Summary
Total hip arthroplasty has gained worldwide acceptance over the last few decades in
humans and in dogs. Although long-term success is high in most studies, aseptic loosening
of components is still a serious complication. Aseptic loosening can affect either
the acetabular or femoral component of both cemented and cementless systems. The process
is usually characterized by an interface membrane which develops between the adjacent
bone and bone cement of the prosthesis, or in cementless components, between the bone
and the implant itself. The process leading to the formation of this interface membrane
and its function is still unclear; although much has been written about this topic
in recent years. Biomechanical factors including: prosthesis design and material composition
and cellular mechanisms such as signaling pathways of cytokines, local mediators or
matrix metalloproteinases, have been incriminated to be responsible for the process.
None of these factors, alone, have been conclusively proven to be the cause of aseptic
loosening.
Aseptic loosening is the major cause of implant failure in total hip arthroplasty.
The controversial aspects of the pathogenesis of the process are reviewed. The role
of biomechanical factors, including prosthesis design, material composition and biological
factors, such as inflammatory mediators, cellular mechanisms, cytokines and matrix
metalloproteinases, are detailed.
Keywords
Aseptic loosening - hip arthroplasty - implant failure
