Abstract A prosthetic nucleus (10) for a vertebral disc is made of a hydrogel material. The
hydrogel prosthetic nucleus has a shape generally conforming to the natural nucleus pulposus,
and it exhibits diminished lateral bulging under high compressive loads. The hydrogel has a
water content of from 30% to 90% and has a compressive strength of 4NM -2 or greater. When
the hydrogel material is dehydrated, it has a dimension of less than half ofthat of the hydrated
hydrogel nucleus. The prosthetic nucleus may be formed of two or more pieces of hydrogel
material (42, 44) which pieces, when combined, have a shape generally conforming to the
natural nucleus. The prosthetic nucleus may have a stiff posterior periphery (24) and/or a
thickened anterior wall (28).
A prosthetic nucleus (10) for implanting into a disc space after removal of a
degenerated or damaged nucleus of an intervertebral disc, said prosthetic nucleus
comprising: a biologically compatible hydrogel material having, when fully hydrated, a
size and shape generally conforming to a natural nucleus or to the shape of a cavity
created after removal of the degenerated or damaged nucleus; a water content in the
range of 30% to 90%; and a compressive strength of 4MN -2 or greater; and a
prosthetic nucleus periphery a part of which exhibits diminished lateral bulging in
comparison to other parts of the prosthetic nucleus periphery, characterised in that the nucleus periphery wall varies in height by at least
1 mm in the fully hydrated implant.
Claim 2
Dependent Claim
44 words
The prosthetic nucleus (10) as claimed in Claim 1 wherein the nucleus has an anterior
wall (28) and a posterior wall (30) and the anterior wall (28) is at least about 1 mm
thicker than the posterior wall (30) in the fully hydrated implant.
Claim 3
Dependent Claim
30 words
The prosthetic nucleus (10) as claimed in Claim 2 wherein the anterior wall (28) is
at least 2 mm thicker than the posterior wall (30) in the fully hydrated implant.
Claim 4
Dependent Claim
23 words
The prosthetic nucleus (10) as claimed in Claim 2 wherein the height of the nucleus
gradually increases from the posterior to anterior side.
Claim 5
Dependent Claim
61 words
The prosthetic nucleus (10) as claimed in Claim 2 formed from a first piece (42) and
a second piece (44) of hydrogel material having a combined shape generally
conforming to the natural nucleus, wherein at least part of the wall of the first piece
is at least 1 mm thicker than at least part of the wall of the second piece.