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Is Your Head Screwed On Straight?

There's an interesting expression in the English language that goes something like this, I hope he has his head screwed on straight." The hope is that the person in question is using sound judgment in making decisions. In the world of orthopedic surgery, having your head screwed on straight can have a completely different meaning.

In this article, surgeons from the University of Washington Medical Center (Seattle, Washington) review modern posterior fixation for patients with an unstable occipito-cervical spine. That's where the skull meets the upper cervical spine (neck).

Instability severe enough to require surgical fixation occurs as a result of trauma, congenital malformations, or bony destruction from diseases such as cancer, arthritis, and infections. The upper cervical bones are collapsing from underneath the skull. Without support of some kind, the risk of pressure on the spinal cord is too great to leave the problem untreated.

Modern rod-and-screw fixation techniques have replaced the earlier (internal) wire fixation and (external) casts, collars, and halo vests. They are literally using metal plates, screws of various types, and rods to hold the base of the skull attached to the back of the cervical vertebrae.

Preshaped rods and contoured plates have increased the technical difficulty of the surgery. But these devices can be angled specifically to meet each patients needs. And the improvements in design have reduced problems with the plates pulling out or screws backing out.

Different types of locking screws are used and placed in different positions or parts of the spinal bones. The surgeon is literally screwing the head on straight and stable. Specific motions (side bending or rotating the head) can be prevented according to the patient's pattern of instability.

Such stabilization devices are needed when there has been significant disruption of the ligamentous structures, vertebral bodies, and spinal joints. All of these parts support the spine and hold the head in place on top of the spine.

The surgeons who wrote this article provide in-depth advice to other surgeons regarding preoperative planning, patient positioning during surgery, collaboration with the anesthesiologist, and surgical technique.

For example, MRIs are studied to make sure the surgeon knows exactly where the major blood vessels and nerves are located (and to avoid cutting into them). Bone thickness of the skull as well as the vertebrae are taken into consideration in choosing the right type of fixation and finding the best place to secure it (i.e., screw it in).

They include discussion of the various types of fixation devices including transarticular screws, C1 lateral mass screws, C2 pedicle screws, C2 pars screws, C2 translaminar screws, and bone grafting. Each of these methods of fixation has its own indications, benefits, problems, and limitations.

Careful surgical technique requires a very detailed knowledge of skull and cervical vertebrae anatomy. The surgeon tries to avoid blood loss, prevent blood clots, and minimize damage to the soft tissues. Each surgical step is performed slowly and deliberately with checking and double-checking holes and screws before making the final placement.

The authors conclude that with careful planning, surgeons can anticipate what is needed before attempting an occipito-cervical fusion with fixation devices and bone graft. One-hundred per cent (100%) accuracy in placement of the plates and screws can be achieved. Solid fusion is the final goal with patient safety a high priority throughout the procedure.

References: Richard J. Bransford, MD, et al. Posterior Fixation of the Upper Cervical Spine: Contemporary Techniques. In Journal of the American Academy of Orthopaedic Surgeons. February 2011. Vol. 19. No.1. Pp. 49-58.

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