Effects of 3D printed somatosensory stimulation foot orthoses with customized knob heights on postural balance and gait in older adults.

Abstract

Age-related declines in sensory and musculoskeletal function contribute to impaired balance in older adults. Although foot orthoses are commonly recommended, conventional designs often fail to effectively stimulate plantar mechanoreceptor to enhance sensory feedback for postural control. This study aimed to evaluate the immediate effectiveness of 3D-printed, site-specific somatosensory stimulation foot orthoses (SSFO) with customized knob heights, compared to placebo foot orthoses (PFO) without stimulating knobs and conventional flat foot orthoses (FFO). We assessed postural balance during static standing and walking across varied treadmill slope angles. In this repeated measures design study, 23 older adults wore each orthosis type in a randomized order. Postural control and stability were quantified using center of pressure (CoP) trajectories, plantar force/pressure distributions, and subjective ratings of tactile perception and satisfaction. SSFO significantly reduced anteroposterior CoP root mean square (RMS) and range during standing with eyes open compared to both PFO and FFO. During walking, main effects of orthosis type on CoP trajectories were not significant. However, statistical parametric mapping revealed that SSFO reduced mediolateral CoP displacement and increased ground reaction forces during specific phases of uphill walking. SSFO also decreased plantar forces at toes, forefoot, and rearfoot while increasing midfoot loading under certain conditions. Subjective ratings indicated greater perceived effectiveness and safety for SSFO compared to the other orthoses. These findings highlight the potential of site-specific customized SSFO to enhance somatosensory feedback and improve postural balance in older adults. This novel orthotic approach merits further investigation into long-term effects and optimal stimulation strategies.