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.