Abnormal lateral malleolus morphology and its association with physical function in Japanese adolescent competitive athletes; Cross-sectional study.

BACKGROUND

Avulsion fractures of the lateral malleolus, detected as abnormal lateral malleolus morphology (ALM), occur concomitantly with lateral ankle sprain (LAS) in children and adolescents. We hypothesized that structural changes in the ankle joint due to ALM may contribute to deterioration in dynamic balance function.

RESEARCH QUESTION: What are the differences in physical function between competitive adolescent athletes with and without ALM, and what factors influence dynamic postural stability on landing, a critical physical function associated with LAS?

METHODS

This is the cross-sectional study. Among the participants enrolled, 134 feet were categorized into a non-ALM group, whereas 36 feet were assigned to the ALM group. Foot alignment including medial longitudinal arch and transvers arch, ankle dorsiflexion range of motion, intrinsic foot muscle and plantar fascia morphology, toe flexor strength, and dynamic postural stability index (DPSI) were compared between the two groups. Additionally, regression analysis was employed to identify parameters influencing the dynamic postural stability in each group.

RESULTS

The ALM group exhibited wider foot widths, more pronounced transverse arch spreads, reduced ankle dorsiflexion range of motion, thickened plantar fascia, lower toe flexor strength, and decreased dynamic postural stability (p < 0.05, respectively). Multiple regression analysis indicated that decreased ankle dorsiflexion angle was associated with DPSI in both groups, and the wider transverse arch of ALM group was related to DPSI (p < 0.05, respectively).

SIGNIFICANCE: The lowered transverse arch emerged as a specific feature of ALM group associated with their decreasing dynamic postural instability. Athletes with ALM may be at higher risk of LAS due to poor foot alignment and limited ankle joint range of motion, leading to reduced shock absorption during landing. This study provides crucial keys for the critical focus regarding the physical screening of athletes.