[Morphological-functional characteristic of periarticular tissue after total hip arthroplasty: histological, cytochemical and electron microscopy aspects].

PURPOSE OF THE STUDY Analysis of the tissue harvested around the total hip replacement isolated from re-operated patients in order to: (1) characterize complexity of structural processes developing in the region of the total hip replacement and, (2) to define the role and significance of histological structures of this tissue, mainly in relation to implant loosening, from the viewpoint of formal and causal pathogenesis. MATERIAL AND METHODS Biopsied material isolated from periarticular tissue of re-operated patients (n=19) after THR was analyzed using the methods of light optic, fluorescent (TUNEL), and transmission electron microscopy. RESULTS Histological analysis revealed fibroproliferaive processes and epithelioid granulomatosis cell reaction around the implant with the formation of giant multinuclear syncythial (osteoclastlike) structures as a response to foreign bodies. These structures phagocyte fragments of foreign material (polyethylene particles from the implant, cement fragments). All the used methods revealed a range of regressive changes in the layers of foreign microparticles (inside giant multinuclear cells) typical of fibrinoid necrosis in collagen fibres and apoptosis. In certain cases, progressive changes as chondroid and synovial differentiation (metaplasia) were observed. DISCUSSION Total hip replacement, despite all positive aspects for patients, may cause permanent inflammatory processes in its surrounding. This may result in an extensive fibroproduction of a differently thick layer of connective tissue around the implant. An important factor of loosening of THR is probably osteoclastic resorption in the area of "bone-implant" interface, as a result of the interaction between the inflammatory mechanisms around the implant. CONCLUSION In the postoperative period, there occur fibroproliferative changes in the periarticular tissue and large population of multinuclear cells. In our view, these cells play a role in the production of wear particles from the implant and microparticles of bone tissues and bone cement. Fibroproliferative process may be considered as an immune response to the implanted foreign material.