Material properties in unconfined compression of human nucleus pulposus, injectable hyaluronic acid-based hydrogels and tissue engineering scaffolds.
Surgical treatment for lower back pain related to degenerative disc disease commonly includes discectomy and spinal fusion. While surgical intervention may provide short-term pain relief, it results in altered biomechanics of the spine and may lead to further degenerative changes in adjacent segments. One non-fusion technique currently being investigated is nucleus pulposus (NP) support via either an injectable hydrogel or tissue engineered construct. A major challenge for either approach is to mimic the mechanical properties of native NP. Here we adopt an unconfined compression testing configuration to assess toe-region and linear-region modulus and Poisson's ratio, key functional parameters for NP replacement. Human NP, experimental biocompatible hydrogel formulations composed of hyaluronic acid (HA), PEG-g-chitosan, and gelatin, and conventional alginate and agarose gels were investigated as injectable NP replacements or tissue engineering scaffolds. Testing consisted of a stress-relaxation experiment of 5% strain increments followed by 5-min relaxation periods to a total of 25% strain. Human NP had an average linear-region modulus of 5.39 +/- 2.56 kPa and a Poisson's ratio of 0.62 +/- 0.15. The modulus and Poisson's ratio are important parameters for evaluating the design of implant materials and scaffolds. The synthetic HA-based hydrogels approximated NP well and may serve as suitable NP implant materials.
Department of Orthopaedic Surgery, University of Pennsylvania, 424 Stemmler Hall, Philadelphia, PA, 19104-6081, USA.
Jordan M
JM
Cloyd
Neil R
NR
Malhotra
Lihui
L
Weng
Weiliam
W
Chen
Robert L
RL
Mauck
Dawn M
DM
Elliott
D000328:Adult; D000368:Aged; D019245:Compressive Strength; D005260:Female; D006801:Humans; D006820:Hyaluronic Acid / Q000378:metabolism*; D020100:Hydrogels / Q000378:metabolism*; D007267:Injections; D007403:Intervertebral Disc / Q000166:cytology* / Q000502:physiology*; D008297:Male; D008422:Materials Testing / Q000379:methods*; D008875:Middle Aged; D023822:Tissue Engineering / Q000379:methods*; D054457:Tissue Scaffolds
D020100:Hydrogels; D006820:Hyaluronic Acid