[Partial replacement of obsolete prosthetic implants]

Thanks to better technique for cemented prostheses or to better osteointegration of porous coated implants, a long term survival can be expected for joint prostheses. Wear of the bearing surfaces resulting in osteolysis, metallosis and even rupture has become the main threat after several years. In such cases, revising all the parts of a stable and well fixed implant may cause fractures, loss of bone and thus need an extensive reconstruction. Revising only the worn out parts might be preferable, provided that they still are available. Data collected by the SFHG (French Hip and Knee Society) and AVIO group show that 45% of hip revisions and 16% of knee revisions are partial ones. The need for a total exchange instead of a partial one appeared in 6.4% of knee revisions and 2.8% of hip revisions, because parts were no longer available. These problems linked to a longer life expertancy of the patients and the increasing number of hip and knee arthroplasties will be met more and more often by orthopedic surgeons. When parts identical to the worn out ones are still on the market, there is no problem. When their production has been given up, but the company has kept their references and accepts to make a single element it may be possible to obtain the missing unit. The increased cost of such a fabrication, however is not nowadays supported by an appropriate price. But in a few remaining cases without enough industrial references, a custom-made part had to be done to allow partial replacement, with the benefit of an adapted price. Care must be taken to observe the regulations. The surgeon endorses full responsibility not only for the surgical procedure but also for the choice of the implanted device. For custom-made products he is responsible for the technical data given to the company. The patient must be thoroughly informed, and his opinion taken into account in the operative decision. As a revision arthroplasty aims at restoring a good function, the procedure should suit best the patient's health condition and try and avoid any hazard. Rejecting the option of partial replacement just because of parts unavailability is not acceptable when it seems the safest way to get the best result. Help can come from orthopedic surgeons themselves, if they give to their patient precise reports on the primary arthroplasty. The technical references of all the devices devoted to joint arthroplasty should not only be collected by public health services (AFSSAPS) but they should also be available to orthopedic surgeons. The real production cost of prosthetic elements should be taken into account in order to encourage the companies to deliver parts that are not on the market anymore.