Background: An accurate and objective criterion is needed to determine candidates who are suitable for hip arthroscopy in patients with femoroacetabular impingement (FAI). Purpose: To determine whether improvement in pain after ultrasound (US)-guided intra-articular hip injection during standardized examinations can be used to predict the outcomes of hip arthroscopy in patients with FAI. Study Design: Cohort study; Level of evidence, 3. Methods: We enrolled 119 patients with FAI who underwent US-guided intra-articular hip injection of local anesthesia during standardized examinations, carried out from May 2018 to February 2020 (within 2 weeks before hip arthroscopy). All patients had undergone a minimum of 6 months of nonoperative treatment without remission and had 2-year follow-up data. Pain visual analog scale (VAS) scores (0-10) were recorded for 7 different physical examination tests, and a total score (0 [best] to 70 [worst]) was obtained. In addition, International Hip Outcome Tool-12 (iHOT-12) and modified Harris Hip Score (mHHS) scores were recorded before hip arthroscopy and at final follow-up. According to whether patients achieved the substantial clinical benefit (SCB) on the iHOT-12, they were divided into SCB and non-SCB groups, and the improvement in VAS pain scores from preinjection to postinjection (ΔVAS pain) was compared between the 2 groups. Logistic regression analysis was used to predict the achievement of SCB, and the area under the receiver operating characteristic curve (AUC) was used to estimate the accuracy of the prediction. Results: There was a significant pre- to postoperative increase in iHOT-12 (31.6 points; P < .001) and mHHS (20.0 points; P < .001) scores, and 84 (70.6%) patients achieved the SCB. The ΔVAS pain score was significantly greater in the SCB versus the non-SCB group (16.0 vs 7.0 points; respectively; P < .001). Logistic regression analysis demonstrated an optimal cutoff value of 8.5 points for ΔVAS pain (AUC, 0.772; 95% CI, 0.687-0.858). For patients with more severe symptoms (total preinjection VAS pain score of >10 out of 70), the accuracy of the prediction for ΔVAS pain had a better evaluation value (AUC, 0.834; 95% CI, 0.676-0.992). Conclusion: Improvement in pain after US-guided intra-articular hip injection predicted the outcomes of hip arthroscopy in patients with FAI in this study, especially for patients with more severe pain.
