Material properties of and tissue reaction to the Slocum TPLO plate

OBJECTIVE: To determine the material properties of Slocum TPLO plates and assess the soft tissue reaction adjacent to these plates in dogs that had undergone tibial plateau leveling osteotomy (TPLO). SAMPLE POPULATION: 3 new TPLO plates, 8 retrieved TPLO plates, and 1 new Synthes dynamic compression plate. PROCEDURES: Metallurgic analyses were performed. Tissue samples were obtained from areas adjacent to retrieved plates and submitted for histologic examination. RESULTS: All of the TPLO plates had a 2-phase microstructure consisting of austenite and ferrite in various amounts. Residua, inclusions, and cavities were seen during microscopic examination of the plate surface. The major differences between new and retrieved TPLO plates were the presence of small gaps separating many inclusions from the surrounding matrix and the presence of various-sized pits on the surface of the retrieved plates. The dynamic compression plate had a nearly pure austenitic structure and was largely free from residua, inclusions, and cavities. Histologic examination of tissue samples obtained from areas adjacent to retrieved TPLO plates revealed intra- and extracellular particulate debris. Two types of particles (one consisting of chromium, nickel, molybdenum, and iron and the other consisting of aluminum and silicon) were seen. CONCLUSIONS AND CLINICAL RELEVANCE: Results determined that new and retrieved TPLO plates were manufactured from 316L stainless steel and produced by a casting process, but not all plates met specifications for chemical composition of cast surgical implants (American Society for Testing Materials standard F745); tissues surrounding retrieved plates had evidence of adverse reactions, probably as a result of plate corrosion.