Segmentary L5-S1 kyphosis of after the implantation of a stand-alone ASPEN interspinous device with overload of the anterior part of the intervertebral disc. (a) Sagittal balance of lumbar spine before the implantation of the ASPEN device: lumbar lordosis 48°, L4-S1 lordosis 33°, and L5-S1 lordosis 17°. (b) Sagittal balance of lumbar spine after 4 years from the ASPEN device implantation: lumbar lordosis 35°, L4-S1 lordosis 19°, and L5-S1 lordosis 8°. (c) MRI scan after 4 years from the Aspen implantation that shows anterior disc endplate degeneration (Modic II).
