INJURY CLINIC
Sports Med. 20 (1): 53-57. 1995 0112-1642/95/000HXl53/S02.50/0
Effectiveness of Prophylactic Ankle Stabilisers for Prevention of Ankle Injuries Michael R. Sitler l and MaryBeth Horodyski 2 1 Department of Physical Education, Temple University, Philadelphia, Pennsylvania, USA 2 Department of Exercise and Sport Sciences, University of Florida, Gainesville, Florida, USA
Contents Summary . . . . . . . . . . . . . . . . . . . . . . . 1. Traditional Methods for Prevention of Ankle Injury 2. Prophylactic Ankle Stabilisers (PAS) . . . . . . . . 3. Clinical Studies with PAS . . . . .. . . . . . . . . . 4. Study Design and Effectiveness of PAS. . 5. Conclusions . . . . . . . . . . . . . . . . . . . . . .
Summary
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Ankle injuries are common at many levels of athletic participation_ Arelatively recent approach in injury intervention is the use of prophylactic ankle stabilisers (PAS)_ PAS are used with the intention of reducing the frequency and severity of ankle injuries in a cost-effective manner. To date, 4 studies have been completed to determine the clinical efficacy of PAS. Although all of the studies have methodologicallimitations, a general consensus of agreement exists among the findings: PAS are effective in reducing the incidence of acute ankle sprains. However, the effect of PAS on ankle sprain severity remains unclear, as varying results have been reported. PAS do not increase the risk of knee injuries. The use of PAS for ankle injury reduction appears to be justified although further research is required.
The talocrural, or ankle, joint is one of the most frequently injured joints of the body,l1] It is estimated that each year 1 million people experience acute ankle injuries,[2] the most common of which is the inversion sprain,£I,3-5] Acute ankle sprains account for approximately 15% of all sports injuries,£6-8]
1. Traditional Methods for Prevention of Ankle Injury Various injury intervention systems e.g. flexibility and proprioceptive training programmes, have been used to reduce the incidence of ankle sprains. In 1946, Quigley et al.l9] advocated taping
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of ankles, to limit excessive inversion and eversion movement while not inhibiting dorsiflexion and plantar flexion. Clinical support for prophylactic ankle taping, however, has been largely anecdotal, and very little empirical evidence exists to support its use. Prophylactic ankle taping is not without controversy. Although ankle taping is supported by the clinical work of Garrick and Requa,DO] experimental and exercise data present varying results of its effectiveness to stabilise the talocrural and subtalar jointsJIl-IS] Rarick et aUIS] reported that tape loses 40% of its supportive strength after 10 minutes of vigorous exercise, and Myburgh et al.[I4] determined that tape offered no significant ankle support after 1 hour of exercise. It has yet to be determined, however, the amount of support needed to protect the ankle against injury while not compromising performance. Ankle taping has also been criticised for its expense. In 1988, Rovere et al,[16] estimated that it cost $US400.00 to tape both ankles of one American football player for an entire University football season. In 1991, Burks et al.[l7] estimated that it cost $US16 000 to tape players' ankles, for one University football team for one season. Because of inflation, ankle taping is much more costly in the US today.
2. Prophylactic Ankle Stabilisers (PAS) An alternative to ankle taping is use of prophylactic ankle stabilisers (PAS). Ranging from cloth lace-on braces to semirigid, bi-malleolar orthoses made of thermoplastics and plastic polymers, PAS have become increasingly popular. This increased use is purportedly due to the greater effectiveness of PAS in reducing ankle injuries,[IO] ease of application and maintenance, and relative cost effectiveness compared with tapingJl6] The first noncommercial semirigid PAS were developed in 1974, constructed of Orthoplast™ ,DS] These were developed as an alternative to plaster casting. Jackson et alJS] determined that functional recovery of ankle sprains was prolonged by cast immobilisation. Alternatively, use of semirigid PAS allowed for con© Adis Intemational Limited. All rights reserved.
trolled ankle motion, and prognosis was improved. The first line of commercial semirigid PAS was the Aircast AirStirrupTM (Aircast Inc., Summit, New Jersey, USA).[IS] Softshell PAS were first introduced in the early 1980s. Swede-O-UniversafM (Swede-O-Universal, North Branch, Minnesota, USA) was one of the first types of softshell PAS on the market. Softshell PAS are constructed of a variety of materials, including canvas and neoprene rubber, and come in different sizes and shapes. Semirigid and softshell PAS are currently used to prevent ankle injuries and to protect ankles postinjury.
3. Clinical Studies with PAS In 1985, Troop et alJ19] were the first to report on the clinical efficacy of PAS. They prospectively studied the effectiveness of proprioceptive ankle disc training and a semirigid ankle orthosis in reducing the incidence of ankle sprains. Soccer players (n =439) from 25 Swedish soccer teams were randomly assigned to 1 of 3 treatment groups: (1) ankle orthosis; (2) proprioceptive disc training; or (3) control- no ankle orthosis or disc training. All teams were prospectively followed for 6 months, beginning with the preseason training sessions and ending with the spring season. Tropp et alJ19] reported that the ankle orthosis and disc training were equally effective in reducing the frequency of recurrent ankle sprains. However, between the 2 treatment groups, no significant reduction in the frequency of ankle sprain occurred for players without any history of ankle injury. In 1988, Rovere et alJ16] reported on the retrospective comparison of taping versus a cloth laceon ankle stabiliser (specific brace not identified) in preventing ligament and bone injuries of the ankle. Approximately 52000 athlete-exposures were recorded during this 7-year period. Except for the first year of the study, when all players were taped, the decision as to being taped or braced was playerdependent. These researchers determined that players who wore braces or low-top shoes had significantly fewer ankle injuries than players who were not taped or who wore high-top shoes. Braced Sports Med. 20 (1) 1995
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players who wore low-top shoes had the lowest incidence of ankle injuries. Sitler et at.l 20] conducted a prospective, randomised clinical study to determine the efficacy of the Aircast SportStirrupTM in reducing the frequency and severity of ankle injuries. A total of 1601 (male and female) military cadets participated in the study. The researchers controlled for athlete-exposure, type of playing surface, history of ankle injury, type of athletic shoe, and brace assignment (randomised). Approximately half of the cadets participating in the study were braced bilaterally and half were nonbraced, serving as a control group. Intramural participation was not allowed until all equipment requirements of the study were met. The results of the study revealed that use of the brace significantly reduced the frequency but not the severity of ankle injury. In addition, no significant difference existed in the number of knee injuries between braced and nonbraced individuals. Of interest is that attitudes towards wearing the brace improved as its use increased. Surve et al. 121 ] in a prospective, randomised study evaluated the effectiveness of the Aircast Sport StirrupTM in reducing the incidence of ankle sprains in 629 male senior-level soccer players. Brace assignment (approximately half of the players were braced and half were not) and history of ankle injury were controlled. Use of the brace significantly reduced the incidence of ankle sprains in previously sprained ankles, but not in previously uninjured ankles. Braced players also had less severe ankle sprains - but for previously sprained ankles only. No significant difference existed in the incidence of knee injuries between players with braces and the control group, regardless of history of ankle injury.
4. Study Design and Effectiveness of PAS A variety of research designs have been used to determine the effectiveness of PAS in reducing the incidence of ankle sprains. Sitler et at.l 20] and Surve et al.[ 21 1 employed randomised clinical trial designs and Troop et al.[19] used a quasirandomised clinical trial design in that, although © Adis Intematlonal Limited. All rights reserved.
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initial treatment group assignment was randomised, braced players self-selected whether or not to use the orthosis. Conversely, Rovere et at.l 16] used a longitudinal design which was retrospectively implemented. Randomised clinical trials allow for cause-andeffect relationships to be tested. Such study design allows for the control of independent variables, experimentally or statistically, which are believed to have an effect on the dependent variables of interest (e.g. type of injury, frequency and severity). However, a limitation is that it is not always possible to randomly assign study participants, particularly in competitive athletics. 1161 Associations which are replicated over time and over a number of properly designed studies, provide support that cause-and-effect relationships may exist. 122] An important aspect of clinical research is the external validity, or generalisability, of the research results. The question arises as to what extent can the results of a study conducted at one level (e.g. college, professional, intramural) be generalised to another level? The same question arises regarding different types of braces (e.g. semirigid vs cloth lace-on). Although providing the scientific rigour that is essential when conducting clinical research, it is not clearly known to what extent the results of the study of Sitler et al. [201 can be generalised. This is due, in part, to differences in height, weight, playing experience, exposure to injury, and level of play which existed in this study population as compared with the collegiate and professional levels. Essential to clinical research is the need to control confounding variables. Confounding variables have the potential of influencing the dependent variable, thus resulting in spurious research conclusions. Randomised clinical trials[20, 21 1 allow control and randomisation of known and unknown confounding variables, respectively. Conversely, longitudinal studies l161 do not, thus mitigating the establishment of an unequivocal cause-and-effect relationship. Changes in coaching philosophy, conditioning programmes, footwear and playing surfaces, environmental factors and rules are all Sports Med. 20 (l) 1995
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examples of potential confounding variables. Brace selection bias is another potential confounding variable. Brace assignment was only controlled (randomised) in the Sitler et alPO) and Surve et aU 21 ) studies. Individuals using PAS in the study of Troop et al.£19) had the option of not using the brace, and those in the Rovere et al.[16) study were permitted to self-select their treatment option (taping vs bracing). Sample size is an important consideration when conducting clinical research. This is due to the concept that statistical power, the ability to find differences when differences exist, is dependent on sample size. Thus, when power is low, although differences may exist, the probability of rejecting the null hypothesis is also low. A relatively small injury severity sample size can result in an inability to find significant differences PO) Accordingly, determination of the sample size needed to conduct clinical research must be established a priori. In clinical research, establishment of risk of injury is typically based on athlete-exposures (e.g. 1 athlete participating in 1 practice or game equals 1 athlete-exposure). Basing risk of injury on athleteexposure[20.21 1allows meaningful interpretation of the relative exposure of injury for different levels of the independent variable (e.g. braced vs nonbraced players), whereas basing risk of injury on the number of participants[16.19) may not. This is due to the fact that differences in exposure between groups are not recorded, resulting in unreliable estimates (conservative or liberal) of the true risk of injury. The means by which PAS prevent ankle injuries remains an enigma. Results of studies suggest that PAS provide mechanical support to the ankle, limiting excessive inversion and eversion movements.[16,20) Biomechanical studies support this contention.f1 4,23,24) Conversely, some studies suggest that another mechanism may be concurrently or independently involved.f1 9,2I) In these 2 studies, the incidence of ankle sprains was reduced only for individuals wearing PAS who had a history of prior ankle sprains. Assuming that proprioceptive deficits occur following an ankle sprain, one explana© Adis Internaflonal Umited. All rights reserved.
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tion for this finding is that bracing facilitates proprioception of the ipsilateral injured limb, resulting in increased functional stabilisationPl) Additional biomechanical and clinical research is needed to further elucidate the exact mechanism(s) by which PAS are effective in reducing ankle injuries.
5. Conclusions Although the studies cited have methodological limitations, a general consensus of agreement exists among the findings that PAS are efficacious in reducing the incidence of acute ankle sprains. However, the effect of PAS on ankle sprain severity remains unclear, as varying results have been reported. In addition, PAS do not increase the risk of knee injuries. In conclusion, the use of PAS for ankle injury reduction appears to be justified, although unequivocal confirmation of this finding can only be made by additional supporting research.
References
I. Lassiter T, Malone T, Garrick J. Injury to the lateral ligaments of the ankle. Orthop Clin NAm 1989; 20: 629-40 2. Miller E, Hergenroeder A. Ankle bracing. Pediatr Clin N Am 1990; 37: 1175·85 3. Altarian D, McCrackin H, DeVito D, et al. Biomechanical characteristics of human ankle ligaments. Foot Ankle 1985; 6: 54-8 4. Greene T, Roland C. Acomparative isokinetic evaluation of a functional ankle orthosis on talocalcaneal function. J Orthop Sports Phys Ther 1989; 11: 245-52 5. Gross M, Lapp A, David J. Comparison of Swede-O-Universal Ankle Support and Aircast SportStirrup orthoses and ankle tape in restricting eversion-inversion before and after exercise. J Orthop Sports Phys Ther 1991; 13: 11-9 6. Blythe D, Mueller F. An epidemiological study of high school football injuries in North Carolina, 1968-1974 final report. Washington, D.C.: Government Printing Office, 1974: 67 7. Garrick J. The frequency of injury, mechanism of injury, & epidemiology of ankle sprains. Am J Sports Med 1977; 5: 241-2 8. Jackson D, Ashley R, Powell J. Ankle sprains in young athletes. Clin Orthop Rei Research 1974; 101: 201-15 9. Quigley T, Cox J, Murphy J. Protective wrapping for the ankle. JAMA 1946; 132: 924 10. Garrick J, Requa R. Role of external support in the prevention of ankle sprains. Med Sci Sport 1973; 5: 200-3 II. Fumich R, Ellison A, Guerin G, et al. The measured effect of taping on combined foot and ankle motion before and after exercise. Am J Sports Med 1981; 9: 165-70 12. Greene T, Hillman S. Comparison of support provided by a semirigid orthosis and adhesive ankle taping before, during, and after exercise. Am J Sports Med 1990; 18: 498-506 Sports Med. 20 (1) 1995
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13. Laughman R, Carr T, Chao E, et al. Three-dimensional kinematics of the taped ankle before and after exercise. Am J Sports Med 1980; 8: 425-31 14. Myburgh K, Vaughan C, Isaacs S. The effects of ankle guards and taping on joint motion before, during, and after a squash match. Am J Sports Med 1984; 12: 441-6 15. Rarick L, Bigley G, Karst R, et al. The measurable support of the ankle joint by conventional methods of taping. J Bone Joint Surg Am 1962; 44A: 1183-90 16. Rovere G, Clarke T, Yates C, et al. Retrospective comparison of taping and ankle stabilizers in preventing ankle injuries. Am J Sports Med 1988; 16: 228-33 17. Burks R, Bean B, Marcus R. Analysis of athletic performance with prophylactic ankle devices. Am J Sports Med 1991; 19: 104-6 18. Stover R. Air Stirrup management of ankle injuries in the athlete. Am J Sports Med 1980; 8: 360-5 19. Troop H, Asking C, Gillquist J. Prevention of ankle sprains. Am J Sports Med 1985; 13: 259-62
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20. Sitler M, Ryan J, Wheeler B, et al. The efficacy of a semirigid ankle stabilizer to reduce acute ankle injuries in basketball. Am J Sports Med 1994; 22: 454-61 21. Surve I, Schwellnum M, Noakes T, et al. A fivefold reduction in the incidence of recurrent ankle sprains in soccer players using the sport-stirrup orthosis. Am J Sports Med 1994; 8: 601-6 22. Looney M, McAllister B. Is critical analysis of sports medicine research necessary? J Athl Train 1989; 24: 333-6 23. Bunch R, Bednarski K, Holland D, et al. Ankle joint support: a comparison of reusable lace-on braces with taping and wrapping. Physician Sports Med 1985; 13: 59-62 24. Greene T, Hillman S. Comparison of support provided by a semirigid orthosis and adhesive ankle tape before, during and after exercise. J Orthop Sports Phys Ther 1990; 18: 498-505
Correspondence and reprints: Dr Michael Sitler, 125 Pearson, Temple University, Philadelphia, PA 19122, USA.
Sports Med. 20 (1) 1995