An intervertebral articulating prosthetic device having a longitudinal axis, a transverse axis and a vertical axis, and comprising: an upper component, a lower component, and an articulating central portion between the upper and lower components (22, 24), by means of which the upper and lower components (22, 24) are moveably engaged with each other, the upper component having a first engagement surface and a first engagement structure having a pair of opposite surfaces (48, 50), separated by a width, and extending from the first engagement surface at a first oblique angle between the first engagement structure and the first engagement surface, and comprising a single flange member or keel extending substantially across the first engagement surface in a direction substantially along the transverse axis, the first engagement structure, along the longitudinal axis, being approximately centrally located along the corresponding longitudinal dimension of the device and being configured for disposition within a preformed opening in an adjacent vertebral endplate; and the lower component having a second engagement surface and a second engagement structure having a pair of opposite surfaces (60, 62) separated by a width and extending from the second engagement surface at a second oblique angle about the transverse axis and comprising a single flange member or keel extending substantially across the second engagement surface in a direction substantially transverse to the longitudinal axis and extending from the second engagement surface at a second oblique angle about the transverse axis, the second engagement structure being approximately centrally located along the longitudinal axis and being configured for disposition within a preformed opening in an adjacent vertebral endplate. an upper component, a lower component, and an articulating central portion between the upper and lower components (22, 24), by means of which the upper and lower components (22, 24) are moveably engaged with each other, the upper component having a first engagement surface and a first engagement structure having a pair of opposite surfaces (48, 50), separated by a width, and extending from the first engagement surface at a first oblique angle between the first engagement structure and the first engagement surface, and comprising a single flange member or keel extending substantially across the first engagement surface in a direction substantially along the transverse axis, the first engagement structure, along the longitudinal axis, being approximately centrally located along the corresponding longitudinal dimension of the device and being configured for disposition within a preformed opening in an adjacent vertebral endplate; and the lower component having a second engagement surface and a second engagement structure having a pair of opposite surfaces (60, 62) separated by a width and extending from the second engagement surface at a second oblique angle about the transverse axis and comprising a single flange member or keel extending substantially across the second engagement surface in a direction substantially transverse to the longitudinal axis and extending from the second engagement surface at a second oblique angle about the transverse axis, the second engagement structure being approximately centrally located along the longitudinal axis and being configured for disposition within a preformed opening in an adjacent vertebral endplate.