GELATINASE TYPE-IV COLLAGENASES IN THE LOOSENING OF TOTAL HIP-REPLACEMENT ENDOPROSTHESES

Gelatinase/Type IV collagenases, namely, 72 kDa matrix metalloproteina se (MMP)-2 type and 92 kDa MMP-9 type, were analyzed to evaluate the r ole of extracellular matrix degradation in 17 cases of loosening of to tal hip endoprostheses. Zymographic and densitometric analyses reveale d elevated production of MMP-2 and induction of MMP-9 in tissue extrac ts from both the interface tissues between bone and implants and the p seudocapsular tissues around the loose endoprostheses when compared wi th those of 8 control noninflammatory knee synovial tissues. The level of MMP-9 was higher in the interface tissues than in the pseudocapsul ar tissues. MMP-9 activity was not detected in the control samples. Al though differences in the type of prosthetic fixation (cemented versus cementless) or the type of alloy (cobalt-chromium-molybdenum versus t itanium-aluminum-vanadium) existed, they shared a similar potential to stimulate tissues to produce MMP-2 and MMP-9. These findings suggest a role for MMP-2 and MMP-9 type gelatinase/Type IV collagenases in the degradation of extracellular matrix of periprosthetic tissues, where they may cause weakening of the connective tissue bed and the loosenin g of total hip replacement endoprostheses. The pseudocapsular tissues could contribute to the loosening via the production and release of ma trix metalloproteinases into the synovial fluid. Alternatively, induct ion of matrix metalloproteinases in such tissues may reflect remodelin g of the pseudocapsular connective tissues.