Subaxial subluxation after atlantoaxial transarticular screw fixation in rheumatoid patients

Abstract

The most common cervical abnormality associated with rheumatoid arthritis (RA) is atlantoaxial subluxation, and atlantoaxial transarticular screw fixation has proved to be one of the most reliable, stable fixation techniques for treating atlantoaxial subluxation. Following C1-C2 fixation, however, subaxial subluxation reportedly can bring about neurological deterioration and require secondary operative interventions. Rheumatoid patients appear to have a higher risk, but there has been no systematic comparison between rheumatoid and nonrheumatoid patients. Contributing radiological factors to the subluxation have also not been evaluated. The objective of this study was to evaluate subaxial subluxation after atlantoaxial transarticular screw fixation in patients with and without RA and to find contributing factors. Fortythree patients who submitted to atlantoaxial transarticular screw fixation without any concomitant operation were followed up for more than 1 year. Subaxial subluxation and related radiological factors were evaluated by functional X-ray measurements. Statistical analyses showed that aggravations of subluxation of 2.5 mm or greater were more likely to occur in RA patients than in non-RA patients over an average of 4.2 years of follow-up, and postoperative subluxation occurred in the anterior direction in the upper cervical spine. X-ray evaluations revealed that such patients had a significantly smaller postoperative C2-C7 angle, and that the postoperative AA angle correlated negatively with this. Furthermore, anterior subluxation aggravation was significantly correlated with the perioperative atlantoaxial and C2-C7 angle changes, and these two changes were strongly correlated to each other. In conclusion, after atlantoaxial transarticular screw fixation, rheumatoid patients have a greater risk of developing subaxial subluxations. The increase of the atlantoaxial angel at the operation can lead to a decrease in the C2-C7 angle, followed by anterior subluxation of the upper cervical spine and possibly neurological deterioration.

Sagittal balance of the cervical spine: an analysis of occipitocervical and spinopelvic interdependence, with C-7 slope as a marker of cervical and spinopelvic alignment

“…3 Recent studies stress that in addition to the clinical consequences of cervical malalignment, the geometry of the fusion of the upper cervical spine promotes alignment changes in the subaxial spine. 8,15 Matsunaga et al 14 have observed a higher incidence of subaxial cervical malalignment (kyphosis, swan neck deformity, or subluxation) among patients with occipitocervical fusion in an abnormal position. Yoshimoto el al.…”

Rheumatoid vertical and subaxial subluxation can be prevented by atlantoaxial posterior screw fixation

“…However, the question of whether RA patients are at risk for developing VS and/or SAS after AAS treatment is controversial. Several studies have shown that rheumatoid patients have a greater risk of developing SAS after atlantoaxial fixation using wiring systems or transarticular screws [9][10][11], and the authors emphasized that the risk factor for SAS may be subaxial kyphosis caused by atlantoaxial hyperlordosis. However, the development of SAS is regulated by multiple factors, including not only the mechanical effect of fixed atlantoaxial angle and secondary subaxial kyphosis, but also disruption of the extensor muscles in addition to a strong effect due to a natural history of RA.…”

“…Some authors have reported that the incidence of SAS in RA patients not surgically treated was 15-22 % [1,22,23] and of AAS was 18-61 % [1,22]. In patients who were surgically treated, a higher incidence of newly developed SAS and AAS after AA fusion using wiring systems or transarticular screws has been reported (32.7-39 % [9][10][11] and 100 %, respectively). It is suggested that the higher incidence of SAS after the surgery is probably due to mechanical stress caused by changes in cervical alignment, but there is a significant difference in RA status between patients with and without surgical treatment.…”

“…AA fixation has been proposed as a prophylactic procedure for VS, because the mechanical effect prevents the destruction of the lateral masses of the atlas from the inflammatory process [8]. On the contrary, fused mechanical limitations may occasionally become risk factors for SAS [9][10][11]. Thus, the question of whether atlantoaxial fusion achieves prophylaxis or leads to development of risk factors for subsequent subluxations has led to some controversy.…”

Characteristics of idiopathic atlanto-axial subluxation: a comparative radiographic study in patients with an idiopathic etiology and those with rheumatoid arthritis

“…RA, in particular, is a common cause for such instability, and some authors [5,6,10] have reported their recent clinical results after atlanto-axial arthrodesis. However, idiopathic AAS patients without RA, upper-cervical spine anomaly or any other disorder are rarely encountered.…”