Pre-operative irreducible C1-C2 dislocations: intra-operative reduction and posterior fixation. The "always posterior strategy".

Background: According to Menezes' algorithm, pre-operative dynamic neuroradiological investigation in C1-C2 dislocations (C1C2D) instability is strongly advocated in order to exclude those patients not eligible for posterior fixation and fusion without previous anterior trans-oral decompression. Anterior irreducible compression due to C1C2D instability, it is said, needs trans-oral anterior decompression. We reviewed our experience in order to refute such a paradigm.

Methods: The study involves 23 patients who were operated on for cranio-vertebral junction (CVJ) instability; all of them had C1C2D of varying degree on x-ray, computerised tomography (CT) and magnetic resonance (MR) imaging of the CVJ. Pre-operatively, irreducible C1C2D was demonstrated only in 3 patients, (2 with Down's Syndrome, one of them was harbouring os odontoideum, 1 Rheumatoid Arthritis), i.e. 13.04%; the remaining 19 (86.9%) had reducible C1-C2 dislocation. After an unsuccessful traction test conducted in the pre-operative phase under sedation, it was possible to completely reduce the C1C2D (with a combination of axial traction with light extension of the neck on the chest and a light flexion of the head on the neck by using a Mayfield head holder) and proceed to posterior fixation in all the patients under general anaesthesia using a precise "timing sequences fixation technique". Wiring (C0 and C3 were fixed first being stretched up to approximately 10 lbs, then C2 in order to pull up this vertebra last by forcing approximately 8 lbs) or screw fixation methods were used to achieve fusion along with post-operative external orthosis and neuroradiological assessment of the C1C2D. The instrumentation produced a lever and pulley effect which assisted reduction of the dislocation.

Findings: At follow up (range 34-55 months-mean 45.33 months) the clinical picture was improved or stable in all patients.

Conclusions: Pre-operative irreducibility of the C1C2D should not be an absolute indication for trans-oral decompression. An attempt to reduce the dislocation under general anaesthesia and during posterior fixation should be attempted in Down's syndrome, os odontoideum and rheumatoid arthritis.