Q8-1. Anterior Compartment

Question 1

anterior compartment:

borders

Answer 1

• anterior intermuscular septum,
• lateral surface of the tibia, and the
• interosseous membrane

Question 2

anterior compartment:

function and innervation

Answer 2

• dorsiflexors of the ankle and the digits
• innervated by deep fibular/ peroneal nerve

Question 3

tibialis anterior:

key features

Answer 3

• origin is most medial
• insertion is on plantar foot
• strongest ankle dorsiflexor
• invertor

Question 4

extensor digitorum longus:

key features

Answer 4

• origin is as proximal as TA & also arises from the lateral condyle fo the tibia
• no origin on the tibial shaft instead on the anterior/medial surface of fibular shaft
• weak evertor

Question 5

extensor hallucis longus:

key features

Answer 5

• origin is more inferior/distal to the previous 2 (keep this in mind for when you begin to look as axial sections of the leg)

Question 6

innervation of anterior muscular compartment of leg

Answer 6

deep fibular nerve (L4, L5)

Question 7

tibialis anterior:

attachments and actions

Answer 7

1. proximal: lateral condyle & superior half of lateral surface of tibia & interosseous membrane
2. distal: medial & inferior surfaces of medial cuneiform and base of 1st metatarsal
3. actions: dorsiflexes ankle & inverts foot

Question 8

extensor digitorum longus:

attachments and actions

Answer 8

1. proximal: lateral condyle of tibia & superior 3/4 of medial surface of fibula and interosseous membrane
2. distal: middle and distal phalanges of lateral four digits
3. main action: extends lateral 4 digits and dorsiflexes ankle

Question 9

extensor hallucis longus:

attachments and actions

Answer 9

1. proximal: middle part of anterior/medial surface of fibula and interosseous membrane
2. distal: dorsal aspect of base of distal phalanx of great toe (hallux)
3. main action: extends great toe and dorsiflexes

Question 10

fibularis tertius:

attachments and actions

Answer 10

1. proximal: inferior 1/3 of anterior/medial surface of fibula and interosseous membrane
2. distal: dorsum of base of 5th metatarsal
3. main action: dorsiflexes ankle and aids in eversion of foot & weak evertors

Question 11

which common origin do all anterior muscular compartment muscles attach?

Answer 11

interosseous membrane

Question 12

Which anterior compartment muscles are invertors? Which are weak evertors?

Answer 12

Invertors: tibialis anterior

Evertors: extensor digitorum longus, and fibularis tertius

Question 13

what is the extensor hallucis capsularis?

Answer 13

tendinous slip coming off either the EHL (extensor hallucis longus) or TA (tibialis anterior), and inserts into the MTPJ 1 capsule;

may attach to the synovial membrane, where it acts as a retractor or it may insert into the fibrous layer of the capsule

Question 14

peroneus tertius:

key features

Answer 14

1. origin is most inferior/distal and often fused/continuous w/ EDL
2. absent in 5-10% of subjects
3. weak evertor

Question 15

CC: If anterior compartment muscles are ONLY WEAK… when will major deficit occur?

Answer 15

at heel strike;

bc they can’t adequately control plantar flexion tendency of the ground reaction line and the forefoot will slap down hard

(results in foot slap)

Question 16

CC: If anterior compartment muscles are COMPLETELY PARALYZED… when will major deficit occur?

Answer 16

• foot will DROP into plantar flexion during swing and the “lengthened” limb will have to be compensated by increased hip and knee flexion
• (high steppage gait) to keep the foot from dragging –> there will also be a toe strike rather than heel strike

Question 17

muslces in

dorsal muscular compartment of foot?

Answer 17

1. EDB - extensor digitorum brevis
2. EHB - extensor hallucis brevis

Question 18

dorsal muscular compartment of foot:

innervation and main actions

Answer 18

• inn by lateral terminal branch of deep fibular nerve (L5, or S1, or both)
• action: dorsiflex the toes

Question 19

extensor DIGITORUM brevis:

prox and distal attachments

Answer 19

• prox:
  
  1. calcaneus (floor of tarsal sinus);
  2. interosseous talocalcaneal ligament
  3. stem of IER (inferior extensor retinaculum)
• distal:
  
  1. extensor expansion of 3 medial digits (toes 2-4)

Question 20

extensor hallucis brevis:

prox and distal attachments

Answer 20

• prox:
  
  1. common attachment w/ extensor digitorum brevis
• distal:
  
  1. dorsal aspect of base of proximal phalanx and great toe (digit 1)

Question 21

difference in action b/w the extensor digitorum brevis and extensor hallucis brevis muscles?

Answer 21

both extend/dorsiflex the toes

EDB extends the 4 medial toes at MTP and IP joints,

whereas EHB extends great toe at MTP joint

(*neither attach at 5th toe)

Question 22

which 2 structures run in superficial fascia of the ankle–> into dorsum of the foot?

Answer 22

1. medially - great saphenous vein & saphenous nerve

laterally - superficial fibular nerve & it’s terminal branches

Question 23

describe the skin on the dorsum of the foot

Answer 23

very thin!

therefore, had to be careful during exam

Question 24

in the dorsum of the foot, which nerve and vessels travel together that need to be separated?

Answer 24

1. deep fibular NERVE
2. anterior tibial vessels

Question 25

between which muscles does the DEEP FIBULAR NERVE and ANTERIOR TIBIAL VESSELS pass between?

Answer 25

the two structures pass between the: * **Superior leg**: TA (tibialis anterior) and EDL (extensor digitorum longus) * **Inferior leg:** TA (tibialis anterior) and the EHL (extensor hallucis longus)

Question 26

Although the pattern is variable, which are the superficial veins that can be found in the dorsum of the foot?

Answer 26

* great saphenous v * small saphenous v * lateral marginal v * medial marginal v * 1-4 dorsal MT v * lateral dorsal digital vein of 5th toe * medial dorsal digital vein of hallux * dorsal digital veins

Question 27

describe the general layout of the **arterial supply to the dorsum of the foot?** **(**it is variable; what is a key variation?)

Answer 27

\*in some cases, dorsalis pedis may be absent and instead is replaced by perforating fibular artery * dorsalis pedis * lateral tarsal artery * medial tarsal artery (often 2) * arcuate artery * deep plantar artery * first dorsal MT artery * proper dorsal digital branch to medial side of hallux * proper dorsal digital artery * anterior perforating artery * dorsal MT * posterior perforating artery * proper dorsal digital branch to lateral side of 5th toe

Question 28

CC: how to take dorsalis pedis pulse

Answer 28

* fingertips b/w EHL and EDL and toward the 1st intermetatarsal space * both pulses can be taken simultaneously * some patients may not have palpable dorsalis pedis pulse b/c a larger perforating fibular compensates

Question 29

describe termination of **superficial fibular nerve**

Answer 29

* travels w/in lateral compartment --\> * exits the deep fascia @ the inferior 1/3 of the leg and runs in the superficial fascia * 2 terminal branches

Question 30

which structures are deep to the course of the 2 terminal branches of **superficial fibular nerve**

Answer 30

* SFN starts at neck of the fibula, descending b/w fibularis muscles and the lateral side of the extensor digitorum longus * Gives rise to motor branches --\> supply the fibularis longus and brevis * Continues to descend w/ ONLY cutaneous function, providing sensory innervation to the anterolateral aspect of the lower leg. * In lower 1/3 of leg, SFN pierces the deep crural fascia and terminates by dividing into the medial and intermedial dorsal cutaneous nerves * These nerves enter the foot to innervate the majority of its dorsal surface.

Question 31

describe the **branching** of the Superficial Fibular nerve

Answer 31

1. Superficial fibular nerve 2. Intermediate dorsal cutaneous * Common dorsal digital branch * Proper dorsal digital branch 3. Medial dorsal cutaneous * Common dorsal digital branch * Proper dorsal digital branch * Proper dorsal digital branch to the medial side of the hallux

Question 32

describe termination of DEEP FIBULAR NERVE

Answer 32

1. after traveling w/in the anterior compartment and crossing the ankle, it divides into **lateral and medial terminal branches**

Question 33

which structures are superficial to DEEP FIBULAR NERVE? which structures are deep to DEEP FIBULAR NERVE?

Answer 33

* superficial: extensor retinaculum and extensor digitorum longus are superficial to the DEEP FIBULAR NERVE

Question 34

where does the **deep fibular nerve** contribute on the dermatome map?

Answer 34

very minimal contribution; proper dorsal digital nerve from medial terminal branch \*just supplies medial aspect of 2nd MT, and lateral of MT 1 (aka the flip flop space)

Question 35

describe course/ location of the lateral dorsal cutaneous nerve

Answer 35

branches from the sural nerve in posterior leg; travels under lateral malleolus, travels w/ sural

Question 36

name the following nerve branches in the dorsum of the foot

Answer 36