Flexible intramedullary nails for limb lengthening: a comprehensive comparative study of three nails types

Abstract

A comparative study of flexible intramedullary nails (FIN) used for lengthening of long tubular bones in children is presented. It has been found that the presence of calcium phosphate coating obtained by micro-arc oxidation or a composite coating based on a copolymer of vinylidene fluoride with tetrafluoroethylene and hydroxyapatite on the surface of FIN significantly enhances the formation of bone regenerate in the area of osteotomy during limb lengthening by combined osteosynthesis. The investigation of physico-chemical properties of FIN with calcium phosphate coating obtained by micro-arc oxidation demonstrated that improved bone tissue formation is due to favourable conditions for adhesion, proliferation, and differentiation of MMSCs into osteoblasts on the coating surface. Composite coatings stimulated the formation of bone tissue only in vivo, mainly due to the piezoelectric properties of the copolymer of vinylidene fluoride with tetrafluoroethylene. Keywords: flexible intramedullary nails, calcium phosphate coating, vinylidene fluoride -tetrafluoroethylene, piezoelectric, combined limb lengthening 1. Introduction Deterioration of the environmental situation, primarily in industrialized countries, and rising frequency of genetic diseases provoke an increase in the number of patients and the severity of orthopaedic pathologies associated with congenital shortening and deformities of the limbs. The limb shortening, progressing as a person develops, leads to pathological changes in the entire biomechanical system. For example, overloading a healthy limb and skewing of the pelvis cause the development of pathologies associated with deformations and dislocation of the healthy hip, leading to a decrease in the quality of life. Thus, the restoration of the limb length allows solving not only the problems of orthopaedic and biomechanical recovery, but also the problem of social rehabilitation and patient's integration into society. For congenital limb length discrepancy the correction of pathology in the affected segment and functionally related elements of the biomechanical system could be done only through surgical interventions. A major contribution for solving this problem was made by outstanding orthopaedic surgeon G.A. Ilizarov, who developed the methods of surgical treatment based on distraction osteogenesis [1,2]. The recent development of G.A Ilizarov method resulted in development of combined osteosynthesis. In this approach, the external fixation devices and thin (up to 2.5 mm) flexible intramedullary nails (FIN) implanted into medullary canal of the tubular bone are used [3,4]. The circular external fixator allows to achieve the high stability of the bone fragments positioning. FIN located in the anatomical zone with multipotent cells depot and a good blood supply, allows to control the histogenesis aimed at bone tissue production. The unique anatomical location of FIN makes it one of the key elements of the combined osteosynthesis. FIN properties largely determine the clinical success of the limb leng...

Biocompatibility and Osseointegration of Calcium Phosphate-Coated and Non-Coated Titanium Implants with Various Porosities

“…To prevent scratch-fit effects when fixing the implants, they were fabricated without an aggressive rough coating on the surface. A calcium phosphate coating of 20±4 μm thickness was applied to some of the samples by the microarc oxidation method [ 8 ] using an experimental facility at the National Research Tomsk Polytechnic University (Russia). Next, wet-steam sterilization was carried out at a temperature of 134°C for 5 min in accordance with GOST R ISO 17665-1, which was followed by placing the samples in a triple sterile package.…”

“…Many authors agree when it comes to biodegradable calcium phosphate coatings of titanium implants: coatings significantly improve their osteoinductive properties and promote osteogenesis [6,8,9,14]. Kalinichenko et al [14] studied how a biodegradable calcium phosphate and hydroxyapatite coating applied to titanium implants by plasma electrolytic oxidation affected osteogenesis in the setting of simulated closed fracture of the rat femur.…”

“…Calcium phosphate coatings formed by microarc oxidation on the surface of titanium implants are known to significantly improve the osteoinductive properties of products used for extraosseous and transosseous osteosynthesis [ 8 , 9 ]. However, application of such 3D printed implants is limited in general clinical practice.…”

Antibacterial Ferroelectric Hybrid Membranes Fabricated via Electrospinning for Wound Healing

“…Vinylidene fluoride-tetrafluoroethylene (VDF-TeFe) copolymer is one of the most electrically active polymers demonstrating high residual polarization and piezoelectric constants [12,13]. At the same time, VDF-TeFe copolymer demonstrates the lowest polarization switch period [14], high Curie temperature, high strength, thermal stability, tissue compatibility, and anti-adhesive properties [15,16]. The complex of these properties makes VDF-TeFe copolymer one of the most potentially useful materials for the development of electrospun polymer membranes with ferro-and piezoelectric properties for wound healing.…”

Composite Ferroelectric Membranes Based on Vinylidene Fluoride-Tetrafluoroethylene Copolymer and Polyvinylpyrrolidone for Wound Healing

“…Compared to PVDF, the VDF-TeFE copolymer is characterized by a lower hardness and elastic modulus and a higher strength, relative elongation, crystallinity, pyroelectric coefficient, and electrostrictive constant, as well as the ability to form a ferroelectric β crystalline phase directly from the melt [21][22][23][24]. These properties along with high biocompatibility [25,26] make VDF-TeFE a polymer of choice for producing atraumatic membranes with high handling properties and electrical activity. The inclusion of nontoxic water-soluble PVP in the structure of VDF-TeFE membranes potentially allows encapsulation and efficient drug delivery to regeneration zones [27].…”