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Neurovascular Anatomy of the Split Latissimus Dorsi Muscle Flap for the Purpose of Smile Restoration

Background: Patients with facial paralysis experience functional and cosmetic problems related to facial muscles inactivity. Free micro neurovascular functional muscle transfer offers the best prospect for restoring both voluntary and emotional facial expressions. The transferred muscle replaces some of the paralyzed muscles, mainly the lip elevators. If the lip depressors are not replaced, asymmetry of the mouth persists. This study investigates splitting of the latissimus dorsi muscle to replace lip elevators and depressors in different vectors to reanimate the smile. Methods: We studied 10 latissimus dorsi muscle specimens obtained from five fresh cadavers. Intramuscular dissection for the branches of the nerve and blood vessels was performed. A radio-opaque lead oxide mixture was injected to obtain radiograms. Splitting of the muscle was done parallel to the muscle fibers and neurovascular branches. The nerve pedicle was split into two fascicles by intrafascicular dissection along its whole length. Results: We split all muscle specimens into neurologically independent segments with each segment containing one of the main branches of the neurovascular bundle. Splitting of the whole length of the thoracodorsal nerve into two branches was performed in all specimens. Conclusions: This study suggests that the latissimus dorsi muscle is suitable for segmental splitting into completely independent muscle slips that can be rotated into entirely different vectors to reanimate the smile, including both upward and downward pulls on the oral commissure. Disclosure: The authors have no financial interest to declare in relation to the content of this article.