The disclosed embodiments relate generally to the field of prosthetic medical devices. More specifically, the field relates to the development of prosthetic medical slings implemented for supporting internal body structures.
Pubovaginal sling procedures are very prevalently used to offer support needed to stabilize a patient's urethra or bladder. The most common device used in executing such a process is an elongated flexible strip constructed of a nonabsorbable polypropylene mesh material, the ends of which can be anchored elsewhere in the patient's body, and support is offered to prevent incontinence.
This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Other aspects and advantages will be apparent from the following detailed description of the embodiments and the accompanying drawing figures.
In embodiments, a medical support device includes an elongated body comprised of an expanded fluoropolymer. The device is used to support a body component, e.g., in embodiments, can be used as a urethral sling or for other like applications. In some embodiments, the elongated expanded fluoropolymer is polytetrafluoroethylene (ePTFE). The ePTFE can be formed into a hollow crushed tube shape. In some of the crushed tube embodiments, the tube is filled with a co-elongated core within the tube. In some of the embodiments where the crushed tube includes a core, the core can be made of fluorinated ethylene propylene (FEP).
In some aspects, the techniques described herein relate to a method for producing a surgical implant device, the method including: mixing a polytetrafluoroethylene (PTFE) resin paste with an extrusion aid; forming the resin paste and the extrusion aid into a billet; extruding the billet into a PTFE tube; drying the PTFE tube to remove the extrusion aid; reheating the PTFE tube at a temperature lower than a melt temperature of the PTFE tube; expanding the PTFE tube in at least one dimension to create a node/fibril structure; heating the PTFE tube to a temperature above a thermal transition temperature for the PTFE thus setting a node/fibril structure in place resulting in an expanded tube; and applying heat and pressure to collapse the expanded tube and adhere the inside tube surfaces together to form a substantially flat article having rounded lateral edges.
In some aspects, the techniques described herein relate to a method, wherein the expanding the PTFE tube in at least one dimension step includes: unidirectionally and longitudinally expanding the PTFE tube resulting a plurality of substantially parallel fibrils interconnecting a plurality of nodes defining a plurality of apertures therebetween, each aperture in the plurality of apertures having a pore size less than 2 microns.
In some aspects, the techniques described herein relate to a method including: establishing a tube wall thickness in the extruding step of about 0.20 millimeters.
In some aspects, the techniques described herein relate to a method including: allowing the article to cool after the restraining step and the applying heat and pressure step.
In some aspects, the techniques described herein relate to a method including: presenting the article for use as a supportive surgical implant.
In some aspects, the techniques described herein relate to a method including: configuring the article for use as a supportive surgical implant.
In some aspects, the techniques described herein relate to a method including: sizing the article to operate as a supportive surgical implant, and configuring a first end and a second end of the article to attach to surgical placement aids.
In some aspects, the techniques described herein relate to a method including: configuring the article to have a length making the article usable as a supportive surgical implant device having first and second ends.
In some aspects, the techniques described herein relate to a method including: densifying the first and second ends by the application of elevated heat and pressure making the ends apt for the receipt of implantation aids.
In some aspects, the techniques described herein relate to a method including: forming apertures into the first and second ends, the apertures being configured to receive implantation aids.
In some aspects, the techniques described herein relate to a method including: after setting the node/fibril structure in place, and before the step of applying heat and pressure: inserting a meltable filler material into the expanded tube, and melting the filler material to aid in adhering the inside tube surfaces together.
In some aspects, the techniques described herein relate to a method including: selecting Fluorinated Ethylene Propylene (FEP) as the meltable filler.
In some aspects, the techniques described herein relate to a method wherein the applying heat and pressure step is executed at a temperature lower than the thermal transition point of the PTFE.
In some aspects, the techniques described herein relate to a method wherein the applying heat and pressure step is executed by: sandwiching the expanded tube between a hot surface and another surface under moderate pressure; and applying heat and pressure until porosity is reduced and a now collapsed tube softens.
In some aspects, the techniques described herein relate to an article usable as a supportive surgical implant, the article including: a collapsed tube forming an elongated body having a first end and a second end, rounded lateral edges, the elongated body being formed of a biocompatible, bacteria-resistant fluoropolymer material, the fluoropolymer material being configured to have a plurality fibrils connecting between nodes.
In some aspects, the techniques described herein relate to a article wherein the biocompatible, bacteria-resistant fluoropolymer material includes Polytetrafluoroethylene (PTFE).
In some aspects, the techniques described herein relate to a article wherein the bacteria-resistant fluoropolymer includes expanded PTFE (ePTFE).
In some aspects, the techniques described herein relate to a article wherein the plurality of fibrils extend longitudinally substantially in parallel, and the plurality of fibrils and plurality of nodes together define a plurality of pores having sizes of 2 microns or less in smallest dimension.
In some aspects, the techniques described herein relate to a article wherein the article is configured for use as a tissue support.
In some aspects, the techniques described herein relate to a article wherein the article is configured for use as a pubovaginal sling.
In some aspects, the techniques described herein relate to a article wherein the first end is configured to receive a first surgical placement aid, and the second end is configured to receive a second surgical placement aid.
In some aspects, the techniques described herein relate to a article wherein the bacteria-resistant fluoropolymer includes a microporous structure which is relatively closed to ingrowth and bacterial penetration.
Regardless of the particular configuration involved, the elongated medical support device can have first and second ends both receivable by a placement tool designed to aid with implanting the device into the human body in a supporting capacity regarding an internal structure. In some embodiments the device is usable as a surgical sling.
Illustrative embodiments are described in detail below with reference to the attached drawing figures, which are incorporated by reference herein and wherein:
The drawing figures do not limit the invention to the specific embodiments disclosed and described herein. The drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the invention.
The following detailed description references the accompanying drawings that illustrate specific embodiments in which the invention can be practiced. The embodiments are intended to describe aspects of the invention in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments can be utilized and changes can be made without departing from the scope of the invention. The following detailed description is, therefore, not to be taken in a limiting sense. The scope of the invention is defined only by the appended claims, along with the full scope of equivalents to which such claims are entitled.
In this description, references to “one embodiment,” “an embodiment,” or “embodiments” mean that the feature or features being referred to are included in at least one embodiment of the technology. Separate references to “one embodiment,” “an embodiment,” or “embodiments” in this description do not necessarily refer to the same embodiment and are also not mutually exclusive unless so stated and/or except as will be readily apparent to those skilled in the art from the description. For example, a feature, structure, act, etc. described in one embodiment may also be included in other embodiments, but is not necessarily included. Thus, the technology can include a variety of combinations and/or integrations of the embodiments described herein.
Synthetic slings have been available for implant procedures for many decades. The most common form of sling is constructed of polypropylene, which is typically comprised of woven or knit filaments. A polypropylene sling presents open structure which allows bacteria to penetrate. This can lead to post-operative infection. Although these devices have been implanted in many thousands of patients, there remain many post-implantation problems that have yet to be resolved. Most of these problems are clinically significant, and can end with surgical retrieval of the devices, which can lead to further internal tissue damage.
One problem with these prior art polypropylene mesh slings is damage that can be caused upon surgical implant. Those skilled in the art will recognize that during surgery the polypropylene mesh sling is worked through bodily tissues, e.g., being pushed or pulled therethrough using needles or other devices. The edges of these prior art slings may be rough, and when passed through the body during surgical implant can create tissue damage, e.g., scar tissue, etc.
Any limited damage created upon implant of the polypropylene sling is not necessarily considered a bad thing, in that the damage causes an immediate inflammatory response, which ultimately helps incorporate the device structurally. But this damage can compromise tissues in undesirable ways also.
Another problem is that the polypropylene mesh degrades over time. This degradation can result in migration of sling segments or filaments, or even extrusion of same. These obvious failures create harm, and often result in the need for removal of an already-implanted sling by a surgery far more complicated and potentially harmful than the initial implant procedure, and can leave behind massive scar tissue, as well as result in chronic pain moving forward.
Another problem is that of infection. The vulnerability of the polypropylene to infection is due in large part to the nature of the mesh material. Following implant of a conventional polypropylene mesh sling, it is considered desirable that the surrounding tissues grow into the device. This ingrowth is seen as necessary to secure the polypropylene device in place. But this also makes the device extremely difficult to remove surgically, e.g., in the case of complications such as infection or structural degradation over time. Many times, surgery to remove the sling creates serious problems to the tissues on or around the implant.
The invention disclosed herein is a prosthetic medical sling made of a novel synthetic material, in embodiments, a relatively closed expanded Polytetrafluoroethylene structure. The inventive design of the medical device provides for a strong, supportive, biocompatible sling that resists bacterial invasion and disintegration.
The prosthetic sling embodiments disclosed herein overcome the aforementioned problems significantly.
More specifically, the embodiments described herein comprise a novel synthetic prosthetic medical sling that is biocompatible, resists bacterial infection, exhibits significant long-term strength to support tissues, does not promote massive scar tissue, and will not deteriorate over time. Further, the sling embodiments exhibit strength adequate for intended use, are supple and tissue compliant to minimize scar tissue formation, and are durable, as PTFE, a fluoropolymer is known to be resistant to biodegradation.
Embodiments are comprised of a processed fluoropolymer, such as Polytetrafluoroethylene (PTFE). Embodiments disclosed in the figures herein incorporate expanded PTFE, or “ePTFE” which is formed by longitudinal expansion under heat. An ePTFE article can be manufactured to have fibril lengths such that the article is relatively closed structured to prevent the infiltration of bacteria yet supple for tissue compliance, and adequately strong for its intended use as a tissue support device. And of course, as ePTFE, it is fully biocompatible and will not degrade.
The micro porous structure of known ePTFE articles is characterized by a plurality of nodes that are connected together by a plurality of fibrils. The nodes are essentially solid PTFE, having a density of about 2.0-2.2 grams per cubic centimeter, whereas the density of the expanded material is less than about 2.0 grams per cubic centimeter. The shape, size and orientation of the nodes and fibrils within the structure can be controlled by varying the expansion rate, expansion ratio, number of expansion axes and other processing parameters to yield many different structures. It is also known that properties such as the expandability and microstructure of the expanded article vary with the molecular weight, particle size and other physical characteristics of the PTFE resin.
The disclosed embodiments of the ePTFE implant device (e.g., sling) are configured as (i) a first embodiment comprised of a collapsed tube (
The body of the device in each of the embodiments in
The embodiments above have shown no ingrowth or bacterial penetration. Thus, they avoid the well-known infection problems existing in the polypropylene prior art devices. Additionally, because ingrowth is avoided, surgical removal is relatively easy to accomplish, if necessary, and leaves little if any scar tissue or other damage.
The embodiment 100 is shown in perspective in
Referring to
A process for making the first embodiment of
Next, the pellet is mechanically extruded using a ram extruder. The extruder initially compacts the resin and extrusion-aid paste and feeds it into a die nozzle. The material is then subjected to very high pressure and shear forces within the die such that the resin exits as a tubular shaped article.
After being extruded, the article is dried. More specifically, the lubricant is removed by subjecting the article to temperatures slightly above the boiling point of the lubricant (e.g., about 150° C.), and far below the sintering or coalescing temperature of the polymer (generally at about 327° C.) in embodiments.
Following extrusion and drying, the tubular PTFE is heated above the thermal transition point of about 354° C. and expanded longitudinally. This expansion process creates openings containing fibrils interconnecting solid nodes of PTFE.
In embodiments, the article is extruded (and expanded) to a tubular wall thickness of about 0.20 millimeters.
The now tubular expanded PTFE article is allowed to cool over a period of time at a lower temperature, e.g., at ambient. The article can also be cut into desired lengths which will ultimately comprise individual prosthetic devices, e.g., surgical slings.
Once the article has cooled and is ready for use it, in embodiments, will have expanded fibrils in the elongated dimension.
After expansion the article, in embodiments, is subjected to post-expansion processing where the article is subjected to both moderate temperatures and pressures (below the thermal transition point for PTFE) to flatten and soften the article. This can be done by sandwiching the length of the article between a single hot surface and an opposing surface, between two opposing plates, or on one or more rollers in a system. The temperature at which the article is reheated is, in embodiments, below the thermal transition point (about 254° C.). Conventionally, it has been assumed that nothing can happen micro-structurally below that transition temperature, but here significant changes in the structure have been discovered (e.g., at temperatures around 200° C.). The pressure applied to the article during this step is low, e.g., a few psi.
Upon completion of this post-expansion processing, the article will be softer. Additionally, the fibril structures will, microscopically, appear to be more integrated and pore sizes will be reduced and in some cases pores eliminated. The result is a material that is softer and at the same time less porous.
As an optional additional step, an antimicrobial coating can be added after the completion of earlier process steps discussed above or below, in order to inhibit bacteria.
Once the article has been processed as discussed above, the article can be presented for use along with existing implant systems and/or methods. The article can also be prepared for use as a sling according to any number of configuration steps. For example, in embodiments, the ends of the article can be configured for connection at each of ends 102 and 104 shown in
Again here, as an optional step, antimicrobial coating could be added after the article is configured for use as an implant instead of beforehand. This timing might be advantageous since the coating of the article will occur when the implant is in final (or nearly final) form.
A 100% PTFE powder was mixed with mineral spirits, and then compressed under relatively low pressure to form a billet. The billet was then mechanically extruded under high pressure using a ram extruder having a die nozzle such that the resin was expanded and solidified into a tubular shaped article having a thickness of about 0.20 millimeters.
After being extruded, the article was dried by subjecting the article to temperatures at about 175° C., which is slightly above the boiling point of the lubricant (about 150° C.), and far below the sintering or coalescing temperature of the polymer (about 327° C.).
After drying, the tubular article was expanded longitudinally at elevated temperatures and sintered to lock in the expanded structure.
The tubular expanded PTFE article created was then allowed to cool over a period of time at a lower temperature, e.g., at ambient.
Once the article was cooled, it possessed expanded fibrils in the elongated dimension, and resulted in the microscopic appearance shown in the micrograph of
After expansion, the now expanded article as shown in the
Upon completion of this post-expansion processing, the article was appreciably softer. Additionally, the fibril structures were more integrated with the nodes/body of the article as can be seen in the post-processing micrograph of
The softness, strength, and porosity created in the article proved to be ideal for use as a surgical sling device, and are also quite surprising in view of conventional wisdom that when ePTFE structure is closed down, stiffness goes up.
The article was then cut into desired sections which will ultimately comprise individual slings, and otherwise configured for use as sling implants.
Once the filler has been put into the processed ePTFE tube, heat and pressure are applied to flatten the article much like is done in the process described for the first article 100 except that the temperature selected should be greater than the melt point of the filler, but still lower than the melt point for PTFE. The application of the moderate temperatures and pressures flatten and soften the article, and allow the filler to serve as a bond enhancer, facilitating adhesion within the now collapsed tube.
Articles made according to the example above have been configured for use as surgically implantable slings as discussed above (before the example section). For example, the ends have been modified to add hardware like discussed for
Additionally, an antimicrobial coating step has been contemplated to be beneficial for many applications. The coating could be added any time after the completion of post-processing heat treatment, but most likely be executed after the article has been configured for use as an implant, the purpose being to inhibit bacteria.
Although the descriptions above relate to the ePTFE strips of articles 100 and 200 being implemented as prosthetic slings used to stabilize a patient's urethra or bladder, they could also be useful in providing support for other pelvic organs. Additionally, multiple strips could be used together for certain applications. Further, the articles could be used for the support of rectal muscles in other applications.
Many different arrangements of the various components depicted, as well as components not shown, are possible without departing from the spirit and scope of what is claimed herein. Embodiments have been described with the intent to be illustrative rather than restrictive. Alternative embodiments will become apparent to those skilled in the art that do not depart from what is disclosed. A skilled artisan may develop alternative means of implementing the aforementioned improvements without departing from what is claimed.
It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations and are contemplated within the scope of the claims. Not all steps listed in the various figures need be carried out in the specific order described.
This application claims the benefit of U.S. Provisional Application No. 63/140,052 filed Jan. 21, 2021, the entire contents of which are herein incorporated by reference.
Number | Date | Country | |
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63140052 | Jan 2021 | US |