Changes in the shear plantar soft tissue properties with diabetes are believed to play a role in plantar ulceration, yet little is known about these properties. Our group recently conducted shear tests on specimens previously tested in compression to fully characterize the tissue under both these loading modes. However, previously tested specimens may not necessarily provide representative mechanical properties as prior testing may have altered the tissue to an unknown extent. Thus, the purpose of this study was to test the effect of prior compression testing on both the plantar soft tissue shear and compressive properties using paired specimens. First, one specimen from each pair was subject to compression using our standard protocol with modifications to compare compressive properties before and after the protocol while the other specimen from each pair was left untested. Then, both specimens (i.e., one previously compression tested and one previously untested) were subject to shear testing. The results indicate that prior compression testing may affect the tissue compressive properties by reducing peak stress and modulus; however, additional testing is needed since these results were likely confounded by stress softening effects. In contrast, neither the elastic nor the viscoelastic plantar soft tissue shear properties were affected by prior testing in compression, indicating that previously compression tested specimens should be viable for use in future shear tests. However, these results are limited given the small sample size of the study and the fact that only nondiabetic specimens were examined.

References

1.
Van Schie
,
C. H.
,
2005
, “
A Review of the Biomechanics of the Diabetic Foot
,”
Int. J. Low Extrem. Wounds
,
4
, pp.
160
170
.10.1177/1534734605280587
2.
Pai
,
S.
, and
Ledoux
,
W. R.
,
2010
, “
The Compressive Mechanical Properties of Diabetic and Non-Diabetic Plantar Soft Tissue
,”
J. Biomech.
,
43
, pp.
1754
1760
.10.1016/j.jbiomech.2010.02.021
3.
Pai
,
S.
, and
Ledoux
,
W. R.
,
2011
, “
The Quasi-Linear Viscoelastic Properties of Diabetic and Non-Diabetic Plantar Soft Tissue
,”
Ann. Biomed. Eng.
,
39
, pp.
1517
1527
.10.1007/s10439-011-0263-z
4.
Wang
,
Y.-N.
,
Lee
,
K.
, and
Ledoux
,
W. R.
,
2011
, “
Histomorphological Evaluation of Diabetic and non-Diabetic Plantar Soft Tissue
,”
Foot Ankle Int.
,
32
, pp.
802
810
.10.3113/FAI.2011.0802
5.
Pai
,
S.
, and
Ledoux
,
W. R.
,
2012
, “
The Shear Mechanical Properties of Diabetic and Non-Diabetic Plantar Soft Tissue
,”
J. Biomech.
,
45
, pp.
364
370
.10.1016/j.jbiomech.2011.10.021
6.
R-Development-Core-Team
,
2010
, “
R: A Language and Environment for Statistical Computing
,”
R Foundation for Statistical Computing
,
Vienna, Austria
.
7.
De Clercq
,
D.
,
Aerts
,
P.
, and
Kunnen
,
M.
,
1994
, “
The Mechanical Characteristics of the Human Heel Pad During Foot Strike in Running: An In Vivo Cineradiographic Study
,”
J. Biomech.
,
27
, pp.
1213
1222
.10.1016/0021-9290(94)90275-5
8.
Ledoux
,
W. R.
, and
Blevins
,
J. J.
,
2007
, “
The Compressive Material Properties of the Plantar Soft Tissue
,”
J. Biomech.
,
40
, pp.
2975
2981
.10.1016/j.jbiomech.2007.02.009
9.
Miller-Young
,
J. E.
,
Duncan
,
N. A.
, and
Baroud
,
G.
,
2002
, “
Material Properties of the Human Calcaneal Fat Pad in Compression: Experiment and Theory
,”
J. Biomech.
,
35
, pp.
1523
1531
.10.1016/S0021-9290(02)00090-8
10.
Horgan
,
C. O.
,
Ogden
,
R. W.
, and
Saccomandi
,
G.
,
2004
, “
A Theory of Stress Softening of Elastomers Based on Finite Chain Extensibility
,”
Proc. R. Soc. London, Ser. A
,
460
, pp.
1737
1754
.10.1098/rspa.2003.1248
11.
Chaudhuri
,
O.
,
Parekh
,
S. H.
, and
Fletcher
,
D. A.
,
2007
, “
Reversible Stress Softening of Actin Networks
,”
Nature
,
445
, pp.
295
298
.10.1038/nature05459
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