Article
Minimally invasive plate osteosynthesis: advanced early fracture healing in a sheep trauma model
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Authors
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M. E. Wullschleger
- Queensland University of Technology, Institute of Health and Biomedical Innovation, Brisbane, Australia
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R. Steck
- Queensland University of Technology, Institute of Health and Biomedical Innovation, Brisbane, Australia
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J. Webster
- Queensland University of Technology, Institute of Health and Biomedical Innovation, Brisbane, Australia
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K. Wilson
- The Prince Charles Hospital, Biological Research Facility, Brisbane, Australia
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K. Ito
- Eindhoven University of Technology, Orthopaedic Biomechanics Section, Eindhoven, Netherlands
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M. A. Schuetz
- Queensland University of Technology, Institute of Health and Biomedical Innovation, Brisbane, Australia
| Published: | October 15, 2009 |
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Outline
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Problem: Minimally invasive plate osteosynthesis (MIPO) has become a clinically accepted method with good results, when compared to the conventional open surgical approach (ORIF). However, while MIPO offers some advantages over ORIF, it also has some significant drawbacks, such as a more demanding surgical technique with the risk for malreduction/malalignment, and increased radiation exposure. No experimental study to date showed a difference between the healing outcomes in fractures treated with the two surgical approaches. Therefore, we have developed a novel, standardised severe trauma model, applied to the distal femur of sheep, and used it to examine the effect of the two surgical approaches on soft tissue and fracture healing.
Methods: 24 sheep (Merino wethers, mean age 5.6 years, mean weight 39.1 kg) were subjected to a severe soft tissue damage (Tscherne III), administered by blunt impact from a pendulum device, and a multi-fragmentary distal femur fracture (AO C-type) created in a minimally invasive fashion by a combination of drill holes and partial osteotomies. The fracture was initially stabilised with an external fixator. After 5 days of soft tissue recovery, internal fixation with a 4.5mm narrow LCP was applied, randomised either by MIPO or ORIF. Within the first 14 days, the soft tissue damage was monitored by daily serum blood tests for Creatin Kinase (CK). The sheep were sacrificed in two groups after 4 and 8 weeks, and CT scans and mechanical testing performed. The results were analysed statistically with ANOVA test.
Results and conclusion: Soft tissue monitoring showed significantly higher CK values in the ORIF group (1028.9±827.0 U/l (SD), p<0.05) compared to MIPO (286.4±259.7 U/l).
After 4 weeks, the torsional stiffness was significantly higher in the MIPO group (30.1±10.6% (SD) of the intact contra-lateral femur, p=0.018) compared to the ORIF group (9.8±12.4%). The torsional strength also showed increased values for the MIPO technique (p=0.11). The measured mineralised callus volumes were higher in the ORIF group (19141±8511 mm3) than those of the MIPO group (15596±6194 mm3), however, statistically not significant.
After 8 weeks, the trends observed at 4 weeks continued, but the differences in torsional stiffness were not statistically significant anymore.
This study shows that the surgical approach does influence the healing process of fractures. Fractures treated with the MIPO technique had superior mechanical properties during the earlier stages of the healing process, despite the smaller fracture callus. In contrast, the open surgical approach creates more damage, (higher CK levels), and leads to the formation of a bigger callus, whereas this size difference does not translate into better mechanical properties.
Clinically, these results indicate that despite the challenges involved with the MIPO technique, the outcome is at least as good as with the proven ORIF technique, with potential advantages during the early stages.
