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Calipered Kinematic Alignment Total Knee Arthroplasty Performed With Specific Manual Instrumentation, Verification Checks, and a Decision Tree
Overview
This chapter contains discussion and video links that assist the surgeon in performing calipered kinematically aligned (KA) total knee arthroplasty (TKA) with specific manual instruments, a verification worksheet, and a decision tree. The treatment of 4726 primary TKAs performed from 2009 through 2019 with KA to restore the patient’s prearthritic joint lines regardless of knee deformity and without ligament release, by the senior author, provide the background. During this time, 4316 had retention and 410 had an excision or an unintended transection or tibial detachment of the posterior cruciate ligament (PCL). This experience evolved into a highly reproducible surgical technique that works best with the retention of the PCL. The first section discusses tips for exposing the knee. The second section describes the use of caliper measurements and verification checks that set the femoral component coincident to the patient’s prearthritic or native distal and posterior femoral joint lines with minimal flexion of the femoral component. The third section describes the use of caliper measurements and verification checks that set the tibial component coincident to the prearthritic tibial joint line. The fourth introduces a decision tree that, when followed, restores the native tibial compartment forces, laxities (except anterior laxity), and tibiofemoral and patellofemoral kinematics, thereby balancing the calipered KA TKA. The fifth section discusses the management of the severe fixed valgus deformity and the knee with flexion laxity from injury to the PCL. The educational objective is to encourage those surgeons that use manual, patient-specific navigation and robotic instrumentation to retain the PCL, not release the collateral ligaments, measure bone resections with a caliper, perform verification checks, and follow a decision tree to align and balance the calipered KA TKA reproducibly.
Tips for Exposing the Knee to Perform Calipered Kinematically Aligned Total Knee Arthroplasty
The following tips for the surgical exposure of the osteoarthritic knee might be of help when performing calipered KA TKA. The authors favor either a midvastus or a traditional medial parapatellar arthrotomy. With the knee in 90 degrees of flexion, make the incision long enough to clearly view 3 cm of femur proximal to the trochlea and 4 to 5 cm of the proximal tibia. The fat pad can either be excised or retained. The medial tibia is subperiosteally exposed deep to the superficial medial collateral ligament to view the posteromedial corner. A clear view of the posteromedial tibia is useful for setting the slope of the tibia resection to match that of the patient’s prearthritic slope when a cruciate ligament–retaining (CR) implant design is used. The iliotibial band and popliteus tendons are protected and retained. To preserve the posterior cruciate ligament (PCL) during exposure, place a single-prong Hohmann retractor lateral to the PCL. The straddling of the PCL with a two-prong retractor should be done carefully, as pushing the retractor distally can peel the PCL off the insertion on the posterior tibia. Remove all marginal, notch, and posterior osteophytes to restore the prearthritic resting length of the ligaments and full motion arc of the knee. Resurfacing the patella is preferred, as is the use of an anatomic-shaped patella implant. Because KA restores the patient’s prearthritic Q-angle and does not set the femoral component distal to the prearthritic joint line, the patella tracks well without a lateral release, with the exception of the few patients with a chronically dislocated patella. The workflow of KA is “femur first” followed by the tibial resection. The TKA is balanced by fine-tuning the varus-valgus (V-V), slope, and depth of the tibial resections, which restores the native tibial compartment forces without ligament release. ,
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