Free Transfer of Latissimus Dorsi Flap
The latissimus dorsi is the largest muscle in the body, up to 20 × 40 cm, allowing coverage of extremely large defects. In spite of its size, no significant donor functional deficit results from removal of the muscle. It is the largest flap that can be harvested on a single pedicle, and it can even be combined with the serratus, scapular, or parascapular flaps to create a flap complex that can cover massive wounds.1 In the normal population, the muscle is quite thin (less than 1 cm thick), allowing it to be draped over irregular surfaces with ease. It represents one of the workhorse flaps in upper extremity reconstructive microsurgery. When reinnervated using the thoracodorsal nerve, the latissimus can be used as a functional muscle to restore hand function of both finger flexion and finger extension. The free microsurgical transfer of the latissimus dorsi flap was first described in 1979 by Watson.2
The free microsurgical transfer of the latissimus dorsi flap can be used in reconstruction of extensive upper extremity defects.3
It can be used in reconstruction of contaminated wounds and osteomyelitis.
Can be useful in augmenting blood supply to areas of deficiency, for example, in postradiation tissue necrosis, diabetes mellitus, and areas of skin necrosis secondary to vasculitis.
The entire musculocutaneous flap can be transplanted as a functional unit to provide finger or elbow flexion.
It can cover large defects in hand and forearm with extensive wound, where the target tissue is beyond the arc of rotation of a pedicled flap (crush degloving injuries, farm injuries).
It can be used in severe posttraumatic upper extremity contracture, such as Volkmann ischemic contracture.
The ideal candidate is a motivated patient with supple joints, stable shoulder, and stable wrist, dedicated to participation in a lengthy postoperative rehabilitation program.
There is no specific age range or time limit. The flap can be used for acute and chronic reconstruction.
The flap cannot be used in the presence of infection in the donor or recipient area.
In patients with paraplegia, loss of this muscle may seriously weaken upper extremity function (e.g., crutch walking and bed-to-wheelchair transfer) by affecting extension of the humerus, rotation, and adduction.
Similarly, in patients with poliomyelitis or other neuromuscular diseases, loss of this muscle will seriously weaken pelvic stability.
A relative contraindication is an individual with a high-demand upper extremity that requires unrestricted shoulder motion.
The surgeon must verify good shoulder motion and stability of the donor site.
Due to the vascular consistency of the flap, angiogram is not necessary.
Doppler probing for the vessels may be used.
The design of the flap is done according to the size and shape of the defect as well as the volume or thickness required.
The latissimus dorsi muscle takes origin on the iliac crest inferiorly and the thoracolumbar fascia posteriorly near the midline.
It inserts into the humerus, where it acts as a humeral adductor and internal rotator.
The posterior axillary fold is made up of the most superior aspect of the muscle.
The nerve supply is via the thoracodorsal nerve, a branch of the posterior cord of the brachial plexus. The nerve closely accompanies the thoracodorsal artery.
The latissimus muscle blood supply is via the subscapular artery, a branch of the axillary artery ( Fig. 39.1 ).
The subscapular artery sends off a circumflex scapular branch posteriorly and then becomes the thoracodorsal artery.
The subscapular artery can be from 2 to 5 mm in size, while the thoracodorsal artery ranges from 1.5 to 4 mm. The vena comitans is usually slightly larger, from 3 to 5 mm.
The pedicle has an average length of 9 cm (6–16 cm) and can be approached directly by dissecting the latissimus from the axilla, or it can be found by following the undersurface of the muscle in a distal-to-proximal approach.
Because the artery divides in the substance of the muscle, the muscle can be split longitudinally to form a bilobed or two-tongued flap.
The muscle is also supplied by perforators from the thoracic intercostal and lumbar arteries, which allow it to be used as a pedicled flap that can resurface posterior defects. These vessels are quite small, with short leashes, and are not typically used for microsurgical reconstruction.
Latissimus dorsi musculocutaneous flap. A much larger flap, 20–22 × 33–35 cm, can be harvested, but the donor site must be grafted, increasing the morbidity ( Fig. 39.3a–c ).
Latissimus dorsi osseous musculocutaneous flap. When the 10th rib is included, an osseous segment (10–13 cm) can be obtained from the 10th rib.
The latissimus dorsi musculocutaneous flap can be divided into two flaps corresponding to the transverse (medial) and descending (lateral) branches of the thoracodorsal artery. This split flap concept was first described by Tobin.7
The latissimus dorsi musculocutaneous flap can be transplanted on a single vascular pedicle (the subscapular artery and vein), with the lower three slips of the serratus anterior muscle or with the scapular-parascapular flap.
Because the transverse (medial) and descending (lateral) branches of the thoracodorsal artery course on the deep surface of the muscle throughout their length, and because secondary branches course vertically and form an interconnecting plexus between these two branches, the muscle can be thinned horizontally from its superficial surface.
Immediate refinement of the flap is done before fixation to the recipient site.