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 segment...

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Bibliographic Details
Published in:	European spine journal 2007-11, Vol.16 (11), p.1892-1898
Main Authors:	Cloyd, Jordan M, Malhotra, Neil R, Weng, Lihui, Chen, Weiliam, Mauck, Robert L, Elliott, Dawn M
Format:	Article
Language:	eng
Subjects:	Adult Aged Compressive Strength Female Humans Hyaluronic Acid - metabolism Hydrogels - metabolism Injections Intervertebral Disc - cytology Intervertebral Disc - physiology Male Materials Testing - methods Middle Aged Original Tissue Engineering - methods Tissue Scaffolds
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Summary:	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.
ISSN:	0940-6719 1432-0932