Patient-specific positioning guides versus manual instrumentation for total knee arthroplasty: an intraoperative comparison.

Traditional manual instruments for total knee arthroplasty are associated with a malalignment rate of nearly 30%. Patient-specific positioning guides, developed to help address alignment, may also influence other intraoperative factors. This study compared a consecutive series of 270 Vanguard total knee replacements performed with Signature patient-specific positioning guides (study group) to a consecutive series of 595 similar knee replacements performed with manual instrumentation (control group). The study group averaged 16.7 fewer minutes in the operating room (p < .001), utilized tibial inserts that averaged 0.4 mm thinner with a smaller proportion of "thick" tibial inserts (14-18 mm) (p < .001), and required fewer transfusions (p = .022). The Signature-derived surgical plan accurately predicted correct femoral and tibial component sizes in 86.3% and 70.3% of the cases, respectively. These rates increased to 99.3% and 99.2%, respectively, for accuracy to within one size of the surgical plan, similar to published values for manual instrumentation.