System, including apparatus and methods, for ankle fusion using a device for separating a first bone and a second bone of an ankle region. In some embodiments, the device may comprise an expandable spacer including first and second bone-contacting surface regions facing away from one another and configured to be abutted with the first and second bones, respectively. A distance between the first and second bone-contacting surface regions may be adjustable to change the separation of the first and second bones. The first bone-contacting surface region may correspond to a portion of a sphere and may be configured to be disposed at least partially in a concavity formed surgically in the first bone. The expandable spacer offers improved control over the length of the lower limb and the orientation of the foot during ankle fusion surgery.
