Saw cuts in unicompartmental knee arthroplasty: an analysis of Sawbone preparations

Unicompartmental knee arthroplasty (UKA) has become a frequently used treatment option for anteromedial osteoarthritis (OA) of the knee due to good clinical and functional results. However, serious complications like tibial plateau fractures have been reported. These can be associated with saw cuts during surgery. The purpose of this study was to analyse saw cuts during Sawbone preparations at instructional unicompartmental knee courses and to identify potential sources of surgical error. One hundred Sawbone preparations were performed by knee surgeons inexperienced with UKA. Sawing errors during preparation were analysed and quantified. Tibial and femoral errors can occur during preparation. At the proximal tibia three errors can be found: extended vertical cuts (A), extended horizontal cuts (B) and perforation of the posterior cortex. An ascending cut at the posterior femoral condyle (C) is possible during femoral preparation. Errors type A were found at a mean length of 2.4 mm+/-2.3 mm with a maximum value of 10.1 mm. In 18% errors of more than 4.0 mm were found. Type B errors showed an average value of 2.0 mm+/-1.7 mm with maximum values of 7.4 mm. Type C errors were found at a mean of 1.3 mm+/-1.0 mm (maximum value 5.1 mm). Our data showed that in 18% of the cases, vertical cutting errors of more than 4.0 mm occurred in inexperienced surgeons.