Veterinary Surgery, 21,4, 299-303,1992
Unilateral and Bilateral Stifle Arthrodesis in Eight Dogs MARK A. COFONE, vMD, GAIL K. SMITH, VMD, PhD, TIMOTHY M. LENEHAN, DVM, Diplomate ACVS, and CHARLES D. NEWTON, DVM, MS, Diplomate ACVS Nine stifle arthrodeses in eight dogs were reviewed retrospectively to evaluate use of the limb, each dog’s comfort, complications, and factors that may have influenced the final outcome. Ability to use the limb after unilateral fusion was good (limb used at ail times) in three dogs, fair (limb used at all gaits except a gallop) in three dogs, and poor (limb used only when running) in one dog. Factors that appeared to affectthe outcome included angle at which the stifle was fused and lesions in the ipsilateral coxofemoral joint. One dog with bilateral arthrodesis had a good outcome with minor limitations. The only potentially devastating complications occurred in one dog in which infectionand premature implant looseningjeopardized the fusion. None of the dogs exhibited signs of pain and all owners were satisfied with the results.
diseases involving the stifle can be M treated medically or surgically to reestablish clinically acceptable function. Sometimes even the most me-
Materials and Methods
OST INJURIES OR
ticulous repair cannot correct an overwhelming injury. Arthrodesis of the stifle is an uncommon procedure in dogs, but it has been advocated when severe lesions have rendered the joint nonfunctional.’ General indications for arthrodesisof the stifle include intractable pain; instability resulting in dysfunction;septic arthritis; irreparablejoint, muscle and bone lesions; peripheral nerve injury; and limb-sparing surgery for tumors involving the femur or tibia.24 The methods for performing stifle arthrodesis have been described, and cranial placement of a plate is the most ~ o m m o n . ’ , Other ~ * ~ , means ~ include full- and half-pin external skeletal fixation and transarticular pins or screws.’ Transarticular stabilization is not recommended in dogs or cats that weigh more than 9 kg.’ Whichever technique is used, strict compliancewith the principles of arthrodesis, removal of all articular cartilage, cancellous bone grafting, rigid fixation, and functional anatomic positioning are necessary.*” Although there are several published reports on the methods for stifle arthrodesis, there are, to our knowledge, no reports on the clinical outcome of this surgery. The purpose of this study is to evaluate the postoperative limb function, patient comfort, complications, contraindications, and owner acceptance.
The case records of eight dogs that underwent stifle arthrodesis between 1982 and 1988 at the Veterinary Hospital of the University of Pennsylvania (7 dogs) and the San Diego Veterinary Referral Service (1 dog) were reviewed. Criteria included indication for arthrodesis, methods of arthrodesis, complications, overall function and comfort of the dog, and owner satisfaction. Records and radiographs were reviewed, telephone contact was made with each owner, and five dogs were available for reexamination. Owners were questioned to determine use of the limb when standing, walking, and running, the perceived comfort level, problems since surgery, and their level of satisfaction with the outcome. The overall function and comfort of each dog was compared to the dog’s preoperative status. Clinical reexamination of five dogs allowed an assessment of the ability to use the limb and the way in which the gait was affected by the arthrodesis. The gait was compared to the normal canine gait6 The stifle and both hips were radiographed to evaluate the status of the fusion and fixation device and to identify any pathologic changes that might be attributed to the arthrodesis. Arthrodesis was performed by using a lateral approach to the stifle and by osteotomy of the tibial crest to mobilize the patella.7 Depending on the lesions and the size of the
From the Department of Clinical Studies, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania (Cofone, Smith, Newton), and San Diego Veterinary Referral Service, San Diego, California (Lenehan). Reprint requests: Mark A. Cofone, VMD, Ethicon, Inc., P.O. Box 151, Somerville, NJ 08876.
299
300
STJFLE ARTHRODESJS TABLE 1. Signalment of Eight Dogs Treated by Arthrodesis of the Stifle
Dog Number 1 2 3 4
5 6 7 8
Age at Time of Surgery (Months)
Age at Reevaluation (Months)
Sex
Breed
Weight at Surgery (kg)
34 14 12 (first stifle) 16 (second stifle) 132 68 102 72 72
48 70 46
FS M F
Husky German shepherd Mixed breed
20 37 15
148 72 107 168 84
F FS
German shepherd Yorkshire terrier Boxer German shepherd Golden retriever
44
M FS F
5 35 27 25
F = Female. FS = Female spayed. M = Male.
dog, articular cartilage was removed with an oscillating saw, an osteotome, or rongeur forceps. Subchondral bone removed with the osteotomies was harvested for a cancellous graft. If necessary, additional cancellous bone was taken from the humerus or the ilium. Arthrodesis angle was based on a preoperative measurement of the contralateral stifle while the dog was standing. This angle was increased 5" to 10" to compensate for the unavoidable shortening in limb length caused by the femoral and tibial osteot~mies.~ Further increases were made in dogs 2, 4, 5, 6, and 7 to compensate for pathologic femoral or tibial shortening. A subjective determination was necessary to ensure that the limb was long enough to allow the paw to touch the ground when the dog was standing. The exception was dog 3 in which both stifles were arthrodesed; here, an attempt was made to fuse the stifles at the same angle. All stifles were stabilized with a dynamic compression plate applied along the cranial aspect of the femur and tibia. In three stifles, transarticular pins were inserted to help maintain the angle before application of the plate. In one dog, two screws were placed across the joint in lag fashion to enhance stability. In all cases, the tibial tuberosity was secured to the medial or lateral aspect of the tibia with several pins. Plate selection was based on AOASIF guidelines for the appropriate strength.8Plate length exceeded that which would give only the recommended six cortices above and below a fracture line. A padded bandage was applied for 2 days to control swelling, and appropriate analgesics were administered as needed. Only dog 3, with bilateral fusions, had prolonged external support. After the first operation, a padded bandage was used for 2 weeks. After the second operation 4 months later, a lateral coaptation splint made of thermoplastic material* was used for 4 weeks. * Polyform, Smith &Nephew Rolyan, Menomonee Falls, Wisconsin.
Follow-up examinations with radiographic evaluation of the stifle were performed every 2 to 4 weeks until the arthrodesis was complete. Activity was restricted to short leash walks until bony union was evident radiographically. The dogs were then allowed to return to normal activity. Results Nine stifle arthrodeses in eight dogs were available for evaluation (Table 1). There were 6 females and 2 males ranging in age from 12 to 132 months (mean, 58 months) and in weight from 5 to 44 kg (mean, 26 kg) at the time of surgery. The interval to follow-up was 4 to 96 months (mean, 29 months). Trauma was the initiating cause in six dogs (Table 2). In dogs 1 and 8, stifle fusion was elected as the primary treatment because of irreparable loss of joint components. In dogs 2, 5 , 6, and 7, primary repair of distal femoral fractures had failed. Dog 3 suffered severe contracture of both quadriceps muscle groups caused by congenital toxoplasmosis. The muscle fibers were severely atrophied and fibrotic, so that with growth of the femurs the stifles were fixed in hyperextension. Dog 4 had severe degenerative joint disease of unknown etiology, with pain and a 70% decrease in the range of motion. Two dogs had concurrent problems affecting the musculoskeletal system. Dog 8 sustained a luxated hip and severely traumatized fourth and fifth digits on the ipsilateral limb. The digits could not be repaired because of loss of the third, second, and most of the first phalanges of each digit. Femoral head and neck excision was performed because of chronic recurrent luxations of the hip. A fistulous tract developed on day 14 in dog 4. Staphylococcus epidermitis, which was sensitive to trimethoprim-sulfadiazinet, was isolated from the tract. The dog
t Tribrissen, Coopers Animal Health, Kansas City, Missouri.
COFONE, SMITH, LENEHAN, AND NEWTON
301
TABLE 2. Arthrodesis of the Stifle in Eight Dogs Dog Number
1
2
3
Indication for Arthrodesis Shear injury medial stifle. Loss of 1/3 medial femoral condyle and 1 /3 tibial plateau. Distal femoral nonunion. Ruptured medial collateral ligament. DJD after pin migration. Quadriceps contracture from congenital toxoplasmosis infection.
4
Chronic DJD of unknown origin.
5
Distal femoral nonunion. Disruption of articular cartilage.
6
Distal femoral nonunion. Disruption of articular cartilage. Distal femoral nonunion. DJD after pin migration.
7
8
Shear injury to stifle. Loss of medial 1/3 of femoral condyle and tibial plateau.
Method of Fixation
4.5 DCP 12 hole (1 nut) 4.5 DCP Broad 14 hole (one 6.5 cancellous screw) R-3.5 DCP 8 hole L-3.5 DCP 10 hole 4.5 DCP 9 hole (four 6.5 cancellous screws) 2.7 DCP 10 hole (one 3.5 cancellous screw) 4.5 DCP 12 hole 4.5 DCP Broad 14 hole (four 6.5 cancellous screws) 4.5 DCP 12 hole
Stifle Norm.
Angle Arthrodesis
Clinical Results
140"
144"
Good
NA
128"
Fair
132"
Good
133" NA
110"
Good
130"
155"
Good
140"
160"
Fair
NA
128"
Poor
135"
140"
Fair
DCP = Dynamic compression plate; DJD = degenerative joint disease.
Good = Uses limb under all circumstances. Fair = Uses limb at a walk and standing. Poor = Uses limb at a run only. NA = Not available.
was treated for 4 weeks and no further drainage was noted. There was no radiographic evidence of active osteomyelitis. At week 4, the distal aspect of the plate had separated from the tibia by 2 to 3 mm, and the dog was restricted to minimal activity. At week 8, the arthrodesis was healing satisfactorilyand the plate had not moved, so activity was increased. Clinical evaluations were based on the dog's ability to use the leg, its perceived comfort level, and the owner's satisfaction (Table 2). Before surgery, the dogs with unilateral stifle arthrodesis did not bear weight on the limb, and the dog requiring bilateral stifle arthrodesis was unable to use either hind limb and dragged herself by her forelimbs. In the postoperative period, none of the dogs was considered to have an excellent outcome because all used the limb or limbs with an abnormal motion. Dogs 2,4, and 7 were not available for reexamination, so clinical outcome was based on the owners' evaluations. Dog 4 used the limb under all circumstances. Dog 2 used the limb for standing and walking but not at faster gaits. Dog 7 used the limb only when running.
Follow-up examination was available for dogs 1, 3, 5, 6, and 8. Dog 3, with bilateral arthrodesis, was examined 30 months after the second procedure. The dog advanced both hind limbs together in a rabbit-hopping motion, but it did this very efficiently up to speeds comparable to a trot. The dog could not go up stairs without assistance but was able to go down. It tended to strike its toenails when advancing the hind limbs, as evidenced by worn ends of the nails. Dogs 1, 5, 6, and 8 were examined at months 14,4, 5, and 12. Dogs 1 and 5 used the limb while standing and at all gait speeds. Dogs 6 and 8 used the limb while standing and at a walk and trot, but not at a gallop. The dogs circumducted the limb as they advanced it forward, with most of the motion occurring in the hip and very little change in the angle of the hock. Three dogs with unilateral arthrodesis were considered to have a good outcome (limb used by the dog at all times), three had a fair outcome (limb used at all times except at a gallop), and one outcome was considered poor (limb used only when the dog was running). All dogs except
STIFLE ARTHRODESIS dogs 3 and 5 were able to go up and down stairs. All dogs were reported to be “comfortable” by their owners, and all owners were satisfied by the outcome and functional ability of their dogs, feeling that given the same set of circumstances they would again elect to have fusion rather than amputation.
Discussion The results of this retrospective study indicate that stifle arthrodesis provided acceptable restoration of limb function after severe, irreparable stifle disease or injury. None of the dogs in this study regained normal function because of the unavoidable “mechanical” lameness associated with loss of stifle motion. Why some dogs had better use of the limb than others could not be determined with certainty. Ability to touch the paw to the ground without a significant change in attitude of the contralateral limb and a good range of motion in the ipsilateral hip seemed to play important roles. Dog 8, which underwent femoral head and neck excision at the time of arthrodesis, had a marked decrease in the range of motion at the coxofemoral pseudarthrosis at month 12. Limited ability to circumduct the hip made it difficult to advance the limb; this dog used the limb when standing or walking, but not when running. It would appear that any hip lesion can diminish the ultimate function of a limb with an arthrodesed stifle because all motion to advance the limb comes from the hip. Consideration should be given to staging surgery on the hip so that maximum rehabilitation can be achieved. The only guide for selection of the appropriate angle at which to arthrodese a stifle has been to measure the angle of the normal limb while the animal is standing, and to add 5” to 10” to allow for shortening caused by the pr oc e d~r e It . ~is difficult to obtain a precise measurement with this method; it does not take into account the loss of bone that may have occurred from the lesions within the joint or in adjacent long bones. In each case except the bilateral arthrodesis, the final determination was made at surgery to take all factors affecting the angle into account to try to ensure that the paw would touch the ground when the dog was standing. In dogs 5 and 6 , the normal stifle angles were 130” and 140°, but the significant amount of femoral shortening caused by previous surgery and nonunion made it necessary to arthrodese the stiflesat 155” and 160°, respectively. The method was not precise and was subject to error. In dog 7, which had the poorest end result because it used the leg only when running, the owner reported that the leg appeared to be too short to touch the ground without the dog greatly bending the contralateral stifle. Unfortunately, this dog was unavailable for examination. None of the dogs appeared to have a problem with the leg being too long.
Until a system is devised that can take all variables into account accurately, we believe it is better to err on the side of making the stifle straighter and the leg longer. It has been stated that bilateral stifle arthrodesis should not be attempted because the animal would not be able to perform simple functions. With severe bilateral fibrosis of the quadriceps muscles secondary to congenital toxoplasmosis, dog 3 had extreme stifle hyperextension and was unable to walk. After bilateral arthrodesis, the dog was able to perform most daily activities very well, except going up stairs, and no major problems have occurred subsequently. Fusing the stifles at less then 132” might have prevented wearing the toenails on a hard, rough surface. The use of external support postoperatively has been advocated.* In this series, coaptation was used beyond the immediate postoperative period only in dog 3 , with bilateral fusions, because of the need for immediate postoperative weight bearing on the treated limb. In dog 1, the arthrodesis was postponed for 12 weeks to allow a contralateral femoral fracture to heal. There were no complications that could be associated with the lack of external support. It would appear from this limited series that external support of the fused stifle is not necessary if the dog has three other functional limbs. The only postoperative complications occurred in dog 4, in which a fistulous tract and loosening of the distal screws was noted on day 14. Premature loosening of the distal screws may have been related to the bone quality, length of the plate, and angle of the arthrodesis. The bone was considered to be extremely osteoporotic, based on its radiographic appearance and texture at surgery. This probably reflected the patient’s age and disuse caused by severe osteoarthriti~.~.’~ Osteoporosis should be considered when working with bone in a limb that has had a chronic non-weight-bearing lameness. l o Another reason for loosening of the screws may have been that the plate length in relation to the size of this dog was shorter than in the other cases (Tables 1 and 2). A longer plate would have provided more screw holes and, therefore, more holding power. Another benefit of using a longer plate is that the high bending moment and stress concentration at the plate ends (proximal and distal screw holes) can be reduced. It should, therefore, not be necessary to remove the plate when healing is achieved to prevent fracture at the ends of the plate, as has been s~ggested.~ The fixation in dog 4 was at a mechanical disadvantage because of the sharp angle of fusion ( 1 lo”), which was necessary to keep the leg at the correct length because of the dog’s conformation and minimal loss of bone. The more acute the angle, the greater the bending moment about the joint, which increases the stress on the plate and screws. The angle of fusion, the quality of the bone,
’
COFONE, SMITH, LENEHAN, AND NEWTON
and the size of the dog must be taken into account when choosing the length and cross-sectional size of a plate. Dogs 4 and 7 had moderate to severe degenerative joint disease of the hips, and dog 4 had a total hip prosthesis in the contralateral hip. It was believed that stifle arthrodesis was preferable to amputation in these dogs because they would have great difficulty getting up and moving about with only three limbs. Although all owners realized their dogs were moving the arthrodesed limb in an abnormal manner, all thought that the dogs were comfortable and they were pleased with the outcomes. Each stated that he would make the same decision, given the alternatives of limb dysfunction or amputation. References 1. Newton CD. Arthrodesis of the stifle, tarsus and interphalangeal
joints. In: Newton CD, Nunarnaker DM (eds). Textbook ofsmall Animal Orthopaedics. Philadelphia: JB Lippincott, 1985:57 1-575. 2. Moore RW, Withrow SJ. Arthodesis. Cornp Cont Ed 1981;3:319329.
303
3. Newton CD. Principles and techniques of arthrodesis. In: Newton CD, Nunarnaker DM (eds). Textbook of Small Animal Orthopaedics. Philadelphia: JB Lippincott, 185:561-563. 4. Lesser AS. Arthrodesis. In: Slatter DH (ed). Textbook ofSmallAnima1 Surgery. Philadelphia: WB Saunders, 1985:2263-2276. 5. Newton CD, Nunarnaker DM. Arthrodesis of the stifle joint. In: Brinker WO, Hohn RB, Prieur WD (eds). Manual of Internal Fixation in Small Animals. New York, Springer-Verlag, 1984: 269-27 I . 6. Nunarnaker DM, Blauner PD. Normal and abnormal gait. In: Newton CD, Nunarnaker DM (eds). Textbook ofSmaN Animal Orthopaedics. Philadelphia: JB Lippincott, 1985:1083-1095. 7. Piermattei DL, Greeley RG. Atlas of Surgical Approaches to the Bones ofthe Dog and Cat. 2nd ed. Philadelphia: WB Saunders, 1979:164. 8. Brinker WO. Guidelines for selecting bone plate and screw size. In: Brinker WO, Hohn RB, Prieur WD (eds). Manual of Internal Fixation in Small Animals. New York, Springer-Verlag, 1984: 104- 105. 9. Detenbeck LC, Jowsey J. Normal aging in the bone of the adult dog. Clin Orthop 1969;65:76-80. 10. Whittick WG. Osteopenia due to a stress deficiency. In: Whittick WG (ed).Canine Orthopedics. Philadelphia, Lea & Febiger, 1974: 41-42.
Unilateral and Bilateral Stifle Arthrodesis in Eight Dogs MARK A. COFONE, vMD, GAIL K. SMITH, VMD, PhD, TIMOTHY M. LENEHAN, DVM, Diplomate ACVS, and CHARLES D. NEWTON, DVM, MS, Diplomate ACVS Nine stifle arthrodeses in eight dogs were reviewed retrospectively to evaluate use of the limb, each dog’s comfort, complications, and factors that may have influenced the final outcome. Ability to use the limb after unilateral fusion was good (limb used at ail times) in three dogs, fair (limb used at all gaits except a gallop) in three dogs, and poor (limb used only when running) in one dog. Factors that appeared to affectthe outcome included angle at which the stifle was fused and lesions in the ipsilateral coxofemoral joint. One dog with bilateral arthrodesis had a good outcome with minor limitations. The only potentially devastating complications occurred in one dog in which infectionand premature implant looseningjeopardized the fusion. None of the dogs exhibited signs of pain and all owners were satisfied with the results.
diseases involving the stifle can be M treated medically or surgically to reestablish clinically acceptable function. Sometimes even the most me-
Materials and Methods
OST INJURIES OR
ticulous repair cannot correct an overwhelming injury. Arthrodesis of the stifle is an uncommon procedure in dogs, but it has been advocated when severe lesions have rendered the joint nonfunctional.’ General indications for arthrodesisof the stifle include intractable pain; instability resulting in dysfunction;septic arthritis; irreparablejoint, muscle and bone lesions; peripheral nerve injury; and limb-sparing surgery for tumors involving the femur or tibia.24 The methods for performing stifle arthrodesis have been described, and cranial placement of a plate is the most ~ o m m o n . ’ , Other ~ * ~ , means ~ include full- and half-pin external skeletal fixation and transarticular pins or screws.’ Transarticular stabilization is not recommended in dogs or cats that weigh more than 9 kg.’ Whichever technique is used, strict compliancewith the principles of arthrodesis, removal of all articular cartilage, cancellous bone grafting, rigid fixation, and functional anatomic positioning are necessary.*” Although there are several published reports on the methods for stifle arthrodesis, there are, to our knowledge, no reports on the clinical outcome of this surgery. The purpose of this study is to evaluate the postoperative limb function, patient comfort, complications, contraindications, and owner acceptance.
The case records of eight dogs that underwent stifle arthrodesis between 1982 and 1988 at the Veterinary Hospital of the University of Pennsylvania (7 dogs) and the San Diego Veterinary Referral Service (1 dog) were reviewed. Criteria included indication for arthrodesis, methods of arthrodesis, complications, overall function and comfort of the dog, and owner satisfaction. Records and radiographs were reviewed, telephone contact was made with each owner, and five dogs were available for reexamination. Owners were questioned to determine use of the limb when standing, walking, and running, the perceived comfort level, problems since surgery, and their level of satisfaction with the outcome. The overall function and comfort of each dog was compared to the dog’s preoperative status. Clinical reexamination of five dogs allowed an assessment of the ability to use the limb and the way in which the gait was affected by the arthrodesis. The gait was compared to the normal canine gait6 The stifle and both hips were radiographed to evaluate the status of the fusion and fixation device and to identify any pathologic changes that might be attributed to the arthrodesis. Arthrodesis was performed by using a lateral approach to the stifle and by osteotomy of the tibial crest to mobilize the patella.7 Depending on the lesions and the size of the
From the Department of Clinical Studies, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania (Cofone, Smith, Newton), and San Diego Veterinary Referral Service, San Diego, California (Lenehan). Reprint requests: Mark A. Cofone, VMD, Ethicon, Inc., P.O. Box 151, Somerville, NJ 08876.
299
300
STJFLE ARTHRODESJS TABLE 1. Signalment of Eight Dogs Treated by Arthrodesis of the Stifle
Dog Number 1 2 3 4
5 6 7 8
Age at Time of Surgery (Months)
Age at Reevaluation (Months)
Sex
Breed
Weight at Surgery (kg)
34 14 12 (first stifle) 16 (second stifle) 132 68 102 72 72
48 70 46
FS M F
Husky German shepherd Mixed breed
20 37 15
148 72 107 168 84
F FS
German shepherd Yorkshire terrier Boxer German shepherd Golden retriever
44
M FS F
5 35 27 25
F = Female. FS = Female spayed. M = Male.
dog, articular cartilage was removed with an oscillating saw, an osteotome, or rongeur forceps. Subchondral bone removed with the osteotomies was harvested for a cancellous graft. If necessary, additional cancellous bone was taken from the humerus or the ilium. Arthrodesis angle was based on a preoperative measurement of the contralateral stifle while the dog was standing. This angle was increased 5" to 10" to compensate for the unavoidable shortening in limb length caused by the femoral and tibial osteot~mies.~ Further increases were made in dogs 2, 4, 5, 6, and 7 to compensate for pathologic femoral or tibial shortening. A subjective determination was necessary to ensure that the limb was long enough to allow the paw to touch the ground when the dog was standing. The exception was dog 3 in which both stifles were arthrodesed; here, an attempt was made to fuse the stifles at the same angle. All stifles were stabilized with a dynamic compression plate applied along the cranial aspect of the femur and tibia. In three stifles, transarticular pins were inserted to help maintain the angle before application of the plate. In one dog, two screws were placed across the joint in lag fashion to enhance stability. In all cases, the tibial tuberosity was secured to the medial or lateral aspect of the tibia with several pins. Plate selection was based on AOASIF guidelines for the appropriate strength.8Plate length exceeded that which would give only the recommended six cortices above and below a fracture line. A padded bandage was applied for 2 days to control swelling, and appropriate analgesics were administered as needed. Only dog 3, with bilateral fusions, had prolonged external support. After the first operation, a padded bandage was used for 2 weeks. After the second operation 4 months later, a lateral coaptation splint made of thermoplastic material* was used for 4 weeks. * Polyform, Smith &Nephew Rolyan, Menomonee Falls, Wisconsin.
Follow-up examinations with radiographic evaluation of the stifle were performed every 2 to 4 weeks until the arthrodesis was complete. Activity was restricted to short leash walks until bony union was evident radiographically. The dogs were then allowed to return to normal activity. Results Nine stifle arthrodeses in eight dogs were available for evaluation (Table 1). There were 6 females and 2 males ranging in age from 12 to 132 months (mean, 58 months) and in weight from 5 to 44 kg (mean, 26 kg) at the time of surgery. The interval to follow-up was 4 to 96 months (mean, 29 months). Trauma was the initiating cause in six dogs (Table 2). In dogs 1 and 8, stifle fusion was elected as the primary treatment because of irreparable loss of joint components. In dogs 2, 5 , 6, and 7, primary repair of distal femoral fractures had failed. Dog 3 suffered severe contracture of both quadriceps muscle groups caused by congenital toxoplasmosis. The muscle fibers were severely atrophied and fibrotic, so that with growth of the femurs the stifles were fixed in hyperextension. Dog 4 had severe degenerative joint disease of unknown etiology, with pain and a 70% decrease in the range of motion. Two dogs had concurrent problems affecting the musculoskeletal system. Dog 8 sustained a luxated hip and severely traumatized fourth and fifth digits on the ipsilateral limb. The digits could not be repaired because of loss of the third, second, and most of the first phalanges of each digit. Femoral head and neck excision was performed because of chronic recurrent luxations of the hip. A fistulous tract developed on day 14 in dog 4. Staphylococcus epidermitis, which was sensitive to trimethoprim-sulfadiazinet, was isolated from the tract. The dog
t Tribrissen, Coopers Animal Health, Kansas City, Missouri.
COFONE, SMITH, LENEHAN, AND NEWTON
301
TABLE 2. Arthrodesis of the Stifle in Eight Dogs Dog Number
1
2
3
Indication for Arthrodesis Shear injury medial stifle. Loss of 1/3 medial femoral condyle and 1 /3 tibial plateau. Distal femoral nonunion. Ruptured medial collateral ligament. DJD after pin migration. Quadriceps contracture from congenital toxoplasmosis infection.
4
Chronic DJD of unknown origin.
5
Distal femoral nonunion. Disruption of articular cartilage.
6
Distal femoral nonunion. Disruption of articular cartilage. Distal femoral nonunion. DJD after pin migration.
7
8
Shear injury to stifle. Loss of medial 1/3 of femoral condyle and tibial plateau.
Method of Fixation
4.5 DCP 12 hole (1 nut) 4.5 DCP Broad 14 hole (one 6.5 cancellous screw) R-3.5 DCP 8 hole L-3.5 DCP 10 hole 4.5 DCP 9 hole (four 6.5 cancellous screws) 2.7 DCP 10 hole (one 3.5 cancellous screw) 4.5 DCP 12 hole 4.5 DCP Broad 14 hole (four 6.5 cancellous screws) 4.5 DCP 12 hole
Stifle Norm.
Angle Arthrodesis
Clinical Results
140"
144"
Good
NA
128"
Fair
132"
Good
133" NA
110"
Good
130"
155"
Good
140"
160"
Fair
NA
128"
Poor
135"
140"
Fair
DCP = Dynamic compression plate; DJD = degenerative joint disease.
Good = Uses limb under all circumstances. Fair = Uses limb at a walk and standing. Poor = Uses limb at a run only. NA = Not available.
was treated for 4 weeks and no further drainage was noted. There was no radiographic evidence of active osteomyelitis. At week 4, the distal aspect of the plate had separated from the tibia by 2 to 3 mm, and the dog was restricted to minimal activity. At week 8, the arthrodesis was healing satisfactorilyand the plate had not moved, so activity was increased. Clinical evaluations were based on the dog's ability to use the leg, its perceived comfort level, and the owner's satisfaction (Table 2). Before surgery, the dogs with unilateral stifle arthrodesis did not bear weight on the limb, and the dog requiring bilateral stifle arthrodesis was unable to use either hind limb and dragged herself by her forelimbs. In the postoperative period, none of the dogs was considered to have an excellent outcome because all used the limb or limbs with an abnormal motion. Dogs 2,4, and 7 were not available for reexamination, so clinical outcome was based on the owners' evaluations. Dog 4 used the limb under all circumstances. Dog 2 used the limb for standing and walking but not at faster gaits. Dog 7 used the limb only when running.
Follow-up examination was available for dogs 1, 3, 5, 6, and 8. Dog 3, with bilateral arthrodesis, was examined 30 months after the second procedure. The dog advanced both hind limbs together in a rabbit-hopping motion, but it did this very efficiently up to speeds comparable to a trot. The dog could not go up stairs without assistance but was able to go down. It tended to strike its toenails when advancing the hind limbs, as evidenced by worn ends of the nails. Dogs 1, 5, 6, and 8 were examined at months 14,4, 5, and 12. Dogs 1 and 5 used the limb while standing and at all gait speeds. Dogs 6 and 8 used the limb while standing and at a walk and trot, but not at a gallop. The dogs circumducted the limb as they advanced it forward, with most of the motion occurring in the hip and very little change in the angle of the hock. Three dogs with unilateral arthrodesis were considered to have a good outcome (limb used by the dog at all times), three had a fair outcome (limb used at all times except at a gallop), and one outcome was considered poor (limb used only when the dog was running). All dogs except
STIFLE ARTHRODESIS dogs 3 and 5 were able to go up and down stairs. All dogs were reported to be “comfortable” by their owners, and all owners were satisfied by the outcome and functional ability of their dogs, feeling that given the same set of circumstances they would again elect to have fusion rather than amputation.
Discussion The results of this retrospective study indicate that stifle arthrodesis provided acceptable restoration of limb function after severe, irreparable stifle disease or injury. None of the dogs in this study regained normal function because of the unavoidable “mechanical” lameness associated with loss of stifle motion. Why some dogs had better use of the limb than others could not be determined with certainty. Ability to touch the paw to the ground without a significant change in attitude of the contralateral limb and a good range of motion in the ipsilateral hip seemed to play important roles. Dog 8, which underwent femoral head and neck excision at the time of arthrodesis, had a marked decrease in the range of motion at the coxofemoral pseudarthrosis at month 12. Limited ability to circumduct the hip made it difficult to advance the limb; this dog used the limb when standing or walking, but not when running. It would appear that any hip lesion can diminish the ultimate function of a limb with an arthrodesed stifle because all motion to advance the limb comes from the hip. Consideration should be given to staging surgery on the hip so that maximum rehabilitation can be achieved. The only guide for selection of the appropriate angle at which to arthrodese a stifle has been to measure the angle of the normal limb while the animal is standing, and to add 5” to 10” to allow for shortening caused by the pr oc e d~r e It . ~is difficult to obtain a precise measurement with this method; it does not take into account the loss of bone that may have occurred from the lesions within the joint or in adjacent long bones. In each case except the bilateral arthrodesis, the final determination was made at surgery to take all factors affecting the angle into account to try to ensure that the paw would touch the ground when the dog was standing. In dogs 5 and 6 , the normal stifle angles were 130” and 140°, but the significant amount of femoral shortening caused by previous surgery and nonunion made it necessary to arthrodese the stiflesat 155” and 160°, respectively. The method was not precise and was subject to error. In dog 7, which had the poorest end result because it used the leg only when running, the owner reported that the leg appeared to be too short to touch the ground without the dog greatly bending the contralateral stifle. Unfortunately, this dog was unavailable for examination. None of the dogs appeared to have a problem with the leg being too long.
Until a system is devised that can take all variables into account accurately, we believe it is better to err on the side of making the stifle straighter and the leg longer. It has been stated that bilateral stifle arthrodesis should not be attempted because the animal would not be able to perform simple functions. With severe bilateral fibrosis of the quadriceps muscles secondary to congenital toxoplasmosis, dog 3 had extreme stifle hyperextension and was unable to walk. After bilateral arthrodesis, the dog was able to perform most daily activities very well, except going up stairs, and no major problems have occurred subsequently. Fusing the stifles at less then 132” might have prevented wearing the toenails on a hard, rough surface. The use of external support postoperatively has been advocated.* In this series, coaptation was used beyond the immediate postoperative period only in dog 3 , with bilateral fusions, because of the need for immediate postoperative weight bearing on the treated limb. In dog 1, the arthrodesis was postponed for 12 weeks to allow a contralateral femoral fracture to heal. There were no complications that could be associated with the lack of external support. It would appear from this limited series that external support of the fused stifle is not necessary if the dog has three other functional limbs. The only postoperative complications occurred in dog 4, in which a fistulous tract and loosening of the distal screws was noted on day 14. Premature loosening of the distal screws may have been related to the bone quality, length of the plate, and angle of the arthrodesis. The bone was considered to be extremely osteoporotic, based on its radiographic appearance and texture at surgery. This probably reflected the patient’s age and disuse caused by severe osteoarthriti~.~.’~ Osteoporosis should be considered when working with bone in a limb that has had a chronic non-weight-bearing lameness. l o Another reason for loosening of the screws may have been that the plate length in relation to the size of this dog was shorter than in the other cases (Tables 1 and 2). A longer plate would have provided more screw holes and, therefore, more holding power. Another benefit of using a longer plate is that the high bending moment and stress concentration at the plate ends (proximal and distal screw holes) can be reduced. It should, therefore, not be necessary to remove the plate when healing is achieved to prevent fracture at the ends of the plate, as has been s~ggested.~ The fixation in dog 4 was at a mechanical disadvantage because of the sharp angle of fusion ( 1 lo”), which was necessary to keep the leg at the correct length because of the dog’s conformation and minimal loss of bone. The more acute the angle, the greater the bending moment about the joint, which increases the stress on the plate and screws. The angle of fusion, the quality of the bone,
’
COFONE, SMITH, LENEHAN, AND NEWTON
and the size of the dog must be taken into account when choosing the length and cross-sectional size of a plate. Dogs 4 and 7 had moderate to severe degenerative joint disease of the hips, and dog 4 had a total hip prosthesis in the contralateral hip. It was believed that stifle arthrodesis was preferable to amputation in these dogs because they would have great difficulty getting up and moving about with only three limbs. Although all owners realized their dogs were moving the arthrodesed limb in an abnormal manner, all thought that the dogs were comfortable and they were pleased with the outcomes. Each stated that he would make the same decision, given the alternatives of limb dysfunction or amputation. References 1. Newton CD. Arthrodesis of the stifle, tarsus and interphalangeal
joints. In: Newton CD, Nunarnaker DM (eds). Textbook ofsmall Animal Orthopaedics. Philadelphia: JB Lippincott, 1985:57 1-575. 2. Moore RW, Withrow SJ. Arthodesis. Cornp Cont Ed 1981;3:319329.
303
3. Newton CD. Principles and techniques of arthrodesis. In: Newton CD, Nunarnaker DM (eds). Textbook of Small Animal Orthopaedics. Philadelphia: JB Lippincott, 185:561-563. 4. Lesser AS. Arthrodesis. In: Slatter DH (ed). Textbook ofSmallAnima1 Surgery. Philadelphia: WB Saunders, 1985:2263-2276. 5. Newton CD, Nunarnaker DM. Arthrodesis of the stifle joint. In: Brinker WO, Hohn RB, Prieur WD (eds). Manual of Internal Fixation in Small Animals. New York, Springer-Verlag, 1984: 269-27 I . 6. Nunarnaker DM, Blauner PD. Normal and abnormal gait. In: Newton CD, Nunarnaker DM (eds). Textbook ofSmaN Animal Orthopaedics. Philadelphia: JB Lippincott, 1985:1083-1095. 7. Piermattei DL, Greeley RG. Atlas of Surgical Approaches to the Bones ofthe Dog and Cat. 2nd ed. Philadelphia: WB Saunders, 1979:164. 8. Brinker WO. Guidelines for selecting bone plate and screw size. In: Brinker WO, Hohn RB, Prieur WD (eds). Manual of Internal Fixation in Small Animals. New York, Springer-Verlag, 1984: 104- 105. 9. Detenbeck LC, Jowsey J. Normal aging in the bone of the adult dog. Clin Orthop 1969;65:76-80. 10. Whittick WG. Osteopenia due to a stress deficiency. In: Whittick WG (ed).Canine Orthopedics. Philadelphia, Lea & Febiger, 1974: 41-42.
