Purpose: The diagnosis of hip osteoarthritis is often complicated by co-existing pathology in the knee and spine, and mismatch between clinical and radiological signs. Temporary pain relief from a local anaesthetic injection into the hip joint has been reported to help localise symptoms, reducing the risk of unnecessary surgery being performed. We hypothesize that good surgical outcome is predicted by good analgesia following diagnostic injection, and that alternative pathology is present when there is no response to injection.
Methods: Data were analysed from a prospective database of 163 consecutive patients who underwent diagnostic hip injection for possible osteoarthritis. We recorded result of injection and whether hip arthroplasty was performed. A good outcome to surgery was defined as subsequent pain relief without significant residual symptoms.
Results: A total of 138 patients were suitable for inclusion in the study. Fifty-eight patients had hip arthroplasty following a good response to diagnostic injection. Of these 54 had a good outcome following surgery (93%). There was also a quantitative improvement in pain and function in these patients as measured by 1 year post-operative and pre-operative Harris hip scores (P < 0.0001). A total of 44/49 patients had no surgery following no response to injection. A clear alternative diagnosis to hip osteoarthritis was made in 40 of these patients (91%).
Conclusion: Diagnostic ultrasound-guided local anaesthetic injection of the hip joint is a useful test in confirming hip pathology. Complete relief of hip pain following intracapsular injection of local anaesthetic is associated with good surgical outcome following joint replacement.