Atlantoaxial Facet Osteoarthritis: Inflammatory Facet Arthropathy C1-2 Level

Clinical Presentation

The patient is an 86-year-old man with prostate carcinoma who presented with history of several months of progressive right upper neck pain and recent development of suboccipital headaches. No pain or numbness reported in the upper extremities. Limited range of motion was observed in the right upper extremity. Otherwise, the physical examination was normal.

Imaging Presentation

Radionuclide bone scan reveals focal area of increased activity in right upper cervical spine region ( Fig. 33-1 ) . Otherwise the bone scan is normal. Magnetic resonance (MR) imaging obtained both without and with intravenous contrast enhancement reveals abnormal T1 and T2 signal intensity in and adjacent to the right C1-2 facets. Contrast enhancement is demonstrated in the C1-2 facets and adjacent bone marrow, in the periarticular soft tissues, and within the right C1-2 facet joint ( Figs. 33-2 to 33-4 ) . Findings indicate active right C1-2 inflammatory facet arthropathy (facet synovitis).

Figure 33-1

Active Inflammatory Facet Arthropathy (Facet Synovitis), C1-2 level.

Technetium-99m methylene-diphosphonate (MDP) bone scan. Posterior view. A focal area of increased uptake ( arrow ) overlies right upper cervical spine.

Figure 33-2

Active Inflammatory Facet Arthropathy, C1-2 level.

Same patient as in Figure 33-1 . Axial T1-weighted MR image A , obtained at the C2 level, reveals irregularity and T1 hypointensity of the right C2 superior articular facet ( arrows ). On contrast-enhanced fat-saturated T1-weighted MR image B , the right C2 facets, right C2 lateral mass, and tissues adjacent to the right C2 facets ( arrows ) enhance with contrast.

Figure 33-3

Active Inflammatory Facet Arthropathy, C1-2 level.

Parasagittal fat-saturated T2-weighted MR image A and contrast-enhanced fat-saturated T1-weighted MR image B , in same patient as in Figures 33-1 and 33-2 . The C1-2 facet joint ( arrow in A ) is narrowed and T2 hyperintense due to presence of joint effusion. T2 hyperintense marrow is located in the articular facets and lateral masses of C1 and C2 on the right ( small arrows in image A ). In image B , inflammatory tissue, in and adjacent to the right C1-2 facet joint, enhances with contrast. The bone marrow of the right lateral masses of C1 and C2 and periarticular soft tissues ( arrows in B ) also enhance with contrast.

Figure 33-4

Right C1-2 Active Inflammatory Facet Arthropathy and Peri-Odontoid Inflammation.

Same patient as in Figures 33-1 to 33-3 . In parasagittal image A , which is lateral to Figure 33-3B , the right C1-2 facet joint is widened and tissues in the facet joint ( between arrows ) enhance with contrast. Note small osteophytes arising anteriorly at C1-2 level ( arrows ). On parasagittal image B , which is medial to Figure 33-3B , the ligaments and tissues adjacent to C1-2 on the right enhance with contrast indicating presence of inflammation. On sagittal midline image C , the dens has been eroded and the prevertebral soft tissue and ligaments anterior and posterior to the dens ( arrows ) enhance indicating inflammation of these tissues.


Osteoarthritis commonly occurs in the cervical zygapophyseal (facet) joints in patients with advancing age. Any cervical level may be affected by facet osteoarthritis. Osteoarthritis has been reported to involve the atlantoaxial (C1-2) facet joints (also called the lateral atlantoaxial joints ) in approximately 4% of patients overall, and the prevalence increases significantly after the fifth decade of life.

Osteoarthritis involving the C1-2 facet joints can produce a distinct clinical syndrome characterized by limitation of neck rotation, severe upper neck pain, and occipital headaches. The patient may have suboccipital pain trigger points, suboccipital crepitus upon palpation, and a rotational head tilt deformity may be present. Upper neck pain and occipital neuralgia can also be secondary to osteoarthritis involving the atlantal-odontoid joint (anterior C1-2 joint). Lateral and anterior C1-2 osteoarthritis commonly coexist (see Figs. 33-3 and 33-4 ).

The joints between the lateral masses of C1 and C2 anatomically are considered to be zygapophyseal (facet) joints. These joints have some unique anatomic features that are not present in the lower cervical facet joints. The inferior C1 (atlas) articular facet is relatively flat, and this articulates with the relatively convex C2 (axis) superior articular facet. This incongruent configuration of the C1-2 articular facets results in a rather wide (3 to 5 mm) atlantoaxial facet joint space anteriorly and posteriorly. The shape of these joints and the relatively loose capsule that normally surrounds these joints imparts greater joint mobility to these joints than is possible at other cervical levels. The greatest degree of neck rotation occurs at this level.

Meniscus-like synovial folds are present within the C1-2 facet joints during infancy, but these folds usually involute and are not present in older children and young adults. As the atlantoaxial joints age or degenerate, meniscus-like synovial folds again develop that fill the incongruous spaces within the C1-2 joints. These folds are believed to provide stability to these joints. Such meniscal folds also develop in degenerated facet joints elsewhere in the spine.

The earliest findings in degeneration of the lateral atlantoaxial joints is superficial flaking of the articular cartilage. Thinning and fibrillation of the articular cartilage with associated facet cortical sclerosis and irregularity also occur as in any other degenerating facet joint. Eventually the joint space narrows and hypertrophic bone arises at the bone margins of the joint ( Figs. 33-5 to 33-8 ) .

Figure 33-5

Right C1-2 Facet Osteoarthritis.

Anteroposterior (AP) “Open mouth” radiograph shows marked narrowing of right C1-2 facet (zygapophyseal) joint ( arrow ) with sclerosis of adjacent articular facets. Left C1-2 facet joint space is mildly narrowed medially but relatively normal in size laterally.

Figure 33-6

Right C1-2 Facet Osteoarthritis.

Coronal CT image corresponding to AP radiograph in Figure 33-5 . The right C1-2 facet joint ( arrow ) is markedly narrowed, and adjacent articular facets are irregular due to subchondral erosions. Adjacent articular processes are sclerotic. Note large erosion along right lateral margin of dens ( D ). The left C1-2 facet joint is narrowed medially and adjacent facets are slightly sclerotic due to relatively mild osteoarthritis on the left.

Figure 33-7

Right C1-2 Facet Osteoarthritis, Marrow Edema in Adjacent Bone.

Axial fat-saturated T2-weighted MR images obtained at C1 level (image A ) and C2 level (image B ). Heterogeneous T2 hyperintense signal intensity, consistent with marrow edema, is located within the right C1 inferior facet/lateral mass ( arrows in image A ) and in the right C2 superior facet/lateral mass ( arrows in image B ). T2 hyperintense signal ( arrows in image B ) is located in the right C2 lateral mass and body of C2 on the right consistent with marrow edema.

Aug 25, 2019 | Posted by in NEUROLOGICAL IMAGING | Comments Off on Atlantoaxial Facet Osteoarthritis: Inflammatory Facet Arthropathy C1-2 Level
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