Prediction of Postoperative Stem Anteversion in Crowe Type II/III Developmental Dysplasia of the Hip on Preoperative Two-Dimensional Computed Tomography.

Background: Preoperative planning is fundamental for total hip arthroplasty. This study investigated the optimal femoral neck level for measuring femoral anteversion to predict postoperative stem anteversion in developmental dysplasia of the hip and determined the predictive role of average anteversion based on the sagittal 3-point fixation.

Methods: Sixty-two Crowe type II/III dysplastic hips that underwent total hip arthroplasty were retrospectively analyzed. Preoperative and postoperative anteversion was measured via 2-dimensional computed tomography. Anterior and posterior cortex anteversions were measured at 6 levels of the proximal femur. Femoral anteversion at each level was calculated. Average anterior (lesser trochanter) and posterior cortex anteversions (femoral neck) were calculated based on the sagittal 3-point fixation.

Results: From the lesser trochanter to head-neck junction, femoral anteversion decreased gradually from more to less than stem anteversion. For hips with femoral neck height ≥10 mm, femoral anteversion at the 10-mm level above the lesser trochanter proximal base showed no significant difference with stem anteversion, with a good correlation for the single-wedge and an excellent correlation for the double-wedge stem. Average anterior (lesser trochanter proximal base) and posterior cortex anteversions (femoral neck at 10 mm above the lesser trochanter proximal base) showed no significant difference from stem anteversion, with excellent correlations.

Conclusion: For Crowe type II/III hips with femoral neck height ≥10 mm, the 10-mm level above the lesser trochanter proximal base is an optimal choice for measuring femoral anteversion to predict postoperative stem anteversion. The average of anterior cortex anteversion at the lesser trochanter and posterior cortex anteversion at the femoral neck has a predictive role.