Introduction: As Achilles tendon ruptures are healing slowly, many attempts are made trying to improve the healing after injury. Rat experiments have shown that injection of platelets improves tendon healing. A clinical study on patients has also shown a better outcome after injecting platelets into the rupture area. Therefore we wanted to verify the effect of platelets by measuring the mechanical properties of the healing Achilles tendon in a randomised study.

Methods: We included 30 patients with an Achilles tendon rupture. All patients left one blood unit at the hospital blood bank. From this unit of blood approximately 20 ml of platelet concentrate were gained. All patients were operated the next day using an open technique. Just before wound closure, patients were randomised into 2 groups, with one group receiving 10 ml of their own platelet concentrate. In order to measure mechanical properties, we implanted Tantalum beads on either side of the rupture giving us the chance of exactly determining the distance between the beads using RSA and thereby measuring the stiffness of the tendon. CT was used to measure the area of the rupture site. Both groups were postoperatively treated with a cast for 7 weeks. 4 weeks with the ankle in the equines position and 3 weeks in the neutral position. After cast removal, the patients started rehabilitation. The patients in both groups received exactly the same treatment after surgery. Patients were examined with CT and RSA to determine area, stiffness and modulus of elasticity. Measurements were performed at 7 weeks after operation and again at 19 weeks.

Results: 16 patients were randomised to platelet concentrate. One patient got a deep infection and another patient suffered from a rerupture of the Achilles tendon. Both patients had to be excluded after the first CT- and RSA-examination. Both patients had received platelet concentrate. There was no significant difference between both groups after 7 and 19 weeks in area, stiffness or modulus of elasticity.

Discussion: Our results indicate that platelet concentrate does not improve the mechanical properties of the healing Achilles tendon, at least when patients are treated with a cast for 7 weeks.

Studies have shown that the effect of platelet concentrate is depending on a certain loading of the Achilles tendon during the early phase of healing. Unfortunately we do not know much about loading of the Achilles tendon while having the leg in a cast, but the rigid fixation might lead to certain unloading. Further studies are needed to learn more about loading of the Achilles tendon in a cast.

Furthermore we have also done a clinical examination of all patients, as we know from a previous study that there is a correlation between early mechanical properties and clinical outcome but we have not evaluated the clinical results of this study yet.