THE ROLE OF EXTERNAL NONRIGID ANKLE BRACING IN LIMITING ANKLE INVERSION

The purpose of this study was to measure the effectiveness of the nonr igid subtalar stabilizer (STS) ankle brace under conditions similar to an unexpected fall that could lead to a lateral ligament injury. The calcaneal inversion angles, times, and ground reaction forces were mea sured when the subject's right foot, bearing body weight, was suddenly inverted to a side slope of 22 degrees. Thirty subjects, 15 women and 15 men, participated in the study. The overall inversion drop was div ided into two phases, free fall and loading. Based on the data of this study it is suggested that the major function of a brace is to restri ct the amount of foot inversion during the fall before actual landing occurs rather than functioning as a force bypass for the lateral ligam ents during loading after foot contact. The results showed that the br ace significantly (p < 0.05) reduced the maximum calcaneal inversion a ngle from 27.4 +/- 6.1 to 18.3 +/- 6.0 degrees for the overall drop, s ignificantly lengthened the inversion time from 0.14 +/- 0.04 to 0.18 +/- 0.04s for the overall drop, and significantly reduced the calcanea l peak inversion velocity from 324.6 +/- 111.9 to 165.2 +/- 66.5 degre es/s during loading, and from 278.7 +/- 120.0 to 183.0 +/- 108.7 degre es/s for the overall drop. Following exercise, which incorporated late ral movements and sprinting, the STS ankle brace continued to provide significant (p < 0.05) reduction in the calcaneal inversion angle and velocity, although some of its effectiveness was reduced. The results of this study suggest that the nonrigid STS ankle brace provides suppo rt that could reduced injuries by significantly restricting the degree of calcaneal inversion range of motion during an unexpected fall; sig nificantly lengthening the time of inversion, thereby decreasing the r ate at which the calcaneus inverts during a sudden inversion drop; and maintaining this support following sprinting and lateral movement exe rcises.