Abstract: Distraction rods for use in the treatment of curvature of the spine and comprising an elongated member having a threaded, axial bore therein and an elongated housing into which the elongated member is slidably fitted, the elongated housing having located at one end a connection means for fitting to a clamp for connection to the vertebra, and wherein at the other end of the elongated housing a second connection means for fitting to another clamp for connection to the vertebra is located on one end of the elongated member, said elongated housing having a threaded rod which fits within the bore of the elongated member and engages the threaded bore therein such that the elongated member can move longitudinally along the threaded rod, and hence longitudinally with respect to the elongated housing.