Effects of Direct Functional Mobilization After Achilles Tendon Rupture on Healing and Outcome

Patients with acute Achilles tendon rupture will be screened for eligibility at the Karolinska University Hospital and Södersjukhuset, Stockholm.

One hundred-fifty patients will be included and enrolled and assigned to the interventions either by a third party nurse or by a research nurse. Randomisation will be performed with use of computer-generated random numbers in permuted blocks of four, through an independent software specialist, and consecutively numbered, sealed, opaque envelopes opened after surgery and prior to treatment.

The patients will be randomized to undergo either treatment as usual using plaster cast treatment alone or direct post-operative functional mobilization with a weight-bearing orthosis with adjustable range of motion of the ankle.

The power calculation was based upon data from a recent study reporting a 50% rate of CDU-verified DVT after ATR surgery (Domeij-Arverud et a. 2015). We estimated early functional mobilization (EFM) to confer a 50% risk reduction. Sixty-three patients in each group were required to detect a difference of 25% in the incidence of DVT (two-sided type-I error rate = 5%; power = 80%). We decided to include 150 patients to counteract drop-outs. On recommendations from the ethical committee, a ratio of 2:1 was chosen, since our hypothesis was that the EFM group would perform better.

The endpoint of the first part of the study is tendon healing quantified at 2 weeks by microdialysis followed by quantification of markers for tendon repair. The sample size for the outcome in the microdialysis study was calculated on a difference of the glutamate metabolite of 12 µM between the two groups. For this power analysis, we used a glutamate standard difference of 15 µM resulting from a previous study. It was determined that a sample size of 25 patients per group would be necessary to detect the glutamate difference with 80% power when alpha was set equal to 5%. Anticipating that we would lose 10% of participants enrolled, we plan to enroll 27 patients in each group for microdialysis.