A Dynamic Knee Function Scoring System for Anterior Cruciate Ligament Injuries Based on Normative Six-of-Freedom Gait Pattern

Abstract

Abstract Background: Anterior cruciate ligament (ACL) injuries are common, but traditional examinations primarily focus on static assessments, lacking the ability to evaluate dynamic knee stability. Therefore, a dynamic knee function scoring system is needed. Purpose: This study aimed to propose a dynamic scoring system based on a large sample of normative six-degrees-of-freedom (6-DOF) gait kinematics and validate its correlation with conventional outcome measurements when assessing ACL-injured knees. Methods: A total of 500 healthy Chinese participants were recruited to establish a large dataset. 83 patients with isolated unilateral ACL injury were included for preoperative assessments. An infrared navigation three-dimensional portable knee motion analysis system was used to collect data on the 6-DOF of both knees while walking on a treadmill. A novel 6-DOF scoring system was developed based on the large sample data using the dynamic time warping algorithm. The Spearman correlation coefficients (ρ) were calculated between the 6-DOF score and the Lysholm score, 2000 International Knee Documentation Committee (IKDC) subjective score, and Tegner’s activity scale. Results: The 95% confidence intervals (CI) for abduction/adduction, internal/external rotation, flexion/extension, anterior/posterior translation, medial/lateral translation, and proximal/distal translation in the 500 healthy participants were as follows: 10.07 ± 4.04°, 15.13 ± 4.85°, 60.56 ± 6.07°, 1.79 ± 0.75 cm, 1.09 ± 0.42 cm, and 1.58 ± 0.54 cm, respectively. The Spearman correlation coefficients (ρ) between the 6-DOF score and the assessment scores were as follows: ρ = 0.375 (p < 0.001) for the Lysholm score, ρ = 0.273 (p = 0.016) for Tegner’s activity scale, and ρ = 0.145 (p = 0.208) for the 2000 IKDC subjective score. Conclusion: Significant correlations were found between the 6-DOF score and the Lysholm score as well as Tegner’s activity scale. Therefore, the 6-DOF score has the potential to provide comprehensive and meaningful information on the dynamic knee function and stability of ACL-injured patients.