Does the removal of pectoralis minor impair the function of pectoralis major?

Abstract

The treatment of long-standing unilateral facial palsy with cross-facial nerve graft and free pectoralis minor muscle flap to the face has been the elective choice for more than 300 patients during the last 20 years at Mount Vernon Hospital in Northwood, United Kingdom. In this study, the authors assessed the residual donor-site morbidity in the chest after the procedure. During the second stage of the operation, the medial and the lateral pectoral nerves are divided at a proximal level from the plexus. Due to the common innervation shared by the two pectoral muscles, a consequent change in pectoralis major muscle function can be expected, but so far no study has been carried out to find out whether or not this occurs. The authors have performed a subjective and an objective study on a voluntary sample of 38 patients previously operated on for facial palsy with pectoralis minor muscle transfer. Cosmetic and functional outcomes were recorded. The subjective evaluation was obtained through a questionnaire. The objective evaluation was obtained through physical examination (inspection and palpation). The following quantitative parameters were determined: thickness of the muscle, arm muscle circumference, power produced at contraction, and muscle fiber activity. Subjectively, six patients (15.8 percent) reported a reduction in the force of the muscle, and 10 patients (26.3 percent) noticed a change in muscular thickness at the site of the operation. Objectively, the results of the electromyogram were almost normal in all of the muscles sampled (17 patients). Occasionally, minor changes from the normal pattern were seen in the lower half of pectoralis major. The dynamometer adduction test showed a significant reduction in the force developed on the operated side when it was the dominant side (p = 0.02), whereas no difference was shown in the group of patients who underwent operations on the nondominant sides (p = 0.18). The pectoral fold and the arm muscle circumference did not show any difference between the side operated on and the nonoperated side. This clinical study confirms that the use of the pectoralis minor muscle as a neurovascular free flap for face reanimation is associated with a low morbidity at the donor site. The authors believe that the medial pectoral nerve has a marginal role in pectoralis major muscle innervation in contrast to the classic anatomic descriptions and some of the positions of the official surgical literature regarding the actual function of this nerve.