Effect of an artificial prosthetic disk nucleus on the mobility and height of an L4/L5 disk segment after nucleotomy

This study investigated whether after a nucleotomy and implantation of a prosthetic disk nucleus (PDN) the original height and mobility of an L4/L5 disk can be restored. Compared to the intact state (100%), nucleotomy increased the median values of the normalized range of motion (ROM) in flexion/extension to 118%, lateral bending to 112%,and axial rotation to 121%. PDN implantation reduced ROM to 102%, 88%, and 90%. These differences were even more distinct when comparing the neutral zone (NZ) with 210%, 173%, and 107% after nucleotomy and 146%, 149%, and 44% after PDN implantation. With an axial preload of 200 N, disk height after nucleotomy was reduced by about 1.3 mm and could be restored with PDN implantation. PDN implantation can restore disk height and ROM after nucleotomy to normal values and reduce the strong NZ increase. Further biomechanical characterization of this therapy with PDN is necessary.