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.

Reoperation for Thoracic Disc Herniation

Between 7% and 15% of patients with thoracic disc herniations are asymptomatic; symptomatic herniation is very rare, accounting for only 0.25% to 0.57% of herniated discs in the whole spine. The true incidence for recurrent thoracic disc herniation is not known. An accurate diagnosis may be difficult to determine and therefore may be delayed, resulting in either progressive or occasionally relapsing and remitting neurologic impairment. Reoperation at the thoracic spine level is usually due to persistent or inadequately removed centrally located calcified discs. Thoracotomy for treatment of centrally located recurrent thoracic disc herniations is associated with improvement in or stabilization of myelopathic symptoms in the majority of patients, with an acceptable rate of complications. Modified transfacet pedicle-sparing decompression and fusion is also an alternative. Other indications for reoperation for thoracic disc herniation are missed level at the first operation, missed intradural herniation, and CSF leaks.

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.