An implant is a device or tissue placed inside the body or on its surface. A prosthesis replaces a body part. The U.S. Food and Drug Administration, or FDA, describes implants made from materials including metal, plastic and ceramic, as well as body tissues. Understanding an implant involves its material, intended use, surgical risks and the possibility of later problems. Its approval record and information collected after surgery answer different questions. The FDA explains implants and prosthetics.
What premarket approval means
Premarket approval is an FDA review category for medical devices. In its information about metal-on-metal hip implants, the FDA describes approval as a determination that an application contains enough valid scientific evidence to reasonably assure safety and effectiveness for the intended use. That description concerns a defined use. It does not mean that a material name or a general device category establishes suitability for a particular person. The FDA describes the evidence standard.
The FDA’s implant information separately discusses the risks of placing or removing an implant, infection, reactions to materials and implant failure. An implant can move, break or stop working properly, and further surgery may be needed. These general categories give context to an approval record. They also explain why questions about an implant include the planned procedure and later follow-up, rather than approval status alone. The FDA describes implant risks.
What artificial-disc records show
The FDA lumbar artificial-disc record gives a decision date of 10/26/2004 Read the approval record.
The FDA cervical artificial-disc record gives a decision date of 07/16/2007 Read the approval record.
The lumbar record describes the diagnosis and skeletal maturity associated with its stated use. The cervical record concerns disc replacement after disc removal for specified nerve-root or spinal-cord problems. These examples illustrate why a record needs to be read for the condition and location it describes. They are regulatory descriptions rather than a list by which a reader can decide personal eligibility. The lumbar record states the intended use. The cervical record states its intended use.
The records also warn that device descriptions or indications may have changed through supplements. The labeling shown with an original approval may not represent the labeling after later changes. An initial decision date is therefore part of a record, not the complete account of every subsequent change. The history of joint and disc replacement puts regulatory milestones in their broader context. The FDA record explains the labeling limitation.
The FDA’s metal-on-metal hip information
In a metal-on-metal hip implant, the ball and socket surfaces are made of metal. The FDA’s information distinguishes this design from other hip implants and discusses benefits, risks and regulatory requirements. It describes the requirement for premarket approval of metal-on-metal total hip implants. That is a statement about a particular implant category, not a reason to regard every metal component in every joint replacement as the same design. The FDA explains the implant category.
What joint replacement registries collect
A registry brings together information about procedures. The American Academy of Orthopaedic Surgeons’ American Joint Replacement Registry collects hip and knee replacement data from participating care settings. Its stated purposes include informing clinical decisions, assessing quality and patient safety, and supporting research. It describes comparison with national standards and other institutions as a way of examining performance across a wider body of data. The American Joint Replacement Registry explains its purpose.
The UK National Joint Registry describes recording, monitoring, analyzing and reporting performance in joint replacement. It identifies implant and procedure outcomes, data quality and research among its areas of work. These are ways to examine experience across procedures and care settings. Registry information adds a different perspective from the original approval record, which describes a regulatory decision and its stated indications. The National Joint Registry describes its monitoring.
Materials and their response in the body
Materials are part of the implant’s design. The FDA lists metal, plastic and ceramic among implant materials. Polyethylene is a plastic; its ultra-high-molecular-weight form is described in the materials reference as having a history of use in hip, knee and spinal implants. That material description does not establish which design is right for a particular joint or how long an individual replacement will function. The materials reference describes polyethylene use. The FDA lists implant materials.
Biocompatibility means that a material performs with an appropriate response from the body in its intended setting. The reference emphasizes that this depends on the application and that a device may contain different materials. Shape and surface treatment can matter too. Describing a material as compatible therefore needs context rather than being treated as a promise that no reaction or complication can occur. The reference explains why context matters.
How bone can attach to an implant
Osseointegration describes a direct connection between living bone and an implant surface. New bone can form against that surface, creating attachment without a layer of soft tissue between them. This is a biological process as well as a feature of implant design. The description explains the term without setting a timetable for an individual person’s bone attachment or rehabilitation. The reference defines osseointegration.
Bone itself remains active throughout life. The bone-remodeling reference describes the ongoing removal of mature bone tissue and formation of replacement bone, responding in part to mechanical demands. This continuing turnover is different from the material of the implant. Together, the concepts of remodeling and osseointegration help explain why the surrounding living tissue is part of the discussion of fixation and follow-up. The reference explains bone remodeling.
The implant surface and infection
An implant surface can also provide a place where bacteria form a biofilm, a community within a protective surrounding material. A review of prosthetic-joint infection describes biofilms protecting bacteria from antibiotics and the immune response. The biofilm and infection guide explains that process and the clinical assessment of postoperative concerns. This is a separate issue from mechanical wear or the regulatory status of an implant. The implant-infection review describes biofilms. The microbiology review defines the community.