WO2013181034A1

WO2013181034A1 - Breast implant with shell failure detection

Info

Publication number: WO2013181034A1
Application number: PCT/US2013/042172
Authority: WO
Inventors: David S. Hollstien
Original assignee: Hollstien David S
Priority date: 2012-05-30
Filing date: 2013-05-22
Publication date: 2013-12-05

Abstract

There exists a need therefore, for a breast implant shell failure detection mechanism that allows for non-invasive confirmation of the integrity of the implant shell to determine if material contained within the implant has been or may soon be released into the patient. This need is met by the present invention, which in one embodiment is a breast implant comprised of an external shell, and an internal shell between which a vacuum established. A leak is detected when this vacuum is relieved and a radiological indicator is set. The inner and outer shells are, for example, made from a tough silicone formulation.

Description

BREAST IMPLANT WITH SHELL FAILURE DETECTION

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority to U.S. Prov. App. 61/652,863 filed May 30, 2012, which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

[0002] Field of the Invention: The present invention relates to prosthetic breast implants.

[0003] Prosthetic breast implants are constructed with a tough, elastic silicone shell which is typically filled with a viscous silicone gel, or a sterile saline solution. The shell is manufactured by spraying or dipping a mandrel with silicone material which is cured and filled through a hole on the posterior side of the implant. The hole is plugged and is typically sealed with a silicone patch using heat or chemical methods.

[0004] The rupture of silicone implants had been widely publicized and the leakage of silicone material into patients has been attributed to a wide variety of disease processes. While extravasated silicone has not been shown to have caused these maladies, concern among patients and physicians remains high.

[0005] Manufactures of breast implant have extensive history and experience with the materials used in breast implants. The mechanical properties and biocompatibility of silicone shell materials have been proven over many years. Due to the history of breast implant leakage, regulatory agencies are very hesitant to allow manufactures to change these materials without thorough testing that can take decades to complete.

[0006] Breast implant shell failures can be massive ruptures or small creases that leak over a long period of time. The failures can result from an instantaneous trauma or as a result of cyclical fatigue of the shell. Because extravasated silicone is difficult to remove from the patient, it is beneficial to detect shell failures early when the shell is initially weakened or otherwise compromised.

[0007] Breast implant shells are sometimes regarded as "semi-permeable" in that they allow a small fraction of silicone gel to "bleed" through the shell and migrate into the capsular area surrounding the implant. Medical studies are conflicting, but some have shown that "gel bleed" can cause capsular contraction and auto-immune disease. To reduce gel bleed, implant shells are often constructed with an outer layer composed of a mixture of polydimethylsiloxane and amorphous silica and an inner layer of

polydimethylsiloxane that is more effective in blocking gel bleed.

[0008] Current non-invasive methods for determining implant failure include manual examination, radiologic imaging such as X-ray and magnetic resonance imaging (MRI). Numerous studies have shown that none of these can be considered to be reliable techniques.

BRIEF SUMMARY OF THE INVENTION

[0009] There exists a need therefore, for a breast implant shell failure detection mechanism that allows for non-invasive confirmation of the integrity of the implant shell to determine if material contained within the implant has been or may soon be released into the patient. This need is met by the present invention, which in one embodiment is a breast implant comprised of an external shell, and an internal shell between which a vacuum established. A leak is detected when this vacuum is relieved and a radiological indicator is set.

[00010] The inner and outer shells are, for example, made from a tough silicone formulation such as Silastic®, made by the Dow Chemical Company. The tensile strength and tear propagation properties of these materials have been optimized for use in breast implants. In the present invention, the outer shell construction and thickness may be identical to a conventional implant thereby ensuring the overall rupture integrity of the prosthesis. The inner shell may be made from the same materials, but may be a made thinner and may have surface features such as a pattern or texture to hold the shells apart so that a continuous vacuous cavity is formed between the inner and outer shells over most of the area of the breast implant. The cavity does not extend over the fill hole plug.

[00011] This vacuous cavity is a region where the pressure is negative with respect to the internal body pressure and to atmospheric pressure. The cavity forms a boundary to silicone gel which only migrates from a region of high pressure to a region of low pressure. Therefore, silicone gel that may bleed or migrate into the vacuous cavity through the inner shell will not migrate further through the outer shell and out of the implant as long as a vacuum exists in the cavity.

[00012] The implant is filled with a low molecular weight silicone gel most of which is placed inside the inner shell. A small amount, e.g. less than 3 cc, of silicone gel filler material may be inserted or injected between the inner and outer shells to act as a lubricant and to ensure that a seal does not form between the inner and outer shells.

[00013] A vacuum relief indicator may be a conically wound compression spring which separate a pair of radiologically opaque disks. The spring and disks may be made from an implantable stainless steel such as 316. When fully compressed the conical spring lies flat between the disks, however, when uncompressed, the spring separates the disks by 1 to 3 cm. The disks are approximately 2 cm in diameter so the compressed vacuum relief indicator can pass through the incision along with the more flexible parts of the implant during surgical implantation. A compressed vacuum relief indicator is placed between the inner and outer shells and is positioned on the posterior side of the implant, adjacent to the fill hole. A circular step protruding approximately 1 mm on the outer surface of the inner shell may hold the vacuum relief indicator in proper position.

[00014] The uncompressed length and spring rate of the vacuum relief indicator spring are selected to draw fluid between the inner and outer shells during a shell failure. The spring rate must not be so high as to stretch, fatigue or damage the shells when a failure has not occurred. The shell thicknesses may be increased or alternate materials may be used in the region surrounding the vacuum relief indicator to increase its strength.

[00015] The time necessary for the vacuum relief indicator spring to become fully uncompressed is determined by the vacuum relief indicator spring characteristics, the implant rupture size and the viscosity of the silicone gel. For example, a given spring stiffness and gel viscosity, the vacuum relief indicator spring will take longer to become fully compressed with a relatively small rupture than with a larger rupture. Alternatively, the spring characteristics and silicone gel viscosity may be adjusted to provide an indication of the size of the implant rupture when the vacuum relief indicator is checked at regular or known time intervals.

[00016] The cavity between the inner and outer shells may be sealed with an annular bond surrounding the fill hole. The shells may be sealed in a vacuum with the vacuum relief indicator clamped such that the spring is fully compressed. [00017] Once the shells are sealed together, the bulk of the filler material is placed into the inner shell and the implant is plugged using conventional methods.

[00018] If a failure develops in the outer shell, a negative pressure at the failure point draws body fluids into the vacuous cavity which relieves the vacuum and allows the vacuum relief indicator spring to separate the radiologically opaque disks. This process continues until the spring is fully uncompressed. The volume of body fluids drawn in is determined by the volume uncompressed spring length and the disk diameters. The separation of the radiologically opaque disks indicates a shell failure and can be observed using common X-ray techniques or other forms of non-invasive imaging, e.g., ultrasound. While in this case, no silicone material is extravasated from the implant, the indication of a shell failure is appropriate since the outer shell has been breached and therefore the overall shell strength has been reduced. In this way, an early warning of an implant shell failure is provided

[00019] If a failure develops in the inner shell, the negative pressure will draw viscous silicone filler material from inside the inner shell into the vacuous cavity. This relieves the vacuum and allows the vacuum relief indicator spring to separate the radiologically opaque disks. This process continues until the spring is fully uncompressed. While in this case, no silicone material is extravasated from the implant, the indication of a shell failure is appropriate since the inner shell has been breached. This is an additional early warning of an implant failure.

[00020] If a failure develops in both the outer and inner shells, the negative pressure will draw a mixture of body fluids and silicone filler material into the cavity between the shells. This relives the vacuum relief indicator spring which allows the radiologically opaque disks to separate. This process continues until the spring is fully uncompressed. In this case, a quantity of silicone material will have been extravasted from the implant, although, some of it will be drawn into the cavity.

[00021] The separation of the vacuum relief indicator disks may also be simply felt by a patient during a self examination or palpated by a physician. This is most likely to possible in circumstances where the prosthesis size is relatively small and the surrounding tissue is not overly thick or dense.

[00022] Depending on the size of the rupture, the vacuum relief indicator disks may separate slowly over weeks or months, however, the separation distance is a cumulative measure of the leak volume. The spring in the vacuum relief indicator sustains a negative pressure at a failure point until the spring becomes fully uncompressed. A, e.g., 2 cm, long vacuum relief indicator spring with, e.g., 2 cm, diameter disks provides a negative pressure in the vacuous cavity until approximately, e.g., 6 cc, of fluid is drawn between the inner and outer shells.

[00023] An additional advantage of the present invention is with regard to reducing silicone gel bleed. Gel that permeates through the inner shell is retained in the cavity between the inner and outer shells until the pressure inside the outer shell is greater than surrounding capsular pressure. Regular assessment of the vacuum relief indicator will identify implants with shell failures or excessive accumulated silicone gel bleed.

[00024] The disclosed means to detect implant failure can also allow medical personnel to confirm that the implant shells are fully intact prior to prior to surgical implantation. Prior to implantation of the prosthesis, the separation of the vacuum relief indicator disks can be inspected visually.

[00025] In another variation of the invention, the separation of vacuum relief indicator disks can be determined electronically using radio frequency signals. The determination may be by measuring the effect on an electromagnetic field generated by a device external to the patient. For example, if the radiologically opaque disks may be replaced with a pair of tuned antenna circuits. When the circuits are in close proximity, corresponding to the condition where no shell failure exists, the inductive coupling between the antenna circuits will be greater than when they are separated. The amount of coupling will directly affect the resonant frequency of the antenna circuits and can be measured externally. To minimize the effect of the spring on the electromagnetic field, the spring may be coated with a silicone polymer to insulate each turn which reduces induced eddy currents.

[00026] In another variation, conventional radio frequency identification (RFID) circuitry is used to communicate with an electronic microprocessor located on a printed circuit board that replaces one or both of the radiologically opaque disks inside the implant. A sensor connected to the microprocessor allows the status of the vacuum relief indicator to be measured and transmitted via a modulated carrier signal. This signal is electronically picked up, decoded and presented to medical personnel.

[00027] In another variation, an electronic absolute pressure sensor may be used to measure the vacuum between the inner and outer shells. The sensor used may be a commercially available sensor, e.g., ST Microelectronics, LP331AP. The vacuum measured by the sensor may be retrieved and transmitted using a microprocessor.

BRIEF DESCRIPTION OF THE DRAWINGS

[00028] These and other features, aspects and advantages of the present invention will become better understood with regard to the following description, accompanying figures where:

[00029] Figure 1 is a diagram of a posterior side of breast implant with the disclosed failure detection mechanism.

[00030] Figure 2 is a section view of the vacuum relief indicator positioned between the inner and outer shells when the shells have not failed.

[00031] Figure 3 is a section view of the vacuum relief indicator positioned between the inner and outer shells when the shells have failed.

[00032] Figure 4 is a diagram showing an embodiment of the pattern on the outer surface of the inner shell.

[00033] Figure 5 is a diagram showing the inner and outer shells and the inter-shell cavity between them.

DETAILED DESCRIPTION OF THE INVENTION

[00034] According to one embodiment of the present invention, there is provided an improvement to breast implants with a breast implant shell failure detection mechanism that allows for non-invasive confirmation of the integrity of the implant shell to determine if material contained within the implant has been or may soon be released into the patient.

[00035] All dimensions specified in this disclosure are by way of example only and are not intended to be limiting. Further, proportions shown in the figures are not shown to scale. As will be understood by those skilled in the art with regard to this disclosure, the actual dimensions of any device or part of a device disclosed in this disclosure will be determined by its intended use.

[00036] As used in this disclosure, except where the context requires otherwise, the term "comprise" and variations of the term, such as "comprising", "comprises" and "comprised" are not intended to exclude other additives, components, integers or steps. [00037] Referring now to Figure 1, there is shown the posterior side of a breast implant with a mechanism of detecting a shell failure. Breast implant (1) includes an outer shell (2) and an inner shell (3) between which is inter-shell cavity (10) where vacuum relief indicator (4) is positioned adjacent to fill hole (5) and held in place by retaining step (7). Inter-shell cavity (10) is the volume bounded by the inner surface of the outer shell (2) and the outer surface of inner shell (3).

[00038] Outer shell (2) may be smooth or textured on either its inner or outer surface. The inner surface of outer shell (2) and/or outer surface of inner shell (3) may be textured or formed with a pattern as shown in Figure 4. Small protrusions (1 1) which are molded on the outer surface of inner shell (3) hold the inner and outer shells apart while the partial vacuum exists in inter-shell cavity (10). Alternatively, a rough texture or ridges, or another pattern may be molded on the outer surface of inner shell (3). The height, size and spacing of the protrusions (1 1) are selected to ensure that silicone gel and/or bodily fluids can be drawn through the inter-shell cavity (10).

[00039] Figure 2 shows vacuum relief indicator (4) which includes radiologically opaque disks (8) attached to either end of conical spring (9). Vacuum relief indicator (4) is positioned between outer shell (2) and inner shell (3) inside inter-shell cavity (10). Vacuum relief indicator (4) is oriented such that radiologically opaque disks (8) will push outer shell (2) away from inner shell (3) as shown in Figure 3. The axis of the cylindrical volume between radiologically opaque disks (8) is positioned so that it remains generally normal to the surface of breast implant (1).

[00040]

[00041] Inner shell (3) and outer shell (2) may be made by spraying or dipping one or more layers of silicone onto a single mandrel. The silicone layers may be made of, e.g., NuSil MED-6655 and Nusil MED-6640.

[00042] A texture may be applied to the outer surface of an uncured layer of the inner shell (3) by coating the surface with crystalline material which may be sodium chloride. The crystalline material is removed by dissolving it with water after the layer is cured. The surface of the remaining layer has a roughness which is determined by the size of the crystals applied to the surface. Sodium chloride crystals are generally cube shaped and may have dimensions of, e.g., 0.1 mm to 1 mm, in each orthogonal dimension. Portions of inner shell (3) in the annular bond region (6) and the portion which comes into contact with vacuum relief indicator (4) are made smooth by masking or blocking the application of crystals on the surface. Sodium chloride is a desirable roughening material because it is inherently biologically compatible and therefore residual quantities which are not removed do not present a toxic hazard.

[00043] Outer shell (2) may be made by spraying or dipping additional layers of silicone onto the outer surface of the inner shell (3). To ensure that outer shell (2) does not bond or adhere to inner shell (3), inner shell (3) may first be coated with a bond inhibitor. The bond inhibitor may be a sugar such as glucose (CeHnOe). Portions of the inner surface of outer shell (2) in the annular bond region (6) which are intended to adhere to the outer surface of inner shell (3) are masked or blocked from the coating of bond inhibitor. This allows inner shell (3) to bond directly to outer shell (2) in annular bond region (6). Glucose is a potential bond inhibitor material because it is inherently biologically compatible and therefore residual quantities does not present a toxic hazard.

[00044] Vacuum relief indicator (4) may be encapsulated between inner shell (3) and outer shell (2) by compressing conical spring (9) between radiologically opaque disks (8) against the outer surface of inner shell (2) which is in direct contact with the mandrel, while layers of outer shell (3) are successively applied. To ensure that silicone material does not bond to conical spring (9) so as to limit its extension, a bond inhibitor may be applied to the surface of conical spring (9) and radiologically opaque disks (8).

[00045] When inner shell (3) and outer shell (2) are cured, the bond inhibitor may be removed by injecting water into the inter-shell cavity (10) which dissolves the glucose bond inhibitor. The dissolved glucose solution is removed from inter-shell cavity (10) and replaced with a small quantity of viscous silicone gel. Throughout this process conical spring (9) is held compressed between radiologically opaque disks (8). Once inter-shell cavity (10) is filled with silicone gel, the injection puncture is sealed with silicone adhesive.

[00046] Breast implant (1) is filled with silicone gel and fill hole (5) is sealed.

[00047] Alternatively, outer shell (2) may be made by spraying or dipping layers of silicone onto the outer surface of a first mandrel. The silicone layers may be cured using heat. The mandrel may have a cylindrical protrusion which will form a pocket in the inside of outer shell (2) to hold vacuum relief indicator (4) in position.

[00048] Inner shell (3) may be made by first spraying or dipping a second mandrel with silicone and curing the layer. A second coat of silicone is applied and the mandrel is placed between a two-part mold surrounding the mandrel. The negative of protrusions (1 1) and retaining step (7) are recesses on the inner surface of the mold. The mold cavity may be made 5 mm larger than the size of the mandrel with two coats of silicone. This allows the mandrel to be placed into the mold without disturbing the uniform coating of uncured silicone on the surface. The inner shell mandrel is hollow, which allows compressed air to inflate the cured layer of inner shell (3) and force the uncured silicone into the mold recesses. This silicone layer is cured using heat. A cylindrical recess on the inner shell mandrel and a corresponding protrusion on the mold form a pocket on the outside of inner shell (3) to hold vacuum relief indicator (4) in position.

[00049] Prior to inserting, inner shell (3) may be sprayed with silicone filler prior to insertion into outer shell (2). The silicone filler acts as a lubricant which inhibits adhesion between outer shell (2) and inner shell (3). Vacuum relief indicator (4) is positioned between the shells while conical spring (9) is fully compressed. Returning to Figure 1, outer shell (2) is sealed to inner shell (3) in the annular bond region (6) surrounding fill hole (5).

[00050] Figure 5 is a close up section view of the inter-shell cavity (10) between outer shell (2) and inner shell (3) which are held apart by protrusions (1 1).

[00051] Alternatively, the fill hole plug, outer shell (2) and inner shell (3) may be bonded in annular bond region (6) during a single bonding operation. Inner shell (3) is completely filled with silicone gel and the plug positioned over fill hole (5) and bonded in an evacuated chamber. This simultaneously removes air from the inter-shell cavity and bubbles from the silicone gel.

[00052] When a shell failure occurs, the vacuum in inter-shell cavity (10) is relieved which allows conical spring (9) to extend thereby separating radiologically opaque disks (8). If a partial shell failure or slow leak occurs, the change in separation distance over time is a measure of the leak rate.

[00053] In another variation, conical spring (9) is replaced with a closed cell foam which expands when the vacuum in inter-shell cavity (10) is relieved.

[00054] Although the present invention has been discussed in considerable detail with reference to certain preferred embodiments, other embodiments are possible. Therefore, the scope of this disclosure should not be limited to the description of the preferred embodiments contained in this disclosure. All references cited herein are incorporated by reference in their entirety.

Claims

CLAIMS What is claimed is:

1. A breast implant having a shell failure detection mechanism comprising a filler material that is surrounded by a pair of concentric shells which have a vacuum between them.

2. A breast implant with shell failure detection comprising:

an outer shell; and

an inner shell bonded in a vacuum to said outer shell to form a cavity;

a vacuum relief indicator, placed between said inner and said outer shells; and filler material contained within said inner shell.

3. The implant of claim 2 where a state of the vacuum relief indicator is observable via non-invasive imaging devices.

4. The implant of claim 2 where a state of the vacuum relief indicator is determined using radio frequency signals.

5. The implant of claim 2 where a state of the vacuum relief indicator is determined during a manual examination.

6. The implant of claim 2 where the filler material is contained in the inner shell and in a cavity defined between the inner and outer shells.

7. The implant of claim 2 where an inside surface of the outer shell or an outside surface of the inner shell defines a texture or pattern.

8. The implant of claim 2 where a negative pressure in the cavity is sustained by a vacuum relief indicator spring.

9. The implant of claim 8 where the negative pressure draws silicone gel into the implant while the vacuum relief indicator spring has not become fully uncompressed.

10. The implant of claim 8 where the negative pressure stops silicone gel from

bleeding through the outer shell while the vacuum relief indicator spring has not become fully uncompressed.

11. The implant of claim 2 wherein the vacuum relief indicator comprises a first surface and a second surface apposed to the first surface with a biasing member secured therebetween, wherein the biasing member is configured to urge the first and second surfaces away from one another.

12. The implant of claim 1 1 wherein the vacuum relief indicator has a first compressed configuration which is maintained when the relief indicator is under a vacuum seal and a second expanded configuration where the first and second surfaces are urged away from one another when the vacuum seal is broken.

13. The implant of claim 11 wherein the first or second surfaces are radiologically opaque.

14. The implant of claim 2 further comprising a mandrel upon which the outer shell and inner shell are moldable upon.

15. The implant of claim 2 where an outer surface of the inner shell is roughened.

16. The implant of claim 2 further comprising a dissolvable bond inhibitor material between the outer shell and inner shell, wherein the bond inhibitor material inhibits adherence between the respective shells.

17. A breast implant with shell failure detection comprising:

an outer shell; and

a pair of inner shells bonded in a vacuum to form a cavity; and

a vacuum relief indicator, placed between the pair of inner shells; and filler material contained within the inner most shell and in the region inside the outer shell and the pair of inner shells.