Abstract
The purpose was to investigate the proportion of severe load imbalance after appropriate
conventional gap balancing and analyze the intraoperative kinematics after load balancing
in cruciate-retaining (CR) and posterior-stabilized (PS) total knee arthroplasties
(TKAs). In total, 45 sensor-assisted CR and 45 PS TKAs using NexGen prosthesis were
prospectively evaluated. After appropriate conventional gap balancing, the loads at
10, 45, and 90 degrees of knee flexion were evaluated with a wireless load sensor
placed in trial implants. The proportion of severe load imbalance (medial load–lateral
load >75 lbs) was investigated. After load balancing, location of the femorotibial
contact point was investigated at each flexion angle to analyze femorotibial kinematics.
The proportion of the severe load imbalance was significantly higher in CR TKAs at
the 10 degrees knee flexion (37.8 vs. 15.6%, p = 0.031). This proportion was higher in CR TKAs than in PS TKAs at the 45 and 90
degrees knee flexion angles, but without statistical significance (31.1 vs. 15.6%,
p = 0.134 and 33.3 vs. 15.6%, p = 0.085, respectively). After load balancing, consistent posterior femoral rollback
occurred in medial and lateral compartments during 90 degrees flexion in CR TKAs (p < 0.001), but not in PS TKAs. Medial pivot kinematics was not observed in both TKA
designs. The sensor was more beneficial in CR TKAs for achieving appropriate load
balancing and consistent posterior femoral rollback compared with PS TKAs. Further
studies are required to identify target load distribution to restore ideal knee kinematics
after TKA. This study shows level of evidence II.
Keywords knee - arthroplasty - sensor - load - kinematics
