Patient‐specific Instrumentation Affects Rotational Alignment of the Femoral Component in Total Knee Arthroplasty: A Prospective Randomized Controlled Trial

OBJECTIVE: To evaluate whether patient‐specific instrumentation (PSI) improve the accuracy of femoral component rotational alignment with respect to conventionally‐implanted total knee arthroplasty (TKA). METHODS: Twenty‐four patients were randomized to receive a TKA implanted with PSI or conventional instrumentation. Implant orientation was compared on Computed Tomography (CT). Surgical time, recuts, and component size variations from planning were recorded. Preoperative and postoperative Oxford knee score and visual analogue scale were compared to assess clinical outcomes. RESULTS: Femoral components implanted with patient‐specific instrumentation were aligned with greater external rotation than those implanted with conventional instrumentation (P = 0.022). No significant differences were found in surgical times, number of recuts, and clinical outcomes. Surgeon modifications from the planned size were necessary in 58% of PSI cases. CONCLUSION: Femoral components implanted with PSI had greater external rotation than with conventional instrumentation. Surgeons must carefully evaluate component sizes when using PSI, both in planning and during surgery.