The effect of triple pelvic osteotomy on hip force in dysplastic dogs: a theoretical analysis

The effect of a triple pelvic osteotomy (TPO) procedure on the forces acting about the hip joint was examined in five dysplastic canine hips using a previously described theoretical analysis. Hip reaction force (Fh) and its angle of application (theta h) were calculated from radiographic measurements made before and after TPO procedures which sequentially increased acetabular ventroversion from 0 degree to 20 degrees, 30 degrees, and 40 degrees. The results of the in vitro study showed that Fh decreased with increasing acetabular ventroversion reaching an asymptotic value between 30 degrees and 40 degrees. The decrease in Fh corresponded to an increase in theta h toward the vertical, with statistical significance found in both Fh and theta h between 0 degree and 20 degrees. The changes observed in Fh and theta h after TPO were attributed to the medialization of the femoral head resulting from the reduction of the subluxated head. The results of this study suggest that the noted reduction in the magnitude of the forces acting on the hip joint may act in concert with increased coverage of the femoral head to effect the beneficial clinical results observed with the TPO procedure.