Congenital Thoracolumbar Deformity Complication

Although surgery for spinal deformity has shown superior outcomes to nonoperative treatment in terms of pain and disability [1,2,3,4], surgical treatment is not without risks. Studies have estimated the rate of complications to be around 48% [5], with the most common being acute posthemorrhagic anemia, respiratory complications, implant-related complications, and incidental durotomy, among others [5].

Incidental durotomy has an incidence of approximately 1.1–5.19% in scoliosis surgery [5,6,7]. In a report by the Scoliosis Research Society on short-term outcomes after surgery for thoracolumbar fixed sagittal plane deformity, researchers found a durotomy rate of 5.9%, which represented the most common complication [7]. One of the potential sequelae of durotomy is formation of a fistula and cerebrospinal fluid (CSF) leak or pseudomeningocele. When a fistula develops, this increases the risk of meningitis, arachnoiditis, epidural abscess, impaired wound healing, nerve root entrapment, and headache [8].

The purpose of this chapter is to present a case of incidental durotomy during deformity surgery and to provide an overview of the diagnosis and management of CSF leak.

A 33-year-old woman with a history of congenital spina bifida, myelomeningocele, and multiple untetherings of the spinal cord presented to the clinic with increasing back pain radiating into her legs and worsening back and leg spasms. The back pain was the patient’s primary complaint and worsened with any activity. The leg pain bothered the patient to a much lesser degree as it was intermittent and only occasionally occurred down either leg (left leg worse than right). The patient also was experiencing increasing bowel and bladder incontinence over the past year.

On examination, she was in a wheelchair but had the ability to stand and move her legs. She still had some bowel and bladder function. On motor exam, the patient had normal development of the upper body, but she did have a short trunk with notable scoliotic deformity. She had reasonable leg length but abnormal morphology of her feet consistent with her prior myelomeningocele history. Her back incision was well healed from her multiple prior back surgeries. On examination of posture, she had a positive sagittal balance and a trunk shift to the right.

CT and X-rays revealed a hemivertebra on the left at the level of L2 and a block T12–L1 vertebra (Fig. 15.1a–d). L4 and L5 were sacralized (Fig. 15.1a–d). There was also an open spinal dysraphism and postsurgical changes from L3 to the sacrum (Fig. 15.1e, f). MRI demonstrated the conus terminated in a low position at the L3–L4 level (Fig. 15.1e, f). The spinal cord was tethered, resulting in a “bowstring”-type stretching over the kyphotic spinal segments (Fig. 15.1g). On the scoliosis films, her kyphoscoliosis was evident with the apex at the L2 region where the hemivertebra was present (Fig. 15.1h). There was approximately 47 degrees of focal kyphosis at the lumbar congenital anomaly (Fig. 15.1i). Flexion-extension films demonstrated a small degree of flexibility in the lumbar spine (Fig. 15.1j, k, l).

(a) Coronal and (b) sagittal computed tomography (CT) imaging demonstrating a hemivertebrae on the left at the level of L2, a block T12–L1 vertebrae, and a focal left convex lumbar spinal scoliosis at the level of the L2 hemivertebrae with sacralized L4 and L5. (c) Axial CT demonstrates an open spinal dysraphism and postsurgical changes starting at the L3–L5 level. (d) Coronal and (e) sagittal magnetic resonance imaging (MRI) demonstrate the conus terminated in a low position at the L3–L4 level. (f) Axial MRI at the T12/L2 level demonstrates marked congenital spinal canal narrowing. (g) Anteroposterior and (h) lateral scoliosis films demonstrate that the patient had levoscoliosis with the apex at the L1–L3 region scoliosis. (i) Lateral plain radiograph of the lumbosacral region. (j) Flexion and (k) extension films demonstrated a small degree of flexibility in the lumbar spine. (l, m) Anteroposterior and (n, o) lateral postoperative films several months later demonstrated significantly improved spinal alignment and good fusion

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Treatment options were discussed with the patient. Given she exhibited a tethered spinal cord that was draped over a lower lumbar congenital kyphoscoliosis, the goal of treatment was to correct the kyphoscoliosis with vertebral column resection and placement of cage. Such a strategy would potentially improve her structural anomaly of the spine while simultaneously shortening the spinal column, thus indirectly relieving pressure on the tethered spinal cord.

The procedure was done entirely through a posterior approach. Pedicle screws were first placed at T9, T10, T11, T12, L3, L4, and the pelvis. Laminectomies were extended to T12–L1 beyond the prior dysraphic L2–L5 levels. Given the poorly developed dura in this patient with a prior myelomeningocele, CSF was encountered during bony exposure. Specifically, for the planned vertebral column resection (VCR) , the dural sac had to be circumferentially dissected from the bony spine, creating multiple breaches in the friable dural. Each dural hole was primarily repaired with 5-0 Prolene sutures. Muscle patches were also incorporated to serve as plugs in the durotomies because the dura was diffusely friable and thin. After dissection, a bilateral corpectomy of L1 was performed followed by a complete resection of the L2 hemivertebra. Once this was completed, the spine was much more mobile, and the deformity could be corrected with distraction and compression via screws and rods. Distraction was first applied with stable monitoring. Two 8 mm titanium cages, filled with local autograft, were placed to provide anterior support and allow anterior arthrodesis between T12 and L3. Posterior compression maneuvers were then used to compress upon the cages and lordose the spine. All these corrective maneuvers resulted in correction of the focal kyphosis from about 45 degrees to almost 0 degrees. Furthermore, the shortening of the spinal column from the VCRs resulted in decreased tension of the dural sac and its contents.

To ensure CSF containment in light of th e multiple dural repairs of congenitally friable dura, several adjuncts were employed for this patient. First, a layer of collagen-based dural substitute (DuraGen) was wrapped around the dura where CSF was encountered earlier in the case to reinforce the repair. Fibrin glue then was used as sealant over this scaffold. Regarding the soft tissue closure, extra measures were performed. Specifically, local tissue flaps were advanced to help obliterate dead space above the dura and around the spinal implants. This maneuver also allowed a greater amount of durable fascia to be advanced to the midline reducing tension on the wound. Closure of this fascial layer “off tension” was particularly important given her history of myelomeningocele and poorly formed thoracolumbar fascia over the caudal spinal segments. A drain was placed under the fascia to collect blood products but kept off suction to avoid worsening CSF leakage from the dural repair. The fascia was then closed with interrupted Vicryl sutures followed by a running Vicryl suture in an effort to create a watertight fascial closure. Then a supra-fascial drain was placed on full suction, in an effort to prevent CSF leakage through the skin if CSF was able to leak through the fascial closure. This drain served to protect the skin until it had healed from a CSF-cutaneous fistula formation. The skin was then closed with a running 3-0 nylon suture.

Postoperatively, the patient was kept flat for the first 24 h. The drains remained in place for 8 days after surgery as the patient recovered. It was ensured that the subfascial drain was off suction at all times. Output from the drains slowly decreased each day during her hospitalization, and they were removed on postoperative day 8, just prior to discharge. In an effort to decrease CSF production in the postoperative period, she was placed on acetazolamide (Diamox) during her hospital stay and for 4 weeks thereafter. In addition, to prevent collection of a pseudomeningocele following surgical drain removal, she was instructed to wear an abdominal binder at all times for 4 weeks following surgery. At her 1 month clinic appointment, the nylon skin sutures were removed with no signs of CSF leak or pseudomeningocele. The patient made a good recovery with some improvement in bowel/bladder function and significant improvement in back pain that has been durable over 2 years since surgery. Postoperative films most recently show stable deformity correction and spinal fusion throughout her construct (Fig. 15.1m, n, o).

Incidental durotomy and subsequent CSF leak may commonly occur during the decompression portion of the operation or during placement of pedicle screw instrumentation [9], most commonly due to direct dural trauma. Risk factors for incidental durotomy include revision procedures (due to scarring/fibrosis in the epidural space), surgeon experience, and advanced patient age [8]. In a study examining risk factors for this occurrence, authors found that the primary tool involved in durotomy was the Kerrison rongeur, which could be explained by the fact that this tool is primarily used for the decompression [10]. Unrecognized durotomies or durotomies that do not seal appropriately in spite of treatment may lead to subsequent fistula formation and CSF leak.

Symptoms associated with CSF leak include positional headache (which increases in severity with sitting or standing), nausea, vomiting, and/or dizziness [8]. Objective signs include observing clear fluid draining from the incision site (particularly during a Valsalva maneuver), increased drain output with a watery appearance, or a collection of fluid under the skin. CSF can be detected by using a β-2 transferrin assay , which is to have a high sensitivity and specificity [11]. β-2 transferrin is a protein that arises from the action of cerebral neuraminidase, and it is only found within the central nervous system [12].

The imaging gold standard for diagnosis of CSF leak is magnetic resonance imaging (MRI), which may demonstrate fluid accumulation (pseudomeningocele) or a fistula. CSF appears hyperintense on T2-weighted images and hypointense on T1-weighted images. A computerized tomography myelogram may also be useful to establish the location of the pseudomeningocele or “fistulous communication” [12]. CT myelogram may be especially helpful when high-density implants make MRI evaluation difficult.

Ideally, durotomies should be primarily repaired when first encountered in order to decrease the probability of developing a fistula and CSF leak. Although most dural tears are recognized intraoperatively, a small percentage may present at a later time with delayed symptoms of CSF leakage either because the dural tear was not recognized at the time of surgery or because of de novo delayed dural tear [13]. If identified at the time of surgery, durotomies may be repaired with primary sutured closure and/or fibrin glue [14]. Unresolved durotomies may result in CSF leaks, wound infections, pseudomeningoceles, and even postoperative hematomas [14].

Postoperatively, if leakage is confirmed, there are several nonoperative strategies that can be employed including bed rest, wound oversewing, use of an abdominal binder, placement of a subarachnoid drain, or use of an epidural blood patch. If leakage is persistent despite attempting nonoperative treatments, reoperation and primary repair are indicated [8].

Nonoperative Treatment

Bed rest is the most conservative measure along with oversewing the wound. Studies have demonstrated that CSF fistulas may resolve with these conservative measures , especially when the skin or fascia is closed in a watertight fashion [15, 16]. Although various protocols exist, patients are typically kept flat for 24 h, given that this position minimizes hydrostatic pressure at the durotomy site [8]. Patients are then elevated to a sitting position for 8 h, and if tolerated, patients are then allowed to ambulate [8]. If patients are not able to tolerate the sitting position, another 24 h of flat bed rest is recommended. Although this is one bed rest algorithm, there are others that recommend greater than 24 h initial bed rest. There is no definitive algorithm and a retrospective study by Low et al. that compared three different bed rest protocols after durotomy, showing no significant difference in complication rates specific to the durotomy [17]. In their study, an overall durotomy incidence of 6.8% was observed. All patients received fibrin glue intraoperatively. Twenty-six patients were mobilized on the first postoperative day (group 1), nine patients on the second day (group 2), and twenty-six patients on the third day or after (group 3). After analysis, the overall incidence of complications related to durotomy was 18% with no statistical significance between the day of mobilization and the rate of complication (p = 0.433) [17].

In regard to medical therapies, caffeine has the best evidence of effectiveness in treating post-dural-puncture headaches [18]. In their meta-analysis, Basurto et al. also reported that gabapentin, hydrocortisone, and theophylline may also improve headache scores when compared with standard treatment, but there is still insufficient evidence for other agents such as sumatriptan, cosyntropin, or adrenocorticotropic hormone (ACTH). Hydration and medications for pain relief can also be helpful in treating the symptoms of CSF leakage; however, the evidence of these measures for symptom treatment from durotomies is lacking. The best evidence comes from a meta-analysis of post-dural-puncture headaches, which suggests that there is no clear evidence that fluid supplementation prevents post-dural-puncture headaches [19].

The abdominal binder is a form of mechanical compression that has been successful in some cases. The proposed mechanism is “an increase in hydrostatic pressure within the pseudomeningocele, thereby slowing or preventing additional leakage of CSF” [20]. It is thought that compression may further reduce headache and promote dural healing.

Beyond these noninvasive measures, the subarachnoid lumbar drain is a commonly used method to decrease hydrostatic pressure at the durotomy site by acting as a shunting system for CSF. In a study evaluating the success rate of lumbar drainage, Kitchel et al. reported an 82% success rate in patients who had a catheter for 4 days [21]. Some authors recommend the use of a silicone catheter at a draining rate of 10 mL/h which can be adjusted if headache develops [8]. Additionally, the use of antibiotics for prophylaxis during drainage should be considered. Complications of using lumbar drains include headache (60%), meningitis (2.5%), discitis (5%), wound infection (2.5%), and others [22].

An epidural blood patch has also been shown to be effective in treating postoperative pseudomeningocele and CSF fistulas [23, 24]. The epidural blood patch consists of injecting approximately 20 cc of autologous venous blood into the epidural space near the leak [8]. Blood will spread around the dural defect, and it is thought that the clot will form a gelatinous seal over the durotomy [8].

Surgical Treatment

When nonoperative management fails, surgical repair is the definitive treatment. In certain cases, where patients have a profuse leak or severe symptoms, earlier surgical intervention rather than conservative measures may be warranted [12].

For dural repair, the first step is to identify the tear location. Exposure is important, and this may include removing additional bone to optimally visualize the source of CSF leakage [8]. Any visualized nervous tissue should always be protected with cottonoids and a suction device that allows suction regulation to prevent excessive CSF aspiration or inadvertent retraction on exposed neural elements [8]. Rootlets herniating through the dural defect should be reduced back into the thecal sac prior to definitive dural repair. Temporarily placing the patient into Trendelenburg position decreases the intrathecal pressure and decreases the tendency of the intrathecal contents to herniate out of the defect during the closure of the defect.

The dura is best closed primarily with a nonabsorbable suture (4-0 or 5-0 Prolene typically). Instruments such as dural holding forceps and fine needle drivers may be necessary and should be available [8]. A watertight closure is the ultimate goal, and this may be achieved by running the suture starting a few millimeters cephalad to the superior edge of the tear and proceeding to a few millimeters caudal to the tear [8]. If watertight closure is achieved, the dura will reinflate in a pulsatile manner, and integrity should be tested by using a Valsalva maneuver [8].

If a large defect exists, a dural graft or fascia patch may be required. Additionally, dural sealants such as fibrin glue, Tisseal®, BioGlue®, and DuraSeal® may be used.

Outcomes after a durotomy vary. The most common symptom following CSF leak is positional headache that is worse in the standing position. CSF leaks can impair wound healing and also increase the risk for infection. In a retrospective review of 1326 consecutive patients who underwent spine surgery, the authors found an unplanned durotomy rate of 3.8% (51 patients) [14]. Of the 51 cases, 13 developed a postoperative complication (25.5% of all durotomies and 1.0% of the entire cohort) consisting of seven CSF leaks, two wound infections, two postoperative hematomas, and two pseudomeningoceles [14].

An uncommon complication of CSF leak is acute intracranial subdural hematoma [25]. Though rare, it has been suggested that such complications result from CSF overdrainage, and reoperation may be necessary [25, 26]. Likewise, it is important that if using a lumbar drain for treatment of a CSF leak , overdrainage should be avoided because of the risk of potentially catastrophic tonsillar herniation with brainstem compression.

Durotomy may also affect fusion rates after spinal instrumentation [27]. In a series of 327 patients who underwent lumbar fixation with pedicle screws, Bydon et al. reported a durotomy rate of 5.2%, and patients who experienced an intraoperative CSF leak had significantly higher pseudoarthrosis rates compared to controls (p = 0.016) [27]. Some of the hypothesized mechanisms include CSF leakage displacing bone chips and CSF interfering with the bony healing cascade needed for fusion [27, 28].

Conversely, some authors have reported no difference in short- or long-term outcomes for patients who experience a durotomy versus controls [29]. Adogwa et al. examined outcomes of 1741 patients who underwent a first-time lumbar spine fusion, finding an overall durotomy rate of 4% [29]. When compared to controls, there were no significant differences in terms of infection (p = 0.320), need for revision surgery (p = 0.850), or neurological complications (p = 0.660). At 2 years of follow-up, there were no differences in terms of patient-reported back pain, leg pain, or disability (assessed by the Oswestry Disability Index) [29].

In this case example, numerous risk factors for intraoperative durotomy followed by CSF-cutaneous fistula were present for this patient, which included revision surgery, poor-quality dura and thoracolumbar fascia from prior myelomeningocele, and circumferential dural dissection required for a multilevel vertebral column resection. Attempts to contain CSF leakage postoperatively were focused at numerous areas of the patient’s intraoperative and postoperative care. At the dural level, durotomies were primarily repaired and “plugged” with local muscle grafts in the repair. A collagen dural substitute was then wrapped around the dural sac to create a reinforcing scaffold that was then sealed with fibrin glue. Soft tissues, including muscle and thoracolumbar fascia, were then advanced to obliterate dead space and to allow for low-tension, watertight closure of the fascia. A subfascial drain was placed to allow removal of epidural blood products but was kept off suction to avoid worsening CSF leakage from the dural repair. An additional supra-fascial drain was placed on full suction to protect the skin from exposure to CSF that may leak through the fascial closure. Postoperatively, the patient was placed flat to decrease hydrostatic pressure within the dural sac and was instructed to wear an abdominal binder to increase hydrostatic pressure outside the dural sac. Finally, the patient was placed on acetazolamide to decrease overall CSF production in the acute period.

Incidental durotomies are relatively common in spinal surgery. Development of a CSF leak or pseudomeningocele may occur, causing postoperative headache and back pain and potentially increasing the risk of infection or pseudoarthrosis, among others. Multiple conservative and operative options exist for postoperative CSF leak. Ideally, intraoperative identification, primary repair, use of dural sealants, and “watertight” wound closure will minimize postoperative complications.

• Durotomy and CSF leak are potential complications that can occur with deformity surgery and should be repaired at the time of surgery if possible. Care should be taken to maximize soft tissue repair above the durotomy.

• Complications can include postural headache, meningitis, CSF-cutaneous fistula, pseudomeningocele, wound infection, pseudoarthrosis, and reoperation.

• There are multiple methods of managing CSF leaks postoperatively including lumbar drainage, blood patches, and reoperation.