Stabilization of the Craniovertebral Junction with Clivus Plate Constructs: Biomechanical Comparison with Conventional Technique

Abstract

Ventral defect caused by resection of the lesions involving the upper cervical spine commonly has been reconstructed with a fabricated mesh cage. Recently, a clival screw and plate fitted to the osseous anatomy of the craniovertebral junction was developed for this pathologic status. To evaluate the stability a clivus plate system fixation (CPSF) for the craniovertebral junction and compare it with a conventional fashioned mesh cage fixation (FMCF). Seven human fresh cadaveric specimens (occiput [Oc], atlas [C1], axis [C2], third cervical vertebra [C3], fourth cervical vertebra [C4]) were tested with intact and destabilization-reconstruction conditions. FMCF and CPSF were applied randomly to the clivus to the C3 segment combined with posterior occipitocervical fixation applied from the occiput to C4 segment, respectively. Specimens were subjected to a pure moment of 1.5 Nm in flexion, extension, lateral bending, and axial rotation, respectively. The range of motion (ROM) and neutral zone (NZ) from the occiput to C3 were calculated and compared between two anterior fixations. Motions were reduced significantly in all directions following FMCF and CPSF fixations when compared with the intact. The CPSF resulted in smaller ROM in lateral bending (0.3°vs. 0.6°, P= 0.015), axial rotation (0.6° vs. 1.2°, P=0.023) and flexion (0.1° vs. 0.3°, P= 0.019), but similar ROM in extension (0.2° vs. 0.4°, P= 0.273) when compared with the FMCF. NZs with the CPSF were 0.1° in flexion-extension, 0.1° in lateral bending and 0.2° in axial rotation, respectively, and similar to NZs with the FMCF. The clivus plate system fixation is biomechanically superior to the conventional fashioned mesh cage fixation in flexion, lateral bending and axial rotation, but equavalent in extension.