Effect of Limb Dominance on Chronic Ankle Instability: Does It Matter?

Abstract

Our study aimed to examine preoperative differences in strength and balance between dominant foot (DF) and nondominant foot (non-DF) of individuals undergoing ligament stabilization surgery in the general population. Patients with records of preoperative evaluation, including isokinetic dynamometric strength evaluation, Y-balance test (YBT), and Foot and Ankle Outcome Score (FAOS), were included in the study. The DF was the preferred leg for accurately kicking a ball through a goal. Statistical analysis determined the differences between DF and non-DF and the correlations between muscle strength, balance, and FAOS. There was no statistically significant difference between DF and non-DF regarding evertor and invertor muscle strength (p=0.082–0.951). The YBT revealed no significant difference between the two groups (p=0.082–0.951). There was a significant correlation between the evertor peak torque and total work deficits at 30°/s (p=0.022), as well as the evertor peak torque deficit at 120°/s (p=0.048). No significant differences in muscle strength and balance were found between DF and non-DF in nonathletes with chronic ankle instability. Peroneal muscle strength deficit was associated with functional impairment. Tailored interventions are needed to address limb dominance and muscle strength deficits in CAI management.

Keywords

dominant foot - muscle strength - balance - foot and ankle outcome score

Introduction

Chronic ankle instability (CAI) is persistent instability following an ankle sprain that causes the ankle to repeatedly give way, resulting in functional limitations. This condition, affecting about 25% of people with sprained ankles, can lead to long-term consequences, such as ankle arthritis, significantly affecting quality of life [1].

Limb dominance is a tendency of a person to favor one leg over the other during activities requiring unilateral movement or support, such as kicking balls, stepping onto a box, balancing after a posterior push, or standing on one leg. Various factors, including genetics, injury history, and training, contribute to determining limb dominance [2] [3]. The dominant foot (DF), which is typically used more during physical activities, may exhibit greater strength and balance than the nondominant foot (non-DF) [3] [4]. Thus, the presence of CAI in the dominant leg could affect the function and symptoms.

Limb dominance may predict lateral ankle sprains and increase the risk of lower extremity injuries. However, several studies have found no significant difference in injury rates between dominant and nondominant ankles [2] [3] [4] [5] [6]. These studies mainly analyzed the influence of limb dominance on athletes with CAI. Studies on how limb dominance affects nonathletes with CAI are lacking.

DF affected by CAI may show reduced strength and balance compared with non-DF. Our study aimed to examine preoperative differences in strength and balance between the DF and non-DF of individuals undergoing ligament stabilization surgery in the general population.

Materials and Methods

Our institutional review board approved this study (Institutional Review Board No. 2022–09–031). Informed consent was waived due to the retrospective design of the study. We reviewed the medical records of all patients with a lateral CAI who visited our hospital between March 2020 and March 2023. Patients with records of open or arthroscopic lateral ligament stabilization surgery and preoperative evaluation, including isokinetic dynamometric strength evaluation, Y-balance test (YBT), and Foot and Ankle Outcome Score (FAOS), were included in the study.

All included patients underwent lateral ligament stabilization surgeries performed by a single surgeon. The choice of surgical procedure was based on the discretion of the surgeon and the preference of the patient after being informed of the procedures. The preoperative examination results did not influence the choice of surgical method. Open surgery was preferred if the patient was active, such as athletes or military personnel. Otherwise, arthroscopic surgery was preferred, especially for those more sensitive to incisions, such as young women. The DF was the preferred leg best able to kick a ball through a goal, as this is the most effective assessment method [7]. Only patients with a right-sided DF were included to minimize statistical error. Exclusion criteria included patients with previous foot and ankle surgery; known conditions such as tarsal coalitions, neuromuscular diseases, or recent trauma that could interfere with the examination; incomplete medical examinations and records; and generalized laxity with a Beighton score>4.

Isokinetic dynamometric strength evaluation

The isokinetic dynamometer (Cybex NORM®, Humac, CA, USA) was used to assess the ankle evertor and invertor muscle strength. The patient assumed a sitting position with the knee flexed at 90° and the thigh secured to the pad. The feet were secured to the inspection device. The handles were gripped to keep other body parts immobile, while the legs, waist, and torso were fixed to the seat. The ankle was positioned with 10° plantar flexion in the foot adapter and secured using two Velcro straps ([Fig. 1a]). An isokinetic test was performed in concentric mode for ankle eversion and inversion at angular velocities of 30°/s (5 repetitions) and 120°/s (10 repetitions). The test range was 30°–35° for ankle inversion and 25°–30° for ankle eversion [8]. Three trials were conducted before each test, with a 20-second rest between the trial and the test and a 90-second rest between the two sets. The patients received encouraging feedback to exert maximum effort. For accuracy, the strength of the healthy ankle was measured before the injured foot was examined. The parameters recorded included peak torque, time to reach peak torque, and work performed.

Fig. 1 The position of the patient on the dynamometer to perform the ankle evertor and invertor muscle strength test (a) and the Y-Balance test (b).

Y-Balance test

The YBT was performed as a dynamic balance assessment using the YBT equipment (FMS TM, Chatham, VA, USA) and following the recommended guidelines [9]. After the isokinetic strength test, participants had a 20-minute rest. The YBT was performed by placing each foot of the participants on the examination table with one foot positioned at the center and extended as far as possible in the anterior, posterior lateral, and posterior medial directions ([Fig. 1b]). Testing began with the healthy side, followed by the injured side, with the examiner giving verbal instructions. Each side was tested three times, and the highest recorded value was documented. The recordings were made at 0.5 cm increments. If a loss of balance resulted in the foot touching the ground, the test was repeated after an explanation. The examiner observed the participants from behind to minimize distraction. The lower limb length was measured from the anterior superior iliac spine to the middle of the medial malleolus using a tape measure. The total score was calculated using the following formula: ([sum of the three distances]/[lower limb length×3])×100.

Foot and ankle outcome score

The FAOS questionnaire was developed to assess symptoms or pain in various situations related to foot and ankle problems [10]. A transculturally adapted FAOS was used in this study [11].

Statistical analysis

Descriptive statistics (means, standard deviations, and proportions) were calculated. A Kolmogorov-Smirnov test was used to assess the distribution normality of continuous variables. Comparisons between DF and non-DF were conducted using a t-test or a Mann-Whitney U test, depending on the data characteristics. The isokinetic dynamometric strength evaluation and the YBT results were analyzed for correlation with FAOS using Pearson’s correlation coefficients. Statistical analyses were performed using SPSS version 20.0 (IBM Co., Chicago, IL). P values<0.05 were considered significant.

Results

A total of 43 patients (24 men and 19 women) with right-side lateral CAI were included ([Fig. 2]). The mean age at the time of surgery was 34.1±15.1 years (range, 15–72). Of the 43 patients, 31 and 12 underwent open and arthroscopic surgeries, respectively. The surgery methods did not influence the results, as the study was based on the preoperative evaluation. A total of 26 and 17 patients reported their affected right side as their DF and non-DF, respectively. The mean FAOS score was 67.8±14.8 (range, 28–92). The mean FAOS scores for patients with affected DF and non-DF were 65.7±16.2 and 71.0±12.1, respectively. The mean FAOS scores for patients who had undergone open and arthroscopic surgeries were 68.9±15.6 and 65.1±12.4, respectively ([Table 1]).

Fig. 2 Inclusion and exclusion criteria.

Table 1 Patient demographics.

Parameter	Measurements	95% CI	p-value
No. of subjects (Male/Female)	43 (24/19)
Laterality (Right:Left)	43/0
Age at operation (Mean±SD)	34.1±15.1 (15–72)
OP type (Arthroscopic/open surgery)	12/31
FAOS	67.8±14.8 (28–92)
DF	65.7±16.2	− 14.5–4.0	0.257
Non-DF	71.0±12.1
Arthroscopic surgery	65.1±12.4	− 14.0–6.4	0.457
Open surgery	68.9±15.6

Age at operation and FAOS; mean±standard deviation (range); Age=decimal years; CI=confidence interval; DF=dominant foot; OP=operation.

[Table 2] compares the isokinetic dynamometric evaluation of ankle evertor and invertor muscle strength and the YBT between the DF and non-DF. There was no statistically significant difference between the DF and non-DF regarding evertor and invertor muscle strength (p=0.082–0.951). The YBT also showed no statistically significant difference between the two groups in the anterior, posterior medial, and posterior lateral directions (p=0.082–0.951).

Table 2 Comparison of preoperative measurements based on the presence of dominant foot instability.

Measurements			DF	Non-DF	95% CI	p-value
Y balance	AN		− 5.5±6.0	− 6.8±11.4	− 4.0–6.7	0.621
	PM		− 6.3±9.0	− 5.4±14.7	− 8.2–6.4	0.805
	PL		− 5.1±9.1	− 8.1±7.3	− 2.3–8.3	0.264
Peak torque deficit (%)	Invertor	30º	20.5±26.0	25.2±30.2	− 22.2–12.7	0.587
		120º	17.8±26.7	20.3±23.0	− 18.5–3.5	0.755
	Evertor	30º	25.9±26.0	21.1±32.1	− 13.2–22.7	0.597
		120º	18.3±20.7	20.7±23.8	− 16.2–11.4	0.731
Total work deficit (%)	Invertor	30º	21.9±31.1	30.6±32.2	− 28.6–11.1	0.381
		120º	22.3±29.9	32.2±32.8	− 29.4–9.7	0.316
	Evertor	30º	27.5±25.4	26.9±33.7	− 17.6–18.8	0.951
		120º	23.1±23.7	28.6±28.9	− 21.7–10.8	0.503
Time to peak torque	Invertor	30º	0.14±0.28	0.02±0.31	− 0.07–0.30	0.220
		120º	− 0.01±0.11	− 0.04±0.08	− 0.02–0.98	0.278
	Evertor	30º	0.18±0.02	0.02±0.31	− 0.02–0.35	0.082
		120º	0.01±0.13	0.06±0.18	− 0.15–0.04	0.260

DF=dominant foot; CI=confidence interval; AN=anterior; PM=posteromedial; PL=posterolateral.

The relationship between the FAOS score and the isokinetic muscle strength of the affected side was also examined. There was a significant correlation between evertor peak torque and total work deficits at 30°/s (p=0.022), as well as the evertor peak torque deficit at 120°/s (p=0.048) ([Table 3]). This suggests that functional impairment correlates with reduced peroneal strength.

Table 3 Relationship between FAOS and the concentric strength.

Measurements			r	p-value
Peak torque deficit (%)	Invertor	30º	− 0.231	0.137
		120º	− 0.040	0.801
	Evertor	30º	− 0.349	0.022
		120º	− 0.259	0.094
Total work deficit (%)	Invertor	30º	− 0.236	0.128
		120º	− 0.103	0.509
	Evertor	30º	− 0.374	0.013
		120º	− 0.303	0.048
Time to peak torque	Invertor	30º	− 0.140	0.370
		120º	− 0.083	0.596
	Evertor	30º	− 0.106	0.499
		120º	− 0.077	0.622

Discussion

Our findings revealed that there were no significant differences in muscle strength and balance between the DF and non-DF in individuals with CAI, contrary to the expectation that the dominant limb, typically subjected to greater physical demands, might exhibit greater strength and balance [3] [4]. Therefore, it could be interpreted that the muscle strength and balance of the DF were reduced compared with those of the non-DF in individuals with CAI.

Interpreting the results is difficult as to whether the similarity in muscle strength and balance on both sides is due to reduced overall physical activity levels (resulting from discomfort in the affected ankle), or whether it is a consequence of reduced use of the affected side. The absence of significant differences in FAOS between patients with CAI in the DF and non-DF groups could indicate an adaptation to the chronic condition. Alternatively, it might be attributed to the increased use of the non-DF when the DF is affected. The complex relationship between discomfort, muscle strength, and balance in CAI requires further research.

To minimize statistical errors, our study only included patients with right-sided DF. The literature presents varying results regarding lower limb dominance and its association with ankle sprains. While some studies suggest that lower limb dominance is a risk factor for injury, particularly in high-demand activities [6] [12], others show conflicting results [13] [14]. We excluded patients with left-sided DF to address this ambiguity.

Bilateral muscle strength deficit is a risk factor for CAI. It has been studied in athletes [15] due to its role in injury prevention and rehabilitation [8]. Eler et al. found no difference in the ankle evertor and invertor muscle strength between the dominant and nondominant limbs in their research of elite handball players [16]. In 1984, Wong et al. observed symmetry in the ankle evertor and invertor muscle strength in both limbs of healthy individuals [17]. However, similar studies in nonathletes with CAI are lacking. Our findings indicate no discernible difference in strength between the limbs.

CAI has been associated with peroneal muscle strength, suggesting that peroneal muscle weakness may contribute to CAI development [18]. Arnold et al. reported that decreased eversion strength is associated with impaired proprioception and contributes to CAI development [19]. Our study also found that peroneal muscle strength deficit was correlated with reduced FAOS. Thus, evertor muscle strength is important in stabilizing the ankle and preventing CAI, and evertor muscle strengthening exercises need to be included in rehabilitation protocols.

This study had several limitations. First, only a small number of patients were included. Therefore, it is difficult to generalize the results. However, the significance of our study lies in analyzing the impact of dominant foot on ankle instability from a different perspective compared to previous research. Second, this was a retrospective study; thus, many patient factors were not adequately controlled. We made extensive efforts to control those factors by applying broad exclusion criteria and only including patients with right-sided DF. However, the lack of information regarding the preexisting patient conditions and the different conservative treatment periods and methods until the decision for surgery made it difficult to take these variables into account. Future prospective studies with a larger number of well-controlled participants are needed. Third, we did not include the imaging results of the patients in the analysis. Functional instability and patient discomfort play crucial roles in deciding the surgical treatment for CAI. Although the relative importance of imaging can be diminished, it is still essential to consider the effects of ligament damage and mechanical instability on strength and proprioception.

Conclusion

In conclusion, no significant differences in muscle strength and balance were found between the DF and non-DF in patients with CAI. Peroneal muscle strength deficit was associated with functional impairment. Thus, peroneal muscle strengthening is essential in CAI rehabilitation. When CAI affects the DF, a substantial decrease in strength can be expected. Therefore, these findings should be considered in conservative treatment approaches.

Conflict of Interest

The authors declare that they have no conflict of interest.

Acknowledgement

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MIST) (No. RS-2023–00249202). This funding source had no role in the design of this study and will not have any role during its execution, analyses, interpretation of the data, or decision to submit results.

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Publication History

Received: 20 February 2024

Accepted: 18 May 2024

Article published online:
19 June 2024