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Introduction

Injury to the ankle joint is common among the athletic population (Garrick, 1988), military personnel (Milgrom, 1991), and the working population (Grimm, 1999). The vast majority (85%) of injuries to the foot and ankle are ankle sprains (Garrick, 1977). Garrick (1988) reports that among injuries treated in a sports-medicine clinic over 6.5 years, twenty- five percent of the injuries occurred at the foot and ankle. Ankle sprain rates for basketball participation have been reported as ranging from 1.22 injuries/1,000 participations in Canadian collegiate players (Meeuwisse, 2003) to 3.85 injuries/1,000 participations in predominantly recreational games (McKay, 2001). Half of the recreational participants who incurred an ankle sprain injury missed a week or more of competition. Anderson et al. (2004) recently reported a rate of 4.5 injuries/1,000 match hours during matches between elite Norwegian and Icelandic soccer players. Ankle sprains also account for up to 41% of all volleyball injuries (Verhagen, 2004). Ankle injuries also account for between 30 to 60% of all parachuting injuries in military personnel (Amoroso, 1998).

The general population also experiences an appreciable number of ankle sprains. Grimm and Fallat (1999) retrospectively studied all foot and ankle injuries during a one year period at an occupational medicine clinic. These investigators reported that 6.4% of all injuries treated at the clinic were injuries to the foot and ankle, 40.8% of which were ankle sprains. The average cost of medical treatment for all types of ankle injury for this

Mechanisms of Injury

Common mechanisms of injury for ankle sprains during sporting events include quick cutting motions, landing from a jump (McKay, 2001), landing on an uneven surface, and colliding with an opponent (Anderson, 2004). Additional mechanisms include misstepping, stepping on an object, and inverting the ankle on uneven terrain while walking or jogging. The risk for future ankle sprain injury increases following an initial injury (Surve, 1994; Yeung, 1994). McKay (2001) reported basketball players with a history of ankle sprain are up to five times more likely to suffer an ankle sprain than individuals without previous injury.

Recommended use of an ankle brace is a common clinical intervention to prevent ankle sprains. The results of multiple studies indicate that using an ankle brace can reduce the incidence of ankle sprains in sporting activities such as football (Rovere, 1988), basketball (Sitler, 1994), and soccer (Tropp, 1985; Surve, 1994). Additionally, Amoroso et al. (1998) demonstrated a reduction in the incidence of ankle sprain injuries during Army paratrooper training when recruits wore an outside-the-boot brace.

The Future of Ankle Brace Research

Several recently published reviews have called for additional research studying the use of ankle bracing to prevent ankle sprains. Wilkerson (2002) has encouraged researchers to assess the effectiveness of braces and taping procedures at limiting rotary motion in the transverse plane. Cordova et al. (2002) noted that while numerous studies have examined the efficacy of external ankle supports at limiting passive motion, the effects of ankle braces on

ankle kinematics and kinetics during dynamic activities such as running, cutting, and lateral movements are poorly understood. Finally, Gross and Liu (2003) indicated in their review that a new generation of ankle braces is being recommended by clinicians and used by the general population. Gross and Liu recommend that clinicians should be surveyed to

determine which ankle braces are used most commonly. This initial effort could be followed by clinical trials to determine the effects of these braces on ankle sprain injury rates during selected activities as compared to control groups. Additional related questions raised by Gross and Liu include: the influence ankle braces may have on injuries to more proximal lower extremity joints, the effects of long-term ankle brace use on muscle strength, and the length of time after an ankle sprain that a brace should be worn to reduce the risk of re-injury adequately.

No published data are available describing which ankle braces clinicians most commonly recommend or which braces individuals acquire on their own. Additionally, no data are available regarding the factors clinicians consider when they recommend a specific ankle brace. The purpose of this study is to address these deficiencies in the literature.

Studies documenting decreased incidence of ankle sprain using ankle braces Semi-rigid braces

At least two prospective studies have demonstrated reduction in the incidence of ankle sprains using the semi-rigid Aircast Sport-Stirrup (Aircast, Inc.) brace (Surve, 1994; Sitler, 1994). Surve et al. reported that soccer players with a history of previous ankle sprain who wore a semi-rigid ankle brace over the course of one season (Aircast Sport-Stirrup) experienced a significant reduction in the incidence of ankle sprains. The incidence of ankle

sprain for those with a history of ankle sprain was 0.14 injuries/1,000 playing hours in the braced group versus 0.86 injuries/1,000 playing hours for the unbraced group. Sitler et al. followed U.S. Military Academy cadets over two seasons of intramural basketball play. The authors reported that the subjects had no “preparticipation clinical, functional, or

radiographic evidence of ankle instability.” Of 789 subjects who wore the Sport-Stirrup ankle brace, 11 suffered ankle injuries. Among 812 subjects in the control group, 35 incurred ankle injuries.

Additionally, the results of two studies offer strong evidence that a semi-rigid brace worn outside of paratroopers’ boots can prevent ankle injuries (Amoroso, 1998; Schumaker, 2000). Schumaker et al. reported 1.5 injuries/1,000 jumps in a braced group and 4.5

injuries/1,000 jumps in an unbraced group. Amoroso et al. reported data for paratrooper trainees who performed five jumps each. Seven inversion ankle sprain injuries were reported for a group of 376 trainees who did not wear this brace. Only one inversion ankle sprain was observed in a group of 369 trainees who wore the brace.

The previously reviewed studies indicate that semi-rigid ankle braces, and

specifically the Aircast Sport-Stirrup, are effective at reducing the incidence of ankle sprains for individuals with or without a history of a previous ankle sprain injury. Activities included in these studies were basketball, soccer, and high impact landing during paratrooper training.

Lace-up and other braces

The results of several studies also indicate that wearing a lace-up brace may effectively reduce the incidence of ankle sprain injuries. The head football coach at Wake Forest University mandated in 1980 that all players have their ankles taped prior to practices

and games. He allowed players to begin choosing between tape and a lace-up brace in 1982. For six years the department maintained records detailing the type of support used and the injuries that occurred. The records were then retrospectively reviewed. Overall, taped players incurred 4.7 sprains/1,000 exposures and braced players incurred 2.9 sprains/1,000

exposures. Injury rates were greater for taped players across all positions. Readers should note that the players were encouraged to tighten the lace-up braces as they felt necessary. The authors did not specify the type of lace-up brace(s) used (Rovere, 1988).

Sharpe et al (1997) studied the effect of the Swede-O Universal Ankle Support (North Branch, MN) canvas lace-up brace on reducing recurrence of ankle sprain injury for female soccer players. Subjects were varsity female soccer players at a Division III college who had a previous history of ankle sprain injury. The players’ medical records were retrospectively studied over a five-year period. The recurrence incidence for the group who wore the Swede- O brace was significantly less than the taped and control groups. The authors reported that the braced group incurred no ankle sprains in approximately 790 total game and practice exposures. Based on the previously reviewed studies, it appears that wearing a lace-up brace effectively reduces the incidence of initial and recurrent ankle sprains. Conducting a larger prospective study tracking specific braces and the observed rates of injury and re-injury during additional sporting activities would increase the degree of confidence in the previous claims.

Tropp et al (1985) studied the prevention of ankle sprains using the “Step 1” (Patrick Inc., Linkoping, Sweden) brace, which consists of a plastic sole with medial and lateral straps tightened to an anchor above the malleoli. The subjects were Swedish male soccer players in the national league Division VI. Seventeen percent of the participants in the control group

(n=171) suffered an ankle sprain and 3% of the participants in the braced group (n=60) incurred an ankle sprain.

Mechanism of Injury

Understanding the mechanisms of injury for ankle sprains is important to guide future studies that would evaluate the effects of ankle braces on ankle motion. Most ankle sprains involve the lateral joint structures and occur after the ankle joint is excessively inverted and plantar flexed. Garrick (1977) described the following three mechanisms for ankle sprain injury: 1) a poorly executed cutting motion, 2) landing on an irregular surface, and 3) landing on another player’s foot.

Ankle injuries occur as a result of both contact and non-contact events. Video analysis has revealed that injuries during soccer matches were often due to player-to-player contact resulting in either the player landing in a vulnerable, inverted position or being forced into plantar flexion (Anderson, 2004). McKay et al (2001) observed 10,393 basketball

participations, and reported that the most common mechanism of injury (MOI) for ankle sprains during basketball was landing from a jump. The authors reported that half of the landing injuries involved landing on another player’s foot and half involved landing on the court surface. The next most common MOI was a sharp twist or turn (30%).

Wright et al. (2000) used “muscle driven computer simulations” to explore the mechanism for ankle sprains injuries. The movement studied was described as a simulation of the first half of the stance phase of a side-shuffle movement. A “sprain” was counted for a given stimulation when the torque or angular displacement at the subtalar joint exceeded an

established value. The authors reported that the joint angle of the subtalar joint at foot touchdown did not have a “considerable influence on sprain occurrence.” The authors

reported, however, that increased talocrural plantar flexion angle at touchdown resulted in an increase in “sprain” occurrence.

Effects of ankle braces on ankle joint kinematics and kinetics

Numerous investigators have assessed the efficacy of ankle braces for restricting passive joint motion. The majority of these efforts included at least an analysis of inversion and eversion (Hartsell, 1997; Greene, 1990; Eils, 2002; Gross, 91, 92, and 94; and Siegler, 1997). Braces have usually been evaluated for their ability to restrict inversion since excessive inversion, in addition to plantar flexion motion, is often considered the primary motion responsible of an ankle sprain injury. Most investigators have demonstrated that the test braces restrict inversion and eversion compared with unbraced testing. Several studies have also included measures of restriction of plantar flexion and dorsiflexion (Cordova, 2000). Very limited data are available, however, describing the influence ankle braces have on internal and external rotation range of motion (Eils, 2002; Siegler, 1997). Wilkerson (2002) details the importance of stability in the transverse plane and the role of the anterior talofibular ligament in restricting external rotation of the leg on the talus.

Cordova et al. (2000) performed a meta-analysis of nineteen studies to analyze the effect of ankle braces and taping on ankle joint range of motion before and after exercise. The analysis compared the effects of tape, semi-rigid braces, and lace-up braces on inversion, eversion, dorsiflexion, and plantar flexion motion both before and after exercise. Every condition significantly differed from the control condition (no tape or brace). Differences

existed, however, in the amount of motion allowed between the types of braces and tape. Inversion and eversion were significantly less for pre-exercise testing and when semi-rigid braces were worn, compared with taped conditions and other lace-up braces. After exercise the semi-rigid braces offered a level of support similar to pre-exercise, whereas the tape and lace-up braces loosened and allowed more inversion and eversion range of motion.

Cordova et al. indicated that the effect sizes were rather small for the data on restriction of plantarflexion and dorsiflexion motion. The tape and lace-up braces restricted plantar flexion and dorsiflextion more significantly than the semi-rigid braces. The tape condition provided greater restriction of dorsiflexion than the lace-up condition. Cordova et al reported no significant difference between the pre- and post-exercise effect on plantar flexion and dorsiflexion motions for the tape and lace-up conditions, indicating that there was not significant loosening in this plane. The general findings of this meta-analysis are

consistent with the structure of the braces. Semi-rigid braces generally offer greater medial and lateral support to restrict frontal plane motion. Additionally, these braces are made of stiffer material, which should provide a more lasting level of support throughout an exercise bout. Tape and lace-up braces do not appear to restrict frontal plane motion as well as semi- rigid braces. Lace-up braces, however, appear to offer valuable additional support in the sagittal plane, which may contribute to a reduction of ankle sprain incidence.

Two investigations have studied the ability of braces to restrict internal and external rotation of the foot relative to the leg in response to a passively induced force (Siegler, 1997; Eils, 2002). Eils et al. compared 10 braces (one rigid, five semi-rigid, and four “soft” braces) and reported relatively consistent measures among the braces for internal and external rotation motion. Siegler et al. tested the three-dimensional support of two semi-rigid braces

(Aircast Sport-Stirrup, Aircast Inc. and Active Ankle, Active Ankle Systems) and two lace- up braces (Swede-O Universal, Swede-Inc. and Ascend, AOA Corporation). All braces provided significant support for internal rotation of the foot relative to the leg compared to the no brace condition. Both semi-rigid braces provided significantly greater restriction of motion than the lace-up braces. Additionally, the Active Ankle brace provided significantly greater restriction than the Aircast brace. All braces provided significant support for external rotation of the foot relative to the leg. The semi-rigid braces, however, provided significantly more support than the lace-up braces.

Several investigators have attempted to simulate dynamic inversion while subjects stand on a tilting platform and wear various ankle braces (Eils, 2002; Eils, 2003; Nishikawa, 2000; Vaes, 1998; Ubell, 2003). This dynamic inversion motion is similar to events that occur during a game situation when players land awkwardly on the sport surface or land on an opponent’s foot. Eils et al. (2002) studied the effects of one rigid, five semi-rigid, and four soft braces for motion restriction with subjects who had a history of previous ankle sprain injury. The investigators measured passive inversion, as well as inversion that occurred when subjects stood on a platform that was suddenly tilted in the direction of inversion. All braces significantly reduced inversion for both types of testing compared with unbraced testing. The restriction of inversion for passive testing was less than the inversion restriction for platform testing, however, the measurements were significantly correlated for the two tests. These results suggest that the amount a brace restricts passive inversion is indicative of the relative amount of protection the brace might provide against rapidly induced inversion during functional weight-bearing activities.

Vaes et al. detailed that subjects with a history of ankle sprain injury demonstrated a decrease in inversion motion and inversion speed during a 50-degree ankle sprain simulation while wearing an Aircast Sport-Stirrup compared to a control group. Nishikawa et al.

reported the Aircast Sport-Stirrup (semi-rigid plastic), Donjoy RocketSoc (lace-up cloth) braces, and ankle taping provided similar inversion and eversion support during a 10-degree tilt on a perturbation platform.

Two investigators have examined more dynamic inversion tilt tasks. Ubell et al. (2003) imposed a 24-degree inversion tilt on subjects who landed on one leg with an intensity intended to approximate two times the force of body weight. Each subject performed the task for five trials in each of three braces (Aircast Sport Stirrup semi-rigid, Bledsoe semi-rigid, and Swede-O Universal lace-up) and in a no brace condition. Subjects were instructed to resist the inversion motion upon landing. A landing was considered

successful if the subject allowed less than 24 degrees of ankle inversion. The average success rate for all three braces was 44%. During the unbraced condition subjects demonstrated a 24% success rate. Only the semi-rigid braces, however, resulted in significantly better success rates than the unbraced condition.

Eils et al. (2003) imposed rapidly induced inversion on subjects who landed on the ground after jumping down from a platform. Eils et al. reported use of each of the ten braces (one rigid, five semi-rigid, and four “soft” braces) resulted in significantly reduced inversion compared to the no brace condition. An interesting finding was that the braces that restricted inversion most effectively during the free fall from the platform resulted in lower maximum inversion angle and maximum inversion velocity during the landing. The authors reported this relationship was relatively constant across all brace models. The results suggest that the

influence braces have on ankle position prior to landing may be a possible mechanism through which ankle braces reduce the number of ankle sprain injuries.

Relatively few investigators have examined the influence of ankle braces on ankle joint kinematics and kinetics during more dynamic activities such as running (Hamill, 1986) and lateral movements (Cordova, 1998; Simpson, 1999). Hamill et al. (1986) reported no differences in sagittal plane or frontal plane ground reaction forces among the no brace, taping, and “boot-type ankle stabilizer” conditions during a 5 m/sec running task. The investigators reported, however, that the variability of the forces was consistently greater for the no brace condition.

Another area of interest is the effects of ankle braces on joint kinematics and ground reaction forces during lateral movements and quick cutting motions. Cordova et al. (1998) tested subjects as they performed a lateral dynamic movement at 80-90% of their maximal speed during three conditions: no brace (control), Aircast Sport-Stirrup brace, and an Active Ankle brace. No significant differences in inversion peak impact force, maximum loading force, or peak propulsion force were observed among the brace and control conditions. Kinematic and moment values were not reported. Simpson et al. (1999) tested subjects with a history of two or more ankle sprains using a lateral shuffle movement task that involved a reversal of movement direction. The movements were performed at 85% of maximum velocity and required that subjects create the change of direction on the previously injured ankle. Subjects performed the activity using two semi-rigid braces (Aircast Sport Stirrup and Malleoloc) and a Swede-O Universal lace-up brace. None of the braces restricted inversion compared to the no brace condition. The amount of plantar flexion was significantly less (3 to 4 degrees) for each of the braced conditions compared to the control condition. The

Swede-O brace restricted maximum dorsiflexion significantly more than the two semi-rigid braces (differences from 2 to 4 degrees).

Effects of ankle braces on functional performance

Even though ankle braces have been effective in reducing the incidence of ankle sprains, athletes may be less likely to use them if they believe a given brace will adversely influence performance. Clinicians’ beliefs about the effect of ankle braces on functional