I went with Mother to her surgery appointment this morning. The surgeon said her neck was unstable and she has myelopathy. That's why they would have to do a fusion. Just exactly what does unstable mean? Is she in any danger with this problem? We just thought she had some neck arthritis and that's why her neck hurts so much.

Cervical spine instability usually means that one vertebral body slides too far forward over the vertebra below it. The degree of instability depends on how far the bone moves. This movement can be measured in actual distance (usually in metric units of millimeters). Or it can be expressed as a percentage based on its location over the vertebra below it. For example, a spinal segment that has slipped forward 25 per cent over the vertebra below it is a Grade I instability.

Grade II describes a vertebral bone that has moved forward over the bone below it by 50 per cent. Grade III is a 75 per cent instability. Grade IV is complete instability and very rare with paralysis and/or death as the outcome.

With all of these instabilities, the spinal cord is involved. As the vertebral bone moves forward, a traction pull is placed on the spinal cord. Patients experience painful symptoms accompanied by neurologic signs and symptoms such as numbness, tingling, weakness, loss of reflexes, and/or bowel and bladder problems.

The problem your mother has been diagnosed with is called cervical myelopathy. It is a degenerative condition that occurs with aging. Adults affected most often are 50 years old and older. The term myelopathy refers to any problem that affects the spinal cord. Cervical tells us the area affected is the cervical spine (neck region).

Fusion is needed to stabilize the bones -- that is, put them in as good alignment as possible and hold them there. Bone graft and instrumentation (metal plates, screws, or rods) are used to hold the spine stable. Without this stabilizing procedure, continued pull and pressure on the spinal cord can cause loss of function and severe disability.