Myoeletric activity pattern of scapular muscles after axillary lymphadenectomy in breast cancer

Purpose: to identify the pattern of myoelectrical activity of muscles from the scapular region, after axillary lymphadenectomy in breast cancer. Methods: prospective cohort study including all the women submitted to axillary lymphadenectomy for surgical treatment of breast cancer, in a breast cancer reference center, from June to August 2006. The women were evaluated before, and after 3 and 12 months from the surgery, through physical and electromyographic examinations of the serratus anterior, upper trapezius and middle deltoid muscles. Resultsesults: the patients' average age was 60.3 years old (DP +/- 14.1), and the incidence of winged scapula at the physical examination was 64.9%. At the third-months evaluation, a reduction of 28.3 mu V was observed in the myoelectrical activity of the serratus anterior muscle. At the twelveth-months evaluation and between the 3rd and the 12th month, there was an increment of 23.3 mu V and 43.6 mu V, respectively. For the upper trapezius, the increase was of 23.1 mu V at the third-months evaluation, and 23.3 mu V and 43.6 mu V between the 3rd and the 12th months. As compared to before the surgery, the evaluation of the middle deltoid muscle did no present significant differences. ConclusionS: considering muscle activity evaluated by surface electromyography, there was a decrease in the myoelectrical activity of the serratus anterior, due to lesion of the long thoracic nerve (neuropraxia), in the immediate postoperative evaluation. The increase of the mean square root of the electromyographic signal of the upper trapezius muscle, since the preoperative evaluation, suggests a muscular compensation related to the serratus anterior muscle's deficit.