What effect does a fusion have on the rest of the cervical spine?
The effect that a fusion would have depends on what level of the spine is fused and how many levels are fused. Most of the nodding and turning of the head occur at the uppermost cervical levels, which are relatively rarely involved in cervical fusion operations. The most common fusions are performed in the middle of the cervical spine. By causing the bones to grow together at one or more levels, some of the stress of head motion will be transferred to adjacent cervical spinal levels. There is a suggestion that this may cause accelerated breakdown at the adjacent spinal levels, although this has not been proven. Once again, however, one should not have a cervical fusion unless it is considered absolutely necessary. At that point, the risk of degeneration at adjacent segment levels may be worth taking.
That is an excellent question. In a one level fusion, there is little impact on the spine. In a multilevel fusion, the major concern about performing a fusion is adjacent segment degeneration. The discs act as shock absorbers between the vertebras. When the spine is fused, the levels above or below the fusion may absorb the sheer force from every day motion, and thus wear out the discs. When the fusion is performed with the appropriate size bone graft, the balance of the spine is maintained and the adjacent segments are at less risk of degeneration.
