Pre-operative planning with X-PSI™ compared to MRI-based patient-specific instrumentation in total knee arthroplasty

X-ray-based patient-specific instrumentation (PSI) for total knee arthroplasty (TKA) is a new method for preoperative planning of TKA. This study presents the preliminary experiences with preoperative planning of TKA, comparing Zimmer Biomet's X-PSI™ with MRI-based planning for patient-specific instrumentation (PSI).

One high-volume experienced orthopedic surgeon modified and approved preoperative X-PSI™ and MRI-based PSI planning of 20 patients. Absolute differences in individual subjects of the planning by both modalities were evaluated for the following parameters: femoral- and tibial implant size, femoral resection (medial-distal, lateral-distal, medial-posterior, and lateral-posterior), tibial resection (medial and lateral), femoral flexion-extension angle, femoral- and tibial varus/valgus angle, posterior slope tibia, tibial rotation, and femoral- and tibial rotation.

The planned implant size was within one size difference between X-PSI™ and MRI-based planning of the same patient in 95 % of cases for femoral implant size and 90 % of the cases for tibial implant size. Furthermore, femoral resection levels were more comparable between both imaging modalities, whereas more variation was seen between planned tibial resection levels.

This study presents a high agreement between X-PSI™ and MRI-based PSI in implant sizing and femoral resection levels, based on measurements within the same individuals, with greater variability observed in tibial resection. Further research is needed to validate and optimise PSI for TKA.