[Effect of preoperative timing for ultrasound-guided intra-articular hip anesthetic injection on post-arthroscopy infection and inflammation in patients with femoroacetabular impingement].

<b>Objective:</b> To investigate the relationship between preoperative ultrasound-guided intra-articular local anesthetics injection at different time points and postoperative infection risk and inflammatory response after hip arthroscopy in femoroacetabular impingement(FAI). <b>Method:</b> This retrospective observational study enrolled FAI patients who underwent hip arthroscopy surgery at the General Hospital of the People's Liberation Army from May 2017 to October 2023. According to the time interval between intra-articular injection and the surgery, the patients were divided into four groups: injection time≤30 days prior to surgery, injection time between 30-90 days prior to surgery, injection time>90 days prior to surgery, and non-injection group. The temperature and peripheral blood inflammation indicators of patients within one week before surgery and during hospitalization after surgery were collected. The international hip joint score (iHOT-12), visual analogue scale (VAS) of pain and the modified Harris Hip Score (mHHS) before and within 12 months after surgery were collected. The postoperative infection rates, clinical scores, temperature and inflammatory markers between groups were compared. <b>Results:</b> A total of 425 patients were included, with 264 males and 161 females, aged (37.2±12.9) years. There were 152 cases in the≤30 d group, aged (36.9±12.5) years; 58 cases in the 30-90 d group, aged (41.4±13.2) years; 28 cases in the>90 d group, aged (37.3±12.0) years; and 187 cases in the non-injection group, aged (36.2±13.0) years. No acute and chronic infections were found in the enrolled patients, and 8 cases of suspected acute infections were found: 5 cases (2.7%) in the non-injection group, 2 cases (3.5%) in the 30-90 d group, 1 case (3.6%) in the>90 d group, and 0 case in the≤30 d group, and the difference in the proportion of patients with suspected acute infections among the various groups was not statistically significant (<i>P</i>=0.061). There were 17 patients with maximum body temperature≥38.0 ℃ on postoperative day 1, 9 (4.8%) in the non-injection group, 2 (7.1%) in the > 90 d group, 1 (1.7%) in the 30-90 d group, and 5 (3.3%) in the≤30 d group. There were 143 patients with mildly elevated body temperature (37.0-38.0 ℃), 74 (39.6%) in the non-injection group, 10 (35.7%) in the>90 d group, 17 (29.3%) in the 30-90 d group, and 42 (27.6%) in the≤30 d group, and the difference in the proportion of the number of people with different degrees of fever among the groups was not statistically significant (<i>P</i>=0.180). The peripheral blood leukocyte level was 10.6 (8.5, 12.2)×10⁹/L in the≤30 d group, 9.7 (7.8, 10.5)×10⁹/L in the 30-90 d group, 8.9 (8.0, 10.7)×10⁹/L in the>90 d group, 10.0 (7.9, 11.3)×10⁹/L in the non-injection group, and peripheral blood leukocytes in the≤30 d group were significantly higher than those in the other three groups (all <i>P</i><0.05). The differences in neutrophil ratio, neutrophil-to-lymphocyte ratio, C-reactive protein, erythrocyte sedimentation rate were not statistically significant among the groups after the surgery (all <i>P</i>>0.05). The iHOT-12, VAS of pain and mHHS scores of patients in all groups improved at 12 months after surgery when compared with the values before the operation (all <i>P</i><0.001). <b>Conclusion:</b> Preoperative ultrasound-guided intra-articular hip anesthetic injection performed with standardized sterile technique does not increase postoperative infection risk or inflammatory response in FAI patients.