Artikel
Elimination of parasitic motions enables application of defined mechanical conditions to study the mechanobiology of bone healing
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Autoren
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Pelin Tufekci
- Institute of Health and Biomedical Innovation, Queensland University of Technology, Kelvin Grove Qld, Australia
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Mirjam Neumann
- Universitätsklinikum Freiburg, Klinik für Orthopädie und Unfallchirurgie, Freiburg, Germany
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Siamak Saifzadeh
- Medical Engineering Research Facility, Queensland University of Technology, Chermside Qld, Australia
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Jan Henkel
- Institute of Health and Biomedical Innovation, Queensland University of Technology, Kelvin Grove Qld, Australia
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Roland Steck
- Medical Engineering Research Facility, Queensland University of Technology, Chermside Qld, Australia
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Michael Schütz
- Princess Alexandra Hospital, Trauma & Orthopaedic Services, Queensland University of Technology, Brisbane, Australia
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Devakar Epari
- Institute of Health and Biomedical Innovation, Queensland University of Technology, Kelvin Grove Qld, Australia
| Veröffentlicht: | 5. Oktober 2015 |
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Gliederung
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Objectives: Fracture healing requires mechanical stability and adequate blood supply. Although the influence of the mechanical environment on the healing outcome is well documented, the influence on the biological processes during healing is less clear. The inability to eliminate with interfragmentary motions arising from functional activity in experimental models has clouded the interpretation of bone healing studies. A newly developed bone-healing model featuring a novel defect configuration allows elimination of movements arising from functional activity and application of defined mechanical conditions an in vivo monitoring of healing through active fixation.
Methods: The novel bone-healing model consists of two osteotomies creating an experimental fracture (3 mm) and a critical size defect (3 cm). The main proximal and distal fragments are stabilised by a conventional external fixator. A mobile segment between the experimental and critical sized defects is held by a motorised custom fixator. Pilot investigation was undertaken to establish performance of the model. Six merino sheep were divided into two groups. In the first, negative control, the experimental fracture was not subjected to any motion. In the second, 500 cycles of interfragmentary movement (1 mm) were applied daily for 3 weeks. After 9 weeks the animals were sacrificed and the healed tibiae were explanted for microCT scans and biomechanical testing.
Results and Conclusion: The animals tolerated the procedure. Analysis of micro CT scans showed expected minimal callus formation after nine weeks in the negative group due to an understimulation in the fracture zone. In the positive group with permitted physiological loading in the fracture gap model signs of callus formation were evident after nine weeks. Biomechanical testing demonstrated a superior healing in the loaded group (torsional stiffness 6.2 versus 0.8 Nm/deg).
The presented model has the capability to eliminate functional loading within an experimental fracture and application of a defined mechanical environment. The model provides an opportunity to apply defined loads to a healing fracture during different phases of healing to understand the mechano regulation of callus formation through the use of active fixation.
