Comparison and Validation of Methods for Restoring Neck Length in Hip Arthroplasty That Can Be Applied for Femoral Neck Fracture

Background: Restoring leg length during total hip arthroplasty (THA) for femoral neck fracture is challenging due to the lack of an intact femoral neck on the fractured side. Thus, templating methods typically use size of the intact contralateral hip to estimate length. Common reference points include the distance from the lesser trochanter to the center of the femoral head (LTC) and femoral head diameter (FHD). Objectives: We sought to (1) investigate the LTC:FHD ratio as a preoperative templating method and (2) compare this method with calibrated LTC measurements. Methods: We performed a retrospective review of patients undergoing primary THA between 2021 and 2022 with recorded intraoperative measurements of LTC and FHD at a single academic orthopedic specialty hospital. Preoperative hip X-rays were used to determine the "predicted LTC length" with 2 separate methods: the LTC:FHD ratio yielding the "Ratio Predicted LTC" and the calibrated measurements method yielding the "Calibrated Predicted LTC." These measurements were compared with intraoperative measurements of the LTC length to determine accuracy. Results: Sixty-two hips in 59 patients were studied. The ratio predicted LTC and contralateral ratio predicted LTC length showed no significant difference from the intraoperative LTC length with a strong correlation between the 2 measurements (correlation coefficient = 0.77 and 0.80). The calibrated predicted LTC lengths were significantly different from the intraoperative LTC lengths (mean difference, 3.0 mm; 95% confidence interval [CI] = [2.2, 3.8]). Conclusions: This retrospective review suggests the LTC:FHD ratio multiplied by intraoperative FHD may be an accurate method for restoring anatomic femoral head height in THA (LTC_a = [LTC_r/FHD_r] × FHD_a). This method may be useful in hip fracture populations with distorted proximal femoral anatomy.