Function of the clavicular part of the pectoralis major muscle after transplantation of its sternocostal part

Muscle-sparing transplantation of the sternocostal part of the pectoralis major muscle while preserving the clavicular part of the muscle may reduce donor-site morbidity, particularly in cases where dissection of the lymph nodes of the neck has been performed. The nerve supply and motor function of the clavicular part is alleged to be preserved when the sternocostal part is transposed through the deltopectoral groove. This study aims to objectify such preservation. Muscle activity of the remaining clavicular and abdominal muscle parts was determined electromyographically, dynamometrically, and goniometrically on 17 sides in 16 patients after head and neck reconstruction. Subjective assessment was obtained by use of a structured questionnaire. The electromyogram proved preservation of innervation of 16 of 17 clavicular parts. The electromyogram of the abdominal part showed no signs of denervation on 10 sides and normal, full interference patterns at maximum voluntary effort in all patients. Selective functional testing of the clavicular part revealed decreased force in horizontal adduction in 11 out of 15 patients. Still, the isolated effect of the pectoralis major transposition on shoulder function could not be objectified statistically. Subjective evaluation yielded that shoulder disability was more likely to have been correlated with loss of trapezius muscle function. We conclude that the innervation of the clavicular part, indeed, is preserved by transposition of the sternocostal part through the deltopectoral groove. This supports the validity, effectiveness, and functional acceptability of our muscle-sparing technique of partial pectoralis major transplantation.