Evaluation of risk factors for luxation after total hip replacement in dogs

Objective-To identify risk factors for luxation after canine total hip repl acement (THR). Study design-Retrospective study. Sample population-256 client-owned dogs that underwent THR. Methods-Patient data surveyed included signalment, body weight, diagnosis, prior hip surgery, implant size, intraoperative complications, and angle of lateral opening of the acetabular component. Results-Postoperative complications were recorded in 20 cases (7.8%). The m ost common complication was dorsal luxation which occurred in 12 dogs (4.7% ). The interval between joint replacement and luxation ranged from 1 to 116 days (mean, 44 days). In 1 case, luxation was attributable to failure of t he repair of an intraoperative fracture of the greater trochanter. Excludin g this case, the mean angle of lateral opening in those dogs that sustained luxation was 62 degrees (range, 46 degrees -75 degrees). The mean angle of lateral opening overall was 48 degrees (range, 18 degrees -76 degrees). Th e angle of lateral opening was the only factor that had a statistically sig nificant effect on whether luxation occurred (P =.035). Acetabular revision , performed primarily to reduce the angle of lateral opening, was performed in 8 dogs and successfully prevented subsequent luxation. Conclusion-Luxation of the prosthesis is substantially under the control of the surgeon. It is recommended that the acetabular cup be inserted at an a ngle of lateral opening of 35 degrees to 45 degrees. In those cases of THR luxation in which an inappropriate angle of lateral opening is identified, acetabular revision arthroplasty generally results in a good clinical outco me. (C) Copyright 2000 by The American College of Veterinary Surgeons.