Abstract
The primary aim of this study was to assess the effects of total knee arthroplasty (TKA) implant design on collateral ligament elongation patterns that occur during level walking, downhill walking, and stair descent. Using a moving fluoroscope, tibiofemoral kinematics were captured in three groups of patients with different TKA implant designs, including posterior stabilized, medial stabilized, and ultra-congruent. The 3D in vivo joint kinematics were then fed into multibody models of the replaced knees and elongation patterns of virtual bundles connecting origin and insertion points of the medial and lateral collateral ligaments (MCL and LCL) were determined throughout complete cycles of all activities. Regardless of the implant design and activity type, non-isometric behavior of the collateral ligaments was observed. The LCL shortened with increasing knee flexion, while the MCL elongation demonstrated regional variability, ranging from lengthening of the anterior bundle to slackening of the posterior bundle. The implant component design did not demonstrate statistically significant effects on the collateral elongation patterns and this was consistent between the studied activities. This study revealed that post-TKA collateral ligament elongation is primarily determined by the knee flexion angle. The different anterior translation and internal rotation that were induced by three distinctive implant designs had minimal impact on the length change patterns of the collateral ligaments.
Highlights
The anterior and posterior cruciate ligaments are primary restraints in the natural knee (Boguszewski et al, 2011; Hosseini Nasab et al, 2016)
Using a novel moving fluoroscope to overcome the limitations of a stationary imaging modality, this study aims to investigate the effects of total knee arthroplasty (TKA) component design on collateral ligament elongation patterns that occur during level walking, downhill walking, and stair descent
Understanding the postoperative elongation patterns of the collateral ligaments is crucial for improving intraoperative soft tissue balancing and implant design, in order to achieve better patient satisfaction following TKA
Summary
The anterior and posterior cruciate ligaments are primary restraints in the natural knee (Boguszewski et al, 2011; Hosseini Nasab et al, 2016). After cruciate sacrificing Total Knee Arthroplasty (TKA), the passive restraint in the post-operative joint must be provided by the geometric congruency of the implant components and the surrounding soft tissues, predominantly the collateral ligaments. Collateral Ligaments Elongations in TKA through a post-cam mechanism, which constrains excessive posterior translation of the tibia relative to the femur. While both designs have been highly successful in achieving anteroposterior (AP) knee stability (Song et al, 2017), overly constrained knee motion has been observed clinically, especially regarding internal tibial rotation (Guan et al, 2017), and is a plausible cause of non-physiologic collateral ligament strain and possible pain
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