Spinopelvic Alignment and Low Back Pain after Total Hip Replacement Arthroplasty in Patients with Severe Hip Osteoarthritis

STUDY DESIGN: Retrospective observational study. PURPOSE: We examined change in lumbrosacral spine alignment and low back pain (LBP) following total hip arthroplasty (THA) in patients with severe hip osteoarthritis (OA). OVERVIEW OF LITERATURE: Severe hip osteoarthritis has been reported to cause spine alignment abnormalities and low back pain, and it has been reported that low back pain is improved following THA. METHODS: Our target population included 30 patients (29 female, mean age 63.5 years) with hip OA who underwent direct anterior approach THA. There were 12 cases with bilateral hip disease and 18 cases with unilateral osteoarthritis. Visual analogue scale (VAS) scores for LBP and coxalgia, the Roland-Morris Disability Questionnaire (RDQ), and the Japanese Orthopaedic Association Back Pain Evaluation Questionnaire (JOABPEQ) were assessed before and after surgery. Spinal alignment metrics were measured before and after surgery. RESULTS: VAS for LBP change from preoperative to final postoperative observation was significantly improved (p <0.05), as was VAS for hip pain (p<0.001). RDQ improved significantly (p<0.01). All five domains of JOABPEQ were significantly improved (p<0.05). In terms of coronal alignment, lumbar scoliosis change from preoperative to last observation was significantly reduced (p<0.05). There were no significant changes in the sagittal alignment metrics. In addition, there was a correlation between before and after RDQ difference and before and after lumbar scoliosis difference (p<0.05). VAS for LBP (p<0.05) as well as RDQ (p<0.05) were significantly improved only in unilateral OA. Lumbar scoliosis was significantly improved in cases of unilateral OA (p<0.05), but alignment did not improve in cases of bilateral OA (p=0.29). CONCLUSIONS: The present study demonstrates improvements in VAS for LBP, RDQ, and all domains of JOABPEQ. There were also significant reductions in lumbar scoliosis and an observed correlation of RDQ improvement with lumbar scoliosis improvement. We were able to observe improvements in lumbar scoliosis and low back pain only in cases of unilateral OA. It has been suggested that the mechanism of low back pain improvement following THA is related to compensatory lumbar scoliosis improvement.