Restriction of motion during simulated inversion on a tilting platform in ten different ankle braces

Eils E, Demming C, Kollmeiser G, Thorwesten L, Völker K, Rosenbaum D

Abstract in digital collection (conference)

Abstract

INTRODUCTION Ankle bracing is a cornrnon practice arnong individuals with chronic ankle instability to prevent recurrent injuries. In sports, the rnain goal of braces is to ensure stability without influencing performance. A variety of products that consist of rigid or flexible rnaterials is cornrnercially available and rnay lead to confusion of consurners. A cornparative evaluation of the stabilizing effect of several ankle braces should be helpful for the selection of the rnost appropriate brace. Therefore, the airn of the present study was to cornpare the stabilizing eff ect of ten different ankle braces under sudden inversion conditions on a tilting platform. METHODS 25 subjects with chronic ankle instability participated in the project. Their rnean age, rnass and height was 22.7±2. 7 years, 70.6±12.4 kg and 177±8.6 cm, respectively. A trap door with a tilting angle of 30° in the frontal plane was used to sirnulate lateral ankle sprains. Surface EMG signals of the peroneus longus were recorded to determine reaction tirnes due to sudden inversion and a custornized goniorneter was used to rneasure the hindfoot inversion angle inside the shoe (Fig. 1 ). Ten different commercially available ankle braces and the condition without brace (native) were used in all subjects ( one rigid reference rnodel (3-Caligarned), five serni rigid (1-Aircast, 2-Malleoloc, 5-Air Gel, 7-Air Brace, 9-Ligacast Anatomie) and 4 soft (4-Kalassy, 6-Kalassy-S, 8-Fibulo-Tape, 10-Dynastab). The testing order of the ten braces was randornized and one shoe rnodel was used for all subjects. Ten repeated trials per brace were recorded and for each trial muscle reaction tirnes and inversion angles were derived and averaged. Inversion was subdivided into two phases: end of tilting phase (free fall) and rnaxirnurn inversion phase (weight bearing) (Fig. 1, right). A repeated rneasures Anova with the alpha-level set to 5% and the Scheffe test for post-hoc cornparisons were used for statistical analysis. RESULTS The inversion angle for native, free fall condition was on average 28°±5°. All braces reduced this angle significantly and values between 12° (#1) and 23° (#8) were reached. Maximum inversion angles of 39°±6° were found for native condition and all braces led to a significant restriction of motion to 20°-33°. Focussing on the categories of braces, significant differences could be found for braces that consist of separate plastic parts on either side of the ankle (# 1, 5, 7, 9) and all other models. Differences between inversion angles at the end of free fall and bearing bodyweight (maximum inversion angle) are in the range of 7° to 11 °. Peroneal reaction times were on average 51.2± 0.9 ms and no significant differences between conditions could be found (Table 1 ). DISCUSSION AND CONCLUSION In general, semi-rigid braces that contain rigid parts on the medial and lateral ankle (#1,5,7,9) appear to restrict inversion movements more effectively than all other braces. Although all ankle braces significantly reduce sudden inversion, the stabilizing effect of some soft braces may not be sufficient in terms of injury prevention. When focussing on free fall and maximum angles, only differences of 4 ° could be found between all braces. This finding suggests, that the major function of braces is the restriction of motion in the free fall phase and does not act like a force bypass in the weight bearing situation [1, 2]. This seems to be independent of the category of the braces (semi rigid or soft). With respect to the peroneal reaction times, no proprioceptive effect of braces could be measured. For prophylactic use in sports it was shown that the tested braces had no significant influence on performance in a short agility course [3]. From that point of view, some serni rigid models (#1, 5, 7, 9) might be recommended as an optimal solution for preventing injuries in sports. On the other hand, it has to be considered, that the special design makes it difficult to wear regular shoes with these braces. In addition, some sports like soccer restrict the use of these models because of using sorne additional equipment like shin guards.

Details zur Publikation

Publisher: Hennig E, Stacoff A
Book title: Proceedings of the 5th Symposium on Footwear Biomechanics
Release year: 2001
Publishing company: Schlieren, Switzerland : Dept. of Minerals, ETH Zurich
Language in which the publication is written: English
Event: Zuerich