A Multi‐Axis Plantar Load Measurement Platform for the Assessment of Foot Disorders: Comparison of Patients With Psoriatic Arthritis to a Healthy Control Cohort

BACKGROUND: Accurate assessment of plantar loading, including shear forces, is crucial for understanding foot pathologies such as dactylitis in psoriatic arthritis (PsA). Existing devices predominantly measure plantar pressures, neglecting important shear stresses which may initiate dactylitis. This study presents a novel multi-axis plantar load measurement platform to address this gap. METHODS: The study utilised a newly developed plantar load measurement system, comprising a Hall-effect-based magnetic sensing array, custom data logging electronics, and tailored data processing software. The system's efficacy was evaluated in a pilot feasibility study involving patients with PsA with no, current, or previous dactylitis, and healthy controls. Participants walked barefoot on the platform, capturing plantar shear and pressure data. FINDINGS: Shear stresses were notably higher in the second to fourth rays compared to other regions, particularly in the left foot, aligning with the hypothesis that repetitive local trauma might initiate dactylitis in PsA. However, no consistent differences in stresses were observed between diagnostic groups, likely due to small sample sizes and gait alterations associated with pain. A marked asymmetry was observed between the right and left feet, suggesting dominant-foot placement effects. INTERPRETATION: The new platform demonstrates potential clinical utility in capturing comprehensive foot-loading profiles, including critical shear stresses previously under-assessed. Although the current pilot study was limited in number, the results support the theory that local mechanical stresses may contribute to PsA-related dactylitis. Future larger-scale studies are needed to clarify these findings and overcome limitations related to altered gait patterns due to foot pain.