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Fixation of distal fibular fractures: A biomechanical study of plate fixation techniques

Marvan J., Horak Z., Vilimek M., Horny L., Kachlik D., Baca W.

Acta of Bioengineering and Biomechanics

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2017

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Vol. 19, no. 1

33--39

EN

Ankle fractures are complex injuries with variable prognoses that depend upon many factors. The aim of the treatment is to restore the ankle joint biomechanical stability with maximum range of motion. Most ankle fractures are fibular fractures, which have a typical oblique fracture line in the distal fibula located in the area of the tibiofibular syndesmosis. The aim of this study was to simulate numerically several fixation techniques of the distal fibular fractures, evaluate their stability, determine their impact on surrounding tissue load, and correlate the results to clinical treatment experience. The following three models of fibular fracture fixation were used: (a) plate fixation with three screws attached above/below and lag screws, (b) plate fixation with two screws attached above/below and lag screws, and (c) three lag screws only. All three fracture fixation models were analyzed according to their use in both healthy physiological bone and osteoporotic bone tissue. Based on the results of Finite Element Analysis for these simulations, we found that the most appropriate fixation method for Weber-B1 fibular fractures was an unlocked plate fixation using six screws and lag screws, both in patients with physiological and osteoporotic bone tissue. Conversely, the least appropriate fixation method was an unlocked plate fixation with four screws and lag screws. Although this fixation method reduces the stress on patients during surgery, it greatly increased loading on the bone and, thus, the risk of fixation failure. The final fixation model with three lag screws only was found to be appropriate only for very limited indications.

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Biomechanics of Bone-Fracture Fixation by External Unilateral Mechatronic Ortopaedic Fixators

Choromański W., Leśniewska A.

Machine Dynamics Research

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2010

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Vol. 34, No. 2

78-86

EN

In the external fixation of fractured bone by means of bone-external fixation device fastened to the bone, an on-going concern has been determined the stress distribution at fracture as well as at fixation sides during the whole fracture healing process. In order to address this problem, it has been proposed to use Uunilateral Mechatronic Ortopaedic Fixators. Accordingly, the stress distribution has been computed by finite-element analysis. The analyses were performed under an axial, variable loaded boundary conditions, different fracture sizes and different value of a distance between bone and external fixator device to study the stress distribution. The results show that stresses in the external fixator device are higher at the beginning of fracture healing process, afterwards gradually are reduced throughout the healing process. The analyses were carried out using the commercial package CATIA P3 V5R11. This allowed to accomplishes three-dimensional model more similar to the geometrical architecture of the long bone as well as of the external fixator. However, the accuracy of the results depends not only on the quality of the model geometry but also on the material properties assigned to the model components as well as on the accuracy in the simulation of the finite element model and the optimized mesh generation.

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Biomechanical analysis of human pelvis under muscolo-skeletal load using 3D finite element method

Majumder S., Roychowdhury A., Pal S.

International Journal of Applied Mechanics and Engineering

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2005

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Vol. 10, no 4

647-665

EN

During walking, the human pelvis is Ioaded by hip contact force and 22 muscle forces. Due to its complex geometry and structure, biomechanics of the human pelvis is complicated. A three-dimensionaI finite element model of the fulI pelvis was developed and the stress and deformation pattern was mapped, considering musculoskeletal loading, during 8 phases of a normal walking cycIe. The cortical and trabecular bones were modeled with shell-solid elements. The full model consisted of 71 674 tetrahedral and 17 264 shell elements (four-noded), through 16429 nodes. An algorithm was aIso developed to calculate the components and direction of 22 muscle forces, considering the origin, insertion points and change of femur position, relative to the pelvis during walking. Stress contour maps revealed that the zones and magnitudes of maximum von-Mises stresses (28 to 38 MPa for the cortical bone and 1.3 to 1.7 MPa for the trabecular bone) varied from phase to phase during walking. AIso the average phase wise variations for the resultant displacement were 0.1 to 0.5 mm. These results may be used approximately for a cIinical comparison between the normal pelvis and the effectiveness of different pelvic fracture fixation modalities.