Determining Radiographic Reliability of Pelvic Landmarks in Assessing Limb Length Discrepancy Following Total Hip Arthroplasty.

Limb length discrepancy (LLD) is a frequent complication following total hip arthroplasty (THA) often associated with patient dissatisfaction. Radiographic landmarks are commonly used to determine limb length, but their reliability and accuracy remain to be validated. One-hundred and sixty-two preoperative standing pelvic radiographs from patients undergoing THA were measured using four common landmarks (teardrop, ischial tuberosity, obturator foramen, and iliac crest.) LLD and angular differences between measurements were obtained. Comparison of these landmarks for measuring leg lengths showed weak correlation and wide ranges of LLD for each method - in some cases differing by 30 mm. Angular comparisons showed similar results. Surgeons should be cautioned that there is no standard and reliable method for radiographic measurement of leg length in association with hip replacement surgery and use of these techniques in clinical and research settings should be approached cautiously. (Journal of Surgical Orthopaedic Advances 32(1):028-031, 2023).