Spine Reoperations

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Chapter 202 Spine Reoperations

Preventing repeat spine surgery is an important goal for surgeons and their patients. Reoperation is generally an undesirable outcome, implying persistent symptoms, progression of the underlying disease, or complications related to the initial operation. A higher risk of reoperation was observed among patients covered by workers’ compensation insurance compared with those with other types of insurance. Patients under age 60 were more likely than those age 60 years and older to have second operations. Males had a slightly lower risk of reoperation than females, and having any comorbidity resulted in a higher risk of reoperation.1

Often reoperations on the spinal column are more technically difficult than the first operations, and the risk of surgical complications is potentially greater. In addition to the technical problems of reoperation, clinical and radiographic evaluation of the patient is more difficult. Because normal anatomic relationships and normal tissue planes have been altered, imaging is less accurate and the surgical pathology is more difficult to recognize.

Patients undergoing surgery for degenerative spine disease may require further surgery for disease progression at the original operative level or at adjacent levels or for instability. Reoperation has proven to be much less effective than initial surgery, and it is estimated that only 30% to 50% of patients benefit from this second surgical procedure. Reoperation rate varies with the region of the spinal column, type of disease, and type of previous surgery. Reoperations are performed at the rate of 2.5% per year at the cervical spine level and range from 8.9% to 10.2% at the lumbar level. Reoperations are more expensive; a recent study found that the average hospital charge for a cervical spine reoperation is $57,205.2 Identifying modifiable factors, such as the choice of approach, might reduce the need for spine reoperations and might improve public health and curb health care expenditures.

MRI remains the most valuable imaging study, but it may not be adequate for examination of bony detail. Plain films are of great importance for determining exactly what was done previously, and CT scanning with two- and three-dimensional reconstruction can provide bony detail that is useful during reoperation. These techniques are particularly useful for recognizing failed fusion or instability. CT myelography is still useful when there is question about pathology definition.

Some general principles of wound healing should be kept in mind when reoperating on the spine. If the reoperation is being performed through the same approach as previous surgical interventions, the scar in the skin may be excised so that fresh skin edges are approximated. This may reduce the chance of superficial wound infection, wound dehiscence, and a poor cosmetic outcome. The surgical field in reoperation should be exposed beyond the scar tissue and into normal surgical planes, so that the surgeon is working from normal anatomy on either side of the scar. Foreign material in the wound, which could be a source for bacterial contamination, should be removed unless doing so would create excessive tissue destruction or unacceptable instability.

Usually, reoperations on the spinal column are performed for the following reasons: (1) recurrent or persistent neural compression; (2) development of, or persistence of, instability; (3) CSF leak; (4) hematomas; and (5) infection.

Neural Compression

The most common reason for reoperation on the spine is recurrent or persistent neural compression. Of all the indications for reoperation for neural compression, recurrent or persistent radiculopathy (radiculitis secondary to disc or scar) is by far the most common.311 Persistent symptoms with neural compression are seen in patients with a recurrent disc herniation, large foraminal osteophyte, thickened ligamentum flavum, facet joint hypertrophy causing root compression and inadequate decompression of the spinal cord or cauda equina in spinal stenosis, calcified nerve, ossification of the posterior longitudinal ligament, recurrent disc herniation, or neoplasia.12,13

Lumbar Radiculopathy or Radiculitis

The reported incidence of symptomatic recurrent disc herniation after lumbar discectomy varies between 3% and 18% in retrospective studies.14 Subjects with larger anular defects and those in whom a smaller proportion of disc volume was removed during the first surgery were associated with an increased risk of symptomatic recurrent disc herniation. Carragee et al. demonstrated that the reherniation rate varied from 1.1% with small fissure-like anular defects to 27.3% for large open anular defects.15 Recurrent disc herniation or progressive disc space loss after discectomy often leads to increased pain and disability, which necessitates repeat surgery. Revision surgery, however, does not always improve symptoms.16 The differentiation of a recurrent disc herniation from an epidural scar presents a dilemma. Characteristics associated with recurrent disc herniation include a nonenhanced or rim-enhanced abnormality surrounding a low-signal-intensity lesion on MRI and extension of contrast into the epidural space and an enhancing abnormality on CT/discography.17 However, the discovery of a focal mass of scar that is obviously compressing a nerve root may still be an indication for surgery. Diffuse epidural scar without nerve root compression, however, is not.

Reoperation for a recurrent lumbar disc herniation often requires lengthening the surgical incision to expose the normal laminae above and below the interspace and freeing of the scar from the previous laminotomy using sharp dissection with a tool such as a sharp curet or a no. 15 knife. A high-speed drill or angled punch is used to obtain further bony decompression and to allow visualization of normal epidural tissue. Residual ligamentum flavum from previous surgery should be removed and the disc space approached from normal epidural tissue rostrally toward the disc space and nerve root. It is important to completely dissect out the nerve root, with good exposure of the axilla of the nerve root and its entire course in the lateral recess. If the dura mater or the nerve root is firmly attached to a recurrent disc fragment, sharp dissection and magnification should be used to free it so that no dural tear occurs during manipulation of the disc fragment. Utmost care should be taken to visualize the paramedian aspect of the disc, which is frequently the site of residual or persistent compressive disc herniations. Exploration, both above and below the disc space, should be carried out to ensure that at the conclusion of the second procedure, no extruded fragment has migrated over the body of the vertebra above or below the disc space. Using a microinstrument, the surgeon should circumferentially feel around the nerve root as it passes through the lateral recess and along its course in the neural foramen. Any dural tears that occur during the dissection should be repaired, if possible, before further dissection is performed. Repairing the dura mater prevents significant CSF fluid loss, with resultant decompression of the dural sac and increased risk of epidural venous bleeding. Primary closure of the dural defect with microsurgical technique or a dural patch graft gives a better result in preventing postoperative CSF leak. If the dura mater cannot be repaired primarily, it can be covered with absorbable gelatin sponge or muscle with fibrin tissue adhesive. A subcutaneous or epidural fat graft covering the dural defect is an effective alternative seal.

Inadequate Decompression of the Nerve Root in Patients with a Large Foraminal Osteophyte

Vertebral osteophytes are a common radiologic finding, affecting 20% to 30% of the elderly population. A number of factors are responsible for the local osteogenesis, notably mechanical factors.

Reoperation for persistent cervical nerve root compression can usually be undertaken via one of several options. In a patient with a previous ventral cervical discectomy and fusion and with a persistent large osteophyte in the neural foramen, correction may be accomplished by performing a simple cervical foraminotomy from a dorsal approach, with or without drilling off the osteophyte. This procedure is probably easier than reoperating from the ventral approach and drilling out the previous fusion and decompressing the foramen. If, however, the osteophyte is ventral and medial in location and cannot be decompressed adequately from a dorsal approach, a reoperation from the ventral approach should be performed. The soft tissue planes may be scarred, but the tissue plane between the carotid sheath and the esophagus and trachea is usually maintained and easily dissected. If the soft tissue scarring is due to previous infection or radiation therapy, the operation may be simplified by operating from the opposite, or virgin, side. An operation being performed from the ventral approach for inadequate neural decompression requires increased bone resection, at least a minicorpectomy, to remove 7 or 8 mm of each vertebral body rostrally and caudally to the disc space and to allow definitive visualization of both nerve roots with magnification. This is often best accomplished by using a high-speed drill and an operating microscope. If the problem is a persistent central osteophyte or ossification of the posterior longitudinal ligament, corpectomy is the safest ventral approach, allowing complete decompression of the spinal cord. The corpectomy is followed by a ventral interbody fusion.

Inadequate Decompression of the Cauda Equina in Spinal Stenosis

Cauda equina syndrome (CES) is a complex of clinical symptoms and signs most commonly secondary to a massive prolapsed intervertebral disc, accounting for 2% to 6% of all lumbar disc herniations. Less common causes of CES are epidural hematoma, infections, primary and metastatic neoplasms, trauma, and prolapse after manipulation, chemonucleolysis, or spinal anesthesia. Meta-analysis of surgically treated CES suggests benefit if decompression is undertaken within 48 hours from symptom onset18 in pooled data from retrospective studies. However, not all studies support this argument, which has raised the notion that the principal determinant of outcome may be not timing, but the extent of the neurologic deficit before surgery.19

Recurrent symptoms of CES occur not only from inadequate previous decompression but also from progression of the disease. The most common radiographic findings are disc herniation and hypertrophic facet arthritis, whereas other features, such as acquired spondylolisthesis, osteophyte formation, stenosis, and scoliosis, are observed less frequently. The pathophysiology remains unclear but may be related to damage to the nerve roots composing the cauda equina from direct mechanical compression and venous congestion or ischemia. A high index of suspicion is necessary in the postoperative spine patient with back or leg pain refractory to analgesia, especially in the setting of urine retention. Regardless of the setting, when CES is diagnosed, the treatment is urgent surgical decompression of the spinal canal.

Recurrence and Inadequate Decompression of the Spinal Cord in Neoplasia

Spinal cord compression from neoplasms is characterized based on location as intramedullary, intradural extramedullary, and extradural. Reoperation represents a viable option in patients with high-grade epidural spinal cord compression who have recurrent metastatic tumors at previously operated spinal levels. In carefully selected patients, reoperation can prolong ambulation and result in good functional and neurologic outcomes. Treatment is palliative, with the goals of achieving pain control and improving or maintaining neurologic function. Reoperation should be considered as a treatment option in patients with tumor recurrences who are no longer candidates for radiotherapy or those who have high-grade spinal cord compression.

A reoperation for persistent spinal cord compression secondary to epidural tumor usually results from a dorsal decompression that was performed on a ventrally or ventrolaterally situated tumor. A different surgical approach, either a lateral extracavitary or a ventral approach, is required for resection of tumor and decompression of the spinal cord, as well as for appropriate stabilization of the spinal column. Reexposure of the dorsal spine may also be necessary for performing dorsal arthrodesis and segmental instrumentation to supplement the ventral arthrodesis.

Reoperation for intramedullary tumors needs a special mention. With advances in microsurgical technology, management of these tumors has shifted toward aggressive treatment with radical resection. This approach is associated with increased long-term survival and improved quality of life for both intramedullary and extramedullary tumors. Spine deformity, a well-documented complication after intradural spinal tumor resection, has been reported in up to 10% of cases in adults and 22% to 100% of cases in children.20,21 Laminoplasty for the resection of intradural spinal tumors is not associated with a decreased incidence of short-term progressive spinal deformity or improved neurologic function. However, laminoplasty may be associated with a reduction in incisional CSF leak.22

Reoperation for intradural tumors requires exposing the dura mater. Intraoperative real-time ultrasound is extremely helpful for planning the dural opening and its extent. If a previous dural incision with retained suture material is present, the dura mater should be opened above and below the previous dural closure, and a small blunt dissector should be used to free the underlying spinal cord or arachnoid from the dura mater. When the dura mater has been opened a second time, placing a dural patch graft on the closure is usually prudent, both to reduce the chances of the dura mater adhering to the spinal cord and to provide increased room for the spinal cord.

Dissection of recurrent tumor from nerve roots and the spinal cord needs to be accomplished under high magnification. Great care regarding hemostasis is necessary to allow good visualization. Dissection is obtained best by using sharp dissection with two-point microcoagulation. If no neurologic structures are deep to the tumor, a laser may be used. The laser is particularly effective in removing ventrally based dural tumors.