Background Art Mammary implant prostheses have been used for reconstructing the surgically sectioned breasts due to breast cancer, external injuries or for augmenting breasts for cosmetic surgery. Typical example of such mammary implant prosthesis is a resilient and completely sealed silicon shell or bag or pouch filled with silicon gel, and this type of completely sealed silicon shell has been used for an extended period of time as an ideal material for an implantable artificial prosthesis.

However, when such prosthesis material is used for a prolonged period of time, the gel, with which the silicon shell is filled, escaped from the completely sealed silicon shell when the silicon shell is ruptured, and the escaped gel has been proven to be harmful to human body, thereby the US Food and Drug Administration (FDA) banned the use of such devices. Therefore, in place of the silicon gel as a"filler"for the completely sealed silicon shell or bag or pouch, a new filler material in liquid form which is harmless to human body has been developed. A typical example of such liquid filler material is polysaccharide in liquid form and saline solution for injecting into a silicon shell or bag or pouch.

However, when the polysaccharide in liquid form is used, the shape of the silicon shell at the time of the initial stage of the surgery can not be maintained because

the liquid is penetrated into the inside of the silicon shell or bag due to the osmotic pressure through the silicon shell, and eventually the silicon shell is ruptured, and this created a problem. On the other hand, saline solution is still being used as a filler material, even today, but after a long period of use of the silicon shell, it is eventually ruptured, and also this material gives unsatisfactory results from the view point of morphology and natural touch.

First, the cause of the rupture of a shell is primarily due to the physical changes to the silicon shell coming from the frictional force exerted on the part of rumples or bend on the shell and the differential modulus, when the recipient of a mammary implant prosthesis is active for an extended period of time. On the other hand, the problems arising from morphology are that when the recipient of an implantable artificial breast silicon shell is in a lying down position, the artificial breast does not change pliable and maintain a natural shape conforming to the changes of the surrounding tissues, and that when the recipient is in a standing position, the saline inside the silicon shell is shifted to the lower part of the shell due to the fact that the specific gravity of the saline is higher than the specific gravity of the tissues in the nearby surrounding area, thereby such down-shifting of the saline causes wrinkling in the upper part of the silicon shell and also a slight collapse of the shell, eventually resulting in a cosmetic damage on the breast. Furthermore, as described previously, the wrinkling in the upper part of the silicon shell causes continuous and sustained rubbing action with the skin of the breast as well as the soft tissues in the surrounding area, eventually leading into inflammation in the tissue and possibly a puncture in the shell.

Such disastrous result occurs more frequently to the recipients of cosmetically reconstructive breast surgeries than those received a medically necessary surgery. Also, as aforementioned, the feelings of unnatural sloshing or rolling motion of the filler material inside of the shell as well as the senses of the existence of the foreign material coming from such movement when the recipient moves around is primarily due to the

fact that the specific gravity of the saline solution is higher than the specific gravity of the natural breast tissue and also the corresponding viscosity is lower instead. Such slight mismatches are the causes of difference in the feelings in touching of an artificial breast and the natural one.

In order to remedy the deficiencies described above, a variety of methods have been disclosed, among which several methods are briefly described below.

Tiffany, J. S. et al. disclosed in US 4,731, 081, "RUPTURE-RESISTANT PROSTHESIS WITH CREASABLE SHELL AND METHOD OF FORMING SAME", a new method of using the saline solution containing lubricious material of from 5 to 10 weight % instead of using pure saline, assuming that the primary cause of the rupture of a shell is the friction exerted on the part of the rumples and bend on the shell. This method reduces the risk of getting the shell ruptured, but such method did not solve the problems arising from the use of pure saline and the filler material such as morphological and unsatisfactory feel and sense in touching the breast.

Carlisle, D. A. , et al. disclosed in US 5,480, 430, "SHAPE-RETAINING SHELL FOR A FLUID FILLED PROSTHESIS", a newly shaped prosthesis material that has a shallow depth in the upper part of the inside of the shell, therefore, less volume in the upper half, and deeper in depth in the lower part of the interior shell, therefore, more volume in the lower half, and also that the thickness of the shell material in the upper part is at least twice as thick than the thickness in the lower part of the shell material, in order to provide an artificial breast appearing closer to a natural breast and also to reduce the risk of getting the shell ruptured. However, such structure did not solve the problems of morphological and unsatisfactory feel and sense in touching the breast caused by the use of saline solution and the filler in the inside of the shell.

Waybright, R. S. et al. disclosed in US 5,549, 671, "ADJUNCTIVE FILLER MATERIAL FOR FLUID-FILLED PROSTHESIS", a mammary artificial prosthesis shell filled with a new filler material consisting of porous silicon particles varying from 7/32 inch to 1/2 inch in inside diameter. Such filler material proposed here reduces the formation of rumples or sagging when the shell is filled with the filler material together with saline solution and also gives better feel and sense in touching the breast, but during the surgery a larger opening is necessary or a special procedure or provisions for inserting the silicon particles into the inner part of the shell causing difficulty in performing the surgery, and the problem of certain degree of unsatisfactory feel and sense in touching due to the use of many solid particles still remains unsolved. Also, since the solid silicon particles continuously rub the interior wall of the shell, rather high risk of rupturing the shell still exists.

The problems caused by the use of existing filler materials together with the use of saline solution still remain unsolved, that is, the reduction of the risk of damage caused by the filler material when the shell is ruptured, and much improved level of satisfaction in morphological look as well as the feel and sense in touching the breast.

Development of such filler material is highly desirable, for which this invention provides a solution.

Detailed Description of the Invention The primary objective of the present invention is to disclose a new filler material to fill silicon shells to form mammary implant prostheses that remedy the problems described in the Background Art Section, that is, to provide a new filler material that significantly reduces the risk of rupturing the silicon shells to be used as artificial breasts. Another object of the present invention is to provide an implantable artificial breast silicon shell filled with saline solution together with the new filler material, which silicon shell is safer to use than a shell filled with conventional gel. Yet, another object of the present invention is to provide mammary implant prostheses that

maintains more natural shape of a breast, when implanted into a female's body, and gives more realistic feel and sense in touching similar in touching a natural breast.

According to the present invention, the artificial breast shaped similar to a female's natural breast is made of resilient silicon shell which is completely sealed, hollow inside and filled with polyvinylalcohol (PVA) that expands inside the silicon shell when the PVA material absorbs the liquid state solvent injected into the shell. Here, the PVA material is simply inserted into the inside of the shell or coated on the inside wall of the silicon shell.

According to the present invention, a preferred solvent for dissolving or binding the filler material is saline solution, a solvent, and known chemical composites, chemical compounds or high polymers that have been proven to be harmless to human body may be added to saline.

Basic construction and the material of the silicon shell itself used for structuring the implantable artificial breast silicon shell disclosed here according to the present invention is the same or similar to conventional commercially available silicon shell. The silicon shell is equipped with one or more opening and closing holes through which the filler material and the solvent are transported into the shell, after which the opening hole is closed seal-tight automatically so that the contents inside of the silicon shell do not normally leak. Such opening and closing mechanism is well known and is not described here.

After making an incision in the breast area where a surgery is required, an implantable artificial breast silicon shell pre-filled with PVA material structured according to the present invention is inserted through the opening made by incision and placed inside properly, after which saline solution is injected through the aforementioned opening and closing hole. The PVA material then absorbs the saline solution and expands in the inside of the silicon shell. When the PVA expands fully,

the silicon shell is shaped to look very similar to a natural breast according to the design of the silicon shell structure. The degree of the expansion of the PVA material is confined by the amount of the PVA material, the volume of the hollow space inside of the silicon shell and the elasticity of the silicon material according to the design of the silicon shell structure. Ideally, the shape of the artificial breast would become very similar to a female's natural breast.

According to the present invention, the characteristics of the implantable artificial breast silicon shell is that the recipient of an artificial breast silicon shell filled with PVA material when fully expanded and stabilized as designed should feel and sense in touching as almost a natural breast, and also the artificial breast should maintain a shape of a natural breast regardless of her body posture or position. This is because the PVA material when absorbed saline solution which are harmless for human body remains inside the shell in the state of gel-like that has a characteristics of proper level of resilience and firmness. In addition, the PVA material expanded to its full extent by absorbing the solvent saline solution and stabilized inside the silicon shell prevents the shell from being wrinkled or rumpled, resulting in protecting the shell from being folded, thereby the rupturing phenomenon of the shell due to friction is prevented.

Furthermore, it has an advantage that the saline solution does not readily leak even if the shell is ruptured. This characteristics is due to the physical property of the fully expanded PVA material filling the silicon shell when saline solution is injected into the completely sealed silicon shell or pouch. The concept of using PVA and saline solution in a silicon shell or pouch as a new material for structuring mammary implant prostheses is a new and noble approach disclosed here according to the present invention.

The PVA material, saline solution and the silicon material which are used for structuring a new kind of mammary implant prostheses, are known to be harmless

materials to human body, and each material is biocompatible each other. It is known that the existence of such substances in the human body does not cause any side effects.

The silicon shells or pouches, according to the present invention, can have many types and shapes. For example,"symmetrically half-spherical shape"which is a radially symmetrically structured shell and"anatomically natural-looking shape"which is shallow in depth in the upper half of the shell with small volume and deep in the lower half of the shell with large volume. Among them, the anatomically natural- looking shape is preferred, but as in the conventional shell, when only saline solution is used for filling the shell, there exists a difficulty in maintaining the originally intended shape of the shell because the saline solution has higher specific gravity than the natural breast tissues, thereby the lower half of the shell has a tendency of sagging downwards and therefore, it is difficult to maintain the originally expanded shape of the silicon shell.

On the other hand, the symmetrically spherical shape has an advantage of maintaining a natural-looking breast shape because of the downward shifting helps shaping the shell look similar to a natural looking breast, but as described previously, the upper part of the shell become wrinkled or rumpled, thereby the shell is easily ruptured.

Nevertheless, the silicon shells filled with PVA material and saline solution maintain their original shape, because the fully expanded PVA after absorbing saline solution lowers the specific gravity of the saline solution and the contact boundary between the silicon shell and the expanded PVA material helps the shell maintain its original shapes.

Silicon shells can be made in many different ways. First example is the"blow form method", whereby air is blown into the form carved in the shape of a female breast containing an appropriate silicon parison, thereby a silicon shell hollow inside and completely sealed is made. Second example is the"dipping method", whereby a mandrel shaped as a breast is dipped into a silicon solution, and repeat this process in order to attain desired thickness and then it is"harden"in order to transform it into a soft rubber-like shell. Again, the final product is a silicon shell hollow inside and

completely sealed. Third method is"casting method", whereby an appropriate amount of silicon parison is pushed into the space between the form used in the"blow form method"of the first example above and the matching form used in the"dipping method"described in the second example above. Once the shell is formed it is "hardened"to create a rubber-like soft shell. The final product is again a silicon shell hollow inside and completely sealed. These methods are widely recognized manufacturing processes in this industry.

The expandable filler material by absorbing saline solution, polyvinylalcohol (PVA), is a powdery substance that expands after absorbing saline solution. The PVA can be simply inserted into the hollow space inside the sealed shell or pouch, or it can be coated or applied on the inside wall of the shell. The silicon shells containing PVA material inserted into the hollow space onside the shell by means of these methods can be implanted as artificial breasts. The level of filling, coating or a combination of both is determined by the degree of expansion of the PVA material after absorbing the saline solution injected into the hollow space inside of the silicon shell, and the degree of expansion of the PVA material is dependent upon the property of cross-linking between the micro-particles and molecules of the PVA material. The PVA material is basically water soluble or hydrophilic, and maintains its water solubility and at the same time exhibits solid phase by mutually cross-linking part of alcohl radicals or a secondary link, that is stringed to the main link or the primary link. The cross-linking reaction takes place by the secondary or additional reaction of the aldehyde compounds.

Therefore, according to the present invention, the optimum cross-linking is determined by the specific gravity of the PVA material with the saline solution fully absorbed as well as the resulting feel and sense in touching that give the closest feel and sense in touching of the natural breast, that is, about 0. 8g/cm3. Accordingly, according to the present invention, the optimum cross-linking is determined by finding comfortably acceptable level of sustained outer surface condition of the silicon shell

when the PVA material after absorbing the injected saline solution is fully expanded under various conditions of simple filling, coating, or simple filling and coating, and such optimum conditions including the optimum amounts of the saline solution for each case can be found experimentally.

According to the present invention, the PVA materials to be used as filler materials for the silicon shells are preferably in the solid state such as powder, chips, particles, polygons. The size is not specifically limited, but the powdered material is preferred simply for the reason of ease of insertion into the silicon shell.

According to the present invention, the nano-scaled or nanostructured particles of the PVA materials such as nanotubes, nanocoils and nanostrings can be used as the PVA-based filler materials primarily because they are much smaller particles compared to the conventional powdery PVA materials, thereby they are much softer and resilient and better suited as the filler materials.

There are many different ways of inserting the PVA particles into the hollow space inside the silicon shell. According to the present invention, after a silicon shell is made, the PVA material can be inserted into the shell through the opening and closing hole or the PVA material can be placed inside the silicon shell during the silicon shell manufacturing process. Silicon is a resilient material, thereby relatively large size of the PVA material can be inserted into the shell. Such insertion process of the PVA into the silicon shell can be performed by using a special equipment after the silicon shell is placed through the incision during the surgery. According to the present invention, after the silicon shell is inserted into the body through the incision made for surgery, the pre- mixed material of the PVA and the saline solution is injected into the silicon shell by using a specially prepared supply tube, before the pre-mixed material of the PVA and the saline solution is fully expanded.

According to the present invention, the PVA material can be composed in such a way that the state of the expandable PVA varies with the pressure and place it inside the shell. For example, the PVA material can be composed and adjusted so that the expanded PVA material maintains a liquid state at high pressure and at low pressure such as atmospheric pressure the expanded material changes into a solid state, and then such PVA material can be easily inserted into the silicon shell.

According to the present invention, the syndiotactic PVA can also be used.

According to the present invention, a pre-prepared PVA material can be made and tuned in such a way that the PVA material is injected into the silicon shell using a specially designed one way valve tube and connected to the silicon shell, and when the temperature of the filler, the expanded PVA material after absorbing the saline solution, reaches the body temperature, the specific gravity and the viscosity of the filler are changed close to those of breast tissue.

According to the present invention, the coating of the PVA material can be spread over the entire interior area of the silicon shell or over a part of the interior wall, but preferably a thicker layer over the upper part of the interior of the silicon shell and a relatively thinner layer over the lower part of the interior of the silicon shell in reference to the radial center of the mammary implant prostheses. This is because when the female person is in the standing position the breast is shifted downwards, thereby the amount of the saline solution absorbed by the PVA material is increased by increasing the thickness of the coating layer of the PVA material on the inside wall if the silicon shell. However, the delivery and coating methods are not limited to those described above.

There are numerous ways of coating the PVA on the interior wall of the silicon shell. According to the present invention, the interior wall of the silicon wall can be coated by making a cross-linked PVA in a similar shape to the silicon shell and

submerge it into a silicon solution and then harden it, and repeat it until a silicon shell with a desired thickness is obtained. Another aspect of the present invention, a pre- fabricated silicon shell is coated with a PVA liquid material, and then the PVA material is cross-linked, and eventually a PVA coated interior wall is formed.

According to another aspect of the present invention, the expandable filler material PVA to be inserted into the silicon shell can be made in a specifically shaped structure by design instead of in the form of powdery particles or coating. More specifically, a part or in its entirety of the expandable filler material PVA is shaped to conform to the contour of the inner wall of the silicon shell, and then they can be inserted into the pre-fabricated silicon shell or they can be placed inside of the silicon shell before the outer shell is fabricated, thereby the structured expandable filler made of PVA material or its composites is placed inside the silicon shell when the fabrication of the silicon shell is completed.

Brief Descriptions of the Drawings Fig. 1 is a cross-sectional drawing of a conventional silicon shell structure of an implantable artificial breast of a symmetrical half-spherical shape before and after filled with saline solution.

Fig. 2A is a cross-sectional drawing of an exemplary silicon shell structure of an implantable artificial breast of a symmetrical half-spherical shape filled with the PVA particles (with an injection device attached) according to the present invention.

Fig. 2B is a cross-sectional drawing of an exemplary silicon shell structure of an implantable artificial breast of a symmetrical half-spherical shape filled with the PVA particles expanded after a saline solution is injected into.

Fig. 3 is a cross-sectional drawing of an exemplary silicon shell structure of an

implantable artificial breast of an anatomically natural breast-like shape according to the present invention.

Fig. 4A is a cross-sectional drawing of an exemplary silicon shell structure of an implantable artificial breast of a natural-looking shape as shown in Fig. 3 with PVA coat inside the silicon shell according to the present invention.

Fig. 4B is a cross-sectional drawing of an exemplary silicon shell structure of an implantable artificial breast of a natural-looking shape as shown in Fig. 3 with PVA coat inside the silicon shell and a saline solution injected into the shall, thereby the PVA is fully expanded for shaping.

Fig. 5 is a cross-sectional drawing of another exemplary silicon shell structure of an implantable artificial breast of a symmetrical half-spherical shape filled with an expandable PVA material according to another aspect of the present invention.

Best Modes for Carrying Out the Present Invention In the following, the best modes embodying the principles and basic ideas of the present invention are described in detail in reference with the figures. However, the principles, basic ideas and realizations of these are not limited to those presented here. Those who are familiar in the art should be able to readily generate variations of the principles, basic ideas and realizations presented here.

In order to provide a smooth transition from prior art to the basic flow of the principles behind the present invention, a typical prior art of an implantable artificial breast structured with a silicon shell is described in detail in the following.

In Fig. 1 is a cross-sectional drawing of a typical silicon shell 110 of a symmetrical half-spherical shape filled with saline solution 200 designed as an implantable artificial breast 100. The implantable artificial breast 100 is structured with a shell 110 made of a resilient material such as silicon, and the shell 110 is equipped with an opening-and-closing hole 120 through which the saline solution 200 is injected

into the shell 110. The opening-and-closing hole 120 is consists of the main body 122 which is an integral part of the shell 110, feeding orifice 124 that passes through the exterior and the interior of the shell 110, and a flexible stopping cover 126 that covers the outer opening area of the feeding orifice 124.

When the shell 110 is not filled with saline solution, the shell 110 is in a collapsed state as shown in dotted lines, and the shape of the shell changes to a fully expanded shape of a breast 110 (shown as solid lines) as the shell is filled with saline solution 200 by injection through the feeding orifice 124 using a special device (not shown). Since the artificial breast 100 is made of a resilient material, the prosthesis can be folded and inserted into the space behind the breast through a small opening made by incision during surgery. Conventional prosthesis 100 is shifted downward B due to the heavy weight of the saline solution 200 itself, thereby the lower part B of the shell 110 becomes more inflated than the upper part A of the shell 110. As a result, the top peak part P in the upper part A of the shell 110has a tendency of being rumpled or even folded, and the surrounding skin of the breast (not shown) is wrinkled, thereby the cosmetic look of the surrounding area of the skin of the breast is the undesirable result, and furthermore, the bent or folded top peak part P is at the risk of being ruptured after a prolonged use. Also, the low viscosity of the saline solution 200 has a tendency of causing the feel and sense of sloshing and rolling as it moves around more than desired inside of the artificial prosthesis 100 as the recipient of the artificial breast 100 makes moving motions.

Embodiment 1 Referring to Fig. 2A, the shell 310 of the implantable artificial breast 300 prior to the injected of saline solution is in the collapsed state 310, and the hollow space inside of the shell 310 made of a soft and resilient silicon material is filled with polyvinylalcohol (PVA) particles 320. The PVA particles 320 are a mixture of various sizes in diameter, and can be placed inside the shell 310 during the process of fabrication of the shell 310. In Fig. 2A, it appears that the PVA particles are evenly spread inside the shell 310, but this is not necessarily the case.

As in Fig. 2B, when a saline solution 200 is injected into the interior of the

shell 310 through the supply tube 400 by means of the injection device 500, to which one end of the supply tube 400 is connected, after the other end of the supply tube 400 is connected to the feeding orifice 324 in the opening-and-closing hole 330. The PVA particles 320 inside the shell 310 absorb the saline solution, and expand to their full extent, and as a result the shape of the silicon shell 310 becomes similar to a natural breast. The degree of the expansion of the PVA particles is dependent upon the cross- linking property of the PVA material used. For example, it expands from 3 times to as high as 20 times. The expanded PVA particles 340 determine the shape of the shell 310 (expanded), but the shape might change slightly due to the settling effect between the PVA particles. Therefore, small pockets of saline solution only may present within the shell with the expanded PVA material depending upon the degree of the absorption of saline solution by the PVA material and the degree of cross-linking of the PVA material, and sometimes such small pockets of saline solution only may not present.

Embodiment 2 The implantable artificial breast 302 shown in Fig. 3 is a silicon shell 312 shaped anatomically similar to the shape of a natural breast and it differs from Figs. 2A and 2B from the point of view that the expandable PVA material 322 is a layer coated inside wall of a shell 302 instead of the form of particles as in Figs. 2A and 2B. The thickness of the layer of the PVA material 322 can be uniform or thick at the upper part and thin at the lower part of the shell 312 as illustrated in Fig. 3. Furthermore, the PVA material can be partially coated on the inside wall of the shell 312. Remaining structures and functions are about the same as Embodiment 1.

Embodiment 3 The implantable artificial breast 304 shown in Figs. 4A and 4B differs from Embodiments 1 and 2, in that this Embodiment contains both particle type of PVA 320 and the coated layer type of PVA 322. When a saline solution 200 is injected into the shell 314 in Fig. 3, both particle type 320 and coated layer type 322 of the PVA expand and the shape of the silicon shell 314 changes to anatomically similar shape to a natural

breast. As afore-described, the expanded PVA particles 320 do not necessarily maintain the shape similar to the one shown in Fig. 4B, that is, the expanded particle PVA 320 and the expanded coated layer PVA 322 may be changed at the boundary and fill the hollow inside space of the silicon shell 314.

Embodiment 4 The implantable artificial breast 306 shown in Fig. 5 is different from the previous Embodiments 300,302, 304, in that the silicon shell 316 in that the expandable PVA material 326 is formed in a shape of a partially half sphere. Use of such expandable PVA material 322 shaped as a partially half sphere is advantageous over other types because the size of this PVA material 322 is relatively small when a saline solution is not injected yet, thereby such small volume artificial breast can be readily inserted into a small incision made for the surgery. The expanded shape of the silicon shell 316 after a saline solution is injected is shown in dotted lines in Fig. 5.

The embodiments described above are not intended to limit the scope of the principles, basic ideas and realizations of the present invention, and those who are familiar in the art should readily derive different variations of the underlying principles, basic ideas and realizations of the intended purposes of the present invention.

Industrial Applicability The implantable artificial breast silicon shells disclosed here according to the present invention, improve the quality of conventional mammary implant prostheses significantly. New filler material PVA disclosed here is a significant step towards the perfection of the existing mammary implant prostheses and will solve many difficult problems for both breast surgery-related patients as well as those who desire cosmetic surgery for breast reshaping or enlargements.