Axially dynamic implants for stabilization of the cervical spine.

Abstract

Subsidence is a naturally occurring process that is observed during aging and after spine surgery. Rigid cervical spine instrumentation is excellent for stabilizing the spine. These devices, however, also retard subsidence after surgery. Thus, the implant carries much of the axial load, rather than sharing the axial load with the bone graft. This results in an increased incidence of construct failures, pseudoarthrosis, or both, which often occur late in the postoperative course. In contrast, dynamic implants allow normal (natural) subsidence to occur, while effectively stabilizing the spine by preventing translation, rotation, and angular deformation. Load sharing, which works with, instead of against, the normal biology of bone healing, occurs with axially dynamic implants, resulting in more robust and earlier fusions. Diminished incidences of construct failures have been reported with dynamic implants. Dynamic implants seem to be the system of choice for ventral cervical stabilization in selected patients.