The cervical spine and its relation to anterior plate-screw fixation: a quantitative study.

Multilevel discectomy and inter-vertebral body fusion combined with anterior plate-screw fixation is the common procedure in cervical spine surgery. The correct placement of the screws is an important factor for the outcome of these operations. Yet no systematic approach has been undertaken to optimize the geometry of the fixation-plates regarding the position of the screw-perforations. In this study MRI scans of 50 consecutive patients were analyzed regarding the height of each segment (C3-C7), the anterior-posterior diameter of the vertebral body and the distance between the vertebral arteries. Based on this data we developed "Standard Spine Models". Using these models we designed two plates each for single and two-level surgery, and three plates each for three- and four-level surgery. These ten plates do fit the cervical spines of all 50 patients examined in this study. With these plates the screw-perforations could be positioned efficiently over the bodies of the concerned vertebrae. This should facilitate the selection of a plate and the positioning of the screws. Thus the surgeons might save time and the screws might be positioned more exactly and entirely in the vertebral bodies, ensuring a secure fixation.