Introduction Functional microvascular muscle transplantation (FMMT) has met with less success in situations involving traumatic major soft tissue and nerve loss because of the less than optimal recipient wound bed and target motor nerve. We report an innovation to the staged reconstruction of a traumatized upper extremity with a FMMT. We also discuss how this innovation optimized the recipient bed and target motor nerve.

Case Report A 37-year-old-man sustained a crush-degloving injury of his forearm. Surgical exploration revealed an 18 x 22cm soft tissue defect, which included the dorsal and volar compartments as well as the radial nerve proximal to the lateral epicondyl. The patient underwent latissimus muscle transplantation to obtain primary wound cover. Next, the thoracodorsal nerve measuring 10cm was repaired to the mixed motor-sensory radial nerve stump, which was debrided 2cm proximal to healthy appearing fascicles well outside the zone-of-injury.

Between the 6th and 8 th weeks after muscle transplantation, the latissimus began to contract at the proximal forearm. These contractions strengthened, and by the 13 th weeks, the patient could voluntarily contract the entire muscle. At that time, the patient had no active wrist or digit extension, and injury to the volar forearm precluded tendon transfer.

Eight months after latissimus transplantation, the contra-lateral gracilis muscle was harvested to restore finger and wrist extension. On elevation of the latissimus muscle, an avascular septo-alveolar plane similar to that between two healthy muscle bellies could be developed with gentle finger dissection. The latissimus was elevated as a bipedicle flap and the gracilis was drawn into this plane. The throacodorsal-obturator nerve repair was performed as close as possible to the gracilis muscle.

At eight weeks the patient had regained active extension of his wrist and fingers. Seven months after FMMT the patient had excellent extension or the wrist and digits. Strength was 4+ based on the Medical Research Council (MRC) grading scale.

Conclusion The simple technique of innervating the muscle used for coverage of a large upper extremity wound helped overcome the potential limitations introduced by traumatic injury. The latissimus muscle excursion not only signaled the appropriateness of the target motor nerve but also eventually created a recipient bed comparable to the plane between two healthy muscles. The thoracodorsal nerve provided enough graft length to both allow initial proximal repair outside the zone of injury and eventual distal repair as close as possible to the functional muscle, decreasing reinnervation time.