Design, synthesis, imaging, and biomechanics of a softness-gradient hydrogel nucleus pulposus prosthesis in a canine lumbar spine model.
A hydrogel nucleus pulposus prosthesis (NPP) was designed to swell in situ, have intrinsic radiopacity, and restore intervertebral disc height and biomechanical functionality. These features were examined using an ex vivo canine lumbar model. Nine NPPs were implanted in five spines and their visibility was assessed on radiography, computed tomography (CT), and magnetic resonance imaging (MRI). The NPPs were visible on all imaging modalities and 8/9 NPPs stayed intact and in situ. Six other NPPs were tested biomechanically in six canine lumbar spines. Removal of the nucleus pulposus (nuclectomy) caused significant changes in biomechanical parameters. After implantation and swelling of the NPP, values were not significantly different from the native state for range of motion (ROM) of flexion-extension (FE) and lateral bending (LB), the neutral zone (NZ) of all motion directions, and the NZ stiffness (NZS) of FE. Biomechanical restoration by the NPP compared with the nuclectomized state was significant for the ROM of FE and axial rotation, the NZ of FE and LB, and the NZS of FE and LB. Disc height was significantly restored and 6/6 NPPs stayed intact and in situ. In conclusion, the NPPs swell in situ, have intrinsic radiopacity and restored disc height and aforementioned biomechanical properties.
Department of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands.
Hendrik-Jan C
HJ
Kranenburg
Björn P
BP
Meij
David
D
Onis
Albert J
AJ
van der Veen
Ketie
K
Saralidze
Luc A
LA
Smolders
Julie G
JG
Huizinga
Menno L W
ML
Knetsch
Peter R
PR
Luijten
Fredy
F
Visser
George
G
Voorhout
Wouter J A
WJ
Dhert
Herman A W
HA
Hazewinkel
Leo H
LH
Koole
D000818:Animals; D004285:Dogs; D020100:Hydrogels; D020007:Implants, Experimental; D007403:Intervertebral Disc; D008279:Magnetic Resonance Imaging; D008422:Materials Testing; D019919:Prosthesis Implantation; D014057:Tomography, X-Ray Computed / Q000379:methods
D020100:Hydrogels