Five different methods of Colles' fracture fixation were studied to determine their stability while simulating early post-operative movement in an in-vitro model. Eight previously frozen cadaveric upper extremities were mounted in a computer-controlled wrist loading apparatus. This device was used to generate finger, wrist, and forearm motions through loading relevant tendons. An unstable Colles' fracture was simulated by removing a dorsally-based wedge from the distal radius metaphysis. An electro-magnetic tracking system measured fragment motion following block randomized application of a Hoffman external fixator, Hoffman external fixator plus styloid pins, dorsal Pi plate, dorsal AO plate, and a hybrid ring external fixator. Regardless of the fixation technique used in this unstable fracture model, fragment motion occurred when post-operative finger, wrist, and forearm motions were simulated, with forearm rotation being the most provocative motion studied. The Hoffman external fixator did not provide adequate fixation in this model, but the addition of styloid pins significantly improved fracture stability and approached that achieved with the AO plate. The Pi plate and hybrid ring external fixator were both comparable to the AO plate in terms of fracture stability provided.