Age- and sex-related changes in vertebral trabecular bone architecture in Neolithic and Mediaeval populations from Poland.

This paper investigates trabecular bone ontogenetic changes in two different Polish populations, one prehistoric and the other historical. The studied populations are from the Brzesc Kujawski region in Kujawy (north-central Poland), one from the Neolithic Period (4500-4000 BC) and one from the Middle Ages (twelfth-sixteenth centuries AD), in total 62 vertebral specimens (32 males, 30 females). Eight morphometric parameters acquired from microCT scan images were analysed. Two-way ANOVA after Box-Cox transformation and multifactorial regression model were calculated. A significant decrease in percentage bone volume fraction (BV/TV; [%]) with age at death was observed in the studied sample; Tb.N (trabecular number) was also significantly decreased with age; trabecular separation (Tb.Sp) increased with advancing age; connectivity density (Conn.D) was negatively correlated with biological age and higher in the Neolithic population. These data are found to be compatible with data from the current biomedical literature, while no loss of horizontal trabeculae was recorded as would be expected based on modern osteoporosis.

Biomechanics of esophageal elongation with traction sutures on experimental animal model.

Esophageal elongation is one of the methods of long gap esophageal atresia treatment. The aim of the study was to determine the best type of traction suture for esophageal lengthening on an animal model. White Pekin Duck's esophagi were used as a model (fresh-frozen and thawed). The esophagus was cut in half, then both ends were sutured together and extended on a tensiometer. Tested sutures involved simple suture, suture aided by a single or double clip, and suture aided by pledget (10 samples each). Constant and 2 methods of intermittent traction were also compared. The histological study showed similarities between duck's and newborn's esophagus. The highest maximal force was achieved with pledget suture (F = 8.59 N ± 1.45 N), then with double clip (F = 5.74 N ± 1.29 N) and the lowest with single suture (F = 3.80 N ± 0.54 N) (p < 0.001). Pledget suture also allowed for the greatest elongation (p < 0.01). Intermittent traction results in better elongation at the same breaking strength as constant traction (p < 0.05) if traction is maintained during breaks. Reinforced sutures (pledget or double clip) should be taken into consideration in internal traction. When performing traction sutures, it is worth step by step carefully tightening the sliding knot in short periods before its final binding.

Experimental assessment of changes in bone fragment position using infraread diodes on saw bone models with a hexapod fixator.

BACKGROUND: The purpose of this study was an experimental assessment of changes in bone fragment position in patients with non-union of the tibia treated with a hexapod fixator. HYPOTHESIS: We hypothesized that the use of hexapod fixators leads to differences between the planned and actual position of bone fragments. METHODS: The study was conducted in physical models of the hexapod fixator-bone fragment system. Bone fragment displacement was measured using the Optotrak Certus Motion Capture System. We assessed differences between the planned and actual position of bone fragments. RESULTS: Assessment of bone fragment compression demonstrated a difference between the target and actual correction ranging from 1.5% to 13.2% (depending on the force applied to bone fragments) for configuration 1, from17% to 21.3% for configuration 2, and from 13.2% to 17.9% for configuration 3. The achieved varus deformity correction constituted 93.7-98.4% of the target correction for configuration 2 and 98.3-98.9% of the target correction for configuration 3. Torsional deformity correction showed considerable discrepancies between the target and achieved correction, ranging from 65.6% to 83%. DISCUSSION: The value of the applied compression force had no marked effect on the differences between the target and achieved correction or on the magnitude of unintended rotational and transverse displacement of bone fragments. The use of hexapod fixators helped achieve complete correction of the simulated varus deformity; however, complete correction of torsional deformities was not achieved. Deformity correction in physical models with the use of a hexapod fixator yielded instances of unintended rotational and transverse bone-fragment displacement. The use of hexapod fixators in physical models leads to differences between the planned and actual position of bone fragments. LEVEL OF EVIDENCE: IV, case series.

Influence of the intramedullary nail locking method on the stiffness of the bone-implant system.

PURPOSE: Bone fractures are one of the most commonly seen problems in veterinary traumatology. The authors of this study strive to find a new intramedullary nail, which is intended for treating femoral bone fractures for canine patients. The purpose of this study was to analyze biomechanical parameters of the intramedullary nails, which use a new bolt system concept. METHODS: Dissected femoral bones of a large breed dog were cut in order to simulate interfragmentary gap, and then the bones were stabilized using intramedullary nail with locking bolts. Bone-nail systems were subjected to cyclic loading using force which corresponds to the load on the femoral bone in the first few days after surgery. Micro-CT scans were taken of the bone samples around implant in order to determine deformation and structural parameters of bone tissue. RESULTS: The calculation of the bone-nail system stiffness was done through analysis of the force- displacement curves recorded during experimental studies. Using monocortical locking bolts resulted in smaller stiffness of the bone-nail system than using bicortical locking bolts. CONCLUSIONS: The results obtained in this study can indicate that the intramedullary nail could work well when used for treatment of bone fractures in dogs. The authors focused on using monocortical bolts which provides good stability and adequate biomechanical environment. Described fixation method is easily adjustable to a particular patient individual pa- rameters.

Novel Nanohydroxyapatite (nHAp)-Based Scaffold Doped with Iron Oxide Nanoparticles (IO), Functionalized with Small Non-Coding RNA (miR-21/124) Modulates Expression of Runt-Related Transcriptional Factor 2 and Osteopontin, Promoting Regeneration of Osteoporotic Bone in Bilateral Cranial Defects in a Senescence-Accelerated Mouse Model (SAM/P6). PART 2.

PURPOSE: Healing of osteoporotic defects is challenging and requires innovative approaches to elicit molecular mechanisms promoting osteoblasts-osteoclasts coupling and bone homeostasis. METHODS: Cytocompatibility and biocompatibility of previously characterised nanocomposites, i.e Ca5(PO4)3OH/Fe3O4 (later called nHAp/IO) functionalised with microRNAs (nHAp/IO@miR-21/124) was tested. In vitro studies were performed using a direct co-culture system of MC3T3-E1 pre-osteoblast and 4B12 pre-osteoclasts. The analysis included determination of nanocomposite influence on cultures morphology (confocal imaging), viability and metabolic activity (Alamar Blue assay). Pro-osteogenic signals were identified at mRNA, miRNA and protein level with RT-qPCR, Western blotting and immunocytochemistry. Biocompatibility of biomaterials was tested using bilateral cranial defect performed on a senescence-accelerated mouse model, ie SAM/P6 and Balb/c. The effect of biomaterial on the process of bone healing was monitored using microcomputed tomography. RESULTS: The nanocomposites promoted survival and metabolism of bone cells, as well as enhanced functional differentiation of pre-osteoblasts MC3T3-E1 in co-cultures with pre-osteoclasts. Differentiation of MC3T3-E1 driven by nHAp/IO@miR-21/124 nanocomposite was manifested by improved extracellular matrix differentiation and up-regulation of pro-osteogenic transcripts, ie late osteogenesis markers. The nanocomposite triggered bone healing in a cranial defect model in SAM/P6 mice and was replaced by functional bone in Balb/c mice. CONCLUSION: This study demonstrates that the novel nanocomposite nHAp/IO can serve as a platform for therapeutic miRNA delivery. Obtained nanocomposite elicit pro-osteogenic signals, decreasing osteoclasts differentiation, simultaneously improving osteoblasts metabolism and their transition toward pre-osteocytes and bone mineralisation. The proposed scaffold can be an effective interface for in situ regeneration of osteoporotic bone, especially in elderly patients.

Antiepileptic Stiripentol May Influence Bones.

Bone structure abnormalities are increasingly observed in patients chronically treated with antiepileptic drugs (AEDs). The majority of the available data concern older conventional AEDs, while the amount of information regarding newer AEDs, including stiripentol, is limited. The aim of the study was to assess the effect of stiripentol on bones. For 24 weeks, male Wistar rats, received 0.9% sodium chloride (control group) or stiripentol (200 mg/kg/day) (STP group). In the 16th week of the study, we detected lower serum PINP levels in the STP group compared to the control group. In the 24th week, a statistically significant lower 1,25-dihydroxyvitamin D3 level, higher inorganic phosphate level and higher neutrophil gelatinase-associated lipocalin (NGAL) levels in serum were found in the STP group compared to the control. Micro X-ray computed tomography of the tibias demonstrated lower bone volume fraction, lower trabecular thickness, higher trabecular pattern factor and a higher structure model index in the stiripentol group. Considering the results of this experiment on rats which suggests that long-term administration of stiripentol may impair the cancellous bone microarchitecture, further prospective human studies seem to be justified. However, monitoring plasma vitamin D, calcium, inorganic phosphate and kidney function in patients on long-term stiripentol therapy may be suggested.

Effects of efavirenz and tenofovir on bone tissue in Wistar rats.

BACKGROUND: Clinical trials indicate an increased risk of osteoporosis and bone fractures in people infected with human immunodeficiency virus (HIV). The pathogenesis of bone disturbances in HIV-positive patients is unknown, but it is suggested that antiretroviral drugs may be involved. OBJECTIVES: To assess the effects of efavirenz (EF) and tenofovir (T) on bone remodeling in rats. MATERIAL AND METHODS: The study involved 36 male Wistar rats divided into 3 groups, receiving normal saline (control group - group C), efavirenz (group EF) or tenofovir disoproxil (group T). RESULTS: After 24 weeks of the study, the following observations were made: In blood serum of the EF group compared to group C, there were increased levels of tartrate-resistant acid phosphatase form 5b (TRAP) and inorganic phosphorus. In the densitometric examination, group T showed a lower total body (TB) bone mineral density (BMD) than group C. In the immunohistochemical assessment, group EF showed a higher intensity and extension of anti-tartrate resistant acid phosphatase antibodies (abTRAP) compared to group C. In the histopathological examination of the second lumbar vertebra (L2), group EF showed a lower bone surface/volume ratio (BS/BV) and higher trabecular thickness (Tb.Th) than the control group. In the histopathological examination of the femur, a lower bone surface/tissue volume (BS/TV) and lower trabecular number (Tb.N) were found in group T compared to in group C. A lower value of the Young's modulus was observed in the four-point bending trial in groups EF and T compared to group C. CONCLUSIONS: The results of this study indicate that EF affects bone microarchitecture and leads to impaired biomechanical properties of bones in rats. Additionally, the negative effect of T on bone tissue was confirmed.

Laser Texturing as a Way of Influencing the Micromechanical and Biological Properties of the Poly(L-Lactide) Surface.

Laser-based technologies are extensively used for polymer surface patterning and/or texturing. Different micro- and nanostructures can be obtained thanks to a wide range of laser types and beam parameters. Cell behavior on various types of materials is an extensively investigated phenomenon in biomedical applications. Polymer topography such as height, diameter, and spacing of the patterning will cause different cell responses, which can also vary depending on the utilized cell types. Structurization can highly improve the biological performance of the material without any need for chemical modification. The aim of the study was to evaluate the effect of CO2 laser irradiation of poly(L-lactide) (PLLA) thin films on the surface microhardness, roughness, wettability, and cytocompatibility. The conducted testing showed that CO2 laser texturing of PLLA provides the ability to adjust the structural and physical properties of the PLLA surface to the requirements of the cells despite significant changes in the mechanical properties of the laser-treated surface polymer.

Laser-modified PLGA for implants: in vitro degradation and mechanical properties.

PURPOSE: Irradiations by CO2 laser poly(lactic-co-glycolic acid) surface lead to alterations of physicochemical properties of a copolymer. Effects of PLGA irradiations are results of photochemical and photothermal processes leading to polymer degradation. The scale of the degradation depends on the inducted surface modification. Hence the main goal of presented studies was to define the influence of CO2 laser irradiation with different process parameters, inducing three cases of surface modification, on mechanical properties and topography of PLGA during degradation in the aqueous environment. METHODS: Hydrolytic degradation were performed in distilled (demineralized) water. Mechanical properties were conducted in accordance with the PN-EN ISO 527-3:1998 standard. pH of incubating solution, specimens' topography, mass and geometrical dimensions were controlled during process. RESULTS: During the hydrolytic degradation, gradual changes in failure mode were observed from ductile failure characteristic for untreated PLGA to brittle failure of incubated PLGA regardless of the case of triggered modification. Tensile strength decreased with degradation time regardless of the case of surface modification with insignificant fluctuation in means Young's moduli. pH for each case decreased and topography od specimens become smoother with incubation time. CONCLUSIONS: PLGA surface modification by CO2 laser below the ablation threshold (P1) and at the ablation threshold (P2) leaded to surface functionalization, however, irradiation above the ablation threshold (P3) caused marked degradation of PLGA and accelerated specimens disintegration during incubation in the aquatic environment.

Cornelian cherry extract ameliorates osteoporosis associated with hypercholesterolemia in New Zealand rabbits.

BACKGROUND: Results of animal studies show that a high-cholesterol diet increases bone resorption and decreases bone formation, thus leading to osteoporosis. Previously, we reported on the beneficial influence of Cornelian cherry (Cornus mas L.) fruit on lipid profile in an animal model of diet-induced hipercholesterolemia. OBJECTIVES: To investigate the influence of Cornus mas L. extract and loganic acid (LA) on cholesterol-induced bone changes. MATERIAL AND METHODS: The study was conducted on 50 New Zealand rabbits. The animals were given either standard chow (group P) or the same standard chow enriched with 1% cholesterol (other groups). Additionally, the group CHOL+EX received Cornus mas L. extract, group CHOL+LA - loganic acid, and group CHOL+SIM - simvastatin. Serum concentration of bone turnover markers, bone mineral density (BMD) and bone micro-computed tomography (microCT) were assessed. RESULTS: In the CHOL group, a decrease in osteocalcin (OC) and an increase in C-terminated telopeptide of type I collagen (CTX) levels were detected (CHOL vs P 0.674 ±0.159 ng/mL vs 1.003 ±0.297 ng/mL and 10.049 ±1.276 ng/mL vs 7.721 ±1.187 ng/mL, respectively). The EX and LA ameliorated cholesterol-induced changes in serum OC (0.857 ±0.160 ng/mL and 1.103 ±0.356 ng/mL, respectively) and CTX (7.735 ±1.045 ng/mL and 8.128 ±1.106 ng/mL, respectively). There was a significant decrease in femoral BMD in CHOL group (0.429 ±0.11 g/cm² vs 0.449 ±0.020 g/cm²). The EX and LA ameliorated those changes (0.458 ±0.016 g/cm² and 0.449 ±0.021 g/cm², respectively). The microCT revealed increased bone volume ratio (BV/TV) and trabecular thickness (Tb.Th.) in the CHOL+EX group. CONCLUSIONS: Cornus mas L. inhibited bone resorption and stimulated bone formation, thereby preventing the development of cholesterol-induced osteoporosis.

Effect of dissection on the mechanical properties of human ascending aorta and human ascending aorta aneurysm.

PURPOSE: The aim of the presented work is to determine (i) mechanical properties of the ascending aorta wall (DAA) and the wall of the ascending aortic aneurysm (DAAA), in which spontaneous dissection resulting from the evolving disease occurred, and (ii) the strength of the interface between the layers in the above-mentioned vessels. METHODS: The mechanical tests were divided into two steps. In the first step the mechanical properties of the of DAA and DAAA walls were examined on the basis of uniaxial stretching until rapture. In the next step the mechanical parameters of the interface between layers of DAA and DAAA walls were determined by the peeling test. RESULTS: Higher values of tensile strength (  max) and Young's modulus (E) were obtained for the DAAA group, to which the dissecting wall of the ascending aortic aneurysm was classified. For circumferential samples, the difference between the DAAA and DAA groups was 39% in the case of tensile strength and 70% in the case of the Young's modulus. CONCLUSIONS: Summarizing, the studies performed showed that the dissection process is different in the case of the ascending aortic aneurysm wall and the ascending aorta wall. The wall of the ascending aortic aneurysm is more susceptible to dissection, as evidenced by lower values of the mechanical parameters of the interface between the intima and the media-adventitia complex. The obtained results of mechanical properties tests confirm that dissection and aneurysm should be treated as separate disease entities that may coexist with each other.

Study of Surface Structure Changes for Selected Ceramics Used in the CAD/CAM System on the Degree of Microbial Colonization, In Vitro Tests.

In the article has been presented an analysis of susceptibility of selected dental materials, made in the CAD/CAM technology. The morphology and structural properties of selected dental materials and their composites were determined by using XRPD (X-ray powder diffraction) techniques, as well as the IR (infrared) spectroscopy. Moreover, an adhesion as well as development of biofilm by oral microorganisms has been studied. It has been shown that a degree of the biofilm development on the tested dental materials depended on microorganism genus and species. Streptococcus mutans has demonstrated the best adhesion to the tested materials in comparison with Candida albicans and Lactobacillus rhamnosus. However, the sintered materials such as IPS e.max® and the polished IPS e.max® have showed the best "anti-adhesive properties" in relation to S. mutans and L. rhamnosus that have not formed the biofilm on the polished IPS e.max® sample. Furthermore, S. mutans have not formed the biofilm on both surfaces. On the contrary to S. mutans and L. rhamnosus, C. albicans has demonstrated the adhesive properties in relation to the above-mentioned surfaces. Moreover, in contrast to S. mutans and C. albicans, L. rhamnosus has not formed the biofilm on the polished IPS Empress material.

The impact of configuration of the Ilizarov fixator on its stiffness and the degree of loading of distraction rods.

BACKGROUND: The mechanical parameters of the Ilizarov fixator are influenced by many factors related to its spatial configuration. The aim of this study was to experimentally evaluate the impact of the type of implant and the number of distraction rods on the uniformity of loading of distraction rods and stiffness coefficients of the Ilizarov fixator. METHODS: The tests were carried out on a physical model. The model was mounted in a universal loading station MTS 858 Mini Bionix. Forces in distraction rods are measured with the use of strain gauge force transducers. Displacements of bone fragments were measured by means of digital image correction. FINDINGS: In the case of a fixator with 3 distraction rods, configuration of implants has no statistically significant effect on the forces occurring in distraction rods. In the case of a fixator with 4 distraction rods, there are statistically significant differences in the forces in distraction rods. The highest transverse stiffness coefficients occurs in the system with 4 distraction rods and the configuration of 1K1S implants, while the smallest transverse stiffness coefficients occurs in the fixator with 4 distraction rods and the configuration of 0K1S implants. INTERPRETATION: Based on the results of experiments on the physical model, we observed an asymmetry in the distribution of forces transmitted through distraction rods. The configuration with 3 distraction rods provides more uniform distribution of forces in distraction rods and reduces the impact of the implant configuration on transverse stiffness coefficients. The use of a configurations with 4 rods may be advantageous when we want to obtain greater transverse stiffness coefficients of a system consisting of the fixator and fragments of the lengthened bone.

Wall stress correlates with intimal entry tear localization in Type A aortic dissection.

OBJECTIVES: The risk of aortic dissection should be assessed based not only on the aortic diameter, but also on other biomechanical parameters that have an impact on the stress in the aortic wall. This study evaluates very rare clinical scenarios of patients with both pre- and post-dissection computed tomography (CT) images and evaluates whether an increased wall stress correlates with the localization of an intimal entry tear in Type A aortic dissection. METHODS: CT-angiography images of 4 patients performed shortly prior to and after developing Type A aortic dissection were evaluated. The stress distribution in the pre-dissection aortas was evaluated using the finite elements method. Then, the areas of high stress in the pre-dissection aortas were compared to the localization of the intimal entry tears in the dissected vessels. RESULTS: In all the patients, the pre-dissection areas of high wall stress correlated with the location of the intimal tears. The highest stress was not observed in the most dilated segments of the aorta but was predominantly found in the areas of an abrupt change in the geometry of the aorta. CONCLUSIONS: Wall stress can indicate the areas susceptible to the formation of an intimal tear and subsequent aortic dissection. Stress analysis may be a valuable tool to predict the risk of aortic dissection in patients with aortic dilatation.

Three-dimensional printing as a technology supporting the treatment of lower limb deformity and shortening with the Ilizarov method.

BACKGROUND: Treatment of multiplanar deformities, especially in younger children, requires construction of a complex Ilizarov fixator, frequently with small dimensions. The aim of this study is to verify clinical application of a3D-printed bone model in treatment with the Ilizarov method. METHODS: The study involved a 6-year-old child in whom clinical and radiological examination revealed multiplanar deformity of the right leg. Then, 3D models of individual bones were printed by means of additive manufacturing and were used as a scaffold to install the Ilizarov apparatus. To compare the expected and factual axial correction and lengthening, we measured spatial orientation of bone fragments three times. The factual axial correction and lengthening were determined with a photometric technique. RESULTS: Ilizarov fixator with a configuration developed using a 3D model of the treated bone was mounted on the patient's leg. Corticotomy was carried out at the proximal metaphysis of the right tibia, along with osteotomy of the right talus. The treatment resulted in a 3.5-cm lengthening of the limb and a 7° correction of valgus angle. The values of actual lengthening and axial correction were 4.1% lower than the expected values of these parameters. INTERPRETATION: Orthopedists should consider differences between the expected and actual lengthening and axial correction in planning treatment with the Ilizarov method. Three-dimensional printing is a useful technology that can be used to support treatment with the Ilizarov method.

The combined impact of mechanical factors on the wall stress of the human ascending aorta - a finite elements study.

BACKGROUND: Biomechanical factors influence stress in the aortic wall. The aim of this study was to assess how the diameter and shape of the vessel, blood pressure and longitudinal systolic aortic stretching (SAS) caused by the contraction of the myocardium influence stress in the aortic wall. METHODS: Three computational models of the non-dilated aorta and aneurysms of the ascending aorta and aortic root were created. Then, finite elements analyses were carried out. The models were subjected to blood pressure (120 mmHg and 160 mmHg) and longitudinal systolic aortic stretching (0 mm, 5 mm, 10 mm and 15 mm). The influence of wall elasticity was examined too. RESULTS: Blood pressure had a smaller impact on the stress than the SAS. An increase in blood pressure from120 mmHg to 160 mmHg increased the peak wall stress (PWS) on average by 0.1 MPa in all models. A 5 mm SAS caused a 0.1­0. 2 MPa increase in PWS in all the models. The increase in PWS caused by a 10mm and 15mmSAS was 0.2 MPa and 0. 4 MPa in the non-dilated aorta, 0.2­0.3 MPa and 0.3­0.5 MPa in the aneurysm of the ascending aorta, and 0.1­0.2 MPa and 0.2­0.3 MPa in the aortic root aneurysm model, respectively. The loss of elasticity of the aneurysmal wall resulted in an increase of PWS by 0.1­0.2 MPa. CONCLUSIONS: Aortic geometry, wall stiffness, blood pressure and SAS have an impact on PWS. However, SAS had the biggest impact on wall stress. The results of this study may be useful in future patient-specific computational models used to assess the risk of aortic complications.

Oral administration of kaempferol inhibits bone loss in rat model of ovariectomy-induced osteopenia.

BACKGROUND: Postmenopausal osteoporosis and osteoporotic fractures constitute an increasing problem in developing countries. Kaempferol, isolated from seeds of Cuscuta chinensis, is an active flavonoid inhibiting in vitro osteoclast activity. The aim of the presented research was an assessment of kaempferol effect on estrogen-deficiency-induced bone structure disturbances in rats. METHODS: The study was performed on 24 Wistar female rats divided into 3 groups: SHAM - rats undergoing a "sham" surgery, OVX-C - control group of animals that underwent ovariectomy, OVX-K - rats undergoing ovariectomy and receiving kaempferol for 8 weeks (from day 56 to day 112). RESULTS: In the OVX-K group, contrary to the OVX-C one, there was no significant decrease in femoral bone mineral density (BMD). A significant increase in Young's modulus was observed in the OVX-K group compared to the OVX-C (15.33±2.51GPa vs. 11.14±1.93GPa, p<0.05). A decreased bone turnover was detected in the OVX-K group. Tissue volume ratio (BV/TV) and trabecular bone perimeter were increased in the OVX-K group compared to the OVX-C one (0.241±0.037 vs. 0.170±0.022, p<0.05 and 15.52±2.78mm vs. 9.67±3.07mm, p<0.05, respectively). CONCLUSION: Kaempferol has a beneficial influence on estrogen-deficiency-induced disturbances of bone structure in rats.

Effect of elliptical deformation of the acetabulum on the stress distribution in the components of hip resurfacing surgery.

Hip resurfacing surgery is a matter of controversy. Some authors present very good late results of 99% survival outcomes. However, national records of implants point to the series of complications connected with biomechanical flaws of the implant. These results implicate the experimental research on biomechanical properties of HRS. The aim of the research was to define the nature of cooperation between the components of hip resurfacing surgery (HRS) and the influence of the deformation of acetabulum, the size of the implant and the nature of the bone surface on the stress distribution in the acetabulum and the femoral component. The calculations were run with the use of the finite element method (FEM), using the ANSYS bundle for this purpose. Four decrete models of the studied system were made: a model with the elements of the system connected with glue, a perfect spherical model with cooperating surfaces, a model reflecting an elliptical deformation of the acetabulum, and a model with different sizes of the implant. The results indicate that the stress values obtained for models with the ideally spherical acetabulum cannot cause significant deformation of cooperating implants. In the case of loads of the elliptically deformed acetabulum significant point stress concentrations can be observed in the spots of joint. The size of the acetabular and femoral components of HRS has influence on the stress concentration on the internal surface of the acetabulum as well as in the bone tissue surrounding the madrel of the femoral component. Moreover, physical properties of the base surface surrounding the HRS components have influence on the size of stress in the acetabulum and the femoral component.

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

BACKGROUND: Significant developments in additive manufacturing technology have occurred in recent years. 3D printing techniques can also be helpful in the Ilizarov method treatment. OBJECTIVES: The aim of this study was to evaluate the usefulness of 3D printing technology in the Ilizarov method treatment. MATERIAL AND METHODS: Physical models of bones used to plan the spatial design of Ilizarov external fixator were manufactured by FDM (Fused Deposition Modeling) spatial printing technology. Bone models were made of poly(L-lactide) (PLA). RESULTS: Printed 3D models of both lower leg bones allow doctors to prepare in advance for the Ilizarov method treatment: detailed consideration of the spatial configuration of the external fixation, experimental assembly of the Ilizarov external fixator onto the physical models of bones prior to surgery, planning individual osteotomy level and Kirschner wires introduction sites. CONCLUSIONS: Printed 3D bone models allow for accurate preparation of the Ilizarov apparatus spatially matched to the size of the bones and prospective bone distortion. Employment of the printed 3D models of bone will enable a more precise design of the apparatus, which is especially useful in multiplanar distortion and in the treatment of axis distortion and limb length discrepancy in young children. In the course of planning the use of physical models manufactured with additive technology, attention should be paid to certain technical aspects of model printing that have an impact on the accuracy of mapping of the geometry and physical properties of the model. 3D printing technique is very useful in 3D planning of the Ilizarov method treatment.

The Negative Impact of Selective Activation of Retinoic Acid Receptors on Bone Metabolism and Bone Mechanical Properties in Rats.

BACKGROUND: Drug-induced osteoporosis is a significant health problem, as many drugs have deleterious effects on bone metabolism. Data from several studies concerning the influence of retinol on bone homeostasis are inconsistent. OBJECTIVES: The purpose of this study was to investigate the influence of tazarotene, a selective agonist of the retinoic acid receptor (RAR), on bone metabolism and bone mechanical properties in rats. MATERIAL AND METHODS: Sixteen male Wistar rats were assigned either to the group receiving tazarotene or to the control group. Serum biochemical markers of bone turnover (osteocalcin: OC, tartrate resistant acid phosphatase 5: TRACP5b, and osteoprotegerin: OPG) and the mechanical properties of bones were analyzed. RESULTS: The mean Young's modulus was 24% higher (p < 0.05) in the control group than in the group receiving tazarotene. The stiffness of femur bones was 25% lower (p < 0.05) in rats receiving tazarotene. Flexural yield stress was slightly (2%) decreased in the tazarotene group, but the difference was not statistically significant. In the tazarotene group significantly lower serum concentration of bone turnover markers were obeserved (TRACP5b: 0.86 ± 0.30 ng/mL vs. 2.17 ± 0.67 ng/mL, OC: 7.77 ± 2.28 ng/mL vs. 13.04 ± 3.54 ng/mL and OPG: 0.09 ± 0.04 ng/mL vs. 0.27 ± 0.10) than in the control group. CONCLUSIONS: Tazarotene worsened bone mechanical properties and inhibited bone turnover in rats. These results suggest that tazarotene has a negative impact on bone metabolism and that it exerts osteoporotic activity.