Factors predicting manipulation under anaesthesia after total knee replacement

Introduction Manipulation under anesthesia (MUA) is a standard and effective treatment to correct stiffness and improve range of motion (ROM) following total knee arthroplasty (TKA). Delayed MUA has been associated with increased rates of revision surgeries and infections. Early MUA has been shown to double the mean gain in flexion compared to delayed interventions. To identify candidates early and effectively, this study aimed to evaluate various risk factors influencing the likelihood of undergoing MUA after TKA using statistical analysis. Methods Data from 1973 to 2023 were collected from TriNetX, reviewing 245,567 unique patients. Current Procedural Terminology (CPT) codes identified those who had undergone TKA and MUA. ICD-9 and ICD-10 codes identified preoperative comorbidities and complications. Univariate and multivariate analyses assessed the association between preoperative risk factors and MUA likelihood. Independent sample t-tests, Levene's test, and effect size analyses examined age differences between MUA and non-MUA cohorts. The study included 6,867 patients (2.8%) in the MUA cohort and 238,700 patients (97.2%) in the non-MUA cohort. Results Among 245,567 TKA patients, 6,867 (2.8%) required MUA. Univariate analysis showed significant associations with age < 65 (OR = 2.49 [CI: 2.37-2.61], p < 0.001), Black race (OR = 2.04 [CI: 1.91-2.18], p < 0.001), SCD (OR = 2.96 [CI: 2.01-4.35], p < 0.001), and cannabis-related disorders (OR = 2.38 [CI: 1.29-4.38], p = 0.004). Multivariate analysis confirmed significant predictors: age < 65 (OR = 2.39 [CI: 2.26-2.53], p < 0.001), Black race (OR = 1.65 [CI: 1.51-1.81], p < 0.001), SCD (OR = 1.51 [CI: 1.00-2.26], p = 0.048), and female sex (OR = 1.13 [CI: 1.07-1.18], p < 0.001). The average age was 61.94 years in the MUA cohort and 67.09 years in the non-MUA cohort, with a significant mean difference of 5.14 years (p < 0.001). Conclusion Our study demonstrates that younger age, female sex, and Black race are significant predictors of MUA after TKA. Additionally, novel risk factors such as peripheral artery disease (PAD), chronic kidney disease (CKD), and sickle cell disease (SCD) were identified, with SCD notably increasing the likelihood of MUA. This study uniquely highlights reduced likelihoods of MUA in PAD and CKD patients, contrasting with prior literature. The significant association of SCD with MUA, alongside these novel findings, emphasizes the value of demographic and comorbidity-specific predictors in refining postoperative risk stratification.