A novel method for assessing leg length discrepancy after total hip arthroplasty: Measurement of the trochanter major–ischial tuberosity distance

Leg length discrepancy is a common and clinically important complication following total hip arthroplasty. It may lead to patient dissatisfaction, altered gait, and functional impairment. Although radiographic assessment is widely used, existing measurement methods can be affected by pelvic rotation and anatomical variations. This study aimed to evaluate the reliability and validity of a novel radiographic method based on the distance between the greater trochanter and the ischial tuberosity for assessing leg length discrepancy after hip arthroplasty. This retrospective cohort study included 56 patients who underwent hip arthroplasty between 2020 and 2023 and had appropriate postoperative standing pelvic radiographs. Leg length was measured clinically using the anterior superior iliac spine-medial malleolus distance, and radiographically using 3 different methods: teardrop to lesser trochanter, greater trochanter to ischial tuberosity, and anterior superior iliac spine to ankle. All radiographic measurements were performed twice, 2 weeks apart, by 2 orthopedic surgeons. Intraobserver and interobserver reliability were assessed using the intraclass correlation coefficient (ICC). Pearson correlation analysis was used to evaluate the relationship between the measurement methods. Receiver operating characteristic (ROC) analysis was used to assess the diagnostic performance of each method in identifying leg length discrepancy of ≥ 10 mm. The mean age of the patients was 66.8 ± 9.1 years. The greater trochanter-ischial tuberosity method showed excellent intraobserver and interobserver reliability (ICC > 0.84). A strong positive correlation was found between this method and the anterior superior iliac spine-ankle measurement (P < .001). The novel method also demonstrated the highest diagnostic accuracy in detecting leg length discrepancies ≥ 10 mm (AUC: 0.96). The greater trochanter-ischial tuberosity distance is a reliable, reproducible, and practical radiographic measurement method for assessing leg length discrepancy after hip arthroplasty. Its reduced sensitivity to pelvic rotation and anatomical variation makes it a promising alternative to traditional methods, especially in clinical settings where full-limb imaging is not available.