Mobile planovalgus deformity of foot (MPVDF) ranks second among all foot deformities in children with cerebral palsy. An important element in the MPVDF pathogenesis in children with cerebral palsy is the instability of the subtalar joint, which develops gradually and is one of the pathogenetic components in the further the deformity progression. It is shown that one of the promising ways for obtaining new knowledge to determine the force changes in the foot’s components in the norm and in cases of its deformity, is the use of the finite elements method to study the stress-strained state.
The purpose of the work was to improve the results of treating mobile planovalgus deformity of feet in children with cerebral palsy by substantiating the options of its surgical correction based on biomechanical modeling, clinical and radiological studies of structural and functional changes in affected feet.
Object of research: Mobile planovalgus deformity of foot in children with cerebral palsy.
Research methods: clinical, radiological, biomechanical modeling, computer mathematical modeling, statistical.
A retrospective analysis of these case histories was performed in 34 patients with cerebral palsy (56 feet) who were divided into two groups. In two age groups of children with cerebral palsy, the following was determined:
- - The most typical complaints observed in children with cerebral palsy with MPVDF are: walking disorders and foot deformities, pain syndrome – in 51.8 %, fatigue - in 83.9 %; impaired foot support - 89.6 %
- - in 96.4 % of cases in children with cerebral palsy MPVDF is accompanied by rigid equinus deformity of the foot;
- - in patients of both groups there was an increase Meary angle and a decrease in the heel angle, indicating a decrease in the medial longitudinal arch of the foot, and an increase in the angle of the calcaneonavicular planar arch indicates the presence of pathological abduction of the anterior foot;
- - the most common secondary deformity was rigid supination deformity of the anterior foot, which occurred in 62.9 % of children in age group 2;
- - a significant percentage (66.7 %) of MPVDF recurrences was revealed in children aged 7-10 years, who underwent surgical techniques;
- - a subgroup of children was identified in whom arthroereisis of the subtalar joint permitted to effectively maintain the correction of the foot, but 80 % of them reported chronic pain, of the its conical shape of the standard implant that does not coincide with the anatomical structure of sinus tarsi.
A clinical and experimental study was performed to determine the projection of the subtalar joint axis on the plantar surface of the foot in three groups of children: healthy, healthy with MPVDF, diseased with cerebral palsy and MPVDF.
Biomechanical studies using the designed mathematical models of foot in norm and in MPVDF are carried out by means of a finite element method and features of loadings distribution in foot were defined depending on various variants of surgical intervention used for correction of MPDVF. The advantages of stress distribution in the calcaneal and subtalar bones in the case of subtalar joint arthroereisis using the proposed hollow two-stage conical implant compared to the standard one have been proved.
A three-stage working clinical and radiological classification of the planovalgus deformation severity in children with cerebral palsy is proposed.
Algorithms for choosing the method of MPVDF surgical treatment in children with cerebral palsy, based on the proposed working classification of the foot deformation severity, the results of biomechanical modeling, clinical and radiological, functional assessment of the foot, and provide a choice between soft tissue intervention and mild invasive subtalar arthroereisis, or corrective osteotomy of the bones in the posterior and the middle foot or arthrodesis of the joints in the posterior foot in combination with soft tissue interventions (according to the indications).
The results of clinical verification of the proposed algorithms according to the severity of planovalgus deformity of feet in children with cerebral palsy are presented. In particular, a minimally invasive technique of the subtalar joint arthroereisis was tested for the treatment of MPVDF in 5 patients (10 feet) with cerebral palsy, using the developed hollow two-stage conical implant.
The efficacy and safety of the technique for the subtalar joint arthroereisis has been proven, which permitted to obtain normalization of X-ray parameters in 89.4 % of children and to improve functional mobility in the nearest future after the surgery.
The results of the study were implemented in clinical practice by the State Institution “Sytenko Institute of Spine and Joint Pathology, National Academy of Medical Sciences of Ukraine“, Kharkiv regional clinical trauma hospital and other hospitals of Ukraine.
Scope of use – medicine (pediatric orthopedics).
