Patient-specifi c instrumentation does not improve radiographic alignment or clinical outcomes after total knee arthroplasty

Background and purpose — Patient-specifi c instrumentation (PSI) for total knee arthroplasty (TKA) has been introduced to improve alignment and reduce outliers, increase effi ciency, and reduce operation time. In order to improve our understanding of the outcomes of patient-specifi c instrumentation, we conducted a meta-analysis. Patients and methods — We identifi ed randomized and quasi- randomized controlled trials (RCTs) comparing patient-specifi c and conventional instrumentation in TKA. Weighted mean differ- ences and risk ratios were determined for radiographic accuracy, operation time, hospital stay, blood loss, number of surgical trays required, and patient-reported outcome measures. Results — 21 RCTs involving 1,587 TKAs were included. Patient-specifi c instrumentation resulted in slightly more accu- rate hip-knee-ankle axis (0.3°), coronal femoral alignment (0.3°, femoral fl exion (0.9°), tibial slope (0.7°), and femoral component rotation (0.5°). The risk ratio of a coronal plane outlier (> 3° deviation of chosen target) for the tibial component was statis- tically signifi cantly increased in the PSI group (RR = 1.64). No signifi cance was found for other radiographic measures. Opera- tion time, blood loss, and transfusion rate were similar. Hospital stay was signifi cantly shortened, by approximately 8 h, and the number of surgical trays used decreased by 4 in the PSI group. Knee Society scores and Oxford knee scores were similar. Interpretation — Patient-specifi c instrumentation does not result in clinically meaningful improvement in alignment, fewer outliers, or better early patient-reported outcome measures. Effi - ciency is improved by reducing the number of trays used, but PSI does not reduce operation time.