Purpose: Diagnostic hip injections are often used to confirm intra-articular pathology prior to arthroscopic treatment for femoroacetabular impingement (FAI). However, little is known whether the type of response correlates with the post-operative functional outcomes. The purpose of this study is to document the ability of a diagnostic hip injection to predict short-term functional outcomes following arthroscopic surgical management.
Methods: A prospective cohort of 52 patients diagnosed with FAI who had an intra-articular hip injection prior to arthroscopic surgery was evaluated. A pain diary was used during the 2 weeks after hip injection to document response. In addition, the modified Harris Hip Score (mHHS) was administered preoperatively and 6 months post-operatively to assess functional outcomes. The relationship between response to an intra-articular hip injection and mHHS scores 6 months after FAI surgery was evaluated.
Results: Overall, 42 of 52 (81 %) patients diagnosed with FAI achieved pain relief from the hip injection. Outcomes according to mHHS scores improved significantly at the 6-month follow-up visit (19 points, 95 % CI 15-24, p = 0.001). The therapeutic utility of the hip injection suggested that lack of pain relief predicted a lack of functional improvement following arthroscopic surgery.
Conclusion: In this study, the data suggests that a positive response from an intra-articular hip injection is not a strong predictor of short-term functional outcomes following arthroscopic management of FAI. However, a negative response from an intra-articular hip injection may predict a higher likelihood of having a negative result from surgery.