Back Reconstruction

Defects of the back requiring reconstruction are caused by either a congenital or acquired problem.

Congenital

Spina bifida occurs in approximately 1 in 800 births and is the most common birth defect of the central nervous system. Children with spina bifida are born with incomplete fusion of the vertebrae dorsally. It can be classified further as occulta and cystica.

Spina bifida cystica further has the following 4 variants: meningocele, myelomeningocele, syringomyelocele, and myelocele.

Neural elements have intact epithelial covering in all the variants except myelocele. Reconstruction with stable and well-vascularized cover is indicated to prevent epithelial tears and subsequent infection and to preserve existing functional neural tissue. Most of these defects can be closed easily and are addressed by neurosurgeons. However, approximately 25% of defects require plastic surgical expertise.

Giant congenital pigmented nevi can occur over the posterior trunk. The lifetime risk of developing melanoma in these patients may approach 15%. Complete prophylactic excision of the nevi usually is recommended in infancy and early childhood. Most of the giant nevi can be excised and reconstructed using tissue expansion. Multiple large expanders are placed cephalad and caudal to the nevus. Careful design of the flaps to include paraspinal perforators makes them more vascular and reliable.

Acquired

Acquired posterior trunk defects result from trauma, infection, burns, radiation, tumor resection, postoperative wound dehiscence, or pressure ulcers.

Postoperative infections in the back can produce complex wounds with muscle necrosis, deep dead space, and exposed hardware, bone, and dura. The morbidity associated with these wounds can include prolonged hospital stays, multiple operations, meningitis, and osteomyelitis. Conventional treatment of wound infections (eg, debridement, antibiotic irrigation, intravenous antibiotics, delayed closure) is not always successful. In this setting, the application of soft-tissue transfer techniques successfully may achieve early wound closure, coverage of exposed hardware, and decreased rates of chronic osteomyelitis.

Reconstructive goals are to protect underlying vital structures, including the spinal cord, and to provide functional support.

A literature review by Chieng et al indicated that the use of flaps in patients who develop wound complications following spinal surgery increases the chance of hardware salvage in these patients. ^[1]

The reconstructive surgeon must be aware of the anatomy of the back muscles prior to embarking on a complex reconstruction. The blood supply and innervation of some of the back muscles and fascial layers of the posterior trunk are discussed.

The superficial fascia of the back is anatomically continuous with the superficial fascia of the ventral abdominal wall. It easily is identified and elevated from the deeper lumbodorsal (thoracolumbar) fascia overlying the paraspinous muscles.

The deep fascia of the back is a dense fibrous layer, attached above to the superior nuchal line of the occipital bone; in the mid line it is attached to the ligamentum nuchae and supraspinal ligament and to the spinous processes of the vertebrae below the seventh cervical vertebra; below, it is attached to the crest of the ilium.

The trapezius is a flat, triangular muscle arising from the occiput to the lowest thoracic spine. It inserts along the spine of the scapula and across the acromioclavicular joint to the tip of the clavicle. Its blood supply is from a branch of the thyrocervical trunk and from the transverse cervical artery, the latter of which extends so far inferiorly in the paravertebral area that a muscle flap based on this vessel may have a very long excursion. The trapezius is innervated by the spinal accessory nerve (cranial nerve XI).

The latissimus dorsi muscle takes its axial origin as far inferiorly as the iliac crest and lower 6 vertebrae. It inserts onto the inferior surface of the intertubercular groove of the humerus and receives its innervation from the thoracodorsal nerve. Despite its great power as an adductor and medial rotator of the shoulder, its sacrifice appears not to result in much functional disturbance in nonathletes. The dual blood supply of the latissimus can be exploited in reconstructive surgery. The entire muscle, with a large paddle of skin, can be carried on the thoracodorsal artery. In turn, segmental portions can be carried on individual paraspinal perforating vessels, preserving function of the muscle.

The serratus anterior muscle arises from the anterior surface of the 7th-10th ribs and inserts on the deep surface of the medial scapula. Its blood supply is from the lateral thoracic vessels and branches of the thoracodorsal vessels. The long thoracic nerve lies on the surface of the serratus and enters it through segmental branches.

Paraspinous muscles also are known as erector spinae muscles, which include the longissimus, iliocostalis, and spinalis portions. They are located deep to the latissimus dorsi muscles and the thoracolumbar fascia. Their origin is from the spinous processes and iliac crest inferiorly, and insertion is into the posteromedial aspect of the ribs superiorly.

The gluteus maximus is a large quadrilateral muscle forming the prominence of the buttocks. It originates from the gluteal line of ilium and sacrum and inserts into the greater tuberosity of the femur and the iliotibial band of the fascia lata. It has dual blood supply from superior and inferior gluteal arteries. It is supplied by the inferior gluteal nerve. The gluteus maximus is a powerful hip extensor and is not considered expendable.

No specific or absolute contraindications exist to reconstructive procedures. Some types of reconstruction may not be suitable or appropriate in patients who smoke, those with diabetes, those with paraplegia, and those who are obese.