External fixators for wrist fractures: a biomechanical and clinical study

The rigidity of four external fixators for the wrist was determined by using the Instron universal testing instrument. Using the equivalent stiffness index, the small A.O. was 7.6, the mini Hoffman was 3.7, Roger Anderson was 3.5, and Ace Colles' was 4.3. Thus, the small A.O. was about twice as rigid overall as the other three external fixators. Twenty-two patients with unstable distal radius fractures were treated with the mini Hoffman external fixator over a 3-year period; and follow-up data were obtained. The average final angle of the distal radial articular surface on the anteroposterior x-ray film was 17.5 degrees. The final angle of the distal radial articular surface on the lateral x-ray film was 2 degrees dorsal. The final height of the distal radial styloid averaged 8 mm. The final range of motion of the wrist compared with the opposite normal hand was extension 77%, flexion 77%, ulnar deviation 82%, radial deviation 73%, pronation 84%, supination 78%, and grip strength 72%. Complications included three cases of broken pins, one of a pin loosening with migration, one case of tendon rupture, and one of intrinsic contracture. From our experience, the Hoffman external fixator gave adequate clinical and functional results and can be used safely in the small to average size patient. A more rigid external fixator should be used for larger and more active patients. External fixation is an excellent way to treat unstable distal radial fractures.