A variable length fixation device for insertion into a hole formed in two or more bone fragments has a barrel portion and a fastener element. The barrel portion is secured to an inside surface of the hole in a proximal one of the bone fragments. The fastener element is telescopically mounted to the barrel portion and is extendable into a distal one of the bone fragments. The assembly prevents lateral movements of the distal fragment, relative to the proximal fragment, while allowing axial relative movements (i.e., linear movements along the longitudinal axis of the fastener element) to occur. In a preferred embodiment, the fastener element is a cannulated bone screw having a hex-shaped cross-section on one end which is telescopically received into a hex-shaped interior of the hollow barrel portion. The two components are preferably permanently joined to form a one-piece assembly having a variable overall length. The fixation device of the present invention is substantially insertable in its entirety into the hole which extends across the fracture site, and may be installed with a minimal amount of trauma and damage to surrounding bone and soft tissues.