Bioabsorbable self-expanding endolumenal devices

Abstract

The present invention is directed to bioabsorbable self-expanding medical devices for use inside or outside body conduits that self-expand at, or below, normal human body temperature without requisite for a polymeric thermal transition

Description

FIELD OF THE INVENTION [0001] The present invention is directed to implantable medical devices. In particular, the invention is directed to self-expanding bioabsorbable endolumenal devices. BACKGROUND OF THE INVENTION [0002] A variety of implantable medical devices have been developed to treat diseased, injured, or deformed body conduits. In cases where malfunctioning body conduits have reduced inner diameters, there is usually reduced flow of vital fluid or gas through the conduits. In extreme cases, the malfunctioning conduits are occluded. Implantable medical devices used to open and / or expand, or to otherwise treat obstructed or constricted body conduits often reside in the conduits for a period of time following deployment of the devices. The devices serve primarily as mechanical supports inside the malfunctioning conduits to help maintain the conduits in more open, or patent, conditions. [0003] These types of implantable medical devices are usually threaded through a healthy b...

AI Technical Summary

Benefits of technology

[0033] Though sufficiently strong to resist radially compressive forces from tissue in which devices of the present invention are implanted, the devices have a Young's modulus equal to or less than the tissue in which the devices are implanted. Accordingly, tubular devices of the present invention have integral non-elongating frameworks with a Young's tensile modulus of approximately than 2.1×106 Pascals when evaluated longitudinally in an open, uncompressed, and unrestrained (i.e. fully deployed) configuration. Devices of the present invention are very compliant with implanted tissue as a consequence. A multiplicity of fenestrations is provided in the integral framework to further en

Problems solved by technology

Of particular concern in leaving a metallic implant in a patient is the negative impact a subsequent procedure may have on the patient as a result of the implanted device.

For example, the strong magnetic field produced by a magnetic resonance imaging (MRI) machine can adversely interact with the metallic implant.

Also, the presence of a chronically implanted device can cause abrasions or erosions to tissue in which the device is implanted.

Additionally, a subsequent endoluminal procedure can also result in an adverse encounter, or interaction, with a previously implanted device.

Unfortunately, when the polymeric material used to make the stent is placed inside a body conduit and raised above its melt temperature to undergo a re-modeling process, any inconsistency or inadequacy in thermal transfer from the heated balloon to the device as it is deployed can cause irregular and potentially unpredictable device deformations.

Consequently, implantable medical devices intended for use as degradable stents or other temporary scaffoldings for a body conduit made of poly(ε-caprolactone), or similar homopolymers that require a thermal softening or melting transition above normal human body temperature in order to expand, are likely to lack sufficient reliable mechanical strength to be practical devices.

The stent is described as expandable using a “thermally-assisted mechanical expansion process at a temperature between about 38 degrees centigrade and 55 degrees centigrade.” Hence, the Healy et al. stent does not expand at normal human body temperature of 37 degrees centigrade and is also described as risking a “potentially hazardous” fracture if expansion is attempted in the brittle and glassy state found below the Tg of the stent.

Devices requiring in situ application of heat above normal human body

Images