@article {15833,
	title = {Hydrogels for nucleus replacement {\textendash} facing a biomechanical challenge},
	journal = {Journal of the Mechanical Behavior of Biomedical Materials},
	volume = {14},
	year = {2012},
	month = {2012-10-02 00:00:00},
	pages = {67-77},
	abstract = {

Hydrogels are considered promising for disc regeneration strategies. However, it is currently unknown whether the destruction of the natural interface between nucleus and surrounding structures caused by nucleotomy and an inadequate annulus closure diminishes the mechanical competence of the disc. This\ in vitro\ study aimed to clarify these mechanisms and to evaluate whether hydrogels are able to restore the biomechanical behaviour of the disc.

Nucleus pressure in an ovine intervertebral disc was measured\ in vivo\ during day and night and adapted to anin vitro\ axial compressive diurnal (15min) and night (30min) load. Effects of different defects on disc height and nucleus pressure were subsequently measured\ in vitro\ using 30 ovine motion segments. Following cases were considered: intact; annulus incision repaired by suture and glue; annulus incision with removal and re-implantation of nucleus tissue; and two different hydrogels repaired by suture and glue.

The intradiscal pressure\ in vivo\ was 0.75\ MPa during day and 0.5\ MPa during night corresponding to an\ in vitro\ axial compressive force of 130 and 58\ N, respectively. The compression test showed that neither the implantation of hydrogels nor the re-implantation of the natural nucleus, assumed as being the ideal implant, was able to restore the mechanical functionality of an intact disc.

Results indicate the importance of the natural anchorage of the nucleus with its surrounding structures and the relevance of an appropriate annulus closure. Therefore, hydrogels that are able to mimic the mechanical behaviour of the native nucleus may fail in restoring the mechanical behaviour of the disc.

}, keywords = {Compression test, Disc regeneration, Hydrogels, in vitro, In vivo, intervertebral disc, nucleus replacement}, author = {Reitmaier, S. and Wolfram, U. and Ignatius, A. and Wilke, H. - J. and Gloria, A. and Mart{\'\i}n-Mart{\'\i}nez, J. M. and Silva-Correia, J. and Oliveira, J. M. and Reis, R. L. and Schmidt, H.} }

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