Evaluation of the ranawat triangle method for determining hip rotation center in total hip arthroplasty among Turkish patients

Accurate identification of the anatomical femoral head center is critical in total hip arthroplasty for optimal implant positioning and long-term survival. The Ranawat triangle method is widely used for this purpose, but its applicability may vary across populations. The aim of this study was to evaluate the accuracy and suitability of the Ranawat triangle method in estimating the anatomical femoral head center in a Turkish population.

Standardized anteroposterior pelvic radiographs of 260 non-fractured hips from 312 patients aged 60-90 were retrospectively analyzed. Pelvic height, pelvic width, and femoral head diameter were measured. The coordinates of the anatomical femoral head center were calculated anatomically and using the Ranawat triangle method. Deviations between the two were assessed in both axes, with <5 mm considered acceptable error.

Anatomical femoral head center estimated by the Ranawat triangle method was positioned an average of 4.7±1.5 mm medially and 1.0±0.8 mm cranially in men, and 4.8±1.1 mm medially and 1.1±0.7 mm cranially in women, relative to the anatomical center. While 100% of Y-axis errors and 58.1% of X-axis errors were within 5 mm. Strong positive correlations were found between pelvic height and Cy (r=0.59), and pelvic width and Cx (r=0.82).

The Ranawat triangle method method demonstrated excellent accuracy in predicting the vertical (Y-axis) position of the anatomical femoral head center but showed moderate lateral (X-axis) deviations in over 40% of cases. Despite its limitations in lateral offset prediction, it may serve as a practical reference method for preoperative planning, particularly for estimating the vertical position of the hip rotation center in Turkish total hip arthroplasty patients.