Friday, March 29, 2024

Ossiculoplasty

History of the Procedure

The earliest recorded attempt to re-establish a connection between the tympanic membrane and the oval window in the case of a missing ossicle was in 1901. Since then, numerous materials have been used to re-create the middle ear sound-conducting mechanism. Many materials have been used for ossicular substitution or reconstruction, including both biologic and alloplastic materials. Biologic materials include autograft or homograft ossicles, cortical bone, teeth, and cartilage.

The most commonly used autograft material has been the incus body, which is often reshaped to fit between the manubrium of the malleus and the stapes capitulum. Autograft materials are not always available, or—as in patients with cholesteatoma—an ossicle may have microscopic squamous epithelium infiltration that precludes such use. Autografts have several disadvantages, including lack of availability in chronically diseased ears, prolonged operative time to obtain and shape the material, resorption and/or loss of rigidity (especially with cartilage), and possible fixation to the walls of the middle ear. Additionally, osteitis may exist within the ossicles, and the risk of residual cholesteatoma may be increased in patients with cholesteatoma.

Irradiated homograft ossicles and cartilage were first introduced in the 1960s in an attempt to overcome some of the disadvantages of autograft implants. Homograft ossicles or cartilage may be presculpted by the manufacturer, or they may be sculpted during surgery. Since 1986, homograft materials rarely are used because of the risk of disease transmission (eg, AIDS, Creutzfeldt-Jakob disease).

Because of the disadvantages of autograft materials and the potential risk of infection from homograft implants, alloplastic materials are the most commonly used materials for ossicular reconstruction today. Alloplastic materials can be classified as biocompatible, bioinert, or bioactive. In the late 1950s and the 1960s, biocompatible material, such as polyethylene tubing, Teflon, and Proplast, were used. Ossicular reconstruction with these materials often resulted in migration, extrusion, penetration into the inner ear, or significant middle ear reactivity. For these reasons, use of these solid polymeric substances was eventually abandoned.

In the late 1970s, a high-density polyethylene sponge (HDPS) that had nonreactive properties was developed. HDPS has sufficient porosity to encourage tissue ingrowth. The original form was a machined-tooled prosthesis (Plasti-Pore); a more versatile manufactured thermal-fused HDPS (Polycel) arrived later. This latter form permitted coupling with other materials, such as stainless steel, thus lending itself to a wide variety of prosthetic designs. A high incidence of extrusion occurs when either Plasti-Pore or Polycel is placed in contact with the tympanic membrane. Extrusion is reduced considerably when cartilage is placed between a Plasti-Pore or Polycel prosthesis and the tympanic membrane.

Silastic, stainless steel, titanium, and gold are other examples of biocompatible materials used for ossicular reconstruction.

Bioinert implants are materials that do not release detectable trace substances. The prototype bioinert material is dense aluminum oxide ceramic (Al2O3). This material was popular in Germany and Japan in the 1970s. The implant can be fit to the undersurface of the tympanic membrane without cartilage coverage.

Bioactive implants react favorably with the body’s tissues to promote soft tissue attachment. The attachment is a direct chemical bond to the surface of the material, not merely a mechanical attachment that occurs with bioinert and biocompatible materials. Bioactive implants were introduced in the 1970s with the hope that this new material would have a lower incidence of extrusion than the porous polyethylene implants. The first of the bioactive implants were bioactive glasses (Bioglass and Ceravital). Bioactive glasses enjoy limited use today because of the difficulty in trimming the glass prostheses and their instability in infected environments.

Hydroxylapatite is another bioactive material. From a compatibility standpoint, hydroxylapatite is the most promising implant material currently in use. The most common form of hydroxylapatite for middle ear reconstruction is the dense form. The nonporous and homogenous nature of dense hydroxylapatite resists penetration by granulation tissue. This aspect can clearly be seen using scanning electron microscopy. Hydroxylapatite can be placed directly under the tympanic membrane without increased risk of extrusion.

The goal of this article is to review some of the more common materials and techniques for ossicular chain reconstruction currently in use. An exhaustive review of all materials and techniques is not feasible in a single article.

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