Identification and distribution of synthetic ligament wear particles in sheep

After one year, wear of medial collateral ligament replacements in sheep resulted in the presence of large numbers of wear particles and fibers in the joint space. This study examined the frequency of transport of these particles to the regional lymph nodes and to the liver and spleen. Inguinal, iliac, and paraaortic nodes were examined with regular and polarized light for the presence of particles presumably originating from polyethylene, aramid, polytetrafluoroethylene, polyesterterephthalate, polylacticacid, and carbon ligaments. Lymph nodes from sheep that had received tendon autograft replacements were also evaluated. Particles were observed in 33% of all nodes and in at least one node in 84% of all sheep. Particles were found in contralateral nodes, but not in the spleen or liver. Particles were observed usually as intracellular in foamy histiocytes, although extracellular carbon fibers and extracellular aramid fibers were also seen. Giant cells were occasionally detected in the polytetrafluoroethylene, polyethylene, and aramid nodes. In the polytetrafluoroethylene nodes and in the autograft nodes particles containing Mg, Si, and Fe were identified by elemental analysis. The morphological similarities between various birefringent particles and the particles indirectly identified as talc have led us to question the identification of wear debris solely on the basis of birefringence.