Alas, I must finish what I started! To recap this cognitive exercise that I started over a year ago:
- Use of unstable surfaces (e.g. wobble boards, Bosu balls) are popular in the rehabilitation of ankle sprains
- I think that these exercises are not very specific to the tasks of everyday life or sports as we are not normally on unstable surfaces
- My hypothesis is that task-specific exercises on stable surfaces are more effective at helping to reduce the risk of recurrent ankle sprains than exercises on unstable surfaces
- I have no direct evidence to support or refute this hypothesis right now, so I am going to explore the research. I have condensed the questions that I had posed in my original post to these three:
- What are some modifiable factors that increase the risk of someone having recurrent ankle sprains? (I want to narrow it to modifiable as these are factors we would be able to change through rehab)
- Which methods are effective at reducing the risk of recurrent ankle sprains? Is one better than others? (Hopefully I can find something comparing stable vs unstable surface training)
- Why are these methods effective and how do they address the modifiable risk factors identified in question 1? If there is a more “optimal” method to use, why is it more effective than others?
This post addresses the first question. Chronic ankle instability (CAI) is characterized by repeated episodes of giving way, perception of ankle joint instability, and recurrent ankle sprains with or without the presence of mechanical laxity (1). As well, people with CAI usually report pain, less function, and difficulty returning to previous levels of activity (1). CAI appears to be a common problem, with one study finding that out of 380 athletes, 563 ankles (out of 380×2 = 760) had been sprained in the past, and 73.5% of these ankles had been sprained at least twice (2). The two most common residual symptoms reported were pain (30.2% of the 380 athletes) and ankle instability (20.4%) (2).
I was initially going to try and find all the primary articles related to this topic but then felt overwhelmed and figured, why repeat what others have already done in a systematic manner? I found three systematic reviews on this topic, which are briefly described below:
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Evidence of sensorimotor deficits in functional ankle instability: a systematic review with meta-analysis by Munn et al, 2010 (3)
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Characteristics of people with recurrent ankle sprains: a systematic review with meta-analysis by Hiller et al, 2011 (4)
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Predictors of chronic ankle instability after an index lateral ankle sprain: a systematic review. by Pourkazemi et al, 2014 (5)
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Purpose
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To identify sensorimotor changes associated with CAI
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To determine whether people with recurrent ankle sprains have specific physical and sensorimotor changes
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To identify predictors of CAI after a lateral ankle sprain
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No. included studies
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53
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55
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4
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Strength
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Able to make pooled estimates of differences in sensorimotor measures between those with CAI and those without
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Same as Munn 2010 (3)
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All studies had a prospective cohort design
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Limitation (with respect to the question I am trying to answer)
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Cross-sectional studies, so the identified differences are not necessarily predictive of future re-sprains
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Same as Munn 2010 (3)
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Limited research on this topic – only 4 studies that met the inclusion criteria, which studied 3 possible predictors (perceived instability, balance, severity of initial sprain)
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To summarize the results of these reviews: there is no clear evidence on modifiable predictors of CAI. However, those with CAI seem to have poorer postural control, reduced concentric ankle inversion strength, and possibly poorer proprioception. See below for more details:
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Potential Modifiable Risk Factor
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Description
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Munn 2010 (3)
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Hiller 2011 (4)
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Pourkazemi 2014 (5)
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Postural control
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Various measures including time to stabilization from a 1-legged jump, Star Excursion Balance Test (SEBT), and postural sway velocity and displacement area in single-leg stance (SLS) under stable or challenging conditions (e.g. eyes closed,mov- ing or inclined surfaces and demi-pointe position)
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For SEBT, data pooled from 4 studies: reach distances were greater for controls compared to subjects with CAI (standardized mean difference (SMD)=0.4, 95% CI: 0.1–0.7, p=0.009) – small effect size
For postural sway displacement during SLS on stable surface, data pooled from 10 studies: postural sway displacement was greater in subjects with CAI compared to healthy control subjects (SMD=0.6 (95% CI: 0.2–1.0, p=0.002) – medium effect size (unclear whether or not it was specific to eyes open/closed)
For time to stabilize after a single-leg jump, data pooled from 4 studies: faster stabilization in healthy control compared to subjects with FAI for medial-lateral (mean difference (MD)=0.6 ms, 95% CI: 0.4–0.8, p<0.0001) and anterior-posterior directions (MD=0.7 ms, 95% CI: 0.4–1.0, p<0.0001)
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For postural sway during SLS on stable surface and the eyes open, data pooled from 9 studies: no statistically significant difference between the groups (SMD=0.4, 95% CI 0.0 to 0.7).
For postural sway during SLS on stable surface with eyes closed, data pooled from 3 studies: increased postural sway in subjects with recurrent sprains compared with controls (SMD=0.9, 95% CI 0.4 to 1.4) – large effect size
For postural sway during SLS on unstable surface with eyes open or closed: increased postural sway in subjects with recurrent sprains compared with controls (SMD=0.5, 95% CI 0.1 to 1.0) – moderate effect size
Authors commented that studies investigating time to stabilization after a vertical jump consistently found increased time to stabilize in anteroposterior direction (no pooling of data done though)
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Data was pooled from 2 studies: perceived instability (as measured by the Cumberland Ankle Instability Tool) and static balance (as measured by number of foot movements during SLS with eyes closed for 30 sec) did not predict re-sprain
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Proprioception (Joint angle position sense)
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Ability to reposition ankle either actively or passively to a given angle/position (typically into inversion and/or plantarflexion)
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For passive JPS, data pooled from 6 studies: subjects with instability had reduced passive JPS (MD=0.7◦, 95% CI: 0.2–1.2◦, p=0.004) compared to healthy controls
For active JPS, data pooled from 10 studies: subjects with instability had reduced active JPS (MD=0.6◦, 95% CI: 0.2–1.0◦, p=0.002) compared to healthy controls
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For all measures of JPS: no significant difference between groups. (see below)
Active inversion JPS (3 studies): SMD=1.2, 95% CI −0.3 to 2.6
Passive inversion JPS (3 studies): SMD=0.2, 95% CI −0.3 to 0.8
Passive mixed inversion/eversion JPS (3 studies): SMD=0.7, 95% CI −0.2 to 1.6
Authors commented that
studies which examined active mixed joint position sense also showed no difference between groups but did not do a pooled analysis.
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n/a
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Kinesthesia (Passive movement joint detection)
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Ability to detect passive movement of ankle in frontal and/or sagittal plane
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Data could not be pooled due to heterogeneity of studies
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n/a
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n/a
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Muscle reaction time
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Time it takes for peroneals to react to an inversion perturbation
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Data pooled from 6 studies:
no difference in reaction time between subjects with CAI and uninjured controls
(MD=7.8 ms, 95% CI:−1.4 to 17.1, p=0.10)
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Data pooled from 4 studies: no difference between groups (MD=3.3 ms, 95% CI −2.3 to 8.9)
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n/a
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Strength
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Primarily ankle inversion and eversion strength measured via peak torque data
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n/a
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For concentric inversion, data pooled from 4 studies: lower peak torque among subjects with CAI compared to controls (SMD=1.1, 95% CI 0.2 to 2.1) – large effect size
For eccentric inversion, concentric and eccentric eversion, no significant effects.
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n/a
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Gait
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n/a
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No pooling was done though authors commented that participants with recurrent ankle sprains had a more inverted ankle position and decreased foot clearance during gait analysis
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n/a
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Other limitations and thoughts:
- Measurements of JPS occur at a much slower speed than the speed at which an ankle would be sprained so these measurements may not be as relevant to mechanisms that lead to an ankle sprain (3)
- It was once thought that the peroneals react in response to forced inversions to prevent ankle sprains (3). However, it is now thought that the time in between forced ankle inversion & a sprain to the lateral ligaments is too short for the peroneals to react and prevent a sprain (3). Thus, it may be more important to look at feed-forward muscle activity (3).
- How much difference does 1 degree make in terms of being able to detect joint position?
- Similarly, how clinically significant are the identified gait differences?
- Lack of gold standard for identifying CAI so participants between studies could vary a lot in their symptomology, making it difficult to compare the studies (3)
- ?Reliability and validity of measures that were used – not mentioned in most of the primary studies (3)
- Inconsistencies between studies when measuring proprioception (3,4) and postural control (3,4,5)
- Studies are needed to look longitudinally at postural sway, time to stabilize after jump, strength, proprioception and whether or not these predict future sprains
Back to my original question: what are some modifiable factors that increase the risk of someone having recurrent ankle sprains? There is not enough prospective evidence to tell us this. However, those with CAI have poorer postural control, reduced concentric ankle inversion strength, and possibly poorer proprioception. Therefore, these factors could potentially be targets for therapy.
The next questions are:
2. Which methods are effective at reducing the risk of recurrent ankle sprains? Is one better than others?
3. Why are these methods effective and how do they affect the modifiable risk factors identified in question 1? If there is a more “optimal” method to use, why is it more effective than others?
References:
- Wikstrom EA, Brown CN. Minimum reporting standards for copers in chronic ankle instability research. Sports Med. 2014 Feb;44(2):251–68.
- Yeung MS, Chan KM, So CH, Yuan WY. An epidemiological survey on ankle sprain. Br J Sports Med. 1994 Jun;28(2):112–6.
- Munn J, Sullivan SJ, Schneiders AG. Evidence of sensorimotor deficits in functional ankle instability: a systematic review with meta-analysis. J Sci Med Sport. 2010 Jan;13(1):2–12.
- Hiller CE, Nightingale EJ, Lin C-WC, Coughlan GF, Caulfield B, Delahunt E. Characteristics of people with recurrent ankle sprains: a systematic review with meta-analysis. Br J Sports Med. 2011 Jan 21;45(8):660–72.
- Pourkazemi F, Hiller CE, Raymond J, Nightingale EJ, Refshauge KM. Predictors of chronic ankle instability after an index lateral ankle sprain: a systematic review. J Sci Med Sport. 2014 Nov;17(6):568–73.
2 comments to this article
Simon
on September 1, 2015 at 5:21 am -
Veronica:
Interesting questions posed and great job summarizing your findings in the charts.
First off, I agree with your hypothesis! I believe that task-specific exercises would be more effective at reducing future risks. My thinking is that these exercises would enable the patient to easily transfer the “gains” to the sport/activity/task that poses the risk. On the other hand, maybe using unstable surfaces makes it easier for the patient to generalize the “gains” to not just one task? Let me know if I’m off, as this is a new topic for me!
Why do you think there is not enough evidence or research about modifiable factors that increase recurrent ankle sprains? When I was reading online, I learned about intrinsic vs extrinsic risk factors. Could the insufficient evidence be due to there being various extrinsic risk factors that make it difficult to measure (e.g. equipment, other players, technique, coaching/instruction, environmental conditions, safety hazards)?
Also, as I was reading about intrinsic risk factors, I started to wonder, is it even possible to have a “gold standard” for identifying CAI? I feel like with so many factors, ankle sprains can vary widely.
I look forward to reading your next blog post!
VeeWong
on September 1, 2015 at 10:55 pm -
Yea I’m not sure at this point – they could both be equally effective! It could be that the ingredient behind rehab is just getting them to use their ankle again, whether that’s with a stable or unstable surface. Stay tuned for part 3 where I look at treatment and its mechanisms :).
There’s probably not a lot of research because it’s not really a costly impairment (compared to whiplash or low back pain anyway) so there’s no huge incentive to research this topic and it’s difficult/more expensive to do longitudinal studies. Good point, extrinsic risk factors are definitely hard to measure! If a treatment study finds that the treatment group has a lower incidence of ankle sprains than the control group though, and the study was well-designed so that people were randomly placed into either group (and therefore the extrinsic risk factors should play a role for participants in both groups equally on average), then I would think that it means something instrinsically has been changed. The question is what are these intrinsic factors? Also I need to look into whether or not these treatment studies actually exist. Stay tuned for part 3 again :p.
With respect to a “gold standard” for identifying CAI, there’s probably no right answer. If researchers had an agreement on what they would define as CAI though, then it would help research to be more comparable. I guess I’d be looking for an agreed-upon standard, and not necessarily a “gold” standard.