ROLE OF SOFT-TISSUE BALANCING IN COMPUTER-NAVIGATED TOTAL KNEE ARTHROPLASTY: A SYSTEMATIC REVIEW WITH META-ANALYSIS

INTRODUCTION There is a growing interest in surgical variables that are controlled by the orthopaedic surgeon, including lower leg alignment and soft tissue balancing. Since more tight control over these factors is associated with improved outcomes of total knee arthroplasty (TKA), several computer navigation systems have been developed. Many meta-analyses showed that mechanical axis accuracy and component positioning are improved using computer navigation and one may therefore expect better outcomes with computer navigation but studies showing this are lacking. Therefore, a systematic review with meta-analysis was performed on studies comparing functional outcomes of computer-navigated and conventional TKA. Goals of this study were to (I) assess outcomes of computer-navigated versus conventional TKA and (II) to stratify these results by the surgical variables the systems aim to control. METHODS A systematic search in PubMed, Embase and Cochrane Library was performed for comparative studies reporting functional outcomes of computer-navigated versus conventional TKA. Knee Society Scores (KSS) Total were most often reported and studies reporting this outcome score were included. Outcomes of computer-navigated and conventional TKA were compared (I) in all studies and (II) stratified by navigation systems that only controlled for lower leg alignment or systems that controlled for lower leg alignment and soft tissue balancing. Level of evidence was determined using the adjusted Oxford Centre for Evidence-Based Medicine tool and methodological quality was assessed using Grades of Recommendation, Assessment, Development, and Evaluation (GRADE) tool. Outcomes were reported in mean difference (MD) with 95% confidence intervals [Lower Bound 95%, Upper Bound 95%]. RESULTS Twenty-eight studies reported KSS Total outcomes in 3,504 patients undergoing computer-navigated or conventional TKA. Fifteen studies were evidence level I, five studies level II and eight studies level III. Study quality varied between low and high with most studies having high methodological quality. Patients reported better outcomes following computer navigated TKA than conventional TKA (MD 2.86 [0.96, 4.76], p =0.003), which was both seen at short-term follow-up of six months and one year (MD 5.20 [3.41, 7.00] and MD 8.46 [0.65, 16.28], respectively) and at mid-term follow-up (≥4 years) (MD 2.65 [0.96, 4.76]) (Figure 1). In studies that used computer navigation for controlling lower leg alignment, no difference in functional outcomes was seen between computer-navigated and conventional TKA (MD 0.66 [−2.06, 3.38], p =0.63, Figure 2). However, in studies that used computer navigation for controlling lower leg alignment and soft tissue balancing, patients reported superior functional outcomes following computer-navigate over conventional TKA (MD 4.84 [1.61, 8.07], p =0.003, Figure 3). CONCLUSION This is the first meta-analysis showing superior functional outcomes following computer-navigated over conventional TKA. Stratifying results by variables the systems control, superiority in functional outcomes following computer-navigated over conventional TKA were only seen in systems that controlled soft tissue balancing. This suggests that soft tissue balancing plays an important role in short-term outcomes of TKA. Manually controlling all these surgical variables can be difficult for the orthopaedic surgeon and findings in this study suggest that computer navigation may help managing these multiple variables and improve outcomes. For any figures or tables, please contact authors directly (see Info & Metrics tab above).