Preliminary Reference Values for Plantar Fat Pad Thickness Beneath the Metatarsal Heads and Its Relationship with Body Mass Index.

Introduction and Objectives: The thickness of the plantar fat pad (PFP) beneath the metatarsal heads may play a protective role in preventing forefoot disorders such as metatarsalgia. However, reference values for plantar adipose tissue thickness in this region among healthy individuals are currently unavailable. Therefore, the aim of this study was to determine, by means of ultrasound imaging, the thickness of the PFP beneath the five metatarsal heads and to analyze its possible relationship with body mass index (BMI). Materials and Methods: Thirty-five young adults (17 males and 18 females) with neutral feet, free from deformities or pain, participated in the study. Using a VINNO E35 ultrasound device, the thickness of the PFP beneath each of the five metatarsal heads was quantified. A linear transducer was positioned longitudinally along the axis of each metatarsal. The distance between the dermis and the flexor tendon was measured from the second to the fifth metatarsal heads, and from the fibular sesamoid for the first metatarsal head. Results: The central forefoot showed the greatest PFP thickness (2nd metatarsal head, 7.1 ± 0.9 mm; 3rd metatarsal head, 6.9 ± 0.9 mm). No significant differences in PFP thickness were found between sexes. However, a positive correlation was observed between BMI and PFP thickness at the fourth metatarsal head (r = 0.358, p = 0.035). Conclusions: The study demonstrated greater PFP thickness beneath the second and third metatarsal heads, with no significant sex-related differences. These findings indicate a consistent anatomical pattern independent of sex in young, healthy individuals. Moreover, a moderate influence of BMI was identified at the fourth metatarsal head, which could represent a potential protective mechanism against forefoot overload.