The Effect of Triple Pelvic Osteotomy on the Articular Contact Area of the Hip Joint in Dysplastic Dogs: An in Vitro Experimental Study

OBJECTIVE: To investigate the effect of triple pelvic osteotomy (TPO) on articular contact area and acetabular coverage of dysplastic hip joints in dogs. STUDY DESIGN: Articular contact area and femoral head coverage by the acetabulum were computed in vitro in normal and dysplastic canine hips. The effect of TPO on articular contact and coverage was then analyzed in the dysplastic hips. Sample Population-Five normal and six dysplastic canine cadaver specimens. METHODS: Contact area and coverage of loaded hips were computed using serial computed tomography scan images before and after TPO. Three angles of acetabular ventroversion (AVV) were studied (20 degrees, 30 degrees, and 40 degrees). Using a custom-designed hinge plate, angles of spontaneous hip reduction in dysplastic hips were compared with previously recorded angles of reduction determined by the Ortolani test. RESULTS: Contact area significantly increased from 0 degrees to 30 degrees of AVV, then remained virtually unchanged. Coverage significantly increased from 0 degrees to 20 degrees of AVV. Both contact and coverage of normal hips were similar, yet significantly smaller than those of dysplastic hips once reduction had occurred. The experimental angles of reduction were significantly smaller and poorly correlated with the angles of reduction determined by the Ortolani test. Although coverage continued to increase with AVV, the actual joint contact area did not significantly vary after relocation of the femoral head. CONCLUSIONS: This study suggests that increasing AVV beyond 20 degrees does not significantly improve the beneficial effects of TPO and therefore should be carefully weighed against increased risks of postoperative complications associated with large angles of AVV.