Degenerative changes in the spine (usually from aging) can cause bone spurs to form around the spinal joints. The joint spaces start to narrow. This condition is called spondylosis. Spondylosis with cervical myelopathy is a common problem causing chronic pain in older adults.
Surgery may be needed to stabilize this condition. Complications occur in about four per cent of the patients. An inpatient hospital survey in the U.S. over a 10-year period showed that adults older than 74 years of age were four times more likely to develop problems after cervical spine surgery. This was especially true for those who had a posterior fusion for spondylosis with cervical myelopathy.
In addition, the same group of patients were 19 times more likely to die during their hospital stay. So although unusual, your mother's situation is not rare.