Abstract / Summary
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.