Jarosław Filipiak

The influence of bexarotene, a selective agonist of the retinoid receptor X (RXR), and tazarotene, a selective agonist of the retinoid acid receptor (RAR), on bone metabolism in rats

PURPOSE The purpose of this study was to investigate the influence of selective agonists of the retinoid receptor X (RXR) and the retinoid acid receptor (RAR) on bone metabolism in rats. METHODS Thirty six male Wistar rats were divided into three groups: receiving bexarotene, or tazarotene, or to control group. Serum biochemical markers of bone turnover (osteocalcin - OC, tartrate resistant acid phosphatase 5 - TRACP5b and osteoprotegerin - OPG) and mechanical properties of bones were analyzed. RESULTS There was a significant decrease in the femur index value in groups receiving tazarotene and bexarotene on Day 14 (8% and 20% respectively, p=0.0039). On Day 28, 14 days after discontinuation of tazarotene and bexarotene, the difference in femur indexes was still significant (4% for T1-6 and B1-6, p=0.0270). In the bexarotene group an increase in mean plasma osteocalcin level and mean plasma TRACP5b level was detected. In the tazarotene group the mean osteocalcin level remained unchanged and the mean plasma TRACP5b level decreased. An increased yield stress was detected in groups receiving retinoids comparing to controls after 14 days of tazarotene and bexarotene administration. CONCLUSION Although bexarotene and tazarotene administration caused decrease in the femur index, mechanisms responsible for that effect seem to be different. Our results suggest that bexaroten increases bone turnover. On the contrary, tazaroten seems to have inhibitory effect on bone turnover. A counter influence of selective RAR and RXR agonists on the bone turnover might be the reason for inconsistency in results from published research concerning the influence of retinoids on bone metabolism.

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.

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 Youngs 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.

Mechanical properties and dynamics of degradation of polylactide matrix composites with calcium and sodium alginate fibers

In the present article, new polylactide/alginate fibers composites were investigated. Composite pre-pregs were made by solution casting method. The aim of the study was to define physico-mechanical properties of developed materials. The scope of the studies included: examining the static mechanical properties, properties of the surface and their changes during degradation. Moreover, intensity of the release of degradation products to the environment and a change of the mass of examined samples were analyzed. Obtained results were evaluated taking into account possibility to use prepared composited as materials for vascular implants.

BIODEGRADABLE BLENDS WITH SHAPE MEMORY EFFECT AS MATERIALS FOR CARDIOVASCULAR IMPLANTS

Biodegradable, shape-memory polymers, which have ability to recover previously defined shape under the influence of an external stimulus opens up new perspectives for designing vascular implants, especially such as stents, and methods of their implantation [Yakacki, 2006]. Nevertheless, introduction of biodegradable stent, whose function must be maintained in the environment of the vascular system, under the conditions of constant blood flow and elevated temperature, requires knowledge of the structural material properties and its changes at various stages of degradation. The aim of the presented work was to prepare new biodegradable polymer blends for vascular stents, induce and measure their thermal shape memory, investigate their biocompatibility in vitro and dynamics of in vitro biodegradation.

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 patients 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.