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Flush patch for elastomeric implant shell

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Flush patch for elastomeric implant shell


An elastomeric prosthetic breast implant is provided having a shell and a patch forming a flush interface with the shell and no sudden surface steps on both interior and exterior surfaces of the shell.
Related Terms: Breast Implant

Browse recent Allergan, Inc. patents - Irvine, CA, US
Inventor: David J. Schuessler
USPTO Applicaton #: #20120303120 - Class: 623 8 (USPTO) - 11/29/12 - Class 623 
Prosthesis (i.e., Artificial Body Members), Parts Thereof, Or Aids And Accessories Therefor > Breast Prosthesis >Implantable

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The Patent Description & Claims data below is from USPTO Patent Application 20120303120, Flush patch for elastomeric implant shell.

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RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No. 13/288,885, filed Nov. 3, 2011, which is a divisional of U.S. patent application Ser. No. 12/431,070, filed Apr. 28, 2009, now issued as U.S. Pat. No. 8,070,809, which claims the benefit of U.S. Provisional Patent Application No. 61/038,919, filed on Apr. 28, 2008, the entire disclosures of which are incorporated herein by this specific reference.

FIELD OF THE INVENTION

The present invention relates to patches for elastomeric implants and, more particularly, to devices and methods for forming a patch flush with an elastomeric implant shell.

BACKGROUND OF THE INVENTION

Implantable prostheses are commonly used to replace or augment body tissue. In the case of breast cancer, it is sometimes necessary to remove some or all of the mammary gland and surrounding tissue that creates a void that can be filled with an implantable prosthesis. The implant serves to support surrounding tissue and to maintain the appearance of the body. The restoration of the normal appearance of the body has an extremely beneficial psychological effect on post-operative patients, eliminating much of the shock and depression that often follows extensive surgical procedures. Implantable prostheses are also used more generally for restoring the normal appearance of soft tissue in various areas of the body, such as the buttocks, chin, calf, etc.

Soft implantable prostheses typically include a relatively thin and quite flexible envelope or shell made of vulcanized (cured) silicone elastomer. The shell is filled either with a silicone gel or with a normal saline solution. The filling of the shell takes place before or after the shell is inserted through an incision.

One process for forming flexible implant shells for implantable prostheses and tissue expanders involves dipping a suitably shaped mandrel into a silicone elastomer dispersion. The outer silicone elastomer shell may have an anatomical configuration, in this case matching the breast, and comes off the mandrel with a shell hole. A patch over the shell hole typically includes an uncured portion directly over the hole and a cured portion covering that and adhered to the inner surface of the shell. The patch is cured and then the hollow interior of the shell is filled with an appropriate gel via a needle hole in the patch. The needle hole in the patch is then sealed with a silicone adhesive and the implant oven cured to achieve cross-linking of the gel.

Another process for forming implant shells is rotational molding, such as the system and methods described in U.S. Patent No. 6,602,452 to Schuessler. The process also results in a flexible implant shell having a hole that requires a patch.

Patches for flexible implant shells are sized larger than the manufacturing hole to provide some bonding area. The overlap of the patch on the shell results in a slight surface step on the inside or outside of the shell which may be noticeable in the finished product, which is undesirable. Also, such a palpable step or discontinuity may irritate tissue in contact with the exterior of the implant.

Despite many advances in the construction of soft prosthetic implant shells, there remains a need for a smoother joint between a patch and a manufacturing hole in the implant shell.

SUMMARY

OF THE INVENTION

In accordance with the present invention, a hollow medical implant comprises an elastomeric hollow shell having a contiguous and consistent wall except in an access region, and a patch extending thereacross. The patch is securely bonded to the shell and a peripheral edge of the patch and the shell cooperate to form a flush interface with no surface steps on both interior and exterior surfaces of the implant.

In another aspect, the invention includes a hollow medical implant, comprising an elastomeric hollow shell having a contiguous and consistent wall except in an access region. A patch extends across the access region of the shell and securely affixes thereto. The patch has an outer flange and the shell wall forms an exterior butt joint against a peripheral edge of the flange and overlaps an inner surface of the flange in a manner that results in no surface steps.

Both the elastomeric hollow shell and patch may be made of materials with similar elastic modulus, durometer and elongation, and may even be made of the same material. Desirably, the elastomeric hollow shell is made of a solvent-based solid elastomer and the patch is made of a liquid silicone rubber without a solvent. In one embodiment, the patch includes a stem projecting radially inward into the interior of the hollow shell and an outer flange extending circumferentially outward from the stem, wherein the shell wall forms a flush butt joint against a peripheral edge of the flange and overlaps an inner surface of the flange and extends at least to the stem. In another embodiment, the patch is a substantially flat disk shape and the shell wall covers an entire inner face of the patch. The patch flange may increase in radial thickness from its periphery toward its center such that the portion of the shell wall that overlaps the inner surface of the flange is thickest adjacent the flange periphery.

In one form, the implant is for implantation in the breast and the elastomeric hollow shell is accordingly shaped. Other implant applications include for the buttocks, testes, calf, etc. In some embodiments, the implant is a tillable implant, for example, a saline tillable breast implant or tissue expander. In other embodiments, the implant is an intragastric balloon.

In some embodiments, the implant is a tillable or inflatable implant such as a saline fillable breast implant or an inflatable intragastric balloon and the patch includes a fill valve for facilitating inflation of the implant.

The present invention also embodies a method of formation of a medical implant, comprising:

providing a mold cavity having a sprue orifice;

covering the sprue orifice with a patch;

introducing a silicone elastomer into the mold cavity;

causing the silicone elastomer to distribute generally evenly around the mold cavity and over at least a portion of the patch;

curing the silicone elastomer to form a hollow implant shell having the patch bonded thereto; and

removing the implant shell from the mold cavity.

The patch may be shaped relative to and positioned within the mold cavity so that after formation of the hollow implant shell a peripheral edge of the patch and the shell cooperate to form a flush interface with no sudden surface steps on both interior and exterior surfaces of the implant. The step of introducing preferably includes introducing the silicone elastomer into the mold cavity through the patch. During the step of causing the silicone elastomer to distribute generally evenly around the mold cavity the method may include extending a vent tube through the patch and venting gas from within the mold cavity though the vent tube. Also, a tube may be inserted through the patch for filling the mold cavity with a silicone gel through the tube, which is then cured to form a solid prosthesis.

BRIEF DESCRIPTION OF THE DRAWINGS

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:

FIG. 1 is a plan view from above of a elastomeric implant sealed by a patch construction in accordance with the prior art;

FIG. 2 is a cross-section, to a slightly enlarged scale, when viewed on section line 2-2 of the FIG. 1;

FIG. 3 shows, in cross-section, an alternative patch construction in accordance with the prior art with a chamfered edge of the aperture to be sealed by the patch;

FIG. 4 shows, in cross-section, an alternative patch construction in accordance with the prior art;

FIG. 5 shows, in cross-section, a still further alternative patch construction in accordance with the prior art;

FIG. 6 is a schematic cross-section of an exemplary rotational molding system for use in forming the shell of a soft prosthetic implant of the present invention;

FIGS. 7 and 8 are bottom and sectional views of one embodiment of a mold for use in a rotational molding system such as shown in FIG. 6 to form an elastomeric implant that receives a flush patch of the present invention;

FIG. 9 is a cross-sectional view through an exemplary mold of the present invention showing various elements of a process for forming a flush patch;

FIG. 10 is a cross-sectional view through an exemplary gel-filled breast implant prosthesis having a molded-in-place flush patch formed in accordance with the present invention;

FIG. 11A is a detailed view of the interface between the flush patch and the shell of the breast implant prosthesis of FIG. 10; and

FIG. 11B is a detailed view of the interface between an alternative flush patch and the shell of the breast implant prosthesis of FIG. 10.

DETAILED DESCRIPTION

OF THE PREFERRED EMBODIMENTS

The present invention provides a gel-filled implant prosthesis incorporating a shell composed partly or entirely of a fluid barrier layer, preferably a silicone elastomer. The implant shells of the present invention may have a single material layer of homogeneous or uniform composition, or a laminated or layered configuration. The primary application for gel-filled soft implants is to reconstruct or augment the female breast. Other potential applications are implants for the buttocks, testes, or calf, among other areas. Moreover, though the present invention is particularly advantageous for gel-filled implants, saline filled breast implants or intragastric balloons may be modified to incorporate the benefits herein. Further, tissue expanders which may not be viewed as implants, per se, may also use the concepts disclosed herein. For that matter, the term implant as used herein refers to long and short-term implanted devices.

The implant shells of the present invention are desirably formed using a rotational molding system, such as disclosed in U.S. Pat. No. 6,602,452 to Schuessler, which is expressly incorporated herein by reference. Schuessler discloses a rotational molding machine for forming medical articles, in particular for molding silicone elastomer shells for breast implants. Molding machines other than those that rotate the mold, such as insert molding machines in general (the insert being the patch), may conceivably be used to mold in place the flush patch as described herein, and the advantages of the present invention may even be incorporated into traditional dip molding method, though modifications to the typical dipping mandrel and rod are necessary and will not be described herein.

The advantage of insert molding the patch in place within the shell is that the patch integrates with the shell. That is, the shell material flows over and around the patch and bonds tightly thereto, if not actually melding together to blur any distinct boundaries between the two items. How much of this integration occurs depends on the similarity in the materials, and the mold process parameters such as time and temperature. Preferably the shell comprises a solvent-based solid elastomer (e.g., silicone) and the patch is formed of a liquid silicone rubber (LSR) without a solvent and with a similar elastic modulus, durometer and elongation as the shell. Similar physical properties permits the patch to deform and stretch with the shell which reduces stress concentrators. Alternatively, the materials of the patch and shell could be identical.

FIGS. 1 and 2 of the drawings illustrate a flexible implant construction of the prior art. A breast prosthesis 21 comprises a textured envelope or shell 22 formed by a conventional molding process on a mandrel. A patch 23 covers an aperture in the shell 22 formed during the mold process. As best seen in FIG. 2, the patch 23 comprises an external overlay 24 and an internal underlay 25, with respective overlapping portions 26, 27, so as to form a sandwich structure. The overlapping sections of the patch 23 and shell 22 as well as those portions of the overlay 24 and underlay 25 which are in contact are bonded together.

The patch can be bonded to the shell by a variety of means including chemical welding or bonding, ultrasonic welding, and heat/pressure fusing. One disadvantage of this process is that a ridge 28 is formed on the exterior as well as a concentric ring 29 formed by the bonding process, part or all of which may be smooth, i.e. where the textured exterior surface area of the shell 22 may be reduced by the overlap of the overlay 24. This is undesirable, because the exterior textured surface area ought to be maximized for surgical reasons. Moreover, the circular ring 29 and peripheral ridge 28 form a ridge on the breast prosthesis 21 that is discernible by feel after implantation. The peripheral portion 27 of the underlay 25 also presents a small internal ridge which is palpable after implantation. These physical discontinuities not only present unnatural tactile sensations, but may result in undesirable chafing between the prosthesis 21 and the breast cavity.

FIG. 3 illustrates an implant shell 33 of the prior art having a chamfered edge 32 around the mold aperture and opening toward the interior of the shell. A patch member 34 bonded to the interior of the shell 33 includes a conical portion which fits closely against the chamfered edge 32 and a peripheral skirt 35 that abuts the interior of the shell 33. This construction eliminates an external ridge, such as at 28 in FIG. 2, but the peripheral skirt 35 still presents an interior ridge.

Alternatively, as shown in FIG. 4, a patch applied from the interior of the shell 33 in FIG. 3 may comprise two parts, a cap plug portion 34a, slightly larger than the aperture, and an underlay portion 34b, larger still, such that when bonded together, the whole patch extends radially around the aperture in the same manner illustrated in FIG. 3.

The configurations shown in FIGS. 3 and 4 have the advantage that a stronger bond is formed between the edge of the aperture and the patch, since the edge area is increased by virtue of the chamfer 32, when compared to a squared edge, and that no ridge is formed on the exterior at the joint between the patch and the shell. However, as mentioned above, an interior ridge remains. It will be appreciated that the presence of any detectable seam between the patch and the shell represents a stress point which could possibly fail giving rise to leakage of fluid from the prosthesis, which must be avoided.

Finally, FIG. 5 illustrates another patch configuration of the prior art in which a prosthesis 40 includes a patch 42 closing a mold aperture of a shell 44. The patch 42 comprises an external surface 46 visible through the aperture, and an internal surface 48. The aperture has a chamfered mouth 52 to which a peripheral extent of the external surface 46 conforms. The internal surface 48 extends outward from the mouth 52 in a skirt 54 that terminates at a peripheral edge 56. This patch configuration once again presents a smooth external surface to the prosthesis 40, with no ridge, and is somewhat more streamlined than earlier versions, but the internal peripheral edge 56 remains. Again, the edge 56 presents a relatively sudden surface step and stress point around the patch 42 that is discernible from outside the patient after implantation. In this context, a surface step is a relatively sudden surface change such as an increase or decrease in thickness at the shell wall/patch boundary.

FIG. 6 is a schematic of an embodiment of a rotational molding system similar to that disclosed in Schuessler, U.S. Pat. No. 6,602,452, which can be used to form implant shells of the present invention. A two-piece case mold 120 affixes to a multi-axis rotational mold machine 122 by clamps securing top mold piece 124 and bottom mold piece 126 to clamp base 128 at top locking groove 130 and bottom locking groove 132, respectively. Vacuum connection 134 runs through one arm of the mold machine 122 to a vacuum opening 135. Material connection tube 136, through which silicone elastomer, liner materials, and/or air are injected into the mold cavity 140, may run through or along the same arm 142 as the vacuum connection 134 or by means of another arm 144. The input fluid then continues through a circular sprue tube 145 fitted in a circular opening (not numbered) of bottom mold piece 126. The sprue tube 145 defines a hollow bore that allows materials to enter an internal cavity of the two-piece case mold 120.

The hub 146 of the two arms rotates about axis A in the horizontal direction, while the arms 142, 144 rotate about axis B, which may be perpendicular to axis A. This allows a liner material or silicone elastomer material to uniformly coat the surface of the mold cavity 140. Two-piece case mold 120 may be manufactured from copper, aluminum, or other materials. The top mold piece 124 and bottom mold piece 126 fit together at their mating surfaces, seal with an O-ring 150, and then lock into clamp base 128 of multi-axis rotational molding machine 122.



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Prosthesis (i.e., artificial body members), parts thereof, or aids and accessories therefor
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stats Patent Info
Application #
US 20120303120 A1
Publish Date
11/29/2012
Document #
13570102
File Date
08/08/2012
USPTO Class
623/8
Other USPTO Classes
606/1, 606192, 606191
International Class
/
Drawings
7


Breast Implant


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