Dorsal Spinal Wounds

The technique for closure of dorsal spinal wounds is similar in the cervical and thoracolumbar regions. In procedures involving dural openings, whether intentional or inadvertent, every attempt at a watertight dural closure should be made. Nonabsorbable #6-0 polypropylene sutures generally are used, with or without a fascial autograft, or commercially available dural substitute allografts. The suture line is covered with a layer of fibrin glue, or, more recently, with the sealant DuraSeal (Covidien, Waltham, MA). Where there is concern regarding the quality of closure, a spinal drain should be placed. Failure to achieve adequate dural closure may lead to a variety of complications, including meningitis, arachnoiditis, pseudomeningocele formation, and cerebrospinal fluid (CSF) leakage from the wound. In the latter case, it is imperative to return to the operating room, readdress the CSF leak, and avoid the temptation to simply reinforce the skin closure.

After dural closure, inspection of the deep tissues, including the resected vertebral bone edges, epidural contents, and surrounding musculature, should be performed to ensure that meticulous hemostasis has been achieved. Failure to do so may lead to postoperative hematomas, which can become symptomatic due to compression of neural structures. Epidural bleeding should be controlled with bipolar cautery or local hemostatic agents, the exposed bone edges waxed, and muscular bleeding likewise controlled with cautery. Irrigation with hydrogen peroxide often is performed in cases without dural violation, particularly in large wounds, to aid in hemostasis. Once this has been achieved, some surgeons also cover exposed dura with a local hemostatic agent.

One of the central tenets of wound approximation is the use of an orderly layered closure to optimize wound healing by eliminating dead space to reduce the risk of fluid collection and infection. After the dura has been closed and hemostasis achieved, attention should be turned to the layered closure. After extensive spinal procedures, a large potential dead space exists that is amplified in patients who have undergone laminectomy at multiple contiguous levels. The paraspinal musculature is approximated with a few large absorbable #0 sutures, with care taken not to strangulate the tissue, which can cause local muscle necrosis and severe postoperative pain. Fascial closure is performed carefully with interrupted #0 absorbable sutures. In cases of reoperation, or where radiation is anticipated, nonabsorbable braided #0 suture material is recommended. A tight closure of the fascia is recommended to reduce dead space as well as prevent possible CSF leakage. This layer also may serve as a barrier to the development of a deep infection from a superficial wound infection. Placement of a drain into the epidural and/or subfascial space should be considered in those patients with large wounds, after vascular tumor removal, after instrumented fusion procedures, and after operations for trauma. These drains diminish the occurrence of hematomas and seromas that hamper wound healing^7,8 and that also can cause neurologic deficit with neural element compression. If CSF is observed accumulating in the suction canister, the drain must be removed immediately to prevent a persistent CSF leak and complications associated with CSF overdrainage.

In larger individuals, it may be necessary to close the subcutaneous tissue in multiple layers owing to its thickness. For this, #2-0 Vicryl suture is commonly used, and the membranous superficial fascia, most easily identified in the lumbar subcutaneous tissue,^1,2 should be the target of reapproximation. The dermal tissue is reapproximated next with inverted interrupted #2-0 or #3-0 suture material, taking care to align the edges of the wound in the rostral-caudal as well as dorsal-ventral dimensions. It is important to produce wound eversion with closure of this layer to ensure the skin layer will have minimal tension after its closure, thereby improving its ability to heal. Scars from properly everted wounds tend not to widen with time, and the ridge of everted tissue always settles to normal.⁹ The skin is reapproximated with either monofilament suture, staples, or, in some cases, skin adhesive application.

Ventral Spinal Wounds

Closure of wounds from ventral or lateral thoracolumbar approaches also should adhere to the basic principles of wound closure. Closure or patching of CSF leaks, meticulous hemostasis, placement of drains when appropriate, and orderly layered closure with emphasis on a watertight fascial reapproximation should be performed. These operative approaches often are performed by vascular, thoracic, or general surgeons, and the spine surgeon should participate in the subsequent closure of these wounds.

The reapproximation of anterior cervical spinal wounds, while much less tedious than posterior closures, still must be tackled in meticulous fashion. As with posterior wounds, CSF leakage should be formally addressed and the leak closed if possible. With or without closure, spinal drainage at the end of the case is recommended, and will save the surgeon several agonizing sleepless nights. The spine surgeon should be fastidious with hemostasis, because postoperative hematomas have the potential to be life threatening due to airway compromise. Placement of a drain is not a substitute for adequate hemostasis. The musculature of the neck is not reapproximated, unless it was intentionally divided, which occasionally may be the case with the omohyoid. The watertight fascial closure for the anterior neck is the platysma. It often is easily identified in young patients, but it may be quite atrophied and difficult to discern in elderly patients. In obese patients, it often is infiltrated with adipose tissue, which occasionally makes its identification difficult. The platysma often is closed with #3 Vicryl suture and is followed by reapproximation of the dermis with inverted #3 Vicryl sutures as well. Some surgeons skip deliberate closure of the dermis and instead proceed to a subcuticular closure with an absorbable monofilament suture. Skin adhesives or Steri-Strips may be placed at this point, depending on surgeon preference.

In the presence of wound dehiscence or infection before attempted closure, extensive debridement is necessary. In cases in which radiation therapy has been received preoperatively or is anticipated postoperatively, closure of the fascia should be accomplished with nonabsorbable #0 or #2 monofilament or braided nylon. Wound closure in general is uncomplicated in the cervical and lumbar region because of the thickness of the muscle layer and the lordotic curvature of the spine. An incision in the upper thoracic spine is subject to horizontal tensile forces caused by shoulder movement, and this area is notorious for dehiscence in as many as 30% of patients with cancer or spinal implants.¹⁰ In addition to spinous process excision, a figure-8 brace may be worn postoperatively to reduce tensile forces across the vertical incision. Drains usually are left in place for 2 days, or until the drainage is less than 50 mL per 8-hour shift. Sutures are not removed until at least 2 weeks postoperatively.

When the quality of the tissue present at the wound edge or the amount of tissue damaged or missing precludes primary closure, one must consider either a skin graft or some other type of flap closure. Split-thickness skin graft can be used for closure in rare instances in which the underlying soft tissue is adequate to protect underlying structures and has adequate circulation to support survival of the skin graft. Modern electric-powered and nitrogen gas pressure–powered dermatomes make the harvest of high-quality split-thickness autograft a simple and predictable procedure. Graft may be taken from any suitable donor site, usually at a thickness between 0.012 and 0.015 inches. This is applied to the wound bed. Fixation of the graft for 4 to 5 days prevents movement between the graft and the recipient bed and usually results in graft acceptance.

Trapezius Muscle and Myocutaneous Flaps

Because of its length, extending from the superior nuchal line to the spinous process of T12, and its width, from one acromial process to the other, the trapezius muscle is suitable for rotation, with or without overlying flaps of skin (Fig. 122-1). The blood supply to the trapezius muscle is via the type II vascular pattern characterized by one dominant vascular pedicle with other minor contributing pedicles.^11–13 The principal pedicle consists of the dorsal scapular artery, which constitutes the descending branch of the transverse cervical artery. The latter arises from the subclavian artery or thyrocervical trunk. The dorsal scapular artery courses caudally, medial to the scapula and ventral to the rhomboid muscle, supplying these muscles as well as the latissimus dorsi and trapezius muscles and eventually anastomosing with the suprascapular and subscapular arteries and some of the intercostal arteries. The minor pedicle consists of branches of the occipital artery perfusing the rostral segments of the muscle.^7,14 With careful dissection, the caudal pole of the trapezius muscle can be dissected from the spinous processes and underlying latissimus and rhomboid muscles. Careful attention must be paid to preserve the integrity of its blood supply, which can be observed on the ventral aspect of the caudal and medial fibers.

FIGURE 122-1 Normal anatomy of the trapezius and latissimus dorsi muscles (left). Trapezius and reverse latissimus dorsi flaps (right) are used for coverage of defects over the upper thoracic and lumbar spines, respectively. Mobilization of these flaps requires preservation of their blood supply.

Trapezius flaps, with or without attached cutaneous pedicles, can be used to repair defects overlying the kyphotic curvature of the thoracic spine. Spinal wound closure can be a challenge in patients who are being treated for thoracic spinal metastases. The apex of the thoracic kyphosis is most prone to dehiscence in patients whose wound healing capability has been compromised by chemotherapy and radiation therapy. Radiation therapy contributes to impairment of circulation by virtue of endothelial swelling and subintimal fibrosis. This results in an obstructive endarteritis with the subcutaneous tissue being replaced by dense fibrosis.⁷ Shoulder movement further contributes traction on the skin edges, increasing their predilection for separation and dehiscence. This is further expedited in cases of wound infection or diabetes or in elderly patients. When such wound dehiscence fails to heal by secondary intention, alternative approaches must be sought. Failure of healing with superimposed infection can result in dural erosion and CSF leaks. Spinal drainage is insufficient to provide for dural closure in the depths of an open infected wound. Under those circumstances, extensive debridement of the wound in the operating room is necessary. Excision of all infected bone is undertaken until bleeding cancellous bone is encountered. Dural repairs are undertaken with free or pedicle fascial grafts attached to a trapezius flap. The trapezius flap can obliterate the dead space in the depths of the spinal wound, providing for an optimal watertight closure. The wound is further approximated in layers, usually over drains. The approximation usually is undertaken with heavy, nonabsorbable sutures such as #0 or #2 braided nylon, and the skin is closed with heavy #0 Prolene monofilament. It is important to maintain optimum nutritional status of the patient to enhance healing. In the presence of anemia (hemoglobin <8 g/dL), blood transfusions also will contribute to increased activity and, potentially, to wound healing. The patient is maintained in a figure-8 brace for 4 to 8 weeks.

Latissimus Flaps

The latissimus dorsi muscle, because of its location and blood supply, provides muscle or myocutaneous flaps for the closure of spinal defects overlying the lower thoracic and lumbar spine (see Fig. 122-1). Its blood supply is type V, consisting of one dominant vascular pedicle, which in this case is the thoracodorsal artery arising from the subclavian artery and secondary midline and paramedian pedicles. The thoracodorsal artery consists of the dorsal cutaneous branches of the intercostal and lumbar arteries.^7,11 The intercostal arteries that contribute most to the secondary pedicles are the 9th, 10th, and 11th intercostal arteries, as confirmed on cadaveric dissections.¹⁵ These perforators usually enter the latissimus muscle approximately 5 cm from the midline. Latissimus dorsi flaps, with and without skin, are based on the thoracodorsal artery and are dissected away from the spinous process attachments. Such flaps generally are suited for repair of large thoracic wall or lateral iliac decubiti.

Reverse latissimus flaps, on the other hand, are dissected laterally or rostrally and thus maintain the blood supply of the flap from the midline paraspinal secondary vascular pedicles. The integrity of the penetrating vessels on the ventral surface of the muscle is preserved because the supply from the thoracodorsal artery is sacrificed for distal mobilization. Such latissimus dorsi flaps are referred to as reverse flaps and are suited for the repair of spinal defects of the lower thoracic and lumbar spines (Fig. 122-2). The muscle flap is based medially on the 9th, 10th, and 11th intercostal feeders.

FIGURE 122-2 Postoperative axial T1-weighted (A) and T2-weighted (B) images reveal a sacral meningocele in a 77-year-old woman who underwent release of a tethered cord. Although no external cerebrospinal fluid leakage was present, the patient was symptomatic, with postural headaches and a large subcutaneous fluid collection.

The length of the pedicle is geared to the size of the spinal defect to be repaired. The portion of the latissimus dorsi muscle mobilized and its width are customized to the case at hand (Fig. 122-3). The latissimus dorsi muscle provides a large muscle mass capable of filling far larger spinal defects than is possible with trapezius muscle flaps. The reverse latissimus flap, with or without its cutaneous pedicle, when necessary, is tunneled subcutaneously to the midline incision. The site of the cutaneous pedicle is then repaired with a split-thickness skin graft. Reverse latissimus flaps are usually adequate when used unilaterally.

FIGURE 122-3 Surgical exploration was performed in the patient shown in Figure 122-2, and no frank cerebrospinal fluid leak was identified. This intraoperative photograph was taken while standing at the foot of the table looking toward the head. A reverse latissimus dorsi flap was harvested from the left side and used for obliteration of the dead space. The midline incision was extended rostrally, and the latissimus muscle sectioned below its insertion. The muscle head is held up and reflected into the lumbosacral incision while safeguarding its vascular supply. On follow-up, she was asymptomatic, and her lower back was flat without reaccumulation of the meningocele.

Bilateral large musculocutaneous latissimus flaps may be advanced medially to cover large midline spinal defects. In these circumstances, the flaps are based on the thoracodorsal artery with partial preservation of the secondary intercostal blood supply. Skin grafting may be necessary to cover the relaxing incisions made on either side of the torso to facilitate advancement.¹⁰

It is possible to create a large muscle or skin and muscle flap using the latissimus dorsi muscle based on a vein graft extension of the thoracodorsal artery.¹² This approach requires a microsurgical team and the harvest of saphenous or other suitable vein to interpose on both the arterial and venous circulation. The vein interposition can be performed below the subscapularis branch, and a large muscle advancement can be carried out. This overcomes the problems that occasionally occur when using the most medial portions of the flap with complete ligation of the paraspinous perforators. This medial-most portion of the flap is primarily fascial and of marginal circulation. It depends entirely on the thoracodorsal vessel for inflow. Use of the vein graft and transection of the insertion of the muscle permits safe movement of more reliable muscle and skin medially. A “V-to-Y” technique allows movement of relatively large skin-muscle flaps, when such flaps are needed. This technique also can be used to advance only the latissimus dorsi muscle, and the epithelial coverage is provided by application of a split-thickness graft to the exposed portion of the latissimus muscle.

Gluteus Maximus Flaps for the Sacral Region

The gluteus maximus is a large buttock muscle with a quadrilateral shape. It extends from the ilium, sacrum, coccyx, and sacrospinal aponeurosis to the greater trochanter of the femur and the iliotibial band of the fascia lata.¹⁰ This large muscle has a type III vasculature, with two dominant arteries, the superior and inferior gluteal arteries, arising from the internal iliac artery.^11,16 Because of its location, the gluteus maximus muscle, with or without an attached skin flap, is suited for repair of sacral, ischial, trochanteric, and ilial open wounds. The muscle mass and overlying skin have sufficient size and redundancy that a unilateral myocutaneous flap often is sufficient to provide coverage for a midline defect. For the coverage of a sacral decubitus, the skin incision extends along the caudal margin of the iliac crest laterally from the edges of the wound that had been debrided. The incision is carried through the subcutaneous tissue, and a plane is created between the gluteus maximus and medius muscles. It is important to maintain the integrity of the superior gluteal artery as it enters the deep surface of the gluteus maximus muscle. However, if the superior gluteal artery interferes with the mobility of this muscle flap, it can be sacrificed for increased mobility. In instances in which this has been done, the blood supply provided by the inferior gluteal artery has proven sufficient.¹⁶ The muscle and skin edges are then sutured to the contralateral debrided edge of the exposed wound after incision of all infected and devascularized bone. Depending on the size of the defect to be covered, the lateral caudal margin of the myocutaneous flap can extend inferiorly to the greater trochanter. The gluteus medius muscle provides adequate soft tissue padding of the iliac crest. The donor site of the skin is covered with a split-thickness skin graft. Vacuum drains usually are sufficient to avoid the accumulation of hematomas and seromas that can complicate and impede healing. The muscle flap usually is sutured in place with heavy-gauge absorbable suture such as #0 and #2 Vicryl, and the skin is sutured with monofilament nylon or Prolene. Heavy dressings are applied to prevent pressure on the flap that may impair adequate perfusion. The patient is to be kept on the side or in the prone position for at least 2 weeks subsequent to flap rotation.

The rotational advancement of gluteus-based flaps for sacral wounds has been largely replaced by V-to-Y techniques. The sacral lesion is debrided, and depending on the transverse diameter of the wound, either a single or a bilateral V incision is designed. The origins of the gluteus maximus are freed up as needed, and the muscle is dissected free at the lateral margin, dissecting medially as needed to free the flap. The superior or inferior gluteal artery must be kept intact. This myocutaneous flap is then advanced medially and sutured to the wound edge or to its mirror image flap from the opposite side, if the size of the wound dictates a bilateral approach. As the lateral portion of the flap is moved by this advancement, a linear closure of the defect results in the Y-shaped final appearance as observed in Figures 122-4 and 122-5.

FIGURE 122-4 A, Sacral decubitus ulcer with exposure of sacrum. B, V-shaped myocutaneous flap. C, Completed bilateral gluteal myocutaneous flaps approximated in midline.

FIGURE 122-5 A, Sacral decubitus ulcer with sacral osteomyelitis. B, After closure.

Strategies for Nonhealing Wounds

Strategies for addressing large tissue defects with flaps and grafts have been previously described. Additional strategies for nonhealing wounds include the use of vacuum-assisted closure (VAC) devices and hyperbaric oxygen therapy. Wound VAC therapy, also referred to as negative pressure wound therapy, involves placing a nonbioabsorbable sponge in the bed of a wound covered with an occlusive dressing connected to a suction device with a fluid collection chamber. Wound healing is enhanced by removal of wound fluid, increased angiogenesis, and up-regulation of several tissue factors.^21,22 Wound VACs have been used not only in chronic nonhealing wounds but also in cases of trauma, fasciotomy, and infection.^23–27 A variety of surgical specialties use these devices with seemingly good results,^23,27–29 and some studies have shown cost savings.^30,31 Despite their increased use, however, there are very few randomized controlled trials evaluating their efficacy. A recent Cochrane Review found insufficient evidence that wound VAC use improves healing of chronic wounds.³²

Hyperbaric oxygen therapy (HBOT) is another useful adjunct in treating nonhealing wounds. HBOT involves placing a patient in a hyperbaric chamber where he or she breathes 100% oxygen for brief periods while at an increased barometric pressure. Tissue oxygen tension is more than doubled during these treatments,³³ augmenting wound healing, inducing angiogenesis, and aiding neutrophil function.^34–37 The plasma becomes supersaturated with oxygen to the point that red blood cells are not required to supply oxygen for cellular respiration.³⁸ HBOT is currently indicated in the treatment of the following: decompression sickness, air embolism, necrotizing fasciitis, clostridial necrosis, carbon monoxide poisoning, crush injuries, problem wounds including diabetic ulcers, refractory osteomyelitis, compromised skin grafts and flaps, thermal burns, delayed radiation injury, exceptional blood loss, and intracranial abscesses.³⁹ The number and length of treatments are dictated by the disease process being treated, the response of the wound to treatment, and patient tolerance. Currently, more than 600 hyperbaric chambers are in use across the United States.³⁹

The usefulness of HBOT is predicated on its ability to supply oxygen to tissues at much higher concentrations than at normobaria. Before therapy is initiated, transcutaneous partial pressure of oxygen (TcPo₂) measurements often are made to confirm wound hypoxia and assess whether a wound may benefit from a course of HBOT.^40–43 TcPo₂ values near the wound are obtained with the patient inspiring air at sea level (21% oxygen), inspiring 100% oxygen at sea level, and during HBOT. If the TcPo₂ is in the normal range (≥40 mm Hg) while inspiring air, this confirms that the wound is not hypoxic, and alternative causes of wound nonhealing should be aggressively sought and corrected. When inspiring 100% oxygen at sea level, it has been shown that increases of less than 10 mm Hg in the TcPo₂ reliably predict wounds that likely will not respond to HBOT.⁴⁰ TcPo₂ values less than 400 mm Hg during HBOT also have been shown to predict which wounds will not respond to HBOT.^41–43