Patient Selection for Spinal Surgery

It has been estimated that no more than 20 percent of patients who present with axial or radicular symptoms from degenerative back or neck disease are candidates for surgery. Therefore, it is intuitive that the initial screening, evaluation and management of patients with common back and neck conditions should be performed by a medical spine specialist, rather than by a surgeon. A thorough evaluation is mandatory, and an accurate diagnosis, where possible, is preferred before instituting treatment.

Surgical Indications
The indications for surgery are generally unrelenting radicular (extremity) pain, rather than axial back or neck pain, in a patient who has failed an adequate conservative treatment program. The ideal surgical candidate is one in whom radicular pain is predominant, particularly when such pain is associated with objective neurological findings and a correlative imaging study, such as MRI, CT or, occasionally, myelography.

Lumbar Disc Herniation
With respect to lumbar disc herniation, it has been shown that clinical outcome following surgery is directly correlated with the degree of pathology found intra-operatively: Unequivocal neural compression found at surgery generally portends a good clinical outcome, while absence of nerve compression (the so-called “negative exploration”) is usually associated with poor outcome. Therefore, the goal of clinical evaluation and surgical decision making is to identify those individuals who are likely to have definite nerve root compression at surgery, since they are the ones who will have a good outcome.

This decision making is based upon the presence of a neurological deficit (such as muscle weakness or reflex change), the presence of a “tension sign” (e.g., a positive straight leg raising sign) and a correlative imaging study.When the decision for surgery is based solely upon the presence of a neurological deficit, the chance of finding a disc herniation causing neural compression at surgery is approximately 55 percent. When a positive tension (straight leg raising) sign is also found, the chance of finding a symptomatic disc herniation increases to 86 percent.When a positive imaging test also is included, the chance of identifying unequivocal compression is 95 percent. Therefore, at least for lumbar disc herniation, the best clinical outcome occurs when all three factors are present (Figure 1).

Spinal Stenosis
Spinal stenosis is a degenerative lumbar condition characterized by buttocks and/or leg pain, provoked by standing or walking (neurogenic claudication) and relieved by sitting, squatting or leaning. As opposed to disc herniation, which more commonly afflicts younger individuals, spinal stenosis rarely involves people younger than 50.With spinal stenosis, the neurological examination often is normal, and the decision for surgery is then based upon an appropriate history of neurogenic claudication and a correlative imaging test showing unequivocal neurological compression at a level that explains the patient’s symptoms.

Value of Imaging Tests
The choice of imaging tests (e.g., MRI, CT or myelography) is perhaps not as important as the timing of their use. In other words, no test should be ordered until the patient has failed conservative treatment and is a candidate for surgery, unless there are other unusual concerns such as infection or tumor.More important, the test must correlate with and explain the patient’s radicular leg pain and the neurological findings.

Numerous studies have demonstrated that the likelihood of an asymptomatic individual having an abnormal imaging test is approximately 30 percent. As well, the older the patient is, the more likely the chance of having radiographic abnormalities. In this respect, such abnormalities reflect normal age-related degenerative changes. Unless such tests are correlated with objective neurological findings and an appropriate clinical history, there is the risk that too much emphasis might be placed upon the imaging test alone and that inappropriate, and unproductive, surgery could therefore be performed.

Surgical Localization of Pain
It should be emphasized that surgery is indicated primarily for relief of intractable leg or arm pain rather than for low back or neck pain. A prime reason that surgical outcome for radicular leg or arm pain is so successful is that precise localization of the source of pain is possible; thus, surgery can be directed at the precise source(s) and level(s) of pain.With axial back or neck pain, on the other hand, clinical outcome following surgery is unpredictable, primarily because of the surgeon’s inability to accurately localize the source(s) of pain.

There are many potential causes for axial back or neck pain, including the intervertebral disc, the facet joints, ligaments, muscles and tendons, and there is no method to consistently and reliably identify which anatomical structure(s) is the cause of the pain. The generally suboptimal surgical outcome for axial pain reflects a failure of diagnosis as much as a failure of surgical technique. This point is particularly pertinent as spinal surgery enters a new era of arthroplasty (artificial disc replacement), rather than arthrodesis (fusion), for axial back pain. Ultimately, the success of artificial disc replacement for the surgical treatment of back pain will depend upon the ability of the clinician to identify a particular disc as the source of a patient’s back pain.

One of the most important factors in surgical outcome, therefore, is patient selection. The outcome of surgery is only as good as the decision making process that leads to it. A multidisciplinary approach to the diagnosis and treatment of spinal conditions facilitates and optimizes the chances that the most appropriate treatment will be rendered.

Spinal Column, Spring 2005. Cleveland Clinic Spine Institute (CCSI).
Copyright @2005. Cleveland Clinic Foundation. All Rights Reserved.
http://cms.clevelandclinic.org/spine/documents/Spinal%20Column%20Sp05.pdf