Assessment of upper extremity muscle function in persons with tetraplegia.

The objective was to investigate the actual level of muscle function impairment in tetraplegic persons and, inextricably related to this, the possibilities to compensate function loss using new muscle coalitions. In this cross-sectional group study, 20 persons with a cervical spinal cord injury (SCI) at segmental levels C5C6 or C7C8 and 10 control persons participated. Activity from 21 upper extremity and trunk muscles was recorded during standardised gross upper extremity task performance. No substantial differences in main activation patterns were found between C7C8 and control subjects. In contrast, main activation patterns in C5C6 persons showed an absence of selectivity, which may be explained by the participants activating every controllable muscle in an attempt to perform maximally. In order to identify more intricate differences in muscle activation between control and C7C8 persons a fine motor function task may be necessary. Muscle activation patterns during arm task performance were stable in all three groups.