Fig. 5.

Anterior surface strains of a representative simulation at maximum flexion. Areas of zero strain with the indistinct mesh were partitioned as the rigid bodies of L3 and L4, and thus should not accrue strain. The largest tensile and compressive strains were ZZ and YY, respectively, and occurred because of articular facet motion and the need to conserve volume. Tensile in-plane shear (XY) strains are pronounced and also occur from the prescribed deformation. For reference, the deformation applied to L3 is upward displacement, displacement toward the reader, and rotation toward the reader.