An expandable interbody implant adapted for insertion at least into a disc space, between two adjacent vertebrae of a spine. An upper member and a lower member are pivotally connected at least by a drive link. A bone graft storage portion packed with a selected volume of bone growth material. A translational wall is provided between the bone graft storage portion and a trailing end of the implant. An actuator engages the bone graft storage portion, pushing it forward into engagement with the drive link, which pivots upward, moving the upper member upward away from the lower member. Upward movement of the upper member raises the translational wall to a position to assist in retention of the selected volume bone graft material within the hollow portion of the bone graft storage portion. Upward rotation of the drive link brings a face thereof into contact with a front of the bone graft storage portion, thereby retaining near constant volume of the bone graft material.