Risk Factors for Ventral Luxation in Canine Total Hip Replacement

OBJECTIVE: To identify risk factors associated with ventral luxation (VL) of canine total hip replacement (THR), and outcome. STUDY DESIGN: Retrospective study. ANIMALS: Dogs (n=602) that had THR (563 cemented, 35 cementless, 4 hybrid). METHODS: Dogs (1999-2004) with VL after THR were compared with dogs with uncomplicated THR. Data included signalment, body weight, diagnosis, implant size, acetabular cup orientation, and femoral displacement ratio (FDR). RESULTS: VL was diagnosed in 11 (1.8%) dogs after primary THR. Including 2 other dogs that had VL after the study period, 10 (77%) of 13 dogs had VL within 7 days of surgery. Risk factors for VL included Saint Bernard-type dogs (P=.0001), short neck extension (P=.0005), and high angle of lateral opening in other breeds (P=.018). There were trends toward higher risk of VL with lower FDR in Saint Bernard types (P=.060), and with cementless implants (P=.061). Twelve dogs had revision arthroplasty that was successful in all cementless and 2 cemented VL cases. Five dogs had recurrent VL and a poor outcome. CONCLUSION: VL is generally an early complication of THR, with no single common risk factor identified. CLINICAL RELEVANCE: Saint Bernard types and short neck extensions are associated with increased risk of VL. Poor cup orientation is a determining factor for VL in some dogs, but a protective orientation of the acetabular cup was not found. Revision is successful in most dogs, but recurrent VL merits a guarded prognosis.