Different states (accident or rheumatism as well as tumours) can lead to instability between the first and second cervical vertebrae (C1-C2), especially if the ligation which connects the two vertebrae together, loosens or breaks. In this process, the so-called dens (tooth of the second cervical vertebra) is shifted to the rear. This can lead to a significant narrowing of the spinal canal with pressure effect on the spinal cord, which in return can cause neurological deficits such as paralysis or sensory disturbances. Goal of surgery is the relief of the neural structures and the elimination of instability. So, first, the correct position between C1 and C2 will be restored and then the two vertebrae will be connected in this position, i.e. fixed. This can be done via a direct screwing of the joints, the so-called transarticular fixation or fixation with screws into the pedicles and Massae laterles that are connected to a rod.
Ultimately, in addition a fusion of bone is always required, which is placed between the two vertebrae and secured with wire. Thereby stability is ensured in the long run, even if the screws loosen or break; because the bone grows in. With a C1-C2 fixation is related to a loss of head mobility.
Overall, this form of instability is however rare and primarily affects patients with rheumatoid arthritis. Despite marked instability, the symptoms can be mild, such as head - and neck pain or tingling sensations in his hands. Since the symptoms are very nonspecific, the diagnosis may be delayed. Only by radiographs in function or computed tomography (CT) or magnetic resonance imaging (MRI) the disease can be detected.