Intraoral defect coverage with muscle flaps.

PURPOSE: This study investigated whether wound healing after the use of purely muscular flaps for intraoral defect coverage is negatively influenced by insipient muscular atrophy and the absence of a covering layer.
MATERIALS AND METHODS: In an experimental study, microsurgical transplantation of muscle flaps from the anterior abdominal wall was carried out in 18 Lewis rats. A nerve anastomosis for motor reinnervation was not performed. Atrophy of the muscle flaps was determined by measuring the reduction of their size and weight after 3, 8, and 20 weeks. In the clinical part of the study, free muscle transplants from different donor regions (vastus lateralis, pectoralis major, internal oblique, and temporalis muscles) were used for defect coverage in various areas of the oral cavity. To study epithelization, punch biopsy specimens from the muscle surface were taken at periods of 2 to 4 weeks up to 6 months for histologic evaluation. Final evaluation of reconstruction results with special regard to speech, tongue mobility, mouth opening, chewing, and swallowing took place after 6 months.
RESULTS: In the experimental study, average weight loss of the muscle flaps was 67% after 20 weeks, and the remaining surface area was 71%. The number of myocytes was only about 30% compared with control muscles, and parts of the flap appeared as a thin fibrous membrane. Clinically, this atrophy led to restricted mobility in such areas as the floor of the mouth, the buccal plane, and the tongue. Muscle flaps covering solid structures such as bones or reconstruction plates adapted well to the transplant bed, and the atrophy of the muscle led to no constriction of the surrounding tissue. Atrophy also did not have a negative effect when muscle flaps were placed in the region of the pharyngeal wall. Epithelization started from the edges after 2 weeks and was concluded after 8 weeks in all transplants if no additional radiation was performed. The muscle tissue was sufficiently resistant so that infection, fistulization, and necrosis did not occur.
CONCLUSIONS: Muscle flaps undergo considerable atrophy with a cicatricial transformation and reduction of flexibility. Despite these disadvantages they can be used in the hard palate, the alveolar crest, and in the pharyngeal wall without causing functional restriction. Because of constriction of the surrounding tissues, mobile areas such as the buccal plane, the floor of the mouth, and the tongue are not suitable as sites for muscle transplants.