3.7 Dorsum of Foot

Cutaneous Nerve (506)

Superficial peroneal surfaces mid-leg ® divides at ankle to medial & lateral branches to dorsum

- medial branch further divides to supply medial dorsum of great toe and side of second cleft

- lateral divides to supply 3^rd & 4^th clefts

- saphenous nerve supplies medial foot as far as bunion area (MTP)

- sural nerve supplies lateral side of foot and lateral side of little toe.

- deep peroneal supplies first cleft

Vein

Sole veins drain to dorsal venous arch (over metatarsal heads) ® LSV and SSV at each end.

Like the hand the foot dorsum has little fat ® veins easy to see.

Deep Fascia

Binds down underlying tendons;

Y-shaped fascial thickening inferior extensor retinaculum prevents their bowstringing.

- runs from anterior upper calcaneus laterally and passes in two limbs:

- upper attaches to medial malleolus

- lower to plantar aponeurosis under medial longitudinal arch.

Actually mostly they sling over the tendons to return at the calcaneus; superficial fibres continue to these insertions.

Extensor digitorum brevis (494)

Arises: upper calcaneus and undersurface of inferior extensor retinaculum.

Inserts: tendons to medial 4 toes.

- tendon to hallux has separate name: extensor hallucis brevis; separates early to pass to base of proximal phalanx (great toe has no dorsal extensor expansion)

- other 3 ® dorsal extensor expansions, deep to EDL tendons

Innervation: deep peroneal nerve (S1,S2)

Action: toe extension (especially in the fully dorsiflexed ankle where long extensor less important.

Test: dorsiflex toes.

Dorsalis pedis artery

Runs to base of 1^st inter-MT space ® passes to sole, joins lat plantar artery forming plantar arch. Pulse felt lateral to EHL tendon (malleolar midpoint on navicular and intermediate cuneiform), is medial to nerve & is crossed by EHB.

- occasionally replaced by enlarged perforating peroneal artery in front of lateral malleolus.

3 named branches:

i) lateral tarsal a.: runs lateral beneath EDB to that muscle and underlying tarsal bones

ii) arcuate a: runs lateral beneath EDB over bases of metatarsals ® dorsal metatarsal arteries to each of the lateral three clefts. Each of these ® perforating branch to communicated with plantar arch at posterior and anterior ends of intermetatarsal spaces (Accompanied by perforating veins)

iii) 1^st dorsal metatarsal artery: just before dorsalis pedis enters sole ® 1^st cleft and medial side of foot dorsum.

Deep peroneal nerve

Crosses tibia lateral to artery, midway b/n malleoli.

- passes forward, deep to tendons, on lateral side of dorsalis pedis.

- ® pierces deep fascia to supply 1^st cleft.

- ® branch curves laterally to EDB (and underlying periosteum & jts).

- ® branch to first dorsal interosseus.