Current strategies for the restoration of adequate lordosis during lumbar fusion

Figure 10 Impact of rod-screw connection on lordosis restoration: monoaxial vs polyaxial screws. With mono-axial screws, the connection between the screw and the rod is perpendicular, permitting therefore to position the spine approximately in a similar position compared to the rod. On the contrary, using poly-axial screws, the connection between the screw and the rod is angulated with the spine less lordotic compared to the rod. In the figure, although the contouring of the rod is similar for the two spines, the spine on the right, instrumented with poly-axial screws, is significantly less lordotic.