A.
Subjects
Eight subjects affected with Type II diabetes (4M-4F,
55-80 years) and 8 controls (5F-3M,
60-76 years) were enrolled in this study.
The subjects’ characteristics are reported in Table 1.
Both feet of each subject were considered so that 32 heels were investigated.
All subjects declared to have never had injuries/trauma to any of the feet.
All participants were volunteers and were informed about the conditions of the test that involved no harmful procedures or physical pain.
Before starting the experimental procedure (which included B-Mode ultrasound - US - and sonoelastography - ElaXto),
each volunteer was asked to give information about age,
weight,
height,
nature of physical activity and hours per week,
shoe size and,
in case of diabetes,
the number of years of disease as well as the therapy used,
the presence or absence of neuropathy and history of foot ulcer.
B.
Ultrasonography investigations
The same expert operator performed ultrasonography examinations using a portable US system (MyLabAlpha,
Esaote S.p.A.,
IT),
always applying the same protocol.
Specifically,
the right foot was always the first to be scanned and the ultrasound images were performed with the probe in both longitudinal and transversal positions (Figure 1).
B-Mode US acquisitions (performed to measure the heel pad thickness) were followed by ElaXto scans.
Table 1 Subjects’ characteristics
|
Controls
|
Diabetic subjects
|
Number of subjects
|
8
|
8
|
Age (years)
|
68±7
|
72±9
|
Weight (kg)
|
72.8±16.6
|
75.0±10.3
|
Height (m)
|
166±11
|
166±10
|
BMI (kg/m2)
|
26±5
|
27±6
|
Shoe size
|
40±3
|
41±3
|
Sport (h/week)
|
3±1
|
2±3
|
A large amount of ultrasound gel (Parker Aquasonic 100,
Parker Laboratories,
USA) was used in order to avoid compression of the probe coupling with the heel skin.
Indeed,
it is known that even a small compression changes the shape and dimension of the heel tissues.
The technique adopted consisted in starting to couple the probe (SL1543,
3-13 MHz,
Esaote S.p.A.,
IT) with the heel tissue up to complete coupling of the probe on the center part of the echographic image sector.
The probe movement towards the tuberosity of the heel stopped at the moment the first tissue compression was noticed.
The heel pad thickness (UHPT),
defined as the shortest distance between the calcaneus tuberosity and the heel skin,
was calculated for each heel as the mean value between the longitudinal and transversal measurements.
During the activation of sonoelastography modality,
the ROI was positioned over the heel tissues between the tuberosity and the skin coupled with the ultrasound probe (in average 3 mm over the tuberosity of the heel and up to 3 mm before the skin coupled with the ultrasound transducer).
The height of the soft layer (colored red in ElaXto) was measured from each sonoelastography acquisition.
Statistical analyses (paired and unpaired t test) were carried out in order to differentiate between healthy and diabetic heel pads.
A P-value<0.05 was chosen to indicate a significant difference.