The Clinical Anatomic Study And Biomechanical Evaluation Of Anterior C_1～2 Transarticular Screw Fixation

Objective To provide anatomic data and determine the three-dimensional stability of C1～2 after instrumentation anterior C1～2 transarticular screw fixation for instability of C1～2 joint.Methods Direct measurements were taken from 100 pairs of dried human C1 and C2 vertebrae. The anterior C1～2 transarticular screw insertion point is at the junction of the lateral edge of the C2 vertebral body to 4 mm above the inferior edge of the C2 anterior arch. The medial and lateral lengths of screw paths for transarticular screw placement were measured from the entry point to the midline of the superior articular surface between the anterior and posterior margins of the C1 superior facet. The corresponding minimum and maximum angulations of the screw path relative to sagittal and coronal planes were determined. The maximum posterior angulation of the screw placement relative to the coronal plane also was determined. Eight human occipitocervical spine specimens, including the skull base, clivus and occipital condyles, occipital bone, as well as vertebrae down to an intact C3 were harvested fresh and stored frozen at —20° in double bags until they were mounted and tested. The specimens were tested in a totle of four configurations: intact, after an odontoid fracture, and after anterior or posterior C1～2 transarticular screw fixation. Intervertebral motion was measured with an optoelectronic measurement...