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Prosthetic Components

Obviously, the end-stage management of many of these cartilage lesions is a replacement procedure; however, in many situations the diseased portion is a limited area that is amenable to a limited replacement approach. Several devices are currently available, some experimental and some recently devised that allow for this limited resurfacing.

The currently available device is a titanium coated shaft portion with an articular bearing surface of a cobalt-chrome alloy (Arthrosurface; Franklin, MA). The device is implanted in the central articular defect either in an open or arthroscopic fashion and recreates the circumference of the humerus . Several sizes of implants are available such that a circular defect up to 40 mm can be reconstructed. To date, there are no series of patients available that have been published in the peer-reviewed literature.

A variety of synthetic “articular cartilage-like” materials are also available. All of the devices are currently unavailable in the United States but are presently in use in some European countries and Japan. Again, the experience has been predominantly in the knee joint with an occasional series or case report in other joints such as the hip, ankle, or shoulder.

The majority of the materials are hydrogels which are encapsulated and typically contain a suspension of saline with a variety of macromolecules that simulate the properties of articular cartilage .

In a study evaluating the response of normal cartilage to the hydrogels vs. aluminum and titanium implants in a rabbit model, there were marked pathologic changes noted on the knees with the harder implants, although the knees with the hydrogel implants had none to minimal changes .

This supports some of the well-known literature on the use of hemiprosthetics in the shoulder and knee joint where degradation of the articular surfaces has been documented with long-term follow-up of these patients.

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