Spatial resolution in plantar pressure measurement revisited

• Published in: Journal of biomechanics Vol. 45; no. 12; pp. 2116 - 2124
• Main Author: Pataky, Todd C.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 09.08.2012; Elsevier; Elsevier Limited
• Subjects: Accuracy; Adult; Biological and medical sciences; Biomechanics; Distributed load; Female; Foot biomechanics; Fundamental and applied biological sciences. Psychology; Humans; Male; Mathematical analysis; Mathematical models; Measurement accuracy; Metatarsus - physiology; Models, Biological; Pedobarography; Physical Medicine and Rehabilitation; Plantar pressure; Posture - physiology; Pressure; Sensors; Spatial resolution; Tasks; Vertebrates: body movement. Posture. Locomotion. Flight. Swimming. Physical exercise. Rest. Sports; Walking - physiology; Distributed load; Foot biomechanics; Measurement accuracy; Pedobarography; Biomechanics; Foot sole; Locomotion; Walking; Pressure measurement; Spatial resolution; Biomedical engineering; Foot
• ISSN: 0021-9290; 1873-2380; 1873-2380
• DOI: 10.1016/j.jbiomech.2012.05.038

Plantar pressures are typically measured using sensors of finite area, so the accuracy with which one can measure true maximum pressure is dependent on sensor size. Measurement accuracy has been modeled previously for one patient's metatarsals (Lord, 1997), but has not been modeled either for general subjects or for other parts of the foot. The purposes of this study were (i) to determine whether Lord's (1997) model is also valid for heel and hallux pressures, and (ii) to examine how sensor size relates to measurement accuracy in the context of four factors common to many measurement settings: pressure pulse size, foot positioning, pressure change quantification, and gross pressure redistribution. Lord's (1997) model was first generalized and was then validated using 10 healthy walking subjects, with relatively low RMSE values on the order of 20kPa. Next, postural data were used to show that gross pressure redistributions can be accurately quantified (p<0.002), even with rather gross sensor sizes of 30mm. Finally, numerical analyses revealed that the relation between sensor size and measurement accuracy is highly complex, with deep dependency on the measurement context. In particular, the critical sensor widths required to achieve 90% accuracy ranged from 1.7mm to 17.4mm amongst the presently investigated scenarios. Since measurement accuracy varies so extensively with so many factors, the current results cannot yield specific recommendations regarding spatial resolution. It is concluded simply that no particular spatial resolution can yield a constant measurement accuracy across common plantar pressure measurement tasks.