[Histopathologic diagnostics in endoprosthetics: periprosthetic neosynovialitis, hypersensitivity reaction, and...

The durability of endoprosthetic implants of the large joints has increased over the last decades. North American studies have shown a 10-year durability of 94% for prosthetic hip implants, and European studies have shown 10-year durabilities of 88-95%. Pathologists differentiate three etiological disease patterns for the"pathology of endoprosthetics" that lead to reduction of implant durability: 1) periprosthetic particle disease (aseptic loosening), 2) infection, and 3) arthrofibrosis. Four types of neosynovitis/periprosthetic membrane have been determined in a consensus classification: particle-induced type (type I), with a mean prosthesis durability (MPD) of 12 years; infectious type (type II), MPD 2.5 years; combined type (type III), MPD 4.2 years; and indeterminate type (type IV), MPD 5.5 years. There are three histopathologic degrees of arthrofibrosis; grade 1 always needs clinical information for diagnosis, whereas grades 2 and 3 are distinct histopathologic entities.