Hydrogel balloon prosthesis for nucleus pulposus
View Patent ↗A prosthesis for replacing or supplementing a nucleus pulposus of an intervertebral disk is an expandable container having flexible walls, the container being adapted to be inserted into a central cavity of an intervertebral disk through a narrow cannula, and the flexible walls are made from a biocompatible hydrogel. A preferred hydrogel is a cryogel formed from an aqueous solution of poly(vinyl alcohol) and poly(vinyl pyrrolidone). The prosthesis may be prepared by dip-coating a mandrel with an aqueous solution of a hydrogel-forming polymer or mixture of such polymers, gelling the coated solution by chilling, and subjecting the gelled coating to a series of repeated freeze-thaw treatments. In use, the prosthesis is inserted into a central cavity of an intervertebral disk and filled with biocompatible material, e.g., a biocompatible liquid, a biocompatible polymer, and a biocompatible hydrogel, particularly a thermogelling hydrogel.
1. A prosthesis for replacing or supplementing a nucleus pulposus of an intervertebral disk, comprising a pre-formed expandable balloon having flexible walls defining an inner cavity, the flexible walls having a thickness from about 0.02 mm to about 1.00 mm and a filling tube passing through the flexible walls and in communication with the inner cavity so that the prosthesis is fillable, said pre-formed balloon being adapted to be inserted into the intervertebral disk through a cannula, wherein said flexible walls are made from a material comprising a cryogel formed from subjecting an aqueous solution comprising poly (vinyl alcohol) to repeated freeze-thaw cycles, said expandable pre-formed balloon being filled through the filling tube with a biocompatible material selected from the group consisting of a biocompatible liquid, a biocompatible polymer, and a biocompatible hydrogel in an expanded configuration, and the prosthesis having a tensile modulus of about 0.02 MPa to about 0.8 MPa at 30% strain.
2. The prosthesis of claim 1 , wherein said cryogel is formed from an aqueous solution further comprising poly (vinyl pyrrolidone).
3. The prosthesis of claim 1 , having a shape in the expanded configuration generally conforming to the shape of a natural nucleus pulposus.
4. The prosthesis of claim 1 , wherein said biocompatible hydrogel is a thermogelling hydrogel.
5. The prosthesis of claim 4 , wherein said thermogelling hydrogel is prepared from a mixture of a first aqueous solution comprising poly (N-isopropylacrylamide) and a second aqueous solution comprising poly (vinyl alcohol).
6. The prosthesis of claim 4 , wherein said thermogelling hydrogel is prepared from a mixture of a first aqueous solution comprising poly (N-isopropylacrylamide) and a second aqueous solution comprising poly (ethylene glycol).
7. The prosthesis of claim 4 , wherein said thermogelling hydrogel is prepared from an aqueous solution comprising a poly (N-isopropylacrylamide)-grafted poly (ethylene glycol) polymer.
8. The prosthesis of claim 4 , wherein said thermogelling hydrogel is prepared from an aqueous solution comprising a poly (ethylene glycol)-poly (N-isopropylacrylamide)-poly (ethylene glycol) triblock polymer.
9. The prosthesis of claim 4 , wherein said thermogelling hydrogel is prepared from a mixture of a first aqueous solution comprising poly (vinyl alcohol) and a second aqueous solution comprising poly (ethylene glycol).
10. A method of replacing or supplementing a nucleus pulposus of an intervertebral disk, comprising the steps of:
(i) providing a pre-formed flexible-walled balloon having an inner cavity, flexible walls defining the inner cavity, the flexbile walls having a thickness from about 0.02 mm to about 1.00 mm and a filling tube passing through the flexible walls and in communication with the inner cavity so that the prosthesis is fillable, the flexible walls made from a cryogel formed from subjecting an aqueous solution comprising poly (vinyl alcohol) to repeated freeze-thaw cycles,
(ii) inserting the pre-formed flexible-walled balloon into the intervertebral disk by a minimally invasive surgical procedure in a collapsed configuration, and
(iii) introducing into said inner cavity through said filling tube of said pre-formed flexible-walled balloon a biocompatible material selected from the group consisting of a biocompatible liquid, a biocompatible polymer, and a biocompatible hydrogel for expanding said pre-formed balloon into an expanded configuration to replace or supplement the nucleus pulposus, the filled balloon in the expanded configuration having a tensile modulus of about 0.02 MPa to about 0.8 MPa at 30% strain.
11. The method of claim 10 , wherein said cryogel is formed from an aqueous solution further comprising poly (vinyl pyrrolidone).
12. The method of claim 10 , wherein said pre-formed flexible-walled balloon has a shape in the expanded configuration generally conforming to the shape of a nucleus pulposus.
13. The method of claim 10 , wherein said biocompatible hydrogel is a thermogelling hydrogel.
14. The method of claim 13 , wherein said thermogelling hydrogel is prepared from a mixture of a first aqueous solution comprising poly (N-isopropylacrylamide) and a second aqueous solution comprising poly (vinyl alcohol).
15. The method of claim 13 , wherein said thermogelling hydrogel is prepared from a mixture of an aqueous solution comprising a poly (N-isopropylacrylamide) and a second aqueous solution comprising poly (ethylene glycol).
16. The method of claim 13 , wherein said thermogelling hydrogel is prepared from an aqueous solution comprising a poly (N-isopropylacrylamide)-grafted poly (ethylene glycol) polymer.
17. The method of claim 13 , wherein said thermogelling hydrogel is prepared from an aqueous solution comprising a poly (ethylene glycol)-poly (N-isopropylacrylamide)-poly-(ethylene glycol) triblock polymer.
18. The method of claim 13 , wherein said thermogelling hydrogel is prepared from a mixture of a first aqueous solution comprising poly (vinyl alcohol) and a second aqueous solution comprising poly (ethylene glycol).