Putting the Screws to Upper Neck FusionEver wonder how it is you can nod your head, tilt your face to the sun, turn and look behind you, and hold the phone between your ear and shoulder? Half of your head's ability to turn and a good portion of your ability to bend and extend the neck come from the atlantoaxial (AA) joint. That's where the first vertebra (C1) meets the second vertebra (C2) at the base of the skull.
Anything that can affect the joints or ligaments in this area can seriously disrupt motion. Too much motion in this area is called atlantoaxial instability. (AAI). The most common causes of AAI come from:
AAI is treated with an operation to hold the bones together. The surgery is called internal fixation. Most often, fixation (also known as fusion) is done with wiring and bone grafts. A brace to hold the neck still during healing is used after the operation. The brace is called a halo-vest.
The halo-vest includes a titanium ring (the halo) that goes around the head. This portion of the brace is secured to the skull by metal screws (pins). Four metal bars attach the halo ring to a vest worn on the chest. This vest offers the weight to anchor the ring and immobilize the neck.
A second and newer way to fix the C1-C2 segment is called transarticular screw fixation. As the name implies, a long screw is used through the bone. With this method, bracing isn't needed. This study compares the wiring method with the screw fixation for AAI.
This study compared the two techniques. The fusion results between the two groups were very different. The group with cervical wiring and a halo-vest had 11 cases of poor or no fusion. There were six reoperations. The group with screw fixation (without bracing) had only two cases of stable nonunion. There were fewer complications with the screw fixation group.
The authors conclude that the transarticular screw fixation method of C1-C2 fusion is more rigid. This method may be a better way to fuse the neck. There's a higher fusion success rate with fewer problems after the operation, and no bracing is needed after surgery.
Thomas M. Reilly, et al. Atlantoaxial Stabilization: Clinical Comparison of Posterior Cervical Wiring Technique with Transarticular Screw Fixation. In Journal of Spinal Disorders & Treatment. June 2003. Vol. 16. No. 3. Pp. 248-253.
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