[Results of biomechanical studies of various external fixation devices of the pelvis]

Various mounting systems used in fixation of the pelvis were tested for their stability. The systems were mounted on macerated pelvices and their firmness examined. The criterion for the examination was on the one hand the force needed under distraction to cause a distension in the region of the symphysis or of the sacroiliac joint of 1 cm., on the other hand the force needed to tilt the disjunction points for 1 cm. when shearing takes place. It was concluded from the study that in clinical use, given unstable pelvic fractures, mountings applied only anteriorly are not capable of withstanding the strain expected under biological conditions. Consequently, mobilisation with full weight bearing in instable pelvic fractures is not possible in a shorter period of time than with conservative (extension) treatment.