How To Manage Lateral Ankle Sprains

By John Hester, DPM, PT

Ankle sprains occur at a rate of roughly 25,000 per day nationwide, account for 10 percent of all emergency department visits and represent 25 percent of all sports injuries (and 25 percent of all time lost from sports).1-3 Ankle sprains are particularly prevalent in sports such as basketball and soccer with ankle sprains representing approximately 50 percent of all basketball injuries and 30 percent of all soccer injuries.4 Yet an estimated 55 percent of people who experience an ankle sprain will not seek professional treatment.5 This is unfortunate since most of these individuals are young athletes with good rehab potential. It’s also important to emphasize that ankle sprains, specifically lateral ankle sprains without associated injury, are significant injuries. Consider that 40 percent of those with acute lateral ankle sprains will develop chronic symptoms of ankle dysfunction such as pain, swelling, recurrent injury and having the ankle give way. These chronic symptoms are most often due to functional instability and less frequently to mechanical instability.1,3,4,6 Furthermore, the severity of functional instability has been shown to be unrelated to the grade/severity of the initial injury. In his 1998 study of West Point military cadets, Gerber found that people with Grade I lateral ankle sprains developed chronic symptoms just as frequently as Grade II and III injuries.7 This evidence points to the fact that even mild sprains in athletes deserve our attention. Despite the high incidence of these injuries and the hundreds of articles published on them, there continues to be great variation in diagnosis and treatment strategies. This is partly due to the number of medical specialties and disciplines that treat ankle sprains. They include emergency department physicians, primary care physicians, physician’s assistants, nurse practitioners, physical therapists, athletic trainers, chiropractors, osteopaths, orthopedists and podiatrists. Even if we’re all reading the same literature, there is a lack of evidence-based management strategies. Indeed, there are relatively few high quality randomized, controlled trials relating to this topic. Moreover, there is a lack of proven measures to monitor treatment response. While most clinicians and researchers continue to rely on physical measures (strength, range-of-motion, swelling and joint laxity), recent studies suggest they are not as important as functional measures, particularly when treating athletes. What You Should Know About The Risk Factors A look at risk factors for ankle sprains reveals a lot of conflicting data in the literature. However, McKay recently found some interesting trends.5 In a prospective study of over 10,000 recreational, amateur and elite basketball players in Australia, the largest study of its kind, McKay found a history of previous sprain was the greatest predictor of lateral ankle sprain with these patients having a five times greater risk for the sprain. Interestingly, the second greatest predictor was the presence of an air cell in the heel of the basketball shoe (4.3 times greater risk). The third greatest predictor was failure to stretch (2.6 times greater risk). Beynnon recently published a review of prospective studies that looked at risk factors for ankle sprain.8 The factors that did not predict a higher risk of sprain were particularly interesting. These factors included gender, general laxity and anatomic foot type. Assessing And Grading The Severity Of Ankle Sprains When discussing the diagnostic approach to lateral ankle sprains (without associated injury), it’s important to note the initial exam is often unreliable due to pain, swelling and guarding. Van Dijk found that a delayed physical exam on the fifth day actually compared favorably to arthrography, radiography, sonography and MRI in diagnosing the grade/severity of lateral ankle sprains.9 He concluded, as most authors and clinicians would agree, that stress films are not indicated for acute sprains in that findings are unlikely to change treatment protocol. These ancillary studies are more appropriately utilized for chronic ankle instability and research purposes. The West Point and AAOS grading systems are the most commonly used assessment tools for lateral ankle sprains and can serve as a helpful guide to treatment interventions. However, keep in mind that these systems do have significant limitations. They are somewhat inexact and are largely dependent on subjective interpretation. They show large variability among experienced observers. They do not predict outcome and, in fact, there are no studies to support the validity of these systems as they relate to prognosis. Traditional grading systems also fail to take into account neuromuscular/proprioceptive deficits, which are now believed to be more important than traditional physical measures. How To Distinguish Between Functional And Mechanical Instability As noted above, chronic symptoms of lateral ankle sprains are more often caused by functional instability than mechanical instability. Mechanical instability is a loss of structural integrity of the ankle joint ligaments following injury, resulting in joint laxity. This represents an impairment of the “static defense mechanism,” as Konradsen referred to it.10 Yet a number of studies have shown that a high percentage of athletes who complain of recurrent lateral ankle instability do not demonstrate joint laxity on physical exam or stress films. Other studies have shown joint laxity itself does not predict the presence or severity of chronic ankle instability. Functional instability, on the other hand, can be characterized by chronic pain, swelling, giving way or recurrent injury in the presence or absence of mechanical instability. This is believed to be due to damage of the mechanoreceptors in the capsule and ligamentous tissue, as Freeman described, as well as the muscle/tendon/skin tissue, as Konradsen has added more recently.6,11 This results in deafferentiation of the ankle and subsequent proprioceptive deficit. More recently, functional instability has been defined as recurrent joint instability or a subjective sense of instability due to any neuromuscular deficit. Functional instability has been shown to be independent of the degree/severity of the initial injury and it may exist with or without mechanical instability. What The Literature Reveals About Other Proposed Causes Of Functional Instability Although proprioceptive deficit would appear to be a key factor in functional instability, consider other potential causes that have been proposed as contributing factors. With this in mind, let’s take a closer look at what the studies have suggested. Mechanical instability. Although it may be present, most patients with functional instability don’t demonstrate mechanical instability. Vaes recently reported only 35 percent of 117 functionally unstable ankles demonstrated mechanical instability.12 This percentage is consistent with similar, previously reported studies which show joint laxity itself does not predict the presence/severity of functional instability.13,14 These studies support the notion that mechanical instability alone is of little clinical significance. Peroneal weakness. This would not appear to be a major factor in acute/chronic ankle instability. Following an acute sprain, peroneal strength has been shown to normalize by six weeks (and early as three weeks).6 Other studies have shown no evidence of peroneal weakness in patients with chronic functional instability and that peroneal weakness holds no predictive value for sprains in college basketball players.3,15 In fact, recent studies have suggested that weak invertors may be a contributing factor to functional instability.16 When you consider, however, that the peroneals are capable of generating a five-fold greater eversion moment about the ankle than any tape or brace combination, they certainly deserve our attention during rehabilitation. Delayed reaction time. When it comes to the concept of delayed peroneal reaction time being a cause of functional instability, there is conflicting data in the literature. It has not been definitively determined as to whether these delays exist in acute or chronic ankle instability. A more interesting and fundamental issue is whether the peroneals can react fast enough to protect the ankle from sudden inversion stress. Konradsen found it took 80 msec to passively invert the ankle 30 degrees and found no measurable peroneal muscle force until 126 msec.6 This suggests the peroneals cannot react quickly enough to prevent ligament injury even in healthy subjects. In a more recent study, using a larger degree of displacement, Vaes found it took 110 msec to passively invert 50 degrees and found a measurable motor response at 80 msec.17 This suggests at least the start of a protective muscle contraction is possible. Keep in mind, however, that these data were generated in an experimental setting using a trap door in static stance. They fail to take into account the anticipatory “pre-activation” that occurs with dynamic activities (such as running or jumping) prior to foot strike. Subtalar joint instability. This condition is present in an estimated 10 to 25 percent of patients with functional instability, but the true incidence is unknown due to difficulty in objectively identifying it. Traditionally, physicians identified subtalar instability radiographically with modified Broden stress views. However, Louwerens found these views result in a wide range of displacement and found no correlation with functional instability.19 More recently, Sibrandij looked at patients with positive modified Broden stress films and evaluated them with helical computed tomography (CT).20 He found none of them demonstrated subtalar tilt on CT and concluded these stress views were not valid for assessing subtalar joint instability. It can be concluded that little is known about the relationship between subtalar joint instability and functional instability. With no valid clinical or radiological test currently available, subtalar instability remains essentially a diagnosis of exclusion. Why Proprioceptive Deficit Is An Important Factor Proprioceptive deficit appears to be the most important contributing factor to functional instability of the ankle. Its presence has been extensively documented for acute sprains and chronic lateral ankle instability.11,13,21-23 It’s also important to note that proprioceptive deficits are reversible and and can be corrected with training. Tropp demonstrated that disc training in soccer players with functional instability decreased the injury rate to the point where it was equal to the rate of those with no previous history and, in fact, was as effective as bracing.13 It has been shown that using proprioceptive/balance training programs after a lateral ankle sprain has resulted in a twofold decrease in the risk of recurrent sprain. While no potential contributing factor should be overlooked, proprioceptive deficit is the key factor when addressing functional instability of the ankle. Regaining proprioceptive/neuromuscular control after a lateral ankle sprain is a necessary prerequisite for an athlete wishing to return to his or her sport. What Studies Say About Grade III Lateral Ankle Sprains Treatment options for lateral ankle sprains in athletes have traditionally been broken down into three categories: immobilization/casting, functional treatment/early mobilization and surgical repair. The preferred treatment has undergone an evolution over the years. Immobilization/casting was common through the ‘70s and into the mid-‘80s when surgical repair gained popularity. Currently, functional treatment/early mobilization is the most widely accepted approach. In fact, there is universal agreement that functional treatment is the best approach for grade I and II lateral ankle sprains. Treatment of grade III sprains has generated a little more controversy over the years. Let’s take a closer look at the three potential options for treating grade III lateral ankle sprains in athletes. Functional treatment versus immobilization. When comparing functional treatment to immobilization, virtually every study has found functional treatment superior on all parameters and across all grades of lateral ankle sprain. This holds true when looking at return to work, return to sports, pain, swelling, range-of-motion, objective/subjective stability, recurrence rates and cost. In addition, functional treatment/early mobilization avoids the degenerative and de-conditioning effects of immobilization. There are essentially no demonstrable beneficial effects of immobilization when it comes to lateral ankle sprains. Many have concluded that we should abandon immobilization when it comes to treating any grade of lateral ankle sprain in athletes, except for short periods of time in select patients. Functional treatment versus surgery. The comparison of functional treatment to surgery has not been as clear-cut over the years. From the 1960s to the mid-‘80s, multiple studies reported favorable outcomes with operative repair of acute sprains. However, many of these studies were non-randomized, non-controlled trials, which made it difficult to compare surgical repair to functional treatment. The ‘90s saw an influx of randomized, controlled trials and meta-analyses that clearly favored functional treatment over operative repair, seemingly putting the matter to rest.14,24-26 However, things have become less clear in this decade. Pijnenburg recently published a meta-analysis, as well as results from a randomized, prospective trial, comparing functional treatment to operative repair.27,28 He found primary repair resulted in better long-term outcomes with regard to residual pain, recurrent sprains and stability when compared to functional treatment. (Note that the study authors themselves questioned whether surgery should be the treatment of choice based on potential risks, complications and cost.) Even more recently, Kerkhoffs (in a 2002 Cochranes Review) found insufficient evidence from randomized, controlled trials to determine the relative effectiveness of surgical and conservative treatment for acute lateral ankle sprains.29 Despite these recent interesting studies, functional treatment is still the treatment of choice for all grades of lateral ankle sprain in athletes. Functional treatment provides the fastest recovery of ankle joint mobility with the quickest return to sport. It does not compromise late mechanical or functional stability. One may perform delayed ligament repair (Brostrom-Gould) years later, if necessary, with good results. Functional treatment is also essentially free of complications. Most comparative studies define functional treatment as brace-only. We know today’s athletes benefit from the best available, comprehensive rehabilitation techniques, likely making the comparative results of functional treatment even more favorable. Surgical Repair: A Rarely Used Treatment Option The functional treatment approach holds true when looking at practice patterns in elite, amateur and professional sports programs. Consider the number of operative repairs of acute lateral ankle sprains in select groups of elite athletes in recent years. • Boston Celtics: none in the last 17 years. • NBA: Four in the last 11 years. (League-wide, the NBA averages approximately 100 sprains per season which result in at least one missed game or practice.)29 • Boston College basketball: none in the last 10 years. • Harvard University athletics: one in the last 10 years. • Stanford University basketball: none in the last 10 years. Although these data were generated from an informal survey, they do reflect the current state of practice for high-level athletes with acute lateral ankle sprains. So when is operative repair on an acute lateral ankle sprain indicated in an athlete? In the absence of associated injury, surgery is almost never indicated. With rare exceptions, randomized controlled trials, literature reviews and meta-analyses over the past 10 years have shown functional treatment to be at least equal to operative repair and, in most cases, superior. Keep in mind that today’s athletes have far more sophisticated rehabilitation resources and programs available to them than those described in comparative studies. This would presumably generate even more support for functional treatment/early mobilization in the athletic population. One might argue that exceptions to the conservative approach would be the presence of a massive hematoma requiring decompression or an acute-on-chronic injury in an athlete who has a history of instability refractory to comprehensive functional treatment. In Conclusion Functional treatment/early mobilization is the treatment of choice for acute lateral ankle sprains in athletes. The goal of rehabilitation is to restore the athlete to his or her previous level of function in the shortest period of time or so-called “accelerated” rehab. This typically requires a comprehensive, supervised, functionally-oriented program under the care of a physical therapist or athletic trainer. Keep in mind that athletes require complete functional restoration of strength, power, flexibility and cardiovascular endurance. It is particularly important to address proprioceptive and neuromuscular deficits in order to help prevent recurrent injury. Also recognize that proprioceptive rehabilitation has evolved from simply addressing joint position/motion sense to the broader context of neuromuscular control. Though we may not be directly rehabbing these patients, it’s certainly important to be familiar with the principles and advantages of the “functional” approach. Dr. Hester is a Fellow of the American College of Foot and Ankle Surgeons. He is in private practice with Sports Medicine Associates and Pro Sports Orthopedics, and is the team podiatrist for the Boston Celtics.



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