Lack of Efficacy of Bone Void Filling Materials in Medial Opening-Wedge High Tibial Osteotomy: A Systematic Review and Network Meta-analysis

Purpose: To systematically review the clinical and radiologic outcomes of isolated medial opening-wedge high tibial osteotomies with different bone void filling materials and to compare the outcomes by network meta-analysis. Methods: This systematic review and network meta-analysis included searches of Medline, Embase, Cochrane Library, Web of Science, and Scopus from inception to July 30, 2022, for clinical comparative studies comparing 2 or more bone void filling materials in patients undergoing medial opening-wedge high tibial osteotomies. We performed Bayesian random-effect network metaanalyses to summarize the evidence and applied the Grading of Recommendations Assessment, Development, and Evaluation frameworks to rate the certainty of evidence, calculate the absolute effects, and present the findings. Cochrane Risk of Bias Tool 2.0 and modified Newcastle-Ottawa Scale were used to assess the risk of bias. Results: In total, 2,755 citations were identified by our search, of which 25 eligible trials, including 10 randomized controlled trials and 15 nonrandomized comparative trials (NCTs) enrolled 1,420 participants and 6 different interventions (autografts, allografts, synthetic grafts, mixed grafts, xenografts, and without grafts). There were some concerns on the risk of bias assessment among randomized controlled trials, and the median Newcastle-Ottawa Scale score was 6 for NCTs. All fillers showed no significantly superior treatment effects when compared with unfilled group in final Knee Society Scoring, Western Ontario and McMasters Universities score, time to bone union (TBU), and loss of correction (LOC). Exceptionally, moderate-certainty evidence suggested that autograft would produce superior incidence of complete bone union (CBU) than the unfilled at postoperative 1 year (odds ratio [OR] 13.0, 95% confidence interval [CI] 1.60-95.6), whereas low- to very low-certainty evidence suggested allografts (OR 0.2, 95% CI 0.060.52) and synthetic grafts (OR 0.29, 95% CI 0.10-0.68) would result in inferior CBU. Low-certainty evidence suggested allografts would result in larger LOC angle than unfilled group (mean difference 1.1, 95% CI 0.1-2.3). As for TBU, low-certainty evidence suggested mixed grafts would take longer time to reach clinical bone union (mean difference -14.04, 95% CI -21.0 to-6.9). Conclusions: There is a lack of efficacy for different bone void filling materials to result better outcomes in Knee Society Scoring, Western Ontario and McMasters Universities score, TBU, and LOC than without graft. Although applying the autografts would produce a superior possibility of radiologic CBU than other fillers, because of the inclusion of NCTs, the overall certainty of the evidence synthesis is low. Level of Evidence: Level III, meta-analysis of Level I randomized controlled trials and Level II-III non-randomized comparative trials.