A 3D computational simulation of fracture callus formation: influence of the stiffness of the external fixator.

The stiffness of the external fixation highly influences the fracture healing pattern. In this work we study this aspect by means of a finite element model of a simple transverse mid-diaphyseal fracture of an ovine metatarsus fixed with a bilateral external fixator. In order to simulate the regenerative process, a previously developed mechanobiological model of bone fracture healing was implemented in three dimensions. This model is able to simulate tissue differentiation, bone regeneration, and callus growth. A physiological load of 500 N was applied and three different stiffnesses of the external fixator were simulated (2300, 1725, and 1150 N/mm). The interfragmentary strain and load sharing mechanism between bone and the external fixator were compared to those recorded in previous experimental works. The effects of the stiffness on the callus shape and tissue distributions in the fracture site were also analyzed. We predicted that a lower stiffness of the fixator delays fracture healing and causes a larger callus, in correspondence to well-documented clinical observations.

[1]  Rik Huiskes,et al.  Comparison of biophysical stimuli for mechano-regulation of tissue differentiation during fracture healing. , 2006, Journal of biomechanics.

[2]  M J Gómez-Benito,et al.  Influence of fracture gap size on the pattern of long bone healing: a computational study. , 2005, Journal of theoretical biology.

[3]  T A Einhorn,et al.  The cell and molecular biology of fracture healing. , 1998, Clinical orthopaedics and related research.

[4]  D Kaspar,et al.  Effects of Mechanical Factors on the Fracture Healing Process , 1998, Clinical orthopaedics and related research.

[5]  W. Hayes,et al.  Failure of growth hormone to alter the biomechanics of fracture-healing in a rabbit model. , 1992, The Journal of bone and joint surgery. American volume.

[6]  T. Gardner,et al.  The biomechanical environment of a bone fracture and its influence upon the morphology of healing. , 2003, Medical engineering & physics.

[7]  G. Beaupré,et al.  An approach for time‐dependent bone modeling and remodeling—application: A preliminary remodeling simulation , 1990, Journal of orthopaedic research : official publication of the Orthopaedic Research Society.

[8]  E. Mucke.  Shapes and implementations in three-dimensional geometry , 1993 .

[9]  M. Heller,et al.  The initial phase of fracture healing is specifically sensitive to mechanical conditions , 2003, Journal of orthopaedic research : official publication of the Orthopaedic Research Society.

[10]  Lang Yang,et al.  Stiffness characteristics and inter-fragmentary displacements with different hybrid external fixators. , 2003, Clinical biomechanics.

[11]  L. Claes,et al.  Influence of size and stability of the osteotomy gap on the success of fracture healing , 1997, Journal of orthopaedic research : official publication of the Orthopaedic Research Society.

[12]  A. Goodship,et al.  A technique for investigating the response of bone to changes in its mechanical environment [proceedings]. , 1978, The Journal of physiology.

[13]  T N Gardner,et al.  The influence of mechanical stimulus on the pattern of tissue differentiation in a long bone fracture--an FEM study. , 2000, Journal of biomechanics.

[14]  Ellen M. Leiferman,et al.  Differential growth by growth plates as a function of multiple parameters of chondrocytic kinetics , 1996, Journal of orthopaedic research : official publication of the Orthopaedic Research Society.

[15]  A. Goodship.  Mechanical stimulus to bone. , 1992, Annals of the rheumatic diseases.

[16]  C Ament,et al.  A fuzzy logic model of fracture healing. , 2000, Journal of biomechanics.

[17]  J Sánchez-Lacuesta,et al.  Load transmission through the callus site with external fixation systems: theoretical and experimental analysis. , 1994, Journal of biomechanics.

[18]  P J Prendergast,et al.  Biophysical stimuli on cells during tissue differentiation at implant interfaces , 1997 .

[19]  Lutz Claes,et al.  Shear movement at the fracture site delays healing in a diaphyseal fracture model , 2003, Journal of orthopaedic research : official publication of the Orthopaedic Research Society.

[20]  N. Sasaki,et al.  Elongation mechanism of collagen fibrils and force-strain relations of tendon at each level of structural hierarchy. , 1996, Journal of biomechanics.

[21]  B. Mckibbin,et al.  The biology of fracture healing in long bones. , 1978, The Journal of bone and joint surgery. British volume.

[22]  E. Chao,et al.  Comparison of osteotomy healing under external fixation devices with different stiffness characteristics. , 1984, The Journal of bone and joint surgery. American volume.

[23]  P. Dawson,et al.  A microstructural model for the anisotropic drained stiffness of articular cartilage. , 1990, Journal of biomechanical engineering.

[24]  J Kenwright,et al.  The role of fixator frame stiffness in the control of fracture healing. An experimental study. , 1993, Journal of biomechanics.

[25]  E. Chao,et al.  The effect of rigidity on fracture healing in external fixation. , 1989, Clinical orthopaedics and related research.

[26]  P J Prendergast,et al.  Mechano-regulation of stem cell differentiation and tissue regeneration in osteochondral defects. , 2005, Journal of biomechanics.

[27]  D E Ashhurst,et al.  The influence of mechanical conditions on the healing of experimental fractures in the rabbit: a microscopical study. , 1986, Philosophical transactions of the Royal Society of London. Series B, Biological sciences.

[28]  J L Lewis,et al.  A composites theory predicts the dependence of stiffness of cartilage culture tissues on collagen volume fraction. , 1999, Journal of biomechanics.

[29]  Augustus A. White,et al.  Monitoring the healing of a tibial osteotomy in the rabbit treated with external fixation , 1985, Journal of orthopaedic research : official publication of the Orthopaedic Research Society.

[30]  L Claes,et al.  Analysis of inter-fragmentary movement as a function of musculoskeletal loading conditions in sheep. , 1997, Journal of biomechanics.

[31]  V. A. Gibson,et al.  Model of flexural fatigue damage accumulation for cortical bone , 1997, Journal of orthopaedic research : official publication of the Orthopaedic Research Society.

[32]  Marjolein C H van der Meulen,et al.  Beneficial effects of moderate, early loading and adverse effects of delayed or excessive loading on bone healing. , 2003, Journal of biomechanics.

[33]  L. Claes,et al.  Magnitudes of local stress and strain along bony surfaces predict the course and type of fracture healing. , 1998, Journal of biomechanics.

[34]  P. Prendergast,et al.  A mechano-regulation model for tissue differentiation during fracture healing: analysis of gap size and loading. , 2002, Journal of biomechanics.

[35]  G S Beaupré,et al.  An approach for time‐dependent bone modeling and remodeling—theoretical development , 1990, Journal of orthopaedic research : official publication of the Orthopaedic Research Society.

[36]  L. Nokes,et al.  The use of strain gauges to measurebone fracture healing—a review , 1994 .

[37]  D. Danielson,et al.  Human skin as an elastic membrane. , 1973, Journal of biomechanics.

[38]  J Kenwright,et al.  Controlled mechanical stimulation in the treatment of tibial fractures. , 1989, Clinical orthopaedics and related research.

[39]  Dennis R. Carter,et al.  Mechanobiology of Skeletal Regeneration , 1998, Clinical orthopaedics and related research.

[40]  P J Prendergast,et al.  Three-dimensional Simulation of Fracture Repair in the Human Tibia , 2002, Computer methods in biomechanics and biomedical engineering.

[41]  D. E. Ashhurst,et al.  The Expression of the Fibrillar Collagen Genes During Fracture Healing: Heterogeneity of the Matrices and Differentiation of the Osteoprogenitor Cells , 1999, The Histochemical Journal.

[42]  Lutz Claes,et al.  Local tissue properties in bone healing: Influence of size and stability of the osteotomy gap , 1998, Journal of orthopaedic research : official publication of the Orthopaedic Research Society.