An implant for expanding a spinal canal, comprising: an upper portion and a lower portion, each having an inner bore (120, 128); an inner member extending into the inner bore (120, 128) of, and interacting with, each of the upper and the lower portions; characterized in that: one swivelable coupling (223, 239) is located within the inner bore (120, 128) of each of the upper and the lower portions, each swivelable coupling (223, 239) communicating with the inner member; wherein: the inner bore of the upper portion defines an implant longitudinal axis; at least one swivelable coupling (223, 239) is retained, fixed from translation along the implant longitudinal axis, relative to the inner bore (120, 128); rotating the inner member about the implant longitudinal axis translates the upper portion away from the lower portion, along the implant longitudinal axis, about a vertebral cut, to widen the vertebral cut, thereby expanding the spinal canal; and each swivelable coupling (223, 239), tiltable relative to the implant longitudinal axis, during an entirety of the translation of the upper portion away from the lower portion along the implant longitudinal axis, angulates the entire inner member relative to the implant longitudinal axis to accommodate a lateral offset of a vertebra occurring during widening of the vertebral cut. an upper portion and a lower portion, each having an inner bore (120, 128); an inner member extending into the inner bore (120, 128) of, and interacting with, each of the upper and the lower portions; characterized in that: one swivelable coupling (223, 239) is located within the inner bore (120, 128) of each of the upper and the lower portions, each swivelable coupling (223, 239) communicating with the inner member; wherein: the inner bore of the upper portion defines an implant longitudinal axis; at least one swivelable coupling (223, 239) is retained, fixed from translation along the implant longitudinal axis, relative to the inner bore (120, 128); rotating the inner member about the implant longitudinal axis translates the upper portion away from the lower portion, along the implant longitudinal axis, about a vertebral cut, to widen the vertebral cut, thereby expanding the spinal canal; and each swivelable coupling (223, 239), tiltable relative to the implant longitudinal axis, during an entirety of the translation of the upper portion away from the lower portion along the implant longitudinal axis, angulates the entire inner member relative to the implant longitudinal axis to accommodate a lateral offset of a vertebra occurring during widening of the vertebral cut. one swivelable coupling (223, 239) is located within the inner bore (120, 128) of each of the upper and the lower portions, each swivelable coupling (223, 239) communicating with the inner member; wherein: the inner bore of the upper portion defines an implant longitudinal axis; at least one swivelable coupling (223, 239) is retained, fixed from translation along the implant longitudinal axis, relative to the inner bore (120, 128); rotating the inner member about the implant longitudinal axis translates the upper portion away from the lower portion, along the implant longitudinal axis, about a vertebral cut, to widen the vertebral cut, thereby expanding the spinal canal; and each swivelable coupling (223, 239), tiltable relative to the implant longitudinal axis, during an entirety of the translation of the upper portion away from the lower portion along the implant longitudinal axis, angulates the entire inner member relative to the implant longitudinal axis to accommodate a lateral offset of a vertebra occurring during widening of the vertebral cut. the inner bore of the upper portion defines an implant longitudinal axis; at least one swivelable coupling (223, 239) is retained, fixed from translation along the implant longitudinal axis, relative to the inner bore (120, 128); rotating the inner member about the implant longitudinal axis translates the upper portion away from the lower portion, along the implant longitudinal axis, about a vertebral cut, to widen the vertebral cut, thereby expanding the spinal canal; and each swivelable coupling (223, 239), tiltable relative to the implant longitudinal axis, during an entirety of the translation of the upper portion away from the lower portion along the implant longitudinal axis, angulates the entire inner member relative to the implant longitudinal axis to accommodate a lateral offset of a vertebra occurring during widening of the vertebral cut.