An interbody spinal implant for implantation into a disc space between an upper vertebral body and a lower vertebral body, the implant comprising: a body portion having a proximal first end, an opposite distal second end, a proximal end surface at and adjacent the proximal first end, an upper surface, a lower surface, a first planar lateral side surface, a second planar lateral side surface parallel to the first lateral side surface, and a first mid-longitudinal axis (L 1) extending through the proximal first end and the distal second end of the body portion, the upper surface and the lower surface each being at least in part arcuate in a first plane perpendicular to the first mid-longitudinal axis (L 1), the upper surface and the lower surface each being at least in part arcuate in a second plane extending along the first mid-longitudinal axis (L 1) and perpendicular to the first plane, and the proximal end surface being arcuate in a third plane extending along the first mid-longitudinal axis (L 1) and perpendicular to the first plane; and an extended end portion having a proximal first end, an opposite distal second end, a distal end surface, an upper surface, a lower surface, a first planar lateral side surface, a second planar lateral side surface, and a second mid-longitudinal axis (L 2) extending through the proximal first end and the distal second end of the extended end portion, the proximal first end of the extended end portion being collocated with the distal second end of the body portion, and the second mid-longitudinal axis (L 2) being transverse to the first mid-longitudinal axis (L 1), wherein the upper surface and the lower surface of the body portion being arcuate in the first plane and the second plane provides for biconvex configurations adapted to contact endplates of the upper vertebral body and the lower vertebral body, respectively. a body portion having a proximal first end, an opposite distal second end, a proximal end surface at and adjacent the proximal first end, an upper surface, a lower surface, a first planar lateral side surface, a second planar lateral side surface parallel to the first lateral side surface, and a first mid-longitudinal axis (L 1) extending through the proximal first end and the distal second end of the body portion, the upper surface and the lower surface each being at least in part arcuate in a first plane perpendicular to the first mid-longitudinal axis (L 1), the upper surface and the lower surface each being at least in part arcuate in a second plane extending along the first mid-longitudinal axis (L 1) and perpendicular to the first plane, and the proximal end surface being arcuate in a third plane extending along the first mid-longitudinal axis (L 1) and perpendicular to the first plane; and an extended end portion having a proximal first end, an opposite distal second end, a distal end surface, an upper surface, a lower surface, a first planar lateral side surface, a second planar lateral side surface, and a second mid-longitudinal axis (L 2) extending through the proximal first end and the distal second end of the extended end portion, the proximal first end of the extended end portion being collocated with the distal second end of the body portion, and the second mid-longitudinal axis (L 2) being transverse to the first mid-longitudinal axis (L 1), wherein the upper surface and the lower surface of the body portion being arcuate in the first plane and the second plane provides for biconvex configurations adapted to contact endplates of the upper vertebral body and the lower vertebral body, respectively.