How is atlantoaxial subluxation treated in patients with rheumatoid arthritis (RA) of the cervical spine?

Updated: Aug 13, 2019
  • Author: Steven R Garfin, MD; Chief Editor: Jeffrey A Goldstein, MD  more...
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Answer

Patients with AAS and no symptoms or signs of myelopathy can be observed when their lateral cervical radiograph shows a posterior atlantodental interval (PADI; the interval from the posterior aspect of the odontoid to the anterior margin of the lamina of C1) greater than 14 mm. Patients whose PADI measures less than 14 mm should have a magnetic resonance imaging (MRI) study to determine the true space available for the spinal cord. MRI findings of less than 13 mm of space available for the spinal cord and a cervicomedullary angle of less than 135° are generally indications for surgical stabilization.

The type of procedure performed is determined by whether or not the subluxation is reducible, the individual surgeon's preference and experience, and the patient's condition. If the deformity is reducible, posterior atlantoaxial fusion can be accomplished by a variety of techniques. [56]

Gallie reported a technique for posterior atlantoaxial arthrodesis in 1939, a technique that has been used with different modifications since then. [57]  In essence, the procedure consists of a block of autologous bone graft fixed by wire loop to the posterior arch of the atlas and the spinous process of the axis. Although technically straightforward to perform, rotational stability and translational stability are inferior to other techniques. The image below depicts a modified Gallie fusion.

Rheumatoid spondylitis. Modified Gallie fusion. No Rheumatoid spondylitis. Modified Gallie fusion. Note the H-shaped bone block wired over the spinous process of C2.

The Brooks fusion uses 2 posterior paramedian autologous structural grafts, usually attached with sublaminar wires. The bilateral fixation improves rotational stability. Multistrand titanium cables are increasingly favored over monofilament stainless steel wires because of greater strength and ease of contouring, as well as postoperative magnetic resonance imaging (MRI) and computed tomography (CT) scan imaging qualities. However, all techniques that use sublaminar wire or cable fixation have the potential risk of spinal cord injury during passage or from late failure of the implants. Additionally, the posterior arch of the atlas may be osteoporotic or partially deficient, thereby limiting its use. The image below depicts a Brooks-type fusion.

Rheumatoid spondylitis. Brooks-type fusion. Rectan Rheumatoid spondylitis. Brooks-type fusion. Rectangular structural grafts are beveled to fit between the arches of C1 and C2; then they are secured by bilateral doubled-twisted wires.

Immediate multidirectional stability can be achieved by C1-C2 transarticular screw fixation, as shown in the following image. [58]

Rheumatoid spondylitis. C1-C2 transarticular screw Rheumatoid spondylitis. C1-C2 transarticular screw fixation. Courtesy of Steven R. Garfin.

The screws are inserted posteriorly by entering the inferior aspect of the facet of C2, crossing the C1-C2 facet joint, and then entering into the lateral mass of C1. Safe insertion requires thorough understanding of the upper cervical anatomy and exposure of the medial border of the C2 pedicle. [59]  A preoperative CT scan should be reviewed carefully, because some C2 pedicles may have a small diameter, the lateral mass may be partially resorbed, or the vertebral artery may course superomedially. These conditions preclude safe transarticular screw placement. If there is good bone in the lateral masses, the patient may require only a cervical collar. However, patients with poor fixation may require a halo device postoperatively.

Patients with irreducible deformity and posterior compression can be treated with a C1 laminectomy and transarticular stabilization. Patients who have irreducible deformity and bony anterior compression may be decompressed by an anterior transoral approach, particularly in end-stage conditions. [60, 61]  This route has several difficulties, such as limited opening of the mouth in patients with concomitant temporomandibular disease, postoperative infection, and pharyngeal mucosal edema. However, several authors have reported good results using this procedure. This technique is generally followed by posterior stabilization as a 2-stage, same-day procedure.

Iacoangeli and colleagues reported that endoscopic endonasal odontoidectomy (EEO) with anterior C1 arch sparing provided satisfying long-term results for irreducible ventral craniovertebral junction (CVJ) lesions in 17 patients with rheumatoid arthritis. Moreover, the preservation of anterior C1 arch and the reconstruction of anterior CVJ prevented the need for posterior fusion in 2 patients. [62]

Patients who are healthier (Ranawat class I and class II) (see Classification of Neurologic Deficits) may be treated adequately with atlantoaxial stabilization and fusion alone, even in the presence of irreducible deformity. Some authors recommend that patients with anterior cord compression from a proliferative retrodental pannus be treated with ventral transoral decompression. However, there has been documented resorption of a retrodental pannus if a stable posterior fusion is achieved. [63]  Of these options, initial treatment with a posterior fusion followed by MRI and clinical follow-up is the most common. If the pannus does not resorb and neurologic deficit persists, late transoral decompression can be performed.


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