Biomechanical analysis of the cancellous screws implantation schemes in surgical treatment of flexible flatfoot in children

Abstract

Carry out comparative biomechanical analysis of influence of the implantation scheme and characteristic sizes of cancellous screws on parameters of its strained condition, and elaborate guidelines for optimization of implantation parameters and decision for a material metalware choice. Performed mathematical modelling and comparative numerical analysis of the parameters of strained condition, slant and cantilevered schemes of implantation of cancellous screws, applied to a wide range of support loads variations acting on a screw. Made analysis of influence of size parameters (length of the overhanging part, angle with normal at supporting surface, core diameter) on the magnitude of the calculated stress that appear in compressed and extended zones of slant implanted screw. Carried out investigations reveal that short screws, installed on the hard circuit, from the standpoint of operational reliability according to the criteria of strength under static loading (occasional overload) and multicyclic loading have the highest capacity for work. Least favourable in application are slant and cantilevered implanted screws. With increasing length of cantilevered part and angle between axis of a screw and line of loading force calculated values of stress also increases. Screws of heat-treated stainless steel are preferred from the standpoint of saving bearing capacity with unit congestion due to increased plasticity in 4–5 times (residual strain at failure) compared with titanium alloys.