I went through a special pre-operative program at the hospital for people considering a neck fusion. They spent a lot of time talking about adjacent segment disease or ASD as they called it. I understand what this is -- but how often does it really happen?
When conservative care does not relieve the pain and other symptoms caused by degenerative neck disease known as cervical spondylosis, then spinal fusion is considered. Nearly 60 years ago, in the 1950s, the first anterior cervical diskectomy and fusion (ACDF) was done. This has now become the standard of care for symptomatic cervical spondylosis.
The surgeon removes the diseased or damaged disc and any bone spurs that might be causing problems. This part of the procedure is called decompression. Then the spine is surgically stabilized. This is the fusion part of the surgery. A metal plate is attached to the front (anterior) side of the spine. Bone graft material is used to help speed up the stabilization process.
Any surgery comes with its own set of risks and benefits. Adjacent segment disease (ASD) is one of the known problems that can develop after spinal fusion. ASD refers to breakdown of the vertebrae next to the fusion. According to current studies, the increased stress and strain from a fusion (no movement at the fused level) results in adjacent segment disease in approximately three per cent of patients each year after the procedure.
Based on collected data from studies over the years, there is an expectation that about 25 per cent (one in four) patients will have some adjacent segment disease within the first 10 years after their fusion procedure. These figures come from studies with follow-up X-rays, which is how adjacent segment disease is observed.
Not all patients with visible adjacent segment disease (ASD) seen on X-rays has any symptoms from this degenerative process. In fact, many patients with ASD still report decreased neck pain and improved neck motion as a result. The hope is that the number of patients who experience adjacent segment disease will decline in the future as surgical techniques continue to improve and advance.