ECHO INTENSITY OF PERONEUS LONGUS IN PERSONS WITH CHRONIC ANKLE INSTABILITY

Sakai S.¹, Urabe Y.¹, Tsutsumi S.¹, Made N.¹

¹Hiroshima University, Graduate School of Biomedical & Health Sciences, Hiroshima, Japan

Background: Muscle quality as well as muscle quantity (muscle thickness: [MT]) can be evaluated using
ultrasonography. Enhanced echo intensity (EI) on an ultrasound image of skeletal muscles
represents changes in muscle quality caused by increased intramuscular noncontractile fiber
(e.g., intramuscular fibrous and adipose tissue). In addition, a previous study reported that the amount of noncontractile fiber evaluated by ultrasound was negatively correlated with muscle strength. After repeated recurrence, ankle inversion sprain ultimately can develop into chronic ankle instability (CAI), and one of the main physical impairments contributing to CAI is reportedly muscle weakness of the evertor muscles such as peroneus longus (PL). However, no previous study has examined the quality and quantity of the PL in subjects with CAI.

Purpose: To examine the muscle quality and quantity of PL in persons with CAI as well as evertor strength, and to clarify the muscle characteristics of PL.

Methods: Participants were categorized into two groups consisting of 7 men with unilateral CAI based on the International Ankle Consortium criteria (CAI group, age: 22.0±1.3 years, weight: 62.5±9.3kg) and 6 men with two healthy legs without a history of inversion sprain (control group, age: 21.8±1.5 years, weight: 61.0±10.7kg). Concentric and eccentric evertor peak torque were measured using the Biodex System 3 (Biodex Medical Systems, Inc). Isokinetic testing of the ankle evertor strength was performed at 120 °/sec, and peak torque normalized by weight was recorded. The EI and MT of PL were calculated using ultrasonography (Noblus; Hitachi, Aloka Medical) and EI was determined using computer-assisted-8-bit gray-scale analysis and the standard histogram function of Image J software (NIH). The mean EI of the regions is expressed as a value between 0 (black) and 255 (white); the higher value, the higher ratio of noncontractile fiber. Statistical analysis was performed using SPSS (SPSS Japan Inc.). The evertor strength, EI and MT were compared between the CAI and control groups using the two sample t-test. Significance level was set at 5%.

Results: There was significant difference in evertor strength between two groups (p 0.05); the respective values of concentric evertor strength (Nm/kg) were 0.34±0.11 and 0.53±0.18 in CAI and Control groups (36% decrease), and the respective values of eccentric evertor strength (Nm/kg) were 0.48±0.13 and 0.72±0.25 in CAI and Control groups (33% decrease). There was significant difference in the EI between two groups (p 0.05); EI value were 102.96±16.97 and 77.46±5.34 in CAI and control groups, respectively. There was no difference in MT between two groups; the MT values (mm) were 24.59±1.68 and 26.28±2.76 in CAI and control groups, respectively.

Conclusion(s): Although the evertor strength was significantly low in CAI group, there was no difference in MT between two groups. This study’s findings indicate that intramuscular noncontractile fiber evaluated by ultrasonography contributes to muscle weakness of PL.

Implications: This study clarified the change in muscle quality that occurs in PL in persons with CAI.

Funding acknowledgements: We have no funding acknowledgement in this study.

Topic: Sport & sports injuries

Ethics approval: All patients gave informed consent about the protocol, which was approved by the institutional ethics committee.

All authors, affiliations and abstracts have been published as submitted.