[mmglobal]

Calla, there are many different types of spinal instability, but they are referring to the improper alignment of the vertebral bodies, or a 'slip'. Looking at the imaging, you'd see that the bones are not stacked up properly.

It may be a static situation where a slip has occurred, but it does not change much. It may be dynamic, where your movement can generate inappropriate motion that can cause substantial pain or neurological problems. Often, instability does not show up on static films like MRI, CT, etc... They do 'flexion - extension' xrays that may show that the vertebral alignment changes when you flex forward or extend backwards. Potentially, weighted or dynamic MRI may also show instability.

As our discs collapse, you can think if it like a tire laying on it's side. It will get wobbly as the tire loses pressure. This is degenerative instability and is not a contra-indication to ADR. Implanting ADR will restore the disc height, 're-tensioning' the system. Other types of instability if they are too advanced will be a contra-indication to ADR because the structures that are required to keep your system stable (and are compromised) are also required to keep the system stable with the ADR in place.

Mark