Isabella Gigante, Jaap J. van Netten, and Sicco A. Bus, Amsterdam UMC location University of Amsterdam, Department of Rehabilitation Medicine, Meibergdreef 9, Amsterdam, The Netherlands, Amsterdam Movement Sciences, Rehabilitation and Development, the Netherlands, i.gigante@amsterdamumc.nl

Background: Custom-made footwear is recommended for foot ulcer prevention in high-risk individuals with diabetes. For these individuals, the current footwear design principles appear to rely on studies in the non-targeted population like healthy individuals, potentially misrepresenting the true biomechanical and user needs. We aimed to identify knowledge gaps in footwear research for moderate-to-high risk individuals to guide future research.
Methods: A systematic search in the electronic databases PubMed and EMBASE was performed using search terms related to interventions (footwear) and outcomes (biomechanical and user-related). Experimental studies in English were included. Two reviewers screened papers for eligibility. Included publications were categorized into two subject groups: individuals with diabetes at moderate-to-high ulcer risk (i.e. direct evidence) and other populations (i.e. indirect evidence), 16 interventions and 9 outcomes.
Results: Out of 5813 papers identified, 289 met inclusion criteria, with 92% inter-observer agreement. Direct evidence was found in 29 (10%) publications, and indirect evidence in 260 (90%). 24% of the publications studied user-related outcomes, 76% biomechanical outcomes. Most footwear design components had no or limited (<5) studies for direct evidence (Table 1).
Discussion/Conclusion: The knowledge of footwear design principles for individuals with diabetes at moderate- to-high risk of foot ulceration relies mostly on indirect evidence. There is limited scientific evidence on user-related outcomes, a lack of evidence on key biomechanical principles such as shear, and no evidence about the shoe upper. These gaps highlight the need to prioritize research in the target population to obtain more valid outcomes on footwear design efficacy.