Spondylolysthesis
Spondylolythesis is an unstable movement of the spine that on x-ray shows a forward slippage of one vertebra on another. This is known as a “slipped” vertebra. There are multiple reasons for this condition, but it mainly is a result of either a stress fracture in patients less than 50, or degenerative instability, generally patient over 50. The spondylolysthesis is generally well tolerated until the nerves become pinched as the spine slides instead of pivoting.
The main complaint is usually back pain in any position, sitting or standing. There is a feeling of instability or looseness of the back, but if a good position is found, the muscles can support the back with minimal pain. The pain is episodic and catching with certain movements. When the nerves become involved, the pain is very intense as the instability slides and compresses the nerve with weight of the torso. The pain is focused on the back and buttock, but will commonly radiate down the leg, one or both.
Physical therapy and cortisone injections are helpful early in the process. Usually the instability progresses, as does the stenosis, over the course of years. When the pain is intolerable and not responsive to treatment, surgery is a good option with high success rates expected. Surgery needs to decompress the nerves with a laminectomy and because the spine is unstable, a fusion is usually considered, except for low grade instability or the elderly.