Abstract
Introduction
Optimized tibial tray rotation during a total knee replacement (TKR) is critical for tibiofemoral congruency through full range of motion, as it affects soft tissue tension, stability and patellar tracking. Surgeons commonly reference the tibial tubercle, or the “floating tibial tray,” while testing the knee in flexion and extension. Utilization of embedded sensors may enable the surgeon to more accurately assess tibiofemoral contact points during surgery.
Methods
The malrotation of the tibiofemoral congruency when utilizing the mid to medial 1/3 of the tibial tubercle for tibial rotation was evaluated in 50 posterior cruciate ligament-retaining TKRs performed by an experienced, high-volume surgeon. Sensors were embedded in the tibial trials; the rotation of the tibial tray was defined, and the femoral contact points in each compartment were captured. The surgical procedure was performed to size and then appropriately rotate the tibial tray. The anterior medial tray was pinned to control anterior-posterior and medio-lateral displacement, and allow internal and external rotation of the tray. With the capsule closed and patella reduced, the knee was reduced with trial implants. The femoral contact points and medial-lateral soft tissue tension were documented. Patellar tracking and changes in soft tissue tension were also documented.
Results
In 60% (n = 30/50) of cases, further external rotation (average 5 degrees) was required. No further rotation was required in 10% (n = 5/50), and 30% (n = 15/50) required further internal rotation for optimized congruency. Patellar tracking and changes in soft tissue tension based on rotation showed parallel center of load in medio-lateral compartments and equalized intercompartment pressures resulting in optimized balance of the knee.
Conclusions
Utilizing the tibial tubercle for optimized tibial tray rotation and femoral congruency was only adequate in 10% of cases. The use of sensors to define the femoral contact points on the tibia enabled the surgeon to adjust the tibial tray to optimize tibiofemoral congruency. Mal-rotated trays negatively affected soft tissue tension and patellar tracking.
