Comparison of Recent Studies on Rehabilitation of Chronic Ankle Instability: A Systematic Review

INTRODUCTION

Ankle sprains occur very frequently during daily and sports activities.^1-3 Chronic ankle instability (CAI) is a common result of an ankle sprain.^4,5 About 73% of individuals who have experienced ankle sprain injuries have recurrent episodes, of which 59% report long-term disability.¹ The common symptoms of CAI include feeling of instability, sensation of giving way, and subsequent sprains.^1,6,7 Additionally, patients with CAI often have defects in functional performance, proprioception, and strength.⁹ The sequential development of CAI has negative health effects, including poor quality of life and early onset osteoarthritis.⁷

Studies before the International Ankle Consortium (IAC) published the standard inclusion criteria for CAI in 2014 have differences in methodological quality, outcome measurement method, and criteria for selecting participants.^7,8,10 Standard inclusion criteria approved by IAC for enrolling patients with heterogeneous conditions of CAI in controlled studies are as follows: 1) a history of at least 1 significant ankle sprain, and the initial sprain must have occurred at least 12 months prior to study enrollment, 2) a history of the previously injured ankle joint “giving way,” recurrently spraining, and/or having “feelings of instability,” and self-reported ankle instability should be confirmed using the relevant cutoff score from a specific questionnaire validated for ankle instability [ankle instability instrument (AII)-answer “yes” to at least 5 yes/no questions, Cumberland ankle instability tool (CAIT) < 24, identification of functional ankle instability (IdFAI) > 11], 3) a general self-reported foot and ankle function questionnaire is recommended to describe the level of disability [foot and ankle ability measure (FAAM) < 90% of activities of daily living (ADL) scale, <80% of sport scale, foot and ankle outcome score (FAOS) < 75% in 3 or more categories].¹⁰ It was recommended to exclude any patients with acute damage to the musculoskeletal structure in other joints of the lower extremity (i.e. sprains, fractures), which impacted joint integrity and function, and who have had at least one day of discontinuation of desired physical activity.¹⁰ Patients with a history of previous surgery for both limb musculoskeletal structures of the lower extremities, such as bones, joint structures, and nerves, were also recommended to be excluded to minimize heterogeneity of chronic ankle instability.¹⁰ Despite the IAC’ s recommendations, it was unclear whether the results of previous systematic reviews accurately reflect the CAI population, according to a 2016 study by Tompson et al.⁷ Subjects’ inclusion criteria varied in many previous studies comparing such things as the characteristics of the CAI population and treatment effects. Additionally, inconsistent terminology and multiple operational definitions of CAI were widespread across the literature.^7,8

There are many factors contributing to CAI that can cause disorders, but this condition is more heterogeneous than many perceive.¹⁰ Knowledge of CAI and the factors contributing to its development is critical to developing targeted interventions and preventing long-term symptoms.⁷ A current review reported strong evidence that contributing factors to CAI were dynamic balance, peroneal reaction time, and eversion strength deficits.⁷ Impaired dynamic balance, delayed peroneal reaction time, and lack of eversion muscle strength make the ankle joint unable to cope with the inversion sprain. Common individual rehabilitation exercises for CAI patients are balance training using unstable support surfaces and strengthening using elastic bands.¹¹ Strengthening intervention using an elastic band helps increase muscle strength and joint position sense, and exercise using an unstable support surface helps reduce muscle latency onset and postural sway.¹¹ However, studies involving CAI patients are rare or have limited evidence.^7,11

Therefore, the purpose of this study was to investigate the results of recent CAI rehabilitation studies with strong contributing factors and whether CAI participants meet the criteria according to IAC recommendations.

METHOD

The protocol of this systematic review was developed using the framework outlined in the guidelines provided by the PRISMA (preferred reporting items for systematic review and meta-analyses) statement.¹² The risk of bias assessment was conducted using a modified version of the quality index checklist.

RESULTS

A total of 58 articles were retrieved. After the title and abstract review, 22 articles underwent full-text review. Following a complementary search and assessment of full manuscripts, 19 articles fulfilled the inclusion criteria (Figure 1). Summaries of the studies were shown in Table 1. All selected studies were conducted in participants who met the IAC recommendations for CAI.^11,14-31 Allowing duplicate counts of intervention type resulted in 15 articles using dynamic balance training (DBT)^11,14-27, 4 articles using strength training (ST)^11,14-16, and 4 articles using mixed type.^28-31 The mixed interventions included functional activity, range of motion (ROM), strength, balance, and neuro-muscular training.^28-31 There were 12 studies comparing the effects of each exercise type before and after exercise.^{11,14-16,20-22,24-27,31} Six studies were conducted on the effects of whole-body vibration, sensory targeted ankle rehabilitation strategies, and unstable surfaces.^{16-18,22,27-28} There was one study comparing the effects of exercise on functionally unstable ankles and functionally stable ankles.²⁹ All studies described a method of random allocation and did random sequence generation (low risk of bias).^11,14-31 In most studies, except for one, outcome assessment was double blinded and complete outcome data was provided (low risk of bias).^11,14-31

Figure 1. Flow chart of search strategy.

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DISCUSSION

The purpose of this study was to systematically review and evaluate the effectiveness of training reflecting the factors contributing to the development of CAI and whether recent studies on CAI selected participants that met the recommendations of the IAC. In all selected studies, the subject selection criteria met IAC recommendations.^11,14-31 The findings of the current review indicated that the intervention of recent studies are mainly concerned with dynamic stability, and it is rare to include reaction time and eversion strength.^11,13-26 DBT improved the ankle strength, balance, functional performance, and self-reported function of CAI patients (Table 1). In ST groups, all of these factors improved (Table 1). However, because strengthening exercise protocols included dorsiflexion, plantar flexion, inversion and eversion, the relevance to eversion strength was not clear.^11,13-15 There was limited evidence whether DBT or ST was more effective in improving function in CAI patients.^11,14-16 There was also controversy about the effectiveness of using an unstable support surface, vibration, or sensory-targeted ankle rehabilitation strategies (mobilization, massage, and stretching) in the balance exercise protocol.^{17-19,22,23,31}

In the selected studies, CAIT, FAAM, global rating of function (GRF), star excursion balance test (SEBT), foot lift test, hop test, kinetics, and kinematic were used dependent variables.^{11, 14-18,20,22-24,26-31} As an instability measurement, SEBT, foot lift test, hop test, kinetics, and kinematics provided valid, objective, and quantifiable data to evaluate the balance ability of the ankle joint. CAIT, FAAM, and GRF as subjective data were also used in a validated ankle instability specific questionnaire to confirm self-reported ankle instability.¹⁰ The subjective ‘feelings of instability’ are also important factors that limit patients’ functional activity and reduce their quality of life.¹¹ The CAI populations feel that an unstable ankle joint is usually associated with the fear of sustaining an acute ligament sprain during ADL and sporting activities.¹⁰ Health care clinicians should aim to reduce fear-avoidance as well as symptoms and dysfunction to improve the functioning of CAI populations. According to the results of this study, several weeks of DBT, ST, and progressively therapeutic exercise will help improve balance, strength, and self-efficacy in CAI patients.^11,14-31 Previous studies have shown that a significant number of CAI patients are experiencing recurrent episodes. According to a study by Wright et al., about 43% of participants maintained a decrease in ‘giving way (the regular occurrence of uncontrolled and unpredictable episodes of excessive inversion of the rear foot)’ after 6 months post-intervention.¹⁴ However, as most of the selected studies measured intervention effectiveness immediately after exercise, the long-term effects were not known for certain.^{11,5-17,19,20,22-29,31}

The selected studies were not homogeneous in exercise method, intervention period, and outcome variables, excluding the criteria for selecting CAI participants. Therefore, there is a limitation as comparison using statistical analysis cannot be performed. In addition, in some studies, the similarity between the measurement method and the DBT method used as an outcome variable could not be completely excluded. Therefore, in future studies, it will be necessary to evaluate methodological bias and meta-analysis of articles with research homogeneity.

CONCLUSIONS

This study found that DBT, ST, and therapeutic exercise improved the ankle strength, balance, functional performance, and self-reported function of CAI patients. There is limited evidence on which exercise is most effective in improving function in CAI patients.