Design and Preliminary Evaluation of a New Dual-Styli and Angel-Wing Resection Guide in Limiting Tibial Varus-Valgus Angle and Slope Recuts in Kinematically Aligned Total Knee Arthroplasty

Purpose To overcome limitations using manual instruments designed for mechanical alignment to set the tibial resection plane in kinematically aligned (KA) total knee arthroplasty (TKA), this paper reports a new dual-styli and angel-wing tibial resection guide. The primary objectives were to describe the design and perform a preliminary evaluation by reporting the frequency of tibial recuts and the proportion of thinner inserts, which indicated a conservative resection thickness. A secondary objective was to determine the incidence of radiographic varus-valgus (V-V) angle and posterior tibial slope (PTS) baseplate outliers, defined as deviations greater than ±3° from preoperative values. Methods In this retrospective consecutive case series, 195 KA TKAs performed by two surgeons were included. The dual styli set the varus-valgus (V-V) angle by referencing the medial and lateral tibial sub-chondral bone. Orienting the angel wing in the saw slot of the tibial jig, parallel to the medial joint line, set the posterior tibial slope (PTS). A V-V angle recut occurred when the extension space was asymmetric by ≥ 2 mm. A PTS recut occurred when the anterior-posterior thickness difference in the medial tibial resection differed by ≥ 2 mm and an osteotome placed on the anterior and posterior rim was not parallel to the resected surface. Postoperative V-V angle and PTS deviations were measured radiographically. Results Recuts in V-V angle and PTS were not required in 93% and 95% of cases, respectively, and 91% of inserts were 10-12 mm thick. Postoperative V-V angle outliers occurred in 1 of 195 cases (< 1%), and PTS outliers occurred in 1 of 195 cases (< 1%) and these were two different patients. Conclusion Surgeons using the new dual-styli and angel-wing tibial resection guide can expect to infrequently recut the tibia and use a thinner insert. The < 1% incidence of postoperative V-V angle and PTS baseplate outliers demonstrated reliable restoration of preoperative tibial alignment in this preliminary series.