An implantable device includes a polymeric body and a metallic first mounting strip connected to a trailing end portion of the body. The body has a leading end portion, a first side surface, a second side surface, an upper surface, a lower surface and a central opening extending through the upper and lower surfaces. The central opening has an internal surface with an internal leading surface, a first internal side surface and a second internal side surface. A first depth is defined between the leading end and the internal leading surface, a first spacing is defined between the first side surface and the first internal side surface and a second spacing is defined between the second side surface and the second internal side surface. The first spacing is substantially the same as the second spacing and the first depth is less than the first spacing.
