Soft Tissue Anatomy of the Back

The skin of the back is similar to skin in other parts of the body with epidermal, dermal, and subcutaneous components. The dermis of the back is thicker than that in other parts of the body, however. Superficial fascial layers within the subcutaneous tissue limit the degree the dermis can move relative to underlying structures of the back. Muscular, fascial, and ligamentous tissues lie deep to the subcutaneous layer, with different structures being found in different anatomic locations ( Fig. 165-1 ).

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 ligamentum nuchae is a fibrous structure that lies deep to the subcutaneous tissue in the cervical area in the midline. It is the cervical extension of the supraspinous ligaments that extend between the spinous processes more caudally, and it attaches to the base of the skull in the occipital region. The trapezius muscle is a large, flat, somewhat triangular muscle in the upper back with a broad origin extending from the superior nuchal line of the skull along the ligamentum nuchae to the spinous processes of C7-T12. The muscle inserts laterally to the lateral third of the clavicle, the medial acromion process, and the scapular spine. Deep to the trapezius in the cervical and upper thoracic regions are the splenius, semispinalis, and longissimus muscles, each of which has components that attach to the skull and to the cervical vertabrae. 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. Rostral to C2, however, the deep musculature is termed the suboccipital musculature and consists of the rectus and obliquus capitis groups. The levator scapulae lies deep to the trapezius muscle more laterally in the cervical region. It originates from the transverse processes of C1-4 and inserts into the superomedial portion of the scapula.

The superficial muscular group of the thoracolumbar region includes the trapezius, described in the preceding paragraph, and the latissimus dorsi, originating from the spinous processes of T7 to T12, the thoracolumbar fascia, and the iliac crest. The latissimus dorsi muscle inserts onto the intertubercular groove of the humerus. The thoracolumbar fascia lies caudal to the latissimus dorsi muscle and attaches medially to the spinous processes of the lumbar and sacral vertebrae and caudally to the iliac crests. Laterally, it attaches to the ribs and intercostal fascia. The thoracolumbar fascia is multilayered and arises from the aponeurosis of the transversus abdominis. The dorsal layer of the thoracolumbar fascia is termed the lumbar aponeurosis and serves as the origin of the latissimus dorsi muscle. The intermediate muscles of the trunk lie under the trapezius and latissimus dorsi muscles and include the major and minor rhomboids and serratus posterior. The deep muscles of the central back are located in the paraspinal region and are divided into lateral and medial tracts. The iliocostalis, longissimus, and spinalis muscles make up the lateral group; the rotatores, multifidus, and interspinales make up the medial group. More laterally, a number of muscles that originate on various parts of the scapula and insert on the humerus (including the supraspinatus, infraspinatus, subscapularis, teres minor, and teres major) are located.

Caudal to the thoracodorsal fascia lie the gluteus muscles. The gluteus maximus muscle is most superficial and originates from the inner upper ilium, sacrum, and coccyx. It inserts into iliotibial band of the fascia lata and the gluteal tuberosity. The gluteus medius and minimus muscles underlie the gluteus maximus, as do the piriformis, obturator internus, and gemelli.

Primary Closure

The basic principles and tenets of wound management and closure apply to surgical spinal wounds. Preoperative conditions that interfere and compromise wound healing should be corrected, where possible, to provide the best environment for closure and healing following a surgical procedure. Likewise, meticulous care should be taken throughout any operative procedure to minimize tissue damage, thereby reducing surgeon-induced impediments to wound closure/healing.

In procedures involving dural openings, whether intentional or inadvertent, every attempt at a watertight dural closure should be made. Fine nonabsorbable sutures are generally 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 Tisseel (Baxter, Deerfield, IL). Where 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 leakage from the wound. In the latter case it is imperative to return to the operating room, readdress the cerebrospinal fluid (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 multiple 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 local muscle necrosis and severe postoperative pain. Fascial closure is performed carefully with large interrupted absorbable sutures, or 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 can also cause neurologic 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 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, or in some cases skin adhesive application may be appropriate.

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 the 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 due to the lack of well-designed prospectively randomized and controlled studies. Based on the available evidence, applications 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. The use of vancomycin powder in deformity reconstruction surgeries has been associated with contradicting results.

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 nonabsorbable suture more commonly utilized. 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. These deleterious effects can be exacerbated by wound infection, diabetes, or advanced age.

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 health care system but also, more important, 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, neurologic deficit resulting in inability for the patient to change positions, and tissue hypoxia. With extensive wounds and instrumentation necessary for spine tumors, the hardware can sometimes become exposed due to compromised muscle and skin ( Fig. 165-2 ). It is advantageous for the surgeon and the patient to address as many factors preoperatively as possible.

Lower back wound with exposed hardware.

If a wound is infected or contains nonviable tissue, one must optimize the wound 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 an antibacterial cream or dressing is indicated. A variety of antibacterial creams and dressings are available. Commonly used antibacterial creams include silver sulfadiazine, mupirocin, SilvaSorb, and Iodosorb. There are also a variety of additional dressing materials that contain silver and have antibacterial attributes. If nonviable tissue is present within the wound, this requires debridement before successful wound closure can be accomplished. This can be accomplished surgically, though if a limited amount of nonviable tissue is present, it can often be eliminated with dressing changes. Wet to dry dressing changes with saline-soaked gauze will debride a wound. Santyl, a collagenase-containing ointment, can also be used to actively debride a wound.

Debridement

In the presence of significant severe tissue damage or infection, extensive debridement is often necessary before closure can be attempted ( Fig. 165-3A ). All infected and nonviable bone is debrided until bleeding cancellous bone is encountered. Multiple debridement procedures are sometimes required to generate a clean wound suitable for closure. Wound infections in the spinal area 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.

( A ) Dehisced cervical wound complicating an infected posterior cervical instrumentation and fusion. Infected spinous processes are exposed. ( B ) Cervical wound with wound VAC applied. ( C ) Cervical wound after wound VAC therapy. The wound bed now exhibits a beefy red appearance and is ready to receive the reverse trapezius myocutaneous flap. ( D ) The trapezius flap has been transplanted, and subcutaneous drains are in place. The donor site for the trapezius flap is shown. ( E ) Six months later the cervical wound is closed with a viable myocutaneous flap.

If a patient has one of the risk factors for poor healing that can be reversed or, at the minimum, optimized, it may be better to delay wound closure until this has been accomplished. Examples of such reversible healing inhibitors include malnutrition and smoking. It may also be prudent to delay wound closure in poorly controlled diabetics until their diabetic management is optimized. In addition, there are clinical situations where it may be better to delay wound closure until a patient’s overall medical condition stabilizes or improves.