Q8-2. Crural Fascia/Retinacula Flashcards
Define crural fascia.
Deep fascia completely surrounding the leg.
What is the crural fascia continuous with superiorly?
The fascia lata (of the thigh)
What is the popliteal fascia formed from?
The posterior blending of the crural fascia and the fascia lata with the thigh.
What is the crural fascia continuous with posteriorly?
The fascia over the foot.
What structures are formed by the crural fascia?
- Osteofascial compartments
- Retinacula
(Bonus: popliteal fossa is formed by the blending of the crural fascia and the fascia lata of the thigh.)
In addition to forming the osteofascial compartments and the retinacula, what other purpose can deep fascia serve?
Muscle attachment site
What are the three osteofascial compartments of the leg?
- Anterior
- Posterior (2 subcompartments in 1)
- Lateral
What three fibrous sheets divide the leg into the three osteofascial compartments?
- Anterior crural intermuscular septum
- Posterior crural intermuscular septum
- Interosseous membrane
What are the contents of the anterior compartment of the leg?
Muscles:
- Extensor digitorum longus
- Extensor hallucis longus
- Tibialis Anterior
- Peroneus Tertius
Neurovascular:
- Anterior tibial artery/veins
- Deep Fibular Nerve
What are the contents of the lateral compartment of the leg?
Muscles:
- Peroneus longus
- Peroneus brevis
Neurovascular:
- Superficial fibular nerve
* *no artery or vein runs w/in this compartment–> blood supply comes from the anterior tibial and fibular arteries
How is the posterior osteofascial compartment divided?
Two sub-compartments:
- Deep
- Superficial
The deep transverse intermuscular septum runs from the medial border and soleal line of the tibia–> medial crest of the fibula and the posterior crural intermuscular septum
**Add picture!!
What are the contents of the superficial posterior compartment of the leg?
Muscles:
- Gastrocnemius
- Plantaris
- Soleus
What are the contents of the deep posterior compartment of the leg?
Muscles:
- Flexor hallucis longus
- Flexor digitorum longus
- Tibialis posterior
- Popliteus
Neurovascular:
- Fibular Artery & Vein
- Posterior Tibial Artery
- Tibial Nerve
What is compartment syndrome?
Any condition causing swelling w/in a compartment, which increases intracompartmental pressure–> can in turn reduce blood supply to surrounding structure.
Keep in mind that because the crural fascia is dense and inelastic, it does not yield to swelling.
Which compartment is most susceptible to compartment syndrome?
Anterior compartment–> largely bounded by bone
What purpose do retinacula serve?
Bind tendons in place to prevent bowstringing and assuring the correct line of pull.
What are the main five retinacula in the foot/ankle region?
- Superior extensor
- Inferior extensor
- Flexor
- Superior peroneal
- Inferior peroneal
What differentiates retinacula from their surrounding deep fascia?
- Thickness
- Borders (more difficult to define for retinacula)
What is the course of the superior extensor retinaculum?
Binds anterior borders of tibia & fibula just above both malleoli.
What passes deep to the superior extensor retinaculum?
In order of medial to lateral:
- Tibialis Anterior
- Extensor Hallucis Longus
- Extensor Digitorum Longus
- Fibularis Tertius
What is the telltale characteristic of the Inferior Extensor Retinaculum?
Sideways “Y” shape
What are the three sections of the inferior extensor retinaculum? What do they connect to?
- Frondiform/Fundiform (stem)–> calcaneus, taulus; continuous w/ inferior peroneal retinaculum
- Superior arm–> medial malleolus
- Inferior arm–> blends w/ deep fascia of the sole near the navicular/medial cuneiform joint
What tendons travel deep to the inferior extensor retinaculum?
Ordered medial to lateral:
- Tibialis anterior
- Extensor hallucis longus
- Extensor digitorum longus
- Fibularis tertius
What nerve passes superficially to both the superior and inferior extensor retinacula?
superficial fibular nerve–> medial and intermediate dorsal cutaneous nerves
What neurovascular structures pass deep to both the superior and inferior extensor retinacula?
anterior tibial blood vessels and the deep fibular nerve
What two tendons run deep to both the superior peroneal and inferior peroneal retinacula?
- Fibularis brevis
2. Fibularis longus
What is the course of the inferior peroneal retinaculum?
Runs from the stem of the inferior extensor frundiform to the calcaneus
What is the course of the course of the superior peroneal retinaculum?
Runs from the lateral malleolus to the calcaneus
The flexor retinaculum serves as the superficial boundary to the beginning of what passageway between deep posterior compartments of the leg and plantar foot?
Tarsal Tunnel
AKA Calcaneal Canal & Porta Pedis
What is the course of the flexor retinaculum?
Runs from medial malleolus to the calcaneus
What is the mnemonic to remember the order of structures in the tarsal tunnel?
“Tom, Dick, And Very Nervous Harry “
What are the structures that travels through the tarsal tunnel?
Ordered anterior to posterior:
- Tibialis Posterior
- Flexor Digitorum
- Posterior Tibial Artery
- Posterior Tibial Vein
- Tibial Nerve
- Flexor Hallucis Longus
What is the purpose of tendon synovial sheaths?
Cover tendons to protect them from friction and chafing through their course beneath the retinacula.
How many synovial sheaths protect the tendons from each compartment of the leg?
Anterior= 3
Lateral= 1 then splits
Posterior (Deep)= 3
