A prosthetic nucleus for a vertebral disc is made of a hydrogel material. The hydrogel prosthetic nucleus has a shape generally conforming to the natural nucleus pulposus. The hydrogel has a water content of at least 30% and has a compressive strength of 4MNm.sup.-2 or greater. When the hydrogel material...http://www.google.es/patents/US5047055?utm_source=gb-gplus-sharePatente US5047055 - Hydrogel intervertebral disc nucleus
