Medial Plantar Proper Digital Nerve Thickening – a Sonographic Finding in Volunteers Without Joplin’s Neuroma

Purpose: Thickening of the medial plantar proper digital nerve (MPPDN) along the medial aspect of the big toe is frequently observed incidentally during high-resolution ultrasound examinations in asymptomatic individuals. However, the clinical significance of these findings remains unclear, as no study has definitively linked them to symptoms. Although the localization and visualization of the medial plantar nerve using ultrasound have been documented, its cross-sectional area has not yet been utilized to assess thickening at this specific site. The study aimed to assess the frequency and specific locations of MPPDN thickening in asymptomatic individuals and to identify associated characteristics. Materials & Methods: In this prospective study, high-resolution ultrasound examination of the MPPDN was performed on asymptomatic volunteers. The cross-sectional areas and their changes along the course of the nerve are evaluated descriptively. Potential contributing demographic factors in participants are captured. Results: 56 asymptomatic volunteers, 30 women and 26 men (median age: 28, range: 20-69) participated in this study. 22 individuals (39.3%) showed thickening of the MPPDN at the interphalangeal joint either in one or both feet. More participants above the median population age of 28 showed thickening of the MPPDN (15 [57.7%] versus 7 [23.3%] p = 0.009). Conclusion: Thickening of the MPPDN is frequently observed in asymptomatic individuals, with the likelihood of these findings increasing with age. The pathological significance should however not be overestimated and should be assessed in a clinical context.