The effect of rheumatoid arthritis on the anatomy of the female cervical spine

Biologic Agents Preserve the C-2 Pedicle in Patients with Rheumatoid Arthritis: A Comparative Imaging Study Using Three-Dimensional Computed Tomography

OBJECTIVE

To investigate whether biologic agents (BAs) reduce a narrow C-2 pedicle screw trajectory, which is often a key stabilizer in surgical treatment, in patients with rheumatoid arthritis (RA).

METHODS

A total of 100 patients with RA treated with and without BAs (BA [+] group [n = 50] and BA [-] group [n = 50]), respectively, were included in the present study. Computed tomography (CT) images of their cervical spine, including C-2, were analyzed. The maximum screw diameter at C-2 that could be inserted without breaching the cortex, measured on 3-dimensional images using a CT-based navigation system, was compared between the groups with and without BA administration. Furthermore, the destruction of the atlantoaxial joint was examined using CT images. The risk factors for a narrow C-2 pedicle were elucidated among the patients treated with BAs.

RESULTS

The pedicle in the BA (+) group had a significantly larger C-2 maximum screw diameter than the BA (-) group (6.00 mm vs. 5.13 mm, P < 0.001), with less destruction of the atlantoaxial joint. Among the BA (+) group, a longer period until the initial administration of BAs and RA disease duration were associated with a narrow C-2 pedicle.

CONCLUSIONS

This study suggests that BAs can maintain the trajectory for C-2 pedicle screws, which acts as a key stabilizer in surgical management for the rheumatoid cervical spine, by halting the destruction of the atlantoaxial joint. Early introduction of BAs can be especially important to prevent the narrowing of the C-2 pedicle.

Morphometric Analysis of Subaxial Cervical Spine with Myelopathy: A Comparison with the Normal Population

Introduction

The specific morphology and differences between patients with cervical spondylotic myelopathy (CSM) and those with normal spines remain unclear. This study aimed to evaluate and determine the features of cervical spine morphology on reconstructive CT.

Methods

We investigated that axial reconstructive CT scans of the cervical spine at C3 to C7 were obtained from 309 individuals (97 CSM patients and 212 controls). Those of the optimal pedicle diameter were selected, and the following parameters were measured: (a) sagittal diameter of the spinal canal (b) transverse diameter of the spinal canal, (c) pedicle width, (d) lateral mass thickness, (e) transverse diameter of the foramen, (f) sagittal diameter of the vertebral body, and (g) transverse diameter of the vertebral body. The following ratios were calculated using these values: the sagittal-transverse ratio and the canal-body ratio.

Results

Most parameters differed significantly between the sexes in both groups. The parameters without the mean sagittal diameter of the spinal canal were significantly larger in men than in women. However, the mean sagittal diameter of the spinal canal did not differ significantly between the sexes in CSM patients. The sagittal-transverse ratio and canal-body ratio were significantly smaller in the CSM patients at all levels. According to relative operating characteristic curves of the sagittal diameter of the spinal canal, sagittal-transverse ratio, and canal-body ratio, the sensitivity from C3 to C7 in both sexes was > 60% at the threshold. In men, the specificity from C3 to C7 was also >60% at the threshold.

Conclusions

The morphometry of the sagittal diameter of the spinal canal, sagittal-transverse ratio, and canal-body ratio on axial reconstructive CT images appears useful for distinguishing cervical spinal canal stenosis involving myelopathy.

Risk of the high-riding variant of vertebral arteries at C2 is increased over twofold in rheumatoid arthritis: a meta-analysis

Rheumatoid arthritis (RA) might lead to atlantoaxial instability requiring transpedicular or transarticular fusion. High-riding vertebral artery (HRVA) puts patients at risk of injuring the vessel. RA is hypothesized to increase a risk of HRVA. However, to date, no relative risk (RR) has been calculated in order to quantitatively determine a true impact of RA as its risk factor. To the best of our knowledge, this is the first attempt to do so. All major databases were scanned for cohort studies combining words "rheumatoid arthritis" and "high-riding vertebral artery" or synonyms. RA patients were qualified into the exposed group (group A), whereas non-RA subjects into the unexposed group (group B). Risk of bias was explored by means of Newcastle-Ottawa Scale. MOOSE checklist was followed to ensure correct structure. Fixed-effects model (inverse variance) was employed. Four studies with a total of 308 subjects were included in meta-analysis. One hundred twenty-five subjects were in group A; 183 subjects were in group B. Mean age in group A was 62,1 years, whereas in group B 59,9 years. The highest risk of bias regarded "comparability" domain, whereas the lowest pertained to "selection" domain. The mean relative risk of HRVA in group A (RA) as compared with group B (non-RA) was as follows: RR = 2,11 (95% CI 1,47-3,05), I² = 15,19%, Cochrane Q = 3,54 with overall estimate significance of p < 0,001. Rheumatoid arthritis is associated with over twofold risk of developing HRVA, and therefore, vertebral arteries should be meticulously examined preoperatively before performing craniocervical fusion in every RA patient.

Prevalence of High-Riding Vertebral Artery: A Meta-Analysis of the Anatomical Variant Affecting Choice of Craniocervical Fusion Method and Its Outcome

OBJECTIVE

A high-riding vertebral artery (HRVA) has been defined as a C2 isthmus height of ≤5 mm and/or internal height of ≤2 mm measured 3 mm lateral to the border of the spinal canal. Its reported prevalence has varied widely. If overlooked during the approach for craniocervical fusion, injury to the vertebral arteries can occur, affecting the outcome. The present meta-analysis aimed to provide the pooled prevalence of HRVAs.

METHODS

A comprehensive database search was conducted by 3 of us. Peer-reviewed studies that had followed the strict definition for HRVAs and had reported its prevalence were included. The risk of bias was assessed using the anatomical quality assessment tool. The PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines were followed. The pooled prevalence was calculated using a random effects model.

RESULTS

The data from 20 studies with 3126 subjects (7496 sides) were analyzed. The overall pooled prevalence of ≥1 HRVA was 25.3% (95% confidence interval [CI], 19.6%-31.5%). The prevalence in those without the most important confounding factor, rheumatoid arthritis (RA), was 20.9% (95% CI, 16.5%-25.8%). Patients with RA had a prevalence of 42.9% (95% CI, 23.8%-63.1%). The difference between the non-RA and RA groups was statistically significant (P < 0.001, test of homogeneity, χ²). No geographical differences were noted (P = 0.20, test of homogeneity, χ²). Among those with HRVA, unilateral HRVA was present in 70.3% (95% CI, 65.2%-75.2%) and bilateral in 29.7% (95% CI, 24.8%-34.8%). No left or right side predilection was found (left, 50.8%; 95% CI, 33.8%-67.6%; right, 49.2%; 95% CI, 32.4%-66.2%).

CONCLUSIONS

Craniocervical fusion should be preceded by examination of the vertebral arteries at the level of C2 because the presence of HRVAs is common and might preclude the safe insertion of transarticular or transpedicular screws.

Dimensions of the Subaxial Lateral Mass: A Systematic Review of Anatomic (Morphometric) Measurement Studies

STUDY DESIGN

This was a systematic review.

OBJECTIVE

To review and synthesize information on subaxial lateral mass dimensions in order to determine the ideal starting point, trajectory, and size of a lateral mass screw.

SUMMARY OF BACKGROUND DATA

The use of lateral mass instrumentation for posterior cervical decompression and fusion has become routine as these constructs have increased rigidity and fusion rates.

METHODS

A systematic search of Medline and EMBASE was conducted. Studies that provided subaxial cervical lateral mass measurements, distance to the facet, vertebral artery and neuroforamen and facet angle made either directly (eg, cadaver specimen) or from patient imaging were considered for inclusion. Pooled estimates of mean dimensions were reported with corresponding 95% confidence intervals. Stratified analysis based on level, sex, imaging plane, source (cadaver or imaging), and measurement method was done.

RESULTS

Of the 194 citations identified, 12 cadaver and 10 imaging studies were included. Pooled estimates for C3-C6 were generally consistent for lateral mass height (12.1 mm), width (12.0 mm), depth (10.8 mm), distance to the transverse foramen (11.8 mm), and distance to the nerve. C7 dimensions were most variable. Small sex-based differences in dimensions were noted for height (1.2 mm), width (1.3 mm), depth (0.43 mm), transverse foramen distance (0.9 mm), and nerve distance (0.3-0.8 mm). No firm conclusions regarding differences between measurements made on cadavers and those based on patient computed tomographic images are possible; findings were not consistent across dimensions. The overall strength of evidence is considered very low for all findings.

CONCLUSIONS

Although estimates of height, width, and depth were generally consistent for C3-C6, C7 dimensions were variable. Small sex differences in dimensions may suggest that surgeons should use a slightly smaller screw in female patients. Firm conclusions regarding facet angulation, source of measurement, and method of measurement were not possible.

Vertebral Lateral Notch as Optimal Entry Point for Lateral Mass Screwing Using Modified Roy-Camille Technique

Study Design

Retrospective study of 37 consecutive female patients with cervical spondylotic myelopathy who underwent reconstructed computed tomography (CT) scanning of the cervical spine.

Purpose

The purpose of this study was to investigate whether the vertebral lateral notch of the cervical spine is an effective landmark to determine the entry point for lateral mass screwing. A modified Roy-Camille technique was used to determine the entry point associated with the lateral notch of the cervical spine.

Overview of Literature

The Roy-Camille technique has been a popular technique for the posterior fixation of the cervical spine. A problem with this technique is determining the entry point on the lateral mass via visual inspection, such as in cases with degenerative or destructive cervical facet joints.

Methods

Thirty-three female patients with cervical spondylotic myelopathy underwent reconstructed CT scanning of the cervical spine. Overall, 132 vertebrae from C3 to C6 were reviewed using reconstructed CT. The probable trajectory using a modified Roy-Camille technique was determined using reconstructed CT scans, and the optimal entry point was identified. Horizontal and vertical distances from the vertebral lateral notch were measured.

Results

The entry point determined using the modified Roy-Camille technique was significantly superior and medial compared with that determined using the conventional Roy-Camille technique. At C3 and C4 levels, the entry point using the modified technique was 1.4 mm below and 4.4 mm medial to the lateral notch, and at C5 and C6 levels, it was 2.3 mm below and 4.9 mm medial to the lateral notch.

Conclusions

The vertebral lateral notch of the cervical spine was an effective landmark to determine the entry point for lateral mass screwing. The modified Roy-Camille technique proposed here may prevent surgical complications and poor outcomes.