Revision spine surgery

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Why is the term failed back surgery syndrome considered controversial?

Failed back surgery syndrome is an imprecise term used to refer to patients with unsatisfactory outcomes after spine surgery due to persistent or recurrent pain in the spine and/or extremities. This term does not identify a specific diagnosis responsible for persistent symptoms and implies that additional treatment will not provide benefit. Patients with persistent symptoms following surgical treatment should undergo appropriate assessment to differentiate problems amenable to additional surgical treatment from those problems unlikely to benefit from an operation. Patients unlikely to benefit from additional surgery can then be directed toward appropriate global multidisciplinary nonsurgical management strategies involving specialists with expertise in behavioral health, pain management, rehabilitation medicine, neuromodulation, and other advanced pain therapies.

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What key elements should be present to support the diagnosis of failed back surgery syndrome?

An international multidisciplinary panel of experts proposed the following criteria (8):

• Persistent back and/or leg pain for a minimum duration of 6 months following a recent spine procedure

• Completion of a thorough clinical and spinal imaging assessment

• Absence of a clear surgical target based on clinical examination and imaging that is concordant with current symptoms

• Interdisciplinary agreement that additional surgical intervention for spinal decompression and/or fusion is not appropriate

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What are some common identifiable causes that may be responsible for poor outcomes following an initial spinal procedure?

Multiple factors may contribute to a poor outcome following an initial spinal procedure in a specific patient. These causes may occur singularly or in combination. Specific etiologies to consider include:

• Negative patient characteristics: Barriers to successful outcomes may arise as a consequence of medical comorbidities (i.e., diabetes, osteoporosis, smoking), psychosocial factors (litigation, depression, opioid-use disorder, unresolved worker’s compensation claims), or a patient’s unrealistic expectations and goals regarding surgical treatment.

• Inappropriate surgical indications: An inappropriately indicated procedure will predictably lead to a poor outcome. For example, if a spinal fusion is performed for nonspecific low back pain in the absence of an identified pain generator, improvement in symptoms is unlikely.

• Incorrect or incomplete diagnosis: Surgery is unlikely to benefit a patient when it is based on incomplete preoperative assessment, inadequate imaging studies, or when there is a poor correlation between imaging findings and clinical signs and symptoms.

• Inappropriate surgical procedures: Surgery performed at the incorrect spinal level or surgery that is inadequate to address all aspects of a patient’s spinal pathology (i.e., failure to stabilize and fuse when a decompression is performed at an unstable spinal segment) is doomed to failure.

• Technical issues related to the index surgical procedure: An appropriately indicated spine procedure will fail if surgery is not performed with technical expertise. Persistent symptoms may result due to surgical approach-related complications, neural impingement from incorrectly placed spinal implants, incomplete removal of disc fragments, inadequate decompression of spinal stenosis, inadequate instrumentation constructs which dislodge or fail prematurely, or due to failure to maintain or restore lumbar lordosis when multiple lumbar levels undergo spinal instrumentation and fusion.

• Persistence or progression of an underlying disease process: Ongoing spinal degeneration or recurrent tumors may affect the previously operated or adjacent levels and lead to recurrent axial or radicular symptoms.

• Epidural, perineural, or intradural fibrosis: The formation of scar tissue and adhesions following surgery may manifest as chronic neuropathic pain.

• Postoperative surgical complications: Prompt recognition and treatment of postoperative complications such as wound infection, epidural hematoma, cerebrospinal fluid (CSF) leakage, implant failure, or pseudarthrosis, are critical to prevent permanent sequalae.

• Postoperative medical complications: Major medical complications (i.e., myocardial infarction, pulmonary embolus, stroke, acute kidney injury) are associated with increased patient morbidity and mortality.

4

List some important factors to assess based on the history portion of an initial evaluation of a patient with continuing symptoms after spine surgery.

• What were the indications for the initial or most recent surgery?

• Are the present symptoms predominantly radicular pain, axial pain, or both?

• Are symptoms related to activity and relieved with rest or are symptoms continuous and unrelated to activity?

• Are the present symptoms the same, better, or worse after surgery?

• Was there a period during which the patient had relief of preoperative symptoms (pain-free interval)?

• Are the current symptoms similar to or different from those present before surgery?

• Did intraoperative complications occur? (Review the operative report if possible.)

• Were any complications recognized in the postoperative period?

• Inquire regarding work history, involvement in litigation, substance abuse, tobacco use, and investigate if there are other psychosocial factors that could impact future treatment.

• Is there a history of fever, chills, weight loss, or night sweats?

5

What is the significance of a pain-free interval following spinal surgery? How does the temporal relationship of current symptoms in relation to the index procedure help to inform the differential diagnosis?

The presence or absence of a pain-free interval following surgery and the temporal relationship of symptoms to the index surgical procedure provide a starting point for determining the likely causes of symptoms.

• When there is no improvement following surgery or recurrent symptoms within 1 month. Consider wrong level surgery, wrong procedure performed, failure to adequately remove disc fragments or decompress spinal stenosis, iatrogenic nerve root injury, neural impingement by spinal implants, postoperative hematoma or seroma, and surgical site infection.

• When there is initial symptom relief but pain recurs between 1 and 6 months after surgery. Consider recurrent disc herniation, implant failure, loosening or migration, iatrogenic spinal instability (i.e., secondary to pars or facet fracture), and surgical site infection.

• When there is initial symptom relief with pain recurrence after 6 months following surgery . Consider recurrent pathology at the previously operated segment, new spinal pathology at adjacent segments, epidural, perineural or intradural fibrosis, pseudarthrosis (if spinal fusion was performed), and surgical site infection.

6

What are important points to assess during physical examination of the patient being evaluated for possible revision spine surgery?

A general neurologic assessment and regional spinal assessment are performed. The presence of nonorganic signs (Waddell signs) should be assessed. Global spinal balance in the sagittal and coronal planes is evaluated. The physical examination is tailored to the particular spinal pathology under evaluation. For cervical spine disorders, shoulder pathology, brachial plexus disorders, and conditions involving the peripheral nerves should not be overlooked. For lumbar spine problems, the hip joints, sacroiliac joints, and any prior bone graft sites should be assessed. Examination of peripheral pulses is routinely performed to rule out vascular insufficiency. Depending on clinical symptoms, neurologic disorders such as amyotrophic lateral sclerosis or multiple sclerosis are considered.

7

Are laboratory tests useful in the workup of a patient for possible revision spine surgery?

Yes. Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) levels are obtained to rule out an occult infection. Albumin and transferrin levels may be obtained to assess nutritional status.

8

What diagnostic tests are useful in the evaluation of patients following prior spinal surgery?

The sequence of diagnostic studies in the postoperative patient is similar to assessment for primary spine surgery. Imaging studies are indicated to confirm the most likely cause of symptoms based on a comprehensive history and physical examination. Imaging studies performed prior to the most recent surgery should be reviewed if available to better understand details regarding prior surgical treatment. Additional tests that may be considered include diagnostic blocks and electrodiagnostic studies.

• Radiographs: Upright posteroanterior (PA) and lateral spine radiographs are the initial imaging study of choice. Lateral flexion-extension radiographs play a role in the diagnosis of postoperative instability and pseudarthrosis. Spinal deformities are assessed using standing PA and lateral radiographs of the entire spine or EOS slot-scanning. An anteroposterior (AP) pelvis radiograph is obtained to assess for hip-joint pathology when indicated. Depending on presenting symptoms, extremity radiographs may be obtained to evaluate for peripheral joint pathologies, which may mimic spine pathology.

• Magnetic resonance imaging (MRI), computed tomography (CT), and CT-myelography: The most appropriate study is selected based on the patient’s symptoms, the presence or absence of spinal implants, and the specific spinal pathology requiring assessment. MRI with or without gadolinium enhancement is used to visualize the neural elements and associated bony and soft tissue structures. However, MRI is subject to degradation by metal artifact that may arise from microscopic debris remaining at the initial surgical site or from spinal implants (especially nontitanium implants). CT remains the optimal test to assess bone detail and is the most sensitive test for diagnosis of pseudarthrosis. CT-myelography continues to play a role in evaluating the previously operated spine. It provides excellent visualization of the thecal sac and nerve roots in addition to osseous structure, even in the presence of spinal deformity or extensive metallic spinal implants.

• Nuclear medicine studies: Technetium bone scans and positron emission tomography (PET) scans are infrequently utilized in planning revision spine procedures, but can provide valuable information to support a diagnosis of infection or metastatic disease.

• Diagnostic blocks: Various injection procedures have been described for use in the assessment of anatomic pain generators including discography, medial branch or facet blocks, selective nerve root blocks, and sacroiliac injections.

• Electrodiagnostic studies: Electromyograms and nerve conduction velocity studies may be used to assess nerve injury and distinguish between radiculopathy and peripheral neuropathy.

9

What treatment options are available for patients with persistent back or leg symptoms following previous spinal surgery in the absence of a surgically correctable spinal problem?

• Physical therapy

• Medication

• Psychosocial interventions including cognitive behavioral therapy

• Spinal cord stimulation

• Intrathecal narcotics (implantable drug pump)

• Complementary and alternative medicine approaches

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