Risk Factors and Predictors for Functional Outcome and Complication Rate in Total Hip Arthroplasty through Minimally Invasive and Conventional Approaches: A Systematic Review and Meta-Regression Analysis of 41 Randomized Controlled Trials

Objective: To investigate and identify risk factors and predictors for the difference in functional outcome and complications between total hip arthroplasty (THA) through minimally invasive and conventional approaches, using a meta-regression analysis of randomized controlled trials (RCTs). Methods: A systematic review of the literature up to 31 July 2022 was performed. A meta-regression was conducted based on a random effects meta-analysis using the Hartung–Knapp–Sidik–Jonkman method. Results: A total of 41 RCTs with 3607 patients were found. The following predictors of HHS ≥ 6 months postoperatively were identified: patient age (predictor estimate = 0.14; p < 0.01), avascular necrosis of the femoral head (predictor estimate = −0.03; p = 0.04); incision length (predictor estimate = −0.82; p < 0.01). The following predictors of complication rate were identified: osteoarthritis (predictor estimate = 0.02; p = 0.02); femoral neck fracture (predictor estimate = −0.02; p = 0.02); SuperPATH (predictor estimate = −1.72; p < 0.01). Conclusions: Patient age, avascular necrosis of the femoral head, and incision length were identified as predictors of the effect size of the HHS ≥ 6 months postoperatively; and osteoarthritis, femoral neck fracture, and SuperPATH as predictors of the effect size of the complication rate. Based on these findings, we recommend that more frequent use of minimally invasive THA in elderly patients should be considered. Level of evidence I: a systematic review of all relevant randomized controlled trials. Registered in PROSPERO on 10 August 2022 (CRD42022350287).