Three intraoperative methods to determine limb-length discrepancy in THA.

Limb-length discrepancy (LLD) is a common concern for both surgeon and patient in the setting of elective total hip arthroplasty (THA). There is a paucity of evidence guiding surgeons to an optimal method for measuring intraoperative LLD and minimizing postoperative LLD. The primary objective of this prospective, randomized, double-blinded study was to determine which of 3 intraoperative methods used at the authors' institution was best correlated to postoperative radiographic LLD. From 2011 to 2012, 81 patients undergoing either primary (75) or revision (6) THA with an anterolateral (Watson-Jones) approach were prospectively randomized and received intraoperative measurement of LLD via 1 of 3 methods: abductor shuck (AS), tranosseous pins with calibrated caliper (TP), or patella electrocardiogram (EKG) leads (PL). Intraoperative measurements of LLD were compared to clinical and radiographic postoperative measurements of LLD, and absolute differences and correlation coefficients were calculated for each method. Overall, the mean LLD preoperatively was 8.09 mm, and mean radiographic LLD postoperatively was 4.20 mm. The AS method was associated with the highest correlation to postoperative radiographic LLD (R=0.360; P<.05), whereas the other methods had mildly positive but statistically insignificant correlations (TP R=0.275; P>.05; PL R=0.301; P>.05). The AS method best correlates to postoperative radiographic LLD among the 3 techniques, although all methods were positively correlated. Clinical measurements of LLD correlate poorly with radiographic measurements and may be of limited utility.