Abstract | INTRODUCTION: The biomechanics of early tendon healing is important for designing post-injury training, but this has not been described in an animal model, similar to humans in size. We measured elastic and viscoelastic properties of a tendon regenerate in sheep, in a study designed to see the effects of exogenously applying the growth and differentiation factor CDMP-2. This is the first description of early tendon healing in sheep Achilles tendons. MATERIALS AND METHODS: Twenty female sheep underwent Achilles tendon transection without suturing or immobilization. Two hours after the operation, 100 mug of CDMP-2 or placebo was injected into the hematoma. The sheep were slaughtered after 3 weeks, and tendon regenerates tested for viscoelastic properties by cyclical loading, before a destructive tensile test. Thereafter, all specimens were examined by high resolution computerized tomography (CT), and histology. RESULTS: The tendon regenerate formed a sleeve, around the tendon stumps. Failure occurred between the regenerate sleeve and the tendon stumps. There was an unexpectedly large variation in force at failure. In the CDMP-2 group, force correlated with regenerate transverse area, but not in the controls. Thus, the variation in maximum stress was smaller in the CDMP-2 group (P = 0.009). Although the force at failure was only a tenth of normal, the capacity to store elastic energy was already near normal (hysteresis 16%). The mean transverse area, force at failure and stiffness were all about 30% larger in the CDMP-2 group, but this was not significant. There were no signs of bone or cartilage formation on CT or histology. CONCLUSIONS: Results are compatible with a positive effect of CDMP-2, but the power was too low to demonstrate any such effect. Considering that spontaneous ruptures in humans are likely to have a more variable geometry than in this model, humans can also be expected to vary a lot in early mechanical characteristics. This emphasizes the importance of individualized rehabilitation programs. The low hysteresis suggests that the energy storing capacity is rather easy for the tissues to develop; possibly it is harder to create appropriate energy dissipation, in order to avoid re- rupture.
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Authors | Olena Virchenko, Anna Fahlgren, Mats Rundgren, Per Aspenberg |
Journal | Archives of orthopaedic and trauma surgery
(Arch Orthop Trauma Surg)
Vol. 128
Issue 9
Pg. 1001-6
(Sep 2008)
ISSN: 0936-8051 [Print] Germany |
PMID | 18600332
(Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
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Chemical References |
- Bone Morphogenetic Proteins
- cartilage-derived-morphogenetic protein-2
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Topics |
- Achilles Tendon
(injuries, physiology)
- Animals
- Bone Morphogenetic Proteins
(pharmacology)
- Injections
- Models, Animal
- Random Allocation
- Regeneration
(physiology)
- Sheep
- Tensile Strength
(physiology)
- Weight-Bearing
(physiology)
- Wound Healing
(physiology)
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