Pedobarography

Foot pressure parameters, such as peak plantar pressure and pressure–time integrals, were measured using pedobarography (Tekscan, Inc., Boston, MA, USA). Based on previous studies [9 (link),22 (link)], the peak pressure and pressure–time integrals were calculated for each of the five foot segments. Peak pressure is defined as the maximum pressure (KPa) in each of the three areas (forefoot, midfoot, and rearfoot) during gait. The pressure–time integral is defined as the time integral of the mean pressure (Ns) in each of the three areas (forefoot, midfoot, and rearfoot) during gait. Previous studies have shown that pressure–time integrals may be better indicators of foot function than peak pressure [23 (link),24 (link)]. All patients practiced stepping on the pressure platform in three steps with the affected foot while walking for 2 m, followed by 3 times assessment. The ICC for the peak plantar pressure was 0.77.

Foot pressure was measured by pedobarography [5 (link), 20 (link), 21 (link)] (Tekscan, Massachusetts) during a 2-m walk and recorded at 50 Hz. Based on a previous study, [21 (link)] the peak pressure and pressure–time integral were calculated for each of the 5 segments of the foot (Fig. 3): the medial forefoot (MFF), lateral forefoot (LFF), medial midfoot (MMF), lateral midfoot (LMF), and heel. These data were processed to yield the valgus/varus index (VV index, %), which is defined as ((MMF + MFF) - (LMF + LFF))/(MMF + MFF + LFF + LMF), with plus (+) and minus (−) values of the VV index indicating hindfoot valgus and varus, respectively [21 (link)]. The same peak pressure and VV index assessment processes were used for the normal controls.
Fig. 3

Five segments on pedobarography: the medial forefoot (MFF), lateral forefoot (LFF), medial midfoot (MMF), lateral midfoot (LMF), and heel. This image shows hindfoot valgus with increased pressure in the forefoot and hindfoot

Foot pressure was measured using pedobarography (Tekscan, MA, USA) and recorded at 50 Hz while walking for 2 m. All participants were evaluated after stepping on the pressure platform for three steps on the affected foot while walking the 2 m distance. The foot pressure parameters were evaluated using the pressure–time integral (PTI).
PTI was defined as the time integral of the mean pressure (N/cm² s) in each of the three areas (forefoot, midfoot, and rearfoot) during walking^{18 (link)}, and is a better indicator than peak pressure¹⁹ .
Foot posture was assessed using the foot arch index (AI)^{9 (link),20 (link)}. The foot AI was calculated as the entire footprint area divided by the area of the middle third of the footprint (AI = B/A + B + C), and has demonstrated acceptable reliability and validity.^{20 (link)} Based on a previous study^{20 (link)}, the cut-off scores for foot AI were defined as follows: high-arched (< 0.21), normal (0.21–0.28), and low-arched (> 0.28). The high- and low-foot AI scores were defined as low-arched and high-arched foot postures, respectively, in the present study.