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Introduction/Summary Statement: Adjacent Segment Pathology

Riew, K. Daniel, MD*; Norvell, Daniel C., PhD; Chapman, Jens R., MD; Skelly, Andrea C., MPH, PhD; Dettori, Joseph R., MPH, PhD

doi: 10.1097/BRS.0b013e31826cef01
Introduction
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*Washington University Orthopedics, Washington University School of Medicine, St. Louis, MO

Spectrum Research, Inc., Tacoma, WA

Department of Orthopedic Surgery, University of Washington & Harborview Medical Center, Seattle, WA.

Address correspondence and reprint requests to K. Daniel Riew, MD, Cervical Spine Service, Washington University Orthopedics, Washington University School of Medicine, 660 S Euclid Ave, Campus Box 8233, St. Louis, MO 63110; E-mail: riewd@wustl.edu

Acknowledgment date: July 6, 2012. Acceptance date: July 31, 2012.

The manuscript submitted does not contain information about medical device(s)/drug(s).

Supported by AOSpine North America, Inc. Analytic support for this work was provided by Spectrum Research, Inc., with funding from the AOSpine North America.

One or more of the author(s) has/have received or will receive benefits for personal or professional use from a commercial party related directly or indirectly to the subject of this manuscript: for example, honoraria, gifts, consultancies, royalties, stocks, stock options, decision-making position.

What is in a word? Degenerative disc disease—a disease or a focal syndrome?

A semantic exploration of spinal terminology and its inferences to current concepts and our practice.

This focus issue is entirely devoted to symptomatic or imaging-based findings that occur at a segment adjacent to a previously operated spinal motion segment. Already 60 years ago, the finding of “adjacent segment disease” (ASD) was reported in case reports as a relatively unusual complication of lumbar or lumbosacral fusions.1,2 There are, however, still today a number of unanswered questions regarding what has become frequently referred to as “ASD.” What we do know is that what was originally thought to be rare is now considered a potential complication of all spine surgery, particularly arthrodesis. Despite an increasing body of literature, there are many unanswered questions, as follows, related to this topic.

  • Are the findings due to iatrogenic processes or are they due to the natural history?
  • If iatrogenic, can we modify our interventions to decrease its incidence?
  • How should we study and interpret what occurs at motion segments adjacent to an operated spinal motion segment?
  • To what extent do imaging findings correlate with clinical symptoms and when is treatment necessary?
  • How do we treat adjacent segment pathology (ASP)?

We think that these questions are especially timely for a variety of reasons. As spine specialists, we are increasingly held responsible for the results of our interventions. Are changes that occur in spinal motion segments outside our treatment target zone an expression of underlying patient aging or disease, or are our treatment modalities creating a degenerative ripple effect that affects through previously unaffected motion segments of the human spinal column?

Are there things we can do to minimize or even avoid this risk, or at least predict it with some degree of certainty? Are newer intervention strategies, such as motion-preserving devices, capable of decreasing ASDs? As we raise these questions, the basic conceptual conflict of disc degeneration remains unsettled: Is this process in fact a “disease,” an abnormal condition that affects the body of an organism, for which our interventions simply cannot offer a systemic answer but rather provide a focal temporary remedy?3 Or are we dealing with a focal syndrome, an “association of several clinically recognizable features,” signs (observed by someone other than the patient), symptoms (reported by the patient), phenomena, or characteristics that often occur together, so that the presence of 1 or more features alerts the health care provider to the possible presence of the others, for the creation of which we may contribute depending on the type of treatment we choose?3

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TERMINOLOGY

“What's in a name? That which we call a rose by any other name would smell as sweet.”

—Juliet Capulet from Romeo & Juliet by William Shakespeare

As our work progressed, it became obvious to us that a major problem with research on this topic had to do with the lack of uniform terminology. Although a rose by any other name may still be a rose, Shakespeare never had to do a literature search to find all the articles written about roses. If he had, he would have wished for a single term to look up, as we did for this focus issue. Little did we know when we started this project that one of our greatest challenges would turn out to be the lack of uniformity in the nomenclature of the pathological findings that develop at a segment adjacent to a previously operated segment. Such findings go by many names in the literature, including: adjacent segment degeneration, disease, deformity, fracture, adjacent level ossification development, and proximal junctional kyphosis. Substitute the words “proximal/distal junctional or superjacent/subjacent” for the words adjacent segment and there are another group of words that can be used to describe these findings. The nomenclature lacks standardization, making it difficult to do a comprehensive search and understand exactly what the authors mean. Lack of standardized terminology also leads to confusion for clinicians, patients, payers, and others.

Imprecision in definitions results in imprecision in classification and analysis. For this reason, we have proposed a simple, descriptive terminology: ASP as the general term to describe changes that occur adjacent to a previously operated level. Under this heading, “radiographical ASP” (RASP) refers to radiographical changes that occur at the adjacent segment. Strictly speaking, RASP would exclude magnetic resonance images (MRIs), because an MRI is not a radiograph. However, in the modern era, the terms “radiology, radiograph, and radiologist” have taken on a more expanded connotation. Hence, a radiologist does not only interpret radiographs but also MRIs and ultrasonographs. Similarly, MRIs and ultrasonographs are considered “radiological” modalities that a “radiology” department offers. We think that RASP would be understood to refer to all imaging modality changes. “Clinical ASP” (CASP) refers to clinical symptoms and signs that occur at the adjacent segment, which almost always are associated with RASP.

Why not simply keep some of the terms already utilized such as “adjacent level degeneration or disease?” Because these terms have ambiguous definitions and are incomplete representations of multifactorial processes, which may involve some or several if not all components of a motion segment, or the vertebral body itself or the accompanying neural elements. To continue the use of previously used terms utilized interchangeably in past publications would have meant to simply continue the confusion. Hence ASP, RASP, and CASP provide clear, encompassing, and unencumbered new operative concepts, which allow us to hopefully move forward. The new approach to terminology will finally also provide a rational start to categorizing findings that can be used to create a logical classification system.

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MATERIALS AND METHODS

The methods for each systematic review in this focus issue are described in detail in a separate article.4 Briefly, we invited nearly 30 expert spine surgeons, neurosurgeons, and epidemiologists to participate in this focus issue. We sought to answer nearly 40 clinical questions surrounding ASP, which are addressed in the 14 articles that make up this Focus Issue.

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IMPLICATIONS

It is important for the reader to understand that the majority of the clinical questions addressed in this Spine focus issue explore the risks “of” and risk factors associated “with” a single entity: ASP. ASP could be one of the major factors in reoperations of patients who have received fusions. Avoidance of reoperations is an emerging battleground in the quest to reduce health care spending and improve patient safety and quality of life. Simplistic prevention efforts of ASP, such as simply fusing more levels during the index procedure at the cost of increased upfront patient morbidity and other invasiveness-related outcomes are simply not acceptable or realistic propositions. The ultimate surgical cure for ASP would be a fusion from the occiput to the sacrum—obviously not advisable for the vast majority of patients. Acceptance of some ASPs may be a necessity, especially in the very young or the very elderly patient with multilevel radiographical pathology, where a single symptomatic level procedure may be indicated.

It is not the intent of this supplement to establish patient care guidelines. Such guidelines are traditionally developed after a systematic evaluation of treatment safety and efficacy, and finally culminate in strong or weak recommendations. Guideline development requires an evaluation of the therapeutic benefits and harms of a given treatment and consideration of economic implications. Similarly, functional outcomes and other complications were not assessed in this project. Hence, the consensus statements and clinical recommendations made in this focus issue are not designed to recommend one treatment or another but rather to inform both the surgeon and the patient about the potential risk for ASP as well as considerations for how they might minimize this risk. We think that this information may be helpful in the consenting and shared decision-making process in the future because ASP data have generally not been available in studies comparing treatments.

To date, formal evidence-based assessment groups such as the GRADE (Grading of Recommendations Assessment, Development and Evaluation) working group has not provided formal guidance regarding the application of the GRADE system to questions on prognosis or risk factor evaluation or recommendations about these. According to their website (http://www.gradeworkinggroup.org/), “The GRADE Working Group began in the year 2000 as an informal collaboration of people with an interest in addressing the shortcomings of present grading systems in health care. The working group has developed a common, sensible and transparent approach to grading quality of evidence and strength of recommendations.”

The GRADE perspectives on the implications of a “strong” recommendation are given further with general considerations for studies of prognosis that were thought to be logical for this supplement:

  • Patients: Most people in this situation would want the recommended course of action and only a small proportion would not.
  • Considerations for risk/prognosis: Most people would find the risk acceptable when weighed against the benefits and costs. The assumption is that both benefits and risks are discussed with patients as part of shared decision making.
  • Clinicians: Most patients should receive the recommended course of action.
  • Considerations for risk/prognosis: Most clinicians are comfortable with the risks when weighed with the benefits and cost.
  • Policy makers: The recommendation can be adapted as a policy in most situations.
  • Considerations for risk/prognosis: The risks should not preclude policy adoption based on demonstrated benefits and reasonable cost.

These considerations have not been evaluated beyond this supplement, but seem logical given the subject matter.

Finally, for the majority of the topics in this issue, there was a dearth of high-quality articles that could be used to answer the clinically important questions that the expert panels raised. Not surprisingly, our investigators noted that further investigation was necessary. However, we hoped to increase awareness of factors and circumstances surrounding ASP and provide constructive insights into future investigations. It is our sincere hope that the readership uses this focus issue as a launching point for further investigations on this very important topic. The 14 article titles, their key clinical questions, and their respective consensus statements or clinical recommendations can be found in the Table 1 of this article.

TABLE 1-a

TABLE 1-a

TABLE 1-b

TABLE 1-b

TABLE 1-c

TABLE 1-c

TABLE 1-d

TABLE 1-d

TABLE 1-e

TABLE 1-e

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CONCLUSION

Not surprisingly, the hope to find simple answers for causes of ASP or potential prevention strategies proved futile. We have not been able to conclusively answer the question as to whether ASP is a natural degenerative process or an iatrogenic one, which one can delay with an ideal operation. Although no amount of meticulous attention to detail is likely to prevent it, it is hoped that it may be possible to delay it by reducing the mechanical forces acting on the adjacent segment and maximizing normal kinematics as much as possible.

We hope to have helped the field by providing a more standardized nomenclature with the new acronyms “ASP,” “RASP,” and “CASP.” Clarification of the operational words we choose to describe what we see, treat, and investigate in the spinal motion segments surrounding our primary target levels will over time hopefully result in tangible improvements to our patients, spine clinicians, and researchers. Beyond this, a formal approach to categorizing the severity of ASP through systematic and validated severity scales remains an achievable next step.

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References

1. Anderson C. Spondyloschisis following spine fusion. J Bone Joint Surg Am 1956;38-A:1142–6.
2. Unander-Scharin L. A case of spondylolisthesis lumbalis aquisita. Acta Orthop Scand 1950;19:536–44.
3. “Disease.” Wikipedia, http://en.wikipedia.org/wiki/Disease, Accessed July 2012.
4. Norvell DC, Dettori JR, Skelly AC, et al. Methodology for the systematic reviews on adjacent segment pathology. Spine 2012;37:S10–S17.
© 2012 Lippincott Williams & Wilkins, Inc.