Utility of Ultrasound-Guided Anesthetic Intra-articular Injection to Estimate the Outcome of Hip Arthroscopy in Patients with Femoroacetabular Impingement Syndrome.

Objective: To investigate the effectiveness of ultrasound (US) guided intra-hip joint injection to estimate the outcome of hip arthroscopy in patients with femoroacetabular impingement (FAI) syndrome.

Methods: Patients with FAI syndrome (n = 60) were prospectively enrolled in our study. Before hip arthroscopy, a mix of 4 mL 2% lidocaine and 4 mL 1% ropivacaine were injected into the hip joint under the guidance of US. The clinical efficacy of the intra-articular injection was evaluated by comparing the visual analog scale (VAS) and international hip outcome tool 12 (iHOT-12) results before and after the injection. The outcome of hip arthroscopy was evaluated by iHOT-12, the modified Harris hip score (MHHS), and the patient's satisfaction 12 months after the operation. The outcome of intra-articular injection and hip arthroscopy were compared. Factors related to the outcomes of hip arthroscopy were evaluated. The correlation between the efficacy of intra-hip joint injection and arthroscopy was evaluated.

Results: The VAS of patients decreased from 11.3 ± 7.7 to 3.3 ± 4.5, and the iHOT-12 increased from 52.1 ± 23.2 to 84.1 ± 18.1 after intra-articular injection (all P < 0.001). The iHOT-12 score increased from 52.1 ± 23.2 to 78.9 ± 19.2, and the MHHS increased from 66.5 ± 6.8 to 81.6 ± 8.1 after hip arthroscopy (all P < 0.001). The satisfaction rate of arthroscopy, including very satisfied and effective patients, was 93.3%. Multi-variable logistic regression showed that only iHOT-12 improved value after injection was included in the regression formula of satisfaction, with the β of -0.154, standard error of 0.071, Wald value of 4.720, and OR of 0.857 (95%CI 0.746-0.985) (P = 0.03). Significant correlation was detected between iHOT-12 scores after intra-articular anesthesia and at 12 months after arthroscopy (r = 0.784, P < 0.001). So was the iHOT-12 improved value (r = 0.781, P < 0.001) and the iHOT-12 improved ratio (r = 0.848, P < 0.001). If we had performed arthroscopy only on patients with post-injection iHOT-12 score improvement ≥10, the satisfaction rate of arthroscopy would have increased to 96.6%.

Conclusions: US-guided intra-hip joint injection may provide a feasible way to estimate the outcome of hip arthroscopy in patients with FAI syndrome, and could be used as a method for indication selection of hip arthroscopy.