– extensor digitorum brevis is innervated by the deep peroneal nerve
– a complete peroneal nerve injury at the fibular head would leave sensation only along the plantar aspect of the foot (tibial nerve) and along the medial aspect of the foot (saphenous nerve – continuation of femoral nerve)
Note that in cross section:
– In the anterior compartment the EHL is most posterior and lays along the IO membrane; tib ant lies medially against the tibia, and EDL lays more laterally.
– In the lateral compartment, peroneus brevis is deep to longus.
– In the deep posterior compartment, tib post lays along the IO membrane, FDL lays posteromedially, and FHL lays most laterally (interesting that it lays so laterally when it has to get over so medially – just remember that FHL has to lay laterally because the Harmon approach goes between peroneus brevis and FHL). The plantaris tendon lies posteromedially between soleus and gastrocs.
– tib post inserts into the tarsal navicular
– the spring ligament runs between the calcaneus and navicular and “props up” the talar head. It officially is called the plantar calcaneonavicular ligament – and because it has some elasticity, and because it receives the head of the talus, it is called the spring ligament.
– the structure most at risk with the anteromedial portal is the great saphenous nerve and saphenous vein. For the anterolateral portal, watch out for the superficial peroneal nerve. The tibialis anterior nerve and artery run medial to EHL up high, but at the ankle they lay just lateral to EHL, between EHL and EDC. (Note that EHL and TA are medial). To get an anterocentral portal, go through the EDC tendons – that way you know the artery is medial.
– the medial and lateral planter nerves pass deep to the abductor hallucis and flexor digitorum brevis
Important reminder about the layers in the foot
Superficial – plantar aponeurosis with lateral cord (what rips off the base of 5th metatarsal)
Layer 1: Abductor hallucis
Flexor digitorum brevis (big thick muscle, just under plantar aponeurosis)
Abductor digiti minimi
Layer 2: Quadratus plantae
Flexor digitorum longus tendons
Flexor hallucis longus tendon
Lumbricals (with flexor digitorum longus)
Layer 3: Adductor hallucis – oblique and transverse bands
Flexor hallucis brevis (with two heads going into the sesamoids)
Flexor digiti minimi brevis
Layer 4: Interossei – 4 dorsal, 3 plantar
Long plantar ligament
Note that the medial and lateral plantar nerves are protected from puncture by the thick plantar aponeurosis and the thick first layer (consisting of FDB, AbdH, AbdDM)
Compartments of the Foot – for Compartment Syndrome
Medial: Abductor hallucis
Flexor hallucis brevis
Lateral: Abductor digiti minimi
Flexor digiti minimi
Superficial: Flexor digitorum brevis
Distal tendons of flexor digitorum longus
Adductor: Adductor hallucis
Four interosseous compartments
Calcaneal: Quadratus plantae – this is what Manoli has described.
There are 9 compartments in total (if you count Manoli’s calcaneal compartment). The superficial, lateral, and medial compartments run the length of the foot. The adductor and 4 interossei compartments are confined to the forefoot. The calcaneal compartment is a separate hindfoot/midfoot compartment consisting of the quadratus plantae.
Manoli feels that the clawing from compartment syndrome is due to the contracture of quadratus – pulls on the flexor digitorum longus tendons.
The described technique of decompressing the compartments is two dorsal longitudinal incisions to decompress the interosseous compartments, then a medial curved incision to decompress the medial, superficial, lateral, adductor, and calcaneal. Beware the lateral and medial plantar nerves that run deep to the flexor digitorum brevis, between the 1st and 2nd muscular layers of the foot. (1st layer: flexor digitorum brevis, abductor hallucis, abductor digiti