Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Breast prosthesis – Implantable
Reexamination Certificate
1997-03-25
2001-05-08
Isabella, David J. (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Breast prosthesis
Implantable
C623S011110
Reexamination Certificate
active
06228116
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to implantable prosthetic devices. More particularly, it relates to implantable tissue expanders for use in plastic and reconstructive surgery to stretch tissue in order to augment a soft tissue deficit, cover an ablative defect, or reconstruct a portion of the body.
BACKGROUND OF THE INVENTION
Implantable prosthetic devices have been used in numerous locations in the body. The most common use has been for restoring or improving upon normal body contour or augmenting as well as reconstruction of the female breast. The most common breast prosthesis is similar to that disclosed in U.S. Pat. No. 3,293,663 to Cronin, in which there is a flexible elastomeric container, typically silicone, which is filled with a soft gel, typically silicone gel or a saline solution or a combination of both.
A tissue expander is surgically implanted beneath tissue to be stretched and is filled at appropriate intervals with biocompatible fluid. After sufficient stretch has been achieved the tissue expander is removed and the newly available tissue used to cover a soft tissue defect or used to create a replacement body part. A breast tissue expander may be made convertible to a definitive, long-term, augmentative prosthesis, also known as an “implant”.
As the field has progressed from simple wound coverage to reconstructing more realistic body parts incorporating prosthetic devices, especially in the case of the female breast, it has become evident that more control of the expansion process would be desirable in order to speed the process, to minimize the morbidity and the number of surgeries involved, as well as to refine the end result.
In breast reconstruction, major problems associated with the tissue expansion process include difficulty in creating a normal teardrop shaped and normally pendant breast due to the inability to create a properly shaped pocket. Presently the only options are either multiply chambered expanders with multiple injection ports or laminated component structures. These are commercially considered less than desirable because they are prohibitively expensive. They are functionally suboptimal as slippage at the soft tissue/expander interface may occur and there is a lack of purchase at the interface which is associated with inappropriate thinning and grossly non-uniform expansion of tissue.
SUMMARY OF THE INVENTION
A soft tissue expander, which is a temporary implant into the body, utilizes structures having differential and directional expansion capability to project the expander or implant in the desired directions. In a preferred embodiment, an expander or implant has an exterior surface defining a volume, the exterior surface including a base portion, a first wall and a second wall, wherein the second wall is relatively thinner than the first wall. A fill port, which may be integrally molded into the expander, is included. As the expander is inflated, differential expansion occurs with the relatively thin second wall section expanding more than that of the first wall section.
The base may include ribs or other molded-in structures to increase structural integrity. Additionally, the base may include “toes” or other structures which project out from the base, such as flanges, which are adapted to provide a broader base or footprint to the expander. The expander enjoys increased base and dimensional stability as a consequence.
Additional directional expansion may be achieved through use of optional bellows molded into a portion of the expander shell wall. As the expander is inflated, the bellows provide a projection beyond that provided by the basic expander. Limiting rings may be used, such as surrounding the bellows at the bellow base which mates to the expander.
Molded-in geometric patterns may be employed to present varying textured surfaces to the internal or external surfaces of the implant or expander. This results in increased soft tissue purchase by virtue of unique surface topography and assists in obtaining differential expansion by virtue of the differential purchase resulting from the different molded-in patterns. Textured surfaces also have the effect of weakening periprosthetic scar tissue. Optionally, compressive structures may be beneficially used on the surface of the implant or in the interior of the implant.
In another preferred embodiment, a tissue expander uses multiple chambers wherein the chambers are in fluid communication. Preferably, one of the chambers is adapted for placement behind a muscle, such as the pectoralis muscle if the expander is used for breast reconstruction.
Accordingly, it is an object of this invention to provide an improved implant which functions as a soft tissue expander.
It is a further object of this invention to provide an enhanced ability to weaken periprosthetic scar as well as to permit the surgeon to improve cavity contour at the end of the expansion phase.
It is yet a further object of this invention to create variable yet controlled purchase at the tissue/expander interface and to provide for differential expansion capability by varying wall thickness. It is another object of this invention to provide for directional expandability of the expander.
It is an object of this invention to enable the surgeon to create a more natural soft tissue envelope for the human breast including a more natural inferior sulcus.
It is a further object of this invention to provide an implantable prosthesis which permits postimplantation accommodation of total volume, either more or less than the volume at implantation.
It is a further object of this invention to provide an implantable mammary prosthesis which permits postimplantation accommodation of implant projection which is defined as the distance from the chest wall pole of the implant to the opposite pole of the implant.
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Isabella David J.
Lyon & Lyon LLP
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