Spinal Wound Closure - Clinical Tree

Summary of Key Points

Effective management of spinal wounds require a thorough understanding of the soft tissue anatomy of the back.
The basis for avoiding spinal wound complications relies on basic surgical principles, such as a clean, vascularized wound, organized layered closure, and optimization of patient wound healing factors.
Vancomycin powder applied during primary closure has been effective in reducing surgical site infection.
If a wound complication occurs, local bedside wound care with microdebriding dressings and antibacterial ointments can help in the closure of less complicated spinal wounds.
Negative pressure dressings, also called vacuum-assisted closure systems, have been used with success in chronically nonhealing clean or mildly infected wounds.
Hyperbaric oxygen therapy may be useful for the treatment of nonhealing or infected wounds. The high tissue oxygen tensions may increase angiogenesis and enhance neutrophil function.
Paraspinous muscle flaps are an excellent first choice for coverage of exposed bone or hardware at the midline following primary or secondary closure
Trapezius flaps are useful for defects of the upper third of the thoracic spine and, because of their relatively expansive length and width, can cover a relatively wide arc of rotation.
The latissimus dorsi muscle is useful to provide muscle-only or myocutaneous flaps for the closure of spinal defects over the lower thoracic or lumbar spine.
Unilateral or bilateral gluteus maximus flaps are useful in nonambulatory patients for the closure of sacral or ischial sores.

Wound complication in spine surgery is important and may have a significant impact on costs of care and on clinical outcomes. The purpose of this chapter is to describe the anatomy of the spine muscles and the use of specific techniques for wound complication avoidance. The chapter also describes specific muscle flaps that are useful for wound coverage in the setting of local muscle deficiency.

Soft Tissue Anatomy of the Back

The skin of the back consists of epidermal, dermal, and subcutaneous components, but, unlike in other parts of the body, the dermis of the back is much thicker. Within the subcutaneous component of the skin lies fat and a thin connective tissue layer known as the superficial fascia. At the midline, the dermis is severely limited in its mobility because of dense adhesions to the superficial fascia, the deep fascia of the back, and the ligamentous attachments of the spinous processes (the ligamentum nuchae in the cervical midline and the supraspinous ligament in the thoracolumbar midline). Laterally, however, these connections are much looser, except in areas of bony prominence, such as the scapula and iliac crests. The deep fascia of the back, known as the thoracolumbar fascia, consists of three layers (posterior, middle, anterior) that invest and organize the muscles of the back ( Fig. 172.1 ). Superiorly, the thoracolumbar fascia originates from the superficial investing layer of the deep cervical fascia. Inferiorly, it inserts into the sacrum and posterior iliac spine. Here in the low back the posterior layer of thoracolumbar fascia is also known as the lumbar aponeurosis and serves as the origin of the latissimus dorsi muscle. Medially, the thoracolumbar fascia attaches to the spinous processes of the thoracic vertebrae. Laterally, it fuses with the intercostal fascia and becomes continuous with the aponeurosis of the transversus abdominis of the abdomen (see Fig. 172.1 ). ^,

Fig. 172.1, 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.

The muscles of the back are grouped into the superficial, intermediate, and deep layers. The superficial and intermediate groups are extrinsic muscles involved in movement of the upper limbs and respiratory function, respectively. The deep group are intrinsic muscles of the back involved in extension and rotation of the head, neck, and vertebral column.

The superficial group is subdivided into an outer layer and inner layer. The outer superficial layer consists of the trapezius and latissimus dorsi muscles, whereas the inner superficial layer includes the levator scapulae and rhomboid major and minor muscles. The trapezius is a large, flat, triangular muscle in the upper back with a broad origin extending along the midline from the superior nuchal line to the spinous processes of T12. The muscle inserts laterally on the lateral third of the clavicle, the acromion, and the scapular spine. It is innervated by the accessory cranial nerve (XI). The latissimus dorsi originates from thoracolumbar fascial attachments to the spinous processes of T7 through L5, the iliac crest, and ribs 10 to 12. It inserts into the intertubercular groove of the humerus and is innervated by the thoracodorsal nerve, a branch off the posterior cord of the brachial plexus. The levator scapulae lies deep to the trapezius muscle, originating from the transverse processes of C1‒C4 and inserting into the superomedial portion of the scapula. It is innervated by the dorsal scapular nerve, with contributions from spinal nerves C3 and C4. The major and minor rhomboids also lie deep to the trapezius. They originate from the spinous processes of the upper thoracic vertebrae and insert into the medial border of the scapula. The dorsal scapular nerve also innervates these muscles. Located more laterally are several muscles that originate on the scapula and insert into the humerus (supraspinatus, infraspinatus, subscapularis, teres minor, and teres major). However, these are not often employed in spinal wound closure.

The intermediate group consists of serratus posterior superior and serratus posterior inferior, which lie deep to the rhomboids and latissimus dorsi muscles, respectively. These muscles originate along the vertebral column and travel laterally to attach to the ribs, thus aiding in respiratory function. They receive innervation from segmental branches of the intercostal nerves.

The deep muscles of the central back are located in the paraspinal region and are divided into lateral and medial tracts. The lateral group consists of the iliocostalis, longissimus, and spinalis; the medial group includes the rotatores, multifidus, and semispinalis.

In the cervical and upper thoracic regions, the deep group comprises the splenius capitis, splenius cervicus, semispinalis capitis, and longissimus capitis muscles, each of which attaches to the skull and cervical vertebrae. The splenius muscles originate from the ligamentum nuchae and the spinous processes of the lower cervical and upper thoracic vertebrae, whereas the longissimus and semispinalis muscles originate from the cervical and upper thoracic transverse processes. Deep to the splenius, semispinalis, and longissimus musculature lie the multifidus, rotatores, spinalis, and interspinales muscles. Superior to C2, however, the deep musculature is termed the suboccipital musculature and consists of the rectus and obliquus capitis groups. ^,

The gluteal region also contains an outer and inner muscular layer. The superficial muscular group encompasses the gluteus maximus, medius, minimus and tensor fasciae latae, all of which are involved in abduction and extension of the hip. The gluteus maximus is the most superficial and originates from the upper ilium, sacrum, coccyx, and sacrotuberous ligament. It inserts into the iliotibial band of the tensor fasciae latae and the gluteal tuberosity of the femur. The deep muscular group is primarily responsible for lateral rotation of the femur and comprises the piriformis, gemelli, obturator internus, and quadratus femoris.

Primary Closure

The basic tenets of wound management and closure apply to surgical spinal wounds. Preoperative conditions that compromise wound healing should be corrected, where possible, to provide the best environment for primary closure and healing following a surgical procedure. Likewise, meticulous care should be taken throughout any operative procedure to minimize tissue damage, including prolonged and excessive retraction, thereby reducing surgeon-induced impediments to wound closure/healing. In procedures involving dural openings, whether intentional or unintentional, every attempt at a watertight dural closure should be made. Fine nonabsorbable (5-0 or 6-0 Prolene) sutures are generally used with or without a fascial autograft or commercially available dural substitute allografts. The suture line can be covered with a layer of fibrin glue, such as Tisseel (Baxter, Deerfield, IL), or tissue sealant (Duraseal, Integra LifeSciences). If there is concern regarding the quality of the 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 extensive spinal procedures, a large potential dead space exists that is amplified in those having undergone laminectomy at contiguous levels. An orderly, layered closure facilitates wound healing by eliminating dead space and reducing the risk of fluid collection and infection. The paraspinal musculature is approximated with a few large absorbable sutures, being careful not to strangulate the tissue, which can cause muscle necrosis and severe postoperative pain. Fascial closure is performed carefully, with large interrupted absorbable sutures; in cases of reoperation or where radiation is anticipated, nonabsorbable braided suture is recommended. A tight closure of the fascia is recommended to reduce dead space, as well as prevent possible CSF leakage. This layer may also serve as a barrier to the development of a deep infection from a superficial wound infection. Placement of a drain into the epidural or subfascial space should be considered in 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 can not only hamper wound healing but also cause neurological deficit with neural element compression. If CSF is noted to accumulate 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. In these cases, a 2-0 absorbable suture is commonly used. More stout superficial fascial layers, most easily identified in the lumbar subcutaneous tissue, should be the target of reapproximation. This layer of closure both minimizes dead space and takes tension off the skin closure, which can lead to a narrower scar. The dermal tissue is then closed, often 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 anterior-posterior dimensions. The skin is reapproximated with either monofilament suture or staples.

Another spine wound closure adjunct that has gained popularity has been the use of intrawound vancomycin powder application in an attempt to decrease the rate of postoperative surgical site and deep infections. One gram of vancomycin in powder form is added to the wound at the time of closure, both in the deeper planes as well as the subcutaneous ones. So far, the literature is still not completely clear as to the role and efficacy of vancomycin powder in decreasing rates of postoperative posterior spine infections—although improvements in infection rates have been shown—mostly because of the lack of well-designed prospectively randomized and controlled studies. Based on the available evidence, application of intrawound vancomycin powder appears to significantly decrease the rates of wound infection and costs after posterior cervical fusion, ^, posterior fusion for thoracolumbar trauma, ^, and posterior thoracolumbar fusion surgeries. ^, ^,

In cases in which radiation therapy has been received preoperatively or is anticipated postoperatively, closure of fascial layers should be accomplished with nonabsorbable 0 or 2-0 suture, as opposed to the absorbable suture used in primary closures. This will provide more protracted wound support in an environment where wound strength may develop more slowly. Radiation therapy contributes to impairment of circulation by virtue of endothelial swelling and subintimal fibrosis, resulting in an obstructive endarteritis. In addition, the subcutaneous tissue is often replaced by dense fibrosis as a result of the radiation injury. This impairment in circulation can further impede and delay wound healing.

Nonhealing Spinal Wounds

Impediments to wound healing are numerous and can be challenging to overcome when faced with a nonhealing spinal wound. Nonhealing wounds are costly not only in terms of dollars to the healthcare system but also, more importantly, in terms of the morbidity and potential for mortality for the affected patient. Risk factors for poor healing include, but are not limited to, nutritional status, corticosteroid use, diabetes mellitus, history of radiation treatment, a variety of collagen disorders, smoking, immunosuppressant therapy, infection, neurological deficit resulting in inability to offload the wound site, and tissue hypoxia. ^, With extensive wounds and instrumentation necessary for spine tumors, the hardware can sometimes become exposed because of compromised muscle and skin. It is advantageous for the surgeon and the patient to address as many factors preoperatively as possible.

If a wound is infected or contains nonviable tissue, it must be optimized before proceeding with wound closure. If a wound has been demonstrated to contain greater than 10 ⁵ bacteria per gram of tissue or is clinically suspected of being infected, treatment with antibiotics and an antibacterial cream or dressing is indicated. A variety of antibacterial creams and dressings are available. Commonly used antibacterial creams include silver sulfadiazine, mupirocin, and SilvaSorb (Medline, Northfield, IL). There are also a variety of other dressing materials that contain silver and have antibacterial and absorptive attributes, such as Mepilex Ag (Molnlycke, Gothenburg Sweden). If nonviable tissue is present within the wound, this requires debridement before successful wound closure can be accomplished. This can be accomplished surgically, although if a limited amount of nonviable tissue is present it can often be eliminated with serial dressing changes. Wet-to-dry dressing changes with saline-soaked or 0.25% Dakin’s solution–soaked gauze may debride the wound sufficiently. Santyl (Smith and Nephew, Fort Worth, TX), a collagenase-containing ointment, can also be used to actively debride a wound.

Debridement

In the presence of significant tissue damage or infection, extensive debridement is often necessary before closure can be reattempted. This may require multiple takebacks for serial excision and must include debridement of any infected or nonviable bone, until bleeding cancellous bone is encountered. Additionally, these areas should be pulse-lavaged with either saline or antibacterial irrigant to decrease the bacterial burden within the wound cavity. As noted previously, in the instance of multiple risk factors for poor wound healing (uncontrolled diabetes, malnutrition, congestive heart failure, chronic obstructive pulmonary disease, etc.), definitive closure should be delayed until the patient has been medically optimized. In the event of dural erosion and CSF leak, spinal drainage alone is insufficient to induce dural closure within an open infected wound. Primary repair with or without dural substitute is indicated and may be reinforced with fibrin glue or tissue sealant. Soft tissue coverage will also be required with a locoregional flap.

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