Corrosion and Tribology of Materials Used in a Novel Reverse Hip Replacement.

Total hip arthroplasty has been utilized for the past 50 years as an effective treatment for degenerative, inflammatory and traumatic disorders of the hip. The design of these implants has generally followed the anatomy of the hip as a ball and socket joint with the femoral head representing the ball and the acetabulum representing the socket. We describe a novel hip arthroplasty design in which the "ball" is located on the acetabular side and the "socket" is located on the femoral side. The results of extensive biomechanical testing are described and document wear and corrosion characteristics that are at least equivalent to standard designs. These results support clinical assessment as the next step of the evaluation.

Maintenance of a functional endothelial cell monolayer on a fibroblast/polymer substrate under physiologically relevant shear stress conditions.

The suitability of using a fibroblast-seeded polymer scaffold as a substrate for forming an endothelial monolayer which is responsive to flow has been investigated. The results indicate that a confluent monolayer of endothelial cells can be formed on the top surface of the fibroblast/polymer substrate. This monolayer has an elongated, oriented morphology and alignment even in static culture, and the application of shear stress perpendicular to the endothelium's static alignment causes a progressive reorganization of the cytoskeletal component, F-actin, with a corresponding change in endothelial cell shape from elongated in the direction of flow, to a more "cobble-stone" morphology, to finally elongation in the direction of flow. The production of nitric oxide by this co-culture increases not only in a time and shear stress dependent fashion, but also as a function of the direction of flow in relation to the static alignment of the endothelium. The data obtained also indicate that the coculture had higher levels of ICAM-1 production and monocyte adhesion than seen in ECs on tissue culture plastic, which may be a function of the endothelial cells being in direct contact with the fibroblast cell line. These results demonstrate that a fibroblast/polymer scaffold can serve as a suitable substrate for ECs and that such a monolayer demonstrates the normal EC responsiveness to flow.