| 摘要 |
PROBLEM TO BE SOLVED: To balance the static water pressure against the outer load easily by having at least one hydrophilic xerogel rod which absorbs water from an aqua-composition when it is bound by the disc annulus thereby to expand and fill up the cavity. SOLUTION: A hydrogel prosthetic nucleus 10 implanted in the disc 12 of a vertebra 14 is surrounded by a natural annulus 16. The equilibrium water contents of the hydrogel are set within the range of from about 30 to about 90%. The xerogel contents are 10 to 70% of hydrogel contents with such equilibrium water contents. The xerogel rod is so formed as to have a diameter of from about 2 to about 10 mm. Such hydrogel preferably contains polyvinyl alcohol(PVA) gel, made by crystallizing a PVA solution under minus 10 degrees centigrade. When the xerogel rod absorbs water, the hydrogel expands and fills up the intervertebral foramina cavity.
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