Abstract
The biceps or the posterior deltoid can be transferred to improve elbow extension function for many individuals with C5 or C6 quadriplegia. Maximum strength after elbow reconstruction is variable; the patient’s ability to voluntarily activate the transferred muscle to extend the elbow may contribute to the variability. We compared voluntary activation during maximum isometric elbow extension following biceps transfer (n = 5) and deltoid transfer (n = 6) in three functional postures. Voluntary activation was computed as the elbow extension moment generated during maximum voluntary effort divided by the moment generated with full activation, which was estimated via electrical stimulation. Voluntary activation was on average 96% after biceps transfer and not affected by posture. Individuals with deltoid transfer demonstrated deficits in voluntary activation, which differed by posture (80% in horizontal plane, 69% in overhead reach, and 70% in weight-relief), suggesting inadequate motor re-education after deltoid transfer. Overall, individuals with a biceps transfer better activated their transferred muscle than those with a deltoid transfer. This difference in neural control augmented the greater force-generating capacity of the biceps leading to increased elbow extension strength after biceps transfer (average 9.37 N-m across postures) relative to deltoid transfer (average 2.76 N-m across postures) in our study cohort.
Highlights
ObjectivesWe expect that inadequate re-education of the nervous system to voluntarily activate the transferred muscle affects maximum elbow extension strength in both arms with biceps transfer and arms with deltoid transfer
Active elbow extension is lost or impaired in individuals who sustain a cervical spinal cord injury (SCI) at or above the C7 spinal level due to complete or partial paralysis of the triceps
Maximum voluntary activation during elbow extension was greater in arms with biceps transfer relative to arms with deltoid transfer
Summary
We expect that inadequate re-education of the nervous system to voluntarily activate the transferred muscle affects maximum elbow extension strength in both arms with biceps transfer and arms with deltoid transfer. The purpose of this study was to quantify the ability of
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