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To identify the predictors of chronic ankle instability after an index lateral ankle sprain.
Design
Systematic review.
Methods
The databases of MEDLINE, CINAHL, AMED, Scopus, SPORTDiscus, Embase, Web of Science, PubMed, PEDro, and Cochrane Register of Clinical Trials were searched from the earliest record until May 2013. Prospective studies investigating any potential intrinsic predictors of chronic ankle instability after an index ankle sprain were included. Eligible studies had a prospective design (follow-up of at least three months), participants of any age with an index ankle sprain, and had assessed ongoing impairments associated with chronic ankle instability. Eligible studies were screened and data extracted by two independent reviewers.
Results
Four studies were included. Three potential predictors of chronic ankle instability, i.e., postural control, perceived instability, and severity of the index sprain, were investigated. Decreased postural control measured by number of foot lifts during single-leg stance with eyes closed and perceived instability measured by Cumberland Ankle Instability Tool were not predictors of chronic ankle instability. While the results of one study showed that the severity of the initial sprain was a predictor of re-sprain, another study did not.
Conclusions
Of the three investigated potential predictors of chronic ankle instability after an index ankle sprain, only severity of initial sprain (grade II) predicted re-sprain. However, concerns about validity of the grading system suggest that these findings should be interpreted with caution.
Population based epidemiology of ankle sprains attending accident and emergency units in the West Midlands of England, and a survey of UK practice for severe ankle sprains.
The most common residual impairments include re-sprain, perceived instability and episodes of giving way (also referred to as functional instability), joint laxity (also referred to as mechanical instability), pain, swelling, a feeling of weakness and subsequently reduced level of physical activity.
however, prevention is only possible if people at risk of developing CAI can be identified. That is, to determine the most effective prevention strategy it is essential to understand the underlying causes leading to CAI, and the factors increasing the risk of CAI.
History of a previous sprain is the most frequently reported risk factor for lateral sprain.
Basketball players with history of an ankle sprain were found to be five times more likely to re-sprain, although the reasons for the increased risk are unknown.
suggested that ankle sprains cause various sensorimotor deficits that can lead to instability, and that the presence of instability increases the risk of further sprain. Many studies have investigated this theory, but the findings are inconsistent.
There are few studies of predictors of CAI, however two systematic reviews have evaluated closely related questions and some information can be derived from their findings. One systematic review found decreased dorsiflexion range of motion to be a strong predictor of lateral ankle sprain.
athletes competing at a higher level of competition were at greater risk of persisting impairments after an acute sprain than athletes competing at lower levels. Severity of pain, number of re-sprains, as well as level of perceived instability and self-reported recovery after an acute lateral ankle sprain were found to be independent of the severity of the initial sprain. Furthermore, men were reported to have a greater risk of developing residual impairments than women. However, not all studies included in these two systematic reviews investigated the risk factors contributing to CAI after an index ankle sprain.
Research to date has tended to focus more on changes associated with CAI rather than predictors of CAI. Sensorimotor, functional, anatomical or biomechanical changes associated with CAI have been analysed in a number of systematic reviews.
were found to be associated with CAI. Whether these impairments cause CAI or develop as a result of CAI is not clear. Therefore, the objective of the present systematic review was to identify predictors of CAI (e.g., age, sex, body mass index (BMI), level of physical activity, balance, postural control, proprioception, motor control, severity of ankle sprain, perceived ankle instability, feeling of giving way, ligament laxity, pain, or swelling) after an index ankle sprain. Prospective studies investigating any of these variables as potential predictors of CAI after an index ankle sprain might enable health providers to design more effective treatments to prevent ongoing problems.
2. Methods
The study protocol was developed based on the framework outlined in the guidelines provided by the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement.
The protocol of this systematic review is registered on PROSPERO (registration number CRD42012002990).
Studies were included if they met the following inclusion criteria: (i) longitudinal design, (ii) follow-up length of at least three months since the sprain, (iii) participants of any age who had sustained an index ankle sprain only, (iv) measuring at least one of the potential predictors of CAI, (v) reporting on any re-sprain or residual symptoms after the initial ankle sprain during the follow-up period, (vi) published full paper; abstracts were included if the authors provided the raw data for further analysis. Papers where it was possible that at least some of the participants had suffered an index sprain were considered for inclusion, however if the data from this sub-group could not be isolated, then the paper was excluded.
For randomised controlled trials, we included the minimal intervention group (e.g. conservative treatment of lateral ankle sprains, such as modified footwear and associated supports, taping, adapted training programmes, and education). Randomised clinical trials were excluded if there was no minimal intervention group e.g., if surgery or immobilisation for more than three days were investigated.
Studies were identified through a search of the MEDLINE, CINAHL, AMED, Scopus, SPORTDiscus, Embase, Web of Science, PubMed, PEDro, and Cochrane Register of Clinical Trials to May 2013. Abstracts from the International Ankle Symposium (IAS) and International Foot and Ankle Biomechanics (i-FAB) conference proceedings, and bibliographies of eligible studies were hand searched. In addition, relevant experts were contacted to identify any unpublished studies that may exist and to review the list of identified studies for completeness. No language restriction was imposed, however, if a translation could not be arranged, the paper was excluded.
Key terms used in our search strategy are presented in Supplemental file 1. Search protocols were specifically designed to target prospective studies.
All studies identified by the search strategy were screened against the eligibility criteria independently by the first author (FP) and by one other author (CH, JR or KR). Titles and abstracts were inspected and clearly ineligible studies were removed. Full copies of potentially eligible papers were retrieved. Any inconsistencies regarding inclusion of trials were resolved by consensus.
The following predictors, identified from previous studies of risk factors for lateral ankle sprain, were considered as potential risk factors of developing CAI: age, sex, height, weight, BMI, leg dominance, foot type, foot and lower limb alignment, ankle joint laxity, general ligamentous laxity, postural control, muscle weakness or muscle strength/power imbalance in lower limbs, lower limb muscle reaction time, range of motion at lower limb joints, physical fitness, gait biomechanics, and severity of symptoms after the initial sprain (e.g., pain, swelling, laxity, feeling of instability).
Any measures that assessed ongoing impairments associated with CAI after the initial sprain during the follow up period (e.g., re-sprain, swelling, pain, mechanical instability, perceived instability, feeling of giving way, or feeling of weakness) were considered as outcome measures.
Data were extracted independently by two authors (FP and CH) and confirmed by one other author (either JR or KR). Any discrepancies were settled by further discussion and consensus. Study characteristics extracted were study type, target population (setting, sex, age), sample size, inclusion criteria, follow-up duration, prognostic factors measured, interventions (if any) and all reported outcome measures.
Risk of bias and methodological quality of included studies were assessed using the quality assessment tool developed by Pengel et al.
This tool consists of 7 items rated as either ‘yes’, ‘no’ or ‘N/A’ (not applicable). Four items relate to control of bias (items 1–4), two to appropriate measurement of variables (items 5 and 6) and one to control of confounding variables (item 7). Two raters (FP and JR) independently assessed the quality and a third author (CH) resolved disagreements.
Study outcomes were statistically pooled if the studies were considered to be sufficiently homogeneous. For homogeneous studies, raw data were used in a direct logistic regression to assess whether the predictor variables increased the likelihood of re-sprain. If the studies were considered too heterogeneous, data were not pooled and the outcomes were described.
3. Results
The search strategy identified 8085 titles. Following title and abstract screening, 210 potentially relevant articles were identified, of which 16 met all the inclusion criteria. The data required for analysis were reported in two of the included studies.
The authors of the remaining 14 articles, which included participants with one or more ankle sprains, were contacted for data related to the participants with only an index ankle sprain. Seven authors replied, of whom only two were able to provide raw data for analysis.
All included studies were prospective cohort trials, with follow-up periods that varied between 8 and 24 months. Participants were adults in two studies,
included a heterogeneous group of participants, with a history that varied between multiple ankle sprains to no history of sprain, and the time since sprain was not standardised. Separate data of the participants with an index ankle sprain were provided by the authors of these two studies.
Details of the included studies are presented in Table 1.
Table 1Characteristics of included studies.
Author, year
Type of study
Follow-up length
Participants
Inclusion/exclusion criteria
Predictor
Interventions
Outcome measures
Hiller et al. (2008)
Prospective cohort
13 mths
33 adolescents dancers with an index sprain Age: 14 ± 1.8 yrs (total study participants: 115)
Inclusion: dance and ballet students Exclusion criteria: none
Cumberland Ankle Instability Tool, foot movement during single-leg stance with eyes closed (30 s)
None
Re-sprain
Malliaropoulos et al. (2009)
Prospective cohort
24 mths
202 elite Greek track and field athletes Age: 19 ± 4.1 yrs
Inclusion criteria: Acute index lateral ankle sprain, no history of ankle and foot injury Exclusion criteria: syndesmotic injury or a lower limb fracture
Severity of the initial sprain (I, II, IIIA or IIIB)
Common rehabilitation program
Re-sprain
de Noronha et al. (2011)
Prospective cohort
12 mths
11 active university students with an index sprain Age: 20.9 ± 2.7 yrs (total study participants: 125)
had low methodological quality, with a score of 3 (Supplemental file 2). None of these studies used statistical adjustment for potentially confounding factors. Only one study used blinded outcome assessor(s).
were pooled, because they investigated perceived instability and balance as predictors for re-sprain. We were not able to pool data for the two other studies
investigated perceived instability and static balance on both legs as a predictor of re-sprain. Perceived instability was measured using the Cumberland Ankle Instability Tool (CAIT) and balance was measured recording the number of foot movements during single-leg stance with eyes closed for 30 s. Hiller et al.
provided raw data for 44 participants with history of an index ankle sprain. After the follow-up periods of 12–13 months, 11 participants had re-sprained their ankles. Raw data from these two studies were pooled and logistic regression was performed, finding that the predictive capacity of the model was not statistically significant (Table 2). That is, CAIT score and number of foot lifts during single-leg stance with eyes close did not predict re-sprain.
Table 2Odds ratio of re-sprains associated with CAIT scores, balance, and severity of the initial sprain.
(I, II, IIIA and IIIB) to determine severity of sprain. They found significant differences in rate of re-sprain between athletes with different grades of injury during a 24 month follow-up period. Elite track and field athletes with less severe ankle sprain (grade I or II) had a higher rate of re-sprain than athletes with more severe ankle sprain (grade IIIA or IIIB). To further analyse the results of this study, we performed direct logistic regression to assess the impact of the severity of index sprain on the likelihood of re-sprain. The predictive capacity of the model was statistically significant, X2(3, n = 202) = 14.71, P = 0.002. The severity of sprain (grades I to IIIB) explained between 7% (Cox and Snell R2) and 11.4% (Nagelkerke R2) of the variance in re-sprain status, and correctly classified 81.7% of cases. However, only grade I and II made a unique statistically significant contribution to the model (Table 2). The strongest predictor of re-sprain was grade II injury, recording an odds ratio (OR) of 2.6. This indicates that athletes with grade II injury were 2.6 times more likely to re-sprain their ankles.
divided 30 children with an acute ankle sprain into three groups based on the severity of their clinical symptoms (I, II or III). Only children with grade II and III were followed up for eight months. Endele et al.
reported no significant differences between children with grades II or III of ankle sprain, with regard to limitation of mobility, pain or instability, three months after the index injury. These outcome measures were not reported at eight months follow up. Due to the small number of participants in this study (n = 15) no further analysis was performed.
4. Discussion
The present systematic review found that only three potential predictors of CAI (severity of sprain, balance and perceived instability) had been investigated in longitudinal studies after an index ankle sprain. Although recent evidence from cross-sectional studies shows that postural sway, time to balance after a jump, foot position during gait, strength, and proprioception are altered in participants with CAI,
none of these factors has been investigated in a longitudinal study after the index sprain.
Two studies investigated the severity of the index ankle sprain as a potential predictor of CAI, with conflicting results. Although there are factors limiting comparisons between these studies, including the use of different grading systems, different age groups (adults
, classified the severity of index sprains into four grades based on the patients’ clinical symptoms (dorsiflexion range of motion and swelling). Participants were referred for stress radiography only if they were diagnosed with a grade III sprain. In the second study, Endele et al.
also classified the sprains as grades I, II or III based on the clinical symptoms (weight bearing status and swelling), however, they performed additional MRI investigations. Interestingly, they found that clinical symptoms were not well correlated with the grade of injury. The amount of swelling and ability to weight bear were highly correlated with bone bruising, based on their MRI findings. Furthermore, six (50%) children with sprains classified as grade II based on the clinical symptoms, had complete ligament rupture and three had a Salter I injury. These findings raise concerns about the validity of the grading systems based on symptoms, alone.
provides valuable information regarding the severity of ankle sprain in 30 children. In this study however, only children with sprains classified as grade II or III were followed up, and the follow-up was at eight months, potentially an inadequate period when investigating re-sprain and CAI. In this study, anatomical changes were reported in the MRIs of 10 children at eight months, but Endele et al.
did not re-assess pain, mobility or instability at eight months follow up. Since the main aim of this study was to compare symptoms with MRI findings, the outcomes of pain, instability or mobility were not reported.
Based on the results of these two studies, it is not possible to conclude definitively that ankle sprains classified as grades I or II predict development of CAI. To be able to determine whether the severity of an initial sprain predicts CAI, a valid grading system, a large sample size and adequate follow-up are required.
support the proposed model, and explain the lack of predictive value of the CAIT score. Decreased CAIT score, or presence of perceived instability, may increase risk of re-sprain in some subgroups, but not others.
The results of this systematic review also show that postural control, measured as the number of foot lifts during single-leg stance with eyes closed was not a predictor of CAI. Many studies have investigated postural control as a predictor of acute ankle sprain.
These studies however, used different measurement methods and found different results. While most of these studies found decreased postural control as a predictor of acute ankle sprains,
reported that the studies in which postural control was tested by scoring the number of errors during a test, did not show that poorer postural control increased the risk of ankle sprain. They suggested that the increased subjectivity of these methods may increase the variability in scores and render them less meaningful for measuring postural control.
While it seems the number of foot lifts during single-leg stance might not predict re-sprain, these results should be interpreted with caution. Firstly, the different populations in these two studies (adolescent dancers
may have been a confounding factor. In addition, the time from the index ankle sprain was not controlled for, potentially constituting another confounding factor. Finally, the aim of these studies was not to predict CAI after an index sprain, and therefore data were a subset. This resulted in a small number of participants in these two studies with consequent lack of power for our re-analysis.
The strength of this systematic review was that no language limitations were imposed. Where required, a translation in different languages was made (e.g. German, Italian, Japanese, and French). We also included the grey literature. However, several studies could not be included because reporting was insufficient and the data were not available for further analysis.
5. Conclusion
We found that of the three potential predictors of CAI that have been investigated prospectively after an index ankle sprain, only severity of initial sprain (grade II) predicted re-sprain. However, concerns about validity of the grading system suggest that these findings should be interpreted with caution. Consequently, there is a large gap in the literature. Anatomical, central, physiological and psychosocial changes have yet to be investigated after an initial sprain and the relationship of such variables to re-injury and other residual symptoms remains unknown.
Practical implications
•
Severity of the initial ankle sprain does not necessarily predict the likelihood of developing chronic ankle instability.
•
Perceived ankle instability and static balance do not appear to predict future ankle sprains.
•
Currently there is limited research investigating predictors of chronic ankle instability after an index ankle sprain.
Acknowledgments
The authors would like to thank Dr. Markus Hübscher, Ms. Naomi Kusano, and Ms. Alexandra Di Lallo for their assistance in translation of non-English papers.
References
Waterman B.R.
Owens B.D.
Davey S.
et al.
The epidemiology of ankle sprains in the United States.
Population based epidemiology of ankle sprains attending accident and emergency units in the West Midlands of England, and a survey of UK practice for severe ankle sprains.
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