Surgeon Assessment of Gapping Versus Kinetic Loading Using Intraoperative Sensors During TKA

Purpose : The purpose of this study was to determine if using a sensor-equipped tibial insert would reduce medial (MED) and lateral (LAT) gapping and create more equivalent compressive forces in the MED and LAT compartments. Methods : 7 orthopedic surgeons each performed bilateral TKA on complete lower extremity cadaveric specimens. Left TKA was performed first without the use of the instrumented tibial insert. With trial components placed, the patella was reduced and joint capsule closed with towel clips. Surgeons performed varus and valgus stress tests on each knee and the mm of MED and LAT gapping were recorded. Compressive forces in the MED and LAT compartment were measured at 10°, 45°, and 90° of flexion. Sensor-assisted TKA was then performed on the right knee and compressive forces and gapping were again recorded. MED, LAT, and total mediolateral (ML) gapping and MED and LAT compressive forces were compared between conventional TKA and sensor-assisted TKA with paired t-tests. Results : Sensor-assisted TKA resulted in significantly reduced MED (1.2 vs. 1.9 mm, p<.001), LAT (0.8 vs. 1.4 mm, p = 0.003), and total ML gapping (2.0 vs. 3.4 mm, p<.001). There were no differences in the MED and LAT compressive forces between conventional and sensor-assisted TKA. However, sensor-assisted TKAs demonstrated greater MED compartment forces as the knee was flexed whereas conventional TKAs had greater LAT forces. Conclusions : Sensor-assisted TKA significantly reduced MED and LAT gapping with the knee in 20° of flexion. Future clinical studies are needed to determine the most appropriate compressive forces in the MED and LAT compartments.