Date Published: May 31, 2019
Publisher: Public Library of Science
Author(s): Dong-Ho Lee, Jae Hwan Cho, Jin Il Jung, Jong-Min Baik, Deuk Soo Jun, Chang Ju Hwang, Choon Sung Lee, Jonathan H. Sherman.
To compare the clinical and radiological outcomes between patients with long posterior cervical fusion (PCF) in which fusion stopped at C7 versus patients in which fusion crossed the cervicothoracic junction (CTJ).
The patients were divided into 2 groups on the basis of the lower-most instrumented vertebra (LIV); C7 group patients (n = 25) and upper thoracic (UT) group (n = 21). We analyzed the visual analogue scale of arm/neck pain, Japanese Orthopedic Association (JOA) score, and neck disability index (NDI). And we also measured the following parameters: (1) pseudomotion of fused segments; (2) C2–C7 sagittal vertical axis; (3) T1 slope; and (4) C2–C7 lordosis.
Arm and neck pain were similar in both groups pre- and postoperatively. Interestingly, mean postoperative NDI score in the UT group was significant worse when compared with the C7 group (9.7±4.6 vs. 14.2±3.7, p = 0.006). Although UT patients had longer fusion levels, the fusion rates were not significantly different between the C7 and UT groups (96.0% vs. 90.5%; p = 0.577). The radiographic parameters did not show any significant differences between the groups at final follow-up.
Our study demonstrates that multi-level PCF stopping at C7 does not negatively affect C7-T1 segment failure, fusion rate, neck pain, neurologic outcomes, and global sagittal alignment of the cervical spine. Hence, it is unnecessary to extend the long PCF levels caudally across the healthy CTJ for fear of development of adjacent segmental disease (ASD) at the C7-T1 segment.
Long posterior cervical fusion surgery (PCF) is often performed for multi-level radiculopathy, myelopathy, or severe kyphotic deformity. And the increase in PCF procedures is likely related to an aging patient population, who are more likely to present with a greater severity of stenosis at multiple levels necessitating a posterior approach [1,2]. Also, incidence of posterior cervical fusions performed in the US has increased in all patients and in those with rheumatoid arthritis . Consistent with other junctional regions of the spine, the cervicothoracic junction (CTJ) has significant morphological variations due to the transition from the fairly mobile, lordotic cervical spine to the more rigid, kyphotic thoracic spine [4–8]. As a result, the CTJ experiences significant static and dynamic stress . Since the cervicothoracic junction (CTJ) represents a unique region that shifts from the mobile lordotic cervical spine to the rigid kyphotic thoracic spine, stopping long fusion at C7 may accelerate adjacent segmental disease (ASD), thus requiring revision surgeries at the C7-T1 segment. While surgeons commonly recommend extending cervical fusion into the thoracic spine to protect the adjacent levels, we did not find any direct evidence to support this procedure. Therefore, the purpose of this study is to compare the clinical and radiological outcomes between patients with long PCF in which fusion stopped at C7 versus patients in which fusion crossed the CTJ.
This study was an observational, retrospective cohort study approved by the Institutional Review Board of the Asan Medical Center, Ulsan university school of medicine, AMCIRB (protocol number 2018–0637). All data were fully anonymized before we accessed them and our IRB required informed consent. The patients were verbally informed about the objectives and were included only after reading and signing the written informed consent statement.
All surgical procedures were performed between the C2 to T3 levels, and the C7 group contains patients who underwent PCF surgery between C2 and C7 levels. On the other hand, twenty one patients of 46 underwent PCF surgery at least T1 level (UT group); LIVs, T1 (n = 13), T2 (n = 6), or T3 (n = 2). The operation cases for each group are presented at Fig 1 (C7 group) and Fig 2 (UT group).
The prevalence of clinical adjacent-segment pathology after cervical spine surgery has been reported to range from 1.6% to 4.2% per year, with reoperation rates for clinical adjacent segment pathology approximately 0.8% per year . And there are still many debates about the cause of ASD after spine surgery. Also, the etiology of radiographic ASD defined as degenerative findings at the adjacent segments found on imaging modalities and clinical ASD, defined as symptoms thought to be related to degenerative changes, remains a debate [11,12]. In vitro biomechanical studies have further evaluated the kinematic challenges that occur at the adjacent levels . In particular, biomechanical studies have shown increased intradiscal pressures in the C7-T1 segment after instrumentation of the lower cervical spine . However, other groups have recently claimed that the adjacent disc degeneration may simply be part of the natural progression of cervical spondylosis .
Our study demonstrates that multi-level PCF stopping at C7 does not negatively affect C7-T1 segment failure, fusion rate, neck pain, neurologic outcomes, and global sagittal alignment of the cervical spine. Of course, the sample size of this study was small and the follow-up period was only two years. So no complications such as ASD requiring treatment were found. However, our study shows that unnecessary long fusion across the cervicothoracic junction is likely to deteriorate postoperative neck function (worse NDI scores). These results suggest that cervical decompression and fusion without extending to the thoracic spine does not increase the rate of early adjacent segment disease or radiographic parameters, and that as demonstrated in the other cohort, surgeries extending into the thoracic spine may result with increased postoperative neck pain and therefore may be advisable to avoid.