L. Nordsletten et al., THE PLASMINOGEN ACTIVATION SYSTEM IS UP-REGULATED IN LOOSENING OF TOTAL HIP PROSTHESES, Acta orthopaedica Scandinavica, 67(2), 1996, pp. 143-148
Interface tissues and pseudocapsules from loose total hip replacements
were removed during revision of 11 cases and were investigated for th
e plasminogen activation system and IL-1 beta. Control samples of syno
vium were taken during knee arthroscopy (n 8), and from the hip joint
during primary total hip replacement (n 5). The concentrations of urok
inase plasminogen activator (uPA), tissue type plasminogen activator (
tPA), plasminogen activator inhibitor-1 (PAI-1) and interleukin 1 beta
were all found to be significantly different in interfaces and in pse
udocapsules, compared to controls. Immunohistochemistry disclosed loca
lization in periprosthetic tissues of uPA, uPA-receptor and tPA in mac
rophages with phagocytosed metal, polyethylene, cement particles or ac
companying pieces of necrotic bone. PAI-1 staining was present in the
neighboring areas that stained for uPA or tPA, but PAI-1 staining was
also found overlapping and outside these areas. These findings suggest
a role for the UPA/UPA-receptor and PAI-I in activation and focalizat
ion of extracellular matrix degradation in periprosthetic tissues. The
expression of the plasminogen activation system by macrophages contai
ning phagocytosed material suggests undegradable microdebris as a poss
ible initiating and perpetuating stimulus for a proteolytic activation
cascade, which may contribute to loosening of the prosthesis.