An experimental study of the mechanical properties of the Achilles tendon in rabbits during its recovery after injury




Achilles tendon, trauma, modulus of elasticity, ultimate strength


Background. The problem of treating patients with tendon injuries remains unresolved. Unsatisfactory results after surgical treatment, according to different authors, range from 15 to 62 %. The functional outcome after surgical repair of damaged tendons is difficult to predict because of the high risk of scar block formation, which prevents them from sliding freely. Adhesions compromise the extensibility of the tendons, which in turn affects their strength. The purpose was to experimentally investigate the strength properties of the Achilles tendons after their surgical restoration with the further use of various medications. Materials and methods. The mechanical properties of the Achilles tendons of rabbits were investigated, on which a model of their partial damage was created by crossing by 1/2 the diameter. The injured tendon was sutured with a tendon suture. Within the experiment, 5 groups of preparations of the Achilles tendons of rabbits with a heel bone were studied, 3 preparations in each group. Group 1 was a control one. After performing the tendon suture, the wound was sutured. The rabbits of group 2 were administered Noltrex around the tendon suture. Group 3 included the animals who were injected with a preparation of hyaluronic acid. Group 4 consisted of the animals who were injected with lidase. Group 5 included the animals with the normal values, preparations of non-operated Achilles tendons of intact animals. All animals were withdrawn from the experiment on day 60. According to the test results, the value of the elastic modulus and the ultimate strength of the preparation was calculated. Results. The greatest elongation under a tensile load of 30 N was achieved on preparations of unoperated Achilles tendons of rabbits — 2.96 ± 0.22 mm. The smallest elongation was obtained for the preparations of the control group — 0.83 ± 0.37 mm. The rest of the drug groups showed intermediate values. The Achilles tendon preparations of rabbits from the control group (0.216 ± 0.123 MPa) have the highest value of the elastic modulus. The smallest value of the modulus of elasticity was found in the study of non-injured preparations of the Achilles tendon (0.051 ± 0.004 MPa). The drugs of the control group had the greatest strength (the value of the maximum permissible load was 81.81 ± 0.34 N). The least strength was demonstrated by preparations of non-traumatized Achilles tendons of rabbits (the value of the maximum permissible load was 69.72 ± 0.18 N). Conclusions. Within the recovery of the Achilles tendon in rabbits after injury, an increase in the values of indicators characterizing the strength properties of tissues is observed — elastic modulus, maximum permissible load, and ultimate strength. The values of indicators characterizing the plastic properties of tissues decrease, which can be one of the reasons for the development of post-traumatic contractures. The best indicators in terms of tissue plasticity were observed in the group of preparations of the Achilles tendon of rabbits treated with hyaluronic acid. The worst ones were registered in the control group.


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