Estimation of cervical spine involvement in rheumatoid arthritis (RA) is between 17% and 88% of patients.¹ According to 1 review, up to 86% of patients — particularly patients with inadequate treatment or severe RA — experience symptoms of cervical spine involvement.² Researchers attribute this involvement to “intense chronic synovitis” occurring in joints.² Among patients with RA with cervical involvement, stroke and sudden death have been reported, resulting from vertebrobasilar insufficiencies.²

Craniovertebral Junction Involvement in RA

Housing vital vascular and neural structures, the craniovertebral junction (CVJ) comprises the occipitoatlantal and atlantoaxial segments, responsible for the majority of spinal rotation, flexion, and extension.³ As a surgical site, the CVJ is exceptionally complex and requires a deep understanding of vascular, ligamentous, and bony anatomy.⁴

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When present, cervical spine involvement typically presents in long-standing RA (mean 10 years disease duration),¹ with the most common clinicopathological presentations including atlantoaxial subluxation, cranial settling, and subaxial subluxation.¹

According to Rosario Maugeri, MD, PhD, of the University of Palermo, “Cervical spine involvement in RA is often a silent condition. Even in the presence of severe cervical spine damage, many patients may be asymptomatic.”¹

Although nonsurgical management of cervical spine involvement is the primary goal for clinicians, surgical treatment should be considered in the face of neurological symptoms.¹ “These surgeries should be performed at centers with experience in treating CVJ abnormalities,” Dr Maugeri and colleagues cautioned. Considerations include skilled preoperative evaluation, appropriate choice of surgical procedure, and the use of stabilization instruments.¹

Surgical Overview and Risks

Among patients indicated for surgery, researchers advocate for early surgical intervention to best safeguard the “vital” structures housed in the CVJ.⁵ Challenges in surgery are complicated by the variety of anomalies that patients may present with, including congenital bone malformations, intradural and extradural tumors, and the presence of RA or ankylosing spondylitis.⁵

While Dr Maugeri and colleagues recommend that even asymptomatic patients undergo X-ray evaluation, computed tomography scanning is considered the gold-standard for visualization and identification of bone changes, including erosions, anatomy, ankylosis, and spondylosis.¹ Magnetic resonance imaging can provide the most sensitive evaluation of soft tissue and neural elements and should be performed in all patients with either suspected or confirmed signs of cervical involvement.¹

Several surgical routes and approaches have been developed to best gain access to the CVJ, including the ventral approach, the endoscopic endonasal skull base approach, the endoscopic endonasal transclival transodontoid approach, the far/extreme lateral approach, and the dorsal approach.⁵ Numerous radiological and surgical lines — including McRae’s Line, McGregor’s Line, Ranawat’s Line, and the Redlund-Johnell Method — have been assessed and are reliable angles from which clinicians can analyze a patient’s CVJ anatomy prior to surgery.⁵

In cases requiring occipitocervical reconstruction, cervical pedicle screws may be used to normalize basilar invagination. While indirect posterior reconstruction can be effective, researchers have noted several potential issues, including late subaxial lesions, particularly among patients with RA.⁶

A study published in the Asian Spine Journal sought to clarify the risk factors for fusion-segment-extended reconstruction in response to late subaxial lesion.⁶ One hundred and thirteen patients with RA underwent occipitovertical reconstruction; fusion-segment-extended reconstruction was required 9 times in 7 patients.⁶ In particular, the subset of patients who underwent occipito-subaxial cervical reconstruction were at an elevated risk for fusion-segment-extended reconstruction procedures.⁶

Ultimately, surgical intervention for CVJ involvement in RA is a complex decision that should be individualized to each patient. “A successful surgical procedure requires a great deal of expertise,” Dr Maugeri noted, adding that despite advancements, surgical management of RA “remains a challenging field.”¹ 

Imaging Techniques

As surgical techniques continue to develop, researchers have started to examine the feasibility and efficacy of using 3D-printed models to assist in CVJ surgeries. One study,⁷ published in the Journal of Neurosurgery: Spine examined the use of these 3D models specifically in posterior screw fixation procedures.

“Individualized 3D models have been used in the field of kidney transplantation and pediatric otolaryngology, but their use has rarely been reported in the field of CVJ abnormality,” wrote Fangyou Gao, MD, of the Department of Neurosurgery at the Guizhou Provincial People’s Hospital in Guizhou Province, China, and colleagues.⁷

Dr Gao and colleagues assessed outcomes from 44 patients with CVJ abnormalities and who underwent surgery. The diagnosed CVJ abnormalities included atlantoaxial dislocation, Arnold-Chiari malformations, atlanto-occipital assimilation, basilar invagination, syringomyelia, platybasia, or an incomplete cervical segment. Using preoperative thin-slice CT scanning, image reconstruction, CT angiography, and data collection, investigators were able to create 38 individualized 3D-printed models, which were then used to further evaluate patients’ abnormalities and to simulate screw implantation.

Following surgery, Dr Gao and colleagues found that surgery was successful in the 38 patients who had 3D-printed models made; no accidents or intraoperative mistakes, including injuries of the vertebral artery, were noted.

“[S]urgery that was performed based on the individualized 3D-printed models was successful, without any medical errors or complications,” wrote Dr Gao. “Preoperative simulation of screw placement on the individualized 3D-printed model provides an important guidance for the surgery and offers many advantages, because it is simple to make, convenient, and can be touched.”⁷ 

Another study, published in the Acta Neurochirurgica supplement, examined the case of an endoscopic endonasal odontoidectomy using a high-definition 3D endoscope.⁸ The high-definition 3D endoscope is a new instrument allowing surgeons to overcome the problems associated with the 2D visualization of the surgical field.⁸ 

“Along with the classic transoral approach, the endoscopic endonasal approach has evolved and is gaining growing success,” wrote Paolo Pacca, MD, of the Division of Neurosurgery at the University of Turin in Italy, and colleagues. “The latter, in fact, has been shown to be safe and effective, avoiding the need for tongue retraction, upper airway swelling, and the need for palate splitting.”⁸

Moving Forward in the Field

Much of the current research provides clinicians with just a glimpse of the field of CVJ management and surgical techniques, which Acta Neurochirurgica editor Massimiliano Visocchi, MD, of the Institute of Neurosurgery at the Catholic University of Rome in Italy, said is “full of no man’s lands that deserve to be better investigated.”

“Perfect knowledge of CVJ anatomy and physiology allows us to better understand instrumentation procedures of the occiput, atlas, and axis, and the specific diseases that affect the region,” he wrote.⁴ Despite the current challenges, Dr Visocchi is confident that the CVJ is “one of the most fascinating surgical fields of the future.”⁴

References

1. Ferrante A, Ciccia F, Giammalva GR, et al. The craniovertebral junction in rheumatoid arthritis: state of the art. In: Visocchi M, ed. New Trends in Craniovertebral Junction Surgery, Acta Neurochir Suppl. New York, NY: Springer Nature. 2019;125:79-85.

2. Joaquim AF, Ghizoni E, Tedeschi H, Appenzeller S, Riew KD. Radiological evaluation of cervical spine involvement in rheumatoid arthritis. Neurosurg Focus. 2015;38(4):E4.

3. Lopez AJ, Scheer JK, Leibl KE, Smith ZA, Dlouhy BJ, Dahdaleh NS. Anatomy and biomechanics of the craniovertebral junction. Nurosurg Focus. 2015;38(4):E2.

4. Visocchi M. Why the craniovertebral junction? In: Visocchi M, ed. New Trends in Craniovertebral Junction Surgery, Acta Neurochir Suppl. New York, NY: Springer Nature. 2019;125:3-8.

5. Giammalva GR, Iacopino DG, Graziano F, et al. Surgical highways to the craniovertebral junction: is it time for a reappraisal? In: Visocchi M, ed. New Trends in Craniovertebral Junction Surgery, Acta Neurochir Suppl. New York, NY: Springer Nature. 2019;125:17-23.

6. Iwata A, Abumi K, Takahata M, et al. Late subaxial lesion after overcorrected occipitocervical reconstruction in patients with rheumatoid arthritis.  Asian Spine J. 2019;13(2):181-188.

7. Gao F, Wang Q, Liu C, Xiong B, Luo T. Individualized 3D printed model-assisted posterior screw fixation for the treatment of craniovertebral junction abnormality: a retrospective study. J Neurosurg Spine. 2017;27(1):29-34.

8. Pacca P, Tardivo V, Pecorari G, Garbossa D, Ducati A, Zenga F. The endoscopic endonasal approach to craniovertebral junction pathologies: surgical skills and anatomical study. In: Visocchi M, ed. New Trends in Craniovertebral Junction Surgery, Acta Neurochir Suppl. New York, NY: Springer Nature; 2019;125:25-36.