Pedobarography

Pedobarography is the study of the pressure fields that act between the plantar surface of the foot and a supporting surface. Pedobarographic analyses are typically conducted for the clinical / biomechanical evaluation of: gait, posture, and sports movements. The term 'pedobarography' is derived from the Latin: "pedes", referring to the foot (as in: pedometer, pedestrian; see Ped-), and the Greek: "baros" meaning 'weight' and also 'pressure' (as in: barometer, barograph).

History

The first documented pedobarographic study was published in 1882 and used a rubber-and-ink apparatus to record maximal pressures across the plantar surface of the foot (cited in Elftman 1934). Numerous studies using similar apparatus were conducted in the early and mid twentieth century (reviewed in Lord 1981), but it was not until the advent of the personal computer that electronic apparatus were developed and that pedobarography became practical for routine clinical use (Alexander et al 1990). It is now used widely to assess and correct a variety of biomechanical and neuropathic disorders (Gefen 2007).

Hardware

Modern pedobarographic technology is diverse, ranging from piezoelectric sensor arrays to critical light reflection (reviewed in Lord 1981, Alexander et al 1990, Cobb and Claremont 1995, Rosenbaum and Becker 1997, Orlin and McPoil 2000, Gefen 2007). The ultimate form of the data generated by all modern technologies is either a 2D image or a 2D image time series of the pressures under the plantar surface of the foot. From these data other variables may be calculated (see Data analysis).

The spatial and temporal resolutions of the images generated by commercial pedobarographic systems are on the order of 5 mm and 500 Hz, respectively. Finer resolution is limited by sensor technology. Such resolutions yield a contact area of approximately 500 sensors (for a typical adult human foot with surface area of approximately 100 cm²; Birtane and Tuna 2004). For a stance phase duration of approximately 0.6 seconds during normal walking (Blanc et al 1999), approximately 150,000 pressure values are recorded for each step.

Data analysis

To deal with the large volume of data contained in each pedobarographic record, traditional analyses reduce the data to a more manageable size in three stages: (1) Produce anatomical or regional masks, (2) Extract regional data, and (3) Run statistical tests. Results are typically reported in tabular or bar graph formats. There are also a number of alternative analysis techniques derived from digital image processing methodology: (e.g. Chu et al. 1995, Prabhu et al. 2001, Shah and Patil, 2005). These techniques have also been found to be clinically and biomechanically useful, but traditional regional analysis continues to dominate the literature.

Irrespective of methodology, the most commonly analyzed pedobarographic images are peak pressure images. These consist of the maximal pressure values observed at each sensor (pixel) over the measurement duration. Other variables (e.g. contact duration, pressure-time integral, center of pressure trajectory, etc.) are also relevant to the biomechanical function of the foot but are less commonly assessed.

Clinical Use

The most widely researched clincal application of pedobarography is diabetic foot ulceration (van Schie 2005), a condition which can lead to amputation in extreme cases (Klenerman and Wood 2006) but for which even mild-to-moderate cases are associated with substantial health care expenditure (Reiber 1992). Pedobarography is also used in a variety of other clinical situations including: post-surgery biomechanical assessment (e.g. Hahn et al 2008), intra-operative assessment (e.g. Richter et al 2006), and orthotics design (e.g. Hodge et al 1999). In addition to clinical applications, pedobarography continues to be used in the laboratory to understand the mechanisms governing human gait and posture (Alexander et al 1990, Rosenbaum and Becker 1997).

Terminology

"Dynamic pedobarography" refers to the collection and analysis of time series pedobarographic data during gait.

"Static pedobarography" refers to the collection and analysis of time series pedobarographic data during postural activities.

Review articles

Alexander et al. 1990

Cobb J and Claremont D J 1995

Gefen 2007

Lord 1981

Orlin and McPoil 2000

Patil et al. 2002

Razeghi and Batt 2002

Rosenbaum and Becker 1997

Normative data

Blanc et al. 1999.

De Cock et al. 2005.

Hutton and Dhanendran 1979.

Putti et al. 2007.

References

Alexander IJ, Chao EY, Johnson KA 1990. The assessment of dynamic foot-to-ground contact forces and plantar pressure distribution: a review of the evolution of current techniques and clinical applications. Foot Ankle 11 152-67.

Birtane M, Tuna H 2004. The evaluation of plantar pressure distribution in obese and non-obese adults. Clin Biomech 19 1055-9.

Blanc Y, Balmer C, Landis T, Vingerhoets F 1999. Temporal parameters and patterns of the foot roll over during walking: normative data for healthy adults. Gait Posture 10 97-108.

Chu WC, Lee SH, Chu W, Wang TJ, Lee MC 1995. The use of arch index to characterize arch height: a digital image processing approach. IEEE Trans Biomed Eng 42(11) 1088-93.

Cobb J, Claremont DJ 1995. Transducers for foot pressure measurement: survey of recent developments. Med Biol Eng Comput 33 525-32.

De Cock A, De Clercq D, Willems T, Witvrouw E 2005. Temporal characteristics of foot roll-over during barefoot jogging: reference data for young adults. Gait Posture 21 432-9.

Elftman HO 1934. A cinematic study of the distribution of pressure in the human foot. Anat Rec 59 481-90.

Gefen A 2007. Pressure-sensing devices for assessment of soft tissue loading under bony prominences: technological concepts and clinical utilization. Wounds 19 350-62.

Hahn F, Maiwald C, Horstmann T, Vienne P 2008. Changes in plantar pressure distribution after Achilles tendon augmentation with flexor hallucis longus transfer. Clin Biomech 23 109-16.

Hodge MC, Bach TM, Carter GM 1999. Orthotic management of plantar pressure and pain in rheumatoid arthritis. Clin Biomech 14 567-75.

Hutton WC, Dhanendran M 1979. A study of the distribution of load under the normal foot during walking. Intl Orthop 3 153-7.

Klenerman L, Wood B 2006. The Human Foot: A Companion to Medical Studies. Berlin, Springer.

Lord M 1981. Foot pressure measurement: a review of methodology. J Biomed Eng 3 91-9.

Orlin MN, McPoil TG 2000. Plantar pressure assessment. Phys Ther 80 399-409.

Patil KM, Charanya G, Prabhu KG 2002. Optical pedobarography for assessing neuropathic feet in diabetic patients--a review. Intl J Low Extrem Wounds 1(2) 93-103.

Prabhu KG, Patil KM, Srinivasan S 2001. Diabetic feet at risk: a new method of analysis of walking foot pressure images at different levels of neuropathy for early detection of plantar ulcers. Med Biol Eng Comput 39 288-93.

Putti AB, Arnold GP, Cochrane LA, Abboud RJ 2007. Normal pressure values and repeatability of the Emed1 ST4 system. Gait Potsure in press.

Razeghi M, Batt ME 2002. Foot type classification: a critical review of current methods. Gait Posture 15 282-91.

Richter M, Frink M, Zech S, Geerling J, Droste P, Knobloch K, Krettek C 2006. Technique for intraoperative use of pedobarography. Tech Foot Ankle Surg 5 88-100.

Reiber GE 1992. Diabetic foot care: financial implications and practice guidelines. Diabetes Care 15(S1) 29-31.

Rosenbaum D, Becker HP 1997. Plantar pressure distribution measurements: technical background and clinical applications. J Foot Ankle Surg 3 1-14.

van Schie CHM 2005. A review of the biomechanics of the diabetic foot. Int J Low Extrem Wounds 4 160-70.

Shah SR, Patil KM 2005. Processing of foot pressure images and display of an advanced clinical parameter PR in diabetic neuropathy. In: Proc 9th Intl Conf Rehab Robotics 414-417.