Anatomical study of the medial plantar proper digital nerve using ultrasound

To determine whether ultrasound allows precise assessment of the course and relations of the medial plantar proper digital nerve (MPPDN).

This work was initially undertaken in six cadaveric specimens and followed by a high-resolution ultrasound study in 17 healthy adult volunteers (34 nerves) by two musculoskeletal radiologists in consensus. Location and course of the MPPDN and its relationship to adjacent anatomical structures were analysed.

The MPPDN was consistently identified by ultrasound along its entire course. Mean cross-sectional area of the nerve was 0.8 mm² (range 0.4-1.4). The MPPDN after it branches from the medial plantar nerve was located a mean of 22 mm (range 19-27) lateral to the medial border of the medial cuneiform. More distally, at the level of the first metatarsophalangeal joint, mean direct distances between the nerve and the first metatarsal head and the medial hallux sesamoid were respectively 3 mm (range 1-8) and 4 mm (range 2-9).

The MPPDN can be depicted by ultrasonography. Useful bony landmarks for its detection could be defined. Precise mapping of its anatomical course may have important clinical applications.

• The medial plantar proper digital nerve (MPPDN) rises from the medial plantar nerve to the medial side of the hallux. • Because of its particularly long course and superficial position, the MPPDN may be subject to trauma, resulting in a condition known as Joplin's neuroma. • The MPPDN can be clearly depicted by ultrasound along its entire course. Precise mapping of its anatomical course may have important clinical applications.