Motor Nerve Preservation and Muscle Atrophy After Pectoralis Major Musculocutaneous Flap Surgery for Oromandibular Reconstruction.

Abstract

The authors investigated the clinical and histopathologic significance of medial pectoral nerve preservation/reinnervation of pectoralis major musculocutaneous flap for oromandibular reconstruction. The authors compared 13 patients treated with pectoralis major musculocutaneous flap reconstruction and 6 control patients treated by rectus abdominis musculocutaneous flap reconstruction without motor nerve restoration. Subjective awareness was scored to evaluate changes in the facial contour due to muscle atrophy, and objective evaluation was performed in few patients. In addition, the authors performed histopathologic analysis of both muscle atrophy and nerve regeneration in 20 patients from whom samples were available. Subjective awareness of changes in the facial contour induced by muscle atrophy was low among patients with nerve preservation/reinnervation, but there were objective changes at 3 months after surgery among patients who underwent nerve resection. In the patients who had medial pectoral nerve preservation or nerve restoration by nerve suture, favorable facial symmetry was retained at 5 years after surgery. Even though the motor nerve was preserved or restored, fatty degeneration and fibrosis were noted in approximately 30% of the total surface area of the muscle, and type I fibers had decreased to 36% that of control at 7 years after surgery. However, regressive changes were inhibited for 1 year after surgery; in contrast, changes corresponding to those noted at 7 years after surgery were observed by 3 months in the patients with nerve resection. Thus, the authors showed that preservation or restoration of nerves can delay muscle and have highlighted the potential benefits of this approach.