Abductor hallucis for monitoring lower-limb recovery after spinal cord injury in man.

STUDY DESIGN: Electromyogram (EMG) study on patients with acute spinal cord injury (SCI). OBJECTIVES: We hypothesized that subjects with mild to moderate acute SCI would have a higher probability of recovering function in intrinsic muscles of the foot compared to more proximal lower-limb muscles, based on the relative density of corticospinal tract innervation to these different motoneuron pools. SETTING: Miami and Syracuse, USA. METHODS: We conducted repeated measures of EMG during voluntary contractions from lower-limb muscles in subjects with acute traumatic SCI. For this study, analysis was restricted to those subjects who had either no recruitment (ie 'motor-complete') or limited recruitment (ie 'motor-incomplete') in any lower-limb muscle of either leg during the initial evaluation, and all of whom had converted to a motor-incomplete status in one or both legs at the time of final evaluation. Recruitment of the abductor hallucis (AbH) muscle during contraction attempts was judged as being either 'present' or 'absent', based upon the presence or absence of EMG-based volitional motor unit recruitment. RESULTS: A total of 70 subjects were included in this study. Of these, 58 had motor-incomplete injury at or rostral to the T10 vertebral level, and another 12 had injury caudal to T10. In the former group, the AbH muscle showed a recovery probability that was considerably higher than that of other lower-limb muscles. Quite the opposite pattern was seen in persons with injury caudal to T10. In these subjects, recruitment was more common in proximal muscles of the thigh (psoas and quadriceps), and least common in the AbH muscle. DISCUSSION: For persons with SCI at or rostral to the T10 vertebral level, the AbH muscle proved to be an earlier and more sensitive indicator of lower-limb contraction recovery following acute SCI compared to other lower-limb muscles. Including this intrinsic muscle of the foot as part of a neurologic assessment of muscle function after SCI should increase the test's sensitivity to preserved (or restored) supraspinal motor influence over lower-limb motoneuron pools, and is recommended.

Relationship between EMG and muscle force after spinal cord injury.

OBJECTIVE: The purpose of this study was to compare the electromyography (EMG) score during contraction of a given muscle to the independently measured manual muscle test (MMT) score for that same muscle (or muscle group), to determine whether EMG measures could serve as a reasonable approximation of muscle contraction force in persons with acute spinal cord injury (SCI). METHODS: We examined the strength of relationship between surface-recorded EMG and estimated muscle strength using the MMT in a population of 45 subjects with acute (<1 week) traumatic SCI. Eight different muscle groups were compared in each individual; measures were repeated on these subjects approximately 2 months later. A 6-point numeric index was used for assignment of EMG scores, all of which were done in a blinded fashion by 1 investigator from tape-recorded evaluations. RESULTS: Nearly all of the individual muscle comparisons led to positive and significant (P < .01) correlations between EMG and MMT scores, at both the acute and subacute time points following injury. CONCLUSIONS: These findings support the use of EMG scoring as an indicator of recovery of volitional strength following SCI in a given subject. However, caution must be used when attempting to extrapolate EMG scores to absolute forces or when comparing EMG scores among different subjects.