Chronic Ankle Instability: Can Orthotics Help?
- Volume 19 - Issue 10 - October 2006
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Podiatric physicians use foot orthotics daily to treat a myriad of lower extremity conditions. Yet while the foot orthotics industry has been growing each year, researchers in the field of biomechanics have begun to challenge previous clinical studies showing that foot orthotics really work. At the same time, third party insurance payors have started questioning the value of foot orthotic therapy on the grounds that this treatment intervention is “experimental” and still without verification of the overall benefit.
Podiatric physicians may have a false sense of confidence that the medical literature can verify the positive treatment outcomes achieved with custom foot orthotics. Further scrutiny will reveal that strong scientific evidence supporting the benefits of foot orthotic therapy is hard to come by.
In their comprehensive review of the medical literature of all studies conducted on custom functional foot orthoses (FOs), Landorf and Keenan concluded: “(While) these papers have included results which are generally quite supportive of FOs, some have found either inconclusive or negative results. Much of the research to date could be improved upon and from this perspective, it is clear that further randomized controlled trials assessing outcomes for specific clinical conditions are necessary.”1
Out of all the pathologies that podiatric physicians can prescribe foot orthoses for, the one condition which has the most compelling scientific evidence justifying orthotic use is the one least likely to be considered for orthotic treatment. This condition is chronic instability of the ankle.
Chronic ankle instability can be due to mechanical or functional causes. Immediately after an acute ankle sprain, ligamentous injury can cause mechanical instability of the ankle, which one can detect with manual testing, stress radiography or via magnetic resonance imaging (MRI). At the same time, most patients after moderate ankle injury will also show evidence of functional instability, which is basically a loss of neuromuscular control over the ankle and subtalar joints. While there is significant scientific evidence that foot orthotics can address both forms of ankle instability, the primary focus of this article will be on the effects of these devices to treat functional instability.
A Closer Look At Postural Control
In 2003, I described essential components of neuromuscular control of the ankle.2 These elements include proprioception, muscle reaction time, muscular strength and postural control. Of all these physiologic functions, the one finding that clinicians commonly see in individuals after acute ankle injury is a loss of postural control.
Postural control is defined as the ability of an individual to maintain his or her center of mass over a single supporting foot. One can measure this in the clinical setting by having the patient perform a modified Rhomberg test. The patient stands on one foot with the arms crossed over the chest and with the eyes closed. A healthy patient should be able to maintain a single leg stance in this situation for at least 10 seconds.
In the research setting, one can measure postural control with special devices that track deviations of center of pressure. Accordingly, one can measure total body sway in terms of velocity and magnitude. This measurement technique is known as stabilometry. In the practice setting, podiatric physicians can measure postural sway with a Matscan® (Tekscan). With the Matscan, one can track migrations in the center of pressure while a patient stands on one foot.