Biomechanical and clinical aspects of spondylodesis of the lower cervical spine. Methods and implants

Abstract

The break with the demand for maximum rigidity of implant fixation of a traumatized unstable lower cervical spine is based on analysis and implementation of scientific and clinical data on the biomechanics of the native, the unstable and the implant-fixed spinal column. In view of these facts, recommendations for stabilization of the lower cervical spine can presently be formulated as follows: The surgical procedure is to bring about decompression, restoration of form and stability. The anterior approach should be the primary and preferred one. With regard to surgical and positioning technique, this access clearly involves less problems than the posterior approach; if required, unrestricted additional cord decompression can take place; implant fixation is technically simple: and the awareness of instability and type of implant permits functional therapy, also and above all for the paraplegic patient. For traumatic conditions, posterior methods are reserved for exceptional indications, and being single procedures, they require the anterior column to be intact and a multisegmental procedure. They are therefore less recommendable for traumata but rather suitable for degenerative, rheumatoid or tumorous instabilities. The cerclage wire technique depends on intact, osseous posterior elements, while after laminectomy only screwed implants can secure safe stability. This disadvantage of the posterior access for the proprioception of the cervical muscles and the subjective well-being of the patient are known and to be taken into account. Combined techniques are indicated for highly unstable or particularly complex injuries. On the cervicothoracic junction or in cases of Bechterew's disease, the decision is justifiably made in favor of the technique, which ca be performed as one-stage or two-stage operation. Whenever possible, selection of the implant should take into account the foreseeable developments in diagnostic procedures; and therefore, with a view to follow-up examinations required later and to modern imaging techniques, the implant chosen should be made of titanium.