Can the hip joint center be estimated from pelvic dimensions in dysplastic hips?

BACKGROUND: We aimed to determine correlations between the hip joint center position and pelvic dimensions and whether the three-dimensional position of the original hip joint center could be estimated from pelvic landmarks in dysplastic and normal hips.

METHODS: We reviewed the pelvic CT scans of 70 patients (70 hips) with hip dysplasia. Seventy-seven normal hips were used as controls. The hip joint center coordinates (Cx, Cy, and Cz) and pelvic dimensions were measured with reference to the anterior pelvic plane coordinate system. Multiple regression formulas were used to estimate the original hip joint center.

RESULTS: The hip center for both dysplastic and normal hip was highly correlated with the distance between the anterior superior iliac spine (ASIS) in the coronal plane (r = 0.76 and 0.84), the distance from the ASIS to the pubic tubercle in the sagittal plane (r = 0.81 and 0.76), and distance from the pubic tubercle to the most posterior point of the ischium on the transverse plane (r = 0.76 and 0.78). The hip joint center could be estimated within a 5-mm error for more than 80% of hips on their respective axes in both dysplastic and normal hips.

CONCLUSIONS: The three-dimensional position of the original hip joint center was correlated with pelvic dimensions, and can be estimated with substantial accuracy using pelvic landmarks as references. Although these results are preliminary, this estimation method may be useful for surgeons planning total hip arthroplasties.