A prospective cohort study on the effect of low back pain in patients undergoing total hip arthroplasty

Background: Evaluation of patients with hip arthritis for total hip arthroplasty (THA) may be confounded by concomitant low back pain (LBP). Purpose: To study the prevalence and outcome of LBP in THA patients. To evaluate the outcome of THA in patients with dysfunctional low back pain (DLBP). Methods: In patients undergoing THA, low back pain was assessed with the Roland Morris Disability Questionnaire (RMDQ) and Numerical Pain Rating Scale (NPRS) scores preoperatively and 1 year postoperatively. Patients were categorised as suffering from DLBP if their RMDQ score was >4. Hip function was assessed using the modified Harris Hip Score (mHHS). Results: 26 of 79 (33%) patients had DLBP before THA. At 1 year follow-up, 19 of them either no longer suffered from DLBP (RMDQ ⩽ 4) or at least had improvement in their RMDQ scores ⩾ 5 suggesting discerning clinical improvement. The mean NPRS scores for LBP at one year also improved (1.5 vs. 0.7, p < 0.01). The mean mHHS at 1 year in patients without DLBP was significantly higher than those with DLBP (85.15 vs. 75.81, p = 0.003) implying that patients without DLBP had better hip outcomes following THA. Conclusions: DLBP improves considerably after THA. The outcome of THA may be adversely affected by the presence of DLBP.