Perceived leg length discrepancy after total hip arthroplasty is associated with global spinopelvic coronal flexibility

BACKGROUND: Perceived leg length discrepancy (pLLD) is a common source of dissatisfaction after total hip arthroplasty (THA), even in the absence of significant radiographic discrepancies. While spinopelvic factors have been increasingly recognized, most previous studies have focused on sagittal alignment or lumbar mobility, and the impact of preoperative global spinopelvic coronal flexibility on pLLD has remained unclear. METHODS: We retrospectively reviewed 114 patients who underwent primary unilateral THA for osteoarthritis between January and December 2023. pLLD was assessed using a four-point scale at 6 months postoperatively. Patients who reported no perception of discrepancy were classified as the non-pLLD group, while those reporting mild, clear, or strong perception were grouped as the pLLD cohort. Preoperative spinal flexibility was measured on coronal radiographs during maximal lateral bending, calculating changes in spinopelvic angle (ΔSPA), reflecting thoracic-to-pelvic coronal flexibility, and lumbosacral angle (ΔLSA), reflecting lumbar-to-pelvic coronal flexibility. Secondary parameters included radiographic leg length discrepancy, leg lengthening, and sagittal spinopelvic alignment. Multivariable logistic regression analysis was used to identify independent predictors of pLLD. RESULTS: pLLD was reported in 47 patients (41.2%). The pLLD group exhibited significantly lower ΔSPA values (16.6° vs. 21.9°, P = 0.001) compared to the non-pLLD group, although ΔLSA did not differ significantly. Multivariable analysis revealed that lower ΔSPA (P = 0.006) and shorter height (P = 0.037) were independently associated with pLLD. Radiographic leg length discrepancy did not differ significantly between the two groups. CONCLUSION: Reduced preoperative global spinopelvic coronal flexibility, particularly diminished ΔSPA, was associated with the perception of leg length discrepancy following THA. Assessment of coronal spinopelvic flexibility may provide additional insight for preoperative evaluation and patient counseling. Further studies are warranted to better understand whether perioperative rehabilitation aimed at improving coronal spinopelvic mobility may help to mitigate pLLD after THA.