Summary

Development of a stair descending task for ACL-deficient patients using a portable motion analysis system

Abstract

Purpose

The aims of this study are 1) to compare the knee joint kinematics measurement from a portable motion analysis system (Opti-Knee®) with the conventional motion analysis system (Vicon®) and 2) to assess the knee joint kinematic alterations in ACL-deficient patients during a stair descending task, which is often encountered in daily activities.

Methods

Twelve ACL-deficient patients (ACLD) and 12 healthy controls (ACLN) were recruited to perform a stair descent on both sides. Each trial was captured simultaneously by both motion analysis systems, i.e. Vicon and Opti-knee. The knee kinematics between two subsequent foot strikes of the test leg was considered as a complete gait cycle. Kinematic variables from two systems for each trial were compared. For the objective one, Pearson’s correlation coefficient (R) was employed to compare two systems. For the objective 2, paired t-test was used to evaluate kinematic variables between both limbs within each subject group, whereas independent t-test was used to measure side-to-side difference between two subject groups. Statistical analysis was conducted using SPSS with significance level set at 0.05.

Results

For the objective one, the correlation of flexion-extension was high (ACLN: R=0.99±0.01; ACLD: R=1.00±0.01). The correlations were moderate in abduction-adduction (ACLN: R=0.58±0.46; ACLD: R=0.57±0.38) and in external-internal rotation (ACLN: R=0.54±0.39; ACLD: R=0.80±0.13). For the objective two, significant side-to-side difference in internal rotation of the tibia was found between ACL deficient patients and healthy controls, with six out of 12 ACL-deficient patients exhibiting higher internal tibial rotation on the injured side. No significant differences were seen in the other kinematic measures between ACL-deficient patients and healthy controls.

Conclusion

Knee joint kinematic variables in stair descent captured in two motion analysis systems have moderate to high correlation. Altered knee kinematics in ACL-deficiency can be observed by using the portable motion analysis system during stair descent.