Numerical Simulation of Strain Within the Constructions for Temporary Hemiepiphyseodesis in Patients With Systemic Skeletal Dysplasias

Abstract

Introduction. Guided growth (temporary hemiepiphyseodesis) methods for the correction of axial deformities at the knee joint level in children are used mainly in patients with idiopathic deformities. In patients with systemic skeletal dysplasias the use of these techniques does not take into account the peculiarities of the pathological process. Purpose of study: to evaluate with radiographs the incidence of incomplete plate-bone contact at temporary hemiepiphyseodesis; to assess tensely deforming condition of metal implants using numerical simulation of strain in patients with systemic skeletal dysplasias for the prognosis of their potential failure.Patients and methods. Postoperative radiographs were analyzed for 58 children with systemic skeletal dysplasias after temporary hemiepiphyseodesis (107 extremities, 188 plates; main group) and 50 patients with the deformities of other etiology (control group). Plate-metaphysis contact was considered to be incomplete if it exceeded 2 mm. To determine the plate strains and displacement during the process of bone growth the numerical simulation using COSMOL Multiphusics Software was performed.Results. Incomplete plate-bone contact was observed in 41 (22%) out of 188 constructions. Mean contact deficit made up 4.1±1.3 mm. In control group incomplete plate- bone contact (over 2 mm) was observed only in 3 (4.5%) cases (p<0.05). When a screw is not completely inserted into the bone, its’ the most loaded part is out of the bone and the risk of screw breakage in the contact zone occurs. That was showed by the data of numerical strain simulation.Conclusion. In temporary hemiepiphyseodesis the potentiality of incomplete plate-bone contact resulting from the anatomical peculiarities of epimetaphyseal zone is up to 22%. To improve the efficacy of the guided growth method in children with systemic skeletal dysplasias the elaboration of the constructions should take into account of epimetaphyseal zone configuration.