Anatomical and technical considerations in surface electromyography.

Despite the technical and clinical limitations of surface EMG, it is essential in the physical medicine and rehabilitation field. Surface EMG has evolved from a secondary means of clinical assessment to a primary factor in determining and predicting clinical outcomes. Computer models of electrical muscular activity are currently implemented to assist in designing proper instrumentation and electrode with optimum dimensions. These models could be expanded to simulate pathological motor functions to help understand functional abnormalities even before clinical interventions. Currently, several groups all over the world are investigating the use of multichannel surface EMG. This technological advancement would have an immediate impact on several medical fields. For instance, tendon transfers are performed to improve function in peripheral nerve injury, brachial plexus lesion, spinal cord injury, and cerebral palsy. There are potential uses for multichannel surface EMG, both preoperatively and postoperatively. Preoperatively choosing the muscle for transfer has been largely based on clinical grounds. Multichannel surface EMG could give a more objective database to assess prognosis and determine which muscle to transfer. Postoperatively, multichannel surface EMG can provide a systematic way of assessing changes in gross muscle topography caused by the tendon transfer. Other applications of multichannel surface EMG would be for bony and soft tissue deformity from arthritis, heterotopic ossification, amputation, or burns. Multichannel surface EMG would allow clinicians to get a broader picture of the skeletal muscle activity despite the fact that it is physically impossible for the patient to assume the anatomic position used for traditional isolated electrode placement. Individuals with physical disabilities that affect their ability to assume the usual posture for electrophysiologic testing may benefit considerably from development of multichannel electrophysiologic testing. Patients with abnormalities of tone from various causes such as stroke, traumatic brain injury, and cerebral palsy are at times evaluated with kinesiologic EMG to assess motor control. Multichannel surface EMG could potentially give us much greater insight into motor control disorders.