Kinematic alterations in the ipsilateral shoulder of patients with hemiplegia due to stroke.

OBJECTIVE: To evaluate the assumption that shoulder kinematic patterns of the ipsilateral, nonparetic shoulder in hemiplegia are similar to kinematics recorded in a healthy population.
DESIGN: Case control study of a convenience sample of ten patients with hemiplegia due to stroke in the subacute phase compared with a control group of similar age. Three-dimensional positions of the scapula and humerus were measured and expressed in Euler angles as a function of active arm elevation in the frontal and sagittal plane and during passive humeral internal/external rotation at an elevation angle of 90 degrees in the frontal and sagittal plane.
RESULTS: Compared with controls, in the ipsilateral shoulder of patients, we found both a statistically significant diminished scapular protraction during elevation in the sagittal plane (35 +/- 5 vs. 51 +/- 8 degrees at 110 degrees of humeral elevation) and humeral external rotation during arm elevation in the frontal plane (51 +/- 7 vs. 69 +/- 14 degrees at 110 degrees of humeral elevation). Maximal passive humeral external rotation was found to be impaired in the frontal (64 +/- 13 vs. 98 +/- 14 degrees) and sagittal planes (65 +/- 11 vs. 94 +/- 12 degrees). In addition, there was significantly diminished anterior spinal tilt during humeral internal rotation (-5 +/- 10 vs. -20 +/- 9 degrees) and diminished posterior spinal tilt during external rotation in the frontal plane (-14 +/- 8 vs. -3 +/- 6 degrees). Maximal thoracohumeral elevation in patients was significantly impaired (126 +/- 12 vs. 138 +/- 8 degrees).
CONCLUSION: Clear kinematic changes in the ipsilateral shoulder in patients with hemiplegia were found, indicating underlying alterations in muscle contraction patterns. The cause remains speculative. These results suggest that the ipsilateral shoulder should not be considered to function normally beforehand.