Forearm muscles of man can reverse their function after tendon transfers: an electromyographic study

In patients suffering from paralysis of a major synergistic muscle group tendon transfers can be considered the therapy of choice in restoring the mobility of the affected joint(s). In order to study the mechanisms underlying the subsequent reversal of function in the transferred muscles, we have recorded the EMG of several forearm muscles in parallel and compared their activation periods with control data from healthy volunteers. Slow and fast extension-flexion movements of the wrist were evaluated. The findings demonstrated a 'new' phasic EMG activity within the transferred muscles, which correlated to their new mechanical function. However, the 'old' EMG pattern was not lost. In some muscles it was present in fast and slow wrist movements, in others only in fast ones. The results indicate that the reversal of function observed in the transferred muscles can be adjusted to meet the specific needs of the movement to be performed.