Evaluation of fracture stability. A mechanical simulator for assessment of clinical judgement.

To test the surgeon's clinical ability to detect small movements in fractures, a simulator with elastic behaviour was constructed. The bending moment required to produce a certain deflection was adjusted at four different levels. With the lowest stiffness, all surgeons in the test series reported that the fracture was unstable at a deflection of 3-4 degrees. With increasing stiffness, an increase in stability was reported--the registered deflection, however, was always 3-4 degrees. These observations confirm that manual tests of fracture stability are uncertain.