Morphological and Functional Characteristics of the Peroneus Muscles in Patients with Lateral Ankle Sprain: An Ultrasound-Based Study

A cross-sectional study on peroneal muscle echogenicity changes and their effects on balance functions in individuals with chronic ankle instability

This study investigated the relationship between peroneal muscle echogenicity and balance function in individuals with chronic ankle instability (CAI). While prior research has examined peroneal muscle activity, reaction time, and balance, the impact of echogenicity-an indicator of myosteatosis/fibrosis-remained underexplored. Cross-sectional study. Sixty-two adults with CAI were included. Peroneal muscle size, echogenicity, and stiffness were assessed using ultrasound. Dynamic balance was evaluated via the Y balance test (YBT), and static postural control was evaluated during lateral step-down (LSDT) and single-leg stance test (SLST). Eversion strength was assessed with a dynamometer. The relationship between muscle characteristics and balance was assessed using canonical correlation and stepwise linear regression. Individuals with increased peroneal muscle echogenicity had reduced muscle size, poorer eversion strength, and poorer balance. Eversion strength is positively associated with YBT scores across all echogenicity levels and negatively associated with posture parameters during the LSDT in moderate echogenicity. Peroneal longus stiffness was positively associated with YBT in severe echogenicity and posture parameters during the SLST. Increased peroneal muscle echogenicity is associated with poorer eversion strength and stiffness, resulting in poorer balance performance. Improving the peroneal muscle quality may enhance functions in the CAI condition.

Quantitative ultrasonography of the foot muscles: a comprehensive perspective on reliability

Background

Quantitative ultrasound imaging is a popular technique to assess the structural properties of the intrinsic and extrinsic foot muscles. Although several studies examined test-retest reliability, specific gaps remain in assessing inter-rater reliability, particularly distinguishing between image acquisition and muscle measurement. Additionally, these studies utilized equipment that may not be generalizable across both clinical and research settings and often involved small sample sizes without prior sample size calculations. This study aimed to investigate test-retest reliability as well as global and measurement-based inter-rater reliability (MIRR) using a low-end ultrasound device to measure intrinsic and extrinsic foot muscle sizes.

Methods

This prospective reliability study included 21 active individuals. Five intrinsic muscles [abductor hallucis (AbH), flexor digitorum brevis (FDB), flexor hallucis brevis (FHB), quadratus plantae (QP), abductor digiti minimi (AbDM)], and three extrinsic muscles [peroneal (PER), flexor digitorum longus, tibialis anterior (TA)] were scanned. Three investigators independently acquired images on two occasions and measured cross-sectional area (CSA) and thickness in September and October 2023. Participants were assessed either at the Musculoskeletal Research Group laboratory (University of Leuven, Bruges) or in the Rehabilitation Sciences laboratory (Ghent University hospital). Test-retest (same investigator, one week in between), global inter-rater (each investigator measures own image set) and MIRR (three investigators measure one image set) was performed following intra-class correlation, standard error of the measurement (SEM) and coefficient of variation.

Results

Test-retest reliability showed intraclass-correlation coefficients of 0.60-0.88 for the FDB and 0.38-0.73 for the TA. SEM ranged from 0.16 to 0.41 cm2 (CSA) and from 0.05 to 0.31 cm (thickness) for the intrinsic, while they ranged from 0.19 to 1.13 cm2 and from 0.12 to 0.44 cm for the extrinsic muscles. Global inter-rater correlation coefficients varied between 0.4 and 0.8 for the AbH and FDB. Measurement based inter-rater correlation coefficient varied between 0.50 and 0.96 for AbH, FDB, TA and PER muscles. SEM ranged from 0.14 to 0.89 cm2 (CSA) and from 0.07 to 0.24 cm (thickness) for the intrinsic, while they ranged from 0.29 to 0.85 cm2 (CSA) and from 0.12 to 0.51 cm (thickness) for the extrinsic muscles. Coefficients of variations were between 4% and 34%. For test-retest, they were consistently ≤10% for AbH thickness, FDB CSA, FHB and TA. FDB coefficients of variation were ≤10% across all inter-rater reliabilities.

Conclusions

Most muscles demonstrated moderate to excellent test-retest reliability using a portable ultrasound device, supporting its generalizability. However, the greater variability in global inter-rater reliability suggests substantial variation during image acquisition. The same clinician should perform pre-intervention and follow-up assessments to minimize errors. If different clinicians are involved, caution is needed when comparing measurements.

Comparison of the distance between the talus and lateral malleolus during the stance phase with and without chronic ankle instability

The level of dynamic mechanical instability between the bony parts of the ankle joint provides important information on biomechanical function. However, the dynamics of the distance between the talus and lateral malleolus during gait remain unclear. This study aimed to compare the distance between the talus and lateral malleolus and the ankle joint angles during the stance phase of gait between individuals with chronic ankle instability (CAI) and healthy adults. The comparison was conducted using a synchronized ultrasound (US) imaging with a three-dimensional motion analysis (MA) system. This cross-sectional study included 12 participants (5 males, 7 females; age, 20.5 ± 1.8 years; height, 166.6 ± 9.4 cm; body weight, 60.2 ± 5.3 kg; body mass index, 21.7 ± 2.0 kg/m2; 16 feet) with CAI and 10 healthy controls (4 males, 6 females; age, 21.2 ± 1.6 years; height, 164.6 ± 10.5 cm; body weight, 56.8 ± 11.3 kg; body mass index, 20.8 ± 2.6 kg/m2; 20 feet). The distance between the talus and lateral malleolus during gait was significantly increased in the CAI group compared with that in the control group throughout the stance phase. The ankle dorsiflexion angle was smaller in the CAI group during the middle and terminal stance phases. Additionally, the ankle inversion angle was greater in the CAI group than in the control group. Our findings show the application of the synchronized US and MA system in the assessment of mechanical instability in CAI group, which may be used to determine treatment efficacy.

Biomechanical and Physiological Variables in Dynamic and Functional Balance Control during Single-Leg Loading in Individuals with Chronic Ankle Instability: A Scoping Review

BACKGROUND

This scoping review summarizes the tasks and outcomes in dynamic and functional balance assessments of individuals with chronic ankle instability, focusing on the physiological and biomechanical characteristics.

METHOD

A comprehensive literature search was conducted in PubMed, Scopus, Web of Science, and MEDLINE databases in September 2023 and revised in April 2024. Studies evaluating dynamic and functional balance in chronic ankle instability using clinical tests, as well as biomechanical and physiological outcomes, were included.

RESULTS

Out of 536 publications, 31 met the screening criteria. A history of ankle sprain was the main focus of the inclusion criteria (28 articles, 90%). The star excursion balance test, emphasizing maximum reach distance, was the most common quantitative task (12 articles, 66%). Physiological data mainly came from electromyography studies (7 articles, 23%), while biomechanical variables were often assessed through center of pressure studies using force plates (17 articles, 55%).

CONCLUSIONS

The preferred quantitative clinical assessment was the star excursion balance test, focusing on normalized reach outcomes. Qualitative functional balance assessments emphasize landing activities and center of pressure displacement. Electromyography is commonly used to analyze the tibialis anterior and peroneus longus muscles. However, there is a lack of qualitative data on dynamic balance control, including morphological characteristics and the center of mass adaptation.

Selective Strength Training Changes the Morphology and Ankle Strength of the Peroneus Longus and the Peroneus Brevis

This study aimed to investigate the 8-week selective training effect of the peroneus longus (PL) and the peroneus brevis (PB) on muscle morphology, echogenicity, and ankle strength and to examine post-intervention detraining effects. Twenty healthy participants without orthopedic disease in the lower extremities were assigned to either the PL intervention group (training consisted of pushing the Thera-Band® out from the ball of the foot to emphasize ankle eversion) or the PB intervention group (training consisted of pulling the Thera-Band® from the base of the fifth metatarsal to enhance ankle valgus and external rotation). Each intervention was performed three times per week for 8 weeks. The cross-sectional area (CSA), thickness, echogenicity, and ankle strength of the PL and the PB were measured before week 1 and after each training session. Detraining effects were evaluated after the 8-week intervention. The results revealed a significant interaction between within-group (week) and between-group (type of intervention) variables on CSA and ankle strength of both the PL and the PB. Over the 8-week training period, the CSA and ankle strength of the PL significantly increased in the PL intervention group, as did the CSA and ankle strength of the PB in the PB intervention group (p < 0.05). The residual effect of muscle hypertrophy was observed during the detraining period. In conclusion, 8-week selective PL and PB training interventions can increase the CSA and ankle strength of these muscles over time. Long-term selective intervention is required to improve peroneus muscle morphology and function, with separate assessments of the CSA and ankle strength of the PL and the PB.

Acute Effects of Selective Strength Exercise on the Peroneus Longus and Brevis

The peroneus muscles are muscles that mainly act in ankle eversion and can be divided into PL and PB, which have different but important roles in foot and ankle functions. Therefore, PL and PB dysfunction can lead to foot and ankle issues, making. selective strength exercise necessary. This study aimed to identify the effect of two different exercise techniques on PL and PB morphologies. Two interventions were performed on separate days: the PL intervention, in which a Thera-Band® was placed on the ball of the foot and pushed out from the contact point, and the PB intervention, in which the Thera-Band® was pulled from the base of the fifth metatarsal. Cross-sectional area (CSA) and thickness of the peroneus muscles at 25% (showing the PL morphology) and 75% (showing the PB morphology) proximal to the line connecting the fibular head and lateral malleolus, as well as ankle strength was measured before and immediately after the interventions and at 10, 20, and 30 min later. A repeated-measures two-way analysis of variance was conducted to identify differences in the effects of the interventions on the PL and PB. Main and interaction effects on CSA, thickness, and ankle strength, with a significant increase in CSA and thickness in the proximal 25% in the PL intervention and the distal 75% in the PB intervention immediately after implementation, were observed (p < 0.05). The transient increase in muscle volume due to edema immediately after exercise indicates the acute effect of exercise. The CSA and thickness of the proximal 25% in the PL intervention and the distal 75% in the PB intervention increased immediately after the intervention, indicating that these interventions can be used to selectively exercise the PL and PB.

Minimizing risk of iatrogenic nerve injury during peroneus longus tendon autograft harvest: a cadaveric study at different ankle or knee positions

PURPOSE

To evaluate the distances using ultrasound between the superficial peroneal nerve (SPN) and sural nerve along the peroneus longus tendon (PLT) autograft harvest path at different ankle or knee positions in order to minimize risk of iatrogenic nerve injury during PLT autograft harvest.

METHODS

Twenty-four fresh-frozen human cadaveric lower extremities were used to harvest a full-thickness PLT autograft with a tendon stripper. Four specimens were utilized to validate correct identification of nerves under ultrasound. Sonographically guided perineural injections were performed at the start point and end point of the PLT harvest path using coloured latex, followed by dissection with gross inspection. Using ultrasound, the distance from the peroneus brevis muscle to the sural nerve at different ankle positions (20° dorsiflexion, neutral, and 20° plantarflexion) was measured, and the distance from the end of the tendon stripper to the SPN at different knee positions (full extension and 90° flexion) was also measured. Measurements were performed by two separate observers using ImageJ software.

RESULTS

Cadaveric dissection showed the presence of latex around nerves in all four specimens. The average distance from the brevis muscle to the sural nerve increased significantly from dorsiflexion to plantarflexion. The shortest distance from the tenodesis site to the sural nerve was 5.8 ± 1.7 mm. There was no significant difference from the end of the tendon stripper to the SPN between full extension or 90° flexion of the knee.

CONCLUSION

When harvesting the PLT, it is recommended to place the ankle at plantarflexion. The knee at full extension or 90° flexion had no effect. Joint positions at the time of graft harvest should be monitored to reduce risks of iatrogenic nerve injury.