[Analysis of related factors for unexpected positive intraoperative cultures in aseptic hip revision surgery]

Objective: To investigate the related factors for unexpected positive intraoperative cultures (UPC) in patients undergoing aseptic hip revision and the long-term prosthesis survival rate in such patients. Methods: A retrospective cases series analysis was conducted in 397 patients who underwent aseptic hip revision surgery at the Department of Orthopaedics, First Affiliated Hospital of Xinjiang Medical University from January 2012 to December 2021. There were 225 females and 172 males with an age (M(IQR)) of 58(23) years (range:21 to 89 years) and a body mass index (BMI) of 25(6) kg/m² (range:15 to 39 kg/m²). Based on the culture results of intraoperative specimens, patients were divided into culture-positive group (32 cases) and culture-negative group (365 cases). The clinical data were analyzed including gender, age, BMI, preoperative C-reactive protein, preoperative erythrocyte sedimentation rate, American Society of Anesthesiologists(ASA) classification, preoperative urinary bacteria, preoperative hypoproteinemia; comorbidities of diabetes mellitus, anemia, chronic obstructive pulmonary disease, cerebral infarction; history of allergy to antibiotics, smoking, drinking, previous prosthetic dislocation, previous surgical intervention; and time from symptom onset to admission, duration of surgery, etc. A univariate analysis was performed by Mann-Whitney U or χ² test and the independent risk factors were identified by including the independent variables with P<0.20 in the univariate analysis in a logistic regression analysis of dichotomous variables. The study outcomes were defined as :(1) re-surgical treatment for any reason; (2)symptoms of infection such as sinus and incision seepage; (3) persistent excessive hip pain.The Kaplan-Meier survival curve was plotted using the study outcome of any cause as the endpoint event, and the log-rank test was used to compare the 10-year survival rate of the prosthesis in the culture-negative group with that in the culture-positive group. Results: Univariate analysis showed statistically significant differences between the culture-negative and culture-positive groups when comparing gender, BMI, ASA classification, and preoperative urinary bacterial results (χ²=2.368, P=0.124;χ²=-1.648, P=0.098;χ²=14.128, P=0.003; and χ²=7.384, P=0.007). Logistic regression analysis showed that male, ASA classification Ⅳ, and positive preoperative urinary bacteria were independent risk factors for the development of UPC during aseptic hip revision(OR=2.35,95%CI:1.08 to 5.36,P=0.040;OR=37.32,95%CI:1.80 to 1 810.63,P=0.030;OR=4.11,95%CI:1.40 to 11.12,P=0.012). The follow-up time of the 397 patients included in this study was 70 (134) months (range:12 to 146 months). The Kaplan-Meier survival curves showed that the 10-year survival rates of the prostheses in the culture-negative and culture-positive groups were 95.7% and 75.0%, respectively. There was no statistically significant difference in the 10-year survival rate comparing the two groups (P=0.661). Conclusions: UPC is more likely to occur in patients undergoing hip revision due to noninfectious factors in those who are male, have positive preoperative urinary bacteria, and have an ASA classification of Ⅳ. Intraoperative specimen culture results (negative or positive) do not affect 10-year prosthesis survival rate after hip revision.