Electromyographic study on the function of tendon transfers in radial palsy

The aim of this electromyographic study was to evaluate the functional result of tendon transfers for radial palsy. Eighteen patients were compared to 16 healthy volunteers. The intramuscular emg of four muscles was recorded in parallel during extension-flexion movements of the wrist and fingers. The data were stored on FM tape and evaluated off-line. Contrary to expectations, transferred flexor muscles revealed only part of their overall emg activity during extension. Therefore, an "extensor quota" (EQ) was calculated for each muscle. It reflects its emg activity during extension as part of its entire emg activity. In non-transferred flexors EQ was low (11-27 %). High EQ values (69-91 %) were seen in genuine extensors of healthy persons. In only 6 of 18 patients did transferred flexors show an EQ equivalent to genuine extensors (≥ 69 %). Best functional results were seen in transferred flexor carpi ulnaris (median EQ 68 %). The EQ of transferred pronator teres was low (median 18 %) and minor to flexor carpi ulnaris in each patient (P < 0.05). It is concluded that in cases of radial palsy, pronator teres is not suitable for replacing extensor muscles. Superficial flexors of the fingers, however, work in synergy with extensors of the wrist. According to the Ia reflex connections involved, these muscles should be a good choice for regaining extension of the wrist.