The 10–6 Method for Tibial Preparation in Kinematically Aligned Total Knee Arthroplasty: A Technical Description and Preliminary Clinical Evaluation

Background Kinematically aligned total knee arthroplasty (KA TKA) aims to restore the proximal tibia's prearthritic varus-valgus (V-V) alignment. However, a standardized thickness to correct for proximal tibia cartilage wear has not been established. This study reports the cartilage thickness of the tibial plateau. Secondary objectives include determining the incidence of V-V recuts when a 4-mm correction for cartilage wear is applied and analyzing the V-V alignment between the preoperative tibial joint line and the postoperative tibial component. Methods Using a caliper-based optical method, maximum articular cartilage thickness was measured on 28 resections of the tibial plateaus from 28 patients undergoing unrestricted KA TKA. One surgeon corrected for cartilage wear on the tibial plateau by decreasing the resection thickness by 4 mm using a 10-mm- and 6-mm-stylus (10–6 method). Rates of necessary recuts were documented. Results The mean maximum cartilage thickness was 3.8 mm (95% confidence interval 3.4-4.2 mm), with no significant differences by sex or body mass index. The frequency of V-V recuts was 7 %. The difference in V-V orientation of the tibial component from preoperative was 1.2° (95% confidence interval, 1.7°-0.3°) Conclusions Because the mean maximum cartilage thickness of the tibial plateau is close to 4 mm, a 4-mm correction by using the 10–6-method results in a low recut rate when performing KA TKA. Surgeons using two styli with a 4-mm difference in resection depth (10–6 method) should expect to accurately restore the prearthritic V-V orientation of the proximal tibial while minimizing the need for recuts.