February 2011

Inversion ankle sprains: Seeking optimal support

Maximal protection of multiple ankle ligaments following a sprain requires a taping technique or brace that provides restraint of rotary talocrural and subtalar joint displacements within the transverse plane as well as restraint of inward hindfoot motion within the frontal plane.

By Gary Wilkerson, EdD, ATC

The lateral ankle sprain is the most common musculoskeletal injury associated with physical activity, but is often dismissed as a relatively trivial problem that is not expected to cause any long-term disability. Foot inversion (i.e., inward turning of the sole) is always a component of the injury mechanism that damages the lateral ankle ligaments, but numerous factors influence the nature and severity of the pathology that may result from the traumatic event. Inadequate treatment can result in suboptimal healing of damaged ligaments, which leads to recurrent traumatic episodes (i.e., chronic ankle instability) and progressive arthritic degeneration. 1-4

The widely-used term “ankle joint” suggests the existence of a single joint between the leg and foot segments, which does not accurately represent the complex structure and integrated function of two distinct joints that both contribute to ankle motion.5 The key component of the ankle is the talus, which functions in a manner somewhat similar to that of a ball-bearing. Its superior, medial, and lateral articular surfaces are encased within a socket (the tibio-fibular mortise), which forms the talocrural joint (upper ankle joint). When the ankle ligaments are intact, the functional axis of talocrural joint motion has a relatively transverse orientation that is aligned with the distal tips of the tibial and fibular malleoli. Two sets of articulations between the talus and the calcaneus form the subtalar joint (lower ankle joint), which rotates around a functional axis that has an approximate orientation of 45° in the sagittal plane (i.e, with the talocrural joint in a neutral position).

Figure 1. Simultaneous internal rotation of talus and external rotation of the tibia and fibula, which is primarily restrained by the ATFL. Reprinted with permission from reference 19.

Closed-chain subtalar joint inversion induces external rotation of the tibio-fibular ankle mortise (and vice-versa). Relative to the externally rotating tibio-fibular mortise, the talus internally rotates, and the anterior talo-fibular ligament (ATFL) is torn by excessive displacement of the bones in opposite directions (Figure 1). After the ATFL ruptures, the primary remaining restraint to further internal rotation of the talus is the posterior tibio-talar ligament (PTTL). Located on the posteromedial aspect of the ankle joint, the PTTL is the deep posterior component of the deltoid ligament (Figure 2). Because foot inversion can damage structures on the medial aspect of the ankle, the term “lateral ankle sprain” is often an incomplete designation for the pathology that results. In addition to the PTTL damage, the articular cartilage on the anteromedial margin of ankle joint can be damaged by forceful impact; sometimes referred to as a “kissing” lesion (Figure 3).3,6

In many cases, rupture of the ATFL is associated with damage of the calcaneo-fibular ligament (CFL). The ATFL is most vulnerable to injury when the foot is in a position of plantar flexion, but the CFL is most vulnerable in a position of dorsiflexion. Sudden inversion of the foot has been shown to elicit a reflexive postural response that lowers the body’s center of mass, which momentarily reduces the magnitude of the vertical ground reaction force acting on the ankle.7 This suggests that a two-stage sprain mechanism might explain the combination of ATFL and CFL rupture. Immediately after the ATFL is damaged by a combination of plantar flexion and inversion, a combination of reflexive hip flexion, knee flexion, and ankle dorsiflexion may make the CFL vulnerable to continuation of inward displacement of the sole of the foot. Because the CFL maintains a parallel relationship to the orientation of the functional axis of the subtalar joint throughout the range of talocrural joint motion, rotation of the dorsiflexed foot around a non-functional longitudinal axis, which induces lateral tilt of the talus, is the most likely mechanism of CFL disruption.

Figure 2. Posterior view (A) of posterior tibio-talar ligament (PTTL) and calcaneo- fibular ligament (CFL). Superior view (B) of PTTL and anterior talo-fibular ligament (ATFL). Reprinted with permission from reference 9.

Following rupture of both the ATFL and CFL, open-chain lateral tilt of the talus within the tibio-fibular mortise is evident on radiographic images. However, this radiographic finding is highly variable, and symptoms of chronic ankle instability frequently affect patients who do not exhibit an abnormal amount of talar tilt. When the ATFL is disrupted, the antero-lateral portion of the talus lacks restraint against excessive internal rotation and anterior translation from the tibio-fibular mortise, which is referred to as antero-lateral rotary instability (ALRI).8,9 The existence of articular cartilage lesions has been shown to have a strong association with ATFL and PTTL laxity, which imposes a torsional shear load during weight-bearing activity that is concentrated on the medial aspect of the dome of the talus.1 The inversion injury mechanism can also create subtalar ligament lesions that are often unrecognized by clinicians, which may affect the cervical ligament (CL), the interosseus talo-calcaneal ligament (ITCL), or the lateral talo-calcaneal ligament (LTCL).10-12 Thus, ALRI of the talocrural joint, or instability of the subtalar joint, can lead to a chronic ankle dysfunction without damage to the CFL.

Figure 3. Combined anterior translation and internal rotation of the talus in relation to the tibio-fibular mortise, which displaces the antero-lateral portion of the talus (ALRI) and may result in antero-medial impact of articular surfaces. Reprinted with permission from reference 9.

Chronic ankle instability can result from ligament laxity (i.e., mechanical instability), inadequate neuromuscular control (i.e., functional instability), or a combination of the two factors.13 The therapeutic methods used for acute sprain management may affect the rate and quality of ankle ligament healing,14,15 and rehabilitation that is focused on restoration of muscle strength and neuromuscular control of unilateral postural balance may enhance recovery of normal ankle function.16 Rapid restoration of the ability to perform normal physical activities is obviously a primary goal of ankle sprain treatment, but the ligament healing process may require up to a year for maximum tensile strength to be restored. Activities that involve rapid acceleration and deceleration, sudden change of direction, or landing from jumps can impose extremely large tensile loads on incompletely healed collagen fibers, which may result in development or exacerbation of ligament laxity, or may produce another acute ligament disruption. Furthermore, some degree of articular cartilage damage is sustained in approximately 90% of cases that involve rupture of the ATFL.3 Prevention of recurrent inversion sprains is crucial for avoidance of chronic ankle instability and progressive joint surface degeneration.2,3,6

Cloth adhesive tape has been used for external ankle support for more than a century,17 and commercial ankle braces have been widely utilized for the same purpose over the past several decades. The key component of the most widely recognized ankle taping procedure is the application of long “stirrup” strips of adhesive tape that are aligned with the long axis of the lower leg.17 Stirrup-type ankle braces have semi-rigid components that cover the medial and lateral aspects of the lower leg and ankle and the plantar aspect of the hindfoot, and many lace-up ankle supports incorporate fabric straps that function like tape stirrup strips. Such motion restraint systems can provide effective resistance against inward displacement of the hindfoot and lateral tilt of the talus within the frontal plane, but they do not provide any substantial degree of restraint to subtalar joint inversion, anterior translatory displacement of the talus, or internal rotation of the talus within the transverse plane. 18-21 Furthermore, there is no evidence in the medical literature that any ankle brace effectively restrains ALRI of the talus.21

Figure 4. Vertical and antero-posterior components of vector created by tension within the subtalar sling, which is oriented perpendicular to the functional axis of the subtalar joint. Reprinted with permission from reference 19.

The addition of the “subtalar sling” ankle taping procedure with tape stirrups and other components of the widely-accepted standard method for tape application has been shown to dramatically increase restraint to open-chain subtalar inversion in uninjured subjects,22 anterior translation of the foot segment in uninjured subjects,23 and internal rotation of the foot segment of a cadaver specimen with disrupted ankle ligaments.24 With the talocrural and subtalar joints maintained in a neutral position, a strip of semi-elastic/high-strength adhesive tape is anchored to the plantar aspect of the forefoot and wrapped around the lower leg in spiral configuration, which positions the longitudinal fibers of the tape on the lateral aspect of the ankle in an orientation that is approximately perpendicular to the functional axis of the subtalar joint in the sagittal plane (Figure 4). Because external rotation of the leg segment increases tension within the longitudinal fibers of the tape, a lifting force is created on the lateral border of the forefoot, which effectively reverses the normal direction of torque transmission between the leg and foot segments; in other words, tension within the subtalar sling tends to induce eversion of the forefoot when the leg externally rotates (Figure 5).

Figure 5. Restraint of antero-lateral rotary instability (ALRI) provided by tension within the subtalar sling, which increases with inversion of the subtalar joint and external rotation of the leg. Reprinted with permission from reference 19.

Recent research on the effects of ankle support systems has emphasized the necessity of analyzing ankle kinematics under conditions that closely replicate the circumstances associated with ankle ligament injury, i.e., unanticipated high-velocity inversion displacement with axial loading of the joint surfaces.19 Deceleration of closed-chain inversion displacement by an ankle support may allow for generation of protective muscle tension before the ligaments are subjected to a disruptive load level, which might be a factor that is just as important as restriction of the maximum range of joint motion.25 Compared to an unsupported condition, the addition of the subtalar sling component to the standard ankle taping procedure has been found to significantly reduce closed-chain peak inversion velocity (34% versus 16%) and average inversion velocity (13% versus 6%) after the tape has been loosened by physical activity.26 Clearly, the collective evidence strongly supports the superiority of subtalar sling system for protection of the talocrural and subtalar ligaments from the tensile loads imposed by the complex joint displacements that can be produced by physically demanding activities.

The necessity of access to a clinician who possesses the necessary skill for proper application of the subtalar sling taping procedure, the cumulative cost of the necessary single-use materials, and skin irritation associated with repeated tape applications or prolonged use present major limitations for widespread utilization of the concept. An ankle brace designed to replicate the mechanical effects of the subtalar sling taping procedure incorporates a semi-rigid foot component that is secured on the dorsum of the forefoot, a semi-rigid leg component that conforms to the anterior contours of the tibia, a medial hinge that connects the foot and leg components, and a strapping system that restrains oppositely directed rotary displacements of the leg and foot segments in the transverse plane through development of strap tension (Figure 6). This brace design has been found to provide a similar level of closed-chain inversion restriction and inversion deceleration as that provided by the subtalar sling taping procedure.27

Figure 6. Postero-lateral view (A) and postero-medial view (B) of an ankle brace designed to replicate the effects of the subtalar sling ankle taping procedure (Fillauer, LLC, Chattanooga, TN).

Accumulating research evidence strongly suggests that clinicians often underestimate the extent of pathology that results from an inversion ankle sprain, as well as the potential for development of chronic dysfunction and progressive arthritic degeneration. Protection of healing ankle ligaments from excessive tensile loading during stressful physical activities and prevention of recurrent inversion sprains are crucial for long-term preservation of optimal ankle function. Ankle support systems that primarily restrain inward hindfoot motion within the frontal plane, thereby restraining lateral talar tilt, provide a limited degree of ankle ligament protection. Restraint of rotary talocrural and subtalar joint displacements within the transverse plane is crucial for optimal protection of multiple ankle ligaments, since the development of ALRI clearly presents elevated risk for articular cartilage degeneration and disability.

Gary Wilkerson, EdD, ATC, is a tenured professor in the Graduate Athletic Training Program at the University of Tennessee at Chattanooga.

References

1.     Hintermann B, Boss A, Schafer D. Arthroscopic findings in patients with chronic ankle instability. Am J Sports Med 2002;30(3):402-409.

2.     Okuda R, Kinoshita M, Morikawa J, et al. Arthroscopic findings in chronic lateral ankle instability: Do focal chondral lesions influence the results of ligament reconstruction? Am J Sports Med 2005;33(1):35-42.

3.     Taga I, Shino K, Inoue M, et al. Articular cartilage lesions in ankles with lateral ligament injury. An arthroscopic study. Am J Sports Med 1993;21(1):120-127.

4.     Valderrabano V, Hintermann B, Horisberger M, Fung TS. Ligamentous posttraumatic ankle osteoarthritis. Am J Sports Med 2006;34(4):612-620.

5.     Wilkerson GB. Diagnosis and management of lower leg, ankle, foot, and toe injuries. In:  Cummings NH, Stanley-Green S, Higgs P, eds. Perspectives in athletic training. St. Louis: Mosby Elsevier; 2008:213-243.

6.     van Dijk CN, Bossuyt PM, Marti RK. Medial ankle pain after lateral ligament rupture. J Bone Joint Surg Br 1996;78(4):562-567.

7.     Konradsen L, Ravn JB: Ankle instability caused by prolonged peroneal reaction time. Acta Orthop Scand 1990;61(5):388-390.

8.     Rasmussen O, Tovborg-Jensen I. Anterolateral rotational instability in the ankle joint. An experimental study of anterolateral rotational instability, talar tilt, and anterior drawer sign in relation to injuries to the lateral ligaments. Acta Orthop Scand 1981;52(1):99-102.

9.     Wilkerson GB, Alvarez RG. Rotary ankle instability: overview of pathomechanics and prognosis. Athl Ther Today 2010;15(4):4-8.

10.  Freund E, Nyska M, Mann G. The subtalar joint: instability. In: Nyska M, Mann G, eds. The unstable ankle. Champaign, IL: Human Kinetics Publishers; 2002:157-161.

11.  Hertel J, Denegar CR, Monroe MM, Stokes WL. Talocrural and subtalar joint instability after lateral ankle sprain. Med Sci Sports Exerc 1999;31(11):1501-1508.

12.  Hintermann B. Biomechanics of the unstable ankle joint and clinical implications. Med Sci Sports Exerc 1999;31(7 Suppl):S459-S469.

13.  Wilkerson GB, Nitz AJ. Dynamic ankle stability: mechanical and neuromuscular interrelationships. J Sport Rehabil 1994;3(1):43-57.

14.  Wilkerson GB: Treatment of the inversion ankle sprain through synchronous application of focal compression and cold. J Athl Train 1991;26(3):220-237.

15.  Wilkerson GB, Horn-Kingery HM. Treatment of the inversion ankle sprain: comparison of different modes of compression and cryotherapy. J Orthop Sports Phys Ther 1993;17(5):240-246.

16.  Wilkerson GB, Pinerola JJ, Caturano RW. Invertor vs. evertor peak torque and power deficiencies associated with lateral ankle ligament injury. J Orthop Sports Phys Ther 1997;26(2):78-86.

17.  Gibney VP. Sprained ankle: A treatment that involves no loss of time, requires no crutches, and is not attended with an ultimate impairment of function. NY Med J 1895;61:193-197.

18.  Kamiya T, Kura H, Suzuki D, et al. Mechanical stability of the subtalar joint after lateral ligament sectioning and ankle brace application. Am J Sports Med 2009;37(12):2451-2458.

19.  Wilkerson GB. Biomechanical and neuromuscular effects of ankle taping and bracing. J Athl Train 2002;37(4):436-445.

20.  Omori G, Kawakami K, Sakamoto M, et al. The effect of an ankle brace on the 3-dimensional kinematics and tibio-talar contact condition for lateral ankle sprains. Knee Surg Sports Traumatol Arthrosc 2004;12(5):457-462.

21.  Hintermann B, Valderrabano V. The effectiveness of rotational stabilization in the conservative treatment of severe ankle sprains: a long-term investigation. Foot Ankle Surg. 2001;7(4):235-239.

22.  Wilkerson GB. Comparative biomechanical effects of the standard method of ankle taping and a taping method designed to enhance subtalar stability. Am J Sports Med 1991;19(6):588-595.

23.  Wilkerson GB, Kovaleski JE, Meyer MA, Stawitz CE. Effects of the subtalar sling ankle taping technique on combined talocrural-subtalar motions. Foot Ankle Int 2005;26(3):239-246.

24.  Wilkerson GB, Doty JF, Gurchiek DA, Hollis JM. Analysis of rotary ankle instability and taping restraint in a cadaver specimen. Athl Ther Today 2010;15(4):9-12.

25.  Cordova ML, Dorrough JL, Kious K, et al. Prophylactic ankle bracing reduces rearfoot motion during sudden inversion. Scand J Med Sci Sports 2007;17(3):216-222.

26.  Heath DJ. A comparison of taping methods on closed-chain subtalar kinematics [master’s thesis]. Chattanooga, TN: University of Tennessee at Chattanooga; 2005.

27.  Wilkenfeld DA. Effects of ankle support systems on lower extremity kinematics [unpublished master’s research project]. Chattanooga, TN: University of Tennessee at Chattanooga; 2010.

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One Response to Inversion ankle sprains: Seeking optimal support

  1. DAVID ALTIERI, PT,OCS,CSCS says:

    I AM CURRENTLY TREATING A FEMALE DIVISION I TRIPLE JUMPER WITH CAI AND WOULD LIKE TO KNOW HOW I MIGHT BE ABLE TO FIND THE BRACE THAT IS FEATURED IN THE ARTICLE ON ANKLE SPRAINS BY WILKERSON IN THE FEB 2011 MAGAZINE.

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