Reconstruction of Posterior Neck and Skull With Vertical Trapezius Musculocutaneous Flap

Stephen J. Mathes, MD, San Francisco, California, Thomas R. Stevenson, MD, Ann Arbor, Michigan

The vertical trapezius musculocutaneous flap has been successfully utilized for reconstruction in 13 patients with complex posterior skull and neck de- fects. This flap based on its vascular pedicle, the descending branch of the transverse cervical artery, provides well-vascularized tissue for coverage of de- fects related to chronic osteomyelitis, tumor extir- pation, osteoradionecrosis, and dehisced cervical la- minectomy wounds. Emphasis on flap design, including the location of the skin island, allows ade- quate wound coverage, direct donor site closure, and muscle function preservation. With its large size and wide arc of rotation, the vertical trapezius musculocutaneous flap provides reliable coverage for posterior trunk, cervical, and skull defects.

A tissue deficiency requiring flap coverage in the posterior neck and skull exists after tumor resection

or wound debridement, resulting in exposure of the spinal cord or brain. If radiotherapy is planned after extensive soft-tissue resection for tumor treatment, skin grafts may not provide stable coverage. The presence of chronic bone infection or osteoradionecrosis requires both extensive wound debridement and immediate coverage with a well- vascularized flap. The vertical trapezius musculocutan- eous flap is a reliable local flap which is generally avail- able for reconstruction of the posterior neck and skull.

MATERIAL AND METHODS Flap anatomy: The trapezius muscle is located in the

posterior inferior neck and posterior superior trunk. It has its origin from the occipital bone and spinous processes of the seventh cervical vertebra and all thoracic vertebrae and inserts into the clavicle, spine of scapula, and acromi- on. Although the entire muscle may be mobilized as a flap, the middle and lower thirds are most useful for flap transposition. This portion of the muscle is located in the posterior trunk between the scapula and vertebral col-

From the Division of Plastic and Reconstructive Surgery, University of California, San Francisco, San Francisco, California and the Section of Plastic Surgery, University of Michigan, Ann Arbor, Michigan.

Requests for reprints should be addressed to Stephen J. Mathes, MD, Division of Plastic Surgery (U- 122), University of California, San Francisco, California 94143.

Presented at the 34th Annual Meeting of the Society of Head and Neck Surgeons, New Orleans, Louisiana, May 22-26, 1988.

umn. Preservation of continuity of the superior muscle fibers between the occipital skull and lateral third of the clavicle and acromion avoids functional loss of the mus- cle.

The dominant vascular pedicle to the trapezius muscle is the transverse cervical artery, which enters the deep surface of the muscle at the base of the neck. In the posterior neck, this artery provides a descending branch that extends inferiorly in the middle portion of the muscle between the scapula and vertebral column. As noted by Cormack and Lamberty [1], the source of the dominant vascular pedicle varies, which has created confusion about its name. It may originate either from the thyrocer- vical trunk or directly from the second or third part of the subclavian artery. With a type II pattern of circulation, the trapezius muscle also receives circulation from the occipital artery entering the superior portion of the mus- cle [2]. This portion of the muscle is not mobilized for the flap design. However, the middle and lower portions of the trapezius muscle, which are elevated for flap use, also receive minor pedicles from the dorsal scapular artery and segmental branches from the posterior intercostal arteries. The muscular perforating branch from the dor- sal scapular artery penetrates through the rhomboid mus- cle and enters the trapezius muscle. This vessel must be divided to obtain adequate muscle rotation for coverage of skull or cervical defects but may be preserved when the inferior trapezius muscle is transposed over adjacent mid- line thoracic defects. Despite variation in the source of the dominant vascular pedicle, the inferior and middle por- tion of the trapezius muscle will routinely survive eleva- tion based on the descending branch of the transverse cervical artery and associated veins (Figure 1).

There are numerous vascular connections between the trapezius muscle and overlying skin. Based on these mus- culocutaneous perforating vessels, a skin island is gener- ally included with the muscle flap for cervical and posteri- or skull reconstruction. The skin island is designed over the muscle between the vertebral border of the scapula and the midline of the back. The superior margin of the skin island is generally located at the middle portion of the scapula and may extend inferiorly to a point midway between the inferior tip of the scapula and the posterior iliac spine. The width of the skin island is usually 6 cm (Figure 2). The long axis of the skin island may also be designed transversely or obliquely over the scapula, re- suiting in a vertical orientation of the skin island over the midline cervical defect after flap transposition. This de- sign reduces the useful flap arc and is not recommended for closure of defects located in the superior neck and skull base (Figure 3).

The motor nerve to the trapezius muscle, the spinal accessory, and the third and fourth cervical nerves enter the deep surface of the muscle at the posterior base of the

248 THE AMERICAN JOURNAL OFSURGERY VOLUME 156 OCTOBER 1988

Figure 1. Vascular anatomy of the vertical trapezlus musculocutaneous flap. The descending branch transverse cervical artery is the dominant vascular pedicle to the vertical trapezius muscle flap.

neck. These nerves are not disturbed during flap eleva- tion, thus denervation of the superior trapezius muscle fibers is avoided.

Clinieal applieations: The vertical trapezius muscle was used in 13 patients for immediate reconstruction of posterior skull and cervical spine defects. The causes of defects were as follows: osteomyelitis of the posterior skull in two patients; tumor extirpation in four patients; cervical vertebral osteoradionecrosis in three patients; and dehisced cervical laminectomy in four patients. The average skin island dimensions were 16 by 6 cm, with bilateral muscle flaps without skin islands used in one patient. Three flaps were used in children.

Posterior skull osteomyelitis is a rare complication following craniotomy or cranial bone devascularization from trauma or radiotherapy. Aggressive bone debride- ment followed by immediate muscle flap coverage has been effective in the management of chronic osteomyeli- tis [3]. A combined neurosurgical and reconstructive sur- gical team is required to accomplish both bone debride- ment and flap coverage. Since the patient is prone, simultaneous craniectomy and flap elevation are possible. A 6-week course of culture-specific antibiotic therapy is recommended after flap inset. At last follow-up, the two patients reconstructed with the posterior trapezius mus- culocutaneous flap maintained stable coverage without recurrence of infection.

Tumor extirpation required use of the vertical trapezi-

)

Transverse ~ ~ 1 C

Figure 2. Flap design. Vertical skin island for reconstruction of defects at skull base and posterior neck (middle). Note flap can be inset vertically to provide coverage of defects at base of skull (right) or transversely to provide coverage of entire posterior neck (left).

us musculocutaneous flap in one patient after extensive soft-tissue dissection in the posterior neck and in three patients requiring neurosurgical extirpation of recurrent spinal cord tumors. Factors including excessive scar tis- sue and prior radiation injury precluded successful clo- sure of cervical defect with adjacent skin. Although skin grafts may provide temporary coverage, the use of imme- diate flap coverage for wound closure allowed rapid treat- ment with adjuvant chemotherapy and radiotherapy in these patients.

The combination of prior neurosurgical procedures and extensive radiotherapy frequently results in instabili- ty of the posterior neck wound. In three patients, the development of osteoradionecrosis at the site of prior cervical cord tumor resections required reconstruction with the posterior trapezius musculocutaneous flap. In one of these three patients, the skin island of the vertical trapezius flap was designed obliquely over the scapula to avoid use of previously irradiated skin for wound cover- age; in another patient, a fascia lata graft was used to provide dural closure after wound debridement. Stable wound coverage was observed after posterior neck recon- struction with the trapezius musculocutaneous flap.

Four patients were treated for dehiscence with subse- quent nonhealing of cervical laminectomy wounds. Each patient underwent wound debridement and immediate reconstruction with the posterior trapezius musculocu- taneous flap. Dural leaks required primary suture at the time of flap transposition. At last follow-up, these pa- tients maintained stable wound closure after reconstruc- tion with the trapezius musculocutaneous flap.

RESULTS The posterior vertical trapezius musculocutaneous

flap was used in 13 patients with complex posterior skull and neck defects. No flap loss was observed. With one exception in which a skin graft was used, the donor site was closed directly. Preservation of the anterior superior trapezius muscle fibers with the spinal accessory motor

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MATHES AND STEVENSON

Figure 3. Flap design. Transverse skin island (left) is useful for thoracic and inferior posterior neck detects (right).

nerve (eleventh) avoided any functional disability. All patients maintained stable wound coverage with a mini- mal follow,up of 6 months.

COMMENTS Since the initial use of the vertical trapezius musculo-

cutaneous flap for osteoradionecrosis of the neck, this flap has been employed for posterior skull and neck defects in 13 patients [4,5]. Although wounds in the posterior skull and neck requiring flap coverage are relatively uncom- mon, this flap is particularly useful in this area. The flap design has been modified in two ways: First, the skin overlying the muscle is routinely designed as a skin island, allowing direct closure of the donor defect. Skin grafts adjacent to the scapula are subject to motion in the imme- diate postoperative period and may not heal as rapidly as the flap inset site. Second, the skin island is designed transversely or obliquely over the scapula for inferior neck and superior thoracic defects if the skin overlying the trapezius adjacent to the midline appears damaged from prior surgery or radiation injury, or if the long axis of the flap at the inset site is vertically oriented. In pa- tients with laxity of back skin, the skin island may extend to 7 or 8' cm in width and still allow direct closure of the donor site. Vertical orientation of the skin island is pre- ferred for large neck defects and posterior skull defects since a wider arc of rotation is possible. Since the flap will rotate 180 degrees, the width of the skin island should match the transverse extent of the skull defect or skin grafts will be required over exposed muscle flap. These modifications in flap design allow defect closure with well-vascularized muscle and overlying skin.

The technique for vertical trapezius musculocutan- eous flap coverage has been described for reconstruction of defects in the upper back, neck, and head [4-16]. The initial dissection should proceed laterally over the scapula to identify the superficial surface of the muscle. The

dissection then proceeds beneath the muscle between the scapula and vertebral column where the skin island is located. This technique avoids inadvertent separation of the inferior trapezius muscle from the overlying skin is- land. As the trapezius muscle origin is divided from the vertebral column, careful separation of the trapezius muscle from the underlying rhomboid muscles is required to avoid simultaneous elevation of both muscles. Except for defects superior to the occiput, the extent of superior dissection required for an adequate arc of rotation is usually several centimeters above the scapula. Actual identification of the descending branch of the transverse cervical artery is not required. However, division of the muscular perforating branch from the dorsal scapula ex- tending between the rhomboid and trapezius muscles is frequently required for superior neck and skull defects. Since the dominant vascular pedicle enters the muscle at the base of the lateral neck, prior injury to this pedicle is rare and was not encountered in our series of patients. If a prior radical neck dissection has been performed, or if the muscle has previously been denervated indicating possi- ble associated vascular injury, a preoperative selective arteriogram will confirm the patency of the vascular pedi- cle to the vertical trapezius flap. When these techniques were used as described, no flap loss was observed either in patients with posterior neck and skull defects or in pa- tients with anterior head and neck reconstruction.

Alternate flaps are available for posterior neck and skull reconstruction. The latissimus dorsi muscle will reach these areas; however, function preservation is not possible and the flap will not easily reach the posterior skull without extensive mobilization. Microsurgical com- posite tissue transplantation will also allow single-stage skull and posterior neck reconstruction, but suitable re- ceptor vessels are frequently confined to the anterior neck. The lateral trapezius flap and various modifications of the upper trapezius flap will reach the posterior neck but are not used due to lack of function preservation of the trapezius and more difficult access to the donor site in patients with posterior wounds, which frequently require a combined neurosurgical and reconstructive procedure [17-22]. The vertical trapezius is adjacent to these com- plex wounds, with a reliable vascular pedicle sufficiently distant from the zone of injury to allow both flap safety and minimal donor site morbidity.

In conclusion, with its large size and wide arc of rota- tion, the vertical trapezius muscle provides reliable cover- age for posterior trunk, cervical, and skull defects. The muscle has specific advantages in terms of donor site location and reliability for coverage of major cervical spine and posterior occipital skull defects. In our series of 13 patients, the vertical trapezius muscle was successfully used for reconstruction of posterior, cervical, and skull defects related to chronic osteomyelitis, tumor extirpa- tion, osteoradionecrosis, and dehisced cervical laminec- tomy wounds.

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