A unilateral external fixator device that allows for gross manipulation and fine adjustment of deformities in six degrees of freedom. The device may comprise a strut assembly and two compound movable joints, one at each end of the strut assembly. One compound movable joint may comprise two revolute joints, each containing a gear reduction mechanism and may rotate about the strut. The second compound movable joint may contain two revolute joints, each containing a gear reduction mechanism, and may move along the length of the strut assembly. The gear reduction mechanisms may comprise helical spline assemblies that allow for gross and fine adjustment of the fixator.