PURPOSE The latissimus dorsi muscle has many advantages as a choice for free tissue transfer. It is the largest muscle available for free transfer, has a long and consistent pedicle consisting of large-caliber vessels, and has nerve available for potential neurotization for restoration of motor function. However, removal of the entire muscle leads to functional morbidity in arm extension, adduction, and medial rotation as well as morbidity of form in distortion of the posterior thoracic silhouette.

Instead of harvesting the entire muscle, the superior portion of the latissimus can be harvested along the transverse branch of the thoracodorsal vessels while preserving the muscle origin, insertion, and the descending branch of the thoracodorsal nerve. This serves to leave the bulk of the muscle intact, preserving function and form while providing a substantial, well-vascularized muscle for free tissue transfer. This partial superior latissimus (PSL) flap has been documented in the literature for reconstruction of a variety of defects. However, its use has not been described in the pediatric population. We present a case in which a PSL free flap was used to successfully reconstruct a complex left lower extremity wound with exposed hardware in a 13-year-old boy who sustained a left leg injury in a motor vehicle collision, thus demonstrating that the PSL free flap is a safe and viable option for free tissue reconstruction in the pediatric population.

METHOD The procedure was done with the patient in left lateral decubitus position. A curvilinear incision was made along his right back from the axilla continuing inferior-medially toward the mid-back.  The anterior, superior, and posterior edges of the latissimus were identified and freed. A 10 x 15 cm portion of superior latissimus dorsi muscle was harvested based on the transverse branch of the thoracodorsal artery. The dissection was carried to the main thoracodorsal artery. The branch to the serratus as well as the descending branch was ligated, leaving the remainder of the muscle perfused by the lumbar perforators. About 70% of the latissimus muscle remained intact, including the origin and insertion. The thoracodorsal nerve was identified and an intrafascicular nerve dissection was done, separating the branch to the superior latissimus from the descending nerve branch. Once the superior latissimus was isolated on its transverse pedicle, additional length was gained by dissecting retrograde along the main thoracodorsal vessels.

The wound was debrided and dissection of the posterior tibial recipient vessels was carried out. The PSL flap was then divided and transferred to the left leg. The back donor site was closed over drains. Using the operating microscope, the vessels were prepared and the anastamoses of the vein and artery were done end-to-end with 9-0 nylon interrupted sutures. Good blood flow was observed through both the arterial and venous systems. The flap was inset and the wound closed. A split-thickness skin graft was harvested, meshed, and placed over the PSL flap and secured using chromic suture. A Prolene stitch was used to demarcate the area of arterial signal on the flap. The leg was then dressed and splinted for immobilization with open areas in the dressing for Doppler monitoring.

RESULTS Twelve month follow-up reveals a well-healed PSL free flap. The donor site reveals no distortion of the posterior thoracic silhouette. The patient has no complaints of decreased strength in extension, adduction, or medial rotation of the arm.

CONCLUSION The PSL free flap is a safe, viable option for reconstruction in the pediatric population. It has the potential of replacing the rectus abdominis muscle given its comparable size, pedicle length, and donor site preservation. Further study of the use of this flap in the pediatric population is warranted.