The surgeon plays an important role in size planning with patient specific instrumentation for total knee replacement.
Component position and sizing in total knee replacement (TKR) could be improved by patient specific instrumentation (PSI). The purpose of the study was to evaluate the reliability of the manufacturer plan in predicting final component sizes for TKR.Forty-five TKRs were prospectively enrolled and data on component size were recorded from the initial manufacturer’s proposal, the final plan modified after surgeon’s and from the actually implanted prostheses.Pre-operative modifications were required in more than 50% of the cases, with the tibial tray size requiring more frequent changes. The surgeon’s planning showed a significantly higher accuracy than the manufacturer’s one regarding tibial tray size (p < 0.05) but not femoral components size (p: n.s.). Careful evaluation by an experienced knee surgeon is recommended when planning TKR with PSI.