Anatomic basis for a new ultrasound-guided, mini-invasive technique for release of the deep transverse metatarsal ligament

Abstract

Introduction: Morton's neuroma is an entrapment neuropathy of the third common plantar digital nerve, caused by the deep transverse metatarsal ligament (DTML). Minimally invasive or percutaneous surgery is a very common procedure, but surgical effectivity of this technique remains controversial. The goal of our study was to prove the effectiveness and safety of a new ultrasound-guided technique for DTML-release in a cadaver model.

Materials, methods, and results: The DTML was visualized in 10 fresh frozen donated body to science-feet (eight male and two females, five left and five right) using an US device (GE Logic R7; 13 MHz linear probe, Madrid, Spain). Consecutively, minimally invasive ultrasound-guided surgery was performed. Exclusion criteria of the donated bodies to science were previous history of forefoot surgery and space occupying mass lesions. The complete release of the ligament was achieved in all specimens without damage of any important anatomical structures as proven by anatomical dissection.

Conclusions: The results of this study indicate that our novel approach of an ultrasound-guided release of the DTML is safer and more effective compared to blind techniques. The DTML could reliably be visualized and securely cut through a dorsal, minimally invasive surgical incision of only 2 mm.

Keywords: Morton's neuroma; deep transverse metatarsal ligament; minimally invasive; ultrasound.

FIGURE 1

Frontal plane view of the intermetatarsal space at the level of third and fourth metatarsal heads (3°; 4°) showing topographical relationships. Red arrowheads: transection site of DTML (17), 1: extensor digitorum brevis tendon, 2: extensor digitorum longus tendon, 3: triangular adipose‐fascial complex carrying superficial nerves and vessels, 4: intermetatarso‐phalangeal bursa, 5: deep dorsal fascia, 6: vertical lamina of extensor aponeurosis, 7: flexor digitorum brevis tendon, 8: common digital plantar neurovascular bundle, 9: flexor digitorum longus tendon, 10: longitudinal fascicle of plantar aponeurosis, 11: plantar monticuli, 12: pretendinous fat compartment, 13: vertical extension of plantar aponeurosis forming the pretendon flexor space for adipose cushion, 14: Fibrous flexor tendon sheaths, 15: plantar plate, 16: tendon of lumbrical muscle, 17: DTML, 18: tendon of interosseous muscle. Figure based on the work of Stecco et al. (Stecco et al., 2015) [Color figure can be viewed at wileyonlinelibrary.com]

FIGURE 2

(a) The figure shows the positioning of the instruments—buttoned probe dorsal, US transducer plantar. (b) Fluoroscopy of the foot before the DTML release; dotted line shows approximate area of the DTML, buttoned probe also visible. (c) Longitudinal scan of the DTML: The buttoned probe (BP) pushes the ligament plantarly during the surgical procedure at the third intermetatarsal space [Color figure can be viewed at wileyonlinelibrary.com]

FIGURE 3

(a) From medial to lateral, (b) from proximal to distal: US‐appearance of the deep transverse metatarsal ligament (DTML) in two planes: the typical “white–dark–white” pattern of a ligament can be seen with hyperechoic borders (“white”), the substance of the rest of the ligament appears hypoechoic (“dark”) with just a few echogenic speckles. The mean thickness measured was 1.1 mm. (a) transverse scan of the DTML: red arrowheads (transection zone); plantar plate (PP); flexor digitorum longus tendon (FDLT); plantar aponeurosis (PF); yellow arrowhead (neurovascular bundle) (b) longitudinal scan of the DTML: The buttoned probe (BP) pushes the ligament plantarly during the surgical procedure [Color figure can be viewed at wileyonlinelibrary.com]

FIGURE 4

Confirmation of a complete release of the deep transverse metatarsal ligament (DTML) using fluoroscopy—left before, right after the ultrasound‐guided surgical release with widening the third intermetatarsal space [Color figure can be viewed at wileyonlinelibrary.com]

FIGURE 5

Anatomical specimen showing the DTML and its topographical situation. From lateral to medial: *DTML: deep transverse metatarsal ligament, #common plantar digital nerve, DIM: dorsal interosseous muscle, EDBT: extensor digitorum brevis tendon, EDLT: extensor digitorum longus tendon [Color figure can be viewed at wileyonlinelibrary.com]