Relating movement control at 9 upper extremity segments to loss of hand function in people with chronic hemiparesis

Loss of hand function in people with hemiparesis is a major contributor to disability poststroke. To use the hand for functional activities, a person may need control of the more proximal upper extremity segments to position and orient the hand with respect to the environment and may need control of the fingers to manipulate objects within the environment. The purpose of this project was to investigate how movement control at proximal, middle, and distal upper extremity segments contributed to loss of hand function in people with chronic hemiparesis.

32 patients with hemiparesis (avg 21.4 months postlesion) were studied making isolated movements of shoulder flexion, elbow flexion, forearm pronation/supination, wrist flexion/extension, and individual finger flexion using 3D kinematic techniques. For each segment, 3 variables were obtained: how far a segment could move (active range of motion [AROM]), how well a segment could move by itself (individuation index), and how well a segment could remain still when it was not supposed to move (stationary index). Hand function was measured with a battery of clinical tests, and principal components analysis was used to create a single hand function score for each patient from the test battery. Correlation and regression analyses were used to examine relationships between segmental movement control and hand function.

Movement control at all 9 segments of the upper extremity was related to hand function. Of the 9 segments, the thumb tended to have the weakest relationship with hand function. Of the 3 measures of movement control, AROM had strong relationships with and predicted the most variance in hand function (73%). Most of this variance was shared across segments, such that, for AROM, there were no unique contributions provided by proximal, middle, or distal segments.

These data support the idea that loss of movement control covaries across segments and that loss of hand function is due to loss of movement control at all segments, not just at distal ones.