Comment-Box Modification to Muscle-Sparing Latissimus Dorsi Design for Microvascular Anastomosis Coverage.

Free autologous reconstruction introduces added complexity to wound coverage. Flaps based on the descending branch (DB) of the thoracodorsal artery can provide a combination of muscle, skin, or bone to wound all the while providing significant pedicle length. With the placement of a microvascular anastomosis outside of a zone of injury, pedicle management is paramount and is often not considered until toward the last hours of a case when surgeon fatigue is an issue.

In areas of tenuous skin coverage such as the scalp or distal lower extremity where the defect can be part of a convex surface anatomy, traditional management such as subcutaneous tunneling or primary closure with overlying edematous, fibrotic tissue compresses the anastomosis. Skin grafting leaves the pedicle exposed, may compromise aesthetics, and carries the morbidity of an added donor site. Our “Comment Box” modification introduces additional cutaneous tissue and prompts the surgeon to consider pedicle coverage at the outset of the case.

Intraoperatively, careful measurements of the soft tissue requirements of the wound itself and the planned site of anastomosis are performed. After pedicle length requirement are ascertained, we begin harvest of the Comment Box flap (Fig. 1). The tail of the Comment Box is oriented along the anterior LD border within the cutaneous perfusion zone of the DB. The width of the flap equates initially to the width of the base of the flap, but gradually tapering to 1 cm beyond the length required for the anastomosis (Fig. 2). Flap width is constrained by what is allowed for primary closure (< 8 cm). As the DB of thoracodorsal artery perforators lie approximately 9.5–15.4 cm from the posterior axillary fold, a Comment Box–shaped flap can provide coverage for 10–12 cm long wounds and still afford a sufficiently long tail of 5–6 cm up to the posterior axillary fold.[1,2]

Fig. 1.

Diagram illustrating the application of the Comment-Box modification in the design of a muscle-sparing latissimus dorsi flap based on the DB of the thoracodorsal. This flap can be perforator-based with skin only or can include muscle as well.

Fig. 2.

Postoperative photograph following inset of a free muscle-sparing latissimus dorsi myocutaneous flap for coverage of a large anterior knee defect. Given the extensive zone of injury, microvascular anastomosis to the DB of the lateral circumflex femoral system (asterisk) was accomplished at a site distant (proximal) to the region of soft-tissue loss (red). The addition of the Comment-Box modification facilitated reliable, vascularized coverage of the pedicle in this case, where compressive edema in the distal thigh would have otherwise precluded subcutaneous tunneling and/or direct approximation of overlying soft tissues. Additional width was required medially. A full thickness skin graft was placed over folded free transferred muscle.

Given that the DB affords ~10 cm of pedicle length and can afford additional 6 cm when harvested to the axillary artery, insufficient pedicle length is rarely an issue.[3] When harvested as a skin only perforator flap, we begin dissection at the anterior border and trace perforators through muscle retrograde. When harvested as a musculocutaneous flap, we begin at the anterior border of the flap, verify perforators, identify the DB, incise the skin fully and harvest a 3–4 cm strip of muscle up until sufficient pedicle length is achieved.

To our knowledge, this is the first time this shape has been described in the literature as a method for designing and harvesting a DB muscle-sparing latissimus dorsi flap. The significance of adding a taper to the proximal end of the flap prevents the proximal vessels from being compressed while still taking advantage of the long pedicle of the latissimus dorsi. The tapered nature of the tail closes the donor site primarily without dog-ear. Although described in the context of an muscle-sparing latissimus dorsi flap, we posit that this modification is applicable to other flaps with long vascular pedicles (e.g., anterolateral thigh, radial forearm), where the site of anastomosis is located distant to that of the defect and rests in an area of convex anatomy such as the extremities and the head/neck region where closure of the defect over the anastomosis site and pedicle along with postoperative edema can potentially cause compression.