A spacer (100, 400) for maintaining a separation of vertebrae (10, 12), comprising: - a frame (152, 452) having distal and proximal ends defining a longitudinal axis extending therebetween; - a carriage (156, 456) slideably coupled to the frame (152, 452) and having at least one ramped surface (168, 468), said carriage (156, 456) further including a threaded portion; - an actuator screw (154, 454) threadably engaged with said frame(152, 452), said actuator screw (154, 454) configured to bear against said carriage (156, 456) to cause said carriage (156, 456) to slideably move within said frame (152, 452) when said actuator screw (154, 454) is rotated; - a first endplate (110, 410) configured to engage a first vertebra, and having at least one surface (164, 464) mateable with said at least one carriage (156, 456) ramped surface (168, 468), whereby when said carriage (156, 456) (156, 456) is slideably moveable by rotation of said actuator screw (154, 454), said at least one endplate ramped surface (164, 464) slides against said at least one carriage (156, 456) ramped surface (168, 468) to cause said first endplate (110, 410) to move along an axis transverse to said longitudinal axis to increase a height of the spacer (100, 400); and - a second endplate (112, 412) configured to engage a second vertebra, - characterized in that, said first endplate (110, 410) includes at least one socket through which a polyaxial bone screw may pass to secure said first endplate (110, 410) to a first vertebra, - the socket having a corresponding polyaxial shape to receive the polyaxial screw to provide an optimal angle with respect to said spacer, said socket adapted to overlie a lateral side of a cortical bone of the first vertebra after said spacer is expanded. - a frame (152, 452) having distal and proximal ends defining a longitudinal axis extending therebetween; - a carriage (156, 456) slideably coupled to the frame (152, 452) and having at least one ramped surface (168, 468), said carriage (156, 456) further including a threaded portion; - an actuator screw (154, 454) threadably engaged with said frame(152, 452), said actuator screw (154, 454) configured to bear against said carriage (156, 456) to cause said carriage (156, 456) to slideably move within said frame (152, 452) when said actuator screw (154, 454) is rotated; - a first endplate (110, 410) configured to engage a first vertebra, and having at least one surface (164, 464) mateable with said at least one carriage (156, 456) ramped surface (168, 468), whereby when said carriage (156, 456) (156, 456) is slideably moveable by rotation of said actuator screw (154, 454), said at least one endplate ramped surface (164, 464) slides against said at least one carriage (156, 456) ramped surface (168, 468) to cause said first endplate (110, 410) to move along an axis transverse to said longitudinal axis to increase a height of the spacer (100, 400); and - a second endplate (112, 412) configured to engage a second vertebra, - characterized in that, said first endplate (110, 410) includes at least one socket through which a polyaxial bone screw may pass to secure said first endplate (110, 410) to a first vertebra, - the socket having a corresponding polyaxial shape to receive the polyaxial screw to provide an optimal angle with respect to said spacer, said socket adapted to overlie a lateral side of a cortical bone of the first vertebra after said spacer is expanded.