What is adjacent level instability?
Terminal degeneration or connection instability is a phenomenon that describes the changes in one floor above or below the stiffened region. If a section of spine is fused, i.e. reinforced or stabilized, then the force on the adjacent section above and in particular the local disc is higher (the stiffened segment acts as a lever). This applies to both the cervical and the lumbar spine, where most stability operations are carried out.
Often, a stabilization operation is inevitable because a spinal instability is present with appropriate deformations, such as spondylolisthesis (olisthesis) or lateral bending (scoliosis). It is, however, to carry out these stability operations as gently as possible in order not to jeopardize the neighboring segments - i.e. minimize muscle dissection - to implant the screws in a way that the neighboring joints are not weakened and to obtain the spinous as an attachment for the muscles. If no significant repositioning is needed, a gentle transmuscular access can also be used.
If a neighboring segment weakened even before an operation, then the pressure of that segment will be reduced by the implantation of an interspinous spreader part. A so-called "soft" transition will be created. Other dynamic methods to relieve the neighboring segment can be applied (e.g. cosmic system, or DSS).
The best way to protect neighboring segments is of course to possibly avoid a stabilization operation and to maintain flexibility. This can when indicated, take place through the implantation of artificial discs and dynamic fixators. However, the experience with these systems are still limited so there is no absolute certainty whether this deterioration process in neighboring segments can be permanently prevented, especially in the presence of certain stress factors. In addition, disc prosthesis may be secondary i.e. ossify at a later date and thereby reinforce it. To reduce the risk of so-called heterotopic ossification, certain implant techniques are observed, often depending also on the experience of the operator.
To effectively reduce the risk of degeneration connection or connection instability after spinal surgery, concomitant therapy, physiotherapy, rehabilitation, sports rehabilitation and participation in various prophylactic back programs is required.
