Fig. 5.

Biomechanical effect of C1-ring osteosynthesis on C0–2 alignment. Left schematic illustration of forces involved in the creation of a Jefferson burst fracture (JBF). Axial compressive forces (large dark arrows) on C0 result in a failure of the C0–C1–C2 ligamentous tension band through loss of height and fracture of the bony C1 ring, causing a lateral displacement (small dark arrows) of the C1-lateral masses from the anterior and posterior ring arches. Right reconstruction after a JBF involves imparting an axial tensile force (large gray arrows) to lift C0 into proper alignment to the C1–2 complex. Simultaneous compressive forces (small gray arrows) on the C1-lateral masses and occipital condyles allow for the recreation of the functional C0–C1–C2 ligamentous tension band and C0–C height