Effect of Knee Position on Gap Size Following Acute Achilles Rupture

Background: Acute traumatic rupture of the tendoachilles is a common problem. Following a recent Cochrane review, operative treatment has been shown to have a lower re-rupture rate compared with conservative treatment, but is associated with a slightly higher rate of other complications. Debate concerning the method and duration of conservative treatment remains. We aimed to assess the effect of knee position on the gap in acute tendoachilles ruptures. Materials and Methods: Patients with a history and examination consistent with an acute rupture were collected prospectively. They were investigated by the same musculoskeletal consultant radiologist using ultrasonography. Tendon gap was measured with the foot in neutral and full tolerable equinus with the knee both flexed to 90 degrees and fully extended. A pilot study of 10 patients was used to provide data for a power calculation. Following this a total of 25 consecutive patients were recruited for inclusion. A paired Student t-test was used to compare mean differences between the knee flexed/ankle plantarflexed and knee extended/ankle plantarflexed positions on the gap at the rupture site. Results: A diagnosis of acute tendoachilles rupture was confirmed in all patients and tendon gap was measured with the knee flexed and extended with the ankle either neutral or plantarflexed. This confirmed there was no significant difference in the tendon gap with the knee flexed or extended provided the foot was in full equinus (p > 0.05). Conclusion: This study showed that knee position had no significant effect on the tendon gap at the rupture site. This study could have considerable implications on the rationale behind conservative treatment and splinting of acute tendoachilles ruptures with no apparent role for knee flexed immobilization.