Effects of degree of acetabular rotation after triple pelvic osteotomy on the position of the femoral head in relationship to the acetabulum

OBJECTIVE: To assess the effect of rotating the acetabulum 20 degrees and 30 degrees on percent coverage (PC) of the femoral head by the acetabulum and Norberg angle (NA) after triple pelvic osteotomy (TPO). STUDY DESIGN: Retrospective study. ANIMAL POPULATION: Fifty-six client-owned dogs. METHODS: PC and NA were measured from preoperative, immediate postoperative, first recheck, and second recheck radiographs to compare the effects of 20 degrees and 30 degrees of rotation of the acetabulum after TPO for treatment of hip dysplasia. RESULTS: Within the 20 degrees rotation group, PC and NA values were significantly greater at each subsequent evaluation time starting at the preoperative measurement except for NA between the first and second recheck times. Within the 30 degrees rotation group, PC and NA values were significantly greater at each subsequent evaluation time starting at the preoperative measurement except for PC and NA between the first and second recheck times. No significant differences between the 20 degrees and 30 degrees rotation groups were found at any corresponding times for either PC or NA. CONCLUSIONS: Acetabular rotation of 20 degrees provided the same degree of improvement in acetabular femoral head coverage as 30 degrees of rotation after TPO at the immediate postoperative, first recheck, and second recheck evaluation times. CLINICAL RELEVANCE: Based on PC and NA, 20 degrees rotation of the acetabulum provides as much benefit as 30 degrees of acetabular rotation when performing a TPO.