Early, controlled tension improves the material properties of healing human Achilles tendons after rupture : a randomized trial

• Background: Weight-bearing in a fixed brace after acute Achilles tendon rupture does not necessarily lead to mechanical tension in the tendon. Early motion has a positive effect on the clinical outcome, but it is not clear if this is due to effects on tendon strength or to unspecific effects. The aim of this study was to examine if tensional loading leads to improvement of the mechanical properties of the healing, human Achilles tendon.Hypothesis: The elastic modulus of the tendon callus is increased by early tensional loading.Study Design: Randomized controlled trial; level of evidence: 2.Methods: Thirty-five patients with an acute Achilles tendon rupture were recruited consecutively. They were operated with a single suture, and received metal markers in the distal and proximal part of the tendon. After surgery, patients were randomized to either cast immobilization for 7 weeks or tensional loading. The latter group wore a cast for 2 weeks, and then a removable foam walker boot for 5 weeks. They were instructed to remove the boot twice daily and push a special training pedal to produce a predetermined, gradually increasing tensional load on the healing tendon. At 7, 19 and 52 weeks postoperatively, patients were investigated with Roentgen Stereophotogrammetric Analysis (RSA) under different loading conditions, and computed tomography (CT). The collected data allowed calculation of modulus of elasticity. At 52 weeks, we also examined clinical outcome, using the Achilles tendon Total Rupture Score (ATRS) and a heel-raise index.Results: The elastic modulus at 19 and 52 weeks was higher in the tensional loading group. There was no significant difference in ATRS or heel-raise index at 52 weeks. As in previous studies, there was a significant correlation between the modulus at 7 weeks and the heel-raise index at 52 weeks. There was moderate tendon elongation.Conclusion: Early tensional loading improves the mechanical properties of the healing Achilles tendon.

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MEDICIN

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