Not all patients with chronic ankle instability develop ankle osteoarthritis, but evidence suggests the two conditions are related, which in turn suggests that ankle sprain prevention and management could help reduce ankle replacement rates.
By Larry Hand
In 1979, Kevin D. Harrington, MD, an orthopedic surgeon at the University of California at San Francisco, hypothesized that persistent lateral ankle ligament instability causes unbalanced loading of the medial joint, which could in turn lead to the development of osteoarthritis (OA) of the ankle.1 His paper, published in the Journal of Bone and Joint Surgery (JBJS), became a foundation for subsequent research that has, paper by paper, strengthened the link between chronic ankle instability (CAI) and ankle OA. Researchers and practitioners have sought treatments and interventions that might ease the burden of CAI and, further, prevent OA.
CAI can develop after an ankle sprain, the most common injury among people who participate in sports of any kind.2 CAI manifests as a feeling of the ankle giving away and can lead to multiple subsequent sprains. A number of published studies suggest the greatest risk factor for ankle sprain is a previous ankle sprain.3
Although an ankle sprain might be perceived by some as a minor injury, it is in fact a major public health problem. A 2010 paper in JBJS found that more than 3.1 million ankle sprains occurred in the US between 2002 and 2006,4 and the medical costs of ankle sprains could amount to more than $2 billion a year.5
About 1% of the world’s adult population suffers from ankle OA, and in a 2009 study of 309 patients (406 ankles) by Swiss researchers, 78% of them were postraumatic ankle OA cases, most often occurring after ankle fracture, but also resulting from ligament injury.6
It makes sense that reducing the risk of ankle OA could be a matter of reducing the risk of ankle sprains, according to Cathleen Brown, PhD, ATC, codirector of the Biomechanics Laboratory in the Department of Kinesiology at the University of Georgia in Athens.
“We do not know for sure, but more sprains increase the risk of OA, so decreasing the number of sprains experienced would be a goal. The number of sprains can be reduced in people with CAI through ankle bracing and ankle rehabilitation,” Brown explained.
Evidence for a link
In his 1979 study, Harrington evaluated the records of 36 patients who had experienced lateral ankle instability (LAI) for at least 10 years and who underwent reconstruction of the lateral ankle ligaments. Four patients also had total ankle replacements. Upon inversion stress examination by Harrington, all 36 patients had inversion instability and a palpable opening of the lateral tibiotalar joint space. Of the 36 patients, 30 (83%) had experienced joint pain indicative of degenerative arthritis prior to surgery but did not experience further ankle instability symptoms after treatment.
Researchers at the Human Performance Laboratory & Orthopaedic Department at the University of Calgary in Alberta, Canada, concluded in 2006 in the American Journal of Sports Medicine (AJSM)7 that the primary causes of ligamentous post-traumatic ankle OA are lateral ankle sprains from sports participation. They examined the records of 30 patients (33 ankles) from a cohort of 247 ankle OA patients. Of the 30 patients, 85% had experienced lateral ankle ligament injury and 15% had experienced medial and medial-lateral ligament injury, with a mean latency of just over 34 years to OA. The authors concluded, “Lateral ankle sprains in sports are the main cause of ligamentous posttraumatic ankle osteoarthritis and correlate with varus malalignment.”
Duke University researchers, in a 2009 AJSM paper, concluded that altered kinematics in the anterior talofibular ligament (ATFL) could be a link between ankle instability and OA.8 They used magnetic resonance imaging (MRI) and fluoroscopy to evaluate the experiences of nine patients with ATFL injuries. Some of those same researchers, in a 2010 paper in the Journal of Biomechanics,9 concluded that one way chronic LAI may contribute to ankle OA is shifting anteromedially the peak contact strain of the cartilage. They also used MRI and fluoroscopy to corroborate clinical findings of cartilage strains in seven patients with chronic LAI who experienced damage to the ATFL and calcaneofibular ligament.
More recently, in the October issue of Foot & Ankle Specialist, researchers from the Kaiser San Francisco Bay Area Foot and Ankle Residency in Oakland, CA, contributed more possible evidence that chronic LAI may “predispose patients to osteoarthritis.”10 They determined that of 28 LAI patients who underwent ankle arthroscopy between 2004 and 2008, all experienced inflammation of the synovial membrane, seven had talar cartilage fibrillation, and four experienced cartilage defect, among other effects.
A research trend
“Post-traumatic ankle osteoarthritis is really an up-and-coming trend that’s becoming more commonly investigated—which is a good thing,” said Patrick McKeon, PhD, ATC, assistant professor in the Division of Athletic Training at the University of Kentucky College of Health Sciences in Lexington.
Much of the increased research focus on ankle OA is related to ankle replacement surgery, since patients scheduled for ankle arthroplasty typically have been diagnosed with ankle OA. As studies of risk factors contributing to ankle OA have become more common, so have studies of the technical and clinical success of ankle replacement procedures, McKeon said, although whether the two trends are related is unclear.
“Ankle replacements are not as popular as hip and knee replacements, but technical advances have shown promise for them as a viable treatment option for end-stage ankle osteoarthritis,” McKeon added.
A literature review by Duke University researchers in the August issue of JBJS pegged survivorship for total arthroplasty implants at 70% to 98% after three to six years and 80% to 95% after eight to 12 years, with most patients being able to return to recreational sports activity afterward.11 An analysis of ankle replacements in a Swedish register between 1993 and 2010, reported last year in Acta Orthopaedica,12 found that while the survival rate for 780 implanted prostheses declined from 81% at five years to 69% at 10 years, results slowly began to improve in the latter years of the study and that improvements in technology and better patient selection should improve survivorship.
Another literature review in 2010 in Clinical Orthopaedics & Related Research found that almost 10% of ankle replacements needed revisions after an average of just over five years, that improvement in ankle range of motion was “relatively small,” and that residual pain afterward was “relatively frequent.”13 But a more recent paper from Duke, published in the January 4 issue of JBJS, found that 82 patients who underwent the Scandinavian Total Ankle Replacement (STAR) arthroplasty between July 1998 and February 2008 experienced “significant improvement” in function, quality of life, and pain.14
Evidence for intervention
Many efforts in the past several years have been aimed at finding ways to prevent progression of ankle instability and possibly OA. A number of published papers have covered the topics of bracing and taping of ankles, as well as rehabilitation interventions such as balance control.
External support. The most recent Cochrane review on ankle sprain prevention, published in 2001, concluded that external ankle support devices offer significant reductions in risk of ankle sprains, but more so for recurrent than fresh sprains.15 The forms of support included orthoses, braces, high-top shoes, boot inserts, and taping. The reviewers wrote that the evidence points to beneficial effects of orthoses and braces for high-activity sports but that any prophylactic benefit should be balanced with the risk of injury, the cost of the support, “and for some, the possible or perceived loss of performance.” However, that review has since been designated as “withdrawn,” indicating the need for an update.
More recently, in 2010, researchers at the EMGO Institute for Health and Care Research in Amsterdam, The Netherlands, analyzed 24 published studies and concluded that taping, bracing, and neuromuscular training were effective for preventing recurrent ankle sprains in athletes.16
“Wearing an ankle brace can decrease the number of sprains,” Brown Crowell of the University of Georgia said. “There is no evidence that braces are harmful to the joint. Individuals with ankle instability should ask a rehabilitation professional for the brace that best fits their needs.”
Balance control. Balance control interventions have been the focus of a number of researchers in the past few years.
“We’ve seen good things come out of balance training,” McKeon said.
In a study published in Medicine & Science in Sports & Exercise in 2008,17 McKeon and colleagues randomly assigned 31 young adult patients with CAI to an intervention group or to a control group. While the control group maintained activity levels consistent with the prestudy period, the intervention group went through 12 supervised balance training exercises for four weeks that concentrated on stabilization in a single limb stance after landing from a hop. The intervention group was associated with significant improvements in function and in static and dynamic postural control.
“We believe that progressive balance training significantly enhanced the ability of the sensorimotor system to overcome the sensorimotor constraints related to CAI,” McKeon and colleagues wrote in the study.
Earlier, researchers at Shenandoah University in Winchester, VA, reported on another four-week rehabilitation study in the Journal of Orthopaedic & Sports Physical Therapy.18 Their program addressed range of motion, strength, neuromuscular control, and function. The 16 CAI patients in the rehabilitation group showed greater improvements from baseline on the star excursion balance test reach tasks and on functional index scores than the 13 CAI patients in the control group.
University of North Carolina at Charlotte researchers conducted a meta-analysis on balance training and CAI and concluded that balance training improves postural control after acute and lateral ankle trauma, but further research is needed to clarify optimal types and intensity.19
Strengthening exercises may also be indicated to address muscle atrophy in patients with ankle OA. A study from the University of Calgary, published in the December 2006 issue of the Journal of Orthopaedic Research, found that 15 patients with ankle OA had smaller mean calf circumference, dorsiflexion and plantar flexion torque, and lower leg muscle electromyographic frequency and intensity than 15 matched normal individuals.20
Addressing obesity. Weight-loss programs could also be combined with other preventive measures to help delay progression from CAI to ankle OA.
“When you have ankle instability, you’re putting abnormal stress on the obvious osseous and ligamentous structures of the ankle and foot, creating poor alignment,” said Curt Bertram, CO, national orthotics specialist and general manager with the Hanger Orthopedic Group in Milwaukee, WI. “As a result of this poor alignment from the instability, the patient is placing abnormal wear on the joint and thus developing osteoarthritis prematurely through abnormal wear and tear. As an orthotist, the best thing to do is correct instability with an orthosis. The greater your mass, the greater force you’re putting on the ankles. Severe instability combined with obesity and poor health certainly contributes to a higher risk for developing ankle OA.”
A 2007 article in Foot and Ankle International demonstrated an association between obesity and ankle OA.21 Researchers at the West Coast Sports Medicine Foundation in Manhattan Beach, CA, evaluated the records of 1411 patients seen for foot and ankle problems. They compared records of complaints from people who were of normal weight or underweight to complaints from overweight and obese individuals.
Overweight or obese patients were more likely, although not significantly, to develop OA. According to the researchers, osteoarthritis can be secondary to overuse and stress on the soft tissues and joints, which can result from heavier body weights.
Functional vs mechanical instability
Even after rehabilitation, some patients might still require surgery, and that may be due to differences between functional and mechanical instabilities. McKeon and colleagues explored these differences in a 2009 study published in Clinical Rehabilitation, in which 29 patients were assigned to either a balance training group or a control group.22
“While we found improvements in postural control, improvements in function, and improvements in terms of these individuals saying that they were functionally better after undergoing rehabilitation, we found no change in their ligamentous laxity profile,” McKeon said. “They still had the same behavior of the ligaments, but they felt more stable now. So we changed them functionally but we didn’t change them mechanically.”
If traditional rehabilitation approaches can’t address mechanical instabilities, surgery may be the only remaining option for those patients.
“On the functional side, we know that we can potentially improve improper biomechanics as well as improper or impaired postural control and sensorimotor control through rehabilitation,” McKeon said. “We might not be able to alter the mechanical side by any means other than surgical intervention.”
The importance of timing
One Dutch study,23 although published in 2004, still stands as a reminder that timing may be important, McKeon said. The study analyzed one year of volleyball injuries in a Dutch population for one season. Ankle sprains accounted for 41 of 100 injuries. However, said McKeon, the first six months after injury were the most critical in avoiding recurrent sprains, and if players had not sustained a recurrent injury 12 months later, their risk of suffering another sprain dropped down to that of people who had never had a sprain.
“It might actually be,” McKeon said, “that if we can get an individual who sprained an ankle out to a full year without having a recurrent episode, potentially we can help them to decrease their risk of ankle instability and osteoarthritis, too.”
Larry Hand is a writer in Massachusetts.
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