Cervical Instability
Spinal stability can be defined as maintaining normal range of motion without pain or neurological dysfunction in the joints of the spine. In the cervical spine, these joints are unique in the upper cervical spine (craniocervical junction), and even the “sub-axial” cervical spine (below C2, a.k.a. the “axis”) disks and facets are different from those of the thoracic and lumbar spine.
At the cranio-cervical junction, the biodynamics lead to more movement than the sub-axial cervical spine, and have very different spinal elements. In the sub-axial cervical spine, although there are disks and facet joints like in the lumbar spine, these have very different angles and shapes, leading to the different types of movement. Each level has to move normally for people to not be patients…
Loss of integrity of the spinal elements (either mild, moderate, or severe) can lead to symptoms (problems the patients notice). Instability in the craniocervical junction (Cranio-Cervical Instability, or CCI) can lead to slippage of bones compressing the spinal cord or even the brain stem, or compression of nerves, arteries, veins, (or all of the above!), leading to weakness, brain pressure changes, cranial nerve problems including vision and hearing, autonomic dysfunction, swallowing problems, or even strokes.
Sometimes instability leads to damage to the disk, either as a disk herniation (the contents leaking out of a defect in the “annulus fibrosis”) into the space where the spinal cord or nerves can be compressed by the piece that has migrated out, or just collapse and a shortening that leads to the normally tensioned ligaments now relaxed and bulging into the spinal nerves and spinal cord, causing foraminal or central spinal stenosis -> and symptoms from that. In addition, instability can lead to deformity of the spine, either where the spine is tilted away from a painful joint, or where the spine has collapsed, rotated, or tilted in a way that puts abnormal strain on nerves, muscles, or the head, leading to pain or weakness or balance problems.
When the symptoms of the instability are from stenosis include nerve pain (radiating down the arm, perhaps only into the shoulder, or in other cases all the way into the hand) or spinal cord dysfunction (balance, bowel/bladder problems, weakness), then removing the point of compression is the treatment of choice. This can be a diskectomy, foraminotomy, laminectomy, or laminoplasty.
When the symptoms of the instability are from a bone or joint derangement (more pain in the upper, middle, lower neck or even into the thoracic region between the shoulder blades), then replacing the unstable elements like the disk or facet joints is required to make this better. When the disk is the primary problem but the facets are reasonably intact and move normally, an artificial disk can be one treatment option. When instability exceeds certain parameters, fusion may be preferable.
In some cases, both a decompression and a fusion is necessary. When fusion is performed in the cervical spine, more often than not additional hardware is needed to ensure the success of the fusion.