Human Anatomy Week 7 - Outline Notes

Leg Osteology

• Tibia:
  • Medial and lateral condyles, intercondylar eminence, anterolateral tibial tubercle (Gerdy’s tubercle), tibial tuberosity, facet for fibula, shaft (anterior border and medial surfaces, interosseous border, soleal line), medial malleolus, fibular notch
• Fibula:
  • Head, neck, lateral malleolus, shaft
• Interosseous membrane: Syndesmosis between tibia and fibula (middle tibiofibular joint)
• Proximal and distal tibiofibular joints: Planar synovial joints

Leg Fascia

• Crural Fascia:
  • Continuous with fascia lata
  • Surrounds the leg except along medial tibia, attaching to anterior and posterior tibia margins
  • Intermuscular septa form anterior and lateral compartments
  • Retinacula (superior and inferior extensor retinaculum, flexor retinaculum, fibular retinaculum) prevent tendon bowstringing at the ankle
• Compartments of the leg:
  • Anterior compartment: bounded by tibia, interosseous membrane, and anterior intermuscular septum
  • Lateral compartment: bounded by anterior intermuscular septum, fibula, and posterior intermuscular septum
  • Deep posterior compartment: bounded by tibia, interosseous membrane and fibula anteriorly and the transverse septum posteriorly
  • Superficial posterior compartment: posterior to the transverse septum
  • Clinical Relevance: Compartment syndrome (medical emergency), chronic overuse injuries leading to inflammation and increased pressure

Superficial Posterior Compartment

• Overview: Powerful plantar flexors crucial for walking, running, jumping. Plantaris has little function and can be used for surgical repair.
• Muscles: gastrocnemius, soleus, plantaris
• Neurovascular: Shares posterior tibial artery and tibial nerve with the deep posterior compartment
• Clinical Considerations: Achilles tendonitis/rupture (improper training), deep vein thrombosis (DVT) and calf pump

Deep Posterior Compartment

• Overview: Long flexors of the foot and toes, controlling the foot during standing and gait.
• Muscles: Popliteus, flexor hallucis longus, flexor digitorum longus, tibialis posterior
• Neurovascular: Innervation (tibial nerve), vascular (posterior tibial artery)
• Clinical Considerations: Pure inversion (tibialis anterior and posterior working together)

Anterior Compartment

• Overview: Dorsiflexors (extensors) of the ankle.
• Muscles: Tibialis anterior, extensor digitorum longus, extensor hallucis longus, fibularis tertius
• Dorsal foot muscles (short toe extensors): extensor digitorum brevis, extensor hallucis brevis
• Neurovascular: Innervation (deep fibular nerve), vascular (anterior tibial artery becoming dorsalis pedis artery)
• Clinical Considerations: Anterior shin splints (inflammation), compartment syndrome, foot drop

Lateral Compartment

• Overview: Evert the ankle, counteracting inversion. Fibularis longus stabilizes arches of the foot
• Muscles: Fibularis longus, fibularis brevis
• Neurovascular: Innervation (superficial fibular nerve), vascular (fibular artery – NOT in lateral compartment but supplies it via perforating branches)
• Clinical Considerations: Superficial fibular nerve injury in lateral ankle sprain.

Neurovascular Overview

• Arterial supply: Popliteal artery divides into anterior and posterior tibial arteries, supplying the anterior compartment (with deep fibular nerve) and deep posterior compartment (with fibular artery) respectively.
• Superficial veins: Great saphenous (medial) and small saphenous (posterior)
• Innervation:
  • Tibial nerve in deep posterior compartment.
  • Deep fibular nerve in the anterior compartment.
  • Superficial fibular nerve in the lateral compartment.

Tibiofibular Joints

• Proximal tibiofibular joint:
  • Structure: gliding planar joint, ligaments (proximal anterior and posterior tibiofibular ligament).
  • Supports: Common peroneal nerve, biceps femoris and popliteus tendons, IT band, origins of PL, EDL, lateral gastrocnemius and soleus.
  • Motions: Fibula glides superiorly and posteriorly with dorsiflexion.
  • Neurovascular supports: Common peroneal nerve, lateral genicular, anterior tibial, and recurrent tibial arteries.
• Middle tibiofibular joint: Syndesmosis (interosseous membrane), motions are accessory with the ankle joint.
• Distal tibiofibular joint:
  • Structure: fibrous/syndesmosis, ligaments (interosseus, distal anterior and posterior tibiofibular ligament).
  • Supports: Transverse tibiofibular ligament (involved in “trimalleolar fx”).
  • Neurovascular supports: Deep peroneal, tibial, and saphenous nerves, perforating branches of peroneal, anterior and posterior tibial arteries.
  • Motions: Fibula glides superiorly and posteriorly with dorsiflexion.

Clinical Considerations

• Tibial fractures (heal slowly due to poor blood supply)
• Common fibular nerve injuries (causes foot drop)
• Deep venous thrombosis and varicose veins
• Compartment syndrome
• Shin splints: anterior and medial (anterior discussed above)
• Ankle reflex (S1 and S2)