Taylor Spatial Frame for Deformity Correction in Children

Clinical factors affecting lower limb torsional deformities treatment with the Ilizarov method

INTRODUCTION

One of the many uses of the Ilizarov fixator is for torsional deformities correction. Rotational and translational bone displacement related to torsional deformities correction includes the additional tension stresses, which affect the biology of the regenerated bone. Understanding the clinical factors will assist in designing the optimal treatment strategy, thus possibly improving the outcomes.

PATIENTS AND METHODS

It was case series retrospective study. The study examined 56 patients. The mean follow-up time was 5 years and 6 months. The mean age at the start of treatment was 19 years and 10 months. Patients underwent derotational corticotomies of distal metaphysis of the femur or proximal metaphysis of the tibia using the Ilizarov method. In these patients, following derotational corticotomies with the Ilizarov method, numerous variables were defined and their effect evaluated: the selected treatment strategy, the rate, size, type, and level of derotation on complications, the alignment index, the correction coefficient, the elongation index, and deformation correction factor.

RESULTS

The differences in the values of alignment index and deformation correction factor in this study subgroups were not statistically significant. We found differences in the elongation index and correction coefficient in a number of subgroups.

DISCUSSION

In the case of correcting torsional deformation without significant elongation, acute correction and with a value of >30° does not significantly affect the results. Treatment strategy, type and level of derotation had no major influence on torsional deformities treatment.

LEVEL OF EVIDENCE

Case-control study III.

Biomechanical aspects of lower limb torsional deformation correction with the Ilizarov external fixator

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.