Atlantoaxial arthrodesis using interlaminar clamps : an improved technique

The atlantoaxial articulation is a multiaxial joint with a freedom of motion that presents unique problems in achieving surgical stability. Several methods of atlantoaxial arthrodesis have been established with varying degrees of immediate and sustained stability and safety. This study describes a new, improved method of posterior atlantoaxial arthrodesis, using (Halifax) interlaminar clamps with interposed bone graft, which provides distinct benefits over existing techniques. This method achieved atlantoaxial union within 12 weeks in 80% of the study's patients (20/25). The clamp fixation was revised in two patients, with subsequent fusion. Three other patients required revision surgery for nonunion due to loosening of the clamp. This was usually caused by incomplete tightening of the screws, with subsequent loosening or dislocation of the device. Possible clamp loosening is a potential problem with the currently available system, and may be a result of the clamp design. Techniques to minimize this risk and suggestions for improvement in the device are discussed. Nonunion is more likely to develop in patients with rheumatoid arthritis. If nonunion occurs, the pseudarthrosis is generally between the posterior bone graft and the ring of C1.