Lumbar Fusion: Matching Expectations and Outcomes

Edward N. Hanley, Jr., MD
American Academy of Orthopedic Surgeons Bulletin
April 1993

Edward N. Hanlev, Jr., MD. is chairman of the Department of Orthopaedic Surgery. Carolinas Medical Center;. Charlotte, NC.

Lumber spine fusion is a commonly performed surgical procedure, yet the indications for the operation and results of it remain controversial and confusing. The concept of spine fusion is based on experience from other regions of the body where arthrodesis has been employed to treat painful joints and augment correction of deformity.

Initially, spinal fusion was used for the treatment of infectious conditions. scoliosis, and traumatic injuries. Based on these experiences, spinal arthrodesis has been employed in an attempt to control pain attributed to abnormal or "unstable" motion or mechanical insufficiency produced by degenerative change.

Despite little objective information concerning patient outcomes from such procedures, spinal fusions are being performed at increased rates throughout this country with tremendous regional variations in the numbers of such operations performed. Technical "advances" in diagnostic imaging techniques, internal fixation devices, surgical instruments and techniques, and bone grafting methods have led to a gradual extension of the indications from those that are relatively well established (scoliosis, trauma, spondylolisthesis) to the somewhat controversial (instability) to what some would consider fringe (diskogenic back pain).

Expands candidate base

This expansion in indications has opened up an almost endless supply of patients who are potential candidates for this procedure. This has served as an economic boon to some spinal surgeons and implant manufacturers, but has led to concern and criticism on the part of third party payers, employment compensation bodies, and certain members of the medical community.

The problem has been exacerbated by the methods by which spine surgery procedures are coded and billed. Due to the overlap of neurosurgery and orthopaedics, this is one of the few areas where the procedure codes are "unbundled." often leading to the submission of multiple procedure codes and substantial charges for one surgical experience.

In a recent article, "Patient Outcomes After Lumbar Spine Fusion." published in the Journal of the American Medical Association, the authors concluded that "for several low back disorders no advantage has been demonstrated for fusion over surgery without fusion, and complications of fusion are common." They called for randomized controlled trials to "compare fusion. surgery without fusion, and nonsurgical treatments in rigorously defined patient groups." This report has further heated up the debate over the efficacy of this commonly performed surgical procedure.

Who would be fused?

A large volume of information has been published on lumbar spine fusion, but unfortunately most reports contain patients with variable characteristics who were operated on for a variety of conditions and had outcomes assessed by non-standardized methods. Nevertheless, careful review of the data available may assist us in determining what is reasonable. what is unreasonable. and what is or should be considered investigational. Expectations of the surgeon and the patient must also be considered, as they bear heavily on how a result is assessed or construed.

What are the criteria for success? Is complete or almost complete relief of pain and return to full function and employment necessary for a successful outcome or is some diminishment in pain and in the use of pain medication alone enough? What is an acceptable rate of complications for these primarily elective procedures? What about the common repeat procedures after surgical fusions ( pseudarthrosis repair, instrument removal. etc. )? Can they be justified? What about the costs?

It is estimated that the "total" cost of a lumbar disk excision approximates S30,000, but that of an elective spine fusion in a workers' compensation patient may be as high as $250,000. This, with a return to work rate of between 30 percent and 60 percent.

It is generally accepted and substantiated in the literature that lumbar spine fusion may be appropriate in isthmic spondylolisthesis, degenerative spondylolisthesis, and certain forms of scoliosis, but is not indicated for stable forms of multilevel spinal stenosis or in conjunction with primary disk excision. The real areas of controversy and confusion lie in the diagnoses of lumbar "segmental instability" and "diskogenic low back pain."

Segmental instability

This "condition" is thought to be related to disk degeneration. and hence intermingles with the category known as "diskogenic" low back pain. The difficulty with this diagnosis lies in the inability to adequately define the radiographic, biomechanical, and clinical criteria for "instability."

Additionally, it is not even apparent what the clinical symptoms of such a diagnosis are. Some believe that low back pain in conjunction with greater than 4 mm. of translation or 10 degrees of angulation characterize this problem. Some think that discography and facet blocks, a trial of cast or brace immobilization, or even external spinal fixation are helpful in predicting surgical outcome.

Unfortunately, many patients for whom this diagnosis has been made possess negative variables, such as chronic pain, psychosocial abnormalities, or compensation or litigation situations, which adversely affect outcome. Little surgical outcome information is available when this diagnosis is involved as an isolated entity.

Diskogenic low back pain

Even more controversial than spine fusion for "instability" is that for disk "insufficiency." This diagnosis is often made after complaints of chronic low back pain that is unresponsive to non-surgical measures. Plain radiographs show no abnormalities or only nonspecific age related changes such as traction spur formation and disk space narrowing.

MRI shows decreased signal intensity in the disk indicative of degeneration and dehydration, but this may be present in more than one third of asymptomatic subjects. Provocative discography has been proposed as a diagnostic tool for the euphemistic "pain generator" of "internal disk disruption" and as a criterion for fusion. Further confusing the issue has been the finding that some patients with normal MRI scans can have abnormal diskography.

Despite the problems concerning this diagnosis, an evolution of surgical procedures has occurred over the past decade or so with an ever increasing number of surgeon and patient participants. Initially, posterolateral fusion in situ was tried. With the advent of pedicle screw instrumentation systems, posterior "rigid" fixation was tried. Intermingled with this was ongoing experience with anterior disk excision and interbody fusion.

More recently, combined anterior and posterior procedures have been advocated, often with the addition of electrical stimulation devices and allograft bone; indeed, these procedures are being performed by many.

Unfortunately, scientific reports contain precious little objective information to substantiate such approaches, particularly in the difficult patient population on which these operations are so often performed. To some, this is viewed as the "Red Badge of Courage" operation, while others maintain that "someone has to try to help these patients" or "if I don t do it, someone else will."

Unfortunately, as much as we would like to let the evidence speak for itself, it can't. Very little real evidence exists. The reports that are available suggest that the diagnostic procedures necessary are complex, extensive, and expensive.

Surgical outcome data are sorely lacking and support for these approaches are based mainly on opinion and personal experience. What information is available would suggest that some degree of pain relief occurs in 50 percent to 80 percent of patients, but measurable functional improvement or return to work occurs in significantly fewer. Is this different from the placebo response of such procedures? Is it better or worse that the natural history of the problem is left untreated!

A call for accountability

Lumbar spine fusion is a commonly performed procedure, perhaps too commonly. For certain well defined diagnoses, it is a proven effective treatment method. It has, however, taken on a life of its own for certain ill-defined diagnoses with outcomes that are difficult to objectively de­fine or justify.

Those diagnoses with predominant or concomitant neurological or deformity problems have well defined goals of treatment and expectations of surgical outcome. However, those diagnoses with less clear criteria exhibit less clear surgical outcome results.

Whether or not these procedures are justifiable or not has not been determined. Opinion no longer carries the weight it used to. Just because we think something is good or works doesn't count.

We need to clearly define the criteria for each specific diagnosis, the criteria for each specific treatment method recommended, and unbiased and accountable criteria for what is success and what is failure. The opportunity exists with lumbar spine fusion.

References

Turner I A, Ersek M, Herron L, etal:
Patient outcomes after lumbar spinal fusions, JAMA I 992; 268:907-91 1.

The AAOS Bulletin April 1993