Intraoperative Analysis of Collateral Ligament Elongation Patterns by Coronal Plane Alignment of the Knee Classification Using Augmented Reality Navigation in Japanese Osteoarthritic Knees

Background: Elongation, defined as the 3-dimensional distance between ligament attachment sites, is a useful metric for evaluating ligament function. However, intraoperative assessment of elongation patterns in osteoarthritic (OA) knees during total knee arthroplasty (TKA) remains limited. Purpose: To analyze the intraoperative elongation patterns of the medial and lateral collateral ligaments (MCL and LCL) in OA knees using augmented reality (AR) navigation, according to the Coronal Plane Alignment of the Knee classification. Methods: A total of 100 OA knees undergoing TKA with AR-based navigation were evaluated. Real-time 3-dimensional elongation of the MCL and LCL was recorded throughout the full range of motion. A ≥10% change in ligament length was defined as significant. Elongation patterns were analyzed by Coronal Plane Alignment of the Knee type. Results: The MCL remained relatively constant during knee flexion, whereas the LCL shortened. Normal elongation patterns (stable MCL with LCL shortening) were observed in 83.3% of type I, 79.2% of type II, 75.0% of type III, and 100% of type IV and V knees. However, atypical patterns were also noted in some type I and II knees. Conclusions: Most OA knees demonstrated ligament elongation patterns similar to those of healthy knees. AR navigation enabled real-time, quantitative 3-dimensional assessment of ligament dynamics and may support individualized intraoperative soft tissue evaluation during TKA.