Role of transarticular screw fixation in tuberculous atlanto-axial instability.

Prospective study of 27 consecutive cases of tuberculous atlanto-axial instability operated between 1998 and 2003. Early surgical stabilization of tuberculous atlanto-axial instability has gained popularity. This is largely due to success of chemotherapy in rapid control of infection. Although selective atlanto-axial fusion techniques are advocated in other indications, their role in tuberculosis remains confined to atlanto-axial wiring techniques that are mechanically unsound. The role of three-point rigid fixation using trans-articular screws (TAS) remains unclear. The objectives of this study are: (1) To define the role of trans-articular screws in tuberculous atlanto-axial instability based on radiological criteria. (2) To attempt to separate patients that can be treated by selective atlanto-axial fixation as against the standard occipito-cervical fusion (OCF). (3) Compare the clinical and radiological outcome parameters between the two groups. Twenty-seven consecutive patients of tuberculous atlanto-axial instability were operated between 1998 and 2003. The pattern of articular surface destruction and the reducibility of the atlanto-axial complex were assessed on plain radiographs and MRI. The reducibility of the C1-C2 joint was graded as reducible, partially reducible and irreducible. Pattern of the C1-C2 articular mass destruction was grouped as minimal, moderate and severe. The patients were divided into two surgical groups based on radiological findings and were treated with TAS (n=11) and OCF (n=16) fusion. The three-point fixation provided by the TAS allowed early brace free mobilization by 3 months with fusion rate of 100%. Fusion occurred in 83.16% in the OCF group. Implant failure occurred in two patients who underwent OCF. The patient satisfaction rate in the TAS group and the OCF group was 90.90 and 62.50%, respectively. Results in 27 consecutive patients demonstrate improved patient fusion and satisfaction rates in the TAS group. Judicious selection of patients for TAS fixation is possible with relatively few complications in tuberculosis of the atlanto-axial complex. This, however, requires a thorough understanding of the MRI pattern of involvement of the atlanto-axial complex that is difficult in non-endemic areas.