Flexibility of the transverse arch of the forefoot.

Purpose: To measure the percentage of the transverse arch length (%TAL) in 2 positions using a 3-dimensional motion capture system to determine the flexibility of the transverse arch of the forefoot.

Methods: 19 men and 10 women with no lower extremity injury or deformity were included. The %TAL of the left foot was measured using a digital caliper in the standing position and the lower leg maximum anterior tilting (LMAT) position. The difference in the %TAL between the 2 positions (δ%TAL) was calculated. 10 markers were mounted on skin over each metatarsal head and base of the left foot. Motion was captured using a 3-dimensional motion capture system. Coordinates of each marker were manually digitised. The percentage of the transverse arch height (%TAH) and angle between the first and fifth metatarsals (M1M5) were calculated, and differences in each forefoot parameter in the 2 positions were defined as δ%TAL, δ%TAH, δM1M5, and the fore foot flexibility magnitude (FFM) was calculated. Subjects were divided into 3 groups based on their δ%TAL: <25th percentile (hypo-flexibility group, n=7), >26th percentile to <74th percentile (control group, n=15), and >75th percentile (hyperflexibility group, n=7). The 3 groups were compared in terms of the δ%TAL. δ%TAH, δM1M5, and FFM.

Results: The δ%TAL correlated with δM1M5 (r=0.61, p<0.001) and FFM (r=0.60, p=0.001). For the δM1M5, the hyper-flexibility group differed significantly from other groups (p=0.01). For the FFM, the hyperflexibility group differed significantly from the hypoflexibility group (p=0.02).

Conclusion: Measurement of the %TAL in both the standing and LMAT positions provides a simple and quantitative method of assessing the flexibility of the transverse arch of the forefoot.