Furlong H-A.C. Femoral Stem

The Furlong®hydroxy-apatite ceramic (H-AC) coated femoral prosthesis was introduced into clinical use in 1985, since which time the geometry of the stem has remained unchanged.

The proximal body of the Furlong®H-AC stem is designed to fit the metaphysis of the femur providing direct contact with the cancellous bone so that following implantation load is transferred to and transmitted by the interface between the prosthesis and the spongiosa.

The rectangular cross section of the proximal body of the prosthesis provides rotational stability under dynamic loading.

The geometrical transition between the proximal body of the stem and the cylindrical distal stem is a cone. The integrity of this prosthesis depends on this unique cone concept. Subsidence of the prosthesis is prevented by the cone which creates “hoopstressing” of the cortical bone and provides early stable mechanical fixation.

The femoral canal distal to the cone is over reamed by 2mm so that it is not in contact with the endosteum. The space around the stem contains osteoblastic cells and these cells, under the influence of osteotropism, form bridging trabeculae vectorially arranged to convey forces between loaded stem and recipient bone. These “cradling” trabeculae are elastic and absorb the inevitable micromovement between the host bone and the stiffer titanium alloy implant. With titanium, new bone formation begins at a distance and only secondarily reaches the implant surface. With hydroxy-apatite ceramic, new bone grows primarily on and directly into the ceramic surface. Bonding osteogenesis on the hydroxy-apatite ceramic surface and reparative osteogenesis on the endosteal bone surface occur simultaneously. This bilateral ossification significantly shortens the time required for osseous bridging between prosthesis and host bone. A fully coated prosthesis ensures even distribution of forces transmitted through the prosthesis to the host bone.

The Furlong® H-AC total hip replacement was the first hydroxy-apatite ceramic coated femoral prosthesis and the combination of the unique geometry to achieve initial primary mechanical fixation, with the hydroxy-apatite ceramic as an intermediary to achieve secondary physiological fixation, has resulted in its well documented clinical success.

While the geometry of the femoral prosthesis has remained unchanged since its inception, the range of stems has been expanded to accommodate a wide spectrum of patients’ anatomical requirements.

Femoral stems are now available in sizes from 8mmto 14mmin 1mm increments, and in sizes 16mm and 18mm. All femoral stems are available in 133° and 140° neck angle and in standard and high offset.

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