The radiological outcomes of patient-specific instrumentation versus conventional total knee arthroplasty

Purpose The aim of this study was to investigate the post-operative radiological outcomes of patient-specific instrumentation (PSI) surgery versus conventional total knee arthroplasty (TKA). Methods Sixty patients scheduled for a primary TKA were prospectively divided into PSI or conventional technique. Coronal and sagittal radiographic long limb films were taken post-operatively. The accepted values for normal alignment were 180 degrees +/- 3 degrees for hip-knee-ankle angle; 90 degrees +/- 3 degrees for coronal femoral component angle or coronal tibia component angle; 0 degrees to 3 degrees flexion for sagittal femoral component angle and 0 degrees to 7 degrees posterior slope for sagittal tibia component angle. Results For hip-knee-ankle angle, there were 21 % more outliers in the PSI group compared to the conventional group (p = 0.045). Most of these outliers had valgus deformity in the PSI group and varus deformity in the conventional group (p = 0.045). For implant placement, there was no difference in the proportion of outliers between the two groups. There was also no difference in the duration of surgery. Conclusions This study showed that PSI surgery is associated with a larger proportion of outliers for lower limb alignment. PSI surgery as an alternative to conventional TKA is not advisable. Level of evidence II.