Abstract and Introduction
The past several decades have been the setting for a remarkable evolution of spinal instrumentation technology. The advancements that have been made have allowed previously complex disorders of the cervical spine, the atlantoaxial articulation, and the occipitocervical junction to be managed more effectively with direct methods of internal fixation and arthrodesis. This has resulted in improvements in patient outcomes and fusion success rates. The improved strength of instrumentation constructs allows minimal, if any, external bracing, obviating the need for a halo orthosis in many cases. In this paper the authors review key events that have occurred in neuroimaging, biomechanical testing, and the development of fusion and instrumentation constructs.
The cervical spine presents a challenge to the spinal surgeon because of its limited biomechanical strength, the paucity of some osseous structural elements, the neural and vascular structures contained within the spine, and the frequent variation in anatomy among patients. Any instrumentation construct must be strong enough to resist force in multiple axes of motion, yet delicate enough to integrate into the cervical spinal elements. In addition, a complex spinal transition zone occurs at the occipitocervical junction. Successful attainment of arthrodesis in this transition zone has been a challenge for many years.
Numerous pathological conditions can destabilize the occipitocervical junction, atlantoaxial articulation, and subaxial cervical spine. Common mechanisms of instability include but are by no means limited to trauma, rheumatoid arthritis, inflammatory or infectious lesions, neoplasms, and congenital deformity. Common to all these processes is the resulting neural compression and/or craniospinal or spinal instability. The rapid identification of the pathological process and the subsequent correction of subluxation or malalignment, decompression, and, ultimately, stabilization must be undertaken. Every patient presents a unique diagnostic and therapeutic challenge.
Although in this manuscript we will focus on posterior approaches for arthrodesis and instrumentation of the craniocervical junction, atlantoaxial articulation, and subaxial cervical spine, it is important to realize that posterior approaches are not always the correct solution. Many cervical spinal lesions, as well as the majority of occipitocervical, lesions, are anterior and anterolateral in orientation. Previous attempts at direct posterior approaches for these lesions have been abandoned in favor of anterior and anterolateral approaches that have proved to be more direct and effective, and associated with lower risks of morbidity. Posterior surgical decompression remains a vital component in the management of these anteriorly or anterolaterally situated lesions in some select cases. Also, it is not necessary in every case to perform an arthrodesis of the occipitocervical articulation or the cervical spine. Careful preoperative decision making requires assessments of the functional stability of the spine, anterior instrumentation and fusion options, and the need for posterior supplementation. In cases of posteriorly situated lesions in which posterior surgical decompressive approaches are appropriate, an additional assessment of the stability of the spine must be made. In cases in which the pathological process or the surgical approach to correct this process results in the instability of the spine, posterior cervical arthrodesis is appropriate. In some rare cases a combined anteriorposterior supplementation is required.
Much of the evolution of posterior spinal instrumentation technology is attributable to advances in neuroimaging; an improved understanding of the biomechanical and anatomical relationships between the structures involved; and an enhanced materials science technology from which smaller, lower profile (yet stronger), instrumentation constructs, which are suitable for the unique demands of the cervical spinal region, have been produced. In addition, many constructs have now been designed to be compatible with MR imaging, a key imaging modality used in the evaluation of additional progression of many of the lesions being treated.
Neurosurg Focus. 2004;16(1) © 2004 American Association of Neurological Surgeons
Cite this: The Evolution of Posterior Cervical and Occipitocervical Fusion and Instrumentation - Medscape - Jan 01, 2004.