Thoracic Cage

Lower Limb Compartments

The muscles of the lower leg are surrounded by deep fascia and septa which divides them into compartments.

The anterior part of the leg (anterior and lateral compartments) contains:

  • Muscles that:
    • Dorsiflex the foot at the ankle
    • Adduct and invert the foot
  • Peroneal longus and brevis which abduct and evert the foot
  • Common peroneal nervewhich supplies the muscles
  • Popliteal arterybecoming the dorsalis pedis artery in the foot

The posterior compartment contains:

  • Muscles that:
    • Plantar flex the foot at the ankle
    • Adduct and invert the foot
  • Tibial nerve
  • Posterior tibial artery (eventually passing behind the medial malleolus)

Remember – one compartment may have increased internal pressure while another is normal.

lower-limb-compartment

Compartment Syndrome

Compartment syndrome occurs due to swelling within non-expansile fascial compartments. Swelling may be due to haematoma, muscle injury or fluid resuscitation. The increased pressure cuts off the blood supply and causes muscle death. Tissue pressures greater than 35 mmHg are dangerous and are common in:

  • High energy or crush injuries
  • Fractures of the tibia and fibula, particularly tibial plateau fractures
  • Tight dressings or plaster casts Burn injuries
  • Vascular damage

It can also occur, although less commonly, in prolonged unconsciousness, without trauma (for example, a midazolam overdose).

The symptoms all start with P – pain, paraesthesia, pallor, paralysis and pulse loss.

One of the first symptoms of compartment syndrome is increased pain, which is why orthopaedic surgeons wish to avoid lower limb nerve blocks. By the time the distal pulses have disappeared, much of the damage is already done. Finding one pulse does not exclude increased pressure in another compartment.

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