Table 1.

Definition of the histological types of periprosthetic membranes (Krenn and Morawietz et al.)

Type	Characteristics
Type I – Periprosthetic membrane of the wear particle induced type	Infiltration of predominantly macrophages and multinuclear giant cells containing PE particles
Type II – Periprosthetic membrane of the infectious type	Activated fibroblasts, proliferation of small blood vessels, oedema, and inflammatory infiltrate of neutrophilic granulocytes
Type III – Periprosthetic membrane of the combined type	Combination of the histomorphological changes described for types I and II
Type IV – Periprosthetic membrane of the indeterminate type (non infected, non wear particle induced)	Connective tissue low in cells and rich in collagen fibres