To evaluate cervical facet joint degeneration using a newly developed classification, investigate its prevalence and relationship with cervical degenerative spondylolisthesis, and clarify its clinical significance in patients with degenerative cervical myelopathy (DCM).
This study included 145 consecutive patients with DCM who underwent surgical treatment. Clinical variables and radiological findings were analyzed. A new 6-grade computed tomography (CT) classification for cervical facet joint degeneration was adapted, and its prevalence was evaluated by categorizing the joints into those at responsible and those at nonresponsible spinal segmental levels. We evaluated the association between rapidly progressive myelopathy and the presence of significant facet joint degeneration or spondylolisthesis at the responsible segmental level.
Finally, 140 patients with a mean age of 64.1 ± 12.8 years were analyzed. The prevalence of grade 1, 2, 3, 4, 5A, and 5B classification in all facet joints was 72.0%, 9.5%, 10.9%, 4.3%, 2.9%, and 0.4%, respectively. There was a statistically significant difference in the distribution of CT grades between the joints at the responsible and nonresponsible segmental levels (p < 0.001), with a high prevalence of grade 4 or 5B degeneration at the responsible segmental level, reflecting articular irregularity. There was also a statistically significant relationship between rapidly progressive myelopathy and grade 4 or 5B degeneration at the responsible segmental level (p < 0.001), but not between rapidly progressive myelopathy and spondylolisthesis (p = 0.255).
This novel CT classification for facet joints deserves additional evaluation in patients with DCM. Abnormal findings on the articular surfaces might be related to the progression of myelopathy.
Degenerative cervical myelopathy (DCM), including cervical spondylotic myelopathy, is a common age-related spinal disorder. DCM is mostly asymptomatic, but sometimes it becomes a symptomatic background pathology and reduces quality of life due to impairment of motor function [
The cervical facet joint is a synovial joint located in the posterolateral spine. Degenerative facet joint pathology is associated with cervical degenerative spondylolisthesis, which can induce myelopathy [
We recently reported a case of DCM with unilateral severe facet joint degeneration at the responsible spinal segmental level and rapid neurological deterioration without any trauma or cervical spondylolisthesis [
All experiments were conducted following the guidelines of the Declaration of Helsinki. All research protocols were approved by the Institutional Review Board of Nara Medical University (approval number: 2241). The need for informed consent was waived.
We retrospectively analyzed consecutive DCM patients who underwent surgical treatment at our institution between January 2013 and December 2020. Inclusion criteria included the responsible spinal segment being at the subaxial level between C2–3 and C6–7 and preoperative CT and radiography of the cervical spine. Patient who received revision surgery within 12 months was excluded. Clinical data, including responsible segmental level and radiological findings, were gathered retrospectively from medical records, preoperative neurologic examinations, and radiographic images. Regarding the clinical evaluation, the diagnosis of cervical myelopathy was made on the basis of symptoms first, but also on the magnetic resonance imaging (MRI) findings. The responsible segmental level was defined as the level of the lesion causing myelopathy and identified in each case based on the neurologic examinations first, and referring to the MRI findings if necessary. To study radiological classification as well as its clinical implications, the clinical course, especially concerning rapid progression of cervical myelopathy, was also investigated. Rapid progression of cervical myelopathy was defined in this study as in previous reports [
Preoperative CT of the cervical spine was performed on admission in each patient. Results were retrospectively reviewed and assessed. We carefully evaluated all cervical facet joints from the C2–3 to C6–7 levels on the axial, sagittal, and coronal sections. In short, 10 facet joints for 5 intervertebral levels were evaluated separately for each case. We classified them into 6 grades according to the severity of the following degenerative findings: osteophyte formation, joint hypertrophy, joint space narrowing, cyst formation, articular irregularity, ankylosing changes, and facet joint opening with articular irregularity (
To evaluate cervical spondylolisthesis, all intervertebral spaces from C2–3 to C6–7 in each patient were examined using a preoperative lateral radiogram of the cervical spine in the neutral position. We measured anterior-posterior translation of the upper vertebral body relative to the lower vertebral body. In this study, we defined cervical spondylolisthesis as 2 mm or more in the forward or backward direction.
This clinical study consisted of the 3 evaluations. First, we investigated the prevalence of cervical facet joint degeneration in all patients with DCM using the classification mentioned above. The prevalence of each CT grade at all spinal intervertebral levels was investigated. In addition, we compared the distribution of CT grades by dividing the joints into those at responsible or nonresponsible segmental levels to assess the impact of the CT classification on clinical diagnostic aspects and identify which type of degeneration is clinically significant in DCM. Second, we assess the clinical relationship between cervical facet joint degeneration and spondylolisthesis in patients with DCM. The patients whose evaluation of the lower cervical vertebra was impossible due to overlapping shoulders were excluded, and the assessment of each intervertebral space from C2–3 to C6–7 in the remaining patients were collected and investigated. By dividing the joints and intervertebral levels into at responsible and nonresponsible segmental levels, the prevalence of clinically significant cervical facet degeneration, as evaluated during the first step, and spondylolisthesis were assessed and compared. We also investigated the relationship between the presence of significant cervical facet degeneration on either side of both facet joints and spondylolisthesis at responsible and nonresponsible segmental levels, respectively. Third, we assessed the clinical impact of these 2 variables at the responsible segmental level on rapidly progressive myelopathy in patients with DCM. The same patients as in the second assessment were also involved. After dividing the patients into 2 groups according to the presence or absence of rapidly progressive myelopathy, we evaluated the association between rapidly progressive myelopathy and the presence of significant cervical facet degeneration or spondylolisthesis at the responsible segmental level, separately.
All statistical analyses were performed with IBM SPSS Statistics ver. 26.0 (IBM Co., Armonk, NY, USA). Radiological variables at each spinal levels were compared using the Pearson chi-square test, and relationships between the radiological variables were assessed using the McNemar test. The reproducibility of the CT classification was evaluated using Cohen kappa coefficient. Data are presented as means± standard deviation (SD). Statistical significance was defined as p <0.05.
Although 145 patients were enrolled, 140 patients were finally included in this study (
The overall prevalence of cervical facet degeneration is shown in
Evaluation of cervical spondylolisthesis was possible in 131 cases, because 9 patients were excluded for whom evaluation of the C6–7 vertebrae was impossible due to overlapping shoulders. Therefore, the following analysis was performed on 655 vertebrae. Spondylolisthesis of 2 mm or more was observed in 84 vertebrae (12.8%). Of the 131 patients with cervical myelopathy, 27 patients (20.6%) had rapid neurological deterioration before surgery. Therefore, 27 patients were classified into the rapid progression group and the remaining 104 patients into the slow progression group.
Grade 4 or 5B degeneration on either side of the cervical facet joints and spondylolisthesis were each observed with relatively high frequency at the responsible segmental level compared with nonresponsible levels. The prevalence of grade 4 or 5B degeneration in facet joints at the responsible level was 22.1% (29 out of 131 intervertebral levels), which was higher than 5.7% (30 out of 524 levels) at nonresponsible levels (p <0.001). The prevalence of cervical spondylolisthesis at the responsible level was 28.2% (37 out of 131 levels), which was also higher than 8.6% (45 out of 524 levels) at nonresponsible levels (p <0.001) (
Although there were similar trends for cervical facet joint degeneration and spondylolisthesis, there was no association between these 2 variables. There were no statistically significant differences between the presence of grade 4 or 5B degeneration on either side of both facet joints and the presence of spondylolisthesis at nonresponsible segmental levels (p = 0.142) (
In the investigation of the clinical impact of facet joint degeneration and cervical spondylolisthesis in patients with DCM, the prevalence of grade 4 or 5B degeneration on either side of the facet joint at the responsible segmental level was higher in the rapid progression group compared to the slow progression group (p <0.001). On the other hand, the prevalence of cervical spondylolisthesis at the responsible segmental level was higher in both the rapid and slow progression group, resulting in no statistical difference between the rapid and slow progression groups (
The present study investigated clinical significance of facet joint degeneration in patients with DCM, by comparing the joints at responsible versus nonresponsible segmental levels. This is the first detailed comparative study of the association between facet joint degeneration and spondylolisthesis in DCM. The newly developed CT classification reflecting articular irregularity had few intraexaminer differences, and facet joint degeneration with articular irregularity and spondylolisthesis were more prevalent at the responsible segmental level. Moreover, this study showed that facet joint degeneration with articular irregularity at the responsible segmental level is significantly associated with rapid progression of myelopathy than slow progression of myelopathy. Although both articular irregularity and spondylolisthesis were significantly more prevalent at the responsible than the nonresponsible segmental levels, no such trend was observed in spondylolisthesis. We were able to clarify the clinical significance of facet joint degeneration; the impact of articular irregularity at a responsible segmental level was particularly significant in the rapid progression of DCM.
Age-related degeneration of the spine causes decreased mobility, stabilization, and bony fusion. In contrast, it can also cause increased local mobility and pathological conditions with intervertebral instability. Because the facet joints, a component of the cervical spine, play a role in static and gliding cervical motion and facilitate cervical spine mobility [
Facet joint degeneration of the spine also occurs not only with osteoarthritic bony changes but also with articular surface degeneration [
There have been several attempts to classify cervical facet joint degeneration and determine its prevalence [
There has been a report on the prevalence of cervical facet joint degeneration based on a 4-grade CT classification of facet joint degeneration in the cervical spine: grade I, normal; grade II, degenerative changes including joint space narrowing, cyst formation, and small osteophytes without joint hypertrophy; grade III, joint hypertrophy; grade IV, bony fusion of the joint [
We also investigated differences among evaluators, since subdivision of CT grades may cause differences in classification. In this newly proposed CT classification, the investigation of intraexaminer differences showed almost perfect agreement, despite a significant difference in the number of years of clinical experience between examiners. Therefore, this classification is a useful tool in daily clinical practice for evaluating the degree of facet joint degeneration in a comprehensive and effective manner.
Previous studies evaluated the relationship between degeneration of facet joints and degeneration of other structures in the cervical spine. One study focused on degeneration of the vertebral disc, which is not associated with facet joint degeneration. Lee et al. [
On the other hand, cervical spondylolisthesis can be caused by severe facet degeneration [
The clinical impact of cervical facet joint degeneration on myelopathy has not been well debated, but there are few relevant studies. Even in these studies, the clinical impact has not been sufficiently examined because the studies included evaluation of images from a wide range of patients, such as patients without symptoms or neck pain only [
DCM occurs due to the interrelated involvement of many factors [
This study has several limitations. First, it used a retrospective design with a small number of patients. Second, it is uncertain whether the responsible segmental level was correctly identified in all patients. Third, the evaluation of cervical spondylolisthesis was not sufficient because there is no consensus on the definition of dynamic instability, which was not assessed in this study. Considering cervical spondylolisthesis, this study compared it only with articular irregularity of facet joints. It is speculated that patients who present with cervical spondylolisthesis at the responsible segmental level often have a low grade of facet degeneration. In addition, the spondylolisthesis in this study includes both forward and backward spondylolisthesis. Further studies are required on this point. Fourth, there is a pair of facet joints at each intervertebral height, and they do not always have the same degree of degeneration. If the contralateral facet joint was classified differently, it could have reduced the proportion of joints with grade 4 or 5B degeneration despite the presence of articular irregularity, which can underestimate the impact of facet joint degeneration with articular irregularity. Therefore, the clinical effect of grade 4 or 5B degeneration might be more significant. Despite these limitations, this study demonstrated the importance and clinical usefulness of evaluating cervical facet joint degeneration in patients with DCM.
This study was the first to focus on the potential importance of facet joint degenerative pathology and demonstrate the usefulness and reliability of a newly created CT classification of cervical facet joint degeneration in patients with DCM. The novel CT classification had few intraexaminer differences and deserves additional evaluation, suggesting that abnormal findings on articular surfaces might be related to the progression of myelopathy.
The authors have nothing to disclose.
This study received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
Conceptualization: YT; Data curation: YT; Formal analysis: YT; Methodology: YT; Project administration: HN; Visualization: AO, YT; Writing - original draft: AO; Writing - review & editing: YT, SY, FN, IN, YP.
Newly developed computed tomography classification for cervical facet joint degeneration. (A) Grade 1, normal facet joint with no degenerative changes. (B) Grade 2, mild degenerative changes with only osteophyte formation. (C) Grade 3, degenerative changes with osteophyte formation including joint space narrowing, microcyst (< 2 mm), or joint hypertrophy. (D) Grade 4, severe degenerative changes, including moderate to large cysts (≥ 2 mm), and articular irregularity. (E) Grade 5A, ankylosing changes with bony fusion of the facet joint. (F) Grade 5B, facet opening with articular irregularity.
Flow chart showing the patient selection process.
Prevalence of cervical facet joint degeneration by grade. (A) Prevalence of cervical facet joint degeneration. (B) Prevalence of cervical facet joint degeneration at responsible and nonresponsible segmental levels. There was a statistically significant difference between the 2 distributions (p < 0.001), with grade 4 or 5B degeneration being more prevalent at the responsible segmental level and grade 5A being more prevalent at nonresponsible levels. Grade 1, normal facet joint with no degenerative changes. Grade 2, mild degenerative changes with only osteophyte formation. Grade 3, degenerative changes with osteophyte formation including joint space narrowing, microcyst (< 2 mm), or joint hypertrophy. Grade 4, severe degenerative changes including moderate to large cysts (≥ 2 mm), and articular irregularity. Grade 5A, ankylosing changes with bony fusion of the facet joint. Grade 5B, facet opening with articular irregularity.
Prevalence of significant cervical facet degeneration and spondylolisthesis. The prevalence of grade 4 or 5B degeneration on either side of the facet joints at the responsible segmental level was 22.1%, which was higher than 5.7% at nonresponsible levels (p < 0.001). The prevalence of cervical spondylolisthesis at the responsible segmental level was 28.2%, higher than 8.6% at nonresponsible levels (p < 0.001). Grade 4, severe degenerative changes including moderate to large cysts (≥ 2 mm), and articular irregularity. Grade 5B, facet opening with articular irregularity.
Impact of cervical facet degeneration and spondylolisthesis on preoperative rapidly progressive myelopathy. The prevalence of grade 4 or 5B degeneration on either side of the facet joints at the responsible segmental level was significantly higher in the rapid progression group than in the slow progression group (p < 0.001). On the other hand, there were no statistically significant differences in the prevalence of cervical spondylolisthesis at the responsible level between the 2 groups (p = 0.195). Grade 4, severe degenerative changes including moderate to large cysts (≥ 2 mm), and articular irregularity. Grade 5B, facet opening with articular irregularity.
Clinical characteristics of the study participants (n=140)
Characteristic | |
---|---|
Age (yr) | 64.1 ± 12.8 |
Male sex | 93 (66.4) |
Disease | |
Cervical canal stenosis | 84 (60.0) |
Ossification of the posterior longitudinal ligament | 31 (22.1) |
Cervical disc herniation | 25 (17.9) |
Comorbid disorder | |
Hypertension | 54 (38.6) |
Diabetes | 31 (22.1) |
Current smoking | 52 (37.1) |
Responsible Spinal Segmental level | |
C2/3 | 3 (2.1) |
C3/4 | 29 (20.7) |
C4/5 | 49 (35.0) |
C5/6 | 52 (37.1) |
C6/7 | 7 (5.0) |
JOA score for cervical myelopathy | |
Before surgery | 11.7 ± 2.8 |
At 1 year follow-up | 14.2 ± 2.3 |
Values are expressed as mean±standard deviation or the number of patients (%).
JOA, Japanese Orthopaedic Association.
Cervical facet degeneration with articular irregularity and spondylolisthesis at each of the spinal levels
Nonresponsible level | Responsible level | Total | p-value |
|
---|---|---|---|---|
Grade 4 & 5B degeneration on either side of the facet joints | ||||
(+) | 30 | 29 | 59 | - |
(-) | 494 | 102 | 596 | - |
Total | 524 | 131 | 655 | < 0.001 |
Cervical spondylolisthesis (≥ 2.0 mm) | ||||
(+) | 45 | 37 | 82 | - |
(-) | 479 | 94 | 573 | - |
Total | 524 | 131 | 655 | < 0.001 |
Pearson chi-square test.
Relationship between cervical facet degenerations with articular irregularity and spondylolisthesis at the nonresponsible segmental level
Cervical spondylolisthesis (≥ 2.0 mm) |
Total | p-value |
||
---|---|---|---|---|
(+) | (-) | |||
Grade 4 & 5B degeneration on either side of the facet joints | ||||
(+) | 3 | 27 | 30 | - |
(-) | 40 | 454 | 494 | - |
Total | 43 | 481 | 524 | 0.142 |
McNemar test.
Relationship between cervical facet degenerations with articular irregularity and spondylolisthesis at the responsible segmental level
Cervical spondylolisthesis (≥ 2.0 mm) |
Total | p-value |
||
---|---|---|---|---|
(+) | (-) | |||
Grade 4 & 5B degeneration on either side of the facet joints | ||||
(+) | 8 | 21 | 29 | - |
(-) | 29 | 73 | 102 | - |
Total | 37 | 94 | 131 | 0.322 |
McNemar test.