Leg length discrepancy after total hip arthroplasty: comparison of 3 intraoperative measurement methods

Introduction: Total hip arthroplasty (THA) is 1 of the most successful and frequent orthopaedic procedures around the world. Leg length discrepancy is reported in 1% to 60% of cases and is 1 of the most frequent causes of patient dissatisfaction and a common reason for litigation. The aim of this study was to compare leg length discrepancies following THA using 3 different intraoperative measuring methods. Material and methods: We present a prospective cohort study of 454 hips undergoing THA for osteoarthritis between January 2009 and August 2016. We compared postoperative leg length discrepancy using 1 of the following 3 measurement methods: (1A) direct intraoperative comparison of the legs; (1B) measurement with a compass-like device with supra-acetabular fixation, involving length and offset; (1C, D) an intraoperative device that measures the trochanteric/joint ratio. Results: Leg length discrepancy >5 mm was present in 26% of the total study population. Direct intraoperative leg-to-leg assessment resulted in the greatest proportion of leg length discrepancy >5 mm (31%), followed by the compass group (27%) and the least discrepancy was observed in the trochanteric/joint ratio group (15%). The trochanteric/joint ratio assessment method resulted in the greatest reduction in discrepancy when compared to the other methods: discrepancies of 5-10 mm fell by 48% (relative risk [RR] 0.40 CI [confidence interval [CI] 95%, 0.22-0.74), and discrepancies of ≥10 mm fell by 59% (RR 0.52; CI 95%, 0.32-0.84). Conclusions: We conclude that the use of an intraoperative measurement device can reduce the leg length discrepancy, with best results when using the trochanteric/joint ratio device.