7. A method of exerting a distraction force on a spine, the method comprising: securing a first rod anchor on a first side of the spine to a first vertebra and a second rod anchor on the first side of the spine to a second vertebra; receiving a first portion of a rod in the first rod anchor and a second portion of the rod in the second rod anchor such that the first portion is substantially constrained against lateral translation and the second portion is substantially constrained against lateral translation, the first and second portions being able to change in pitch and yaw at the first and second rod anchors, respectively, in response to movement of the spine during a correction; locating a first stop feature along the rod at a first position adjacent the first rod anchor and a second stop feature along the rod at a second position adjacent the second rod anchor; and imposing a compressive force on the rod with the first and second stop features.
7. A method of exerting a distraction force on a spine, the method comprising: securing a first rod anchor on a first side of the spine to a first vertebra and a second rod anchor on the first side of the spine to a second vertebra; receiving a first portion of a rod in the first rod anchor and a second portion of the rod in the second rod anchor such that the first portion is substantially constrained against lateral translation and the second portion is substantially constrained against lateral translation, the first and second portions being able to change in pitch and yaw at the first and second rod anchors, respectively, in response to movement of the spine during a correction; locating a first stop feature along the rod at a first position adjacent the first rod anchor and a second stop feature along the rod at a second position adjacent the second rod anchor; and imposing a compressive force on the rod with the first and second stop features. 8. The method of claim 7 , further comprising distracting the first side of the spine.