Effect of Surgical Technique, Implant Design, and Time of Examination on Contact Kinematics: A Study of Bicruciate-Stabilized and Posterior-Stabilized Total Knee Arthroplasty

Background Bicruciate-stabilized (BCS) total knee arthroplasty (TKA) designs attempt to approximate natural knee mechanics. Multiple surgical techniques, including gap balancing (GB) and measured resection (MR), have been developed to provide optimal implant positioning and soft-tissue balance. The goal of this study was to determine the effect of surgical technique on BCS TKA contact kinematics. Secondary goals included investigating the change of kinematics over time and comparing BCS TKA kinematics to a posterior-stabilized (PS) design. Methods The study included the BCS-GB, BCS-MR, and PS-MR groups. The BCS-GB and BCS-MR groups underwent weight-bearing radiostereometric analysis (RSA) for multiple knee flexion angles at 3 months and 1 year post-operatively, whereas the PS-MR group was imaged at 1 year post-operatively. The medial and lateral contact kinematics were determined from implant poses. Results There were no differences in BCS TKA kinematics between the GB and MR techniques. There were differences in the mid-flexion ranges when comparing the 3-month and 1-year kinematics of the BCS design, however they were less than 1.5 mm. Differences existed between the kinematics of the BCS and PS designs at all flexion angles for the medial condyle (P < 0.0006) and at 0° of flexion on the lateral condyle (P < 0.0001). Conclusion Contact kinematics for a BCS design were similar for both surgical techniques, suggesting both are appropriate for this design. Small, likely clinically insignificant differences were found between 3 month and 1 year kinematics. The BCS TKA kinematics differed from the PS design; however, it is unclear whether these differences improve clinical outcomes.