3-D Evaluation of Abnormal Upper Extremity Joint Coupling Post-Stroke.

Paretic arm exhibited significantly higher joint coupling ratio (JCR) values compared to the non-paretic arm for all seven upper extremity degrees of freedom, both in- and out-of-plane.

• Study included 18 individuals post-stroke.
• Seven UE DOFs were evaluated: isolated shoulder, elbow, and wrist joint movements.
• JCR was calculated for both in-plane and out-of-plane joint coupling.
• Abnormal coupling was evident in the paretic arm across all measured DOFs.

The combined in- and out-of-plane joint coupling regression model explained significantly higher variance in functional task performance deficits compared to models using only in-plane or only out-of-plane joint coupling.

• The combined model explained up to 33.8% of variance in stroke-induced functional deficits.
• Functional task performance was assessed using an object transfer task.
• Outcome variables explained included movement duration, hand trajectory smoothness, trunk displacement, hand movement extent, and peak velocity time.
• Hierarchical regression analysis was used to compare model contributions.

A novel experimental procedure using 3D motion capture was developed to evaluate both in-plane and out-of-plane joint coupling across seven upper extremity degrees of freedom.

• The procedure captured isolated shoulder, elbow, and wrist joint movements.
• A method to calculate the in- and out-of-plane joint coupling ratio (JCR) for seven UE DOFs was introduced.
• Functional task performance was also evaluated during an object transfer task.
• Previous studies had predominantly evaluated UE joint coupling only within the plane of motion (in-plane).

Out-of-plane joint coupling, representing unnecessary joint movements outside the plane of motion, was identified as a previously underexamined contributor to post-stroke upper extremity impairment.

• Prior work focused predominantly on in-plane joint coupling and its effect on functional task performance.
• The authors note that minimizing out-of-plane movements across all UE degrees of freedom is essential for coordinated movements.
• Including out-of-plane coupling in the regression model increased variance explained in functional deficits beyond in-plane coupling alone.

Stroke-induced abnormal joint coupling contributed to deficits across multiple functional movement parameters during an object transfer task.

• Functional parameters affected included movement duration, hand trajectory smoothness, trunk displacement, hand movement extent, and peak velocity time.
• Both in-plane and out-of-plane JCR values contributed to explaining these deficits.
• The study used hierarchical regression analysis to isolate contributions of in-plane versus out-of-plane coupling to functional deficits.