Tissue Response to Porous Materials used for Ossicular Replacement Prostheses

Abstract

Porous materials were first proposed for the fabrication of ossicular replacement prostheses in the mid 1970’s (1–3). The working hypothesis was that the tissue ingrowth into the porosity of the implant would serve to stabilize the prosthesis in the middle ear thus facilitating sound conduction and preventing dislodgement and extrusion. Initially, porous polymers had been investigated as implants in soft tissue in the early 1950’s (4). Studies investigating porous metals (5,6), ceramics (7) and polymers (8,9) as implants in bone were initiated in the early 1970’s. These studies predating the use of porous materials in otology had demonstrated that tissue ingrowth into the porosity could provide attachment to surrounding bone or soft tissue. The decision to employ porous polymers, instead of metals or ceramics, for ossicular replacement was based on the concern for extrusion of stiff devices (2) and the need to be able to trim the device at surgery. A rationale for use of polymers with pore sizes of less than 100 um could have been based on having porosity a) which provided a prosthesis of sufficient strength, and b) which fell below the minimum pore size requirements (7) for bone ingrowth (to prevent bony ankylosis).