Berivan Cecen

Anatomical and biomechanical evaluation of the tension band technique in patellar fractures

Tension band wiring for patellar fractures is common, but some recent reports refer to disadvantages of this approach. Our anatomical and biomechanical study focused on use of tension band techniques in patellar fractures. The anatomy of the patella and tendon insertion was examined with knee magnetic resonance imaging (MRI) and correlated with the technical requirements of the tension band. Tension band wiring over tendinous tissue was simulated and calculated with a cyclic biomechanical test on cow patellae. According to tension band templating on the MRI section, Kirschner wire insertion was needed for the tension band to turn over the tendinous tissue. The tension band became more stable while turning over less tendinous tissue and more adjacent bone surface. Nevertheless, cyclic loading tests indicate that all tension band applications in this study lose their initial stability. Excessive initial compression by the tension band resulted in bending of the Kirschner wire and thus reduction failure. For optimum stabilisation, tension force transfer should be done directly on bone or at least material that protects the tendon would be useful.RésuméLa tension des fils métalliques lors de l’ostéosynthèse par hauban des fractures de rotules est habituellement utilisée, mais certains travaux en montrent les désavantages. Cette étude anatomique et biomécanique a été centrée sur cette pratique du hauban dans les fractures de la rotule. L’anatomie de la rotule et des insertions tendineuses ont été étudiées et corrélées avec les nécessités de tension. La tension de ce hauban mis en place au dessus des structures tendineuses a été évaluée par des tests biomécaniques sur des rotules de vaches. Selon l’insertion des broches de Kirschner, après étude IRM, il est nécessaire de serrer les fils du hauban sur les structures tendineuses mais, ce hauban est beaucoup plus stable que les tissus tendineux adjacents à l’os. Cependant, les tests de mise en charge nous montrent que ces haubans perdent leur stabilité initiale dès qu’une tension importante entraîne une plicature des broches de Kirschner et un échec de la réduction. Pour une stabilisation optimum, les forces de serrage du hauban doivent être directement appliquées sur l’os ou, tout au plus, au niveau de l’insertion tendineuse au plus près du matériel.

The stiffness characteristics of hybrid Ilizarov fixators

The use of hybrid Ilizarov models around femoral area is gaining clinical popularity lately. Hybrid systems show different mechanical properties. The purpose of this report is to examine the stiffness characteristics of the C-arch and half-pins on the hybrid Ilizarov fixators. Eight models that included standard Ilizarov and hybrid models were applied to six femoral sawbones. The distal part of fixation was composed of a two-ring frame applied identically to all bones. The difference of the configuration was at the proximal part, where half-pins with or without C-arches were either added to the proximal two-ring frame or replaced the proximal one- or two-ring frame. Osteotomy was performed in the femoral diaphysis and the bone was distracted 2cm. The stability of the system was tested with the axial compression testing machine. Displacements between the adjacent fracture sides were measured with the video extensometer in three dimensions. We found that proximal half-pin applications alone had less stiffness, but half-pins with C-arch had more stiffness than the model including only half-pins. Additional half-pins onto one- or two-ring frames had more longitudinal stiffness, but this system showed weak resistance against transverse displacement.

Biocompatibility and biomechanical characteristics of loofah based scaffolds combined with hydroxyapatite, cellulose, poly-l-lactic acid with chondrocyte-like cells

The current study reports the biocompatibility and biomechanical characteristics of loofah-based scaffolds combined with hydroxyapatite (HA), cellulose, poly-l-lactic acid (PLLA) with chondrocytes-like cells. Scanning electron microscope (SEM) micrographs of the scaffolds showed that the addition of PLLA usually resulted in an increase in cells attachment on scaffolds. Mechanical and elemental analyzes were assessed using tensile test and Energy Dispersive X-ray spectrometry (EDS), respectively. In summary, we showed that the loofah+PLLA+HA scaffolds perform significantly better than other loofah-based scaffolds employed in terms of increasing a diversity of mechanical properties including tensile strength and Youngs modulus. Based on the analysis of the differential scanning calorimetry (DSC) thermograms and EDS spectrums that give an idea about the calcium phosphate (CaP) ratios, the improvement in the mechanical properties could principally be recognized to the strong interaction formed between loofah, PLLA and HA. The viability of chondrocytes on loofah-based scaffolds was analyzed by XTT tests. However, none of the scaffolds have proved to be toxic in metabolic activity. The histological evaluation obtained by hematoxylin and eosin (H&E), Masson trichrome, toluidine blue and immunohistochemistry methods showed that cells in all scaffolds produced extracellular matrix that defined proteoglycan and type I-II collagens. The results of this study suggest that the loofah-based scaffold with desirable properties can be considered as an ideal candidate for cartilage tissue engineering applications.

Biocompatibility of MG-63 cells on collagen, poly-L-lactic acid, hydroxyapatite scaffolds with different parameters

Purpose In this study, osteoblast-like MG-63 cells were cultured on 3 different scaffold types composed of (a) collagen + poly-L-lactic acid (PLLA), (b) collagen + hydroxyapatite (HA; 30°C) or (c) collagen + hydroxyapatite (HA; 37°C) and produced with different porosities. Methods Biomechanical properties of the scaffolds were characterized by tensile strength measurements. Properties of the cell-seeded scaffolds were evaluated with scanning electron microscopy (SEM). Cell adhesion and proliferation capacities were evaluated. Alkaline phosphatase (ALP) levels in media were measured. Transmission electron microscopy (TEM) and histological analyses were used to assess morphological characteristics. Results Our results showed that collagen-based PLLA and HA scaffolds have good cell biocompatibility. MTT test showed that the scaffolds exhibited no cytotoxicity. According to the force and displacement data, collagen + HA at 37°C showed the highest mechanical strength and displacement. Conclusion The results suggest that collagen-based PLLA and HA scaffolds might improve osteoblastic growth in vitro and have biomaterial integration potential in possible therapeutic approaches for future clinical studies.

Rigid fixation of the lumbar spine alters the motion and mechanical stability at the adjacent segment level.

OBJECTIVES This study aims to examine the motion and stability of the adjacent segment following rigid fixation of the lumbar spine. MATERIALS AND METHODS The study included 17 fresh-frozen lamb lumbar spines (including the sacrum to T12). Biomechanical testing was performed using an axial compression testing machine. Axial compression was applied to all the specimens using a loading speed of 5 mm min-1. A specifically designed fixture was used to generate torque ≤8400 Nmm. The fixture was used with each specimen to achieve flexion and extension, axial neutral compression, and right and left bending. All specimens were tested intact, and again after implantation using posterior pedicle screws and rod fixation. During testing intervertebral displacement at the adjacent level (L5-S1) was recorded continuously via extensometry. RESULTS Axial compression and superior-inferior displacement were lower in the adjacent segment (L5-S1) than anterior-posterior displacement following rigid fixation. Statistical analysis showed that there was a numerical difference and a significant change between the intact spine and the adjacent segment in the axial compression and extension positions (p<0.027). The intact spines demonstrated the maximum displacement and the difference in extension positions were significant (p<0.015). CONCLUSION Rigid fixation of the lumbar spine altered the range of motion at the adjacent segment level. As such, abnormal stress on the adjacent segment causes spinal instability, which may subsequently cause facet joint degeneration and low back pain.

The Effect of Autologous Platelet Rich Plasma in the Treatment of Achilles Tendon Ruptures: An Experimental Study on Rabbits

BACKGROUND Achilles tendon ruptures are characterized by a long recovery period, high re-rupture rate and late return to work. To overcome these difficulties and augment tendon repair, many agents have been used. AIMS To determine the effect of autologous platelet rich plasma (PRP) in the treatment of Achilles tendon ruptures in rabbits. STUDY DESIGN Animal experimentation. METHODS The study included 14 New Zealand albino rabbits that were divided randomly into 2 groups, A and B, each containing seven rabbits. On day zero, all 28 Achilles tendons were tenotomized and repaired. In group A, the tendons were injected with PRP post-surgery, whereas those in group B were left untreated. On day 28, the right tendons in both groups were examined histopathologically via both light and electron microscopy, and the left tendons were subjected to biomechanical testing. RESULTS The histological and biomechanical findings in both light and electron microscopy in group A were better than those in group B, but the difference was not significant. According to Tangs scale, the mean value in Group A was 3.57, while it was 3.0 in Group B. The mean value of Group A for the length of collagen bands was 48.09 nm while the mean value of Group B was 46.58 nm (p=0.406). In biomechanical tests, although stiffness values were higher in group A, the difference between groups was not significant. In addition, maximum load values did not differ between groups A and B. CONCLUSION PRP had no effect on the healing process 28 days post-Achilles tendon rupture.

The primary factor for suture configuration at rotator cuff repair: Width of mattress or distance from tear edge

Objectives The aims of this study was first to investigate whether the bite size or the bite distance from the tear edge is of primary importance in mattress suture configuration for rotator cuff repair. Secondly, whether the use of a 450 left side bent Arthro-Pierce™ (Smith & Nephew, Andover, USA) during suture passage can be more effective on the strength of the configuration compared to a straight Arthro-Pierce™. Materials and methods Twenty-eight bovine infraspinatus muscle tendons were randomized into four groups. Group 1; 5 mm wide ‘bite size’ × 15 mm length ‘distance from the tear edges mattress’; Group 2: 7.5 mm × 10 mm; Group 3: 15 mm × 5 mm ‘using straight Arthro-Pierce™’ and Group 4: 5 mm × 15 mm using left sided 450 bent Arthro-Pierce™. The repair specimens underwent cyclic loading prior to loading the failure testing. Cyclic elongation (mm), peak-to-peak displacement (mm), ultimate load (N), stiffness (N/mm) and failure mode were recorded for each specimen. Results The mean ultimate load in Group 1 was higher compared to group 3. The peak to peak displacement was higher in Group 4 compared to Group 1 (p < 0.05). The predominant failure mode in Groups 1, 2 and 4 was suture rupture. The Group 3 most specimens failed due to suture cut through the tendon. Conclusion Bite size from the edge of the tendon seems to be more important than the width of the mattress. The curve of the suture passing device may also have an effect on the strength of the suture tendon interface.

In vivo investigation of calcium phosphate coatings on Ti6-Al-4V alloy substrates using lactic acid - sodium lactate buffered synthetic body fluid

OBJECTIVE The aim of this study was to evaluate the mode of failure and biomechanical characteristics of Ti-6Al-4V anchors biomimetically coated with calcium phosphate (CaP) for soft tissue fixation to bone in an animal model. METHODS The current study included 14 adult New Zealand white rabbits equally divided into two groups. Calcium phosphate-coated Ti-6Al-4V anchors were used in the test group and non-coated Ti-6Al-4V anchors in the control group. A new approach was applied to synthesize the CaP coatings via the biomimetic growth in the Lac-SBF containing Ca(2+) and PO4(3-) ions, Na-lactate and lactic acid (HL). Titanium anchors were implanted into the right tibia, followed by biomechanical tensile strength tests. Histological studies were carried out after removal of anchors (bone-implant surface). RESULTS The CaP-coated Ti-6Al-4V anchors had significantly higher tensile strength (p=0.003) and displacement values (p=0.004) than the non-coated anchors. Control group scores were higher than those of the test group (14 and 9, respectively) in tensile strength tests. CONCLUSION The new CaP coating can be used in orthopedic surgery as catalyzer to improve bone ingrowth. We believe that our research will form a model for further research on biomimetic coatings on Ti-6Al-4V substrates.

Three-dimensional silk impregnated HAp/PHBV nanofibrous scaffolds for bone regeneration

ABSTRACT Three-dimensional silk fibroin impregnated poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) nanofibrous scaffolds with or without hydroxyapatite (HAp) were prepared by wet-electrospinning method followed by freeze-drying. Scaffolds with cotton wool-like structure have the average fiber diameter of 450–850 nm with 80–85% porosity. In-vitro cell culture tests using MG-63 osteosarcoma human cells revealed improved cell viability, alkaline phosphatase (ALP) activity and total cellular protein amount on the silk impregnated scaffolds compared to PHBV and HAp/PHBV scaffolds after 10 days of cell culture. Immunohistochemical analyses on the silk impregnated scaffolds showed that HAp triggered cell penetration and type I collagen production. Besides, HAp mineralization tendency increased with a decrease in percent crystallinity of the scaffolds comprising HAp and silk after 4 weeks of incubation in simulated body fluid. Consequently, cotton wool-like HAp/PHBV-SF scaffold would be a promising candidate as a bone-filling material for tissue regeneration. GRAPHICAL ABSTRACT

Permeability mapping of gelatin methacryloyl hydrogels

We report the development of an efficient, customized spherical indentation-based testing method to systematically estimate the hydraulic permeability of gelatin methacryloyl (GelMA) hydrogels fabricated in a wide range of mass concentrations and photocrosslinking conditions. Numerical simulations and Biots theory of poroelasticity were implemented to calibrate our experimental data. We correlated elastic moduli and permeability coefficients with different GelMA concentrations and crosslinking densities. Our model could also predict drug release rates from the GelMA hydrogels and diffusion of biomolecules into the three-dimensional GelMA hydrogels. The results potentially provide a design map for choosing desired GelMA-based hydrogels for use in drug delivery, tissue engineering, and regenerative medicine, which may be further expanded to predicting the permeability behaviors of various other hydrogel types. STATEMENT OF SIGNIFICANCE GelMA hydrogels have attracted increasing attention in recent years as matrices for cell cultures and biomolecule delivery. This inexpensive polymer is derived from gelatin functionalized with methacryloyl groups that can be crosslinked by photochemical reactions. Here we report the development of an efficient, customized testing method to systematically estimate the hydraulic permeability of GelMA hydrogels. Hydraulic permeability indicates the resistance of GelMA hydrogels to the movement of saturated fluid. We used the model to measure the elastic moduli and permeability coefficients, providing a permeability map for various GelMA hydrogel formulations.