Forearm Compartment Syndrome
CIM Case: Forearm Compartment Syndrome
Clinical Scenario
Patient: 30-year-old male Presentation: Right forearm pain following motorcycle accident (90km/hr), brought to ED by ambulance, very distressed with severe pain despite analgesia Relevant history: High-speed motorcycle vs car collision, landed on outstretched hand, no loss of consciousness, no other injuries identified in primary survey, GCS 15 Examination findings:
- Right forearm markedly swollen and tense
- Tense, "wood-like" feel to volar and dorsal compartments
- Severe pain disproportionate to visible injury
- Pain dramatically increased with passive finger extension
- Radial and ulnar pulses palpable with good capillary refill
- Sensation intact but patient reports "pins and needles" in median nerve distribution
- Unable to actively extend fingers due to pain
- X-ray shows both-bone forearm fracture (radius and ulna mid-shaft)
- No open wounds
Investigations Provided
Laboratory Results
| Test | Result | Normal Range | Interpretation |
|---|---|---|---|
| Hb | 142 g/L | 130-180 g/L | Normal |
| WCC | 12.8 ×10⁹/L | 4-11 ×10⁹/L | Mildly elevated (stress response) |
| Platelets | 312 ×10⁹/L | 150-400 ×10⁹/L | Normal |
| Creatinine | 98 μmol/L | 60-110 μmol/L | Normal |
| CK | 2,450 U/L | 30-200 U/L | Elevated (muscle injury/ischemia) |
| Lactate | 2.8 mmol/L | 0.5-2.0 mmol/L | Elevated |
| Potassium | 4.8 mmol/L | 3.5-5.0 mmol/L | Normal |
| Coagulation | Normal | - | Safe for surgery |
| Group & Hold | Complete | - | For surgery |
Imaging
Image 1: AP and Lateral Right Forearm Radiographs
Radiological features:
- Both-bone forearm fracture (radius and ulna)
- Radius: Mid-shaft transverse fracture
- Ulna: Mid-shaft oblique fracture
- Minimal displacement
- Significant soft tissue swelling
- No associated elbow or wrist pathology
- No foreign bodies
Compartment Pressure Measurements (if obtained)
Pressure readings:
| Compartment | Pressure | Diastolic BP | Delta P |
|---|---|---|---|
| Volar superficial | 42 mmHg | 80 mmHg | 38 mmHg |
| Volar deep | 48 mmHg | 80 mmHg | 32 mmHg |
| Dorsal | 35 mmHg | 80 mmHg | 45 mmHg |
Delta P (Diastolic - Compartment Pressure) <30 mmHg = Indication for fasciotomy
Questions & Model Answers
What is compartment syndrome and what are the clinical features to recognise it?
What are the forearm compartments and what structures are at risk?
How do you measure compartment pressures and what are the indications for fasciotomy?
Describe your surgical technique for forearm fasciotomy.
The patient returns at 4 months with progressive forearm pain and stiffness. What is the diagnosis and management?
At 18 months post-operatively, the patient returns with new forearm pain after lifting a 5kg bag. What is the likely diagnosis and management?
Key Teaching Points
Pattern Recognition
This pattern suggests Forearm Compartment Syndrome:
- High-energy forearm injury
- Severe pain disproportionate to visible injury
- Pain with passive finger extension
- Tense, swollen forearm
- Paraesthesia (even with intact pulses)
Early Signs (Act on These):
| Sign | Why Important |
|---|---|
| Pain out of proportion | Most sensitive early sign |
| Pain with passive stretch | Earliest physical finding |
| Tense compartment | Direct evidence of increased pressure |
| Paraesthesia | Nerve ischemia |
Late Signs (Don't Wait for These):
| Sign | Significance |
|---|---|
| Paralysis | Irreversible muscle damage |
| Pulselessness | Very late, damage already done |
| Pallor | Severe ischemia |
Critical Management Points
- Clinical diagnosis - don't rely solely on pressure measurements
- Time is critical - irreversible damage after 4-8 hours
- Adequate fasciotomy - release ALL compartments
- Leave wounds open - plan for delayed closure
- Don't miss the diagnosis - "unnecessary" fasciotomy is better than Volkmann contracture
- Document carefully - time of diagnosis, time to theatre
Common Examiner Follow-ups
Q: "This patient is intubated and sedated after polytrauma. How do you diagnose compartment syndrome?"
In obtunded patients:
- Cannot rely on pain - cardinal sign unavailable
- Serial examination - tense compartments, swelling
- Low threshold for pressure measurement - Delta P <30 mmHg
- Prophylactic fasciotomy - in high-risk injuries (crush, vascular injury)
- Continuous monitoring - if borderline
Approach: Have a very low threshold for fasciotomy in unconscious patients with high-risk injuries. It's better to do a fasciotomy that wasn't needed than to miss compartment syndrome.
Q: "What is the pathophysiology of compartment syndrome?"
Pathophysiology:
| Stage | Events |
|---|---|
| Initiating event | Haemorrhage, oedema from injury |
| Pressure rise | Within fixed compartment |
| Venous outflow obstruction | Capillary pressure exceeded |
| Further oedema | Capillary leak |
| Arterial inflow affected | When pressure exceeds diastolic |
| Ischemia | Muscle and nerve |
| Necrosis | If not decompressed |
The key concept is that tissue perfusion depends on the difference between arterial pressure and compartment pressure, not arterial pressure alone. This is why Delta P (Diastolic - Compartment pressure) is the key measurement.
Q: "What are the causes of compartment syndrome?"
Causes:
| Category | Examples |
|---|---|
| Fractures | Tibia, forearm, supracondylar (paediatric) |
| Soft tissue injury | Crush, contusion, burns |
| Vascular | Arterial injury with ischemia-reperfusion |
| Iatrogenic | Tight casts, extravasation, positioning |
| External compression | Prolonged pressure (coma, intoxication) |
| Increased volume | Bleeding disorders, snake bite |
Most common in orthopaedics: Tibial shaft fractures and paediatric supracondylar fractures.
Related Topics
- Tibial Compartment Syndrome
- Supracondylar Fractures (Paediatric)
- Volkmann Ischemic Contracture
- Forearm Fractures
- Vascular Injury in Trauma
- Fasciotomy Techniques