Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arterial prosthesis – Absorbable in natural tissue
Reexamination Certificate
1998-08-07
2001-05-08
Willse, David H. (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arterial prosthesis
Absorbable in natural tissue
C604S890100, C424S426000, C424S428000, C623S023750
Reexamination Certificate
active
06228111
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a biodegradable implant or the like manufactured of polymer-based material and intended to be installed in tissue conditions.
BACKGROUND INFORMATION
In surgery, it is known to employ biodegradable, elongated, typically tubular surgical implants and devices for supporting or combining or dividing elongated organs, tissues or parts thereof. These objects include various canals, ducts, intestines, blood vessels, tubes, such as bronchial tubes, urinary tracts, nerves etc.
In this context, the biodegradable material refers to a material manufactured of polymer, copolymer or polymer composition, the degradation and/or absorbing of which material takes place by means of metabolic reactions and/or secretion through kidneys, lungs or intestines or skin.
A multitude of publications describe various tubular implants and surgical devices manufactured of biostable or biodegradable materials. Such implants are disclosed e.g. in publications U.S. Pat. Nos. 3,108,357; 3,155,095; 3,272,204; 3,463,158; 3,620,218; WO 83/03752; WO 84/03035; Daniel and Olding, Plast. Rec. Surg. 74 (1984) 329; WO 90/04982; Van Andersdahl et al., Seminars in Urology, Vol. II (1984) 180; Raja Subra Manian, ASAIO Journal 40 (1994) M584; U.S. Pat. Nos. 4,768,507; 4,923,470; 4,973,301; 4,990,131; 4,994,066; 5,019,090; EP-0 606 165 A1; WO 04/15583; U.S. Pat. Nos. 4,950,258; 5,160,341 and 5,085,629.
Known biostable, that is, in tissues practically non-degradable implants and surgical devices of the above mentioned and corresponding type have several shortcomings. Their biostable parts, e.g. fibres, plastic and metal threads or rings or tubes or the like remain in the system even after an organ or a tissue has healed, and therefore such implants and devices can later be harmful to the patient, causing e.g. infections, inflammatory reactions, foreign body reactions and/or particles or corrosion products or the like can be released therefrom, which can further cause harmful reactions in the system.
Known biodegradable implants and surgical devices and devices of a corresponding type, e.g. of the type disclosed in the above-mentioned publications, do not cause the same kind of chronic complications as biostable implants and surgical devices, since biodegradable implants and devices absorb and degrade entirely in the system finally leaving the tissue entirely.
However, typically tubular implants and surgical devices involve the drawback that they degrade evenly at their entirely length, that is, the gradient of biodegration is directed to the centre of the cross section along the entire length of the implant or the corresponding surgical device. Thus, known elongated implants and surgical devices lose their strength evenly at their entire length, and finally the whole implant or surgical device loses its strength in a relatively short period of time at its entire length. As a result, the implant or the surgical device disintegrates evenly after having lost its strength in a short period of time or even suddenly to small pieces and particles [cf. e.g. Törmälä et al. Biomed. Mater. Res. 25 (1991) 1]. In case the disintegrating implant or surgical device is placed inside a hollow, elongated organ or tissue, it is possible that an uncontrollable quantity of particles and pieces is released from the disintegrating implant or the surgical device in a short period of time, wherein some of these parts and particles can join together and can contribute to a stoppage in the hollow tissue or organ, such as in a flow duct of a blood vessel, urinary tract or other tubular organ or tissue.
SUMMARY OF THE INVENTION
The present invention surprisingly discloses that when the implant or the corresponding surgical device is manufactured in a controlled manner to degrade so that it degrades according to its zone division, e.g. gradually starting from one end, it is possible to eliminate the danger that the prior art implants or corresponding surgical devices contribute to a stoppage in the tubular tissue or organ, and in this manner it is possible to improve the technical level in the field. A controlled degradation according to zone division provides the further advantage that the implant or the corresponding surgical device can be constructed to react in biodegradation situations exactly according to a specifically planned use.
For providing the above mentioned advantages, the implant or surgical device according to the invention is thus mainly characterized by what is presented in the characterizing portion of claim
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DETAILED DESCRIPTION OF THE INVENTION
An implant or a corresponding surgical device according to an advantageous embodiment of the invention has an elongated configuration and it starts to degrade in a controlled manner under tissue conditions in accordance with zone division at its first end in a manner that the implant disintegrates from said end onwards into small pieces and/or particles and/or absorbable components in a manner that degradation proceeds in a controlled manner towards the second end. Thus, small quantities of small pieces, particles and corresponding degradation products are constantly released from the implant, which pieces, particles and the like can exit the interior of the hollow organ or tissue with fluids excreted in fluid flows e.g. in urine, blood or by endocrine glands and/or due to movements of muscles surrounding the tubular tissue.
An implant or a corresponding surgical device according to the invention has advantageously an elongated configuration. It can be a tight tube or a tube perforated at its surface, a single-threaded spiral twisted of rod-like preform, a multi-threaded spiral or spiral-structured tube in which the spirals are twisted in opposite directions and pass each other above and below, forming a tubular braiding. The implant or the corresponding surgical device according to the invention can also have a configuration of a braided or knitted tube or the like. It is obvious to an expert in the field that any biostable or biodegradable elongated implant or a corresponding surgical device, e.g. those presented in the publications mentioned in the preamble of the specification, can be employed as a model when constructing implants or corresponding surgical devices in accordance with the invention.
Implants or corresponding surgical devices in accordance with the invention can be manufactured of various biodegradable polymers, copolymers or polymer alloys disclosed in abundance in the literature e.g. in publication WO 90/04982 and in Finnish patent application 953694).
Implants or corresponding surgical devices in accordance with the invention can have a non-reinforced structure, e.g. manufactured by melt-processing techniques or solution techniques, or they can be reinforced e.g. by using self-reinforcing or reinforcing by absorbable polymeric or ceramic fibres.
Some advantageous embodiments of the implant or the corresponding surgical device of the invention are presented in the accompanying dependent claims.
The method according to the invention is mainly characterized by what is presented in the characterizing portion of the independent claim relating to the method.
The method for manufacturing an elongated implant or a corresponding surgical device is based on the fact that the macroscopic and/or microscopic structure of the implant or the corresponding surgical device is formed, according to the method, to be such that the implant or the corresponding surgical device disintegrates, according to a zone division created thereto in a controlled manner under hydrolytic conditions into small particles and/or pieces at its different parts at different times.
By regulating the macroscopic structure, the different parts of the implant or the corresponding surgical device can be disintegrated at different times by creating its walls to have different thickness at its different parts. Provided that the micro-structure of the implant or the corresponding surgical device is approximately homogeneous, usually the thinner the wall struc
Tormala Pertti
Välimaa Tero
Bionx Implants Oy
Jackson Suzette J.
Kenyon & Kenyon
Willse David H.
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