Introduction Over the last decades numerous new materials and techniques for bone tissue engineering have been developed. The use of bioresorbable polymeric scaffolds is one of the most promising techniques for surgical management of bone defects. However, the lack of bioactive properties of biodegradable polymers restricts the area of their application for bone tissue engineering.

The aim of study was to apply solvent/non-solvent treatment to coat the surface of 3D-printed bioresorbable poly(ε-caprolactone) scaffolds with bioactive hydroxyapatite particles and report on the physicochemical properties of the resulting materials.

Material and Methods In the present study, biomimetic poly(ε-caprolactone) scaffolds were 3D-printed via fused deposition modeling technology and their surface was treated with the solvent/non-solvent method for coating with bioactive particles of hydroxyapatite.

Results It has been found that treatment in the mixture of toluene and ethanol is suitable for the coating of poly(ε-caprolactone) scaffolds with hydroxyapatite. The scaffolds maintain porous structure after treatment while hydroxyapatite particles form homogeneous coating. The amount of hydroxyapatite on the treated scaffolds was 5.7 ± 0.8 wt. %.

Discussion The proposed method ensures a homogeneous coating of outer and inner surfaces of the poly(ε-caprolactone) scaffolds with hydroxyapatite without a significant impact on the structure of a scaffold. Fourier-transform infrared spectroscopy confirmed that the solvent/non-solvent treatment has no effect on the chemical structure of PCL scaffolds.

Conclusion Coating of biomimetic 3D-printed PCL scaffolds with bioactive hydroxyapatite by the solvent/non-solvent treatment has been successfully carried out. Upon coating, scaffolds retained their shape and interconnected porous structure and adsorbed hydroxyapatite particles that were uniformly distributed on the surface of the scaffold.

Introduction Assessment of biological characteristics of polylactide/hydroxyapatite (PLLA/HA) biodegradable materials is requiered to specify indications for the use of PLLA/HA composite implants in clinical practice.

The present study was aimed to measure the kinetics of calcium and phosphate release from PLLA and its dependence on polymer structure crystallinity.

Material and methods Four types of biodegradable materials were studied in vitro. Samples of type 1 and type 3 made of crystalline PLLA after annealing contained 25 % and 50 % of HA mass fraction, respectively. Samples of type 2 and type 4 made of amorphous PLLA (without annealing) contained 25 % and 50 % of HA mass fraction, respectively. In every group, 6 samples were tested. The samples were incubated in an aqueous medium at 37 °C for 52 weeks. The rate of PLLA degradation was assessed by the accumulation of lactate monomer in the hydrolysate. The concentrations of calcium ions and phosphate ions were determined for assessment the HA hydrolysis rate. The degree of crystallinity of the polymer matrix was evaluated by scanning calorimetry.

Results The hydrolysis of PLLA and HA in the samples was not simultaneous. The PLLA was hydrolyzed first followed by HA hydrolysis. By the moment of complete hydrolysis of PLLA, there was only 15 % of hydrolyzed HA. The release of calcium ions occurred from the sixth week of incubation for all tested samples, that of phosphate ions from the third week. The total amount of the released calcium ions and phosphate ions decreased in the line: material 3 > material 4 > material 1 > material 2. Calcium ions in the hydrolysates were detected up to 42 weeks of incubation, phosphate ions up to the 52nd week.

Conclusion Higher crystallinity of PLLA achieved by annealing results in increased rate of hydrolysis of HA from PLLA matrix. Biological activity of PLLA/HA implants can be determined by degree of polymer crystallinity and saturation with HA.

Introduction The problem of implant-associated infections is far from being solved in arthroplasty, osteosynthesis of fractures, and spinal pathology. The development of biodegradable implants with bioactive properties is a promising direction.

The purpose of this study was to evaluate the in vitro bactericidal activity of implants made from a degradable material polycaprolactone (PCL) impregnated with hydroxyapatite and an antibiotic.

Material and methods To study antibiotic availability, antibiotic-impregnated PCL cylindrical samples (n = 6) were incubated in distilled water at 37 °C. To evaluate the antibacterial properties, samples in the form of porous disks were used: control samples from PCL; 1) PCL samples coated with antibiotic and hydroxyapatite; 2) PCL samples coated only with antibiotic; 3) PCL samples coated only with hydroxyapatite; (n = 6 for each type of tested samples). The disk diffusion method was used to determine the sensitivity of microorganisms to antibiotics. The microbial strains used were S. aureus ATCC 25923, P. aeruginosa ATCC 27853 and E. coli ATCC 25922. Test microorganisms were cultivated on beef peptone agar (MPA) at 37 °C for 24 hours. Quantitative data were subjected to statistical processing.

Results It was determined that 82.6 % of the antibiotic was released during the first day of incubation and 8.2 % on the second day. Control samples did not show a bactericidal effect. Samples 3 showed an antibacterial effect against E. coli culture. Samples 1 and 2 equally demonstrated significant inhibition of the growth of S. aureus, P. aeruginosa, and E. coli.

Discussion Most of the antibiotic is released into the hydrolyzate during the first two days of incubation. Porous implants made of PCL and impregnated with an antibiotic have pronounced antimicrobial activity against the most common gram-negative and gram-positive bacteria that cause purulent complications in surgical practice. Nanostructured hydroxyapatite on the surface of the implant does not reduce bactericidal activity.

Conclusions Porous polycaprolactone implants filled with hydroxyapatite and antibiotics are targeted to stimulate bone regeneration and simultaneously ensure antimicrobial activity. Nanostructured hydroxyapatite on the implant surface does not decrease bactericidal activity.

Background Management of bone defects with autologous bone grafting has always been the "gold standard" but it is not always possible to use it for a number of reasons. Preprocessed materials of biological and non-biological origin were developed as an alternative. A new branch of these materials is tissue-engineered constructs that fully imitate autologous bone in required volume.

Aim is to study in vivo the possibility of using deproteinized human cancellous bone tissue as a matrix for creating tissue-engineered constructs.

Methods The study was carried out on 24 NZW line rabbits, since this line has a fully characterized stromal-vascular fraction formula (SVF). The study design included 3 groups. First group (control) had surgical modeling of bone defects in the diaphysis of the contralateral femur without reconstruction; Group 2 had bone defect reconstruction using fragments of a deproteinized cancellous bone graft; group 3 underwent bone defect reconstruction using fragments of deproteinized cancellous bone matrix along with the autologous adipose tissue SVF (obtained according to ACP SVF technology). Animals were sacrificed with ether anesthesia at 2, 4 and 6 weeks after the operation and subsequent histological study followed.

Result During all periods of the study, the newly formed bone tissue volume density in the 3rd group (reconstruction with deproteinized human cancellous bone + stromal-vascular fraction) was 1.78 times higher (p < 0.001) than in the first group (bone defect without reconstruction), 1.21 times higher (p < 0.001) than in the 2nd group (reconstruction with deproteinized cancellous bone alone). The dynamics of changes in the mature bone tissue volume density was similar to those of the newly formed bone tissue.

Discussion The comparative analysis of reparative processes using a tissue engeneered construst based on deproteinized cancellous human bone with adipose tissue stromal vascular fraction revealed that the use of these bone substitute materials contributes not only to the early activation of reparative regeneration of the main structural elements of bone tissue at the site of bone defect, but also their timely differentiation.

Conclusion The use of deproteinized cancellous bone matrix combined with stromal-vascular fraction to create a tissue-engineered construct could unleash several regeneration mechanisms and accelerate the process of bone defect site repair, compared with 1st and 2nd group of study.

Introduction The number of surgical interventions using additive technologies in medicine has been growing both in Russia and with every year. Due to the development of printing customized implants, the use of standard (imported) designs has decreased by an average of 7 % in the provision of high-tech medical care. However, the issue of the pore size of customized implants for management of post-traumatic defects in the acetabulum remains open.

Objective To evaluate the results of the treatment of patients with post-traumatic acetabulum defects and deformities with the implementation in clinical practice of customized implants with structure and size porous surface that are optimal from the point of view of biological fixation.

Material and methods Porous implants with different types of porous structure were produced by direct laser sintering using Ti-6Al-4V titanium alloy powders. Experimental work was carried out in vitro to determine the ability of living fibroblasts to penetrate the pores of different sizes. Next, the clinical part of this study was conducted in order to determine the signs of biological fixation of customized acetabular implants in a group of patients (n = 30).

Results The results of this experiment performed to analyze the penetration of living fibroblasts into the porous structure of implants with different pore size demonstrated that metal structures with a pore size of 400-499 μm can be singled out from all others.

Discussion Analysis of the literature data shows that there is no consensus on the structure and size of the pores of a customized implant. In our work, we investigated the ability of human living fibroblasts to penetrate into the surface structure of a customized implant, as a result of which we determined their optimal pore size of 400-499 microns. It should be noted that this study was conducted for a definite anatomical location: the acetabulum. However, it cannot be excluded that the data obtained are relevant for other anatomical locations.

Conclusion Management of bone defects in the acetabulum area with customized implants featuring the surface pore size of 400-499 microns is a justified and relevant method. A prerequisite for the use of such implants is strict compliance with the indications for their use, careful preoperative planning and correct positioning.

Introducrion Repair of the affected articular surface still remains an unsolved problem.

The purpose of this study was to assess the efficacy of a biodegradable polycaprolactone implant coated with hydroxyapatite on the healing of an osteochondral defect of the femoral condyle in rats.

Materials and methods An osteochondral defect of the medial femoral condyle was modeled in 76 Wistar rats divided into 2 groups. In the experimental group, the defect was replaced with a biodegradable polycaprolactone membrane coated with hydroxyapatite. In the control group, the defect remained untreated. The results were assessed within a year.

Results In the experimental group, the animals had a significantly better range of motion at all stages of the experiment than the control animals. The implant ensured the integrity and congruence of the articular surface. On day 180, a newly formed area of the articular surface of the organotypic structure was observed in the defect. Biomechanical properties of the repaied zone restored after 60 days while in the control one they remained lower by 27-29 %.

Discussion Filling the defect with an elastic implant made of polyprolactone with hydroxyapatite provided early functional load on the joint. The structure of the implant, simulating the extracellular matrix, promoted the growth, proliferation and directed differentiation of cells in the area of the osteochondral defect. The moderate rate of biodegradability of the material provided gradual replacement of the implant with organ-specific tissues.

Conclusion A biodegradable polycaprolactone implant impregnated with hydroxyapatite particles might be effective for experimental osteochondral defect repair.

Background Development of resorbable implants for paediatric orthopaedics is promising as there is no need for implant removal.

The aim of this paper is to present our experience in resorbable implants in paediatric traumatology, and to make an overview of the recent literature.

Material and methods In our department of paediatric traumatology and orthopaedics, we have operated 7 children with fractures of long bones with resorbable screws (ActivaScrew™). The inclusion criteria were intra-articular and juxta-articular fractures in children with an indication for screw fixation. To prepare the review, we searched for information sources at the scientific platforms such as PubMed, Scopus, ResearchGate, RSCI, as well as other published products (Elsevier, Springer).

Results The cohort is represented by 7 patients, 4 girls and 3 boys, aged from 5 to 14 years old. The 7 fractures were 3 at the elbow and 4 at the ankle joint. In the immediate postoperative period, no patient presented with abnormal swelling, redness, or tissue reaction. Pain disappeared at day 7 in all cases. Weight-bearing and return to sport activities were allowed in normal delay. Radiological bone union was obtained between 3 and 6 weeks. Range of motion in adjacent joints was comparable to the opposite non-fractured side at 3 months. There were no cases of complications, no infection, and no need for a reoperation.

Discussion The use of resorbable implants, either co-polymers or magnesium, solves the problem: removal of implants is not anymore necessary. Resorbable implants are becoming safer as they have good solidity allowing bone union of fractures and osteotomies before their eliminating.

Conclusion Main indications of resorbable implants in pediatrics remain fractures and osteotomies fixed with screws. The development of plates and intramedullary nails will enlarge the indications. Level of evidence: IV.

Introduction Widespread use of intramedullary and extramedullary implants, as well as external fixation devices, has demonstrated that current surgical methods are not always successful.

The study aimed to assess the efficiency of a combination of transosseous osteosynthesis with intramedullary reinforcement using elastic titanium hydroxyapatite-coated rods (HA-rods) in long bone fracture treatment.

Material and methods Medical records of 40 patients aged from 18 to 55 years with closed diaphyseal tibia fractures of A1-A3 type (AO/ASIF) treated with the Ilizarov transosseous osteosynthesis method combined with intramedullary elastic HA-coated wires were analysed. Result Ilizarov fixator removal was performed on average 45.3 ± 14.7 days after surgery. Radiological signs of bone union (immature callus, patterns of periosteal and endosteal stratifications overlapping the fracture line) were visible by week 3 to 4.

Discussion Соmbination of the external fixator and intramedullary elastic HA-coated wires overcomes shortcomings of both external and internal means of fixation. External osteosynthesis provides advantages of the Ilizarov method: preservation of blood supply, absence of soft tissue injury, joint function and early weightbearing. Elastic intramedullary wires do not injure a. nutricia and mechanically stimulate endosteal and periosteal bone formation.

Conclusion The advantages of combined osteosynthesis provide reduction of Ilizarov apparatus fixation time, reduction in the number of wires and half-pins in the frame assembly, stimulation of bone callus formation and prevention of secondary bone fragment displacement.

Introduction Forearm fractures are common injuries in childhood. Completely displaced and unstable fractures require surgical intervention. Elastic Stable Intramedullary Nailing (ESIN) is widely used in treating these fractures. Although stainless steel and titanium implants are the most widely used, resorbable nails are becoming an option.

Aim To present our initial experience in treating forearm fractures in children with Resorbable Stable Intramedullary Nailing (ReSIN).

Methods The authors present several cases treated with ReSIN, their summarry and describe the techniqual steps. Results The series included 4 patients operated on with ReSIN. Bone union with anatomic and functional recovery was stated in all cases within the period of 5-7 months after surgery.

Discussion More and more paediatric fractures can be treated with absorbable implants and result in good outcomes. It can be said that the new methods enabled similar stable fixation as with metal implants, which is considered the gold standard. A distinct advantage over metal implants is that there is no need to remove the implant, thus avoiding a second operation and reducing the risk of surgical complications. Another positive thing is that absorbable implants can be sunk the level of the cortical layer of the bone, they can easily be dropped under the skin. The only drawback of the method is the price of the implants.

Conclusion The management of paediatric diaphyseal forearm fractures with bioabsorbable intramedullary nails is a promising emerging alternative to the gold standard ESIN technique.

Introduction Long duration of distraction osteosynthesis remains an unsolved problem. One of the promising ways to stimulate reparative regeneration of bone tissue is the technology of combined osteosynthesis with intramedullary elastic reinforcement with titanium wires coated with hydroxyapatite. A significant drawback of this combined distraction osteosynthesis is the planned removal of intramedullary wires several months after disassembling the Ilizarov apparatus.

The purpose of this work is to demonstrate the possibility of stimulating reparative regeneration and reducing the duration of distraction osteosynthesis using an intramedullary degradable implant with bioactive filling.

Methods We present the first in clinical practice case of surgical leg lengthening in a female 10-year-old patient using the Ilizarov apparatus an intramedullary degradable implant made of polycaprolactone (PCL) saturated with hydroxyapatite to stimulate reparative regeneration in the tibia. Monthly radiographic monitoring of the process of reparative regeneration of bone tissue was supplemented by computed tomography after disassembling the Ilizarov apparatus.

Results The process of lengthening the tibia was accompanied by pronounced formation of a bone “sleeve” around the implant, which was directly connected to the endosteum of the tibia. The density of bone substance in the medullary canal reached 496.6 HU. The cortical layer of the tibia in the elongation zone increased to 4 mm, and its density was equal to 1288.8 HU.

Discussion Leg lengthening of 4 cm was achieved along with simultaneous correction of valgus recurvatum bone deformity at IO = 15 days/cm, that is two times shorter than the generally accepted excellent IO in distraction osteosynthesis according to Ilizarov.

Conclusions Biodegradable polycaprolactone implants saturated with hydroxyapatite might be not inferior to titanium wires coated with hydroxyapatite in regard to the degree of osteoinduction and do not require repeated surgical intervention to remove them.

Introduction An aneurysmal bone cyst (ABC) is a rare, non-neoplastic, destructive, hemorrhagic, and expansile lesion accounting for 1 % of all bone tumors. ABC of the foot is very rare. Patients with foot ABC usually complain of pain and swelling of the affected area. Radiographs and MRI may be helpful in the diagnosis of ABC. No single surgical procedure has gained wide acceptance in the treatment of foot ABC.

Purpose To show new effective surgical approach in the treatment of patient with ABC of the medial cuneiform bone.

Material and methods We present the case of a 47-year-old woman with a 10-months history of pain and swelling in her right foot. Postoperative histopathological evaluation of resected tissues confirmed the diagnosis of ABC. An en bloc resection (total extraction of the remnant of the medial cuneiform bone) was performed and the defect was replaced with a fibular bone graft from the right leg. Allograft (Bio-Ost®) was placed along the autograft. Tibialis anterior tendon was attached to the fibular bone graft. We performed fixation of the foot and ankle using the Ilizarov original apparatus for prevention of bone graft instability and opportunity for early weight-bearing on the operated foot.

Results The postoperative period was uncomplicated with complete healing of the bone defect without recurrence after 12 months of observation. AOFAS score increased significantly from 34 points preoperatively to 92 at 1-year follow-up.

Discussion The optimal treatment of this lesion is still under discussion. Different treatment modalities have been described in the literature: wide resection, curettage with or without adjuvants, arterial embolization, intralesional sclerotherapy. Biological reconstruction using bone graft seems to be the best option, but fractures and nonunion are common complications of bone grafting.

Conclusion The combination of Ilizarov external fixation and bone grafting provided favorable conditions for the healing of foot bone defect due to ABC without complications, allowed mobility and early weight-bearing of the patient. Recurrence was not detected radiologically. Harvesting of the fibular bone graft did not affect the position of the foot and its movements. Our surgical approach should be considered as a treatment option in similar cases.

Introduction One of the key limitations of distraction osteogenesis (DO) is the absence or delayed formation of a callus in the distraction gap, which can ultimately prolong the duration of treatment.

Purpose Multiple modalities of distraction regenerate (DR) stimulation are reviewed, with a focus on modulation of the mechanical environment required for DR formation and maturation.

Methods Preparing the review, the scientific platforms such as PubMed, Scopus, ResearchGate, RSCI were used for information searching. Search words or word combinations were mechanical bone union stimulation; axial dynamization, distraction regenerate.

Results Recent advances in mechanobiology prove the effectiveness of axial loading and mechanical stimulation during fracture healing. Further investigation is still required to develop the proper protocols and applications for invasive and non-invasive stimulation of the DR. Understanding the role of dynamization as a mechanical stimulation method is impossible without a consensus on the use of the terms and protocols involved.

Discussion We propose to define Axial Dynamization as the ability to provide axial load at the bone regeneration site with minimal translation and bending strain. Axial Dynamization works and is most likely achieved through multiple mechanisms: direct stimulation of the tissues by axial cyclic strain and elimination of translation forces at the DR site by reducing the effects of the cantilever bending of the pins.

Conclusion Axial Dynamization, along with other non-invasive methods of mechanical DR stimulation, should become a default component of limb-lengthening protocols.

Introduction Technological advances in bone tissue engineering have improved orthopaedic implants and surgical techniques for bone reconstruction. This approach allows overcoming inconvenience of the paucity of autologous materials available and donor site morbidity.

Aim To demonstrate advances of the past 30 years in the development of bioimplants providing alternatives to bone grafting in reconstructive orthopaedics.

Methods Preparing the review, the scientific platforms such as PubMed, Scopus, ResearchGate, RSCI were used for information searching. Search words or word combinations were bioactive osteoinductive implants, bone grafting, bone reconstruction, hydroxyapatite, bone scaffolds.

Results The main trends in tissue engineering in the field of orthopaedics are represented by construction of three-dimensional structure implants guiding cell migration, proliferation and differentiation as well as mechanical support. Association with bone morphogenetic proteins, growth factors enables proliferation and differentiation of cell types of the targeted bone tissue. A promising advancement should be biodegradability with a controllable degradation rate to compliment cell/tissue in-growth and maturation in limb reconstruction.

Discussion This review presents and discusses the experimental and clinical application of biotolerant, bioinert and bioactive materials for reconstructive bone surgery. Future generations of biomaterials are designed to be osteoconductive and osteoinductive.

Conclusion Properties of polycaprolactone (PCL) filled with hydroxyapatite (from 10 to 50 wt %) make this hybrid material with controllable absorption a promising strategy for reconstructive surgery in comparison to other materials.