Background/Purpose: To investigate the frequency, location, nature, and clinical significance of subaxial involvement (below C1-C2) in a series of patients with rheumatoid arthritis (RA) and symptomatic involvement of the cervical spine.

Methods: Forty-one patients with RA were studied with cervical spine MRI. A comparative study of the incidence of the different types of subaxial lesions was also performed with respect to 41 age- and sex-matched patients with symptomatic cervical spondylosis.

Results: Stenosis of the spinal canal was found at the subaxial level in 85% of RA patients, and at the atlantoaxial level in 44%. The comparative study with cervical spondylosis revealed significant differences in the type and frequency of subaxial lesions (Table 1). In RA patients, subaxial stenosis seems to be the consequence of both the inflammatory activity of the disease (multilevel vertebral subluxations, inflammatory involvement of cervical spine ligaments, interapophyseal synovitis, bone marrow edema involving the vertebral plates and the interapophyseal joints, spinous process damage, and acquired vertebral blocks) and mechanical-degenerative changes (discopathy and ligamentum flavum hypertrophy).

Unconditional logistic regression analysis was used to identify MRI parameters of subaxial spine involvement associated with the development of neurological dysfunction (Ranawat class II or III). Evidence of alterations in the signal intensity of the spinal cord was the only independent risk factor found for the development of neurological dysfunction (p=.01; OR=11.43), increasing the risk 11-fold. There was a trend toward statistical significance for spinal cord compression (p=.06; OR=3.95). The presence of stenosis of the subaxial spinal canal without evidence of cord compression did not achieve statistical significance (p=.17). These data suggest that neurological manifestations correlate poorly with MRI findings at this level.

Table  1. Frequency  of subaxial lesions in patients with RA and Spondylosis.

	RA patients N = 41	Spondylosis N = 41	p  value
Stenosis of the subaxial canal	85%	27%	0.0000003
Spinal cord compression	34%	0%	0.0001
Alteration in signal intensity of the spinal cord	27%	0%	0.0003
Bone marrow edema involving the vertebral plates and the interapophyseal joints	27%	2%	0.003
Inflammatory involvement of cervical spine ligaments (interspinal ligaments and/or ligamentum nuchae)	32%	0%	0.0002
Interapophyseal or facet joint synovitis	17%	0%	0.012
Synovitis of the uncovertebral joints	0%	0%	–
Spinous process damage (sharpening, erosions, sclerosis or fusion)	7%	0%	NS
Pannus formation	0%	0%	–
Discopathy (disk bulging or disruption and/or herniation)	90%	98%	NS
Ligamentum flavum hypertrophy	66%	22%	0.0001
Degenerative spinal osteophytosis	71%	78%	NS
Vertebral subluxation	24%	5%	0.026
Vertebral ankylosis	24%	2%	0.007
Sclerosis and/or hypertrophy of the interapophyseal joints	0%	49%	0.000001
Sclerosis and/or hypertrophy of the uncovertebral joints	0%	17%	0.0012

 NS = not significant.

Conclusion: Subaxial stenosis seems to be the consequence of both the inflammatory process and mechanical-degenerative changes. Despite its frequency, it was not usually related to the occurrence of myelopathy symptoms, not even in cases with MRI evidence of spinal cord compression. These data seem to indicate a notable behavioral adaptation of this segment

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/subaxial-cervical-spine-involvement-in-symptomatic-rheumatoid-arthritis-patients-comparison-with-cervical-spondylosis/