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New Joint Fusion System for Upper Neck Problems

The top two bones of the neck fit together like a horseshoe around a spike. The upper bone is in the shape of a ring. It fits around a cone-shaped projection in the second vertebrae, called the dens.

The skull rests on top of the spine with two contact points. The connection between the head and the neck is called the occipitocervical junction. Most of the strength and stability of the occipitocervical junction come from the interlocking of the cervical bone around the dens. A network of ligaments gives added support.

Damage or injury to the dens or surrounding ligaments can cause serious problems. When the junction becomes unstable from disease or injury, it can cause paralysis, disabling pain, and even death. Surgical fusion to relieve pain and provide support is often needed. There are many ways to fuse this area. An operation is done to insert a plate, screws, rods, cables, wires, or a bone graft.

Researchers are looking for a better way to get rigid fixation. Doctors want something that can be used anywhere along the cervical spine. Scientists from the Biomechanics Laboratory at the Mayo Clinic in Rochester, Minnesota, report several studies in this area. The most recent one looks at a new rod and screw system.

The new rod system was compared to two standard methods of securing the occipitocervical area. The study was done using 12 cadavers (bodies preserved after death). Total range of motion and amount of stiffness were measured for each vertebral level. Six different loading conditions were used.

The authors report that fusion of in this part of the neck is a challenge. The best way to do fusion depends on the type of problem and cause of instability. The quality of the patient's bone is also a factor. They conclude that the new rod-based system is equal to or better than the plate-and-screw or rod-and-cable systems already in use.

References: Bradford L. Currier, MD, et al. Biomechanical Evaluation of New Posterior Occipitocervical Instrumentation System. In Clinical Orthopaedics and Related Research. June 2003. Vol. 411. Pp. 103-115.

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