Diagnostic intra-articular injection with provocative functional testing predicts patient-reported outcomes following hip arthroscopy: a prospective investigation

The purpose of this study is to evaluate the predictive value of preoperative diagnostic intra-articular injections with formal provocative post-injection functional testing on patient-reported outcomes (PROs) following hip arthroscopy. Patients aged 14–40 with suspected labral pathology and/or femoroacetabular impingement were prospectively enrolled. Patients received a diagnostic intra-articular anesthetic injection then completed a battery of provocative physical function (PF) tests and were asked to rate the percentage of pain improvement. Patients completed PRO surveys preoperatively and up to 2 years postoperatively. PROs were compared between positive and negative injection response groups. Ninety-six patients received a diagnostic injection with provocative functional testing and subsequently underwent hip arthroscopy, 74 reported a positive injection response (≥75% improvement) and 22 reported a negative injection response (<75% improvement). The average postoperative follow-up was 12 months. Both groups experienced significant improvement in PROs postoperatively. A positive injection response was associated with greater improvements in hip outcome score, Non-Arthritic Hip Score, Patient-Reported Outcomes Measurement Information System (PROMIS) pain interference and PROMIS PF at final follow-up compared to a negative injection response. Similar improvements in modified Harris Hip Score, Visual Analog Scale hip pain and PROMIS depression were experienced between groups. These results indicate that diagnostic intra-articular hip anesthetic injection with provocative functional testing may be a valuable predictor of pain and PF following hip arthroscopy. However, patients with negative injection responses still experienced significant clinical improvement in their postoperative outcomes. As such, a negative injection response should not preclude patients from being surgical candidates, but their outcomes may be less predictable.