Effect of Spinal Alignment Changes on Low Back Pain in Patients Treated with Total Hip Arthroplasty for Hip Osteoarthritis

Abstract BackgroundTotal hip arthroplasty (THA) is an established procedure for patients with osteoarthritis (OA) of the hip joint that effectively relieves pain and restores function. Because contracture of the hip joint as well as preoperative leg length discrepancy is expected to improve by the surgery, it would be reasonable to speculate that spinal sagittal alignment will also change. However, the influence of spinal alignment changes on clinical symptoms, such as low back pain (LBP), remains controversial. In this study, we aimed to evaluate the associations between spinal alignment changes and improvement in preoperative LBP after THA.MethodsFrom November 2015 to January 2017, 104 consecutive patients who underwent THA were prospectively enrolled. Whole spine X-rays were obtained preoperatively and 12 months postoperatively. The patient-reported outcomes (PROs) used were the Numerical Rating Scale (NRS) for back pain, EuroQol 5 Dimension, and Short Form-12. The presence of LBP was defined as an NRS of ≥4. Changes in spinal alignment and PROs before and after surgery were evaluated.ResultsSeventy-four (71%) patients were included in the study. The sagittal spinal parameters changed slightly but significantly; pelvic incidence (PI) decreased, pelvic tilt (PT) increased, and sacral slope decreased. Coronal spinal alignment significantly improved after surgery. Twenty-six (37%) patients had LBP preoperatively. The patients with preoperative LBP had smaller lumbar lordosis (LL), larger PT, and larger PI minus LL than those in the patients without. Fourteen (54%) of the 26 patients with preoperative LBP showed improvement, but there were no significant differences in the pre- and postoperative radiographic parameters.ConclusionAlthough preoperative LBP was likely to resolve after THR, there were no significant correlations between alignment changes and LBP improvement. The cause of LBP in patients with hip OA patients might be multifactorial.