Measurement Techniques for Leg Length Discrepancy in Total Hip Arthroplasty: A Systematic Review of Reliability and Validity.

BACKGROUND: Total hip arthroplasty (THA) carries a substantial litigative burden. THA may introduce leg length discrepancy (LLD), necessitating a valid and reliable technique for LLD measurement. This study investigates the reliability and validity of techniques quantitively measuring LLD both pre- and post-THA. METHODS: Embase and MEDLINE databases were searched following PRISMA guidelines for articles assessing either the validity or reliability of LLD measurement techniques. Data was pooled using random effects meta-analysis to derive reliability estimates. Study quality was assessed using the Brink and Louw checklist. RESULTS: Forty-two articles with 2059 participants were included. Thirty-three investigated reliability and twenty-five validity. Reliability displayed high heterogeneity. Poor to excellent intra-rater reliability was reported for AP pelvis radiographs, moderate to excellent for CT scanograms, good to excellent for clinical methods and teleradiography, and excellent for bi-planar radiography (BPR). Poor to excellent inter-rater reliability was reported for AP pelvis radiographs and clinical methods, moderate to excellent for teleradiography, good to excellent for CT scanogram and excellent for BPR. The tape measure method is a valid clinical measure of LLD whilst markerless motion analysis and the block method are not. Imaging techniques are appropriately cross-validated with the exception of BPR. CONCLUSION: The reported intra- and inter-rater reliability for most measurement techniques vary widely. The tape measure method is a valid clinical measurement of LLD. Imaging techniques have been appropriately cross-validated, with the exception of BPR, although they lack validation against a common reference technique.