Innervation of the abductor digiti minimi muscle of the human foot: anatomical basis of the entrapment of the abductor digiti minimi nerve

Abstract

The origin, relationships and innervation of the abductor digiti minimi muscle were determined in 145 human feet, from formaldehyde-fixed cadavers. The muscle arises from both processes of the calcaneal tuberosity, from the plantar aponeurosis and from the septum which separates it from the flexor digitorum brevis muscle. The nerve to the abductor digiti minimi muscle arises next to the origin of the lateral plantar nerve, close to the abductor hallucis muscle, and descends becoming closely related to the medial face of the calcaneus and the deep face of the abductor hallucis muscle. Then, it passes inferiorly through the origin of the quadratus plantae muscle and later divides into two branches for the two heads of the muscle.

Sonographic Visualization of the First Branch of the Lateral Plantar Nerve (Baxter Nerve)

“…In the majority of cases (88%), the FBLPN originates from the LPN and should appear as a 1-to 2-mm-maximal-diameter fascicle arising from the LPN's posterior border ( Figures 6 and 7 and Video 2). 7 Once identified, the FBLPN was followed further caudad to ensure that it entered the AH-QP interval, thus confirming its sonographic identity ( Figure 8 and Video 3). In approximately 12% of individuals, the FBLPN has a more proximal origin from the TN.…”

“…As expected based on prior anatomic descriptions, the FBLPN arose from the LPN just distal to the TN bifurcation, was approximately 2 mm in maximal diameter, and demonstrated a relatively vertical course as it passed caudally within the plane between the AH and QP (ie, AH-QP interval). [4][5][6][7][8][9] The nerve then assumed a more horizontal oblique orientation as it coursed laterally toward the ADM, bordered dorsally by the QP and on its plantar surface by the FDB. As the nerve continued laterally toward the ADM, it passed beyond the lateral margin of the QP, where it was bordered dorsally by the plantar calcaneal surface and the long plantar ligament.…”

“…In approximately 12% of individuals, the FBLPN has a more proximal origin from the TN. 7 In such cases, the LPN cannot Figure 4, the transducer is moved caudad to visualize the TN division, at which point the TN splits into the MPN, LPN, and MCN. A and B, Transducer position (box) and underlying anatomy, respectively (compare with Figure 4, A and B).…”

“…Distally, the nerve may be entrapped at the anterior aspect of the medial calcaneal tuberosity as it passes laterally, bordered by the FDB plantarly and the QP dorsally. [7][8][9] Chronic inflammation of the plantar fascia or FDB from plantar fasciitis or plantar calcaneal spurs can produce conditions favoring FBLPN nerve entrapment at this location. 9 Neuropathy affecting the FBPLN is an uncommon but well-documented cause of chronic heel pain.…”

Sonographically Guided Deep Plantar Fascia Injections

“…This space can also be referred to as the FDB-QP interval. 18,20,22 Specific etiologies of FBLPN entrapment/irritation in this region include plantar fasciitis, plantar calcaneal spurs, and FDB inflammation. 1,3 Recent data from our laboratory have demonstrated that the FBLPN can be sonographically visualized at a proximal location between the AH and QP muscles.…”