Self-sealing shell for inflatable prostheses

Abstract

A self-sealing shell useful as a component of a soft fluid-filled prosthetic implant is provided. The shell is at least partly constructed of a wall made of a colloid of an elastomeric polymer matrix and particles of a water-swellable material distributed therein.

Claims

1. A method of making an implantable and inflatable prosthesis, the method comprising the steps of: providing a curable polymer-based liquid; distributing a plurality of solid, water-swellable particles in the liquid to form a fluid mixture comprising the liquid polymer and the solid, water-swellable particles; solidifying the mixture to form a matrix of the polymer having the solid, water-swellable particles occupying enclosed spaces in the matrix; and forming the mixture into a wall of an inflatable prosthesis comprising the matrix and enclosed particles, wherein, when the wall is contacted with an aqueous fluid, the water-swellable particles expand and the wall becomes self-sealing to a needle puncture.

2. The method of claim 1 wherein the wall is not self-sealing when it is in a dry state.

3. The method of claim 1 wherein the water-swellable particles make up between about 2% to about 40% by weight of the mixture.

4. The method of claim 1 wherein the water-swellable particles make up about 25% by weight of the mixture.

5. The method of claim 1 wherein the water-swellable particles are a hydrogel or polyethylene glycol (PEG) material.

6. The method of claim 5 wherein the water-swellable particles have a molecular weight of between about 200 and about 10,000 Daltons.

7. The method of claim 1 wherein the forming is conducted by rotational molding.

8. The method of claim 1 wherein the prosthesis configured to be inserted into a breast cavity in an empty or partially-filled state before being filled with physiological saline via a needle, the empty or partially-filled state reducing a required size of an incision.

9. The method of claim 1 wherein the prosthesis is configured to be used as an inflatable member of a gastric balloon useful for treatment of obesity.

10. The method of claim 1 wherein the prosthesis comprises a single layer of the matrix around an entirety of the prosthesis.

11. A method of making an implantable soft prosthesis, the method comprising: providing a liquid polymer matrix; distributing a plurality of particles of a water-swellable material in the polymer matrix to form a colloid; solidifying the colloid into a solid matrix of the polymer entrapping the particles; forming the colloid into a wall of a shell comprising the solidified matrix and entrapped particles for an inflatable prosthesis; and contacting the wall with an aqueous fluid such that the particles swell and the wall becomes capable of self-sealing around a needle puncture.

12. The method of claim 11 wherein the wall is not self-sealing when it is in a dry state.

13. The method of claim 11 wherein the water-swellable particles make up between about 2% to about 40% by weight of the colloid.

14. The method of claim 11 wherein the water-swellable particles make up about 25% by weight of the colloid.

15. The method of claim 11 wherein the water-swellable particles are a hydrogel or polyethylene glycol (PEG) material.

16. The method of claim 15 wherein the water-swellable particles have a molecular weight of between about 200 and about 10,000 Daltons.

17. The method of claim 11 wherein the forming is conducted by rotational molding.

18. The method of claim 11 wherein the prosthesis is configured to be inserted into a breast cavity in an empty or partially-filled state before being filled with physiological saline via a needle, the empty or partially-filled state reducing a required size of an incision.

19. The method of claim 11 wherein the prosthesis is configured to be used as an inflatable member of a gastric balloon useful for treatment of obesity.

20. The method of claim 11 wherein the prosthesis comprises a single layer of the matrix around an entirety of the prosthesis.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Features and advantages of the present invention will become appreciated as the same become better understood with reference to the specification, claims, and appended drawings wherein:

(2) FIG. 1 is a cross-sectional view through a self-sealing implant prosthesis of the present invention having a molded-in-place flush patch;

(3) FIG. 2A is a sectional view through a portion of the wall of the self-sealing implant prosthesis of FIG. 1 prior to implant;

(4) FIG. 2B is a sectional view through a portion of the wall of the self-sealing implant prosthesis of FIG. 1 after implant and absorbance of an aqueous fluid to cause swelling of particles therein; and

(5) FIGS. 3A-3B show needle puncture of and subsequent withdrawal from the implant prosthesis wall of FIG. 1 illustrating a self-sealing character of the wall.

DETAILED DESCRIPTION

(6) The present invention provides a fluid-filled inflatable prosthesis formed with a flexible outer shell having a wall that is at least partly constructed of a polymer matrix and a plurality of particles of material evenly or randomly distributed in the matrix. The shell wall self-seals around needle punctures.

(7) The present invention is especially useful for soft fluid-filled implants, for example, but not limited to, implants useful in breast reconstruction or breast augmentation procedures.

(8) FIG. 1 illustrates an exemplary cross-section of a prosthesis, for example, a fluid-filled breast implant 20 of the present invention. The implant 20 includes an elastomer shell 22 having an anatomical configuration, in this case, a configuration suitable for augmenting or reconstructing a human breast. The shell 22 is shown filled with a fluid such as physiologic saline 30. A patch 24 covers an aperture left over from a dipping or rotational molding process used to form the shell 22.

(9) FIG. 2A shows a wall 28 of the shell 22 prior to the shell 22 being filled with saline. The wall 28 may make up the entire shell 22 or may make up only a portion of the shell 22. The wall 28 comprises an elastomer component 32 and discontinuous particles 34 of a swellable material dispersed in the elastomer component 32. Turning now to FIG. 2B, the wall 28 is shown after having been contacted with an aqueous fluid, for example, water. When the wall 28 is contacted with an aqueous fluid, the particles 34 of swellable material enlarge such that the wall 28 becomes self-sealing to a needle puncture.

(10) In accordance with one aspect of the invention, the wall 28 has the characteristic of being not self sealing when it is in a dry state (FIG. 2A), but nearly substantially entirely self-sealing when in the wet state (FIG. 2B), that is, after it has been contacted with water or other suitable aqueous medium. Contact with an aqueous fluid may be accomplished by exposing the shell or wall of said shell to liquid water, steam or humid environment.

(11) The shell wall 22 includes a polymer matrix 32 and a plurality of particles 34 substantially uniformly or randomly distributed therein. It can be said that the particles 34, in a sense, are entrapped in the polymeric elastomer component 32, or occupy enclosed spaces within the elastomeric material which forms a matrix around the particles.

(12) The polymer matrix 32 may be a silicone elastomer such as a dimethyl silicone elastomer. The polymer matrix 32 may comprise a substantially homogeneous dimethyl-diphenyl silicone elastomer. One especially advantageous composition useful in the present invention is described in Schuessler, et al., U.S. application Ser. No. 12/179,340, filed Jul. 24, 2008, albeit for gel-filled prostheses, the disclosure of which is incorporated herein in its entirety by this specific reference.

(13) In one aspect of the present invention, the shell wall 22 comprises a colloid of the matrix 32 having the swellable particles 34 therein. A colloid in this sense generally means a material made up of a system of particles dispersed in a continuous medium. The size of the particles can vary, and they remain dispersed indefinitely in the medium. In contrast with some definitions of colloid, in accordance with the present invention the linear dimensions of the particles need not be within a specified range. For purposes of the present invention, the swellable particles may be in the form of a solid or a liquid, as long as they do not mix or otherwise dissolve into the surrounding matrix material 32.

(14) In one embodiment, the shell wall 22 is formed by dispersing solid particles 34 in a liquid matrix 32, which is then cured. In another embodiment, the shell wall 22 is formed by creating an emulsion of liquid particles 34 immiscible in a liquid matrix 32, which is then cured. The elastomeric component of the shell wall 22 may be a non-water-swellable silicone elastomer within which water-swellable solid or liquid particles are entrapped.

(15) In one aspect of the invention, the particles 34 are a water-swellable material which swells upon contact with an aqueous fluid. For instance, the material of the particles 34 may be a hydrogel material, or polyethylene glycol (PEG) material. The particles 34 may be in liquid or solid form, as mentioned, and the same substance may be provided in either phase.

(16) In some embodiments, the water swellable particles 34 have a molecular weight of between about 200 and about 10,000 Daltons. In some embodiments, the particles 34 make up about 2% by weight of the particle/matrix composition. In some embodiments, the particles 34 make up at least about 2% by weight of the particle/matrix composition, up to about 40% by weight of the composition. In some embodiments, the particles make up about 25% by weight of the composition.

(17) The combination of the polymer matrix 32 and particle 34 wall construction self-seals around needle punctures once the material has been exposed to or contacted with an aqueous fluid such as water, saline, body fluid, or other biocompatible liquid. Once contacted with an aqueous fluid, the wall 22 allows the fluid to enter the elastomer matrix and upon contacting the particles, the particles 34 swell and expand as shown in FIG. 2B. Although not wishing to be bound by any specific theory of operation, it is believed that the swelling of the particles 34 creates compressive forces in the wall which makes the shell self-sealing to puncture, for example, with a standard gauge needle.

(18) Various processes are known for forming the flexible implant shells for implantable prostheses and tissue expanders of the present invention. In each, a plurality of the particles 34 of the water-swellable material are distributed in a quantity of the liquid polymer matrix 32 to form a colloid. Again, the particles 34 may be in solid or liquid form. The colloid is then solidified to form a portion of the shell wall 22. The colloid may be formed as a sheet material and used for a patch of an otherwise non-self-sealing shell, or may be used as the entire shell, including the patch. In the former case, the colloid first solidifies and is then formed into part of the shell, while in the latter case, the colloid simultaneously solidifies and forms the shell. The shell is then exposed to an aqueous fluid (such as by filling with saline) such that the particles swell and the colloidal portion of the shell wall is capable of self-sealing around needle punctures. In one process, a suitably shaped mandrel may be dipped one or more times into a dispersion of the polymer matrix with distributed water-swellable particles. Each time the mandrel is withdrawn from the dispersion and the excess is allowed to drain from the mandrel. After the excess dispersion has drained from the mandrel at least a portion of solvent within the dispersion is allowed to evaporate to stabilize the silicone elastomer coating. Also, curing may take place between dippings. The process is then repeated several times until a shell of the desired thickness is formed. Furthermore, the layered structure of current silicone elastomer shells can be made by sequentially dipping the mandrel in different dispersions.

(19) In one embodiment, the invention comprises forming an elastomer shell 22 within an injection or rotational molding system. A liquid quantity of the polymer matrix with distributed water-swellable particles is introduced within a mold cavity, which then may be rotated about multiple axes. The liquid evenly coats the inside of the mold cavity as it rotates, and heat is applied to cure the liquid to a more solid form. One exemplary rotational molding system disclosed in U.S. Pat. No. 7,165,964 to Schuessler, the entire disclosure of which is incorporated herein, incorporates a vent system to remove volatilized solvents, and a mold liner to eliminate a mold seam. The patch 24 may be molded in place within the mold cavity, as disclosed in U.S. patent application Ser. No. 12/431,070 filed Apr. 28, 2009, and having common inventor and common assignee herewith, the entire disclosure of which is incorporated herein by this specific reference.

(20) In one embodiment, the implant 20 is a breast implant or a tissue expander for a breast. The implant 20 may be inserted into a breast cavity in an empty or partially-filled state. Introducing an implant that is not completely filled naturally reduces the required size of the incision, which is beneficial as it leaves a smaller scar. Once in place the surgeon fills the hollow interior of the shell 22 with an appropriate fluid 30 such as physiologic saline via a needle. Advantageously, the entire shell wall, and preferably also the patch 24, is formed of the self-sealing construction and thus there is little trouble locating an appropriate injection site.

(21) In another embodiment, the implant 20 is an inflatable member of a gastric balloon useful for treatment of obesity.

(22) FIG. 3A illustrates a needle 40 attached to a syringe 42 penetrating a location in the shell wall 22. An additional quantity of the fluid 30 is then injected into the shell 22 to either incrementally expand the shell, as with tissue expanders, or fill the shell to a predetermined volume. The final volume varies depending on the desired outcome. Additional fluid adjustments may be desired to fine tune the final volume. In that case, a needle is again used to either remove or add fluid.

(23) FIG. 3B shows the shell wall 22 after removal of the needle 40. The swelled particles 34 tend to migrate into the puncture created by the needle 40, and form a seal 44 in the puncture. Multiple punctures at different locations may be made in the shell 22, all of which seal as in FIG. 3B. The advantage of having the entire shell 22 available for injection will be obvious to those of skill in the art.

(24) As mentioned above, the entire shell 22 of the inflatable prosthesis may comprise a single layer of the matrix 32 and particles 34 around the entire shell. Alternatively, however, just a portion of the shell 22, such as an anterior face, may include the self-sealing characteristic in accordance with the invention.

(25) The present invention further provides methods of making an implantable soft prosthesis. The methods generally comprise the steps of providing a liquid polymer matrix such as a silicone elastomer in a flowable form and distributing particles of a water-swellable material in the polymer matrix to form a fluid elastomer/particle mixture, for example, a colloid. While in a fluid state, the mixture is formed into a membrane or layer which, when solidified, can be used to form at least a part of a shell wall for an inflatable prosthesis. In order to cause the prosthesis to become self-sealing as described and shown elsewhere herein, the wall is contacted with or exposed to an aqueous fluid.

(26) In one embodiment, the region of the shell having the self-sealing colloid of the matrix 32 and particles 34 is approximately or more of the surface area of the entire shell. Still further, a fill patch over a manufacturing aperture in the shell may be the only portion of the implant which is self-sealing in accordance with the invention.

EXAMPLE

(27) A silicone elastomer dispersion (polydimethyl siloxane dispersed in a xylene solvent such as NuSil MED-6640) at approximately 1000 cps is mixed with polyethylene glycol (8000 MW) powder in a ratio of about 10% by weight of silicone solids.

(28) This mixture is dip cast over a mandrel in the desired shape of the shell. The mixture is dipped several times to achieve a thickness of 0.050 on the mandrel surface after air drying and removal of the solvent. The shell is cured at about 121 C for about 90 minutes. The shell is removed from the mandrel. After being contacted with water, the shell is self sealing to a needle puncture.

(29) It is contemplated that the self sealing materials of the present invention may be formed into very thin laminates which are applied in a layered fashion to traditional silicone elastomeric shells. It is further contemplated that the self-sealing material may make up one or more layers of a shell which are sandwiched between layers of silicone elastomer such that the self sealing layer is spaced apart from inner and outer surfaces of the shell wall.

(30) Although the invention has been described and illustrated with a certain degree of particularity, it is understood that the present disclosure has been made only by way of example, and that numerous changes in the combination and arrangement of parts can be resorted to by those skilled in the art without departing from the scope of the invention, as hereinafter claimed.