Fusion disease is a complication from spinal fusion surgery. Spinal instability from a variety of problems and conditions may need surgical treatment. The standard operation is a spinal fusion. The disc is removed along with some pieces of bone putting pressure on the spinal nerves.
The now empty disc space is filled with bone graft and a tiny cage filled with bone graft material. Metal screws or a metal plate and screws may be used to hold the spine stable until the bone fusion heals.
This operation can be done in one of two ways. The surgeon can make a large incision, cut through the muscles, and use retractors to pull the soft tissue out of the way. That is the traditional or standard method. A newer approach is called minially invasive surgery (MIS). With MIS, the surgeon makes a tiny incision and uses a microscope to see inside. Retraction is not needed.
It’s the cutting of the muscles called dissection and the use of retraction that can cause fusion disease. Damage to the muscles along the spine and to the nerves to those muscles can result in muscle atropy and weakness. Despite the fusion, the patient may develop an unstable spine from muscle weakness.
This condition can be temporary or permanent. It depends on how much nerve damage occurs. Nerves can heal but it takes time.