ABSTRACT
Objective To evaluate the biomechanical stability of pectin/polyvinyl alcohol composite （CoPP）hydrogel and to assess the range of motion(ROM) and intradiscal pressure (IDP) changes at the above adjacent segment after the anterior implantation of CoPP hydrogel and cage. Method Six fresh cadaveric lumbar spine specimens（L3～L5）were biomechanically tested on the robotic testing machine. ROM at L3/4 and L4/5 and intradiscal pressure at L3/4 were measured. All measurements were made with initially intact and followed by both CoPP and cage implantations. Results At the implanted level (L4/5), the CoPP spine showed no significant change in the other five motion directions except left lateral bending motion compared with the intact spine (P>0.05), whereas the cage spine decreased significantly in all motion directions when compared with the intact spine or CoPP spine (P0.05), whereas the ROM of cage spine significantly increased in all motion directions compared with the intact spine (P0.05). While the IDP of cage spine significantly increased in flexion/extension and left/right lateral bending compared with the intact spine or CoPP spine (P0.05). Conclusions The implantation of CoPP prosthetic nucleus can preserve the motion function at the operated level and maintain the lumbar stability. Compared with the lumbar fusion, the nucleus replacement has no significant effect on the ROM and IDP at adjacent level, which may decrease or avoid the adjacent segment degeneration.
ABSTRACT
<p><b>OBJECTIVE</b>To evaluate the anti degenerative effect of pectin/polyvinyl alcohol composite (CoPP) hydrogel as artificial nucleus material in an animal model.</p><p><b>METHODS</b>Thirty-six New Zealand white rabbits were used to build animal models, the L₄₋₅ intervertebral discs were pierced with a Gauge#16 needle and polyvinyl alcohol (PVA) or CoPP implants were inserted into the holes. For comparative purposes, L₃₋₄ discs underwent sham treatment or control treatment in which the disc was pierced but no implant was inserted. All the discs were divided into four groups as follows: sham disc group, pierced disc group, PVA disc group and CoPP disc group. The discs were analyzed radiologically and histologically for degenerative changes at 1, 3 or 6 months after surgery.</p><p><b>RESULTS</b>None of the animals died from operative complications, such as paraplegia or infection before being killed. Macroscopically, none of the implants showed any signs of displacement at the time of harvest. The radiological analysis revealed that significantly less disc height loss was found with the PVA and CoPP replacement treatment than with the pierced treatment (P < 0.05). Changes in disc height after the replacement treatment were not significantly different from that after the sham treatment (P > 0.05). Histological degeneration of the replaced discs was delayed in comparison with that of the pierced discs (P < 0.05), but progressed with time, and PVA replacement showed faster disc degeneration than CoPP replacement.</p><p><b>CONCLUSIONS</b>Degeneration of the anulus fibrosus after the CoPP prosthetic nucleus replacement treatment is delayed by preserving disc height and occupying the space of the nucleus pulposus, and it has great potential clinical application value.</p>