Background : Plantar fascia (PF) thickness measured by ultrasound is the length from anterior edge of inferior calcaneal border vertically to superficial aspect (=lower margin) of PF. True insertion site of PF tend to locate posterior to the anterior edge. Therefore, the conventional values can be different from its real thickness. The aim of this study was to compare the PF thickness measured by conventional method to its real thickness.
Methods : 99 feet of 50 healthy adults without foot pain were measured. Unlike conventional method measuring PF thickness from the anterior edge (conventional thickness group=CT), subjects were assessed by detecting thickness from upper margin of plantar fascia (real thickness group=RT) (Figure 1). These parameters were measured in long and short axis views when the fascia was in relax. The same process was done when plantar fascia was in stretched position.
Results : In relaxed feet, CT and RT values were obtained in long and short axis views. CT values were significantly larger than RT values (p<0.05) in long axis views (CT: 3.6±0.7mm vs RT: 2.8±0.5mm). Also, CT values were significantly larger in short axis views (CT: 3.4±0.7mm vs RT: 2.8±0.6mm). There was no significant difference between CT and RT values in accordance with axis of ultrasound. Also, effect of stretching PF on its thickness was evaluated. CT values were significantly larger when PF was stretched (Rest: 3.6±0.7mm vs Stretched: 3.8±0.7mm)(p<0.05). However, stretching PF did not affect RT values, which means it’s more constant than CT values.
Conclusion : Conventional method for measuring PF thickness is widely accepted. However, this method can be disorienting as it cannot reflect the real thickness of PF. In this study, RT values were constant regardless of patient’s foot position or ultrasound views. New method for detecting thickness by using other anatomical landmark is considerable.
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