The Reliability of Two Dimensional Kinematic Assessment of a 45-Degree Side Step Cut

Abstract

Background:Up to 70% of all anterior cruciate ligament (ACL) injuries occur via a non-contact mechanism involving deceleration and direction change on a planted foot. Clinical screening tools analyzing movement patterns during a cutting task are reliable and valid. The Expanded Cutting Alignment Scoring Tool (E-CAST) is a reliable tool to qualitatively assess trunk and lower extremity (LE) alignment during a 45-degree side step cut (SSC). Previous works found two-dimensional (2D) kinematic analysis more reliable than qualitative assessments when evaluating jumping and squatting movements. However, there is limited evidence on the reliability of 2D assessments to evaluate SSC tasks.Hypothesis/Purpose:To determine if using 2D kinematic analysis with the E-CAST improves the tool’s reliability for evaluating trunk and LE alignment during a 45-degree SSC.Methods:25 healthy females (age 13.8 ± 1.4 years, mass 52.4 ± 9.3 kg, height 161.7 ± 6.0 cm) who regularly participated in cutting or pivoting sports were included. A repeated measures study design was used. Each subject performed three SSC trials with one trial randomly selected for analysis. Trials were recorded in the frontal and sagittal planes. Two physical therapist raters independently viewed and scored each video on two separate occasions. Videos orders were randomized and a two-week wash out period occurred between rounds. The E-CAST evaluates six movement variables (Figure 1). The assessment criteria for each variable was adapted to utilize the Dartfish motion analysis application on a smart phone (Figure 2). If a movement variable falls outside of the motion analysis definition, the subject scores a point, therefore a higher score represents poorer technique. Intraclass correlation coefficients (ICC) and 95% confident intervals (95% CI) were calculated for the E-CAST total score, and a kappa coefficient was calculated for each variable. Correlations were converted to z scores and compared for significance.Results:The cumulative intra-rater reliability was good (ICC= 0.821, 95% CI 0.687 – 0.898) and the cumulative inter-rater reliability was moderate (ICC= 0.752, 95% CI 0.565-0.859). Intra-rater kappa coefficients ranged from moderate to almost perfect for all variables (k= 0.505-0.875) and inter-rater kappa coefficients ranged from slight to good for all variables (k=0.336-0.733).Conclusion:The use of 2D kinematic analysis resulted in higher intra-and inter-rater reliability compared to the traditional qualitative E-CAST (ICC: 0.77, 95% CI 0.59-0.96 and ICC: 0.71, 95% CI 0.50-0.91), however, the difference was not significant (Zobs = -0.46 and Zobs = -0.30).