Overview of Joint Replacement Hardware
|This overview section describes
general characteristics applicable to joint replacement hardware at any
anatomic site. For a specific joint, click an entry on the left.
A joint replacement can be classified as a total joint arthroplasty, a hemi-arthroplasty, or a resurfacing technique. The last is rarely performed in the United States and is not further discussed. A prosthesis replacing one side of a joint can be a single piece (monoblock) or modular in which the prosthesis has interchangeable parts. The prosthesis in a hemiarthoplasty can have a unipolar or bipolar design. This is especially common with femoral head prostheses. A unipolar prosthesis articulates with the nonreplaced native joint surface. In a bipolar design, the prosthesis has an additional across the joint component with which it articulates, but this component does not replace the joint surface. Click the Hips link for further discussion.
The FDA classifies joint prostheses by the degree to which normal joint motion is restricted. An implant that is free to move in all planes is referred to as an unconstrained prosthesis. An implant that allows free motion in one plane and limits, but does not prevent, motion is the other planes is referred to as semiconstrained. A constrained prosthesis allows motion in only one plane and no motion in other planes. Constrained prostheses have flexible, across the joint, linking components.
Other methods of classifying joint replacement hardware include composition (metal, polymer, composite, ceramic) and cement or noncemented.
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