Forearm Compartment Syndrome

Forearm compartment syndrome is a surgical emergency characterized by elevated pressure within the closed fascial compartments of the forearm, leading to compromised tissue perfusion and progressive ischemic injury to muscles and nerves.

Key Concepts:

• Forearm contains 3-4 distinct osteofascial compartments with limited compliance
• Elevated compartment pressure reduces capillary perfusion (normal compartment pressure: 0-8 mmHg)
• Muscle necrosis begins at 30 minutes of complete ischemia; irreversible after 6-8 hours
• Volkmann's ischemic contracture is the devastating sequela of missed or delayed diagnosis
• High medicolegal risk - one of the most common causes of orthopaedic litigation

Definition: Compartment syndrome occurs when pressure within a closed osteofascial space rises sufficiently to compromise tissue perfusion, leading to:

• Muscle ischemia progressing to necrosis
• Nerve ischemia causing sensory then motor deficits
• If untreated: Volkmann's ischemic contracture

Forearm Compartments

The forearm contains three to four distinct compartments depending on classification. Understanding anatomy is critical for complete fasciotomy.

Pathophysiology

Ischemia-Reperfusion Cascade:

1. Increased compartment pressure (from bleeding, edema, external compression)
2. Venous outflow obstruction - first to be affected
3. Decreased arteriovenous gradient - reduced capillary perfusion
4. Tissue ischemia - muscle more sensitive than nerve initially
5. Cellular swelling - further increases pressure (positive feedback)
6. Muscle necrosis - begins within 30 minutes of complete ischemia
7. Nerve damage - reversible initially, irreversible after 6-8 hours
8. Volkmann's contracture - fibrotic replacement of necrotic muscle

Critical Time Windows

Common Causes

High-Risk Fracture Patterns

Patient Risk Factors

Clinical Features by Stage

Key Clinical Signs

Pain on Passive Stretch - THE most reliable early sign:

• Volar compartment: Pain with passive finger EXTENSION
• Dorsal compartment: Pain with passive finger FLEXION
• Pain is disproportionate to the injury itself
• Increasing analgesic requirements despite adequate initial dosing

Sensory Changes:

• First web space numbness (AIN - median nerve)
• Ulnar nerve distribution numbness (less common)
• PIN (posterior interosseous nerve) - motor only, no sensory

Motor Weakness:

• AIN palsy: Weak FPL (thumb IP), FDP to index finger
• Weak finger flexion (FDS, FDP)
• Weak wrist flexion

Compartment Pressure Measurement

Indications for Pressure Measurement:

• Equivocal clinical examination
• Obtunded/uncooperative patient
• Unreliable examination (intoxication, head injury)
• Serial monitoring when clinical suspicion moderate

Technique:

1. Use calibrated device (Stryker STIC, arterial line transducer)
2. Measure in zone of maximum injury/swelling
3. Measure all compartments if any suspicion
4. Position limb at level of heart
5. Infiltrate 0.3ml saline to confirm placement

Pressure Thresholds for Fasciotomy

Other Investigations

Laboratory:

• CK (creatine kinase) - elevated with muscle necrosis
• Myoglobin - rhabdomyolysis marker
• Serum lactate - tissue ischemia
• Renal function - monitor for myoglobinuric AKI
• Coagulation studies - if bleeding diathesis suspected

Imaging:

• X-rays - identify underlying fracture, guide fracture management
• CT/MRI - NOT routine, may delay treatment
• Doppler ultrasound - assess arterial flow (pulse presence ≠ adequate perfusion)

Continuous Monitoring

Indications for continuous compartment pressure monitoring:

• Multiple trauma patient requiring sedation/ventilation
• Post-operative monitoring after high-risk surgery
• Burns with circumferential involvement
• Serial measurements impractical

Preoperative Preparation

Patient Positioning:

• Supine position, arm on radiolucent hand table
• Tourniquet applied but use judiciously (inflate only if bleeding obscures view)
• Consider avoiding tourniquet to assess tissue perfusion

Consent Discussion:

• Explain wounds will be left open
• Risk of incomplete decompression
• Nerve and vessel injury risk
• Need for return to theatre at 48-72 hours
• Skin graft may be required
• Risk of ongoing muscle/nerve damage despite surgery

Volar Fasciotomy Technique

Complications of Delayed/Missed Diagnosis

Volkmann's Ischemic Contracture

Classification (Tsuge):

Complications of Fasciotomy

Immediate Post-operative Management

Wound Care:

• Leave wounds completely OPEN - NEVER close primarily
• Apply loose non-adherent dressing (Jelonet, Adaptic)
• Consider negative pressure wound therapy (VAC) if:
  • Significant edema persists
  • Large wound with exposed structures
  • Difficult to maintain dressing

Splinting:

• Position of function to prevent contracture:
  • Wrist: 20-30° extension
  • MCP joints: 70-90° flexion
  • IP joints: Full extension
  • Thumb: Abduction and opposition
• Avoid tight circumferential dressings
• Ensure splint does not compress compartments

Monitoring:

• Neurovascular observations every 2 hours for first 24 hours
• Monitor for:
  • Persistent pain (inadequate decompression)
  • Worsening motor/sensory deficit
  • Signs of bleeding
  • Systemic complications (rhabdomyolysis)

Laboratory Monitoring

Return to Theatre (48-72 Hours)

Assessment for Wound Closure:

Rehabilitation Protocol

Phase 1 (0-2 weeks):

• Wound healing priority
• Gentle passive ROM when wounds closed/stable
• Edema control - elevation, compression
• Hand therapy referral

Phase 2 (2-6 weeks):

• Active ROM exercises
• Scar massage and desensitization
• Gentle strengthening
• Functional activities

Phase 3 (6+ weeks):

• Progressive strengthening
• Return to activities of daily living
• Monitor for contracture development
• Long-term follow-up

Factors Affecting Outcome

Timing of Fasciotomy:

Other Prognostic Factors:

• Severity of initial injury
• Associated fractures and soft tissue trauma
• Patient age (younger = better recovery potential)
• Rehabilitation compliance
• Presence of complications (infection, rhabdomyolysis)

Expected Recovery Timeline

Volkmann's Contracture Outcomes

Prevention is Key:

• Incidence with early fasciotomy (less than 6h): less than 5%
• Incidence with delayed fasciotomy (greater than 12h): 20-40%
• Established contracture is IRREVERSIBLE - reconstructive surgery only

Reconstructive Surgery Outcomes:

Long-term Complications Rates

Medicolegal Outcomes

Key Documentation for Medicolegal Protection:

1. Time-stamped neurovascular examinations
2. Compartment pressure measurements (if performed)
3. Clinical decision-making rationale
4. Patient/family discussions about risks
5. Informed consent including Volkmann's contracture risk
6. Time from symptom onset to surgical decompression

Differential Diagnosis

Compartment syndrome must be distinguished from other causes of a painful, swollen or neurologically compromised forearm. The two most dangerous mimics to exclude are arterial injury and an evolving compartment syndrome masked by a nerve block.

Global Epidemiology

According to PubMed, the largest population series (McQueen et al, J Bone Joint Surg Br 2000, PMID 10755426) of 164 consecutive acute compartment syndromes found an associated fracture in 69%, with forearm cases linked to distal radius fractures and occurring predominantly in young men under 35 years. The Lancet Emergency Surgery Series review (von Keudell et al 2015, PMID 26460664) confirms acute compartment syndrome affects upper and lower limbs in both adults and children and that there remains no internationally agreed diagnostic gold standard. Forearm compartment syndrome in children is most often associated with displaced supracondylar humeral fractures (Mubarak & Carroll, PMID 479251).

Guideline & Registry Comparison

There is no orthopaedic registry that systematically captures forearm compartment syndrome in the way arthroplasty registries (AOANJRR, NJR, AJRR) capture joint replacement; incidence and outcome data derive from single-centre and national trauma series rather than registry datasets.

Practice Variation & Regional Considerations

The principal area of international practice variation is the diagnostic pathway: continuous intracompartmental pressure monitoring is favoured in some UK and European units for high-risk or obtunded patients, whereas a clinically-driven "decompress if suspected" approach predominates in many North American and Australasian centres (von Keudell 2015, PMID 26460664). The ΔP less than 30 mmHg threshold (McQueen, PMID 8898137) is the most widely adopted pressure criterion worldwide.

In Australia and New Zealand, trauma centres apply standardised serial neurovascular observation after high-risk fractures, and Therapeutic Guidelines (eTG) recommend cefazolin for surgical prophylaxis at fasciotomy. In rural and remote settings where retrieval (including by the Royal Flying Doctor Service) may exceed 4-6 hours, local surgeons should have a low threshold to perform fasciotomy before transfer rather than risk irreversible ischaemia in transit. VTE prophylaxis follows standard trauma protocols, with mechanical methods preferred initially given the bleeding risk into freshly decompressed compartments.