Abstract
Objective: Chronic ankle instability (CAI) is a debilitating condition, limiting physical activity in the affected 20% of the general population. The lateral leg muscles, fibularis longus (FL) and brevis (FB) are important stablisers of the ankle joint and therefore may be implicated in CAI. However, the relationship between the architecture of these muscles and the aetiology of CAI are not well understood, as detailed accounts of the anatomical parameters of these muscles are limited. This study aims to define the detailed architecture and innervation patterns of FL and FB.
Methods: Twelve cadaveric limbs (male, mean ± SD age 77.8± 7.9 years) were dissected and whole musculotendon parameters measured. Pennation angle (PA), length and mass (FM) of individual fascicles were measured to determine muscle volume and physiological cross-sectional area (PCSA), and nerve entry points (NEPs) were recorded. Muscles were digitised for post-dissection analysis.
Results: Mean musculotendinous junction lengths were 23 ± 2.9cm (FL) and 19.6 ± 3.2cm (FB). PA for FL was 7.8 ± 4.4° and 9.5±5.2° for FB. Fascicle length was similar for both muscles (FL, 4.4 ± 0.8 cm; FB, 3.9 ± 0.7 cm). FL (36.25 ± 10.3 g) was approximately twice as large as FB (17.3 ± 6.0 g), comparable to mean PCSA (FL, 7.7 ± 2.4cm2; FB, 4.1 ± 1.8 cm2). Mean number of NEPs for FL and FB were 5.1 ± 1.1 and 2.1 ± 0.9, respectively.
Conclusion: This research provides a better understanding of the anatomy of FL and FB. Innervation patterns are important for determining whether different muscle sections have different functions. These baseline data may inform future studies focused on the cause and management of CAI.