3A. 2: Muscle Compartments

Limb Compartments

* compartments define groups of muscles within the limbs
* separated by fibrous sheaths which are difficult to stretch
* muscles within a compartment typically act synergistically on a joint
* each compartment is supplied by its own neurovascular bundle

Upper limb compartments

Muscles on the front of the arm: flexion

Muscles on the back: extension

meaning:

* flexors → anterior
* extensors → posterior

flexors vs extensors

* flexors → anterior
* extensors → posterior

Innervation (posterior vs anterior)

UPPER ARM

Posterior (extensors)

* radial nerve

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Anterior (flexors)

* musculocutaneous nerve

Innervation (posterior vs anterior)

FOREARM

Posterior (extensors)

* radial nerve

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Anterior (flexors)

* Median nerve
* Ulnar nerve

Muscles within a compartment typically share:

* common innervation
* blood supply
* action

Innervation (posterior vs anterior)

THIGH + LEG

anterior (extensors)

posterior (flexors)

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\*notice the flip from the arm!!

Compartment syndrome

* fibrous sheaths surrounding compartments __**don’t stretch**__
* if damage + swelling occur, pressure can build up
* common sites: Shank & Forearm

Acute Compartment syndrome

At an acute level, this is a clinical emergency:

* major early sign is pain
* increasing with passive movement of joint distal to the affected area

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\*can occur with chronic overuse (not emergent, just requires time off)

Fasciotomy

the term for the surgery that is performed to release the pressure inside the compartments

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diagram:

* shows lateral and medial incision of the compartments
* cuts through the facia
* release pressure building up in these areas