MODIFICATION OF C1-C2 SCREW FIXATION (DU TOIT TECHNIQUE) FOR ATLOIDOAXOID ARTHRODESIS VIA THE LATERAL APPROACH

Abstract

Purpose: Several techniques have been proposed for C1-C2 fusion. The anterior transoral technique is the most direct approach but at the cost of major risk of infection. The posterior approach allows wiring (Gallie technique) or direct atloidoaxoid screw fixation (Magerl technique). The retrosternomastoid bilateral approach (Du Toit technique) allows direct screwing in the lateral masses. The rate of nonunion reported in the literature is high for wiring techniques. Biomechanical studies have demonstrated the mechanical superiority of trans-articular screwing which has been confirmed in clinical series. The purpose of the present study was to describe a modification of the Du Toit technique and describe results in a short series.

Material and methods: This modification of the Du Toit technique consists in an abrasion of the C1 lateral mass at its origin enabling the penetration of a Cloward curette to create a stable introduction point for the drill bit and thus avoid slippage forward as can occur with the conventional technique. The screw is directed towards C2, in a strict frontal plane. The obliquity depends on the room allowed by the mastoid. The drill bit should cross both corticals of the inferior facet of C1 and the superior facet of C2. The screws must cross in a coronal plane just under the odontoid. Fusion of the C1-C2 lateral masses is achieved by abrasion and grafting.

We have used the modified Du Toit technique for C1-C2 arthodesis in four patients with rheumatoid arthritis, fracture of the odontoid, an odontoid bone, and isolated degeneration. The procedure was a first intention treatment for the patient with primary degeneration, and a second intention procedure for the others who had developed nonunion after wiring.

Results: Mean hospitalisation was six day. Operative time was 2 h 10 min. Mean blood loss was 200 ml peroperatively and 120 ml postoperatively. None of the patients had developed nonunion or mechanical failure at a mean follow-up of 2.7 years (range 1 – 5 years). Operative complications included one case of venous bleeding which was treated with vascular clips and two cases were the lateral mass of C1 was weakened requiring cementing. There was one early postoperative neurological complication with hypoaesthesia of the hemitongue that regressed spontaneously. None of these complications produced sequelae.

Conclusion: The advantages of the modified technique for lateral screw fixation of C1-C2 is the improvement in the entry point for the drill bit allowing an optimal screw position and a stable drilling to achieve good mechanical fixation and certain union.