Compartment Syndrome

Overview

Definition

Compartment syndrome is a condition that occurs when increased pressure in a closed muscle compartment exceeds the pressure to perfuse the compartment, resulting in muscle and nerve ischemia.

Epidemiology

• Because men generally have larger muscle mass, they (especially men < 35 years of age), have the highest incidence.
• Muscle mass in the compartment increases around 20 years of age but subsequently diminishes after 35 years of age.
• Long bone fractures: approximately ¾ of cases
  • ↑ risk of acute compartment syndrome (ACS) in comminuted fractures
  • Bones most affected:
    • Tibia (most common)
    • Humerus near the elbow (supracondylar fractures in children)

Etiology

• Traumatic:
  • Long bone fractures (most common)
  • Crush injury
  • Burns
  • Electrical shocks
  • Penetration injury
  • Animal bites
• Non-traumatic:
  • Bleeding, coagulopathy
  • Ischemia reperfusion syndrome
  • Extravasation injury
  • Cast that is too tight
  • Intense muscle activity
  • High-pressure injection
  • Toxins such as snake venom
  • Group A streptococcus infections of the muscle

Pathophysiology

• Muscle groups are divided into compartments, which are reinforced by fascial membranes.
• ↑ compartment pressure → venous outflow obstruction (↑ venous pressure) → arteriolar collapse (↓ arterial pressure) → decreased tissue perfusion → cellular anoxia →  damage to nerve and muscle tissues
• Factors affecting injury:
  • Pressure:
    • Normal pressure within a compartment: generally 0–8 mm Hg
    • Pressures tolerated without damage: up to 20 mm Hg 
  • Duration: 
    • Prolonged exposure at elevated pressures results in cell death. 
    • Reversible muscle injury: < 4 hours
    • Irreversible muscle injury: ≥ 8 hours
    • Nerve conduction loss: 2 hours
    • Neuropraxia: 4 hours
    • Irreversible nerve injury: ≥ 8 hours
  • Type and location of injury
• Can affect any compartment of the body:
  • Lower extremities (leg): most common location of ACS
  • Forearm: compartment syndrome associated with supracondylar fracture (children) and distal radius fracture (adults)
  • Upper arm
  • Hand
  • Abdomen
  • Buttock

Clinical Presentation

General signs and symptoms

• Pain out of proportion to exam and injury
• Progressive pain on passive stretch of affected compartment
• Paresthesia (sensory loss occurs before motor loss)
• Pallor
• Paralysis
• Pulselessness (patient may have normal pulsation) 
• Cool extremity
• Rapidly increasing and tense swelling

Mnemonic

The 6 Ps of compartment syndrome:

1. Pain
2. Poikilothermia
3. Pallor
4. Paresthesia
5. Pulselessness
6. Paralysis

Leg compartment syndromes

• Anterior compartment (most common site):
  • Structures:
    • Muscles responsible for dorsiflexion, eversion, and inversion of the foot and ankle
    • Toe extensors
    • Anterior tibial artery
    • Deep peroneal nerve
  • Associated clinical feature(s):
    • Tense anterior leg
    • Deep peroneal nerve palsy
    • Sensory loss in the 1st and 2nd web spaces
    • Weak toe extensors and foot dorsiflexion
    • Painful passive motion with toe flexion
• Lateral compartment:
  • Structures:
    • Muscles responsible for foot eversion
    • Superficial peroneal nerve
    • Portion of the deep peroneal nerve
  • Associated clinical feature(s):
    • Weak dorsiflexion and inversion of the foot (deep peroneal nerve deficit)
    • Reduced sensation in the lower leg 
• Deep posterior compartment:
  • Structures:
    • Muscles responsible for foot plantar flexion
    • Posterior tibial artery, peroneal artery
    • Tibial nerve
  • Associated clinical feature(s):
    • Posterior tibial nerve palsy
    • Weak toe flexors 
    • Pain with toe extension
    • Tense distal medial leg
• Superficial posterior compartment (least at risk):
  • Structures:
    • Muscles of plantar flexion (gastrocnemius, soleus)
    • No major arteries or nerve
  • Associated clinical feature(s):
    • Tense leg area
    • Pain in the leg

Forearm compartment syndromes

• Anterior compartment (superficial and deep groups):
  • Structures muscles responsible for wrist and digit flexion and pronation
  • Associated clinical feature(s):
    • Ulnar and median nerve palsy
    • Weak digital flexors
    • Painful digital extension
    • Tense volar forearm
• Posterior compartment of the forearm:
  • Structures: muscles responsible for wrist and digit extension and forearm supination 
  • Associated clinical feature(s):
    • Weak digital extensors
    • Painful digital flexion
    • Tense dorsal forearm

Other compartment syndromes

• Arm compartment syndrome: 
  • Rare, as the arm compartments tolerate significant fluid volume
  • If the anterior compartment is affected, clinical features are:
    • Ulnar and median nerve palsy
    • Weak biceps and distal flexors
    • Painful elbow flexion
    • Tense anterior upper arm
  • If the posterior compartment is affected, clinical features are:
    • Radial nerve palsy
    • Weak triceps and forearm extensors
    • Painful elbow extension
    • Tense posterior upper arm
• Thigh compartment syndrome (may occur with major trauma) and hand compartment syndrome are uncommon.

Diagnosis

• Primarily a clinical diagnosis 
• Compartment pressure measurement:
  • Manometer (hand-held equipment)
  • Wick or slit-catheter technique (catheter is inserted into the compartment and a transducer monitors the pressure)
• Normal pressure of a tissue compartment is 0–8 mm Hg.
• Compartment syndrome:
  • Pressure > 30–40 mm Hg 
  • Differential pressure < 30 mm Hg (the pressure difference between diastolic blood pressure and compartment pressure)

Management

• Initial ABCDE (Airway, Breathing, Circulation, Disability, Exposure) assessment for all trauma patients
• Remove any binders, casts, or dressings of the affected site.
• Compartment pressure within 30 mm Hg of diastolic pressure should undergo emergent fasciotomy:
  • Long incisions release the pressure in the affected compartment and adjacent compartments. 
  • These wounds are left open, and a 2nd-look procedure for debridement is performed within 48–72 hours. 
  • Wound closure within 7–10 days (may require skin grafting)
• Analgesics
• For non-traumatic causes:
  • Hemophiliacs: replacement of factor levels
  • Patients on anticoagulants: reversal of anticoagulation or factor replacement

Clinical Relevance

• ABCDE assessment: the mainstay management approach used in managing critically ill patients and the essential 1st step to perform in many situations, including unresponsive patients, cardiac arrests, and critical medical or trauma patients. For the trauma patient, ABCDE assessment is included in the primary survey, the initial evaluation, and for the management of injuries. 
• Rhabdomyolysis: a condition characterized by muscle necrosis and the release of myoglobin, which has nephrotoxic effects. Rhabdomyolysis can be caused by trauma or direct muscle compression, or can be nontraumatic (e.g., intense exertional activity). Creatine kinase elevation with presentation of myalgias and dark urine highly suggest the diagnosis. Management is with intravenous fluid resuscitation. 
• Crush syndrome: systemic manifestations (renal failure, shock) resulting from a compressive traumatic injury. Compartment syndrome and/or rhabdomyolysis can occur in crush syndrome. Field management with intravenous fluids and extrication is crucial in reducing the risk of complications and death. 
• Supracondylar fracture: the most common elbow fracture affecting the distal humerus just above the condyles. This injury needs an immediate orthopedic consultation to evaluate possible neurovascular bundle damage, as many vessels and nerves pass by the elbow. This fracture may also be complicated with compartment syndrome.