Anterior Compartment of the Leg Flashcards
Anterior compartment enclosed by
- Dense fascia
- Bone
- Interosseous membrane
Anterior compartment is susceptible to
- Compartment syndrome
Anterior compartment major blood supply
- Anterior tibial artery
Muscles of anterior compartment innervation
- Deep fibular nerve (L4-S1)
Anterior compartment tendons have
- Synovial sheath as they pass ankle
- Visible/palpable at ankle with contraction
Function of anterior compartment muscles
- Ankle dorsiflexion
- Extend digits
Muscles of the anterior compartment (names)
- Tibialis anterior
- Extensor digitorum longus
- Extensor hallucis longus
- Extensor hallucis capsularis
- Fibularis (peroneus) tertius
Tibialis anterior
- Largest anterior muscle
- Visible and palpable proximally
- Tendon is palpable and visible as it crosses the ankle joint
Tibialis anterior origin
- Lateral tibial condyle
- Upper 2/3 lateral surface of tibial shaft
- Interosseous membrane
- Crural fascia
Tibialis anterior insertion
- Medial cuneiform
- 1st met base (metatarsal tubercle)
- Medial plantar surfaces for both
Tibialis anterior function
- Dorsiflex and invert foot
- Supinate subtalar joint
Extensor digitorum longus origin
- Lateral tibial condyle
- Superior ¾ of fibular shaft
- Interosseous membrane
- Crural fascia
Extensor digitorum longus insertion
- Divide into 4 slips (digits 2-5)
- Dorsal bases of middle/distal phalanges (digits 2-5)
- Contributes to extensor expansion (digits 2-5)
Extensor digitorum longus function
- Digit extension/dorsiflexion (proximal/distal interphalangeal and metatarsophalangeal joints)
- Helps with dorsiflexion/eversion (subtalar pronation)
Extensor hallucis longus
- Deep to TA and EDL
- Superficial at distal leg/ankle
- Tendon between TA and EDL at ankle joint
Extensor hallucis longus origin
- Middle ½ anteromedial aspect of middle fibular shaft
- Interosseous membrane
- Originates more distal than TA and EDL
Extensor hallucis longus insertion
- Dorsal base of distal phalanx (1st digit)
Extensor hallucis longus function
- Extend/dorsiflex 1st digit (hallux)
Extensor hallucis capsularis origin
- Medial aspect of EHL tendon or muscle (sometimes TA)
Extensor hallucis capsularis insertion
- Dorsomedial aspect of 1st MPJ capsule
Extensor hallucis capsularis function
- Tenses capsules during extension
- Prevents capsular impingement
Fibularis (peroneus) tertius
- Can be absent in people
- Passes anterior to lateral malleolus
Fibularis (peroneus) tertius origin
- Inferior ¼ medial fibular shaft
- Interosseous membrane
- Can also originate from the EDL muscle
Fibularis (peroneus) tertius insertion
- Dorsal aspect of base and shaft of 5th metatarsal
- Sometimes the base of the 4th metatarsal
Fibularis (peroneus) tertius function
- Foot dorsiflexion and eversion
- Subtalar pronation
Synovial sheaths of anterior compartment muscle tendons
- Tibialis anterior
- Extensor hallucis longus
- Extensor digitorum longus and fibularis tertius
Tibialis anterior synovial sheath
- Begins proximal to SER (transverse crural ligament)
- Ends between oblique bands of IER (cruciate crural ligament)
- Begins/ends most proximally
- Within the SER and oblique superomedial band of IER
Extensor hallucis longus synovial sheath
- Begins immediately proximal to oblique superomedial band of IER (level of medial malleolus)
- Ends at the 1st metatarsal base
- Within the IER
- Ends most distally
Extensor digitorum longus/fibularis tertius synovial sheath
- Share a synovial sheath ( 4 tendons of EDL and 1 of FT)
- Begins just proximal to oblique superomedial band of IER
- Ends at level of 5th metatarsal base
- Within the IER
Extensor Retinacula
- Hold extensor tendons in place over the extensor surface of ankle joint
Superior extensor retinaculum (transverse crural ligament)
- Thickening of crural fascia (fascia cruris)
- Attaches to anterior aspect of the tibia and fibula distal shafts
- TA within the retinaculum, the rest pass deep
Inferior extensor retinaculum (cruciate crural ligament)
- Thickening of crural fascia and deep fascia over foot dorsum
- Y shaped band with a stem and 2 oblique medial bands
- Continuous with inferior fibular retinaculum
Tendons of anterior compartment muscles pass within
- The inferior extensor retinaculum
Frondiform ligament
- Stem of the Y shaped band of the inferior extensor retinaculum
- Stem of the Y is lateral
Lateral attachment (frondiform ligament)
- Lateral talar neck
- Superior calcaneus within the sinus tarsi
Medial attachment (frondiform ligament)
- Oblique superomedial band: Anterior aspect of distal medial malleolus
- Oblique inferomedial band: Plantar aspect of medial cuneiform/navicular
Blood supply to anterior and lateral compartment
- Anterior tibial artery (terminal branch of popliteal)
- Passes through proximal opening in the interosseous membrane
- Enters anterior compartment
Anterior tibial is located between
- TA and ED muscles in proximal leg
- Located between TA and EHL in the distal leg
- Distal ankle EHL tendon crosses over artery
Anterior tibial artery becomes
- Dorsalis pedis after ankle
- Dorsalis pedis is located between EDL and EHL
A small anterior tibial artery can be replaced by
- Perforating branches from posterior tibial
- Perforating or fibular artery
Anterior tibial artery (terminal branch of popliteal)
- Branches off near inferior border of popliteus
- Passes through superior opening of interosseous membrane
- Enters anterior compartment
Branches of anterior tibial artery
- Anterior/posterior tibial recurrent arteries
- Muscular branches
- Anterior medial/lateral malleolar arteries
- Dorsalis pedis (continuation)
Anterior compartment venous drainage
- Anterior tibial vein + posterior tibial vein > Popliteal vein > Femoral vein
Deep fibular nerve (L4-S1) pathway
- Branches from common fibular in the lateral compartment
- Enters anterior compartment through anterior intermuscular septum
- Descends along anterior surface of the interosseous membrane (with anterior tibial artery)
Deep fibular nerve (L4-S1) descends along anterior surface of interosseous membrane
- Lateral to artery in both the leg and ankle
- Enters dorsum of foot by passing deep to extensor retinacula
Deep fibular nerve (L4-S1) supplies
- Anterior compartment muscles
- Foot dorsum muscles
Lateral terminal branch of deep fibular nerve innervates
- EHB
- EDB
- Joints of lateral foot
Medial terminal branch of deep fibular nerve pathway
- Communicates with superficial fibular nerve (communicating branch of superficial fibular nerve)
- Follows dorsalis pedis and 1st dorsal metatarsal arteries
Medial terminal branch of deep fibular nerve innervates
- 1st dorsal interossei muscle
- Joints of medial foot
Branches of medial terminal branch
- Proper dorsal digital nerve 2
- Proper dorsal digital nerve 3
Proper dorsal digital nerve 2
- Cutaneous innervation of dorsolateral hallux
Proper dorsal digital nerve 3
- Cutaneous innervation of dorsomedial 2nd toe
Injury to deep fibular nerve symptoms
- Footdrop (increased tripping with gait)
- Weak/loss of toe extension, ankle dorsiflexion
- Steppage gait
- Altered sensation 1st web space
Altered sensation 1st web space from deep fibular nerve injury affects
- Dorsolateral side of hallux
- Dorsomedial side of 2nd digit
Toe tips are innervated by
- Nerves from the plantar aspect of the foot
