparatus and the Stader apparatus have been used to distract bone segments following transverse. osteotomies as a treatment for premature physeal closure. In these cases, the bone segments were distracted two to three times a week with the goal being to keep up with the growth of the contralateral forelimb. 9 , 13 Continuous lengthening of a transverse osteotomy to allow mem-

220

JOHNSON

A Figure 6. Lengthening transverse osteotomy of the radius. A, Placement of transfixation pins and location of the transverse osteotomy. B, Distraction of the proximal radius and placement of the bilateral or Type II external fixation frame and an autogenous cancellous bone graft. (From Johnson AL: Correction of radial and ulnar growth deformities resulting from premature physeal closure. In Bojrab MJ (ed) : Current Techniques in Small Animal Surgery, ed. 3. Philadelphia, Lea & Febiger, 1990, p 801 ; with permission .)

branous bone formation can be done by distracting the segments at the rate of 1 mm per day. Distraction begins at 5 to 7 days following osteotomy or corticotomy and is done continuously in 0.25 mm increments every 6 hours or in 0.5 mm increments every 12 hours. This rate of elongation allows for optimal osteogenesis to occur at the osteotomy gap without final bone bridging until the distraction is discontinued. 6 A modification of the Kirschner ESF splint has been made by substituting threaded 3/16/1 rods purchased at a hardware store for the connecting bars of a bilateral frame. The appropriately sized nuts are added to the connecting bar and placed adjacent to the single pin-grippers on the side toward the osteotomy. These nuts are turned two or four times a day to equal a total of 1 mm distraction at the fracture site per day. This procedure is continued until the appropriate length is reached. The ESF remains in place until bone healing has occurred. 5

TREATMENT OF GROWTH DEFORMITIES

221

Figure 7. A, S, Bilateral application of rubber bands from the proximal radial transfixation pin to an olecranon transfixation pin to apply traction to the proximal radial segment and reestablish humeroradial joint surface contact.

GROWTH DEFORMITIES OF THE TIBIA

Growth deformities of the tibia occur following injury to the tibial physes. Complete closure of the distal tibial physis results in shortening of the bone, and the severity is indirectly proportional to the age of the animal when the injury occurred. Unless the limb length discrepancy is severe, most animals compensate by extending the stifle and hock joints to the affected limb. No treatment is necessary for these animals. Continuous distraction lengthening osteotomy is used if the limb length discrepancy causes functional problems. 6 Asymmetrical closure of the distal tibial physis results in angular limb deformity and is treated with an oblique osteotomy, as described earlier for angular deformities of the radius. Rotational deformities of the tibia rarely occur and can be treated by a derotational transverse osteotomy using the principles of preplacement of proximal and distal transfixation pins in the lateral transverse planes of the deformed tibia. The osteotomy is performed, the bone derotated to place the pins in the same transverse plane, and bilateral ESF constructed to stabilize the osteotomy. PES VARUS

Pes varus is a syndrome occurring in Dachshunds. The deformity is a varus angulation of the distal tibia caused by asymmetrical closure

222

JOHNSON

of the distal tibial physis. There does not appear to be any history of trauma in these animals. A genetic etiology has been suggested but not confirmed. Clinical signs appear at 5 to 6 months but may be ignored until chronic soft tissue and bone changes cause lameness. Surgical correction is recommended to prevent severe osteoarthritis of the tarsus. An open wedge corrective osteotomy is performed and stabilized with a bilateral or type II external fixator. A tran~fixation pin is placed in the proximal tibia parallel to the proximal articular surface. A second transfixation pin is placed in the distal tibia parallel to the distal articular surface. An oblique osteotomy is made parallel to the distal transfixation pin and distal articular surface through the metaphysis at the site of greatest curvature of the bone. The proximal and distal transfixation pins are aligned parallel to each other, correcting the varus deformity. A fixation pin is placed medially into the proximal segment of bone. Because the distal segment is small, a smaller pin is placed diagonally from the medial malleolus, across the fracture line and seated into the lateral cortex of the proximal segment. Autogenous cancellous bone graft is placed at the osteotomy site. The fixation pins are held in alignment with methyl methacrylate. When bone union has occurred, the fixation device is removed. 8 SUMMARY

Growth deformities of the long bones are usually caused by premature closure of the physis. The most commonly affected bones are the radius, ulna, and tibia. Premature closure of the physis can result in shortened, angular, and rotational bone deformities, especially when one bone of a paired bone system like the radius and ulna is affected. Adjacent joints may develop osteoarthritis. Corrective osteotomy to realign in joint surfaces is indicated in mature animals. Bilateral or type II external fixation frames are used to stabilize the osteotomies. The advantages of ESF are: (1) The transfixation pins can be used as guide pins to realign joints. (2) The fixation allows rigid stabilization of the osteotomy site. (3) Postoperative correction of alignment can be achieved. (4) Implant removal after bone union is simple. References 1. Carrig CS, Morgan JP, Pool RR: Effects of asynchronous growth of the radius and

2. 3. 4. 5.

ulna on the canine elbow joint following experimental retardation of the longitudinal growth of the ulna. J Am Anim Hosp Assoc 11:560-567, 1975 Carrig CS, Wortman JA: Acquired dysplasia of the canine radius and ulna. Comp Cont Ed Pract Vet 3:557-564, 1981 Clayton-Jones DG, Vaughan LC: Disturbance in the growth of the radius in dogs. J Small Anim Pract 11:453-468, 1970 Henney LHS, Gambardella PC: Premature closure of the ulnar physis in the dog: A retrospective study. J Am Anim Hosp Assoc 25:573:-581, 1989 Hulse DA: External fixation and distraction osteogenesis for treatment of premature

TREATMENT OF GROWTH DEFORMITIES

6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20.

21. 22. 23. 24.

223

closure of the radial and ulna physes. Presented at the Advanced Course for Internal Fixation of Fractures and Nonunions, Columbus, OH, 1989 I1izarov GA: Clinical application of the tension stress effect for limb lengthening. Clin Orthop Rei Res 250:8-26, 1990 Johnson AL: Correction of radial and ulnar growth deformities resulting from premature physeal closure. In Bojrab MJ, ed: Current Techniques in Small Animal Surgery, ed 3. Philadelphia, Lea & Febiger, 1990, pp 793--801 Johnson SG, Hulse DA, Van Gundy TE, et al: Corrective osteotomy of pes varus in the dachshund. Vet Surg 18:373-379, 1989 Knecht CD, Bloomberg MS: Distraction with an external fixation clamp (Charnley apparatus) to maintain length in premature physeal closure. JAm Anim Hosp Assoc 16:873-880, 1980 Llewellyn HR: Growth plate injuries-diagnosis, prognosis and treatment. J Am Anim Hosp Assoc 12:77-82, 1976 Mason TA, Baker MJ: The surgical management of elbow joint deformity associated with premature growth plate closure in dogs. J Small Anim Pract 19:639-645, 1978 Newton CD: Surgical management of distal ulnar physeal growth disturbances in dogs. J Am Vet Med Assoc 164:479-487, 1974 Newton CD, Nunamaker DM, Dickenson CR: Surgical management of radial physeal growth disturbances in dogs. J Am Vet Med Assoc 167:1011-1018, 1975 O'Brien TR: Developmental deformities due to arrested epiphyseal growth. Vet Clin North Am Small Anim Pract 1:441-454, 1971 O'Brien TR, Morgan JP, Suter PF: Epiphyseal plate injury in the dog: A radiographic study of growth disturbance in the forelimb. J Small Anim Pract 12:19-36, 1971 Olson NC, Brinker WO, Carrig CB, et al: Asynchronous growth of the canine radius and ulna: Surgical correction following experimental premature closure of the distal radial physis. Vet Surg 10:125-131, 1981 Olson NC, Carrig CB, Brinker WO: Asynchronous growth of the canine radius and ulna: Effects of retardation of longitudinal growth of the radius. Am J Vet Res 40:351355,1979 Ramadan RO, Vaughan LC: Premature closure of the distal ulnar growth plate in dogs-a review of 58 cases. J Small Anim Pract 19:647-667, 1978 Ramadan RO, Vaughan LC: Disturbance in growth of the tibia and femur in dogs. Vet Rec 104:433-435, 1979 Riser WH, Shirer JF: Normal and abnormal growth of the distal foreleg in large and giant dogs. J Am Vet Radiol Soc 6:50-64, 1965 Rudy RL: Corrective osteotomy of angular deformities. Vet Clin North Am Small Anim Pract 1:549-583, 1971 Skaggs S, DeAngelis MP, Rosen H: Deformities due to premature closure of the distal ulna in fourteen dogs: A radiographic evaluation. J Am Anim Hosp Assoc 9:496-500, 1973 VanDeWater AL, Olmstead ML: Premature closure of the distal radial physis: A review of 14 dogs. Vet Surg 12:7-12, 1983 Vaughan LC: Growth plate defects in dogs. Vet Rec 98:185-189, 1976

Address reprint requests to Ann L. Johnson, DVM, MS University of Illinois 1008 W. Hazelwood Drive Urbana, IL 61801