Original ArticleIncidence and Risk Factors of Postoperative Adjacent Segment Degeneration Following Anterior Decompression and Instrumented Fusion for Degenerative Disorders of the Cervical Spine
Introduction
Anterior decompression and instrumented fusion procedures, including anterior cervical discectomy and fusion (ACDF) and anterior cervical corpectomy and fusion (ACCF), are commonly used for treatment of degenerative cervical spondylotic radiculopathy and myelopathy, and satisfactory outcomes have been reported in many studies.1, 2, 3, 4 However, subsequent disc degeneration at levels adjacent to the fusion remains an important problem.5, 6, 7 Hilibrand and Robbins8 categorized adjacent segment degeneration (ASD) into 2 types: radiographic ASD and symptomatic ASD. The first type refers to radiographic degenerative findings at the adjacent motion segment and is not correlated with clinical symptoms. The second type refers to the development of new radiculopathy or myelopathy related to radiographic changes adjacent to the level of the previous anterior arthrodesis in the cervical spine. Hilibrand et al.9 reported an annualized incidence of 2.9% per year for developing symptomatic ASD after single-level ACDF and estimated that approximately 25.6% of patients would have symptomatic ASD within 10 years after first surgery.
Within the past few decades, both in vivo and in vitro biomechanical evidence has proven that arthrodesis may augment stress on the unfused adjacent levels and that the fusion segment, number of fusion levels, preexistence of degenerative changes at the adjacent segments, and alignment of the entire cervical spine are closely associated with ASD.10, 11, 12 However, other authors have suggested that ASD can be a sequela of the natural aging of patients and a natural progression of cervical disc disease, rather than a complication after spinal surgery.13 Whether the surgical intervention does influence the incidence of ASD and what the risk factors for ASD are after anterior cervical surgery remain widely controversial. The purpose of this study is to explore the incidence and risk factors of postoperative ASD following anterior decompression and instrumented fusion for degenerative disorders of the cervical spine to aid spinal surgeons in decision making and surgical planning.
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Patients
This retrospective study was approved by the Institutional Review Board of the Third Hospital of HeBei Medical University before data collection and analysis. The inclusion criteria included 1) degenerative cervical disc disease, including cervical radiculopathy and cervical spondylotic myelopathy, between C3 and C7 with at least 5 years of follow-up; 2) ACDF or ACCF; and 3) complete radiographic data, including cervical anteroposterior and lateral x-rays preoperatively, early in the
Results
Postoperative ASD was present in 68 of 283 patients (24.0%) at final follow-up; these patients presented with ASD above the surgical segment and comprised the ASD group. The mean follow-up duration was 6.6 years ± 0.8 (range, 5.1–8.3 years) in the ASD group and 6.3 years ± 0.7 (range, 5.2–8.0 years) in the no ASD group, demonstrating no significant difference (P = 0.79). The prevalence of radiographic ASD was 18.7% (53 patients), the prevalence of symptomatic ASD was 3.9% (11 patients), and the
Discussion
In the present study, 24.0% of the patients (68 of 283) experienced postoperative ASD. Two-level anterior cervical fusion and upper instrumented vertebra at C5 were significantly and independently associated with the occurrence of degeneration and could be assessed before surgery. Plate-to-disc distance <3.0 mm was also associated with ASD. These results were not confounded by other variables that potentially affect postoperative ASD.
A meta-analysis found that the prevalence of ASD in the
Conclusions
In this study, we found that upper instrumented vertebra at C5, plate-to-disc distance <3.0 mm, and 2-level anterior cervical fusion are risk factors for the occurrence of postoperative ASD. Our data are of value in decision making and surgical planning for spinal surgeons and patients with degenerative cervical disease.
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Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.