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Bagheri Z.S.,Ryerson University | El Sawi I.,Ryerson University | Bougherara H.,Ryerson University | Zdero R.,Ryerson University | Zdero R.,Martin Orthopaedic Biomechanics Laboratory
Journal of the Mechanical Behavior of Biomedical Materials

The current study is part of an ongoing research program to develop an advanced new carbon fiber/flax/epoxy (CF/flax/epoxy) hybrid composite with a "sandwich structure" as a substitute for metallic materials for orthopedic long bone fracture plate applications. The purpose of this study was to assess the fatigue properties of this composite, since cyclic loading is one of the main types of loads carried by a femur fracture plate during normal daily activities. Conventional fatigue testing, thermographic analysis, and scanning electron microscopy (SEM) were used to analyze the damage progress that occurred during fatigue loading. Fatigue strength obtained using thermography analysis (51% of ultimate tensile strength) was confirmed using the conventional fatigue test (50-55% of ultimate tensile strength). The dynamic modulus (E*) was found to stay almost constant at 47GPa versus the number of cycles, which can be related to the contribution of both flax/epoxy and CF/epoxy laminae to the stiffness of the composite. SEM images showed solid bonding at the CF/epoxy and flax/epoxy laminae, with a crack density of only 0.48% for the plate loaded for 2 million cycles. The current composite plate showed much higher fatigue strength than the main loads experienced by a typical patient during cyclic activities; thus, it may be a potential candidate for bone fracture plate applications. Moreover, the fatigue strength from thermographic analysis was the same as that obtained by the conventional fatigue tests, thus demonstrating its potential use as an alternate tool to rapidly evaluate fatigue strength of composite biomaterials. © 2014 Elsevier Ltd. Source

Watanabe Y.,Teikyo University | Matsushita T.,Teikyo University | Bhandari M.,McMaster University | Zdero R.,Martin Orthopaedic Biomechanics Laboratory | And 2 more authors.
Journal of Orthopaedic Trauma

Low-intensity pulsed ultrasound (LIPUS) is a relatively new technique for the acceleration of fracture healing in fresh fractures and nonunions. It has a frequency of 1.5 MHz, a signal burst width of 200 μs, a signal repetition frequency of 1 kHz, and an intensity of 30 mW/cm2 In 1994 and 1997, two milestone double-blind randomized controlled trials revealed the benefits of LIPUS for the acceleration of fracture healing in the tibia and radius. They showed that LIPUS accelerated the fracture healing rate from 24% to 42% for fresh fractures. Some literature, however, has shown no positive effects. The beneficial effect of acceleration of fracture healing by LIPUS is considered to be larger in the group of patients or fractures with potentially negative factors for fracture healing. The incidence of delayed union and nonunion is 5% to 10% of all fractures. For delayed union and nonunion, the overall success rate of LIPUS therapy is approximately 67% (humerus), 90% (radius/radius-ulna), 82% (femur), and 87% (tibia/tibia-fibula). LIPUS likely has the ability to enhance maturation of the callus in distraction osteogenesis and reduce the healing index. The critical role of LIPUS for fracture healing is still unknown because of the heterogeneity of results in clinical trials for fresh fractures and the lack of controlled trials for delayed unions and nonunions. © 2010 by Lippincott Williams & Wilkins. Source

Zdero R.,Martin Orthopaedic Biomechanics Laboratory | Zdero R.,Ryerson University | Schemitsch E.H.,Martin Orthopaedic Biomechanics Laboratory
Journal of Orthopaedic Trauma

Objectives: The aim of the study was to investigate how superior entry point varies with tibial rotation and to identify landmarks that can be used to identify suitable radiographs for successful intramedullary nail insertion. Methods: The proximal tibia and knee were imaged for 12 cadaveric limbs undergoing 5 increments of internal and external rotation. Medial and lateral arthrotomies were performed, the ideal superior entry point was identified, and a 2-mm Kirschner wire inserted. A second Kirschner wire was sequentially placed at the 5-mm and then the 10-mm position, both medial and lateral to the initial Kirschner wire. Radiographs of the knee were obtained for all increments. The changing position of the ideal nail insertion point was recorded. Results: A 30 arc (range, 25-40) provided a suitable anteroposterior radiograph. On the neutral anteroposterior radiograph, the Kirschner wire was 54% 6 1.5% (range, 51-56%) from the medial edge of the tibial plateau. For every 5 of rotation, the Kirschner wire moved 3% of the plateau width. During external rotation, a misleading medial entry point was obtained. A fibular bisector line correlated with an entry point that was ideal or up to 5 mm lateral to this but never medial. The film that best showed the fibular bisector line was between 0 and 10 of internal rotation of the tibia. Conclusions: The fibula head bisector line can be used to avoid choosing external rotation views and, thus, avoid medial insertion points. The current results may help the surgeon prevent malalignment during intramedullary nailing in proximal tibial fractures. Copyright © 2011 by Lippincott Williams & Wilkins. Source

Bagheri Z.S.,Ryerson University | El Sawi I.,Ryerson University | Schemitsch E.H.,Martin Orthopaedic Biomechanics Laboratory | Schemitsch E.H.,University of Toronto | And 3 more authors.
Journal of the Mechanical Behavior of Biomedical Materials

This work is part of an ongoing program to develop a new carbon fiber/flax/epoxy (CF/flax/epoxy) hybrid composite material for use as an orthopaedic long bone fracture plate, instead of a metal plate. The purpose of this study was to evaluate the mechanical properties of this new novel composite material. The composite material had a "sandwich structure", in which two thin sheets of CF/epoxy were attached to each outer surface of the flax/epoxy core, which resulted in a unique structure compared to other composite plates for bone plate applications. Mechanical properties were determined using tension, three-point bending, and Rockwell hardness tests. Also, scanning electron microscopy (SEM) was used to characterize the failure mechanism of specimens in tension and three-point bending tests. The results of mechanical tests revealed a considerably high ultimate strength in both tension (399.8. MPa) and flexural loading (510.6. MPa), with a higher elastic modulus in bending tests (57.4. GPa) compared to tension tests (41.7. GPa). The composite material experienced brittle catastrophic failure in both tension and bending tests. The SEM images, consistent with brittle failure, showed mostly fiber breakage and fiber pull-out at the fractured surfaces with perfect bonding at carbon fibers and flax plies. Compared to clinically-used orthopaedic metal plates, current CF/flax/epoxy results were closer to human cortical bone, making the material a potential candidate for use in long bone fracture fixation. © 2013 Elsevier Ltd. Source

Shah S.,Ryerson University | Shah S.,Martin Orthopaedic Biomechanics Laboratory | Bougherara H.,Ryerson University | Schemitsch E.H.,Martin Orthopaedic Biomechanics Laboratory | And 3 more authors.
Medical Engineering and Physics

Femurs are the heaviest, longest, and strongest long bones in the human body and are routinely subjected to cyclic forces. Strain gages are commonly employed to experimentally validate finite element models of the femur in order to generate 3D stresses, yet there is little information on a relatively new infrared (IR) thermography technique now available for biomechanics applications. In this study, IR thermography validated with strain gages was used to measure the principal stresses in the artificial femur model from Sawbones (Vashon, WA, USA) increasingly being used for biomechanical research. The femur was instrumented with rosette strain gages and mechanically tested using average axial cyclic forces of 1500N, 1800N, and 2100N, representing 3 times body weight for a 50kg, 60kg, and 70kg person. The femur was oriented at 7° of adduction to simulate the single-legged stance phase of walking. Stress maps were also obtained using an IR thermography camera. Results showed good agreement of IR thermography vs. strain gage data with a correlation of R2=0.99 and a slope=1.08 for the straight line of best fit. IR thermography detected the highest principal stresses on the superior-posterior side of the neck, which yielded compressive values of -91.2MPa (at 1500N), -96.0MPa (at 1800N), and -103.5MPa (at 2100N). There was excellent correlation between IR thermography principal stress vs. axial cyclic force at 6 locations on the femur on the lateral (R2=0.89-0.99), anterior (R2=0.87-0.99), and posterior (R2=0.81-0.99) sides. This study shows IR thermography's potential for future biomechanical applications. © 2012 IPEM. Source

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