SLR - September 2016 - Michael Matthews

Recovery from a First-Time Lateral Ankle Sprain and the Predictors of Chronic Ankle Instability: A Prospective Cohort Analysis

Reference: Doherty C, Bleakley C, Hertel J, Caulfield B, Ryan J, Delahunt E. Recovery from a First-Time Lateral Ankle Sprain and the Predictors of Chronic Ankle Instability: A Prospective Cohort Analysis. Am J Sports Med. 2016 Apr; 44(4): 995–1003.

Scientific Literature Review

Reviewed By: Michael Matthews, DPM
Residency Program: Mount Auburn Hospital

Podiatric Relevance: Lateral ankle sprains are in many cases cited as the most common traumatic injury seen in lower extremity practice. The treatment of such injuries in the acute setting is well established, but no strict guidelines for long-term treatment are agreed upon in the literature. Lateral ankle injuries can be debilitating and in some cases can manifest in chronic ankle instability in the long-term. The consensus on which of these injuries require surgical intervention and when the optimal timeframe to perform such intervention is not consistent in the literature. In the last decade, research into these injuries has come to incorporate the belief in “articular deafferentiation” at the ankle joint as a result of a lateral ankle sprain. Such deafferentiation has been hypothesized to interfere with the nervous system’s ability to exploit motor control redundancies, thereby helping to prevent further injuries. The clinical significance of such research could be valuable in its potential to identify certain clinical biomechanical tests that could be predictive of future chronic ankle instability. Identification of such clinical tests could allow providers to identify patients significantly at risk for chronic ankle instability, allowing them to surgically intervene sooner to prevent further injury. As such, the primary aim of the paper under review was to identify biomechanical deficits appreciated at two weeks and six months post injury that would be predictive of chronic ankle instability at the one-year mark.

Methods: A level II prospective cohort study was performed. Primary outcomes consisted of performance with five biomechanical tasks with subvariations: single limb stance, Star Excursion Balance Test, single leg drop landing, drop vertical jump and walking gait. Secondary outcomes were the results of patient-reported outcome measures, those being the Cumberland Ankle Instability Tool and the Foot and Ankle Ability Measure. Primary and secondary outcomes underwent logistical regression analysis to determine if they were associated with either (1) chronic ankle instability (CAI) or (2) lateral ankle sprain coper (LAS coper) at the study end point of one year follow-up. Seventy patients were prospectively enrolled over an 18-month period from a single university-affiliated hospital emergency department within two weeks of sustaining an acute first-time lateral ankle sprain injury. Exclusion criteria included previous history of lateral ankle sprain, previous lower extremity injury in the last six months, history of ankle fracture, history of lower extremity surgery, history of neurovascular compromise. Patients were evaluated at the University College Dublin biomechanics laboratory at three time points: two weeks post injury, six months after injury and one year after injury. Primary and secondary outcomes underwent univariate statistical analysis (the Pearson r test) to evaluate their association with the final outcome of CAI or LAS coper. Significance level was defined as P < .05.  

Results: Complete data sets were available for 70 of the initially enrolled 82 patients at one year. Twenty-eight patients (40 percent) were diagnosed with having CAI, and 42 patients (60 percent) as LAS copers. Sixty percent of patients participated in rehabilitation services, where 40 percent did not; however, via a chi squared test, no association between rehab and outcome was appreciated. At the two-week mark, a patient’s inability to perform a single-leg drop landing and a drop vertical jump were found to be statistically significant (P=0.004) with respect to the development of CAI at the one-year point. At the six-month mark, deficits with regard to reach distances and the sagittal plane joint positions at the hip, knee and ankle during the posterior reach segment of the Star Excursion Balance Test had a statistically significant (P <0.001) association with development of CAI. Lower patient-reported outcome scores on the CAIT and FAAM at the six-month mark also had a statistically significant correlation to the development of CAI.  

Conclusions: The significance of this study was its ability to appreciate a number of clinical tests that could be performed close to the time of injury that were significantly correlated with the eventual development of CAI. This study was also unique in being the first of its kind to attempt to correlate patient-reported outcome scores with long-term sequela from a lateral ankle sprain. It is also significant in that it presents an entirely different clinical metric at the six-month mark for which to predict a negative long-term outcome in patients with first-time LAS.  

These findings could be valuable to providers in the clinical setting to expedite the clinical and radiographic workup for surgical repair of lateral ankle injuries. If a clinician had data available at the two-week mark that was strongly predictive of CAI, advanced imaging and surgical intervention could be indicated in a shorter timeframe, thereby decreasing the patient’s overall morbidity and decreasing the time for their return to normal activity. One of the major drawbacks of this study was that the factors that were appreciated at the six-month mark to be predictors of CAI require a biomechanical laboratory to be appreciated. Another significant deficit in the study is that while decreased scores in the CAIT and FAAM were shown to be associated with CAI, no parameters were established and the findings were only with respect to relative values.

Additionally, these findings are also significant in the rehabilitation realm, as they support the theory that kinematics not just with respect to the ankle, but rather the whole lower extremity, is key to rehabilitation.  

In conclusion, this study produced clinical tests that could accelerate the clinical and surgical treatment of lateral ankle sprains, thereby decreasing patient morbidity and decrease time to activity. It also supported the use of a more global approach to rehab rather than foot and ankle-specific treatment.  

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