Shear Load In-shoe Plantar Sensing/Strain Analyses and Mapping in Diabetic Foot Ulcers
Conditions: Diabetic Foot, Diabetic Foot Ulcer
Sponsor: The Leeds Teaching Hospitals NHS Trust

1 
 
Shear Load In-shoe Plantar Sensing/sTRain analysEs And 
Mapping in diabetic foot ulcers: SLIPSTREAM 
 
 
Version 
 
 
1.1 
Date 
 
 
 
03/08/2021 
Sponsor 
 
 
Leeds Teaching Hospitals NHS Trust 
REC Reference 
 
 
ISRCTN 
 
 
 
IRAS reference 
 
291873 
Chief Investigator  
 
Mr David Russell 
Associate Professor and Honorary Consultant Vascular 
Surgeon   
Clinical Trials Research Unit 
Leeds Institute for Clinical Trials Research 
University of Leeds 
Leeds 
LS2 7JT 
Tel: 07803938880 
Fax: 0113 392 2624 
Email: davidrussell1@nhs.net 
 
Research Fellow 
 
Mr Alexander David Jones 
/Principle investigator  
Vascular Research fellow 
Leeds Vascular Institute,  
Leeds General Infirmary,  
Great George Street,  
Leeds  
LS1 3EX. 
Tel: 07773605504 
Email: alexander.jones9@nhs.net 
 
Project Team/Authors  
Dr Peter Culmer, Dr Heidi Siddle, Prof Jane Nixon 
 
 
 
 
 
The Sponsor accepts no responsibility for the accuracy of content reproduced from this 
protocol and incorporated into additional documentation developed by collaborating or third 
party organisations. 
 

2 
 
1. Key Contacts  
 
 
 
 
Project Lead 
 
Mr Alexander David Jones,  
Vascular Research fellow,  
Leeds, Vascular Institute, 
 Leeds General Infirmary,  
Great George Street,  
Leeds, LS1 3EX. 
 
Tel: 07773605504 
Email: alexander.jones9@nhs.net 
 
Chief Investigator 
 
Mr David Russell 
Associate Professor and Honorary Consultant Vascular 
Surgeon   
Clinical Trials Research Unit 
Leeds Institute of Clinical Trials Research 
University of Leeds 
Leeds 
LS2 7JT 
Tel: 07803938880 
Email: davidrussell1@nhs.net 
 
 
MD Supervisors 
 
 
Dr Peter Culmer 
Associate Professor 
School of Mechanical Engineering 
University of Leeds 
Woodhouse 
Leeds, LS2 9JT 
Tel: 01133432141 
Email: P.R.Culmer@leeds.ac.uk 
 
Dr Heidi Siddle 
Associate Professor and Honorary Consultant Podiatrist 
Leeds Institute of Rheumatic & Musculoskeletal 
Medicine 2nd Floor Chapel Allerton Hospital Chapeltown 
Road Leeds, LS7 4SA 
Tel: 01133922267 
Email: H.Siddle@leeds.ac.uk 
 
Professor Jane Nixon 
Director 
Leeds Institute of Health Sciences 
University of Leeds 
Leeds 
LS2 7JT 
 
 
 
 
 
 
 
 
 
 
 
Tel:  
0113 343 1488 
Email: J.E.Nixon@leeds.ac.uk  
 
 

3 
 
2. Contents 
 
GENERAL INFORMATION 
Page No. 
1. 
KEY CONTACTS 
2 
2. 
CONTENTS PAGE 
3 
3. 
GLOSSARY OF TERMS 
4 
4. 
BACKGROUND 
5-6 
5. 
AIMS AND OBJECTIVES 
7 
6. 
FLOW DIAGRAM 
8 
7. 
STUDY DESIGN 
9 
 
7.1 BINDING 
9 
8. 
ELIGIBILITY 
9 
8.1 DFU GROUP 
9-10 
8.2 LOW RISK GROUP 
10-11 
9. 
MATCHING 
11 
10. RECRUITMENT 
11 
10.1 RECRUITMENT SETTING 
11 
 
10.2 RECRUITMENT PROCESS 
11-12 
10.3 SCREENING  
12 
10.4 INFORMED CONSENT AND ELIGIBILITY 
12-13 
11. DATA COLLECTION 
14 
11.1 CLINICAL CHARACTERISTICS 
14 
11.2 PRESSURE AND STRAIN ASSESSMENT 
14 
11.3 STAMP 
14-15 
11.4 PEDAR 
15 
11.5 SLIPS 
15-16 
12. WITHDRAWAL OF CONSENT 
16 
13. ADVERSE AND SERIOUS ADVERSE EVENTS  
16 
13.1 GENERAL DEFINITIONS 
16 
13.2 DEFINITIONS OF (S)AES AND REPORTING 
17 
14. OUTCOMES 
17 
15. STATISTICAL CONSIDEREATIONS 
18 
16. STATISTICAL ANALYSIS 
18-19 
17. DATA AND MONITORING 
19 
17.1 DATA COLLECTION 
19 
17.2 DATA STORAGE 
20 
18. QUALITY ASSURANCE AND ETHICAL CONSIDERATIONS 
20 
18.1 QUALITY ASSURANCE 
20 
18.32 ETHICAL CONSIDERATIONS 
20 
19. CONFIDENTIALITY 
20-21 
20. ARCHIVING 
21 
21. STATEMENT OF INDEMNITY 
21 
22. PUBLICATION POLICY 
18 

4 
 
3. Glossary of terms 
 
AE  
Adverse Event  
CTRU Clinical Trials Research Unit 
DFU 
Diabetic foot ulcer 
DIC 
Digital image correlation 
DPN 
Diabetic peripheral neuropathy 
eGFR Estimated glomerular filtration rate 
GCP 
Good clinical practice 
IWGDF International working group for the diabetic foot  
LCH 
Leeds Community Healthcare NHS Trust 
LOPS Loss of protective sensation 
MTH 
Metatarsal head 
MRC  Medical Research Council  
PI 
Principal investigator 
PIL 
Patient information leaflet 
PSS 
Plantar shear stress 
RGF  Research Governance Framework 
RUSAE Related Unexpected Serious Adverse Event 
SAE 
Serious Adverse Event 
SLIPS Shear load inductive plantar sensing 
STAMP Strain analysis mapping of the plantar surface 
SOPs  Standard Operating Procedures  
 
 
 
 
 
 
 
 
 
 

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4. Background 
 
Four hundred and sixty-three million adults live with diabetes globally, with prevalence 
expected to rise to 700 million by 2045.[1] Up to one quarter will develop a diabetic foot ulcer 
(DFU),[2] with 5-8% of these requiring a major amputation within 1 year.[3] Survival is poor, 
5-year mortality following development of a DFU has been estimated at 30.5%, with half of 
patients undergoing a major amputation dead in 5 years. Ulceration is a multifactorial process 
with peripheral neuropathy and arterial disease playing central roles. Neuropathy leads to the 
loss of protective sensation and development of abnormal foot architecture.[4] Loss of 
protective sensation results in undetected, repetitive trauma to the foot.[4] This effect is 
compounded by the development of structural abnormalities, which increases plantar stress 
leading to inflammation and tissue breakdown.[5] Plantar pressure forms the vertical 
component of the load experienced during normal gait. Plantar shear stress (PSS) forms the 
tangential component of plantar load. It acts parallel to the foot, usually caused by friction 
between the foot-surface interface and comprises antero-posterior (AP) and medio-lateral 
(ML) components. [6] It is suggested that the repetitive, multidirectional nature of PSS, both 
at surface and subsurface levels is a significant contributor to ulcer formation. [7–12]  
 
The authors have performed a systematic review and meta-analysis to summarise the 
literature on PSS in the diabetic foot. The results of this meta-analysis demonstrated that 
patients with diabetes and with a loss of protective sensation sustain greater levels of PSS 
than healthy controls. It also showed those with a current, or previous ulcer exhibit significantly 
greater levels of PSS compared with those with loss of protective sensation without a history 
of ulceration. However, it also identified a wide spectrum of methods of measuring PSS , with 
no validated gold standard. Most studies were performed ‘barefoot’; however, as the 
cornerstone of management of the diabetic foot is ensuring plantar tissue stress reduction 
through all weight bearing activities by using appropriate footwear, this form of analysis does 
not reflect the typical shear stresses that are sustained during a normal day. The review 
therefore highlighted the need for advances in technology to reliably measure ‘in-shoe’ shear 
stress and to transfer this to clinical studies investigating its relationship with ulcer formation. 
  
Sensing platforms and insoles measure PSS and plantar pressure in real-time at the foot-
surface interface. The technical challenges involved has led to the development of a new 
method of measuring the effects of PSS and plantar pressure at the foot-surface interface 
based upon Digital Image Correlation (DIC). DIC is an optical based technique used to 
measure displacement and strain. It involves comparing the image of the point or object of 
interest prior to loading, with those after or during loading. The method utilises DIC software 
employing algorithms to track blocks of pixels to measure displacement or strain. Strain is 
defined as the ratio between the deformation of a structure and its original length. In the 
context of an insole, the strain is determined by the plantar load, the product of both PSS and 
plantar pressure. Thus, it is hypothesised that the level of strain is a product of the cumulative 
effect of plantar pressure and shear stress during walking.  
In-shoe technology 

6 
 
‘STrain Analysis Mapping of the Plantar surface (STAMP)’ is an untested method, 
designed by the University of Leeds to measure ‘in-shoe’ strain patterns on the plantar surface 
of the foot. The insole comprises a pseudorandom pattern applied to a plastically deformable 
insole using a temporary tattoo layer. STAMP utilises DIC to track the deformation of the 
pattern on the surface of the insole following a period of walking. This study will use STAMP 
to measure peak plantar strain. Peak plantar strain is defined as the maximum strain value 
within a region. 
 
‘Shear Load Inductive Plantar Sensing’ (SLIPS) is a new system designed by the University 
of Leeds to measure ‘in-shoe’ shear and pressure. SLIPS is a wearable sensing insole which 
integrates 64 tri-axis soft force sensors, simultaneously measuring both plantar pressure and 
PSS. This study will use SLIPS to analyse peak PSS, mean peak plantar pressure and 
pressure time integral (PTI). Peak PSS is the largest shear value within a region per gait cycle. 
Peak plantar pressure is defined as the largest pressure reading within a region per gait cycle. 
PTI describes the cumulative effect of pressure over time and is calculated  as the sum of the 
products of plantar pressure per time sample by the duration of that time sample. 
 
Pedar (Novel gmbh, Munich), is a commercially available system used to measure in-shoe 
plantar pressure. The Pedar system will be used to compare the load measured by the novel 
systems (STAMP and SLIPS) with pressure data (peak plantar pressure and PTI) from Pedar. 
 
The patient group of interest is those that have developed a plantar DFU as a result of 
abnormal biomechanical loading. The primary pathological process underlying this is diabetic 
peripheral neuropathy (DPN) which leads to the development of foot deformities, including 
hammer toe, claw toe, hallux valgus, prominent metatarsal heads, pes cavus, pes planus and 
pes equinus (IWGDF definition of diabetic foot deformity).[13] A subset of patients with DFUs 
may develop these as a result of significant ischaemia due to peripheral arterial disease in the 
absence of significant biomechanical abnormalities. These patients will not be eligible for 
inclusion, and will be excluded if they have an opening toe pressure of <40mmHg.  
 
Patients with diabetes are classified as ‘low’, ‘intermediate’ and ‘high risk’ risk of ulceration by 
NICE (NG 19).[14] Patients at highest risk of ulceration are those with a recently healed ulcer; 
40% of patients re-ulcerate within 1-year,[2] and we have therefore selected this group to 
represent the high-risk group for ulcer formation in this study. Those classified as ‘low risk’, 
have no risk factors for ulceration other than callus alone. With the lowest risk for ulceration 
and without DPN or foot deformities; this cohort of patients will be used as the comparison 
group. This study will investigate plantar strain, PSS and plantar pressure in these two patient 
groups. 
 
 
 

7 
 
 
5. Aims and objectives 
 
The overall aim is to investigate whether patients with diabetes and a recently healed DFU 
demonstrate elevated levels of plantar strain, PSS and plantar pressure compared with 
patients at low risk for ulceration, without a history of DFU. 
 
Primary objective 
The primary objective is to compare peak plantar strain, peak PSS and peak plantar pressure 
in high-risk patients with diabetes who have a recently healed DFU (DFU group) with patients 
with diabetes who are at low risk of developing a DFU (Low risk group).  
 
Secondary objectives 
1) To report the relationship between location of peak plantar strain, peak PSS and peak 
plantar pressure with location of recently healed ulceration in the DFU group. 
 
2) To investigate the relationship between peak plantar strain, peak PSS, peak plantar 
pressure and PTI at the 1st metatarsal head (MTH), 2nd MTH, 3rd MTH, 4th MTH, 5th 
MTH, hallux, second toe, toes 3-5, midfoot and heel, and to compare between the DFU 
and Low risk groups. 
3) To inform research design for prospective studies investigating peak plantar strain, 
peak PSS and peak plantar pressure as risk factors for ulceration; including 
methodology, patient selection and modifications to the technology used. 
 
Technology 
Load measured 
In-
shoe/barefoot 
Purpose 
STAMP 
Peak plantar 
strain 
In-shoe 
New technique used for the 
assessment of plantar strain 
SLIPS 
Peak PSS, peak 
plantar pressure 
and PTI 
In-shoe 
New insole designed to measure 
plantar shear and pressure 
Pedar 
Peak plantar 
pressure and 
PTI 
In-shoe 
Used to investigate the association 
between the measurements recorded 
by STAMP and SLIPS and plantar 
pressure recorded by the gold standard 
pressure system. 
 
 
 
 

8 
 
6. Flow Diagram 
 
Multidisciplinary Diabetes Limb Salvage Clinics and Community Podiatry 
Screening & Information Provision 
Consent (In clinic for DFU group, at assessment visit for Low risk 
group) 
Formal Eligibility Assessment and Clinical Assessments (One stop 
assessment)* 
DFU group 
Low risk group 
STAMP + 
Pedar +  
 
STAMP+ 
Pedar +  
 
 
 
 
 
 
 
SLIPS 
subsample 
 
 
 
SLIPS 
subsample 
 
Prior DFU 
right foot & 
shoe size 8-11 
foot & < 100 
kg 
Shoe size 8-
11 foot & < 
100 kg 
* Single visit unless technology failure requires a second visit 
 
 
 
 
 
 
 
 
 
 

9 
 
7. Study Design 
 
The study design is a single centre case-control study. Cases will consist of patients with a 
recently healed DFU. The Low risk group (control group) will consist of patients with diabetes 
at low risk of ulceration (NICE NG19 definition).[14] The risk factor of interest is plantar strain, 
measured using the STAMP technique and PSS measured by the SLIPS insole system.  
 
Upon enrolment, baseline clinical data will be collected for each patient. All patients will 
undergo assessment using STAMP and Pedar systems. If eligible, this will be followed by 
assessment with the SLIPS system within the same visit.   
 
7.1 Blinding 
 
To reduce the risk of measurement bias during data collection, the order of tests will be 
randomised using the Latin square method. 
To reduce the risk of observer bias, data will be analysed in batches, with the assessor blinded 
to patient group.  
A subsample of 10% of the patients will undergo analysis by a second assessor, also blinded 
to patient group and level of agreement analysed. 
 
8. Eligibility  
 
8.1 DFU group 
 
Inclusion criteria 
All patients with diabetes who have a recently healed plantar DFU will be identified by the 
clinicians within the Diabetes Limb Salvage Service and assenting patients will be assessed 
for eligibility by the research team. Patients will undergo STAMP and Pedar assessment if 
they fulfil the following inclusion criteria: 
1) ≥18 years of age 
2) A diagnosis of diabetes mellitus 
3) A diagnosis of diabetic peripheral neuropathy (DPN)  
4) Recently healed plantar DFU (healed within the last 3 months) 
5) Provide informed written/witnessed verbal consent to participate 
 
Exclusion criteria 
Patients will be ineligible if they meet the any of the following exclusion criteria: 

10 
 
1) Those who are unable to mobilise independently 150m, without the use of walking aids 
and thus unable to complete the walking assessment 
2) Previous ipsilateral minor amputation 
3) Previous ipsilateral surgical offloading procedure 
4) Previous contralateral major amputation 
5) Ipsilateral toe pressure <40mmHg 
6) Previous open or endovascular ipsilateral revascularisation 
 
SLIPS assessment inclusion criteria 
The SLIPS insole has been designed to measure the plantar load of the right foot, and due to 
its size, can only be accommodated by a size 8-11 shoe. The insole is also only able to 
accommodate patients weighing <100kg. Therefore, in addition to the above criteria, patients 
will undergo SLIPS assessment if the fulfil the following additional inclusion criteria:  
1) Recently healed plantar DFU located on the right foot 
2) The right foot can be accommodated in a size 8-11 shoe 
3) Weight <100kg 
 
 
8.2 Low risk group 
 
Inclusion criteria 
Potential patients will be identified by clinicians in the community podiatry service and 
assenting patients will be assessed for eligibility by either the attending clinical team or a 
member of the clinical research team. Patients will undergo STAMP and Pedar assessment if 
they fulfil the following inclusion criteria: 
1) ≥18 years of age 
2) A diagnosis of  diabetes mellitus 
3) Low risk for DFU according to the NG19 guidelines (no risk factors for ulceration except 
callus alone) 
4) Provide informed written/witness verbal consent to participate  
 
SLIPS assessment inclusion 
Consenting patients will also undergo SLIPS assessment if they fulfil the following additional 
inclusion criteria: 
1)  The right foot can be accommodated by a size 8-11 shoe. 
2) Weight < 100kg 
 
Patients will be ineligible if they meet any of the following exclusion criteria:  

11 
 
1) Those who are unable to mobilise independently 150m, without the use of walking aids 
and thus unable to complete the walking assessments 
2) Toe pressure < 40mmHg 
3) Presence of a foot deformity 
4) Previous ipsilateral minor amputation 
5) Previous contralateral major amputation 
 
 
9. Matching 
 
Matching of DFU and Low risk groups will not be performed. 
Rationale: 
In a study by Yavuz et al., (2014), investigating PSS in neuropathic and non-neuropathic 
patients with diabetes, neither BMI nor age accounted for a significant proportion of the 
variance of shear between groups.  
Furthermore, the effect of age, BMI, gender and walking speed can be adjusted for if 
appropriate in the analysis. 
To ensure equal group sizes for SLIPS assessment, the proportion of patients per group will 
be monitored and selective sampling according to shoe size and weight will be performed and 
recruitment adjusted as appropriate. 
 
10. Recruitment 
 
10.1 Recruitment setting 
 
Patients within the DFU group will be recruited from secondary care from the LTHT Diabetes 
Limb Salvage Service clinics. The service is run by podiatrists, diabetologists, vascular 
surgeons and orthotists specialising in care of the diabetic foot. Patients within the Low risk 
group will be recruited through the Leeds Community Healthcare NHS Trust (LCH) podiatry 
service which has diabetic foot protection clinics with podiatry led care. 
 
10.2 Recruitment process 
 
All patients with diabetes and a recently healed plantar DFU seen within the Diabetes Limb 
Salvage Service clinic will be considered as potentially eligible for this study. Where indicated 
by the attending clinical team and after agreeing to further information, patients will receive a 
full verbal explanation of the study and a Patient Information Leaflet (PIL) by either the 
attending clinical team or a member of the clinical research team  at a time convenient to the 
patient during their routine clinic visit. Consenting patients will undergo an eligibility 

12 
 
assessment within their routine clinic appointment. An appointment will then be booked to 
attend the walking assessments. All data will be collected within a single visit. 
The Low risk group will be recruited using the Leeds Community Healthcare podiatry service. 
The service will review their caseload and identify potentially eligible patients who will be sent 
a letter and the PIL. The letter will include a brief introduction to the study and patients will be 
invited to contact the research team by return of the form, email or via telephone if they are 
interested in participating. Assenting patients will then undergo an eligibility assessment via 
telephone and be invited to attend a research clinic visit for consent and study assessments. 
Community clinics may also be attended by the clinical research team to enable immediate 
referral of patients identified by the attending clinical team; all low risk patients will receive a 
full verbal explanation of the study and a Patient Information Leaflet (PIL) by a member of the 
clinical research team at a time convenient to the patient during their routine clinic visit. 
Consenting patients will undergo an eligibility assessment within their routine clinic 
appointment. An appointment will then be booked to attend the walking assessments. All data 
will be collected within a single visit. ;  
 
 
 
 
10.3 Screening 
 
A log will be kept of all patients who have had an eligibility assessment but have not been 
recruited for the study. Documented reasons for ineligibility or declining participation will be 
collected and monitored. The following anonymised data will be collected in the log: 
1) Age 
2) Gender 
3) Ethnicity 
4) Date screened 
5) Reason not suitable for study OR 
6) Reason for declining participation  
 
 
10.4 Informed consent and eligibility 
As per the recruitment section, patients will have received a PIL and a full verbal explanation 
of the study. Patients will have as long as they need to consider participation and will be given 
the opportunity to discuss the study with family and other healthcare professionals before they 
are asked whether they would be willing to take part. Patients will also be provided with the 
contact details of the research fellow where he/she may be able to obtain further information 
about the study. During the consent process, patients will have the opportunity to ask 
questions.,  
 
The Chief Investigator (CI) retains overall responsibility for the informed consent of participants 
and must ensure that any person delegated responsibility to participate in the informed 

13 
 
consent process is duly authorised, trained and competent to participate according to the 
ethically approved protocol, principles of Good Clinical Practice (GCP) and Declaration of 
Helsinki 1996.  
 
The informed consent process will be undertaken by the clinical research team or registered 
healthcare professional who is GCP trained.  
 
The CI takes responsibility for ensuring that all vulnerable subjects are protected and 
participate voluntarily in an environment free from coercion or undue influence. 
 
Informed consent must be obtained prior to the patient undergoing procedures that are 
specifically for the purposes of the study (including the collection of identifiable participant 
data). The right of a participant to refuse participation without giving reasons must be 
respected.  The participant must remain free to withdraw at any time from the study without 
giving reasons and without prejudicing his/her further treatment and will be provided with a 
contact point where he/she may obtain further information about the study.  
 
Should the participant be capable of giving consent but physically unable to complete the 
written aspects of the consent form, witnessed consent should be obtained. An appropriate 
witness would be a family member or friend of the patient, or another member of the 
participant’s  healthcare team who is not directly involved in the research study. 
 
A record of the consent process detailing the date of consent and those present will be detailed 
in the patients’ healthcare records. The original consent form will be filed securely by the 
clinical research team in a locked filing cabinet in a locked room at the Leeds Vascular Institute 
and a second copy uploaded to the electronic patient record (as per local practice).  
 
 
 
 
11. Data collection 
 
Following consent within the routine clinic appointment, patients within the DFU group will be 
invited will be invited to a research visit for the baseline clinical assessment and the strain, 
PSS and pressure assessment. Consent, baseline assessments and strain, PSS and pressure 
assessments for the Low risk group will be performed in one visit. All assessments are 
expected to be performed within a one-hour visit. 
 
11.1 Clinical Characteristics 
 

14 
 
Following informed consent, demographics and clinical characteristics for each patient will be 
documented. A standardised proforma will be used to collect  clinical characteristic data. 
History, examination and review of the medical records will be performed to collect information 
on: Age, sex, weight, height, duration of diabetes, presence of DPN, smoking status, duration 
of ulceration, time since ulceration, toe pressure, HbA1c (within the last 6 months), pre-
ulcerative lesion at entry, presence and type of foot deformity. 
 
Presence of co-morbidities including presence of chronic kidney disease, defined as an eGFR 
<60 for three months; heart failure, based upon clinic records. These characteristics are based 
upon reporting standards guidelines.[15]  
 
Definitions: 
Diabetic Peripheral Neuropathy – Diagnosed using 10g monofilament test. Methodology will 
be as described in the International Working Group for the Diabetic Foot guidelines on the 
prevention and management of diabetic foot disease.[5] 
Pre-ulcerative lesion – Skin fissure, intra-cutaneous/subcutaneous haemorrhage or blister 
(IWGDF definition of pre-ulcerative lesion).[13] 
 
 11.2 Pressure and strain measurement  
 
To reduce measurement bias, the order of tests performed will be randomised using the Latin 
square method. 
 
    
11.3 STAMP 
 
For the DFU group, the foot with the recently healed DFU will be analysed. For the Low risk 
group the right foot will be selected. Evidence suggests that there is no difference in vertical, 
or antero-posterior ground reaction force between dominant or non-dominant limb, therefore 
no bias should be introduced.[16]  
To capture strain data an insole is created using plasticine and inserted into a trial shoe, a 
standard sock will be worn before donning the trial shoe the patient then undertakes a walking 
assessment.  
The procedure is as follows:  
A pseudo-random pattern will be marked onto a plasticine sheet of uniform thickness. An 
image of this will be taken prior to placing this onto the in-sole of a trial shoe. Each participant 
will be provided with a pair of disposable socks and be asked to wear the provided trial shoes. 
Participants will be asked to take 10 steps forward and then turn around to walk back to the 
initial position at their natural speed and step length before removing the STAMP insole. Three 

15 
 
repeats of this activity will be performed. Walking speed will also be recorded using an 
accelerometer. 
 
An image will be taken of the pattern following the walking assessment. Pre- and post-walking 
assessment images will be compared using the software GOM Correlate, and analysis 
performed with the MATLAB analysis package. 
 
 
 
11.4 Pedar 
 
To capture pressure data the patient will undertake a walking assessment using the Pedar 
system. 
The procedure is as follows: 
The appropriately sized Pedar insole will be placed into the provided trial shoe the side of 
recently healed ulcer for the DFU group. The insole will be placed into the right shoe of the 
Low risk group. Each patient will be asked to walk 10 metres forward and then turn and walk 
back to the initial position at their natural speed and step length. Three repeats of this activity 
will be conducted. 
 
 
      
11.5 SLIPS 
 
To capture PSS data the patient will undertake a walking assessment using the SLIPS insole. 
The procedure is as follows: 
The sensing insole will be placed inside a commercial shoe (manufactured by Steeper Group, 
Leeds) for the right foot. A leather/foam insole (with the same size and thickness to the sensing 
insole) will be put into the shoe for the left foot. Each patient will be provided a pair of 
disposable socks and be asked to wear the provided shoes.  
 
Patients will be allowed a short period of time to acclimatise to the shoes. Patients will then 
be asked to walk 10 metres forward and then turn around to walk back to the initial position 
at their natural speed and step length. Three repeats of this activity will be conducted. 
  
   
 
12. Withdrawal of Consent 
 

16 
 
Patients may withdraw consent from the study at any time without explanation. The CI or PI 
or should make every effort to ensure that the specific wishes of any patient who wishes to 
withdraw from further involvement in the study are defined and documented using the 
withdrawal case report form. Patient withdrawal will be classified as follows:  
a) Withdrawal following STAMP walking assessment 
b) Withdrawal following Pedar walking assessment 
c) Withdrawal following SLIPS walking assessment 
For a), b) and c) patients will be offered to allow use of data up to the point of withdrawal. 
Patients can request complete withdrawal of data if it has not been included in an analysis; 
data utilised in analysis will not be withdrawn. 
Patients who wish to discontinue performing the walking assessments will be allowed to at 
any point. Reasons for this will be explored and patients will be offered to return at another 
appointment if appropriate. Data that has been collected up to that point will be used in the 
analysis with the patient’s consent.  
 
 
13.Adverse and serious adverse events 
 
13.1 General definitions 
 
An Adverse Event (AE) is any untoward medical occurrence in a patient or a clinical trial 
subject which does not necessarily have a causal relationship with the device/procedure. 
 
A Serious Adverse Event (SAE) is an untoward occurrence that: 
- 
Is fatal 
- 
Is life threatening 
- 
Requires hospitalisation or prolongation of existing hospitalisation 
- 
Results in persistent or significant disability 
- 
Consists of a congenital anomaly or birth defect 
- 
Is otherwise considered medically significant by the Investigator 
 
A Related Unexpected Serious Adverse Event (RUSAE) means for an SAE occurring to a 
research participant in the opinion of the Chief Investigator was: 
- 
‘Related’ that is, it resulted from the administration of any of the research procedures, and 
- 
‘Unexpected’ that is, the type of event is not listed in the protocol as an expected 
occurrence. 
 
Medical and scientific judgement must be exercised in deciding whether an event is serious. 
These characteristics/consequences must be considered at the time of the event and do not 
refer to an event which hypothetically may have caused one of the above.  
 

17 
 
   
13.2 Definitions of (S)AEs and reporting 
 
This is a study using three devices to measure plantar load, with no instigation of treatment, 
nor change to patients’ standard care. Therefore, incidents will only be reported as AEs or 
SAEs if injury occurs during walking assessment.  
 
14.Outcomes 
 
Primary outcome: 
The primary outcome is the difference in peak plantar strain and peak PSS between the DFU 
and Low risk groups as measured by: 
1) STAMP  
2) SLIPS  
 
Secondary outcomes: 
 
1) Regional peak plantar strain as measured in-shoe using the STAMP insole. Measured 
at the standard ten regions heel, mid foot, 1st MTH, 2nd MTH, 3rd MTH, 4th MTH, 5th 
MTH, hallux, second toe and toes 3-5. Mean regional peak plantar strain will be 
compared between DFU and Low risk groups. 
2) Regional peak PSS measured at the standard ten regions heel, mid foot, 1st MTH, 2nd 
MTH, 3rd MTH, 4th MTH, 5th MTH, hallux, second toe and toes 3-5. Mean peak regional 
PSS will be compared between DFU and Low risk groups. 
3) Global and regional peak plantar pressure, and PTI measured in-shoe using the Pedar 
system, compared between DFU and Low risk groups. 
 
 
 
 
15.Statistical considerations 
 
Sample size 
The STAMP method is a novel technique, as such nil data exists in the literature to determine 
a sample size. SLIPSTREAM is a preliminary study and due to the time and resource 
constraints of an MD project it is not expected to be powered to detect statistical significance. 
Based upon preliminary work, it is expected the mean difference will be 4, with a standard 
deviation of 6. Therefore 28 patients per group are required for 90% significance at a power 
of 80%.  
 

18 
 
Planned recruitment rate 
It is estimated  4 patients are identified with a healed plantar ulcer every week at the DLSS 
clinic. Assuming half of these consent to inclusion, and dependent upon the required sample 
size, recruitment is likely to be completed within one year.   
 
16.Statistical analysis 
 
Primary outcome analysis 
The mean changes in coordinates and magnitude of principle strains on the plantar aspect of 
the foot will be calculated for each patient using GOM correlate and MATLAB. Linear 
regression will be used to compare mean peak plantar strain between DFU and Low risk 
groups.  Bivariable analysis using Peason’s correlation coefficient will be performed to 
investigate the relationship between the continuous independent variables and mean peak 
plantar strain. Multiple regression analysis will be used to explore the relationship between 
correlated continuous variables and the risk group. 
 
 
Secondary outcome analyses 
1) Regional analysis: A masking algorithm will be utilised to map the previously defined 
areas of interest (Measured at the standard ten regions heel, mid foot, 1st MTH, 2nd 
MTH, 3rd MTH, 4th MTH, 5th MTH, hallux, second toe and toes 3-5)  following data 
acquisition.  Intergroup comparisons will be performed comparing mean peak plantar 
strain at each region using linear regression. Multiple regression analysis will be used 
to explore the relationship between correlated continuous variables and the risk group. 
This method will also be utilised to perform regional intergroup comparisons for peak 
PSS, peak plantar pressure and PTI. 
2) Peak PSS between DFU and Low risk groups will be compared using linear regression. 
Bivariable analysis using Peason’s correlation coefficient will be performed to 
investigate the relationship between the continuous independent variables and mean 
peak plantar strain. Multiple regression analysis will be used to explore the relationship 
between correlated continuous variables and the risk group. This method will also be 
used to perform comparisons between groups for peak plantar pressure and PTI.  
3) Multinomial regression analysis will be used to investigate the relationship between 
peak plantar strain and ulcer location. 
4) Regional analysis: A masking algorithm will be utilised to map the previously defined 
areas of interest (Measured at the standard ten regions heel, mid foot, 1st MTH, 2nd 
MTH, 3rd MTH, 4th MTH, 5th MTH, hallux, second toe and toes 3-5) following data 
acquisition.  Intergroup comparisons will be performed comparing mean PSS at each 
region using ANCOVA, adjusting for factors matched…... Evidence of associated will 
be present if r > 0.3. Multiple regression analysis will be used including continuous 
variables with r > 0.3, risk group and the presence of joint deformity. 
 

19 
 
 
 
 
 
17. Data and monitoring 
 
 
 
 
17.1 Data collection 
 
All data will be collected and stored in accordance with Trust standards and procedures. 
When the data is collected it will be coded to pseudonymise the data. The patients’ details 
and their coded data will be then separated and kept in the locations previously stated. The 
study database will be stored on a password-controlled computer in a locked access-
controlled area in the Leeds General Infirmary. The patient files will be stored in a locked 
cabinet in a locked room in the Leeds Vascular Institute. 
 
 
 
 
 
 
17.2 Data storage 
 
All data will be handled, computerised and stored in accordance with the Data Protection Act 
1998. 
 
 
 
18. Quality Assurance and Ethical    
Considerations 
 
18.1 Quality Assurance 
 
The study will be conducted in accordance with the principle of Good Clinical Practice (GCP) 
in clinical trials as detailed by the Medical Research Council (MRC), the NHS research 
Governance Framework (RGF) and Scottish Executive Health Department Research 
Governance Framework for Health and Social Care 2006. 
 
18.2 Ethical considerations 
 
The study will be performed in accordance with the recommendations guiding physicians in 
biomedical research involving human subjects adopted by the 18th World Medical Assembly, 
Helsinki, Finland, 1964, amended at the 52nd World Medical Association General Assembly, 
Edinburgh, Scotland (1996 or later). Informed written/witnessed verbal consent will be 
obtained from the patients prior to inclusion into the study. The right of a participant to refuse 

20 
 
participation without giving reasons must be respected. The participant must remain free to 
withdraw at any time from the study without giving reasons and without prejudicing his/her 
further treatment. The study will be submitted to and approved by a main REC prior to entering 
patients into the study. The CI will provide the main REC with a copy of the final protocol, 
patient information sheets, consent forms and all other relevant study documentation.    
 
 
19. Confidentiality 
 
Collection of patient data that includes patient identifiers will comply with all aspects of the 
Data Protection Act 1998. Any information that would allow individual patients or clinicians to 
be identified will not be released into the public domain. 
 
All data will be collected and stored in accordance with Trust standards and procedures. 
When the data is collected it will be coded to pseudonymise the data. The patients’ details 
and their coded data will be then separated and kept in the locations previously stated. 
 
Computers that are used to store electronic data will be password protected. Paper copies of 
data will be kept in a locked filing cabinet in a locked room. All new data will be backed up at 
the end of each data collection session. Weekly back up of all the data set will be stored 
both on and off site securely. Patient’s details will not be exposed to the public at any stage 
and kept securely under the research team.  
 
 
20. Archiving 
 
At the end of the study, the data will be securely archived in line with Trust policy for 15 years. 
Following this, arrangements for confidential destruction will be made.  
 
21.Statement of Indemnity 
 
As sponsor, the Leeds Teaching Hospitals NHS Trust does not provide indemnification against 
claims arising from non-negligent harm. 
The NHS has a duty of care to patients treated, whether or not the patient is taking part in a 
clinical study. Therefore, clinical negligence indemnification will rest with the participating NHS 
Trust or Trusts under standard NHS arrangements under this duty of care. 
 
 
22. Publication Policy 
 

21 
 
The study will be registered with an authorised registry, according to the International 
Committee of Medical Journal Editors (ICMJE) Guidelines, prior to the start of recruitment.  
 
The success of the study depends upon collaboration of all participants. For this reason, credit 
for the main results will be given to all those who have collaborated in the study, through 
authorship and contributorship. Uniform requirements for authorship for manuscripts 
submitted to medical journals will guide authorship decisions. These state that authorship 
credit should be based only on substantial contribution to: 
• 
Conception and design, or acquisition of data or analysis and interpretation of data, 
• 
Drafting the article or revising it critically for important intellectual content, 
• 
And final approval of the version to be published, 
• 
And that all these conditions must be met (www.icmje.org)