The Prevalence of Selected Intrinsic Risk Factors for Ankle Sprain Among Elite Football and Basketball Players

The lateral part of ankle is one of the most frequently injured structures in the body and the direct and indirect annual medical cost of treating lateral ankle sprain is estimated to reach as high as billions of dollars (1). Although most lateral ankle sprains (LAS) may not cause long-term disability, an important number do not completely resolve, leading to residual symptoms and dysfunction for athletes.The rate of recurrent ankle sprain may reach as high as 40% and repeated ankle sprain is a major cause of chronic ankle instability (CAI) in athletes (2-4). Moreover, as much as 80% of patients with CAI are assumed to finally suffer from osteoarthritis and some cases require surgical interventions (5-7). Therefore, the recognition of factors which may be related to lateral ankle sprain seem to be the cornerstone of an effective ankle sprain prevention program. Despite many authors evaluating the relationship between different intrinsic factors such as anatomic characteristics (8), balance (9, 10), joint position sense (11), flexibility and range of motion (12), reaction time (13), muscle strength (13, 14), gait pattern (15), body mass index (16), ankle instability (17), generalized laxity (12) and lateral ankle sprain, no consensus has been reached on the predictive intrinsic risk factors. Consequently, the predictive intrinsic factors in LAS remain still to be defined, and further studies are needed. Additionally, while ankle stability is maintained by different parameters including bony structure, foot biomechanics, flexibility and neuromuscular control (2, 18), the majority of authors have merely focused on the neuromuscular mechanisms as an essential factor for ankle stability.

This study was conducted to determine the prevalence of selected intrinsic risk factors for ankle sprain including foot posture, foot dimensions, generalized and localized joint laxity and static and semidynamic balance, ankle and first metatarsophalangeal range of motion among elite football and basketball players and recognize whether they are related to the incidence of acute or recurrent ankle sprain.

In a cross- sectional study, elite basketball and football players were recruited. Inclusion criteria were as follows: 1, history of at least one year of experience in professional sports and at least 3 to 5 training sessions in a week within last 6 months; 2, male gender; 3, age 15 to 40 years; 4, lack of history of orthopedic surgery in lower extremities, any malalignment and spinal deformity. Exclusion criterion was patient’s request to leave the study. The study protocol was approved by the ethics committee of Tehran University of Medical Sciences. All samples were asked to sign an informed consent form prior to participating in the study.

During the preseason period, a prepared checklist was completed for 106 elite basketball and football players who were referred to sports medicine clinic of Sports Medicine Research Center affiliated to Tehran University of Medical Sciences (TUMS) for pre-participation examinations (PPE). All players underwent baseline measurements and were asked for any history of previous ankle sprain and severity, quality and number of injuries in the last two years. Athletes were assessed for measures of foot posture index- 6, foot length and width, Beighton generalized joint laxity score, anterior drawer and talar tilt tests, star excursion and single leg balance tests and goniometric assessment of ankle plantarflexion, ankle dorsiflexion and first metatarsophalangeal dorsiflexion. Each measurement was performed by a single well experienced physician in a station-based model.

LAS was defined as an ankle injury with an inversion mechanism that caused the player feel pain or discomfort in the lateral side of ankle, regardless of missing or not missing a game or practice.

Recurrent LAS was defined as the multiple ankle injury with a low energy inversion mechanism and less than three months interval between two injuries.

Data collection was performed using researcher-designed checklist. Demographic data and risk factor assessments were registered in this checklist considering both lower extremities. All measurements were performed by sports medicine specialists. Baseline measurements included foot posture assessment (using FPI-6), foot characteristics (length, width and length to width ratio), generalized joint laxity (using Beighton and Horan score), lateral ankle ligaments laxity (measured by anterior drawer test and talar tilt test), static and semidynamic balance (measured by single-leg balance test and star excursion balance test), and goniometric measurement of ankle plantarflexion, ankle dorsiflexion and first metatarsophalangeal dorsiflexion. To address the inter-rater variability of the subjective assessments, each examination was performed by a sports medicine expert in a separate station.

Detailed description of all measurements are as follows:

A total of 106 participants [48 basketball players (45.3%) and 58 football players (54.7%) with mean (SD) age of 19.8 (4.5) years participated in this study. The descriptive information is shown in Tables 1, 2.

Sixty two (58.5%) athletes had a history of sprain and 15 athletes (14.2%) reported history of recurrent sprain in at least one extremity (Table 2). Acute and recurrent ankle sprain both were more prevalent in basketball players (P = 0.002 and P = 0.018, respectively).

There was no relationship between acute or recurrent ankle sprain and FPI-6, foot dimensions and generalized joint laxity in athletes (P > 0.05). There was a relationship between acute as well as recurrent ankle sprain and some aspects of ankle joint laxity (Table 3).

The positive Single Leg Balance Test was related to acute LAS (P=0.035) but not to recurrent LAS. Also, no correlation was detected between the SEBT and acute or recurrent LAS. No relationship was found between dorsiflexion of ankle as well as the first metatarsophalangeal joint and acute or recurrent LAS. However plantarflexion of the left ankle was related to acute (P = 0.009) and recurrent (P = 0.02) LAS.

This study showed that some intrinsic risk factors including ankle joint laxity, impaired Single Leg balance test and decreased ankle plantarflexion are more prevalent in athletes with history of acute or recurrent LAS.

Based on this study the positive anterior drawer and talar tilt tests seem to be more common in athletes with acute as well as recurrent LAS. Of course, due to the cross sectional nature of this study, results can merely demonstrate the higher prevalence and these significant differences may not represent a causal effect.

According to the published prospective studies, using the anterior drawer and talar tilt tests to predict occurrence of LAS in athletes present conflicting results.While some authors demonstrated that the anterior drawer and talar tilt tests did not predict ankle sprains, (17) others reported a higher incidence of LAS in athletes with positive talar tilt and anterior drawer tests (13, 28). Through a retrospective study, Denegar et al. (29) reported that significant differences in joint laxity are found between injured and uninjured ankles based on the anterior drawer and talar tilt tests. This finding is in accordance with the result of the present study. Also, in this study like many previous projects (8, 9, 12), no association was detected between generalized joint laxity and LAS.

The relationship between balance and LAS is the main subject of many previous studies. Different methods have been used in the previous studies to assess the balance in athletes. However the Single-leg balance test and the star excursion balance test are the two most commonly used methods in the previous surveys to assess balance of the athletes. According to this study, only the positive single leg balance test was related to acute LAS while no association was found between the SEBT and LAS. Since the majority of previous surveys (24, 30-32) established that balance deficits could predict ankle injury susceptibility in athletes and as the present study was not able to show the causality between different variables, it is not rational to draw conclusions that the SEBT cannot be used to predict LAS in athletes. Besides, the lack of relationship between the SEBT and LAS in the present study is not supported by a recent study where Doherty et al. (33) showed that acute first-time LAS was associated with impaired SEBT. However, this study was performed on samples who suffered from acute first-time LAS, while the players with a history of acute or recurrent LAS during past 2 years were included in the present study. On the other hand, the lack of association between LAS and static and especially semidynamic balance measurements may be explained by this fact that injured athletes may perform the balance and proprioceptive training more vigorously compared with other athletes to continue their professional career and therefore, may not show any difference.

Another finding in this study was the relationship between decreased left ankle plantarflexion and acute or recurrent LAS, while no relationship was found between dorsiflexion of ankle as well as the first metatarsophalangeal joint and LAS. This finding is nearly in accordance with the result of a previous study where Denegar et al. (29) reported that ankle dorsiflexion was mainly restored following LAS.

Static measurements of foot features are mainly performed to determine the relationships between the anatomy as well as biomechanics of foot and LAS (34). Based on this study, none of the foot characteristics including foot length, foot width and Foot Posture Index were related to LAS. However, among different foot characteristics, cavovarus deformity, increased foot width, and increased calcaneal eversion range of motion are reported as the most commonly parameters which have been related to LAS (34). Regarding the relationship between FPI-6 and LAS, the findings of the present study are not supported by previous surveys (34-37), where they reported that having an under-pronated to supinated foot type is associated with an increased risk of ankle injury. This difference may be due to prospective design of the mentioned studies.

The limitations of this study were as follows: First, the surveys like this study, by nature, lend to information bias as participants may not recall their experiences, properly. However, as these events may significantly affect the professional career of these elite athletes, this problem may not apply in this group. Secondly, although cross-sectional studies can be a useful method in gathering general information about samples, it is difficult to evaluate causality. Lastly, due to difficult access to the elite athlete, we were obliged to use conventional sampling and therefore, results of this study may not be generalized to all football and basketball players. Furthermore, the biomechanical differences between football and basketball may impact on some intrinsic factors such as the ankle range of motion and may be considered as a potential confounding factor.