Patient-specific instrumentation (PSI) was developed to improve the accuracy of component positioning in total knee arthroplasty (TKA). A meta-analysis of level I and level II studies was performed to determine if PSI improves the mechanical alignment of the leg compared with conventional instrumentation (CI) in TKA. Seven studies met inclusion criteria evaluating 559 patients undergoing TKA. Mean coronal alignment was within 1 degree of neutral mechanical alignment in both groups (PSI, 0.78 degrees; CI, 0.81 degrees). There were fewer outliers in the PSI group (21.1%) than in the CI group (23.2%), but this was not statistically significant (p = 0.59). On the basis of the data from this analysis, PSI does not significantly improve the postoperative mechanical alignment of the limb after TKA. Moreover, PSI does not decrease the number of outliers compared with CI.
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