The stress-strain state of the "external fixation device – pelvis" system using rods with different thread hands

Abstract

External fixation devices have found wide application in pelvic fractures treating, but it is not always that strength characteristics of these devices make it possible to realize early rehabilitation. The mathematical justification for external pelvic osteosynthesis with use of rods having different thread hands on the basis of analysis of the stress-strain state of the «external fixation device - pelvis» system is presented. In order to increase the stability and reliability of pelvic fixation with external fixation device it is necessary to use a left-handed thread for the left rod, thereby making it possible to avoid loosening of its fixation in the bone, since the "behaviour" of the left rod will be similar to that of the right one. A change in the thread direction does not lead to redistribution of stress-strain state and change in the moment values, but directions of the action of the moments of force for the left rod will correspond to the direction of its screwing both in the left-sided and right-sided one-support position. Keywords: pelvis, stress-strain state, external fixation.