Patient-matched instruments versus standard instrumentation in total knee arthroplasty: a prospective randomized study

38 patients scheduled for total knee arthroplasty were randomized to have the procedure completed with the use of either patient-specific instrumentation (PSI) or conventional intra- and extramedullary instrumentation. The purpose of this study was to compare alignment outcomes, operative time and blood loss between the two groups. Radiographic results demonstrated an average mechanical axis that was significantly closer to neutral with PSI compared to conventional instrumentation, though this did not significantly reduce the incidence of excessive malalignment (deviation in mechanical axis exceeding +/- 3 degrees).