Fig. 4 a.

Under pure-moment, lateral-bending loading, the FHAs of some of the intact L4–5 segments were spread out in the transverse plane (specimen No. 276, light FHAs). In some others (specimen No. 676, light FHAs) as well as after implantation of the PDN-device, they were parallel to each other in an antero-posterior direction (specimen No. 276, dark FHAs; specimen No. 676, dark FHAs). b Range of motion (ROM) and neutral zone (NZ) in lateral bending were almost restored after implantation of the PDN device. Mean and range of 11 specimens after normalisation to the individual intact ROM