Kinematically aligned total knee arthroplasty using calipered measurements, manual instruments, and verification checks

Abstract

This chapter presents the philosophy of kinematic alignment (KA) and the surgical technique for setting the positions of the components using ten calipered measurements, manual instruments, and nine verification checks. The adoption of KA is increasing. Four meta-analyses, three randomized trials, and a national multicenter study showed that patients treated with KA total knee arthroplasty (TKA) reported significantly better pain relief, function, and flexion and a more normal feeling knee than patients treated with mechanically aligned TKA [1-8]. Two randomized trials that limited the severity of the preoperative knee deformities showed similar clinical outcomes [9, 10]. KA co-aligns the axes of the femoral and tibial components with the three axes of the native knee without restrictions on the level of preoperative deformities [11]. The surgical goal of restoring the native alignments of the limb, Q-angle, and joint lines unique to each patient depends on accurately setting the components coincident to the native joint lines, which co-aligns the axes. The surgical goal of restoring the laxities, tibial compartment forces, knee adduction moment, and gait to those of the native knee without ligament release balances the TKA and promotes long-term implant survival [12-19]. A description of the calipered technique of KA with manual instruments, the sequence for measuring bone positions and resection thicknesses, the intraoperative recording of these measurements on the verification worksheet (Fig. 24.1), and the use of decision trees for balancing the TKA with the medial pivot CS and CR inserts are shown (Figs. 24.2 and 24.3). Calipered measurements of the thicknesses of the femoral and tibial bone resections restore the native joint lines with high reproducibility when they are adjusted within ±0.5 mm of the femoral and tibial components after compensating for cartilage and bone wear and the 1 mm kerf from the saw cut [20-22]. Because calipered measurements are a basic surgical skill, inexpensive, and highly reliable, they should be a required verification check when performing KA with manual instruments, patient-specific guides, navigation, and robotics. Examples of treatment of patients with severe varus and valgus deformities and flexion contractures treated with kinematically aligned TKA without ligament release are shown. Finally, the reasons for the low risk of tibial component failure, low risk of patellofemoral instability, and high implant survival at 10 years after KA TKA are explained [11, 23, 24].