Correlation Between Improvement in Pain After Ultrasound-Guided Intra-articular Hip Injection and Outcomes After Arthroscopy in Patients With Femoroacetabular Impingement

<bold>Background: </bold>An accurate and objective criterion is needed to determine candidates who are suitable for hip arthroscopy in patients with femoroacetabular impingement (FAI). <bold>Purpose: </bold>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. <bold>Study design: </bold>Cohort study; Level of evidence, 3. <bold>Methods: </bold>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 (Delta VAS 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. <bold>Results: </bold>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 Delta VAS 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 Delta VAS 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 Delta VAS pain had a better evaluation value (AUC, 0.834; 95% CI, 0.676-0.992). <bold>Conclusion: </bold>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.