Prevalence and Foot Intrinsic Associated Factors of Ankle Sprains among a Random Sample of Tunisian Athletes: Across-Sectional Study

Objective To determine the prevalence of ankle sprains and its associated factors in athletes. Methods This was a cross sectional descriptive study conducted among a random sample of 107 athletes. The subjects were recruited from 6 different associations in Sousse, Tunisia. Demographic, medical and foot characteristics were collected using a medical le completed by a validated, self administered questionnaire to verify ankle instability. All components of this study were approved by a research ethic committee, and all participants gave informed consent at every stage. Data entry and analysis were performed using SPSS 20 Software. The level of signicance was set at p <0.05. Results The prevalence of ankle sprain was 71%. The associated factors were; the weight (p=0.033), the type of sport (p=0.038), the prole of the athlete (p=0.006), the unipodal static balance (p= 0.006), the limitation of the joint mobility (p=10 -6 ), the ligament laxity (p<0.05), the muscular force especially the eversor muscle (the long bular) (p<0.05) and the inversor muscle (the posterior tibial) (p<0.05) and the ankle instability (p<0.05).


Introduction
Ankle sprain is the most common injury in sports. In France, its prevalence varies between 15% and 45% [1]. In the United States, its incidence is estimated at 6445 injuries per year [2] and the cost of treatment reached about 1008$ for lateral injuries and 914$ for medial ones [3].
This injury affects mainly the lateral ligament of the ankle causing thus either a simple distension (benign sprain) or a partial total tear (moderate or severe sprain) and more rarely the medial deltoid ligament [4]. It occurs when the foot violently bascule in inversion or eversion during a false step or in the brutal reception of the foot during a parachute jump [4].
Its appearance can be linked to several factors divided into intrinsic factors such as the musculoskeletal system, the ligament system, the joint mobility, and the proprioceptive foot receptors and extrinsic factors such as the athletes' footwear, frequency of training, type of gait, and the types of elds (ground) [5][6].
It can cause a temporary cessation of sport activity whose rest period varies according to its severity and even after resumption; the athlete may suffer from multiple discomforts such as: ankle chronic instability, ligament laxity, chronic pain, muscular weakness [8]. These manifestations can affect his sport activity, performance, posture, gait and even activities of daily life [7].
Despite its frequency of occurrence, the severity of its sequelae and its ability to in uence the athlete's life, the prevalence of ankle sprain remains unknown in Tunisia. Therefore the objective of this study was to determine the prevalence of ankle sprain in athletes and its associated factors. Methods 1. Type, period and places of the study A cross sectional descriptive study was conducted over a period of 4 months in 6 sport associations in the region of Sousse, Tunisia.

Participants
We randomly selected 107 participants based on a proportional sampling from 6 different sport types.
We included in this study athletes playing football, handball, volleyball, basketball, and tennis or running who gave their consent to participate in the study and who has a period of sports activity equal to or greater than 1 year.

Data collection
Data were carried out from the compilation of two sources of information. On one hand, a clinical le designed for foot and ankle examination. On the second hand, a validated self-administered questionnaire "The Cumberland Ankle Instability Tool" or the CAIT used to verify ankle instability [7][8].
The clinical le contained basic information related to anthropometric data such as; age, gender, height, weight and body mass index. Then sport data (type of sport, years of practice, pro le, regularity and techniques of preparation for exercise: warming up, stretching... Participants were asked about the injuries they had suffered from during their sport career (fractures, tendonitis, dislocations and ankle sprains...).
The index of Hernandez Corvo was used to determine the type of foot ( at, cavus) [9][10], The unipodal test served to evaluate static balance [11][12]. Ligament laxity was assessed using the method of varus and valgus stress test and with the anterior drawer test. Muscular force was tested by global and analytical testing [13].

Data analysis
Data entry and analysis were performed using SPSS 20 Software. Basic descriptive statistics (percentage, frequencies, etc.) were obtained for all participants by group. Differences were declared signi cant at the 0.05 level (i.e., when P < 0:05).

• Descriptive results
Among the 107 athletes recruited in the study, 71 were males (66.4%) and 36 were females (33.6%) with a mean (SD) age of 19.36 (4.24) years. Table 1 shows the distribution of the athletes by type of sport.

Prevalence
The occurrence of sprain ankle in our sample was about 71% (76 athletes). Among our 76 athletes with ankle sprains, 93 ankles were affected by this trauma in which 51 were right ankles and 42 were left.
Unilateral exposure was more frequent with a percentage of 77.6% compared to the bilateral exposure that represented 22.4%.
Analytic results

Anthropometric factors
The anthropometric data showed that no differences were found between the injured and uninjured groups in terms of gender, age, height and body mass index (BMI). Signi cant differences were found only in weight (p = 0.033).

Factors related to sport activity
The study assessed associations between; the sport type, the category of athletes, the pro le, the regularity in practice, the years of practice, the preparation, the warming up and the stretching before physical exercises and the ankle sprain. All factors were found not statically signi cant except for the type of sport (p = 0.038) and the pro le of the athlete (p = 0,006). Table 3 depicts the full results. The p values for each factor are presented as well.

Foot intrinsic factors
The foot examination revealed a signi cant differences between groups in terms of unipodal static balance (p < 0.05), dorsi exion mobility (p < 0.05) and ankle instability (p < 0.05).   The examination of the muscular force revealed that the athletes with injured ankle had more limitations than those who are not affected. Indeed, a signi cant difference between groups were found in the long tibial muscle (p < 0.05) and the posterior tibial muscle (p < 0.05).

Prevalence
Our study showed that the ankle sprain affected 71% of our sample. This percentage was lower to the study conducted by Karen G. Roos et al, in which the prevalence of ankle sprains in National Collegiate Athletic Association Sports was 95% [14]. However, another study showed that ankle sprains represented 15% of injuries occurring in the eld of sport [1]. These differences between the results can be explained by methodological difference such as; sampling techniques or the characteristics of the different groups in different contexts or even to the negligence of athletes of the preventive measures of ankle sprains, hence its high frequency.

Ankle sprain
As for the location of ankle sprains, we noted that unilateral injury was more frequent (77.6%) compared to bilateral injury (22.4%). This can be explained by the fact that ankle sprains frequently affect the dominant member of the athlete. According to Ekstrand and Gillquist jan, the risk of ankle injuries increases in the dominant member [15].
The male population was more affected by ankle sprains (64.5%). Our results were comparable to those found in a study by Karen G. Roos et al. In fact, they demonstrated that the exposure to ankle sprains in men was higher than women [14]. The low vulnerability of women can be explained by their exibility and by the practise of less offensive and lower risks sports.
The percentage of ankle sprains in athletes also varied according to the type of sport practised; it decreases from Basketball (86.2%) to Handball (75%), then Football (70%), Running (65.2%), Tennis (61.5%) and nally Volleyball (33.3%). A study by Romain Terrier et al. reported results comparable [16]. These results can be explained by the facts that Basketball contains a lot of movements of brutal reception of the foot during parachute jumps that can cause a bascule of the foot in inversion or eversion cause though ankle sprains.
Based on our ndings, cadets were the most affected category with ankle sprains (47.6%) compared to seniors (33.3%) and juniors (18.7%). These results can be explained, on one hand by the fact that cadets do not yet master the technical gestures. On the other hand by the fact, that seniors have usually a training rhythm more intense than cadets and juniors which can increase the rate of exposure.
All the athletes with ankle sprains were competitors. This result was similar to the one observed in a study conducted by Yeung Mphil et al. who were interested in competitor athletes [17]. Therefore, the high frequency of training hours and the intensive rhythm for competitors can generate a hyper-extensibility of the ankle ligaments and solicit them which can make the ankle more at risk of developing sprains compared to amateurs that usually practise sport for leisure and just to stay in shape.

Associated factors
Regarding anthropometric data; the results showed that no statistically signi cant difference was observed for age, gender, height and body mass index. However, weight was shown to be statistically signi cant with ankle sprain (p = 0.033). A study conducted by Bruce D et al. on 118 college athletes demonstrated that height and weight were not related to ankle sprains [5]. These results can be explained by the fact that the majority of our athletes have normal body mass indexes. Thus, we cannot resume if there is an association between the ankle sprain and excess of weight.
Concerning sports data, our results demonstrated that ankle sprain was associated to the type of sport practiced (p = 0,038) and to the pro le of the athlete (p = 0,006). Indeed, the characteristics of all type of sports included in this study, solicit the ankle and its different compositions. Hence, the occurrence of ankle sprains.
According to Bruce D, Beynnon et al., the type of foot and the type of the hindfoot are not associated to the incidence of ankle sprain [5]. Likewise, Dahle et al. [18] and Barrett et al. [19] reported no correlation between anatomic foot type (pronated, neutral, or supinated) and the incidence of ankle sprains. Our results support these ndings.
Regarding unipodal static balance, the majority of the athletes affected with ankle sprains had an alteration of the unipodal balance compared to those not affected. This association was found statistically signi cant with p < 0.05. This fact can be explained by the alteration of the ligaments that stabilize the ankle joint which can be responsible for static disorders.
In our study, the ankle instability was associated to ankle sprains. Indeed, residual ligament laxity can result in the loss of the joint stability. Therefore, the athlete may feel insecure. According to Thomas Bauer, ankle instability is the main sequelae that patients complain about after ankle sprains [20].
Regarding muscular force, only the long bular and the posterior tibial muscles were found statically signi cant. These results can be explained by the fact that the eversers are the lateral stabilizing muscles of the ankle. During a sudden reversal movement, the weakened ones will not stabilize the ankle and they will let it roll up. However, the athlete may previously have a weakness of the muscles which would leave the ankle unstable and can lead to the occurrence of ankle sprains.

Limitations
The current study was conducted only in the region of Sousse. Hence the results cannot be generalized to the general population and also should be carefully interpreted.
In this study, we used a self-administrated questionnaire in order to assess ankle instability. However, questionnaires can be subjective and this can lead to an over or underestimation of the results.
Mmissing data on medical records of athletes were one of the most limitations that we have faced during the realization of this study. However, some medical questions were asked directly to the attending physician in order to ll the missing data.

Conclusion And Implications For Practice
Ankle sprain is a frequent trauma in the sports eld. Often benign, however it should not be overlooked because of its frequent recurrence, the potential painful sequelae and the risk of instability that it can cause. All of these manifestations have a negative impact on the athlete's performance.
For this major reason, this injury has aroused the interest of several researchers in the eld of health and sport sciences seeking to explore it and identify the factors leading to its occurrence.
This research can enable healthcare professionals and sportsmen to better understand factors that can lead to ankle sprains. In fact, the main associated factors highlighted in this study must be taken into consideration in order to prevent these injuries and to improve sportsmen´s performance.