Summary:Atlantoaxial fusion may be indicated in cases of painful osteoarthritis of the atlantoaxial joints or in cases of acute and chronic atlantoaxial instability due to developmental abnormalities, trauma, infection, tumor, or aseptic inflammatory processes. The most widely used techniques are the Gallie or Brooks techniques. They rely on the integrity of the posterior arch of the atlas and often require postoperative immobilization in a Minerva cast or halo jacket. With these techniques, intraoperative reduction is sometimes lost during the healing period. This article presents a stable technique for posterior atlantoaxial fixation and fusion using transarticular screw fixation; it is based on our experience in 76 cases. In contrast to other posterior techniques of C1-C2 fusion (e.g., Gallie or Brooks), transarticular screw fixation allows stable fixation of Cl and C2 in the reduced position even in cases of absence of the posterior arch of the atlas. Minimal postoperative immobilization is required, even in the presence of gross instability or pronounced osteoporosis, as in cases of rheumatoid arthritis. In cases of cranial assimilation of the atlas, this technique may be combined with occipitocervical fusion together with posterior decompression of the occiput and C1, if necessary. The patients are mobilized the first or second day after surgery with a Philadelphia- type collar for 6-12 weeks. The technique is contraindicated in cases of collapse of C2 due to massive rheumatoid destruction of the lateral masses.