eMedicine Specialties > Radiology > Musculoskeletal
Rheumatoid Arthritis, Spine: Imaging
Updated: Mar 25, 2009
Radiography
Findings
The mainstay of imaging the rheumatoid spine remains plain radiography. Flexion/extension views are necessary to assess the level of involvement and any evidence of instability. The need for further imaging by means of CT, MRI, or myelography may also be assessed during radiography.
Anterior AAS
Only half of patients with radiographic evidence of atlantoaxial subluxation (AAS) are actually symptomatic. The role of plain radiography is to establish whether there are risk factors for cord compression.
Anterior atlantodental interval
AAS is defined as an anterior atlantodental interval (AADI) greater than 2.5 mm in adults. This distance is measured as the interosseous distance between the posterior aspect of the arch of the atlas and the anterior aspect of the odontoid process. The point of measurement of the joint is a subject of debate: the inferior point is the most popular.
Plain lateral radiograph of the normal cervical spine taken in extension shows measurement of anterior atlantodental interval (yellow line) and posterior atlantodental interval (red line).
Lateral flexion view of the cervical spine shows atlantoaxial subluxation.
There may be a slight variation in normal measurements between men and women. More importantly, it should be noted that an atlantodental interval of less than 2.5 mm, which changes considerably on flexion and extension, may also be abnormal. An AADI of 3-6 mm indicates early instability and implies transverse ligament damage. An AADI of greater than 6 mm indicates that the alar ligaments are also damaged. Some authors consider an AADI of greater than 9 mm to be an indication for surgical stabilization.
Posterior atlantodental interval
Studies suggest that the posterior atlantodental interval (PADI) is a better method of assessing AAS because the PADI directly measures the spinal canal and therefore shows how much is narrowed by the subluxation. The PADI is the distance between the posterior surface of the odontoid and the anterior margin of the posterior ring of the atlas. At all cervical spinal levels, the cord requires a minimum canal width of 10 mm; the CSF, 2 mm; and the dura, 2 mm. Therefore, a minimum PADI of 14 mm is required to avoid cord compression. The normal spinal canal measures 17-29 mm at C1.
In 1993, Boden et al investigated the predictive value of the PADI and found that a value of less that 14 mm on plain radiographs had a 97% ability to detect patients with neurological deficit.13 Also, neurological recovery from surgery was unlikely if the PADI fell beneath 10 mm. Moreover, complete motor recovery occurred if the surgery was performed while the PADI was greater than 14 mm.
Detecting VS
Regarding the McGregor method, VS has been defined as the protrusion of the odontoid tip by more than 4.5 mm above the McGregor line.14 This is drawn between the posterosuperior aspect of the hard palate and the most caudal aspect of the occiput. However, it is not the most accurate of measurements in the rheumatoid spine due to odontoid erosion and often marked osteoporosis.
Lateral radiograph of a normal cervical spine shows the McGregor line. The odontoid tip should not protrude more than 4.5 mm above the line, which is drawn from the posterior edge of the hard palate to the most caudal point of the occiput.
Normal lateral magnified radiograph of the cervical spine shows the Ranawat method of detection of cranial settling. This method is used to measure the distance from the center of the pedicles (sclerotic ring) of C2 to a line drawn connecting the midpoints of the anterior and posterior arches of C1. (Normal values are 15 mm or greater for males and 13 mm or greater for females.)
The Ranawat index is used to assess vertical subluxation (VS) by detecting settling of C1 on C2. The measurement is made from the center of the pedicles of C2 to a line connecting the midpoint of the anterior and posterior arches of C1. Normal values are 15 mm or greater for men and 13 mm or greater for women. Anything less than this confirms VS.
Confirming subaxial subluxation
The diameter of the spinal canal is actually a better predictor of the development of paralysis than the degree of subluxation of 1 vertebral body on another. The normal sagittal diameter from C3 to C7 is 14-23 mm. A spinal canal sagittal diameter of at least 14 mm is critical at all levels in the cervical spine, as this is the minimum space required for the cord, CSF, and dura.
The cervical height index (CHI) is a method for assessing subaxial subluxation that takes into account the contribution of subluxations at multiple levels, together with loss of disk height and bony collapse. The CHI is calculated by first measuring the distance from the center of the sclerotic ring of C2 (as used in the Ranawat method) to the tip of the spinous process of C2. This distance is then divided into the distance from the center of the C2 sclerotic ring to the midpoint of the inferior border of C7 vertebral body. A CHI of less than 2 has a sensitivity and specificity approaching 100% in predicting neurologic compromise.
Lateral radiograph of the cervical spine shows how the cervical height index (CHI) is calculated. The distance from the center of the sclerotic ring of C2 to the tip of the spinous process of C2 (dotted line) is measured. This is then divided into the distance from the center of the sclerotic ring of C2 to the mid-point of the inferior border of the body of C7. A CHI of less than 2 mm is a sensitive predictor of neurologic deficit.
These plain radiographic measurements, along with dynamic flexion-extension views provide a reliable and efficient means of assessing spinal involvement of rheumatoid disease and targeting at-risk patients, as well as selecting those who warrant further radiological studies with a view to surgical stabilization.
Magnetic Resonance Imaging
Findings
The major role for CT and MRI is in the preoperative assessment of the 2 main indications for surgical intervention, namely neurologic deficit and severe pain.15,16 The subluxations that are of a degree likely to result in paralysis need to be identified, as better outcomes are recorded with earlier interventions. The effect of pannus and intracanal granulations on the cord cannot be accurately assessed on plain images, despite the fact that a posterior atlantodental interval (PADI) of less than 14 mm is a sensitive indicator of paralysis risk.
T1-weighted sagittal MRI of the cervical spine shows basilar invagination with cranial migration of an eroded odontoid peg. There is minimal pannus. The tip of the peg indents the medulla, and there is narrowing of the foramen magnum due to the presence of the peg. Inflammatory fusion of several cervical vertebral bodies is shown.
Sagittal T2-weighted MRI of the cervical spine in the same case as in Image above. The compromised foramen magnum is easily appreciated, and there is increased signal intensity within the upper cord; this is consistent with compressive myelomalacia. Further narrowing of the canal is seen at multiple levels.
Although CT scanning can document bone damage and alignment abnormalities, especially with more detailed multiplanar reconstruction, MRI has become the preferred modality for evaluation of the spinal cord and neural elements.17 It demonstrates the presence and effect of pannus on the spinal cord, and is useful in assessing its resolution following posterior fusion and stabilization. On MRI, the direct relationships of the odontoid to the medulla and brainstem can be documented. Spinal cord signal can be assessed; edematous changes in the cord are associated with a poor clinical status, as well as a poor prognosis and a poor postoperative outcome.18,19
The major indications for MRI in RA are abnormal measurements on plain radiographs,20 unremitting suboccipital/cervical pain, progressive/severe subluxations, symptoms of cord/brainstem compression, and vertebral-artery compression.
Dynamic MRI has been used with the patient in flexed or extended positions and in the traditional neutral position. Roca et al suggested that functional (flexed position) MRIs be obtained in patients with RA in whom cervical subluxation is suspected when routine MRI findings in the neutral position are normal.21 Others recommend functional MRI as a preoperative examination.22
Pathologic series have suggested that cord atrophy in rheumatoid cervical myelopathy results from repeated traction injury as a result of compression, stretch, and movement as opposed to an inflammatory process per se. This is unsurprising considering that the atlantoaxial joint is the most mobile segment of the cervical spine.
In a study looking at those features of rheumatoid cervical myelopathy on MRI that were associated with subsequent deterioration, it was found that where axial compression or impingement was present on MRI, 60% experienced a deterioration resulting in death or surgical intervention over a median period of 12 months.
When functional imaging is performed, patient monitoring is advised, and rapid sequences are desirable because patients may find the flexed position uncomfortable. Some authors suggest that functional MRI is unnecessary and even contraindicated in patients in whom medullary or spinal cord compression is discovered on studies made in the neutral position.
Degree of Confidence
The correlation of MRI findings with symptoms is crucial before any surgical decisions can be made. There is a close correlation between the severity of cervical myelopathy and the degree of compression, as demonstrated by MRI. Besides influencing the selection of patients for spinal surgery, MRIs can help in planning surgical procedures, especially those in patients with more than 2 levels of cord compression.
More on Rheumatoid Arthritis, Spine |
| Overview: Rheumatoid Arthritis, Spine |
 Imaging: Rheumatoid Arthritis, Spine |
| Follow-up: Rheumatoid Arthritis, Spine |
| Multimedia: Rheumatoid Arthritis, Spine |
| References |
| Further Reading |
| « Previous Page | Next Page » |
References
Cassar-Pullicino VN. The Spine in Rheumatological Disorders. Imaging. Vol 11. 1999: 104-18.
Resnick D, Kyriakos M, Greenway GD. Rheumatoid arthritis. In: Diagnosis of Bone and Joint Disorders. Vol 2. 4th ed. Philadelphia: WB Saunders;. 2002: 891-974.
Garrod AB. Nature and treatment of gout and rheumatic gout. London: Walton and Maberly;. 1859.
Oostveen JC, Roozeboom AR, van de Laar MA, Heeres J, den Boer JA, Lindeboom SF. Functional turbo spin echo magnetic resonance imaging versus tomography for evaluating cervical spine involvement in rheumatoid arthritis. Spine. Jun 1 1998;23(11):1237-44. [Medline].
Drosos AA, Lanchbury JS, Panayi GS, Moutsopoulos HM. Rheumatoid arthritis in Greek and British patients. A comparative clinical, radiologic, and serologic study. Arthritis Rheum. Jul 1992;35(7):745-8. [Medline].
Papadopoulos IA, Katsimbri P, Katsaraki A, et al. Clinical course and outcome of early rheumatoid arthritis. Rheumatol Int. Jul 2001;20(5):205-10. [Medline].
Pellicci PM, Ranawat CS, Tsairis P, Bryan WJ. A prospective study of the progression of rheumatoid arthritis of the cervical spine. J Bone Joint Surg Am. Mar 1981;63(3):342-50. [Medline].
Rudge SR, Drury PL, Lloyd-Jones JK. Long-term corticosteroids and cervical subluxation in non-rheumatoid patients. Rheumatol Rehabil. May 1981;20(2):102-5. [Medline].
Neva MH, Kauppi MJ, Kautiainen H, et al. Combination drug therapy retards the development of rheumatoid atlantoaxial subluxations. Arthritis Rheum. Nov 2000;43(11):2397-401. [Medline].
Kauppi MJ, Neva MH, Laiho K, Kautiainen H, Luukkainen R, Karjalainen A, et al. Rheumatoid Atlantoaxial Subluxation Can Be Prevented by Intensive Use of Traditional Disease Modifying Antirheumatic Drugs. J Rheumatol. Feb 2009;36(2):273-278. [Medline].
Hamilton JD, Johnston RA, Madhok R, Capell HA. Factors predictive of subsequent deterioration in rheumatoid cervical myelopathy. Rheumatology (Oxford). Jul 2001;40(7):811-5. [Medline].
Paus AC, Steen H, Røislien J, Mowinckel P, Teigland J. High mortality rate in rheumatoid arthritis with subluxation of the cervical spine: a cohort study of operated and nonoperated patients. Spine. Oct 1 2008;33(21):2278-83. [Medline].
Boden SD, Dodge LD, Bohlman HH, Rechtine GR. Rheumatoid arthritis of the cervical spine. A long-term analysis with predictors of paralysis and recovery. J Bone Joint Surg Am. Sep 1993;75(9):1282-97. [Medline].
McGregor M. The significance of certain measurments of the skull in the diagnosis of basilar impression. Br J Radiol. 1948;21:171-81.
Kelleher MO, McEvoy L, Yang JP, Kamel MH, Bolger C. Lateral mass screw fixation of complex spine cases: a prospective clinical study. Br J Neurosurg. Oct 2008;22(5):663-8. [Medline].
Cakir B, Käfer W, Reichel H, Schmidt R. [Surgery of the cervical spine in rheumatoid arthritis. Diagnostics and indication]. Orthopade. Nov 2008;37(11):1127-40; quiz 1141. [Medline].
Narváez JA, Narváez J, Serrallonga M, De Lama E, de Albert M, Mast R, et al. Cervical spine involvement in rheumatoid arthritis: correlation between neurological manifestations and magnetic resonance imaging findings. Rheumatology (Oxford). Dec 2008;47(12):1814-9. [Medline].
Dvorak J, Grob D, Baumgartner H, et al. Functional evaluation of the spinal cord by magnetic resonance imaging in patients with rheumatoid arthritis and instability of upper cervical spine. Spine. Oct 1989;14(10):1057-64. [Medline].
Janssen H, Weissman BN, Aliabadi P, Zamani AA. MR imaging of arthritides of the cervical spine. Magn Reson Imaging Clin N Am. Aug 2000;8(3):491-512. [Medline].
Roche CJ, Eyes BE, Whitehouse GH. The rheumatoid cervical spine: signs of instability on plain cervicalradiographs. Clin Radiol. Apr 2002;57(4):241-9. [Medline].
Roca A, Bernreuter WK, Alarcón GS. Functional magnetic resonance imaging should be included in the evaluation the cervical spine in patients with rheumatoid arthritis. J Rheumatol. Sep 1993;20(9):1485-8. [Medline].
Weissman BN, Aliabadi P, Weinfeld MS, et al. Prognostic features of atlantoaxial subluxation in rheumatoid arthritispatients. Radiology. Sep 1982;144(4):745-51. [Medline].
[Best Evidence] Mertens M, Singh JA. Anakinra for rheumatoid arthritis. Cochrane Database Syst Rev. Jan 21 2009;CD005121. [Medline].
[Best Evidence] Salliot C, Dougados M, Gossec L. Risk of serious infections during rituximab, abatacept and anakinra treatments for rheumatoid arthritis: meta-analyses of randomised placebo-controlled trials. Ann Rheum Dis. Jan 2009;68(1):25-32. [Medline].
[Best Evidence] Hagen KB, Byfuglien MG, Falzon L, Olsen SU, Smedslund G. Dietary interventions for rheumatoid arthritis. Cochrane Database Syst Rev. Jan 21 2009;CD006400. [Medline].
Further Reading
Related eMedicine topics
Rheumatoid Arthritis
Rheumatoid Arthritis, Hands
Juvenile Rheumatoid Arthritis
Clinical guidelines
Ophthalmologic examinations in children with juvenile rheumatoid arthritis. American Academy of Pediatrics. 2006 May 1. 3 pages. NGC:004963
Ottawa Panel evidence-based clinical practice guidelines for therapeutic exercises in the management of rheumatoid arthritis in adults. Ottawa Panel - Independent Expert Panel. 2004 Oct. 39 pages. NGC:004019
Ottawa Panel evidence-based clinical practice guidelines for electrotherapy and thermotherapy interventions in the management of rheumatoid arthritis in adults. Ottawa Panel - Independent Expert Panel. 2004 Nov. 28 pages. NGC:004020
Rituximab for the treatment of rheumatoid arthritis. National Institute for Health and Clinical Excellence (NICE) - National Government Agency [Non-U.S.]. 2007 Aug. 26 pages. NGC:005902
Abatacept for the treatment of rheumatoid arthritis. National Institute for Health and Clinical Excellence (NICE) - National Government Agency [Non-U.S.]. 2008 Apr. 29 pages. NGC:006483
Clinical trials
RESTART C0168Z05 Rheumatoid Arthritis Study
Evaluation of EULAR-RAID Score in Rheumatoid Arthritis Patients
Clinically Important Changes in Rheumatoid Arthritis
Ultrasonography as a Biomarker in Early Rheumatoid Arthritis
Health Outcomes in Rheumatoid Arthritis
Long-Term Evaluation of African Americans With Early Rheumatoid Arthritis (The CLEAR Study)
Keywords
spinal arthritis, spinal rheumatoid arthritis, spinal RA, early RA, early rheumatoid arthritis, erosion formation, pseudocyst formation, advanced RA, advanced rheumatoid arthritis, rheumatoid factor, RhF, course I rheumatoid arthritis, monocyclic rheumatoid arthritis, course II rheumatoid arthritis, polycyclic rheumatoid arthritis, course III rheumatoid arthritis, progressive rheumatoid arthritis, rheumatoid spondylitis, rheumatoid arthritis
