Article
Fixation bending stiffness affects metaphyseal bone fracture healing in mice
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Authors
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Roland Steck
- Institute of Health and Biomedical Innovation, Queensland University of Technology, Orthopaedics and Trauma Qld, Brisbane, Australia
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Lidia Koval
- Institute of Health and Biomedical Innovation, Queensland University of Technology, Orthopaedics and Trauma Qld, Brisbane, Australia
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Anneliese Dickson
- Institute of Health and Biomedical Innovation, Queensland University of Technology, Orthopaedics and Trauma Qld, Brisbane, Australia
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Romano Matthys
- RISystem AG, Davos Platz, Switzerland
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Laura Gregory
- Institute of Health and Biomedical Innovation, Queensland University of Technology, Orthopaedics and Trauma Qld, Brisbane, Australia
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Geertje Govaert
- Trauma Service, Princess Alexandra Hospital, Woolloongabba, Australia
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Michael Schütz
- Queensland University of Technology, Princess Alexandra Hospital, Trauma Service, Brisbane, Australia
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Tina Histing
- Universitätsklinikum des Saarlandes, Klinik für Unfall-, Hand- und Wiederherstellungschirurgie, Homburg, Germany
| Published: | October 23, 2013 |
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Outline
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Objective: Metaphyseal fractures of the distal radius or proximal femur are among the most common fractures observed clinically, and many of these fractures are associated with osteoporosis and an increased incidence of complications. Clinical treatment approaches for these fractures remain controversial, also because metaphyseal fracture healing has received little attention in research up until now, and there have been few suitable experimental models to study metaphyseal bone healing in animals. In particular, it is not known to what extent the mechanical environment, critical for successful diaphyseal fracture healing, plays a role in metaphyseal fracture healing. Recently, a new murine internal fixation plate has been developed to stabilise metaphyseal femur fractures under highly standardised conditions. Goal of the current study was to adapt the existing plate design to reduce its bending stiffness, in order to study the influence of the fixation bending stiffness on metaphyseal fracture healing in mice.
Methods: Adapting the single body design of the existing, high stiffness fixation plate, two new plates were developed with a decreased bending stiffness of approximately 65% and 45% of the original implant (100%). For the in vivo experiments, 54 female CD1 mice were randomly divided into three groups, and a metaphyseal osteotomy was stabilised with one of the three implants with varying bending stiffness. The mice were sacrificed after 14 or 28 days healing time (9 animals per group and time point). Fracture healing was assessed by determining fracture callus volume and mineral density by microCT and by comparing the bending stiffness of the healing bones with that of the contralateral, intact control bones.
Results and conclusion: 14 days after osteotomy and fixation with plates of different stiffnesses, no significant differences in bending stiffness (range of 10-28% of that that of the contralateral control limbs), callus volume and mineralisation of the healing bones could be detected. After 28 days, the bones stabilised with 65% stiffness plates had a higher bending stiffness (70% of control) than those stabilised with 100% plates (40% of control, ANOVA, p<0.05) and marginally higher than those stabilised with 45% plates (47% of control). Since global parameters characterising callus volume and mineralisation were similar among all groups and therefore not able to explain these differences of mechanical competency, a detailed characterisation of callus morphology and mineralisation patterns is currently under way.
Our results indicate that fixation stiffness also affects the healing of metaphyseal fractures. The new implants therefore represent an important new research tool to study the molecular and genetic aspects of metaphyseal fracture healing in mice. In particular, the new implants will enable future studies for evaluating new treatment modalities under standardized conditions to improve metaphyseal bone healing in challenging situations, such as in osteoporotic bone.
