The effect of implant modification: the low contact stress experience.

AIMS: The aim of this study was to conduct the largest low contact stress (LCS) retrieval study to elucidate the failure mechanisms of the Porocoat and Duofix femoral component. The latter design was voluntarily recalled by the manufacturer. MATERIALS AND METHODS: Uncemented LCS explants were divided into three groups: Duofix, Porocoat, and mixed. Demographics, polyethylene wear, tissue ingrowth, and metallurgical analyses were performed. RESULTS: In 104 implants, a decrease in the odds of loosening and an increase in metallosis and tissue staining in the Duofix group relative to Porocoat group was detected (p = 0.028). There was an increased presence of embedded metallic debris in the Duofix group (p < 0.001). Decreased tissue ingrowth was associated with the Duofix surface (p < 0.001). The attached beads had reduced microhardness, indicative of adverse thermal processing, which resulted in bead shedding, particulate debris, and metallosis. CONCLUSION: Hydroxyapatite coating of the LCS femoral component produced unexpected results and led to its recall. The root cause was likely a combination of retained alumina grit and a reduction in bead microhardness (mechanical strength) resulting in increased particle debris, metallosis, and early revision. The Duofix LCS femoral component was not equivalent to the Porocoat version despite its approval through the Food and Drug Administration (FDA) 510(k) equivalance approval process. Regulation of the introduction of modified existing devices needs to be improved and the Duofix LCS should have been considered to be a new device for which equivalence had not been demonstrated at the point of introduction. Cite this article: Bone Joint J 2019;101-B:1248-1255.

Fetus in fetu: presentación de un caso y revisión de la literatura / Fetus in fetu: presentation of case and review

Se reportó el caso de una paciente femenina de 3 meses de edad referida de la ciudad de La Ceiba, con historia de un mes de evolución de vómitos post-prandiales y distensión abdominal. En la última semana la madre nota tumoración en hipocondrio derecho. La tomografía axial computarizada reporta tumoración heterogenea de 12.1 cm x 8.8 cm con múltiples calcificaciones en su interior compatible con teratoma. Durante la intervención quirúrgica se realizó el diagnóstico de "Fetus in Feto" el cual fue confirmado por patología. "Fetus in fetu" es una anormalidad congenita in-usual, existen 80 casos reportados en todo el mundo y este es el primer caso reportado en nuestro país