Biomechanical Aspects of Lower Limb Torsional Deformation Correction with the Ilizarov External Fixator

Abstract

The correction of torsional deformities with the Ilizarov apparatus is accompanied by rotational and translational displacement, which affects the biomechanics of the bone fragments. Understanding the biomechanical factors will assist in designing the optimal treatment strategy and mechanical properties of the fixator, thus shortening the duration of treatment and improving the outcomes. In order to determine the impact of different types of derotators on the kinematics of bone fragments in Ilizarov apparatus, physical models were studied. Translational and derotational displacement was measured using non-contact method (Optotrak Certus Motion Capture System). The results of the studies conducted on physical models have shown that regardless of the type of the derotator, the divergence between the applied angle of derotation and the obtained angle of rotation relative to fragments needs to be taken into account. Transverse displacement of fragments occur by 3.5 mm to approximately 9 mm, depending on the angle of derotation. For correction of rotational deformities up to 30°, it is advisable to use the type Z derotators because of its higher accuracy of derotation. Different types of derotators can affect the biomechanical conditions in the regenerating bone tissue through different kinematics characteristics.

Lower extremity growth and deformity

“…Correction of torsional deformity with external fixation and constrained hinges and motors is difficult when using the Ilizarov external fixators. Morasiewicz et al has shown that the Z-type derotator is more accurate than the H-type or translational-derotational connectors [25]. Treating rotational deformities with external fixation has been made simpler with the Taylor spatial frame and the advent of virtual hinges [26].…”

The Use of 3D Printing Technology in the Ilizarov Method Treatment: Pilot Study

“…3D printing technique allows for a very accurate reconstruction of the bone, while keeping its actual size and spatial geometry [8][9][10][11], which facilitates the planning of treatment.…”

“…Complex multi-dimensional deformations, aplasia and hypoplasia of bones, especially in children, are diagnosed more often, but rarely treated, particularly in children at a younger age. This is due to the structural complexity of the Ilizarov apparatus following the addition of hinges which enable corrections of a multiplanar deformity, the small size of the Ilizarov apparatus for the youngest children, the necessity of precisely mounting and installing the stabilizer onto the patient, and the increased possibility of complications following treatment [5][6][7][8]11].…”