Pedobarography

Pedobarography is the study of pressure fields acting between the plantar surface of the foot and a supporting surface. Used most often for biomechanical analysis of gait and posture, pedobarography is employed in a wide range of applications including sports biomechanics and gait biometrics . The term 'pedobarography' is derived from the Latin: pedes, referring to the foot (as in: pedometer, pedestrian, etc.), and the Greek: baros meaning 'weight' and also 'pressure' (as in: barometer, barograph).

Pedobarography
Example foot pressure distribution; maximum pressures during a single step.
Test ofgait biomechanics

History

The first documented pedobarographic study was published in 1882 and used rubber and ink to record foot pressures.[1] Numerous studies using similar apparatus were conducted in the early- and mid-twentieth century,[1][2] 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.[3] It is now used widely to assess and correct a variety of biomechanical and neuropathic disorders.[4][5]

Example floor-based foot pressure measurement device.
Example insole (in-shoe) foot pressure measurement device.

Hardware

Devices fall into two main categories: (i) floor-based, and (ii) in-shoe. The underlying technology is diverse, ranging from piezoelectric sensor arrays to light refraction, [2] [4] [6] [7] [8] but 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 acting under the plantar surface of the foot. From these data other variables may be calculated (see Data analysis).

There are a few differences between the types of information you will received from these two systems, so depending on the application one system might be a better fit. For example, a floor-based system will provide spatial temporal information, like stride length that an in-shoe system cannot provide. Platform systems (or floor-based systems) will also allow for testing of patients with walking aids for assistive devices. However, there is some controversy about evaluating natural gait with a platform system due to patients potentially targeting the platform when walking. This is where an in-shoe system provides an advantage as it reduces the risk of targeting. Users should evaluate carefully the differences between the systems, the patients they will be evaluating and the type of data they are interested in when selecting a system.[9]

The spatial and temporal resolutions of the images generated by commercial pedobarographic systems range from approximately 3 to 10 mm and 25 to 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).[10] For a stance phase duration of approximately 0.6 seconds during normal walking,[11] approximately 150,000 pressure values, depending on the hardware specifications, 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.[12][13][14] These techniques have also been found to be clinically and biomechanically useful, but traditional regional analyses are most common.

The most commonly analyzed pedobarographic variable is 'peak pressure', or the maximum pressure experienced at each sensor (or pixel, if the sensors fall on a regular square grid) over the duration of the step. Other variables like contact duration, pressure-time integral, center of pressure trajectory, for example, are also relevant to the biomechanical function of the foot.

Clinical use

The most widely researched clinical application of pedobarography is diabetic foot ulceration,[15] a condition which can lead to amputation in extreme cases[16] but for which even mild-to-moderate cases are associated with substantial health care expenditure.[17] Pedobarography is also used in a variety of other clinical situations including: post-surgery biomechanical assessment,[18] intra-operative assessment,[19] orthotics design[20] and assessment of drop-foot surgery.[5] In addition to clinical applications, pedobarography continues to be used in the laboratory to understand the mechanisms governing human gait and posture.[3][7]

The use of pedobarographs in clinical settings is supported by researchers. According to Bowen, et al., "Pediobarograph measurements can be used to monitor and quantitatively assess the progressive changes of foot deformity over time. Pedobarograph is a reliable measurement that shows little variability between measurements at the same occasion and between measurements on different days."[21]

Terminology
  • Dynamic pedobarography refers to the collection and analysis of time series pedobarographic data during dynamic activities like gait.
  • Static pedobarography refers to the collection and analysis of time series pedobarographic data during postural (i.e. quasi-static) activities.

References
  1. Elftman HO (1934). "A cinematic study of the distribution of pressure in the human foot". Anat Rec. 59: 481–90. doi:10.1002/ar.1090590409.
  2. Lord M (1981). "Foot pressure measurement: a review of methodology". J Biomed Eng. 3: 91–9.
  3. Alexander IJ, Chao EY, Johnson KA (December 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 (3): 152–67. PMID 2074083.
  4. Gefen A (December 2007). "Pressure-sensing devices for assessment of soft tissue loading under bony prominences: technological concepts and clinical utilization". Wounds : a Compendium of Clinical Research and Practice. 19 (12): 350–62. PMID 25942685.
  5. Parmar B (2009). "Assessment of Foot Drop Surgery in Leprosy Subjects Using Frequency Domain Analysis of Foot Pressure Distribution Images.". 13th International Conference on Biomedical Engineering, IFMBE Proceedings. pp. 1107–1111. doi:10.1007/978-3-540-92841-6_272. ISBN 978-3-540-92840-9.
  6. Cobb J, Claremont DJ (July 1995). "Transducers for foot pressure measurement: survey of recent developments". Medical & Biological Engineering & Computing. 33 (4): 525–32. doi:10.1007/BF02522509. PMID 7475382.
  7. Rosenbaum D, Becker HP (1997). "Plantar pressure distribution measurements: technical background and clinical applications". J Foot Ankle Surg. 3: 1–14. doi:10.1046/j.1460-9584.1997.00043.x.
  8. Orlin MN, McPoil TG (April 2000). "Plantar pressure assessment". Physical Therapy. 80 (4): 399–409. doi:10.1093/ptj/80.4.399. PMID 10758524.
  9. "Guide to Choosing a Gait Analysis Solution". Tekscan.
  10. Birtane M, Tuna H (December 2004). "The evaluation of plantar pressure distribution in obese and non-obese adults". Clinical Biomechanics (Bristol, Avon). 19 (10): 1055–9. doi:10.1016/j.clinbiomech.2004.07.008. PMID 15531056.
  11. Blanc Y, Balmer C, Landis T, Vingerhoets F (October 1999). "Temporal parameters and patterns of the foot roll over during walking: normative data for healthy adults". Gait & Posture. 10 (2): 97–108. doi:10.1016/S0966-6362(99)00019-3. PMID 10502643.
  12. Chu WC, Lee SH, Chu W, Wang TJ, Lee MC (November 1995). "The use of arch index to characterize arch height: a digital image processing approach". IEEE Transactions on Bio-Medical Engineering. 42 (11): 1088–93. doi:10.1109/10.469375. PMID 7498912.
  13. Prabhu KG, Patil KM, Srinivasan S (May 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". Medical & Biological Engineering & Computing. 39 (3): 288–93. doi:10.1007/BF02345282. PMID 11465882.
  14. Shah SR, Patil KM (2005). "Processing of foot pressure images and display of an advanced clinical parameter PR in diabetic neuropathy.". Proc 9th Intl Conf Rehab Robotics. pp. 414–417. doi:10.1109/ICORR.2005.1501131.
  15. vvan Schie CH (September 2005). "A review of the biomechanics of the diabetic foot". The International Journal of Lower Extremity Wounds. 4 (3): 160–70. doi:10.1177/1534734605280587. PMID 16100097.
  16. Klenerman L, Wood B (2006). The Human Foot: A Companion to Medical Studies. Berlin: Springer.
  17. Reiber GE (March 1992). "Diabetic foot care. Financial implications and practice guidelines". Diabetes Care. 15 Suppl 1: 29–31. doi:10.2337/diacare.15.1.S29. PMID 1559416.
  18. Hahn F, Maiwald C, Horstmann T, Vienne P (January 2008). "Changes in plantar pressure distribution after Achilles tendon augmentation with flexor hallucis longus transfer". Clinical Biomechanics (Bristol, Avon). 23 (1): 109–16. doi:10.1016/j.clinbiomech.2007.08.015. PMID 17949866.
  19. 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.
  20. Hodge MC, Bach TM, Carter GM (October 1999). "novel Award First Prize Paper. Orthotic management of plantar pressure and pain in rheumatoid arthritis". Clinical Biomechanics (Bristol, Avon). 14 (8): 567–75. doi:10.1016/S0268-0033(99)00034-0. PMID 10521640.
  21. Riad J, Coleman S, Henley J, Miller F (November 2007). "Reliability of pediobarographs for paediatric foot deformity". Journal of Children's Orthopaedics. 1 (5): 307–12. doi:10.1007/s11832-007-0053-1. PMC 2656740. PMID 19308525.
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