Procedure for developing the guideline

The first draft of this guideline was written by the first author (JvN), and then sent to two co-authors (PAL and PW) for critical review and expert opinion. A second draft incorporating consensus feedback from the three authors was sent to all authors for critical review and expert opinion feedback. The authors of this guideline, all (inter)national experts in the field of diabetic foot ulcer and footwear management, came from the following backgrounds: podiatric medicine (n = 5), podiatric surgery (n = 1), human movement science (n = 2), wound medicine (n = 2), pedorthics (n = 1), rehabilitation medicine (n = 1), endocrinology (n = 1), and vascular surgery (n = 1). A third draft incorporating feedback from all co-authors was written by the first author (JvN) and again sent to all co-authors for review. This process was repeated one more time, until consensus was reached from all authors, leading to the final version of the guideline, approved by all authors.

Definitions for foot risk status

According to the NHMRC guideline, Aboriginal and Torres Strait Islander people with diabetes are considered to be at high-risk for foot ulceration, until the person’s level of risk is adequately assessed and confirmed otherwise [31].

To determine foot risk status, all people with diabetes should undergo at least a yearly foot screening by an appropriately trained registered healthcare professional with demonstrated competency [14, 31]. People with an intermediate- or high-risk foot status should be screened at least once every 3 to 6 months [14, 31]. In accordance with the NHMRC guideline, this should consist of screening for peripheral neuropathy (10 g monofilament sensitivity; vibration perception; neuropathy disability score), peripheral artery disease (palpation of peripheral pulses; ankle-brachial pressure index; toe-brachial pressure index), foot deformity (six point scale scoring small muscle wasting, Charcot foot deformity, bony prominence, prominent metatarsal head, hammer or claw toes and limited joint mobility), and assessment of a history of foot ulcer(s) or lower-extremity amputation [31]. The Australian Diabetes Society has published a video-example of such a foot examination [35].

Structure of the guideline

This guideline consists of three parts and a discussion. Firstly, footwear recommendations and their rationale are provided for people at-risk of foot ulceration; These recommendations apply to people at low-, intermediate- or high-risk. Secondly, additional specific footwear recommendations and their rationale are provided for people at intermediate- or high-risk of foot ulceration. Thirdly, footwear and offloading recommendations for people with a diabetic foot ulcer are summarised. Finally, considerations on footwear provision, on education and adherence, on cultural and geographical differences, and on methodology and terminology are discussed.

Footwear for people with diabetes at-risk of foot ulceration

Rationale

People with diabetes should wear footwear that fits, protects and accommodates the shape of their feet [14] (see Table 3 and Fig. 1). This includes having adequate length, width, and depth (and consequently adequate girth, i.e. adequate volume) [10, 15, 16, 32, 33]. A particular emphasis may need to be placed on the toe box of the shoe that should be consistent with the shape of the forefoot and toes of the person. An enclosed heel with a stabilising heel counter is recommended. Open-heel footwear can result in direct trauma injury to the heel and may require a person to claw their toes in order to keep the footwear fixed to their feet, further increasing the repetitive stress under their forefoot, and in turn the risk of ulceration. Adequate closure of the footwear is needed, to prevent the foot from sliding forwards and thus causing shear injury to the toes or plantar foot [36]. All features in Table 3 should be considered in combination, as their intended function is closely related and changes to one feature may affect other features and overall function [10, 15, 16, 32, 33].

Feature	Requirements
Length	Inner length of the footwear should be 1–2 cm longer than the foot length as measured from heel to the longest toe when a person is standing. Adequate length needs to be confirmed when people are weight-bearing while wearing the footwear.
Depth	Depth should accommodate the toes to move freely without causing pressure at either the medial, lateral or the dorsal side.
Width	Width should equal the width of all parts of the foot. Width is good when the upper can be slightly bunched. The relation between forefoot and hindfoot is important, as accommodating a wide forefoot may result in the heel being too wide.
Height	Footwear height can be low, ankle-high, or high. High footwear provides more firmness, stability and reduces joint motion. The shaft of high footwear also contributes to forefoot pressure reduction. See further Table 3 for specific height requirements for people with a foot deformity.
Insole	The removable moulded insole can be pre-fabricated, adjusted or custom-made. The primary function of the insole is pressure redistribution. This is achieved via the principle of increasing the contact area between the foot and the insole, and the addition of corrective elements in the insole. Shock-absorbing, soft but sufficiently resilient and non-slippery materials should be used. See further Table 4 for the offloading effects of specific insole modifications.
Outsole	Rubber, plastic, and leather can all be used in construction of footwear outsoles, but rubber outsoles are thought to be superior. Outsoles can be supple, toughened or stiff. The shoe should not be more supple than the foot, or friction between foot and shoe will develop during push-off. See further Table 3 for specific outsole requirements for people with a foot deformity and Table 4 for the offloading effects of specific modifications.
Rocker profile	Rocker profiles have proven effectiveness in reducing plantar pressures, especially the forefoot. The rocker profile chosen depends on the affected joints and is determined by the apex position (pivot point) and the angle from the pivot point to the tip of the toe. For plantar pressure reduction of the metatarsophalangeal joints, the pivot point needs to be proximal to these joints. The rocker profile also impacts balance; the more proximally placed, the greater the balance disturbance. A person’s balance should therefore always be taken into account when deciding on the rocker profile.
Heel enclosure	An adequately fitting and enclosed heel is recommended, as open backed footwear or a heel enclosure that is too wide can result in injury and usually requires a person to claw their toes in order to keep them on. The heel counter needs to be free of edges protruding into the footwear.
Heel lift	The heel lift (or heel-forefoot difference, or pitch) should be generally 1.5–2 cm, and should not exceed 3 cm.
Closure	Adequate closure (or fixation) is needed to keep the foot from sliding forward. Closure should allow secure longer-term fastening and individual adjustment. Laces have long been considered the optimal choice; however, alternatives that are easier to use while still meeting these criteria are available as well, and innovative closures continue to be developed.
Uppers	The uppers consist of the ‘quarter’(hind- and midfoot) and ‘vamp’ (forefoot and toes). Uppers should be made from leather or a combination of materials (similar to sports shoes), with smooth inner lining made from a material that does not harden over time, with limited seams and preferably no seams in the vamp area as they reduce the ability of the leather to give. Uppers should be breathable and durable and have the ability to mould to deformities of the foot without resulting in pressure areas. Uppers can be supple, toughened or stiff. The vamp area should generally remain supple to accommodate the toes. See further Table 3 for specific requirements for the uppers (quarter) for people with a foot deformity.
Toe box	The part of the shoe that covers and protects the toes. This should be supple (unless specific requirements (e.g. for building professionals) require otherwise), and should accommodate the shape of the toes, to avoid any rubbing on the toes.

Features and requirements in this table are based on [10, 15, 16, 32, 33] and authors’ expert opinion; features are depicted in Fig. 1

People at low-risk of foot ulceration can usually be safely accommodated in a wide range of off-the-shelf footwear without specific requirements, provided the footwear is correctly fitted and appropriate for the activity to be undertaken [10, 15, 16, 32, 33]. For people at intermediate- or high-risk of foot ulceration, see recommendations 4-9. When new footwear is provided to a person with diabetes at low-risk of foot ulceration, advise them that a “wear-in” period may be needed where they slowly increase the number of hours per day the footwear is used, and that they should be extra vigilant of their foot health in this period.

Footwear for people with diabetes at intermediate- or high-risk of foot ulceration

Rationale

When a foot deformity, pre-ulcerative lesion is present, off-the-shelf footwear is not likely to be appropriate. Prescribing medical grade footwear (pre-fabricated or custom-made; Table 1) needs to be considered, to accommodate the altered biomechanics. This medical-grade footwear may also include custom-made in-shoe orthoses or insoles. Depending on the foot deformity present or the location of the pre-ulcerative lesion, the footwear requirements algorithms for prescription (Table 4) and footwear modifications (Table 5) should be followed [25, 33]. The outsole, uppers and tongue can be “supple”, “toughened”, and “stiff” [33]. Toughened or stiff features facilitate the even distribution of forces exerted on the foot; unfortunately, no measurable definition of these is available [33].

	Height	Outsole	Uppers (quarter)b	Tongue
Limited joint mobility	Lowa	Toughened	Supple	Supple
Pes cavus	Ankle-high	Toughened	Toughened	Toughenedc
Flexible flat foot with hallux valgus	High	Toughened	Toughened	Toughenedc
Rigid flat foot with hallux valgus	Ankle-high	Toughened	Strong medial support	Toughenedc
Charcot foot	High	Stiff	Toughened	Toughenedc
Hallux or toe amputation	High	Stiff	Toughened	Toughenedc
Forefoot amputation	High	Stiff	Stiff	Stiff

This table is based on [33]

^aUnless a person has limited joint mobility in the ankle joint, in that case use ankle-high or high footwear

^bThe uppers consist of quarter and vamp, the requirements here concern the quarters, as the vamp typically needs to remain supple to accommodate the toes (see further Table 2)

^cWhen a tongue is toughened, it should be padded as well

Med. medial, Lat. lateral. This table is based on [25]

For the blank cells in the matrix, there is either not enough information available, or pressure reduction was not statistically significant, or pressure increased; these modifications are therefore not recommended for these regions of interest

^aPressure reduction was significantly different from 0 (p-values < .05)

^bReplacement with a new top cover of the same material

Footwear for people with diabetic foot ulceration

Considerations on footwear provision

When providing footwear to a person with diabetes, ensure they know their foot risk status and confirm this via an evidence-based screening by an appropriately trained healthcare professional [31]. In addition to the foot screening, other factors that should be considered include the person’s gait pattern, activity levels, occupation, level of mobility, living situation, cultural beliefs, personal goals, and preferences. These factors may influence the possible options for appropriate footwear.

When providing footwear, measure the length, width, depth and girth of the foot the footwear needs to accommodate and ensure that the footwear follows the criteria in Tables 3 and 4. For length and width, we suggest at a minimum using a Brannock measuring device [44]. Although new scanning devices are becoming available to measure foot shape, we still suggest depth requires clinical assessment until accuracy of these devices can be independently quantified, taking into account that people with peripheral neuropathy cannot feel whether depth is accurate. Evaluate the shoe fit with the person in standing position, preferably at the end of the day to ensure that any developing oedema is taken into account. Further considerations in relation to oedema are footwear height (high footwear may have a compression function), outdoor temperature, and changes in oedema treatment.

The timing of footwear provision is important for any footwear that is not pre-fabricated. This becomes even more important when a person with diabetes at intermediate- or high-risk does not have appropriate footwear at a given moment. The longer a person needs to wait to receive appropriate footwear, the more steps they will take in inappropriate footwear, potentially increasing the repetitive stresses on the foot and in turn the risk for foot ulceration. Timing is most important for people with a recently healed plantar foot ulcer. Delivery of their prescribed footwear should be coordinated to a point as close to healing as possible. Ideally, the transition from an offloading device required to heal the ulcer to the preventative footwear is immediate. Any delay in this transition increases the risk of ulcer recurrence. When appropriate preventative footwear is not available for a person with a nearly healed foot ulcer, footwear prescription should be initiated before the ulcer is healed. Prescription can be initiated when foot shape (especially volume), structure and function are not expected to change during the healing process, and should take the manufacturing time-schedule into account. When prescribed footwear cannot be made available immediately when the ulcer has healed, continuation in the offloading device meeting the offloading requirements is needed until the prescribed footwear becomes available. Further, when new footwear is provided to a person with diabetes after healing a foot ulcer, advise them that a “wear-in” period may be needed where they alternate the new footwear with the offloading device that was required to heal the ulcer, and that they should be extra vigilant with checking of their foot health in this period.

In Australia, various state-based schemes are available that may provide financial assistance to people with diabetes who require medical-grade footwear. However, these schemes change over time and discussion of the specific schemes is outside the scope of this guideline.

Considerations on education and adherence to wearing footwear

Early education on the importance of adequate footwear for foot health is important for all people with diabetes. This education needs to continue life-long, and needs to be expanded if a person’s level of risk of foot ulceration increases. The importance of footwear for people with diabetes should be discussed in the context of the individual’s foot risk status and health literacy [45]. Education should aim to increase people’s understanding of the requirements of their footwear to adequately fit, protect and accommodate their feet. This may also include, but is not limited to, education on proper donning of the footwear, the importance of wearing socks in footwear to reduce shear and friction, and explaining the risks to foot health of inappropriate footwear such as slippers and sandals, of narrow heels, of heels higher than 3 cm, and of pointy, flat or hard toe boxes. Education should further focus on motivating people with diabetes at intermediate- or high-risk of foot ulceration to wear their footwear at all times. Footwear can only be effective when it is worn, and adherence to wearing footwear is an important factor in foot ulcer prevention [17, 23, 26, 30].

Achieving better adherence is a challenge, and unfortunately we found no intervention studies on the effect of interventions that aim to increase footwear adherence in people with diabetes [17, 41]. However, we found a number of observational studies investigating reasons for (non-)adherence to footwear [26, 28, 45–49]. An improvement in walking has been described as the most important footwear-related characteristic affecting adherence, while the importance of cosmetic appearance and ease of use varies greatly between people [28, 48]. Rather than focussing on footwear characteristics, it is suggested in various studies that personal perceptions, values and experiences are more important factors to improve adherence [26, 28, 45–49]. A perceived benefit of footwear is associated with increased adherence to wearing the footwear [26], and conversely, a lack of understanding of the need for footwear hinders adherence [28]. Acceptance of the need for footwear is another important factor affecting adherence [28, 46, 47]. This does not only concern accepting the need for footwear, but also acceptance of the person’s underlying diabetic foot disease [28, 46, 47]. Footwear has been described as a “visible representation of the disease”, and people with diabetes at-risk of foot ulceration may choose to moderate their adherence to align with functional requirements and societal norms [28, 46, 47].

These personal values and experiences cannot be assessed using a standardised measurement device. Adequate communication between healthcare professionals and patients is needed to assess these perceptions [45, 50]. For this communication to be effective, it should be person-centred, not footwear-centred [45, 50]. Footwear is very personal, and this should be taken into account during education and communication to ensure maximum acceptance of and adherence with the footwear provided [28, 47, 50].

For people at intermediate- or high-risk of foot ulceration, the importance of adherence to wearing appropriate footwear both indoors and outdoors needs extra attention. People at risk of foot ulceration have been found to perform the majority of their total daily steps indoors [30, 42], while their adherence to wearing their footwear is significantly lower indoors compared to outdoors [30]. To improve adherence, people may need to be made aware of the greater repetitive stresses on their feet when at home resulting from the greater number of steps. It has also been suggested to provide separate footwear for indoor and outdoor use [30]. For people from cultures that may prefer not to wear ‘normal’ footwear indoors, it is suggested that health professionals consider providing indoor footwear that is manufactured to not look like ‘normal’ footwear, which may then be more acceptable to be worn indoors.

Considerations on cultural and geographical differences

In this guideline, we describe features and criteria for footwear for people with diabetes, and specific recommendations based on a person’s foot ulcer risk following the NHMRC risk classification. Footwear is very personal and multiple other factors may need to be taken into account when providing footwear to a person with diabetes and ensuring this footwear is being used. We acknowledge the cultural differences in regard to footwear behaviour, specifically for Aboriginal and Torres Strait Islander people and from other diverse ethnic backgrounds. Furthermore, individuals in geographically rural and remote areas of Australia may have a limited range of footwear options available to them, and limited access to appropriately trained professionals. However, we decided not to provide specific recommendations for different cultures or for people living in rural and remote areas. The criteria and recommendations in this guideline are to be seen as the standards to be achieved, and these recommendations can be used by clinicians in their communications to discuss the footwear requirements for each person’s situation. Specific circumstances may require that a compromise is made to the recommendations, which then may be considered to be better than no footwear at all. However, in our opinion, offering deviations from the standards in this guideline, without supporting evidence and solely based on specific cultural or geographical backgrounds of people, does not align with offering equality of best practice care for all people and may increase the risk of foot ulceration and will weaken this guideline. Rather, we encourage healthcare professionals to use this guideline to discuss footwear requirements with people with diabetes, to try and achieve, if needed, a compromise that is optimal for the person’s situation that most closely aligns with the requirements and recommendations described in this guideline.

Considerations on methodology and terminology

We have based this update of the 2013 guideline on contemporary evidence-based guidelines [10, 14, 15, 31], scientific evidence from systematic reviews [17–22], randomised controlled trials [23, 24], observational studies [9, 25–30, 32–34], and expert opinion, involving experts from eight different disciplines involved in the treatment of people with diabetic foot disease. However, this should not be looked upon as an evidence-based guideline, as we did not follow a specific guideline development methodology. Developing evidence-based guidelines is an extensive and costly process. With recent studies providing a much stronger evidence-base for footwear requirements for people with diabetes we felt that a new footwear guideline to update information in the NHMRC guideline [31] and the 2013 Australian practical guideline on footwear provision [16] was more important than waiting for completion of a full evidence-based guideline. Compared to the recommendations from the 2013 guidelines, some have not changed, and a number of new ones have been added. These include the need for health professionals to prescribe medical grade footwear that has demonstrated plantar pressure reducing effects at high-risk plantar areas for those people with a healed plantar foot ulcer, to review the adequacy of any prescribed footwear every three months, and to treat a plantar foot ulcer primarily with appropriate offloading devices. With this current document, healthcare professionals can immediately start to implement the new footwear evidence to begin to further reduce the large national burden of diabetic foot disease.

The specific footwear requirements are closely related to an individual’s foot risk status. This means that to provide people with diabetes with appropriate footwear, their foot risk status must be assessed first. We followed the classification as provided in the NHMRC guideline [31]. Other countries may use different risk classifications, and we advise healthcare professionals to ensure they use the guideline that is applicable in their own country with regard to foot risk status assessment. In this guideline, we did not separate between intermediate- and high-risk. The first reason for doing so was that some recommendations do not depend on foot risk status per se, but on the presence (or absence) of the specific risk factors of foot deformity or previously healed ulcer. To cover these differences, specific recommendations were needed that applied both to people at intermediate- and high-risk. Further, combining both groups while including specifically targeted recommendations also gives healthcare professionals from other countries the opportunity to match the recommendations in this guideline with their own country’s foot risk status classification system. Finally, the recommendations that did not target a specific risk factor were similar for people at intermediate- or high-risk, which means they could be combined.

As recommended in this guideline, people at intermediate- or high-risk of foot ulceration should be instructed to obtain their footwear from an appropriately trained professional with demonstrated competencies in footwear fitting for people with diabetes. We have not defined ‘appropriately trained’ or ‘demonstrated competencies’, as that was beyond the scope of the current document. However, as a minimum, we suggest an appropriately trained professional should be able to show documented evidence of their training and competency, and should meet the standards of their profession when such standards are available. This way, other healthcare professionals may confidently inform people with diabetes where to obtain their footwear.

The methodology followed to write this guideline does have some limitations. The first, not following a guideline development methodology, has been discussed above. A second is that no patient advocates were involved in its creation. This is a consequence of not following a specific guideline methodology, and we hope that this will be done in the next update of the NHMRC guideline [31]. A third is the limited evidence base with regard to the recommendations for people at low-risk of ulceration [17, 41]. These recommendations might be seen as “good practice statements”, a terminology used in official guideline development for recommendations that are predominantly based on expert opinion and standard of practice, when limited evidence is available [51]. As argued in other publications, it is hoped that researchers and healthcare providers combine efforts to build a stronger research evidence base for these recommendations [41]. Finally, we are unaware of cost-effectiveness information for any of the proposed footwear interventions [17], and thus no such specific information can be added to this guideline. However, a recent Australian cost-effectiveness analysis reported appropriately prescribed footwear as part of a suite of optimal diabetic foot care practice was always cheaper than standard care, and with the high costs associated with foot ulceration [1, 52, 53], it is likely that preventative footwear efforts in this regard will be cost-saving [41].