A device to space adjacent vertebral members, comprising: a spacer which comprises a first member having an exterior side with a first contact surface for contacting the one of the adjacent vertebral members, and having an interior side, and a second member having an exterior side with a second contact surface for contacting the other one of the adjacent vertebral members, and having an interior side, the interior sides of the first and second members (20, 30) having first and second ramped surfaces, respectively, positioned at an angle relative to the exterior sides and extending in first and second directions, respectively, so as to mate with each other, and the second member being moveable relative to the first member between a first position with the ramped surfaces being disengaged, and a second position with the ramped surfaces engaged, a height measured between the exterior sides being greater in the second position than in the first position; characterized in that the device further comprises a delivery device connected to one of the first and second members (20, 30) and having an elongated shape to position the spacer between the vertebral members; and a deployer operatively connected to the other one of the first and second members (20, 30) by means of a cam, which cam is positioned within the delivery device and includes a distal end adjacent to the distal end of the delivery device, and a proximal end positioned at the deployer, and which cam is axially movable through the delivery device, to move the other one of the first and second members (20, 30) relative to the one of the first and second members (20, 30) between the first position with the ramped surfaces being disengaged, and the second position with the ramped surfaces engaged, wherein the distal end of the cam contacts a proximal end of the other one of the first and second members (20; 30) to push said one of the first and second members (20; 30) and deploy the spacer, wherein the delivery device is pivotally attached to the one of the first and second members (20, 30) to adjust the angle of the first and second members (20, 30) relative to the delivery device. a spacer which comprises a first member having an exterior side with a first contact surface for contacting the one of the adjacent vertebral members, and having an interior side, and a second member having an exterior side with a second contact surface for contacting the other one of the adjacent vertebral members, and having an interior side, the interior sides of the first and second members (20, 30) having first and second ramped surfaces, respectively, positioned at an angle relative to the exterior sides and extending in first and second directions, respectively, so as to mate with each other, and the second member being moveable relative to the first member between a first position with the ramped surfaces being disengaged, and a second position with the ramped surfaces engaged, a height measured between the exterior sides being greater in the second position than in the first position; characterized in that the device further comprises a first member having an exterior side with a first contact surface for contacting the one of the adjacent vertebral members, and having an interior side, and a second member having an exterior side with a second contact surface for contacting the other one of the adjacent vertebral members, and having an interior side, the interior sides of the first and second members (20, 30) having first and second ramped surfaces, respectively, positioned at an angle relative to the exterior sides and extending in first and second directions, respectively, so as to mate with each other, and the second member being moveable relative to the first member between a first position with the ramped surfaces being disengaged, and a second position with the ramped surfaces engaged, a height measured between the exterior sides being greater in the second position than in the first position; a delivery device connected to one of the first and second members (20, 30) and having an elongated shape to position the spacer between the vertebral members; and a deployer operatively connected to the other one of the first and second members (20, 30) by means of a cam, which cam is positioned within the delivery device and includes a distal end adjacent to the distal end of the delivery device, and a proximal end positioned at the deployer, and which cam is axially movable through the delivery device, to move the other one of the first and second members (20, 30) relative to the one of the first and second members (20, 30) between the first position with the ramped surfaces being disengaged, and the second position with the ramped surfaces engaged, wherein the distal end of the cam contacts a proximal end of the other one of the first and second members (20; 30) to push said one of the first and second members (20; 30) and deploy the spacer, wherein the delivery device is pivotally attached to the one of the first and second members (20, 30) to adjust the angle of the first and second members (20, 30) relative to the delivery device.