Update on the evidence for adjacent segment degeneration and disease

Abstract

Background context

The evidence surrounding the topic of adjacent segment degeneration and disease has increased dramatically with an abundant amount of literature discussing the incidence of and techniques to avoid it. However, this evidence is often confusing to discern because of various definitions of both adjacent segment degeneration and disease.

Purpose

To organize and review the recent evidence for adjacent segment degeneration and disease.

Results

Although multifactorial, three distinct causes of adjacent segment disease in both the lumbar and cervical spine have been discussed: the natural history of the adjacent disc; biomechanical stress on the adjacent level caused by the fusion; and disruption of the anatomy at the adjacent level with the initial surgery. The incidence of adjacent segment degeneration in the lumbar spine has been widely reported in the literature from 0% to 100%; conversely, the reported incidence in the cervical spine is less variable. Similarly, strategies at avoiding adjacent segment disease in the lumbar spine include arthroplasty, dynamic fixation, and percutaneous fixation, whereas in the cervical spine the focus has remained on arthroplasty.

Conclusions

Adjacent segment disease and degeneration remain a multifactorial problem with several techniques being developed recently to minimize them. In the future, it is likely that the popularity of these techniques will be dependent on the long-term results, which are currently unavailable.

Introduction

The indications for arthrodesis of the lumbar and cervical spine have continued to expand with more fusion procedures being performed every year [1]. Only recently have surgeons become concerned with adjacent segment degeneration and disease, leading to several reports on the incidence of this relatively common problem [2], [3], [4], [5], [6], [7], [8], [9], [10]. Adjacent segment degeneration represents the radiographic changes of the intervertebral discs adjacent to the surgically treated levels, whereas adjacent segment disease is defined as the pathologic process associated with disc degeneration leading to clinical symptoms, such as radiculopathy, stenosis, and instability [11]. Furthermore, avoidance of adjacent segment disease has been a rationale for the development of total disc arthroplasty [12], and with the recent popularity of this new technology, the study of the adjacent segment disease has increased exponentially. Although the same terms are used for both the cervical and lumbar spine, the multifactorial process that leads to its development differs in these two regions.

One very significant question that remains to be answered is the extent to which the adjacent segment degeneration adjacent to an arthrodesis represents age-appropriate degeneration occurring because of natural history alone [13]. The objectives of this review were to discuss the recent literature on the incidence of and potential solutions for the adjacent segment degeneration and disease in the lumbar and cervical spine.