gms | German Medical Science

Objectives: Lateral ankle sprains affect nearly a half of all ankle sprains and have a reported recurrence rate of more than 70%. In lateral ankle sprains and accompanying lesions of the lateral ligaments orthoses are used for the functional treatment by protecting the ligaments from excessive stresses and reinjury since a previous injury history may be one of the most important risk factors for an ankle sprain. Despite their common application in clinical routine, there is very little biomechanical evidence on the efficacy of various orthoses to restrict inversion and internal rotation and on their stabilizing effect in the ankle joint with existing lateral instability. Therefore the aim of the present study was to biomechanically evaluate and quantify the isolated stabilizing abilities of commonly prescribed semi-rigid ankle orthoses in a simulated reoccurring inversion trauma.

Methods: Twelve anatomic lower leg specimens were tested in plantar flexion and hindfoot inversion in a simulated inversion trauma in a quasi-static and dynamic (at 50°/s) mode. Tests were performed on intact specimens, same specimens with the ruptured anterior talofibular ligament (ATFL) (simulating an existing ankle sprain injury), followed by stabilization with 5 different semi-rigid orthoses (AirGo Ankle Brace (DJO, LLC; Vista, CA, USA), Air Stirrup Ankle Brace (DJO, LLC; Vista, CA, USA), Dyna Ankle 50S1 (Otto Bock HealthCare GmbH; Duderstadt, Germany), MalleoLoc (Bauerfeind AG; Zeulenroda-Triebes, Germany), and Push Aequi (Push, Maastricht-Airport; Netherlands)). The stabilizing effect was quantified by the reinforcement of internal rotation moment between tibia and calcaneus compared to the injured and unprotected state. One-tailed t-test was performed to analyse for statistically significant differences in the internal rotation moment.

Results and conclusion: Only two orthoses (AirGo and Air Stirrup) reinforced the ankle joint during inversion compared to the uninjured and unprotected state in (Figure 1a [Fig. 1]) quasi-static and (Figure 1b [Fig. 1]) dynamic modes. Both orthoses show a similar design of stabilizing elements and allow sufficient adhesion on the skin. Aequi showed internal rotation moment in the magnitude of intact ankle joints. Dyna Ankle 50S1 and MalleoLoc provided less than 2.5% resistance to applied internal rotation compared to ankle joint with ruptured ATFL. Their design should be reconsidered. Testing in quasi-static and dynamic mode delivered valid and comparable results.

In conclusion ankle orthoses varied significantly in their ability to stabilize the ankle joint during an inversion trauma. Presented objective data on passive stabilization may assist clinicians when prescribing adequate orthoses.