Associations Between Diabetic Foot Deformity and the Intrinsic Foot Muscles: A Systematic Review

Diabetic foot deformities such as claw toes are debilitating complications. It has been generally accepted that this results from atrophy of the intrinsic foot muscles (IFMs), despite this relationship being underexplored. However, recent diagnostic imaging studies are finding some associations between diabetic intrinsic foot muscles and foot deformity. This new information requires a thorough review of the evidence. Our aim is to systematically review the current literature to investigate any associations between diabetic foot deformity and intrinsic foot muscle changes and review their significance. Electronic databases Medline, Embase, Scopus, CINAHL, and Web of Science were searched on 6 May 2020 for all years until 2020. The search was re-run on 26 June 2023 with dates ranging from 2020-2023. Human data studies on adults in English, investigating diabetes, foot deformities and intrinsic foot muscles were included for review. PROSPERO registration was approved on 24 July 2020. Eleven papers out of 1779 met the inclusion criteria. For the updated search, two papers out of the 226 met inclusion criteria. All were assessed for quality using the STROBE criteria and the Newcastle and Ottawa Scale. Six reported various correlations between intrinsic foot muscles and claw/hammer toe deformity measurements. Three papers reported limited or no associations. Three papers investigated medial column deformity (MCD); two found a significant correlation to intrinsic foot muscle atrophy. Overall, there is a weak association between diabetic foot deformity and intrinsic foot muscle atrophy and intermuscular adipose tissue infiltration.