[Current trends and problems in the measurement of limb loading parameters during transosseous osteosynthesis using external fixation devices].
The problem in question is whether it is reasonable to equip a conventional limb external fixation apparatus with means for the diagnosis of loading parameters: the forces and displacement of the opposite supporting elements of the apparatus. It is assumed that during distraction osteogenesis it is expedient to apply load to the limb by the load rate only at the initial stage of callus regeneration (the plastic or slightly elastic mechanical state) while the most effective way to do so is to act force at later stages. A number of functions derived from the modified parameters which might aid a physician to choose the optimum limb loading parameters at different stages of treatment were considered by using as example a hypothetical ring-type apparatus equipped with means for continuous measurement of current forces applied to the apparatus and current displacements of opposite ring blocks. Specifications for the measuring system of loading parameters were defined by using an Ilizarov apparatus as an example and why possible rough measurement errors may occur is revealed. The paper shows it necessary to develop methods for calculation of parasitic deformations, i.e. those of the loaded elements of the apparatus for the evaluation of the reciprocal displacement of bone fragments.