Abstract
Patient specific instrumentation (PSI) is the latest advancement in total knee arthroplasty (TKA), which claims to improve alignment, simplify the surgical process, forecasts the component size and reduces the operating time. We discuss our experience of preoperative planning using default settings and making changes where necessary.
We analysed prospectively collected data in 100 consecutive PSI knee replacements (Zimmer®) performed in our institute during the period February to August 2012. All patients underwent MRI scans of the ipsilateral hip, knee and ankle joints. From the images, Materialise® (Leuven, Belgium) provided 3D model of the knee on which preoperative planning was done using PSI software. All default plans were checked and appropriate changes were made before the senior author approved final plan for preparation of patient specific moulds.
We made 636 changes (6.36 changes per knee) preoperatively from the default settings. In only 4% of the patients, the primary cuts needed revision. Thus in 96% of the cases, the primary cuts allowed optimal alignment and gap balancing with appropriate soft tissue release. Our preoperative planning predicted 99% of femoral and 98% of tibial component sizes definitively implanted.
Our results show the importance of the surgeon's input in approving preoperative planning with this technique.
