ASSESSMENT OF SCREW DURABILITY USED FOR BLOCKING INTRAMEDULLARY OSTEOSYNTHESIS

Diaphyseal tibial fractures (outside the joint) occupy a leading place among fractures of long bones (8,1–36,6 %). Nowadays, doctors prefer minimally invasive techniques to the ones that cause additional soft-tissue involvement in the area of fracture. Closed blocking intramedullary osteosynthesis (BIOS) is considered to be the most effective technique of osteosynthesis in diaphyseal tibial fractures management. The least traumatic effect as well as the feasibility of early loading of a broken limb are regarded as the benefits of the BIOS. As for the consolidation of the fracture, it is very important that the bone implant system is in constant dynamic tension. Therefore, sometimes it becomes necessary to perform an operation to dynamize the fracture, which consists in removing the locking screw. Improve the results of treatment of patients with extraarticular fractures of the tibia by applying screws made from biodegradable materials. The essence of these materials is that they can dissolve with time. Thus, biodegradable screws after a certain time under loading may be broken. It will give an opportunity to perform stage-by-stage dynamization of the fracture in the given time. Aim. The aim of the study is to examine the factors which influence the durability of blocking screw for BIOS made of biodegradable alloy. Conclusion. Calculations demonstrated that in the model examined the screw stresses are substantially greater than the tensile strength of the material used. What the formula for stresses calculating revealed is that the stresses depend upon a screw diameter only. Thus, it becomes possible to specify the time of screw destruction when using biodegradable screws and knowing the law of solubility. Nevertheless, to verify this law a number of experiments is to be conducted that in its turn proves the complexity of the task. Consequently, the above points to the need for the further research in the field.