Fascia and boundaries of the subfascial space
The proper fascia of the dorsum of the foot is a direct continuation of the crural fascia (fascia cruris). It is firmly fixed laterally to the 1st and 5th metatarsal bones, forming a strong receptacle for deeper structures. Important tendons heading toward the foot are enclosed between the leaves of this fascia: the tendons of the long extensors and the tibialis anterior muscle.
The dorsal subfascial space itself has clear anatomical boundaries:
- Proximal boundary: projected onto the anterior surface of the ankle joint region (just above the inferior extensor retinaculum — retinaculum mm. extensorum inferior).
- Distal boundary: runs at the level of the tarsometatarsal joints.
- Deep (inferior) wall: formed by the deep fascia, which tightly covers the metatarsal bones and the dorsal interosseous muscles located between them (mm. interossei dorsales).
Inside the space are synovial sheaths that surround and protect the tendons of the long extensors of the toes and the tibialis anterior muscle from friction.
Contents of the dorsal space of the foot
In the subfascial cellular space, muscle elements and neurovascular formations lie in a single anatomical layer.
The muscular apparatus includes the short extensors of the toes:
- Extensor hallucis brevis (m. extensor hallucis brevis).
- Extensor digitorum brevis (m. extensor digitorum brevis).
Along with these muscles run the main nourishing vessels of the region — the dorsalis pedis artery (a. dorsalis pedis) and its accompanying deep veins, as well as nerve trunks. On the surface of the fascia and in the subcutaneous tissue are elements of the superficial venous system, in particular, the dorsal venous arch of the foot (arcus venosus dorsalis pedis), as well as the great saphenous vein (v. saphena magna).
Topography and branching of the dorsalis pedis artery
The dorsalis pedis artery (a. dorsalis pedis) is a direct continuation of the anterior tibial artery. Its most important clinical feature is its superficial location. The artery lies lateral to the tendon of the extensor hallucis longus (tendo m. extensoris hallucis longi). In this zone, the vessel is not covered by muscles or tendons, so its pulsation is traditionally determined here.
At the level of the tarsus, the artery gives off a number of branches:
- Medial tarsal arteries (aa. tarsales mediales) are several small branches running medially.
- Lateral tarsal artery (a. tarsalis lateralis) is a large trunk directed laterally. Its terminal branch anastomoses with the perforating branch of the fibular artery (participating in the formation of the lateral malleolar network). Distal branches of this vessel connect with the arcuate artery at the level of the tuberosity of the 5th metatarsal bone.
- Arcuate artery (a. arcuata) arises at the level of the tarsometatarsal joints, runs laterally, and gives off dorsal metatarsal arteries (aa. metatarsales dorsales), which then divide into proper dorsal digital arteries.
The main trunk ends with two terminal branches: the first dorsal metatarsal artery (running to the first interdigital space) and the deep plantar artery (a. plantaris profunda). The latter penetrates through the muscles of the first intermetatarsal space to the sole, where it connects with the lateral plantar artery, forming the plantar arch.
Nerves and additional structures
The main nerve of this region is the deep fibular nerve (n. fibularis profundus). Topographically on the dorsum of the foot, it is located internally (medially) to the dorsalis pedis artery. At the level of the intermalleolar line, it gives off a motor branch that accompanies the lateral tarsal artery and ensures the operation of the short extensors of the toes. Sensory branches innervate a strictly localized area of skin — the contacting surfaces of the 1st and 2nd toes.
When studying anatomical preparations, one can also encounter elements that are often cut away during dissection: the superficial fibular nerve (n. fibularis superficialis) and the saphenous nerve (n. saphenus). In addition, the tendon of the fibularis tertius muscle runs in the lateral part of the foot (m. fibularis tertius).
Briefly: answers to topical questions
What forms the walls of the dorsal subfascial space of the foot?
The walls of the dorsal subfascial space of the foot are formed by the proper and deep fascia.
- Superior wall — proper fascia of the dorsum of the foot (fascia dorsalis pedis), which attaches laterally to the 1st and 5th metatarsal bones.
- Deep (inferior) wall — deep fascia covering the metatarsal bones and the dorsal interosseous muscles (mm. interossei dorsales).
Which nerves provide sensory innervation to the skin of the dorsum of the foot, in addition to the deep fibular nerve?
Sensory innervation to the skin of the dorsum of the foot, in addition to the deep fibular nerve, is provided by branches of the superficial fibular, saphenous, and sural nerves.
- Superficial fibular nerve (n. fibularis superficialis) — innervates most of the skin of the dorsum of the foot via the medial and intermediate dorsal cutaneous nerves.
- Saphenous nerve (n. saphenus) — innervates the medial margin of the foot.
- Sural nerve (n. suralis) — innervates the lateral margin of the foot and the 5th toe (including the lateral dorsal cutaneous nerve).
Which veins form the superficial venous network of the dorsum of the foot?
The superficial venous network of the dorsum of the foot (rete venosum dorsale pedis) is formed by small subcutaneous veins collecting blood from the distal parts.
Its formation involves:
- Dorsal digital veins of the foot (vv. digitales dorsales pedis).
- Dorsal metatarsal veins of the foot (vv. metatarsales dorsales pedis).
- Dorsal venous arch of the foot (arcus venosus dorsalis pedis) — is the main collector and part of this network.
Medial and lateral marginal veins depart from the network.
Which tendons pass in the synovial sheaths under the proper fascia of the dorsum of the foot?
The tendons of the long extensors and the tibialis anterior muscle pass in synovial sheaths under the proper fascia of the dorsum of the foot.
- Tendon of the tibialis anterior muscle (tendo m. tibialis anterior).
- Tendon of the extensor hallucis longus (tendo m. extensoris hallucis longi) — occupies a middle position.
- Tendons of the extensor digitorum longus (tendines m. extensoris digitorum longi) — are located laterally.
To memorize the syntopy of the neurovascular bundle: the nerve always "hides" inward (medially) from the pulsating dorsalis pedis artery.
Class and exam questions
Where is the correct place to palpate the pulse on the dorsum of the foot?
Pulsation is determined lateral to the tendon of the extensor hallucis longus, since in this place the dorsalis pedis artery lies superficially and is not covered by muscles.
What does the lateral tarsal artery anastomose with?
It connects with the perforating branch of the fibular artery (forming the lateral malleolar network) and with the arcuate artery at the level of the tuberosity of the 5th metatarsal bone.
Which nerve provides sensory innervation to the skin of the first interdigital space?
The skin of the contacting surfaces of the 1st and 2nd toes of the foot is innervated by branches of the deep fibular nerve (n. fibularis profundus).
How are the vessels of the dorsum of the foot connected to the blood supply system of the sole?
The connection is carried out through the deep plantar artery, which passes through the first intermetatarsal space to the sole and anastomoses with the lateral plantar artery.
What else to study on this topic
- Formation of the lateral malleolar network (rete malleolare laterale)
- Topography and function of the short extensors of the toes
- Anatomy and role of the synovial sheaths of the ankle joint tendons
- Structure of the dorsal venous arch of the foot (arcus venosus dorsalis pedis)
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