Shear forces under the human foot are thought to be responsible for various foot pathologies such as diabetic plantar ulcers and athletic blisters. Frictional shear forces might also play a role in the metatarsalgia observed among hallux valgus (HaV) and rheumatoid arthritis (RA) patients. Due to the absence of commercial devices capable of measuring shear stress distribution, a number of linear models were developed. All of these have met with limited success. This study used nonlinear methods, specifically neural network and fuzzy logic schemes, to predict the distribution of plantar shear forces based on vertical loading parameters. In total, 73 subjects were recruited; 17 had diabetic neuropathy, 14 had HaV, 9 had RA, 11 had frequent foot blisters, and 22 were healthy. A feed-forward neural network (NN) and adaptive neurofuzzy inference system (NFIS) were built. These systems were then applied to a custom-built platform, which collected plantar pressure and shear stress data as subjects walked over the device. The inputs to both models were peak pressure, peak pressure-time integral, and time to peak pressure, and the output was peak resultant shear. Root-mean-square error (RMSE) values were calculated to test the models’ accuracy. RMSE/actual shear ratio varied between 0.27 and 0.40 for NN predictions. Similarly, NFIS estimations resulted in a 0.28–0.37 ratio for local peak values in all subject groups. On the other hand, error percentages for global peak shear values were found to be in the range 11.4–44.1. These results indicate that there is no direct relationship between pressure and shear magnitudes. Future research should aim to decrease error levels by introducing shear stress dependent variables into the models.

1.
Brand
,
P. W.
, and
Hall
,
O. C.
, 1979, “
The Etiology of the Neuropathic Plantar Ulcer
,”
J. Am. Podiatry Assoc.
0003-0538,
69
(
3
), pp.
173
177
.
2.
Davis
,
B. L.
, 1993, “
Foot Ulceration: Hypotheses Concerning Shear and Vertical Forces Acting on Adjacent Regions of Skin
,”
Med. Hypotheses
0306-9877,
40
(
1
), pp.
44
47
.
3.
Cua
,
A. B.
,
Wilhelm
,
K. P.
, and
Maibach
,
H. I.
, 1990, “
Frictional Properties of Human Skin: Relation to Age, Sex and Anatomical Region, Stratum Corneum Hydration and Transepidermal Water Loss
,”
Br. J. Dermatol.
0007-0963,
123
(
4
), pp.
473
479
.
4.
Fuhrmann
,
R. A.
,
Roth
,
A.
, and
Venbrocks
,
R. A.
, 2005, “
Metatarsalgia: Differential Diagnosis and Therapeutic Algorithm
,”
Orthopade
0085-4350,
34
(
8
), pp.
767
775
.
5.
Frykberg
,
R. G.
,
Zgonis
,
T.
,
Armstrong
,
D. G.
,
Driver
,
V. R.
,
Giurini
,
J. M.
,
Kravitz
,
S. R.
,
Landsman
,
A. S.
,
Lavery
,
L. A.
,
Moore
,
J. C.
,
Schuberth
,
J. M.
,
Wukich
,
D. K.
,
Andersen
,
C.
, and
Vanore
,
J. V.
, 2006, “
Diabetic Foot Disorders: A Clinical Practice Guideline (2006 Revision)
,”
J. Foot Ankle Surg.
1067-2516,
45
(
5
), pp.
S1
S66
.
6.
Veves
,
A.
,
Murray
,
H. J.
,
Young
,
M. J.
, and
Boulton
,
A. J.
, 1992, “
The Risk of Foot Ulceration in Diabetic Patients With High Foot Pressure: A Prospective Study
,”
Diabetologia
0012-186X,
35
(
7
), pp.
660
663
.
7.
Armstrong
,
D. G.
,
Peters
,
E. J.
,
Athanasiou
,
K. A.
, and
Lavery
,
L. A.
, 1998, “
Is There a Critical Level of Plantar Foot Pressure to Identify Patients at Risk for Neuropathic Foot Ulceration?
J. Foot Ankle Surg.
1067-2516,
37
(
4
), pp.
303
307
.
8.
Brennan
,
F. H.
, Jr.
, 2002, “
Managing Blisters in Competitive Athletes
.”
Current Sports Medicine Reports
,
1
(
6
), pp.
319
322
.
9.
Taylor
,
C. M.
,
Riordan
,
F. A.
, and
Graham
,
C.
, 2006, “
New Football Boots and Toxic Shock Syndrome
,”
BMJ
0959-8138,
332
(
7554
), pp.
1376
1378
.
10.
Knapik
,
J. J.
,
Hamlet
,
M. P.
,
Thompson
,
K. J.
, and
Jones
,
B. H.
, 1996, “
Influence of Boot-Sock Systems on Frequency and Severity of Foot Blisters
,”
Mil. Med.
0026-4075,
161
(
10
), pp.
594
598
.
11.
Spence
,
W. R.
, and
Shields
,
M. N.
, 1968, “
Prevention of Blisters, Callosities and Ulcers by Absorption of Shear Forces
,”
J. Am. Podiatry Assoc.
0003-0538,
58
(
10
), pp.
428
434
.
12.
Hodge
,
M. C.
,
Bach
,
T. M.
, and
Carter
,
G. M.
, 1999, “
Novel Award First Prize Paper: Orthotic Management of Plantar Pressure and Pain in Rheumatoid Arthritis
,”
Clin. Biomech. (Bristol, Avon)
0268-0033,
14
(
8
), pp.
567
575
.
13.
van der Leeden
,
M.
,
Steultjens
,
M.
,
Dekker
,
J. H.
,
Prins
,
A. P.
, and
Dekker
,
J.
, 2006, “
Forefoot Joint Damage, Pain and Disability in Rheumatoid Arthritis Patients With Foot Complaints: The Role of Plantar Pressure and Gait Characteristics
,”
Rheumatology
0080-2727,
45
(
4
), pp.
465
469
.
14.
Abuzzahab
,
F. S.
, Jr.
,
Harris
,
G. F.
, and
Kidder
,
S. M.
, 1997, “
A Kinetic Model of the Foot and Ankle
,”
Gait and Posture
0966-6362,
5
(
2
), p.
148
.
15.
Giacomozzi
,
C.
, and
Macellari
,
V.
, 1997, “
Piezo-Dynamometric Platform for a More Complete Analysis of Foot-to-Floor Interaction
,”
IEEE Trans. Rehabil. Eng.
1063-6528,
5
(
4
), pp.
322
330
.
16.
Yavuz
,
M.
,
Botek
,
G.
, and
Davis
,
B. L.
, 2007, “
Plantar Shear Stress Distributions: Comparing Actual and Predicted Frictional Forces at the Foot-Ground Interface
,”
J. Biomech.
0021-9290,
40
, pp.
3045
3049
.
17.
Tu
,
J. V.
, 1996, “
Advantages and Disadvantages of Using Artificial Neural Networks Versus Logistic Regression for Predicting Medical Outcomes
,”
J. Clin. Epidemiol.
0895-4356,
49
(
11
), pp.
1225
1231
.
18.
Schollhorn
,
W. I.
, 2004, “
Applications of Artificial Neural Nets in Clinical Biomechanics
,”
Clin. Biomech. (Bristol, Avon)
0268-0033,
19
, pp.
876
898
.
19.
Savelberg
,
H. H. C. M.
, and
de Lange
,
A. L. H.
, 1999, “
Assessment of the Horizontal, Fore-Aft Component of the Ground Reaction Force From Insole Pressure Patterns by Using Artificial Neural Networks
,”
Clin. Biomech. (Bristol, Avon)
0268-0033,
14
, pp.
585
592
.
20.
Boostani
,
R.
, and
Moradi
,
M. H.
, 2003, “
Evaluation of Forearm EMG Signal Features for the Control of Prosthetic Hand
,”
Clin. Phys. Physiol. Meas.
0143-0815,
24
(
2
), pp.
309
319
.
21.
Guler
,
I.
, and
Ubeyli
,
E. D.
, 2004, “
Application of Adaptive Neuro-Fuzzy Inference System for Detection of Electrocardiographic Changes in Patients With Partial Epilepsy Using Feature Extraction
,”
Expert Sys. Applic.
0957-4174,
27
, pp.
323
330
.
22.
Giansanti
,
D.
, and
Maccioni
,
G.
,
et al.
, 2008, “
Assessment of Fall-Risk by Means of a Neural Network Based on Parameters Assessed by a Wearable Device During Posturography
,”
Med. Eng. Phys.
1350-4533,
30
(
3
), pp.
367
372
.
23.
Park
,
H.
, and
Durand
,
D. M.
, 2006, “
Frequency Sensitive Motion Control for a Single Joint Arm Model
,”
Conference Proceedings IEEE Enginering in Medicine and Biology Society
,
1
, pp.
5416
5419
.
24.
Manoonpong
,
P.
, and
Genq
,
T.
,
et al.
, 2007, “
Adaptive Fast Walking in a Biped Robot Under Neuronal Control and Learning
,”
PLOS Comput. Biol.
1553-734X,
3
(
7
), pp.
1305
1320
.
25.
Davis
,
B. L.
,
Perry
,
J. E.
,
Neth
,
D. C.
, and
Waters
,
K. C.
, 1998, “
A Device for Simultaneous Measurement of Pressure and Shear Force Distribution on the Plantar Surface of the Foot
,”
J. Appl. Biomech.
1065-8483,
14
, pp.
93
104
.
26.
Mcpoil
,
T. G.
,
Cornwall
,
M. W.
,
Dupuis
,
L.
, and
Cornwell
,
M.
, 1999, “
Variability of Plantar Pressure Data: A Comparison of the Two-Step and Midgait Methods
,”
J. Am. Podiatr. Med. Assoc.
8750-7315,
89
(
10
), pp.
495
501
.
27.
Jang
,
J.
, 1993, “
ANFIS: Adaptive Network-Based Fuzzy Inference Systems
,”
IEEE Trans. Syst. Man Cybern.
0018-9472,
23
, pp.
665
685
.
28.
Zhang
,
K.
,
Sun
,
M.
,
Lester
,
D. K.
,
Pi-Sunyer
,
F. X.
,
Boozer
,
C. N.
, and
Longman
,
R. W.
, 2005, “
Assessment of Human Locomotion by Using an Insole Measurement System and Artificial Neural Networks
,”
J. Biomech.
0021-9290,
38
, pp.
2276
2287
.
29.
Subasi
,
A.
, 2007, “
Application of Adaptive Neuro-Fuzzy Inference System for Epileptic Seizure Detection Using Wavelet Feature Extraction
,”
Comput. Biol. Med.
0010-4825,
37
(
2
), pp.
227
244
.
30.
Assaleh
,
K.
, 2007, “
Extraction of Fetal Electrocardiogram Using Adaptive Neuro-Fuzzy Inference Systems
,”
IEEE Trans. Biomed. Eng.
0018-9294,
54
(
1
), pp.
59
68
.
You do not currently have access to this content.