Is the technique of posterior transarticular screw fixation suitable for rheumatoid atlanto-axial subluxation?

Abstract

The rheumatoid patient with atlanto-axial subluxation presents a major challenge to the spinal surgeon, owing to the poor wound healing and bone quality. Traditional wiring techniques are associated with a high complication and failure rate. Posterior transarticular screw fixation of the atlanto-axial joint offers a credible alternative and when combined with a Gallie construct offers immediate true 3-point stability. It is, however, a difficult and demanding technique which carries a risk of vertebral artery, cranial nerve and spinal cord damage. The question that arises therefore is "Do the improved stability rates afforded by this technique really justify the risks of arterial and neurological damage?" To date there have been no studies of this technique dealing solely with the rheumatoid patient, with most reports dealing with a heterogeneous patient population, mainly trauma-related cases. The purpose of this report is to analyse critically our results with particular reference to the complications that we have encountered and the technical reasons for their occurrence. We analysed the clinical and radiological data of 38 rheumatoid patients (six males: 32 females, mean age of 54 years) with atlanto-axial subluxation who underwent transarticular screw fixation. Our analysis centred on screw malposition and complications. Parametric and non parametric statistical analysis was performed. Significance was accepted at the 5% level ( p 0.05). Our analysis revealed that three vertebral arteries were damaged. Two of these were recognized at the time of surgery, with the remaining case only suspected following postoperative CT to assess screw positioning. Vertebral artery occlusion was subsequently confirmed by angiography. All three patients were asymptomatic from their arterial injury. There was only one neurological complication in this series, and this was caused by a high screw, which damaged the hypoglossal nerve with a temporary nerve palsy ensuing. Four screws broke, all were made of titanium, but more importantly, all were also associated with contralateral screw malposition. Stability was achieved in 95% of cases overall. The high stability rates afforded by this technique do appear to justify the inherent risks of this procedure. If unilateral screw fixation only is achieved, we would recommend a period of halo immobilization until osseous union occurs.