injection) and were effectively filtered by the lungs, thus preventing dissemination in the arterial system. No migration of particles from the femur into the lymphatic system was found after four days. However, similar microspheres injected into soft tissue in the distal femur were found in the iliac lymph nodes in two of nine animals after this time period. In neither of these animals were particles found in the lungs. A subsequent study demonstrated that particles as large as 100 micrometers, injected into the canal of the distal femur, migrated to the lungs within fifteen minutes of injection. These results suggest that under certain conditions particles generated by wear might directly enter the venous system. The majority of these particles would be filtered in the lung, preventing hematogenous spread. Collectively the investigations indicate that a marked number of particles can be disseminated to various sites in the body within hours after their generation. Clinical Implications Lymphadenopathy secondary to the accumulation of wear particles in sinus macrophages may cause confusion regarding the appropriate diagnosis, especially in cases where malignancy is suspected. Shinto, et al., recently reported a case of a nineteen year-old man who presented with right inguinal pain and a three x three centimeter palpable mass, three years after placement of a right total knee replacement following resection of an osteosarcoma. The lymph node was biopsied to evaluate for suspected metastatic recurrence of osteosarcoma. Histologic examination revealed sinus histiocytosis due to metal particles released from the knee prosthesis. There was no evidence of malignancy The ultimate fate of particles released from total joint prostheses is unknown. A recer report suggests that metallic particles from orthopedic prostheses may pass through the lymphatics and gain a systemic distribution. The clinical sequelae of polyethy lene particles in lymph nodes and other organs is unknown. However, the fact that disseminated polyethylene particles cannot be removed focuses attention on investigations of the long term host response to polyethylene particlesinjection) and were effectively filtered by the lungs, thus preventing dissemination in the arterial system. No migration of particles from the femur into the lymphatic system was found after four days. However, similar microspheres injected into soft tissue in the distal femur were found in the iliac lymph nodes in two of nine animals after this time period. In neither of these animals were particles found in the lungs. A subsequent study11 demonstrated that particles as large as 100 micrometers, injected into the canal of the distal femur, migrated to the lungs within fifteen minutes of injection. These results suggest that under certain conditions particles generated by wear might directly enter the venous system. The majority of these particles would be filtered in the lung, preventing hematogenous spread. Collectively the investigations indicate that a marked number of particles can be disseminated to various sites in the body within hours after their generation. Clinical Implications Lymphadenopathy secondary to the accumulation of wear particles in sinus macrophages may cause confusion regarding the appropriate diagnosis, especially in cases where malignancy is suspected. Shinto, et al., recently reported a case of a nineteen year-old man who presented with right inguinal pain and a three x three centimeter palpable mass, three years after placement of a right total knee replacement following resection of an osteosarcoma20. The lymph node was biopsied to evaluate for suspected metastatic recurrence of osteosarcoma. Histologic examination revealed sinus histiocytosis due to metal particles released from the knee prosthesis. There was no evidence of malignancy. The ultimate fate of particles released from total joint prostheses is unknown. A recent report suggests that metallic particles from orthopedic prostheses may pass through the lymphatics and gain a systemic distribution12. The clinical sequelae of polyethylene particles in lymph nodes and other organs is unknown. However, the fact that disseminated polyethylene particles cannot be removed focuses attention on investigations of the long term host response to polyethylene particles