Patent Grant
12042458
This application relates to external vacuum expanders, and, more particularly, to external vacuum expanders with rims that reduce shear stress.
It is a well-established biologic phenomenon that sustained gentle tension is a natural stimulus for tissue growth. We grow during childhood thanks to the tension generated by the epiphyseal growth plate that lengthens our bones. Internal inflatable tissue expanders and Ilizarov bone distractors are examples of widely used medical devices that enlarge tissues based upon this principle. These medical devices, however, require complication-prone invasive surgical procedures. There is therefore a societal need for distraction devices that are external and non-invasive while still capable of enlarging tissue in a safe, practical, and user-friendly manner.
Cosmetic breast augmentation and post mastectomy breast reconstruction are the two conditions where such a non-invasive method of tissue enlargement might find its most common application. Dating back to the 1800's, a very large number of vacuum based breast enlargement devices have tried to achieve this goal. While some have been marketed over the years, they are essentially all considered novelty items and none have ever proven their efficacy in scientific clinical studies because none could be consistently applied for the prolonged period of time required to induce substantial tissue growth.
The Brava device conceived and designed by the inventor of the present invention, disclosed in U.S. Patents such as U.S. Pat. Nos. 6,641,527, 6,500,112, 6,478,656, 5,676,634, 5,695,445, 5,662,583, is the only device known to the inventor with scientifically proven efficacy reviewed by the FDA. The Brava device was successful in inducing permanent tissue growth because the inventor identified the biomechanical constraints involved in maintaining a vacuum over the breast for a prolonged period of time and applied biomedical engineering principles to solve these constraints. While a substantial improvement over the prior art, the Brava device has not replaced breast implants because patient compliance remains a major hurdle. The Brava device is impractical and difficult to use all day, every day for the number of months required to achieve substantial tissue growth. In addition to being bulky and cumbersome, the Brava device also has a few other limitations which have yet to be successfully addressed in its over 25 years of use. Thus, the present inventor has recognized the need for improvement of the Brava device.
There are a number of challenges associated with maintaining vacuum to induce a distractive force over the breast in a sustained fashion over a prolonged period of time to achieve breast enlargement. These three challenges are:
The inventor's prior Brava device attempted to solve challenge #1 with a soft silicone gel bladder that conformed to the complex contour of the chest wall and absorbed, to a certain extent, the varying surface topography associated with normal activity. To avoid air leaks, the sole of that bladder included an adhesive layer that sealed it with the skin. However, that adhesive layer tended to wear out with daily use. Once the adhesive layer deteriorated, air leaks occurred, thus, the Brava device only provided a short term solution to the air leak challenge.
Realizing that an external pressure above 20 mmHg occludes capillary circulation (20 mmHg is the highest pressure that can be safely tolerated under the rim on a prolonged basis as described in U.S. Pat. No. 6,500,112), the Brava device attempted to solve balancing the counterforce (challenge #2) by having the surface contact area of the rim being equal to the surface area of the dome aperture where the vacuum pressure is exerted.
The Brava device attempted to solve the shear stress problem challenge (challenge #3) by providing a contact rim that dissipates the shear by recruiting inward some peripheral skin. The larger the aperture, and therefore the amount of tissue under tension, the larger the shear stress.
Shear Stress=τ=Force/Shear Area
Assuming that the Force=Pressure×Surface Area
Approximating the aperture to a circle, the Surface Area S=πR2
Force=Pressure×πR2
Shear Area=Circumference (2πR)×Thickness of tissue (Thickness)
Shear Stress=τ=Force/Shear Area=P×πR2/(2πR×T)=Pressure×R/Thickness
This is why smaller suction cups, nipple expanders and lactation devices (3-6 cm max.) have little need to address this problem. The skin at the periphery of the breast (at least 10-12 cm aperture diameter) that is anchored down by a rigid rim is under a significant amount of lateral inward stress. Prior to the Brava device, none of the prior art addressed this issue and this might be the reason why none of these devices was ever adopted by the medical community. Since the gel rim of the Brava device has an adhesive sole, to recruit the amount of skin necessary to dissipate the shear stress, the gel rim that is adherent to the skin has to significantly deflect. This proved to be the most difficult issue to solve. For the deflection arc to deliver the required amount of inward recruitment, the gel rim had to be at least 4-5 cm high. It also had to be very compliant, offering little resistance to inward roll. This added bulk, height, weight, and premature wear of the constantly deflecting silicone gel bladder.
None of the over 50 prior art breast enlargement patented devices have features that address the foregoing issues/challenges. In fact, none except the Brava device addresses the counterforce and the shear force, however, even the Brava device has some challenges.
Although suction cups sometimes have rubber rims, the rubber used does not meet the specific durometer and elasticity requirement, and they lack the necessary configuration to meet the counterforce/shear force challenges. Furthermore, they lack sufficient concavity and width. Suction cups are also very different from breast enlargement devices. Their shear stress is minimal compared to breast enlargement devices that are an order of magnitude larger in size. Furthermore, most suction cups are passive as they typically do not have an external vacuum pump—their source of vacuum is the recoil force of the rubber rim itself. Additionally, suction cups are often made of natural rubber which has a high incidence of allergy so are of limited use in medical devices.
U.S. Pat. No. 10,603,161 discloses apparatus and methods for nipple and breast formation. The apparatus uses adhesion to hold the mold in place. The design of the rim does not taper down and lacks sufficient concavity. The devices of the '161 patent have no way of dissipating the larger shear forces that would cause skin blistering. The breast has a larger surface area than the nipple, so the deformation is larger and the force on the perimeter is higher for the same amount of pressure. The amount that the skin needs to stretch (strain) for the nipple is minimal compared to the breast therefore the shear force is also less for the nipple.
U.S. Pat. No. 10,433,947 (same inventor as the inventor of the present invention), discloses methods and devices for tissue expansion. The patent describes a splint that holds a swollen/pre-expanded breast in place as an alternative to expanding with an external vacuum. It states, “Another way of mechanically coupling the splint to the skin is surface tension. Surface tension is the naturally occurring means by which the body holds together tissues that need to remain mechanically coupled but yet glide and avoid shear forces. This is how the expanding rib cage transmits the mechanical force of inhalation to the soft sponge like lungs to expand and this is how bowel loops can glide past another while held together too.” However, surface tension is being used here to apply the tensile expansion force on the tissues as an alternative to the glue to replace the need for vacuum or traditional sticky adhesives.
U.S. Pat. No. 5,676,634 (same inventor as the inventor of the present invention) discloses a method and apparatus for soft tissue enlargement with balanced force. The patent discuses a rim with a surface area sized to prevent excessive contact pressure to the skin. The patent does not address shear.
U.S. Pat. No. 6,500,112 (same inventor as the inventor of the present invention) discloses a vacuum dome with a supporting rim and rim cushion. This patent describes minimizing shear force by providing an interface between the dome and the skin which allows inward displacement of the contact surface. This reduces the strain dL/L on the skin. dL is the same but L is larger. The contact surface is no longer anchored by a rigid dome, the flexible interface allows the skin to move more freely with lower strain, lower stress, and lower shear force. However, this device still does not fully meet the challenges enumerated above.
U.S. Pat. No. 9,498,565 discloses lactation devices. Embodiments of the device disclosed include a bra-insert to hold the device in place. Some embodiments include shoulder and torso harnesses, or other strapping fabrics and mechanisms to hold the device in place to allow for hands-free expression. In addition, adhesive fabrics, such as Geckskin™ (University of Massachusetts-Amherst, Amherst, Mass.), to leverage Van der Waals forces on the anterior surfaces of the soft structure 1 of
As can be appreciated, the foregoing prior art devices fail to address the drawbacks/challenges enumerated above, and some do not even recognize the importance of, or are not concerned with, shear forces. Therefore, the needs exists for a vacuum expander for tissue expansion that can effectively prevent air leaks to preserve the vacuum, prevent excessive pressure that would collapse capillary circulation and reduce the shear stresses that develop at the junction of the skin. The devices should also be comfortable to wear for extended periods and minimize skin irritation and blistering as well as be concealable and wearable as comfortably as a regular padded bra. Such devices could improve breast expansion/augmentation and well as expansion/augmentation of other body tissue. Furthermore, such devices could also be used for breast reconstruction.
The present invention solves the problems and deficiencies of the prior art. The present invention provides a comfortably wearable dome (or other shaped) device with a specialized rim (skirt) which contacts the body tissue and utilizes vacuum for tissue expansion, e.g., expansion of breast tissue. The expander devices of the present invention, also referred to herein as vacuum expanders or tissue expanders, effectively 1) preserve the vacuum by preventing air leaks; 2) balance the distractive force applied to the breast with the counter-force exerted by the rim of the external vacuum expander in contact with the surrounding skin to prevent excessive pressure that would collapse capillary circulation and lead to pressure ulcerations; and 3) reduce the shear stresses that develops at the junction between the tensed skin inside the vacuum shell with the skin firmly held down and anchored by the inner lip of the rim to reduce skin irritation, blistering and ulceration which is caused by excess shear forces concentrated at the inner lip of the rim.
It should be appreciated that the devices of the present invention could successfully, with minimal trauma, effect breast expansion/augmentation and well as expansion of other body tissue.
To maintain an air-tight seal, i.e., preserve the vacuum, the devices of the present invention replace the adhesive gel bladder of the Brava device with a deeply concave, wide, tapered, soft rubber skirt that deflects to open and spread out under the effect of the downward vacuum force. This increases the surface contact area and improves the seal. Furthermore, the concave configuration of the rim skirt forces its feathered-out periphery to grip down and espouse the surface contour of the torso to maintain the air-tight seal. This deflective conforming soft rubber skirt can also accommodate a significant amount of body motion without losing the vacuum seal.
The devices of the present invention also effectively balance the distractive and counterforces. Increasing the vacuum pressure causes the concave flexible rubber rim of the device rim to deflect out and widen to increase the surface contact thereby reducing the counter-pressure on the skin, and in some embodiments widen to flatten or substantially flatten. This property of the concave tapered deflecting rubber rim (sole) that increases surface contact with increases in the downward force balances the forces to keep the skin pressure below damaging levels.
The devices of the present invention completely solve the shear stress problem. Because the soft rubber rim maintains a vacuum seal by faithfully espousing the body contour, there is no need for an adhesive layer. Quite the contrary, the device works best when there is a lubricant to provide near friction free gliding between the skin and the rubber rim (skirt) that opens to wrap around the body. With the contact surface no longer glued and anchored to the rim, the skin is free to move, and the tension can recruit as much peripheral skin as necessary to dissipate the damaging shear stress. With this near free tissue recruitment there is lower strain, lower force and lower shear stress. Thus, the vacuum expanders of the present invention solve the shear stress problem by operating in a manner opposite to that of the prior art. The prior art devices focused on securement of the rim position by use of adhesive; the present invention actually “unlocks” the rim and encourages movement/sliding (gliding) of the rim. Thus, the non-adhesive (e.g., lubricated) interface of the rim of the present invention allows it to spread out under the effect of vacuum to increase its contact surface and reduce pressure and to freely recruit peripheral tissue to nullify shear forces.
In accordance with one aspect of the present invention, a tissue expander is provided comprising a shell, an opening in the shell in communication with an external vacuum source to apply a vacuum within the shell and impart a distracting force to expand tissue, and a rim connected to the shell and adapted to be in contact with a skin of a patient. The rim is non-fixedly attached to the skin of the patient and moves laterally outwardly with respect to the shell under application of the vacuum.
In some embodiments, the shell is in the shape of a dome.
In some embodiments, the rim is composed of rubber and has a lubricating layer on a bottom surface to glide over the skin, thereby reducing shear stress between the rim and contact surface of the skin. In other embodiments, the rim has a lubricant to provide reduced friction contact with the skin to allow sliding of the rim and reduce shear forces. In preferred embodiments, the rim is composed of a synthetic rubber and is of low durometer.
In preferred embodiments, the rim has a non-adherent, non-adhesive lower tissue contact surface.
In some embodiments, the rim has a concave tapered portion that forms a skirt that deflects to open and spreads out laterally (widens). In preferred embodiments, when downward pressure is applied by the vacuum, the rim conforms to the contour of a body of the patient and the rim deflects to increase a surface in contact with the skin and prevent an increase in counter pressure against the skin.
In some embodiments, the rim (skirt) has a feathered down periphery to wrap around a portion of the body and grip the torso. Other features/aspects that can be incorporated into some embodiments of the rims (skirts) of the present invention can include one or more of the following: a) a malleable edge thicker than a proximal portion of the rim, the edge being more deflectable than the proximal portion; b) a taper and inward camber so its axis is less than 20 degrees from the vertical; c) of asymmetric form having a narrower skirt medially and a more curved inward skirt laterally to provide a lateral side with deeper concavity and a length longer than a medial side to wrap around the body contour (better grip around the lateral torso and to prevent overlap in the midline); and/or d) a fin pocket within which thin ribs or fins of proper curvature and durometer can be inserted to help espouse the contour of the lateral torso.
In some embodiments, the rim has a connection mechanism for releasable attachment to the dome (or shell) so that the dome of a first size can be removed from the rim and a dome of a second size can be attached to the rim. In these embodiments, domes (shells) of varying sizes can be selectively connected to the rim. In other embodiments, two or more domes are permanently attached to the rim, the two or more domes being of progressively deeper sizes.
In accordance with another aspect of the present invention, a tissue expander is provided comprising a shell, an opening in the shell in communication with an external vacuum source to apply a vacuum within the shell and impart a distracting force to expand tissue and a rim connected to the shell and adapted to be in contact with a skin of a patient. The rim has a concave lower surface, the concave lower surface deforming upon the application of vacuum to deflect out from its concave condition to invert to a convex shape (condition) upon application of vacuum. That is, the segment under the rim changes from concave to convex while in some embodiments the periphery, especially the lateral side remains concave to preserve the seal.
In some embodiments, the rim has tapered surface to progressively decrease in thickness toward an outer periphery to provide a thinner more malleable edge deflectable to a larger degree than thicker portions of the rim (closer to the dome). Other features that can be incorporated into embodiments of the rims of the present invention can include one or more of a) a taper down to a feather thickness forming a feathered edge b) a lateral side of the rim is longer and has a deeper concavity than a medial side of the rim; c) an inward camber skin contacting surface angling downward from a horizontal plane to enhance gripping of the body of the patient; and/or d) an interdigitating design that allows the medial edges of both rims to overlap without leaving any air passage folds that can cause loss of vacuum. In some embodiments, the rim is composed of a low durometer rubber material. In some embodiments, the rim is composed of a varying durometer synthetic rubber material, with the periphery having a lower durometer.
In some embodiments, as downward pressure is applied, the counterforce between the rim and skin is evenly distributed over a skin contact area. In some embodiments, as vacuum pressure increases, the rim increases in deflection to widen and increase contact area with the skin and reduce counter pressure on the skin.
In accordance with another aspect of the present invention, a brassiere is provided comprising a) a first aperture; b) a second aperture; c) a first shell having a first rim extending laterally outwardly therefrom, the first aperture dimensioned and configured to receive the first shell and/or first rim, the first rim non-fixedly positionable in contact with skin of a patient; and d) a second shell having a second rim extending laterally outwardly therefrom, the second aperture dimensioned and configured to receive the second shell and/or second rim, the second rim non-fixedly positionable in contact with skin of the patient. In some embodiments, a distractive force is applied to the skin of the patient within the first and second shells and during such distractive forces the first and second rims slide laterally outwardly while maintaining contact with the skin.
In some embodiments, the rims have a concave lower surface deforming upon application of vacuum to invert to a convex surface.
In some embodiments, the distractive forces are applied by an external vacuum in communication with the shell; in other embodiments, the distractive forces are applied by elastic recoil of the shells and/or rims.
The brassiere can include a reinforcing band to connect the brassiere to the rim and/or reinforcement straps to maintain feathered peripheral edges of the rim in firm contact with the skin to ensure a vacuum seal.
In accordance with another aspect of the present invention, a method for reducing shear stress in a device for expanding tissue is provided. The method comprises positioning a device having a shell and a rim extending from the shell configured for contact with a body of the patient, the rim non-adherently positioned on the body so that upon application of a distracting force within the shell, the rim spreads laterally outwardly with respect to the shell such that shear stress is reduced at a junction between tensed skin inside the shell and skin firmly held own and anchored by the rim.
In some embodiments, the distractive force is applied by elastic recoil of the rim.
In some embodiments, the distractive force is applied by application of a vacuum within the shell. A portable vacuum pump can be provided in communication with an interior of the shell to apply the vacuum. A pressure control mechanism can be provided to control vacuum pressure within the shell. In some embodiments, the pressure control mechanism comprises a manual pump with a pressure relief valve to prevent vacuum pressure from reaching a damaging level. In some embodiments, as vacuum pressure increases, the rim increases in deflection to widen and increase contact area with the skin and reduce counter pressure on the skin.
In accordance with another aspect of the invention, a tissue expander configured to be worn by a user is provided comprising a shell, the shell having an aperture formed within the dome to receive tissue expanded by a distracting force and having a rubber skirt providing a skin (or tissue) contact surface area against a skin of the patient. The aperture defines an aperture surface area, wherein the skin contact surface area is greater than the aperture surface area, and wherein the skirt is non-fixedly attached to the skin of the patient and slides laterally outwardly.
In some embodiments, the shell is dome-shaped.
In some embodiments, the shell has an opening in communication with an external vacuum source to apply a vacuum within the shell and impart the distracting force to expand the tissue and the skirt increasingly spreads under increasing pressure. In some embodiments, the opening receives a flexible tubing connected at one end to the external vacuum source and connected at the other end to the shell.
In some embodiments, the skirt is composed of synthetic rubber and has a lubricating layer on a bottom surface to glide over the skin, thereby reducing shear stress between the skirt and contact surface of the skin. The rubber skirt is preferably of low durometer and can be for example in the Shore OO range less than 10-15 in the shore AA.
In preferred embodiments, the skirt has a non-adherent, non-adhesive lower tissue contact surface. In some embodiments, the skirt increases the skin contact surface area by at least a multiple of three as pressure increases. In some embodiments, vacuum pressure can be applied for bursts over 60 mmHg. In other embodiments, vacuum pressure can be applied continuously at 20 mmHg.
In some embodiments, the skirt under pressure deflects outwardly to increase the skin contacting surface area to approximately three times the aperture area.
In some embodiments, the increased skin contact surface area reduces the counter pressure on the skin from a pressure above 20 mmHg to a pressure about 20 mmHG.
In some embodiments, the tissue expander is attached within an aperture of a brassiere.
The tissue expanders are designed for continuous wear at predetermined pressure levels as discussed below.
The tissue expanders can be used in various methods/applications such as a) enlargement of the expansion treated tissue based on tension induced tissue growth; b) temporary stretching of the expanded tissues to generate a scaffold for grafting or injection of materials/agents; c) maintaining the pre-expanded tissue in an expanded or swollen state. These are discussed in more detail below.
So that those having ordinary skill in the art to which the subject invention appertains will more readily understand how to make and use the surgical apparatus disclosed herein, preferred embodiments thereof will be described in detail hereinbelow with reference to the drawings, wherein:
The current invention utilizes advances in materials technology such as in silicone rubber and in urethane and in other synthetic rubber materials technology to provide a solution to all three problems/challenges enumerated in the Background section above:
The solutions to each of these problems/challenges (referred to below as #1, #2 and #3) are discussed in detail below. This is achieved by a vacuum expander with a dome (shell) or other shaped device attached to a uniquely designed and configured rim (also referred to herein as a skirt) which interacts with the skin in a unique fashion and functions in ways different from prior and current vacuum expanders. Note solutions to address any one of the aforementioned three problems/challenges provide an improvement over prior and current devices so that the present invention in some embodiments can address only one or only two as well as all three of the problems/challenges.
The tissue expanders of the present invention use pressure from an external vacuum source or from recoil of its rubber rim or semi-rigid shell to impart a distracting force that can expand tissue. The device is composed of a shell (also referred to herein as a dome when dome shaped) which forms a more rigid section for the tissue to expand into and a softer rim which is in contact with the tissue to serve as an interface between the dome and tissue. The rim can have a connection mechanism, for permanent or releasable attachment to the dome. A pump, sensor and servomechanism control vacuum pressure within the dome and the pump communicates with the interior of the dome via a tube(s) from the pump extending to or into an opening in the dome. Alternatively, if the recoil of the rubber rim is used to generate the vacuum, an adjustable pressure release/relief valve can be included to prevent the accumulation of higher vacuum pressures that can be damaging to the tissues.
The prior art teaches the use of adhesive to secure the vacuum expander to the skin. However, the present inventors, after years of study, discovered that the use of adhesive caused various problems, such as those enumerated above. The inventors discovered that providing an opposite effect, that is, to allow the skin under the vacuum expander to glide or slide, rather than be adhesively secured to lock movement, actually provided significant reduction in shear stresses and significantly reduced skin damage from excessive shear forces. Thus, the expanders of the present invention developed by the inventors, which are non-fixedly/non-adhesively attached to the skin, operate in a way not contemplated, and in fact opposite to, the teachings of the prior art. The present inventors also recognized the limitations of current rim configurations and discovered unique features for the rim to improve its adaptation to the wearer's body.
The present invention provides superior results in tissue expansion via vacuum. Such tissue expansion is described below for breast expansion/augmentation, but could also be used for expansion/augmentation of other body tissue.
To maintain an air-tight seal (challenge #1) and balance the distractive force with the counterforce (challenge #2), the devices of some embodiments of the present invention replace the adhesive gel bladder of the prior art with a deeply concave, wide, tapered, soft low durometer rubber rim forming a skirt that deflects to open and spreads out under the effect of the downward vacuum force. This increases the surface contact area and improves the seal. This can be appreciated with reference to
A comparison of
Taking into account the elasticity of the rubber material, its thickness and taper angle, the mechanical properties of the rim are engineered such that by spreading and widening with increasing downward force it increases the skin contact area to maintain the surface counter pressure below damaging levels. Furthermore, the design also prevents pressure points and ensures an even pressure distribution along the contact area. That is, because the thinner more malleable edge deflects more while the thicker proximal part deflects less, a relatively constant downward force is maintained on the tissues along the width of the rim.
As shown in the Figures, the rim tapers in thickness with a maximum thickness at the top 107 (closer to the dome 104 where it is connected at region 108), e.g., approximately 1 inch, tapering to a maximum of a few millimeters for example at the periphery 109. In some embodiments, it tapers (narrows) down at region 114 (see e.g.,
The rim is also in preferred embodiments an asymmetric design (see e.g.,
The rim, with its deep concave shape, is preferably made of a low durometer synthetic rubber material such as silicone or newer formulations of urethane. Thus, it is the soft rubber that contacts the skin. With increasing pressure, the rim increases its deflection to increase the contact area and reduce the counter-pressure exerted on the skin. Furthermore, it is designed such that the applied vacuum does not cause it to buckle inward and get sucked into the dome section. (This would reduce the aperture of the expansion surface). In preferred embodiments, a low durometer (anywhere on the entire Shore OO scale), or on the low shore A scale (less than 25 Shore A, and preferably less than 15 Shore A) rubber, preferably silicone or medical grade urethane is utilized. Such materials have the required softness (close to gel like) to be comfortable and elastic rigidity to properly deflect and evenly distribute the pressure as the rim which contours to the skin surface deflects with pressure. (While there are different overlapping shore scales, it is understood that any scale used would be specifying materials of similar and crucial mechanical property as the ones mentioned above. It should also be noted that these are novel materials not widely available until recently for medical use). However, different materials, and combination of materials of different durometers, are also contemplated. The rim material is stretchy enough (very low durometer rubber) so that when pressure is applied and the downward force from the dome is counteracted by the skin, the skirt can stretch out to a flat or near flattened shape as it glides open and allows skin recruitment. Though more complicated to manufacture, it is also contemplated in alternate embodiments to have the skirt made of varying durometers along its thickness and circumference in order to reduce bulk weight and make it more comfortable and concealable, provided the concavity, the taper angle, the width and the deflection property under downward pressure preserve adequate deflection under the physiologic pressures used to evenly distribute the pressure avoiding pressure points. That is, the softer durometer material is more comfortable and conforming against the skin, but is bulkier (thicker). (In some embodiments, the softer durometer can be like a gel). The higher durometer is thinner but less comfortable. Thus, in some embodiments, the durometer can vary so it is harder adjacent the center of the dome to provide reinforcement to hold it together and softer at the periphery for comfort and conformance. In some embodiments, the variable durometer concept can be utilized so that it progressively decreases in durometer toward the periphery. In such variable durometer embodiments, the delicate balance needs to be achieved between comfort/conformance and reinforcement.
The rim/skirt design variables include durometer of the material (e.g.,) rubber, its mechanical properties, its thickness, its rate (angle) of taper, its concavity, its length and its shape, and these variables are design engineered/optimized in order to increase surface contact with increases in vacuum pressure to decrease the counter pressure on the skin—as the skirt flattens with downward pressure, the counter force between the skirt and the tissue is evenly distributed all over and around the contact area. The above variables are design engineered such that there are no concentrated pressure points, but rather a distribution, preferably an even distribution, all over the skin contact area. The taper angle and concavity are also designed to evenly distribute pressure under the spread out skirt such to avoid pressure points. With increasing pressure, the rim increases its deflection, i.e., deflects out and widens, to increase the contact area and thereby reduce the counter-pressure exerted on the skin. The design leads to a near linear relation between vacuum pressure increases and surface contact area increase. To illustrate, when the vacuum pressure doubles, the rim flattens and spreads out to double the contact surface against the skin and keep the pressure it exerts against the skin low and even all around its circumference. This property of the concave tapered deflecting rubber sole that increases surface contact with increases in the downward force balances the forces to keep the skin pressure below damaging levels.
Thus, the devices of the present invention are designed to decrease the frictional shear forces as the smooth (and lubricated in some embodiments) rim/skirt slides and deflects with minimal force (lowest durometer rubber) thereby allowing the dome to push down and the rim to slide without skin damage.
A thin feathered inner rim (feathered lip) to increase contact area and improve the seal could be provided, as illustrated in
With respect to shear stresses (challenge #3), the above vacuum expanders of the present invention completely solve the shear stress problem. The forces and shear effect can be appreciated with reference to
In the present invention, a soft rubber rim (skirt) instead of an adhesive rim is provided. The soft rubber rim maintains a vacuum seal by faithfully espousing the body contour so there is no need for an adhesive layer (or other skin-adherent layer) so the rim is thus non-fixedly/non-adherently/non-adheredly positionable on the skin of the patient to enable sliding outwardly. The device rim (skirt) can have a lubricant or other material to provide near friction free gliding between the skin and the skirt that opens to wrap around the body. With the contact surface no longer glued and anchored to the rim as in devices using adhesive (or other adherent material or structure) which fix the position of the rim and device, the skin is free to move, and the tension can recruit as much peripheral skin as necessary to dissipate the damaging shear stress. With this near free tissue recruitment there is lower strain, lower force, and lower shear stress.
Thus, the vacuum expanders of certain embodiments of the present invention have a lubricated skin-to-rim sole contact area to allow a friction free skin recruitment (and sliding/gliding) that dissipates the shear forces. The lubrication reduces shear stress between the contact surfaces of the skin and the device. In the prior art, the skin is anchored to the contact surface via high friction interfaces or more frequently via adhesives. Lubrication of the present invention takes away this anchoring and thus removes or reduces the shear force.
The lubricant or a low friction film can be applied in one or more of the following ways: a) applied to the skin before placing the device on the skin; b) applied to the bottom (lower) surface (sole) of the rim itself before placing it on the skin and/or c) be in the material of the rim so that it continually lubricates. (The bottom (lower) surface refers to the surface closer to the tissue, e.g., breast tissue, and is also referred to herein as the sole or base). The lubricant or low friction film can be added separately, or alternatively, the rim sole material can have an inherently low friction coefficient thus removing the need for lubricant or film. Thus, the device is non-adhesive/non-adherent to the skin and has a low friction smooth contact skin surface either inherent or by the addition of a lubricant or film interface. Such lubricants which can be utilized to remove or reduce the shear forces between the skin and the device contact surface (rim) include by way of example, grease, petroleum jelly, oils, waxes, KY Jelly, glycerin, hydroxyethyl cellulose, water, liquid, jell, cream, or wax of any type, an Allergen free lubricating material with excellent skin tolerance such as cocoa butter, petrolatum gel, Vaseline, Nivea, Aloe Vera, mineral oil, etc., or a combination of these.
The limited deflection under higher pressure of the adhesive rim of the prior art can be appreciated by the photographs in
Examples of the shear effect in a small and large dome (shell) of the prior art, illustrating how a larger aperture pulling on a larger surface will tend to create more inward pull and therefore more shear force concentrated at the rim that can damage the skin are depicted in
Vacuum Pressure (P) generates a downward force (F) on the skin that is a function of the aperture surface area (S) (F=P×S). That force is balanced by a counter-force against the skin. The force F in the devices of the present invention has to be gently dissipated against the skin as opposed to other suction devices that are designed to pull out and extract. Thus, the rim contact surface area needs to increase in order to diminish the pressure on the skin.
A sustained high pressure cannot be tolerated because after more than a few minutes the skin breaks down. Therefore, the soft rubber rim/skirt (sole) of the device is designed to significantly enlarge its surface contact area in order to reduce the pressure on the skin with increasing vacuum pressure. The Forces are balanced according to the following formula: F(in)=Aperture Surface area×Vacuum Pressure. This is balanced by F(out)=Skin contact Surface area×Pressure applied to the skin. According to Newton, F(in)=F(out). In devices unlike the present invention which are designed to grip and pull out, e.g., a vacuum applier for a fetus, a high pressure needs to be applied to the skin in order to grip and pull out. Therefore, the skin contact surface area has to be small compared to the aperture area. The devices of the present invention are designed for prolonged contact, e.g., several continuous hours at a time (over a span of days, weeks or months), and cannot afford high pressure against the skin. Therefore, the skin contact surface area needs to be much larger. That is, the ratio of aperture surface area to skin contact surface area needs to be greater. (A large aperture and small contact area in contrast is designed for higher gripping pressures against the skin for gripping and extraction; the devices of the present invention have a large contact area relative to the smaller aperture area). Stated another way, for a given aperture surface area and vacuum pressure, the devices of the present provide a much larger skin contact surface area.
Thus, the rubber rim/skirt of the devices disclosed herein spread out to significantly increase skin contact surface area to maintain a low pressure on the skin. Therefore, the deflecting rim significantly increases skin contact surface area with increasing vacuum pressures. (As it glides outward with minimal friction, the surface contact area increases as the vacuum pressure increases in order to minimize skin damage). To give illustrative numbers to aid understanding, in one example, the device has a dome aperture about 4.5 inches in diameter but its skirt can extend the surface contact diameter by another 4.5 inches. We calculate the resting surfaces at 3.14×2.25×2.25=15.8. Increasing the surface contact diameter by another 4.5 inches gives 3.14×4.5×4.5=63.6 square inches for an increase surface contact area of 63.6−15.8=47.8. inches. Thus, the device increases surface contact area by 47.8 sq inches. Clearly, other dimensions to increase the surface contact area are also contemplated.
The maximal tolerable pressure against the skin is 20 mmHg or about 0.4 PSI. Pressure on the skin above this level occludes the capillaries and with no blood flow for more than a few minutes causes tissue damage. The devices of the present invention function at vacuum pressures of 20 to 60 mmHg, and in some instances can function at vacuum pressures of 100 mmHG for short bursts. This means that they can function at about 3 to 4× (times) the tolerable pressure of 20 mmHg. However, to maintain the pressure against the skin at below 20 mmHg, the rim has to increase its surface contact area 3 to 4× (times) as the pressure increases.
Stated another way, and to give illustrative numbers to aid understanding, in one example the diameter of the device dome aperture that applies vacuum pressure on the skin is about 4.5 inches (radius of about 2.25 inches). This corresponds to an aperture area of 2.25×2.25×π=about 15.8 sq inches.
The rim is designed such that its skin surface contact area starts from minimal with no pressure applied (only the thin feathered distal end of the near vertical standing rim provides contact) to an additional approximately 2 inches to approximately 2.5 inches (about 2.25 average.). This gives a surface contact area as follows:
Contact area=Total area−Aperture area=[(2.25+2.25)×(2.25+2.25)×π]−15.8=47.8 sq inches.
This means with increasing vacuum pressure, the rim with the forgoing dimensions can deflect outward to increase its surface contact by 3× the aperture area. (Other ratios are also contemplated) This effectively reduces the counter pressure on the skin from the 60 that is not tolerable to 20 that can be tolerated long term. As can be appreciated, other dimensions are also contemplated which would still provide a surface contact area which is multiple of the aperture area, and with increased surface contact area providing larger multiples.
The vacuum expanders of the present invention in preferred embodiments have an external portable vacuum pump with a pressure control mechanism. However, in alternate embodiments, a manual pump such as a bulb can be utilized. With manual pumps, a pressure relief valve can be included to prevent vacuum pressure from reaching damaging levels. Flexible rubber tubing can be connected at one end to a separate external vacuum pump and at the other end to an opening in the dome to apply a vacuum within the dome/shell and impart a distracting force to expand tissue into the shell.
The devices of the present invention can alternatively function without a pump since surface tension is not required. In such embodiments, the vacuum source is the elastic recoil of the rubber sole. The device is placed over the breast and the air is “burped” out until the rim flattens down completely. At that point, the vacuum pressure inside the dome is a function of the elastic recoil force of the rubber and the surface aperture area of the dome. (Pressure=Force/Surface area). Given a fixed surface of the breast, the rubber sole shape design and its modulus of elasticity determine the force required to maintain the pressure within safe therapeutic range. A relief valve could also be included for added safety. Stated another way, the device would use surface tension in the dome section of the device to adhere to the skin so an active vacuum is not needed. The concept is to burp the air out of the flexible dome and rely on the natural recoil of the dome and/or dome rim to pull on the breast tissue.
In some embodiments, a special garment bra can hold the device in place. This can offer the same effect as pressing the feathered edge of the skirt to fold down and wrap around the chest contour to maintain the seal. The bra has first and second apertures or openings that hold the rubber rim and the dome. This component secures the device as the non-sticky device would otherwise fall off whenever the pressure abates. The bra can have a special design to include a series of reinforcement straps and/or padding cushions that maintain the loose feathered peripheral edges of the skirt in firm contact with the skin all around the breast in order to ensure the vacuum seal. The bra hugs the body contour to force the feathered edges to stay in contact with the skin. Reinforcing bands can connect the bra to the rim.
In some embodiments, a tapered thin additional inner rim that blends with the outer rim to increase the sealing surface without interfering with the vacuum expansion force can be provided.
In some embodiments, the rim is radially reinforced with a series of adjustable thin tapered concave fins to better hug the body contour.
In some embodiments, the rim can have an arcuate periphery that spikes at the reinforcing rims and is concave in between (duck feet).
In some embodiments, ribs of varying curvature and length judiciously inserted inside the rubber skirt at various points within its periphery can help it better adapt to the potentially complex and variable surface contour. Edges of the rim can also have an arcuate periphery with peaks at the site of the reinforcing ribs. A variable durometer construct, such as described herein, could also produce the same effect without the additional bulk.
In some embodiments, interchangeable breast shaped dome shells can be provided. A connector mechanism such as circumferential clasping/tightening mechanism 132 can be provided to secure the rubber sole (rim) 132 to the interchangeable shells (
It should also be noted that the design and the circumference of the rubber skirt can be slightly smaller than the circumference of the harder shell dome at their connection areas and configured such that the stretch of the rubber skirt in itself already provides an intrinsic lock and seal similar to the Tupperware seal of food items. That is, using for example a thick rubber band or an elastic string or a tightening band with an easy snap-tightened or spring lock tightened connection between the silicone rim skirt and dome, domes of various depths can be provided. In use, the connector mechanism is released, one dome is removed and a larger dome is secured to the rim by the connection mechanism. This allows the wearer to use the smallest, most innocuous (most concealable) to wear dome that still provides 1-2 cm of room for expansion. Once the breast expands to fill that small dome, the user can easily switch to a slightly larger one keeping the device worn as concealed as possible which is beneficial since the device should be worn near continuously.
It is also contemplated to have markers on the dome and/or on the skirt that need to match so when the dome is removed and replaced, the patient properly connects a new dome, e.g., easily matches the top with the bottom and the left with the right to preserve the desired asymmetric configuration. This can ensure that the domes are replaced in the proper orientation (especially if the same molds are used for the right and the left domes and skirts).
The multiple depths of the dome shells, e.g., from an AA bra cup to a DDD bra cup, are shown in
The rubber skirt, is connected to the hard dome at the firm bottom base (rim) of the dome. In the embodiment of
To be effective, the device of the present invention needs to be worn nearly 24/7. Therefore, it is preferable to be as concealable as a padded bra as well as be able to be worn as easily as their regular padded bra. It preferably should not add more than 1-2 cm beyond the original breast projection. It is therefore advantageous to have the smallest dome possible that still leaves room for the vacuum expansion. Once she fills the dome, she graduates to the next incremental size, either by selecting the next dome/rim or by removing the dome and attaching a larger dome to the same base (rim) in the replaceable dome embodiments. (
The dome is one shell shape that can be used as other shaped shells can also be utilized. Note the various shell and rim materials and structures/features disclosed herein be utilized for the shells of the brassiere, including the replaceable shell versions.
The device can include a rigid. e.g., hard plastic, dome and firm rim, and the skirt (preferably of low durometer rubber) attaches to the dome at the rigid rim and pivots outward at this firm rim. As the skirt pivots outward, an additional inner component of the skirt increases surface contact and improves the seal.
In preferred embodiments, the dome is made of transparent plastic and is translucent enough to visualize the expansion space between the nipple and the peak of the dome. The dome section can be permanently attached to the skirt by glue, sonic welding, or can cure with the skirt in a complex mold with potentially different rubbers. In alternate embodiments, the dome section of the device can be a separate plastic or rubber component that can be attached to and removed from the rim skirt.
The rigid shell is discussed herein and illustrated as dome shaped, however, it is not limited to such shape as it can be other shapes such as a cube, cylinder, etc. for forming the vacuum chamber, since pressure is isotropic. Thus, the discussion herein of shells utilizing the term “dome” is fully applicable to shells of non-dome shapes.
The dome (shell) and rim/skirt separation/distinction should be appreciated. If the skirt/rim is composed of rubber, there could be a gradual change in durometer from the skirt to the dome. Alternatively, or in addition, the dome can be rigidified with reinforcing ribs. There could be a skin, sheet, etc. covering both the dome and the skirt. The skin, sheet, etc. could be a hard-protective durometer or a soft-cushioning durometer.
It should be appreciated that materials other than rubber could be utilized for the rim (and other components/features) and are within the scope of the present invention.
The present invention could be used in combination with the surface tension concept of U.S. Pat. No. 10,433,947 if a rubber dome is used. In this combined embodiment, the wearer would need to find the proper dome size that perfectly encloses her breast. With no vacuum space, and with the skin in complete contact with the inner surface of the dome, surface tension between the dome and the skin would maintain a friction free adhesion. The air would be burped out of the flexible dome and rely on the natural recoil of the dome and/or dome rim to pull on the breast tissue. The expansion force becomes a function of the elastic recoil properties of the rim/flexible dome construct.
The present invention also provides methods of use of the expanders. For example, one method provides reducing shear stress including positioning a device having a shell and a rim (skirt) extending from the shell configured for contact with a body of a patient, wherein the rim is non-adherently positioned on the body so that upon application of a distracting force within the shell, the rim spreads laterally outwardly with respect to the shell such that shear stress is reduced at a junction between skin inside the shell and the skin held down by the rim. The method can include providing a distractive force by elastic recoil of one or both of the shell or rim or by applying a vacuum within the shell.
The expander devices disclosed herein have several useful methods/applications such as the following three: 1) Enlargement of the expansion treated tissue based upon the principle of tension induced tissue growth. This application takes time (e.g., months of use) because tissue growth is a slow process. (This is an alternative that does not require surgery); 2) Temporary stretching (e.g., mechanical tension) of the expanded tissues to generate a vascularized, primed, and fertilized scaffold for a) grafting and/or b) for injection of materials/agents derived from allografts or xenografts or other growth stimulating factors. This application takes weeks compared to the stand alone tissue growth that takes months. The autologous fat grafting and the method of grafting materials derived from fat whether autograft, allograft, or xenograft can be utilized as disclosed in application Ser. No. 17/719,456 filed Apr. 23, 2022, the entire contents of which are incorporated by reference. This application describes acceleration and improvement of ingrowth into a graft by application of mechanical tension over the graft/host interface. 3) Preservation or Maintenance of a pre-expanded state either from surgery, grafting, injection of fluids, or other means of pre-expanding the tissues and then using the device to maintain the expanded or swollen state.
To achieve any of the three foregoing methods or applications, two possible alternatives are: 1) Continuous wear at a constant pressure of 20 mmHg for at least 10 hours/day. Note 20 mmHg is a level of pressure that does not occlude capillary circulation and can therefore be maintained for a long period of time over the tissue; or 2) for a more effective expansion, raising the pressure up to 80 mmHg for a short while during which the capillaries collapse and tissue perfusion stops. This high pressure therefore cannot be maintained for more than a few minutes before tissue damage sets in so the pressure then drops to 0-10 mmHg to allow re-circulation for a few minutes. This cycling pressure alternative is a more efficient method, but it consumes more battery and requires a more complex electronic control mechanism. Note the current protocol is to raise the pressure to 60 mmHg for about 2-6 minutes and then release it to 0-10 mmHg for 1-2 minutes. While most people can tolerate 60 mmHg, a few will be allowed to reach 80 mmHg without problems and some will need to have their pressure reduced to 40 mmHg because 60 mmHg is not tolerated.
The devices of the present invention can be used with the grafts and materials disclosed in commonly assigned pending application Ser. No. 17/719,459, filed Apr. 23, 2022. The devices enlarge the tissue, e.g., breast tissue, by mechanical force to temporarily create a scaffold for accepting allograft.
Persons skilled in the art will understand that the elements and features shown or described in connection with one embodiment may be combined with those of another embodiment without departing from the scope of the present invention and will appreciate further features and advantages of the presently disclosed subject matter based on the description provided.
While the present invention has been described with reference to the specific embodiments thereof, which constitute non-limiting examples, it should be understood by those skilled in the art that various changes and modifications may be made and equivalents may be substituted without departing from the spirit and scope of the invention as defined in the appended claims. In addition, many modifications may be made to adopt a particular situation, material, composition of matter, process, process step or steps, to the objective spirit and scope of the present invention. All such modifications are intended to be within the scope of the claims appended hereto.
Where a range of values is provided, it is understood that each intervening value within the stated range is encompassed within the invention.
Throughout the present disclosure, terms such as “approximately,” “about,” “generally,” “substantially,” and the like should be understood to allow for variations in any numerical range or concept with which they are associated. For example, it is intended that the use of terms such as “approximately,” “about” and “generally” should be understood to encompass variations on the order of 25%, or to allow for manufacturing tolerances and/or deviations in design.
Although terms such as “first,” “second,” “third,” etc., may be used herein to describe various operations, elements, components, regions, and/or sections, these operations, elements, components, regions, and/or sections should not be limited by the use of these terms in that these terms are used to distinguish one operation, element, component, region, or section from another. Thus, unless expressly stated otherwise, a first operation, element, component, region, or section could be termed a second operation, element, component, region, or section without departing from the scope of the present invention.
Each and every claim is incorporated as further disclosure into the specification and represents embodiments of the present disclosure. Also, the phrases “at least one of A, B, and C” and “A and/or B and/or C” should each be interpreted to include only A, only B, only C, or any combination of A, B, and C.
This application is a continuation in part of application Ser. No. 17/534,527, filed Nov. 24, 2021, which claims priority to provisional application Ser. No. 63/122,016, filed Dec. 7, 2020. The entire contents of each of these applications are incorporated herein by reference.
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