The interface shear strength of uncoated Ti-6Al-4V, dense sintered hydroxyapatite (HA), and HA-coated Ti-6Al-4V were compared. Interface shear strength was determined using a transcortical push-out model in dogs 4 and 12 weeks after implantation. The interface shear strength of dense sintered HA and HA-coated Ti-6Al-4V was significantly higher than that of uncoated Ti-6Al-4V (P < .001). There was no significant difference between the interface shear strength of dense sintered HA and HA-coated Ti-6Al-4V. After the push-out test for HA-coated implants, the regions fractured at the bone-coating interface and at the coating-titanium interface coexisted at 4 weeks after implantation. At 12 weeks, the fracture site was, in all cases, the HA coating-titanium interface, and, in a few samples, fractures inside the coating layer also were visible.
The carcinogenicity and chronic toxicity of 316L stainless steel, nickel, Ti-6A1-4V, hydroxyapatite (HA)-coated Ti-6A1-4V, aluminum oxide containing yttrium oxide, and zirconium oxide containing yttrium oxide were evaluated by implanting solid rods of each material in the thigh muscle of C57BL/6N mice for 24 months. Nickel alloy showed high carcinogenic and toxic potencies, whereas other materials showed no evidence of them. Tumors retaining nickel alloys were malignant fibrous histiocytoma or fibrosarcoma. In some cases, lymphomata that seemed to develop spontaneously were found around the implants because lymphocytes were known to accumulate in chronic inflammatory lesions, and this phenomenon also might be applied to lymphoma.
We have treated osteochondral lesions of the talus using cortical bone pegs. We examined 27 ankles (27 patients) after a mean follow-up of 7.0 years (2 to 18.8). The mean age of the patients was 27.8 years (12 to 62). An unstable osteochondral fragment or osteosclerotic changes in the bed of the talus were regarded as indications for the procedure. The clinical results were good in 24 ankles (89%) and fair in three (11%); none had a poor result. There was also radiological improvement in 24 ankles. Repair of the articular surface and stability of the lesion can be achieved even in unstable chronic lesions.
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