title: Biomechanics of the heel pad for type 2 diabetic patients.
abstract: OBJECTIVE
  To quantify the dynamic behavior of the heel pad in type 2 diabetic patients and age-matched healthy individuals using mathematical modeling.
  
  
  BACKGROUND
  No single parameter can fully describe the heel-pad biomechanical properties during the loading-unloading process.
  
  
  METHODS
  A descriptive study using pseudoelastic modeling was conducted to simulate the heel-pad stress-strain relationship in the loaded and unloaded states. Transmission electron microscope was used to examine six heel specimens taken from amputated legs in diabetic and non-diabetic patients.
  
  
  METHODS
  Energy dissipation ratio, loading curvature, and unloading curvature were calculated from the stress-strain curve-fits. Differences in ultrastructure between the heel pad of healthy subjects and those with diabetes were described.
  
  
  RESULTS
  The diabetic patients had a significantly higher mean energy dissipation ratio (mean 36.1% (SD, 8.7%) vs mean 27.9% (SD, 6.1%); P<0.001) and mean unloaded curvatures (mean 11.8 (SD, 5.1) vs mean 8.46 (SD, 2.6); P<0.001) than those of the control group. The collagen fibrils in diabetic heel samples were ruptured with unclear striation and uneven distribution.
  
  
  CONCLUSIONS
  The curvature parameters may explain the poor rebound phenomenon resulting in the high impact energy in diabetic heel pads. Breakdown in collagen fibrils may be responsible for this observation.
  
  
  CONCLUSIONS
  These findings can be integrated into the fabrication of orthotics that dissipate excessive heel impact energy and protect against injury.
authors.affiliation: Department of Rehabilitation Medicine, Chang Gung Memorial Hospital, Tao-Yuan, Taiwan, ROC.
authors.forename: Tsz-Ching
authors.initials: TC
authors.lastname: Hsu
authors.forename: Ying-Shiung
authors.initials: YS
authors.lastname: Lee
authors.forename: Yio-Wha
authors.initials: YW
authors.lastname: Shau
mesh_terms: D000273:Adipose Tissue / Q000503:physiopathology* / Q000648:ultrastructure*; D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D016009:Chi-Square Distribution; D003094:Collagen / Q000648:ultrastructure*; D003924:Diabetes Mellitus, Type 2 / Q000503:physiopathology; D017719:Diabetic Foot / Q000503:physiopathology*; D005260:Female; D005684:Gait / Q000502:physiology*; D006365:Heel / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008854:Microscopy, Electron; D008875:Middle Aged; D012016:Reference Values; D018570:Risk Assessment; D012494:Sampling Studies; D012680:Sensitivity and Specificity; D013314:Stress, Mechanical; D016474:Weight-Bearing
chemical_list: D003094:Collagen