PROSPECTS FOR NONSURGICAL INTERVENTION IN ARTIFICIAL JOINT LOOSENING

Aseptic failure of total hip and other arthroplasties due to osteolysi s is of significant concern to the orthopaedic surgeon. We now think w e know how this osteolysis occurs. Wear particles produced from prosth etic joints interact with macrophages and stimulate the production of mediators which induce bone loss. There is now the prospect of inhibit ing this process by treatment with drugs. Recent studies carried out i n vitro and in animal models have identified three potential sites at which drugs would prevent wear particle induced bone loss. 1. Inhibiti on of the initial interaction of wear particles and macrophages by dru gs such as chloroquine and bafilomycin. 2. Inhibition of the release o f bone resorbing mediators from macrophages by antiinflammatory drugs such as piroxicam, naproxen and pentoxyphyline. 3. Inhibition of the e ffects of bone resorbing mediators by drugs such as pamidronate. The u se of these types of treatments will ultimately depend on comparing th e possible adverse effects with the benefits which the treatments migh t attain. While drug treatment can now be considered for patients with radiological evidence of early bone loss surrounding the prosthesis, prophylactic treatment in patients with stable implants may eventually emerge as a possibility.