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) o n articular contact area and acetabular coverage of dysplastic hip joi nts in dogs. Study Design-Articular contact area and femoral head cove rage 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 cov erage of loaded hips were computed using serial computed tomography sc an images before and after TPO. Three angles of acetabular ventroversi on (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 reduc tion determined by the Ortolani test. Results-Contact area significant ly increased from 0 degrees to 30 degrees of AVV, then remained virtua lly unchanged. Coverage significantly increased from 0 degrees to 20 d egrees 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 AV V, the actual joint contact area did not significantly vary after relo cation of the femoral head. Conclusions-This study suggests that incre asing AVV beyond 20 degrees does not significantly improve the benefic ial effects of TPO and therefore should be carefully weighed against i ncreased risks of postoperative complications associated with large an gles of AVV. (C) Copyright 1998 by The American College of Veterinary Surgeons.