9.2.1 Migration of Molecules(Soluble)and Particles(Insoluble); Lymphatic System Local and regional lymphadenopathy caused by wear particles released from joint replacement prostheses is becoming increasingly recognized as a possible complication of arthroplasty. Particles generated by mechanical wear of prostheses can leave the site of the implant via the lymphatics and become engulfed by macrophages within local and regional lymph nodes. Accumulation of cells containing particles causes enlargement of the lymph node and the characteristic histologic appearance of sinus histiocytosis. Distension and prominence of the lymphatic sinuses is due to the presence of large numbers of a) histiocytes derived from the cells that line the sinuses or b) macrophages derived from circulating monocytes. Multinucleated giant cells, resulting from the fusion of macrophages or histiocytes, might also be found in the dilated Sinuses nodes draining joints replaced with prostheses has been found in animal 3, 24 and huma ph Accumulation of polyethylene, polymethylmethacrylate, and metal particles in lymp studies2,3, 8, 12, a few of which have reported lymphadenopathy in operative patients, 15, 20.Total joint prostheses produce particulate debris through adhesive, abrasive, and fatigue( delamination) wear processes occurring 1)at the articulating interface between metal and polyethylene, 2) at the junctions of the modular portions of a modular total joint prosthesis, 3)at the interface between component and cement, or 4)at the interface between implant and bone. Polyethylene, polymethylmethacrylate, and metal particles are all capable of stimulating resorption of periprosthetic bone, 4. 9, 10), 16, 1 8, 19,21,25.,26. The adverse consequences of periprosthetic bone loss have focused a great deal of attention on the problems caused by wear particles locally at the implant-bone interface. Much less attention has been focused on the pathologic response to these particles at distant sites in the body The tissue response to wear particles is that of a foreign body reaction, with varying amounts of macrophages and foreign body giant cells, 24, 28. Synovial macrophages readily engulf particles released into the joint space. When the production of particulate debris exceeds the phagocytic capacity of synovial macrophages, excess particles a) migrate into periprosthetic tissue where they are ultimately phagocytosed by macrophages, that release agents that stimulate bone resorption, or b)enter lymphatic vessels. There is evidence that macrophages laden with partcles can also gain entry to the lymphatics. Macrophages present within lymph nodes endocytose free particles traveling within the lymphatic system. A steady influx of wear debris causes these macrophages to accumulate within the sinus of the lymph node. Over several years macrophages containing particles may become so abundant that they cause dilatation of nodal sinuses and node enlargement. The accumulation of histiocytes or macrophages within lymph node sinuses is described pathologically as sinus histiocytosis. The histopathologic response to polyethylene particles in lymph nodes and periprosthetic tissue is comparable. At both sites macrophages containing polyethylene have abundant, granular, eosinophilic cytoplasm, with small central nuclei. Polyethylene particles smaller than three micrometers are seen within individua cells, while larger particles are surrounded by foreign body giant cells9.2.1 Migration of Molecules (Soluble) and Particles (Insoluble); Lymphatic System Local and regional lymphadenopathy caused by wear particles released from joint replacement prostheses is becoming increasingly recognized as a possible complication of arthroplasty. Particles generated by mechanical wear of prostheses can leave the site of the implant via the lymphatics and become engulfed by macrophages within local and regional lymph nodes. Accumulation of cells containing particles causes enlargement of the lymph node and the characteristic histologic appearance of sinus histiocytosis6. Distension and prominence of the lymphatic sinuses is due to the presence of large numbers of a) histiocytes derived from the cells that line the sinuses or b) macrophages derived from circulating monocytes. Multinucleated giant cells, resulting from the fusion of macrophages or histiocytes, might also be found in the dilated sinuses. Accumulation of polyethylene, polymethylmethacrylate, and metal particles in lymph nodes draining joints replaced with prostheses has been found in animal13,24 and human studies2,3,8,12, a few of which have reported lymphadenopathy in operative patients6,15,20. Total joint prostheses produce particulate debris through adhesive, abrasive, and fatigue (delamination) wear processes occurring 1) at the articulating interface between metal and polyethylene, 2) at the junctions of the modular portions of a modular total joint prosthesis, 3) at the interface between component and cement, or 4) at the interface between implant and bone . Polyethylene, polymethylmethacrylate, and metal particles are all capable of stimulating resorption of periprosthetic bone1,4,9,10,16,18,19,21,25,26 . The adverse consequences of periprosthetic bone loss have focused a great deal of attention on the problems caused by wear particles locally at the implant-bone interface. Much less attention has been focused on the pathologic response to these particles at distant sites in the body. The tissue response to wear particles is that of a foreign body reaction, with varying amounts of macrophages and foreign body giant cells8,24,28. Synovial macrophages readily engulf particles released into the joint space. When the production of particulate debris exceeds the phagocytic capacity of synovial macrophages, excess particles a) migrate into periprosthetic tissue where they are ultimately phagocytosed by macrophages, that release agents that stimulate bone resorption19, or b) enter lymphatic vessels25. There is evidence that macrophages laden with partcles can also gain entry to the lymphatics7. Macrophages present within lymph nodes endocytose free particles traveling within the lymphatic system. A steady influx of wear debris causes these macrophages to accumulate within the sinus of the lymph node3. Over several years macrophages containing particles may become so abundant that they cause dilatation of nodal sinuses and node enlargement. The accumulation of histiocytes or macrophages within lymph node sinuses is described pathologically as sinus histiocytosis. The histopathologic response to polyethylene particles in lymph nodes and periprosthetic tissue is comparable. At both sites, macrophages containing polyethylene have abundant, granular, eosinophilic cytoplasm, with small central nuclei. Polyethylene particles smaller than three micrometers are seen within individual cells, while larger particles are surrounded by foreign body giant cells22