After division of the thoracodorsal pedicle, the lowest three slips of the serratus muscle are transferred to the facial wound. The muscle is laid superficial side down, with the neurovascular bundles on the deeper surface so that the ninth slip lies superiorly and the seventh slip inferiorly. The widely undermined skin flaps are then folded forward and the muscle brought into position, securing the seventh slip into the corner of the mouth and the eighth slip into the outer third of the upper lip. The ninth slip is split and brought out in the subcutaneous eyelid tunnel, laminating it over the previously inserted temporalis muscle turndown myofascial slips and tacking it in place with 7-0 dexon. Around the mouth, the muscle ends are secured with 5.0 vicral sutures placed as far anteriorly as possible, tacking the muscle over the previously inserted fascial slips. The secured muscle is then folded forward and the neurovascular repairs performed, anastomosing the thoracodorsal vessels to the anterior facial vessels and the nerve to the serratus to the crossfacial nerve. There is usually at least a two-to-three-to-one fascicle discrepancy between the cross-sectional diameter of the crossfacial nerve and the nerve to the serratus. The crossfacial nerve is carefully split into multiple fascicles, anastomosing the most prominent and healthiest-looking fascicle to the fascicle from the serratus muscle. Other spare fascicles are inserted into the serratus muscle to neurotize the muscle directly, or turned downward to neuronitize the anterior belly of the previous digastric muscle turnover. Again, the microneural anastomoses are performed under high magnification with fine suture material, making great effort to produce perfect anatomic alignment of the fascicular bundles and prevent wasteful regeneration by axonal escape.44 The muscle is then folded back into place, leaving the microvascular repairs on the deep surface. The scapular insertion of the muscle is stretched out to its resting length and secured to the zygomatic and temporal area with multiple rows of 4-0 nonadsorbable sutures. The facial flaps are then brought back into position and the excess skin excised if present. A sterile Doppler is brought into the operative field to absolutely confirm the location of the vascular input to the muscle and a monitoring mark placed on the cheek. This specific spot must be used in the postoperative monitoring of circulation to the muscles because false-positive signals can be picked up from other vessels in the area.

Innervation of the muscle transplant by the crossfacial nerve may take anywhere from 3 to 6 months.43 Muscle action may appear dramatically over a short period of time or may be delayed for as much as a year. Percutaneous and subcutaneous stimulation of the transplanted muscle has been recommended by some, but no standard equipment is available, and the effectiveness of such stimulation is still not confirmed.21,22

With experience from more than two dozen cases, this protocol for serratus transplantation for reanimation has resulted in strong, visible contraction in more than 85% of patients. This success has included a broad range of patients (mean age 26, range 3 to 69) and duration of paralysis (mean 9.1 years, range 1 to 27). Older patients (over 50 years) have shown a less consistent appearance of dynamic contraction, although several older patients have achieved contraction equal to that seen in children. The flap is easily dissected and no donor or recipient site complications have occurred other than hypertrophic scarring, especially in children. Great care must be taken during isolation of the separate branches of the long thoracic nerve to the lowest serratus slips.

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