The effects of foot and ankle devices on balance, gait and falls in adults with sensory perception loss: a systematic review protocol
Authors: Paton Joanne , Collings Richard , Glasser Sam , Kent Bridie 
Published: December 2014

Review question/objective
The objective of this systematic review is to synthesize the best available evidence regarding the effects (positive and negative) of foot and ankle devices on: 1) balance, 2) gait, and 3) falls in adults with sensory perception loss. The results of this review will be used to inform the development of an insole for people at increased risk of falls due to diabetic neuropathy.
More specifically the review will synthesize the best available evidence regarding: a) the effect of foot and ankle devices (including footwear, insoles and ankle foot orthosis) on any clinical or laboratory measure of balance and gait in adults with sensory perception loss; and b) the effect of foot and ankle devices (including footwear, insoles and ankle foot orthosis) on any measure of fall frequency or incidence in adults with sensory perception loss.

Background
It is reported that as people age, postural control declines.1,2 This has been attributed in part to reduced somatosensory input including visual, proprioceptive and vestibular information, and musculoskeletal change, for example, lower limb muscle weakness.3 These changes, which are common in the elderly population, are accelerated in adults with sensory perception loss,3,4 further increasing their risk of falls and injury.5-7 Sensory perception loss is commonly associated with a number of chronic conditions including alcoholism, vitamin B12 deficiency, autoimmune disease and diabetes.8 Diabetes is the most common cause of sensory perception loss, with peripheral neuropathy affecting up to 50% of those with the condition.9

Falls are a major concern for adults with sensory perception loss. Most falls occur during weight bearing activities and are preventable.7 One potential modifiable external risk factor for falls is the interface between the foot and supporting surface. This interface most often takes the form of footwear or insoles, but can also include the supporting surface material if barefoot.10 It is reported that 75% of people who experience a falls-related hip fracture are wearing inappropriate footwear.11 Any device that comes in contact with the foot or ankle including footwear and insoles has the potential to increase or reduce the risk of falls.
Adults with sensory perception loss, particularly those with diabetic peripheral neuropathy, are at increased risk of developing foot ulceration.12 Therefore it is common practice within the clinical environment to provide people with peripheral neuropathy with therapeutic footwear and insoles as a means of reducing plantar loads and foot ulcer risk whilst walking.13 The provision of footwear and insoles for people with diabetic neuropathy is supported by the National Institute for Health and Care Excellence (NICE) guidelines and a Cochrane review of the literature.14,15 This best available evidence investigating the effectiveness of footwear and insoles for people with diabetes and peripheral neuropathy has until now focused entirely on ulcer prevention with no consideration given to the possible secondary effect on balance or falls risk.13,15 One aim of this proposed review is to raise awareness of the issue of balance and falls risk for consideration among professionals tasked with prescribing footwear and insoles to people with sensory perception loss.
Insoles and ankle foot orthosis contained within shoes are known to alter gait kinetics and kinematics.16,17 Whilst the mechanism of influence is unclear, favored theories take either a mechanical or sensory approach. The mechanoreceptors found in the plantar surface of the foot provide important pressure sensory mapping information about changes in pressure related to body position. This sensory threshold is reduced in older people18,19 and further compromised in those with sensory perception loss.3,20 Insoles are the interface between the plantar foot and floor. They are well placed to modify the transmitted sensory information, to dampen or enhance any remaining sensory feedback.21 The shoe, or alternatively an ankle foot orthosis, forms an envelope around the foot to provide a dynamic structural housing within which locomotion can occur. This housing can restrict or facilitate joint motion, generating a mechanical influence on lower limb muscle and foot function that could in turn affect lower limb stability and balance.22 Whilst this review does not aim to focus on the mechanism of influence by which insoles, footwear or other similar devices may affect balance control, an analysis of studies recruiting participants with known sensory deficit may determine if there is a pathology -specific change in the contribution of this mechanical versus sensory control.
An initial search of literature identified three reviews with a focus on the effect of footwear and orthisis on balance in older people.10,23,24 Electronic databases searched were MEDLINE, EMBASE (OVID) and CINAHL, AMED (EBSCO), JBI Database of Systematic Reviews and Implementation Reports, from inception to 2013. A further search of grey literature including government documents, the Cochrane Central Register of Controlled Trials, Google Scholar and a thesis database (http://www.thesis.com) was conducted. Initial MESH and key terms used related to foot orthosis and insoles, footwear and shoes, ankle foot orthosis and ankle braces, postural balance and body sway, gait and walking pattern, stabilizing and destabilizing, accidental falls, older persons, nervous system disorders, diabetes and neuropathy.

Table 1 presents a comparison of the existing reviews including details of review objectives, inclusion and exclusion criteria, search strategy and critical appraisal tools used. The first, a systematic review considered papers published up to the end of 2004.23 The review included a broad participant population of older people and those with peripheral nervous system disorders.23 This strategy highlights the clinical relevance of balance deficits in people with peripheral nervous system disorder, but acknowledges the lack of primary research incorporating this patient group at the time of the review. Another review considered studies investigating the effect of insoles on balance performance and gait in an effort to theorize on the mechanism by which insoles influence balance.24 This review included participants over 60 years of age without differentiation between healthy individuals and those with pathological conditions known to affect balance.24 The authors excluded studies testing lower limb interventions other than insoles and included only laboratory-based outcome measures of balance.24 The resulting report provides a proof of concept summary, with limited transferability to clinical practice. The final systematic review focused on the effect of different footwear features on balance and falls risk in the older population.10 This review excluded studies investigating therapeutic footwear (commonly provided to people with neuropathy) or populations with a specific medical condition.10 Despite the clinical relevance of sensory perception loss, none of the reviews have to date provided evidence pertinent to this patient group. In the real world setting, insoles and other foot and ankle devices are worn inside footwear to function as a single unit to exert an influence on balance and falls risk. Clinically it is ill-advised to prescribe a foot orthosis without also considering how the footwear within which the orthosis will be contained may affect balance and falls risk. Therefore whilst other reviews have been limited to one category of intervention, this proposed review will include all foot and ankle devices and footwear with the aim of increasing the usefulness and relevance of the review results to the treatment approach for the target population.
Studies investigating the effects of insoles, footwear and other foot and ankle devices on balance, fall into two categories. Those using laboratory outcome measures of balance24 and those using clinical based measures of balance or mobility.25,26,27 This review will consider both categories of outcome measures as having predictive relevance to falls risk.
It is commonly accepted that body oscillations during normal quiet standing are indicative of postural stability.28,29 Smaller amplitudes and lower speeds of body sway are considered representative of better postural stability in terms of less effort needed to maintain posture.28 The force platform method of using centre of pressure amplitude and speed as a measure of body sway during quiet standing has been previously used to evaluate the effect of insoles and footwear on the postural control in static conditions.24 Traditional sway parameters include velocity of Centre of Pressure (CoP) displacement (m/s). In a review of stability parameters, velocity of CoP displacement was shown to be the best consistent measure of differences between interventions.29 Other relevant measures of balance traditionally used in trials to predict falls included mean speed and amplitude of movement of the centre of pressure in both the medial lateral and anterior posterior directions.28

A number of alternative approaches have been developed to enable clinicians to measure balance and falls risk in the real world clinical setting.30-31 Most of these tests involve challenging postural control in a way that is representative of day-to-day tasks to give an indication of an individual's falls risk whilst undertaking activities of daily living. Examples of commonly used balance tests include functional reach and the berg balance scale.30-31 The functional reach test requires the participant to stand with their arms positioned at 90 degrees to their body and the distance they are able to reach forward is then measured.30 This test is a predictor of falls and sensitive to change following the introduction of an intervention.32-33 The berg balance scale incorporates 14 tasks such as sit to stand, single leg stance and turning 360 degrees.31 The subject's ability to complete each task is scored 0 to 4 with a maximum score of 56 representing good balance.31 There is mixed evidence to suggest that the berg balance scale is predictive of falls.34 Changes in gait have been associated with falls particularly in the older population.1 Older fallers have been found to adopt a more conservative gait pattern involving reduced velocity and step length, greater step-to-step variability and stance width.1 The spatio-tempero parameters of gait are therefore commonly used as an outcome measure in intervention studies intended to reduce the risk of falling.26,35,36 This review will also therefore consider spatio-tempero parameters of gait as a relevant outcome measure.
The results of this review will be used to inform the design and development of a balance enhancing insole for people with diabetes and neuropathy. An initial search of literature identified a limited number of relatively small-scale studies involving participants with diabetes and neuropathy. Whilst falls are recognised as a concern for this patient group, prevention of foot ulceration is a topic that until recently has taken priority for researchers working in the area of diabetic foot care. Therefore the scope of the review will be expanded to include studies recruiting from the wider insensate population. Balance, mobility and falls are of primary importance for this wider population, and a number of relevant published studies are available for review.36-41 In the first instance the information gained from this review will be used to consider the possible effect of current diabetic insole design on balance and falls risk in people with sensory perception loss. Then the type of insole and footwear shown to enhance balance or reduce falls risk within those with sensory perception loss will be reviewed to inform the development of the new insole design.
Defining the type of footwear or insoles that contribute to falling or influence gait and balance in adults with sensory perception loss will offer direction to future research and guide therapeutic footwear and insole provision.