Acute compartment syndrome (ACS) of the forearm is a time-critical surgical emergency caused by elevated intracompartmental pressure leading to tissue ischemia. The forearm contains three compartments (volar, dorsal, and mobile wad), and the forearm is the most common upper-extremity site for ACS. [1-2] Irreversible muscle and nerve damage can occur within 6 hours of impaired perfusion. [1][3]
1. History
- Mechanism of injury: fractures (distal radius, both-bone forearm, supracondylar in children), crush injuries, high-energy trauma, penetrating injuries [1][4-5]
- Nontraumatic causes: narcotic overdose/"found down" positioning, IV infiltration/extravasation, bleeding diathesis, reperfusion injury after arterial repair [1-3]
- Pain characterization: initially controlled, then escalating and refractory to analgesics — this trajectory is the most important historical feature [1][3]
- Timing: onset typically within hours of inciting event; can evolve over 24–48 hours [3]
- Ask about anticoagulant use, recent casting/splinting, IV access in the affected arm, and substance use history (opioid overdose) [3][6]
2. Alarm Features
- Pain out of proportion to the injury, especially if escalating despite adequate analgesia [1][3]
- Pain with passive stretch of forearm muscles (passive finger extension for volar compartment) [3][7]
- Progressive paresthesias in the median or ulnar nerve distributions [1][3]
- Tense, woody-feeling forearm compartment on palpation [7]
- Motor weakness or paralysis — a late finding indicating likely irreversible damage [1]
- Pulselessness — a very late finding; pulses are typically preserved until pressures exceed systolic blood pressure; do NOT use presence of pulses to rule out ACS [1]
- In children: the 3 A's — anxiety, agitation, and increasing analgesic requirements [1]
3. Medications
- Contributors to ACS risk:
- Anticoagulants (warfarin, DOACs, heparin) — can cause spontaneous compartment hemorrhage [3][8-9]
- IV drug use / narcotic overdose — prolonged immobility with limb compression [1][6]
- Losartan and other drugs rarely associated with rhabdomyolysis-induced ACS [10]
- Regional anesthesia / epidural catheters — may mask pain and delay diagnosis; avoid in high-risk patients [1][11]
- Treatment medications:
- Opioid analgesics for pain control (titrate carefully — escalating requirements are a diagnostic clue)
- IV crystalloid for rhabdomyolysis prevention/treatment
- Mannitol and sodium bicarbonate may be considered for myoglobinuria
- Caution: Do not use NSAIDs as sole analgesic — may mask pain progression. Regional nerve blocks are controversial as they may delay diagnosis [1][12]
4. Diet
- Not directly applicable in the acute setting
- Aggressive IV hydration is critical if rhabdomyolysis is present or suspected (target urine output 200–300 mL/hr) [1][13]
- NPO status should be maintained in anticipation of emergent fasciotomy
5. Review of Systems
- Neurovascular: numbness, tingling, weakness in the hand/fingers
- Musculoskeletal: swelling, inability to move fingers, worsening pain
- Renal: dark/tea-colored urine (myoglobinuria suggesting rhabdomyolysis) [13]
- Cardiac: palpitations, chest pain (hyperkalaemia from muscle necrosis) [1]
- Constitutional: history of recent trauma, surgery, prolonged immobilization, substance use
6. Collateral History and Family History
- Collateral from EMS/bystanders: mechanism of injury, duration of limb compression, time "found down"
- Medication list — especially anticoagulants, antiplatelet agents
- Substance use history (opioids, alcohol) — "found down" patients are at high risk [3][6]
- Bleeding disorders or coagulopathies
- Family history is generally not contributory
7. Risk Factors
- Fractures: distal radius (especially with >35% translation or ipsilateral elbow injury), both-bone forearm fractures, supracondylar fractures in children [1][4-5]
- Crush injuries (OR ~11 for ACS in forearm fractures) [4]
- High-energy trauma, penetrating injuries [14]
- Vascular injury (brachial artery) with subsequent reperfusion [1]
- Tight casts, circumferential dressings, or splints
- IV infiltration/extravasation [1]
- Narcotic overdose / prolonged immobilization ("found down") [1][6]
- Anticoagulant therapy [3][8-9]
- Male sex (7.3 vs 0.7 per 100,000) [15]
- Young age [15-16]
- Burns [15]
8. Differential Diagnosis
- Acute arterial occlusion/ischemia — pulselessness more prominent; Doppler assessment differentiates [1]
- Deep vein thrombosis of the upper extremity — swelling and pain but typically less acute; ultrasound differentiates
- Cellulitis/necrotizing fasciitis — erythema, warmth, systemic toxicity; skin changes more prominent
- Fracture pain without ACS — pain should improve with immobilization and analgesia (unlike ACS)
- Rhabdomyolysis without ACS — elevated CK but no tense compartment
- Peripheral nerve injury — focal deficits without pain out of proportion or tense compartment
- Volkmann ischemic contracture — late sequela of missed ACS, not an acute diagnosis [1][17]
Pearl: The classic "5 P's" (pain, pallor, pulselessness, paresthesia, paralysis) are more indicative of arterial ischemia than compartment syndrome. For ACS, the emphasis should be on pain, pain with passive stretch, and paresthesias as early findings. [1]
9. Past Medical History
- Prior forearm fractures or surgeries
- Bleeding disorders, coagulopathies
- Chronic anticoagulation
- Peripheral vascular disease
- History of substance abuse (opioids, alcohol) [6][13]
- Diabetes, hypertension (may affect perfusion thresholds)
- Prior episodes of compartment syndrome
10. Physical Exam
- Vital signs: Assess blood pressure (needed for delta-P calculation); tachycardia may indicate pain or systemic complications
- Inspection: Forearm swelling, skin tension, ecchymosis; look for cast/dressing constriction
- Palpation: Tense, firm ("woody") compartment — though subjective assessment has low sensitivity/specificity even among experienced clinicians [1][3]
- Pain with passive stretch: Passively extend the fingers — severe volar compartment pain is highly suggestive [3][7]
- Neurologic exam:
- Median nerve: sensation to thumb, index, middle finger; thenar strength
- Ulnar nerve: sensation to small finger; interossei strength
- Radial nerve (posterior interosseous): wrist/finger extension
- Paresthesias are an early finding; motor deficits are late [1][3]
- Vascular exam: Radial and ulnar pulses — typically preserved until very late; their presence does NOT rule out ACS [1]
- Examine all compartments: volar, dorsal, and mobile wad
- Bilateral comparison when possible
11. Lab Studies
- Creatine kinase (CK): Elevated in rhabdomyolysis; CK >669 U/L identified as a predictive cutoff for ACS in forearm fractures; serial monitoring recommended [4][12]
- Basic metabolic panel: Potassium (hyperkalemia from muscle necrosis), creatinine/BUN (renal function), bicarbonate (metabolic acidosis) [1]
- Urinalysis: Myoglobinuria (dark urine, positive for blood on dipstick without RBCs on microscopy)
- CBC: Neutrophil count >7.01/L associated with ACS risk in forearm fractures [4]
- Coagulation studies: PT/INR, PTT — especially in anticoagulated patients
- Lactate: May be elevated with tissue ischemia
- Type and screen: In anticipation of surgical intervention
- Albumin: Low albumin identified as a risk factor for ACS [4]
12. Imaging
- X-rays of the forearm (AP and lateral): First-line to identify fractures, assess displacement, and evaluate for associated injuries [3]
- CT angiography: If vascular injury is suspected (brachial artery involvement)
- Ultrasound: May help identify hematoma or vascular injury; not diagnostic for ACS itself
- MRI: Not indicated acutely; may be used later to assess muscle viability in delayed/missed cases
- Imaging should never delay treatment — ACS is a clinical and pressure-based diagnosis [7]
13. Special Tests
- Intracompartmental pressure (ICP) measurement (Stryker device is most commonly used): [15]
- Indicated when clinical exam is equivocal or unobtainable (obtunded, sedated, pediatric, regional anesthesia) [3]
- Measure within 5 cm of the fracture site and in all compartments [1]
- Normal forearm compartment pressure: ~8 mmHg in adults [1]
- Delta pressure (ΔP) = Diastolic BP − ICP: Fasciotomy indicated when ΔP <30 mmHg [1][3]
- Absolute ICP >30 mmHg alone is less reliable and may lead to unnecessary fasciotomies [1][15]
- Continuous pressure monitoring is more accurate than single measurements when available [3][14]
The following figure illustrates the three main invasive pressure measurement techniques used in clinical practice:
- Near-infrared spectroscopy (NIRS)[18]
14. ECG
- Indicated if hyperkalemia is suspected (from rhabdomyolysis/muscle necrosis) [1]
- ECG findings of hyperkalemia: peaked T waves, widened QRS, sine wave pattern
- Baseline ECG recommended in patients with significant rhabdomyolysis or renal impairment
- Cardiac arrhythmias can occur from the release of hyperkalaemic, acidotic blood after reperfusion [1]
15. Assessment
ACS of the forearm is a clinical diagnosis supported by pressure measurements in equivocal cases. The forearm is the second most common site for ACS overall and the most common in the upper extremity. [2-3] In a systematic review, 35% of forearm ACS cases were linked to fractures, 10% to narcotic overdoses, and 8% to IV infiltrations. [1] Complications occur in approximately one-third of patients and are strongly associated with delays in fasciotomy beyond 6 hours. [16] Late sequelae of missed forearm ACS include Volkmann ischemic contracture — muscle fibrosis leading to decreased hand/wrist motion, diminished strength, and finger clawing. [1][17] Neurological deficit is the most common complication post-fasciotomy (21%). [5]
16. Treatment Plan
Immediate measures (ED)
- Remove all circumferential dressings, casts, and splints immediately [7][19]
- Position the limb at heart level (elevation above the heart may reduce perfusion pressure; dependency increases edema) [7]
- Provide adequate analgesia — but monitor pain trajectory closely as escalating requirements are diagnostic
- Aggressive IV fluid resuscitation if rhabdomyolysis is present or suspected [1][13]
- Correct hyperkalemia if present (calcium gluconate, insulin/dextrose, kayexalate)
Definitive treatment
- Emergent fasciotomy — the only definitive treatment [1][3][7]
- Perform using long, generous skin and fascial incisions releasing all compartments; leave incisions open [3]
- Volar approach (curvilinear incision) decompresses the volar compartment and may reduce dorsal pressures; if dorsal pressures remain elevated, a separate dorsal incision is required [20-21]
- Carpal tunnel release should be included if hand involvement is suspected [20]
- Optimal timing: within 8 hours of onset [1]
- Fasciotomy >8–24 hours after onset is controversial — muscle necrosis may have already occurred, and delayed fasciotomy may not improve outcomes and risks infection from necrotic tissue [1]
- Wound management: Fasciotomy wounds are left open; delayed primary closure or split-thickness skin grafting (needed in ~61% of cases) at 48–72 hours [5][16]
- Debridement of nonviable muscle at second-look surgery (typically 48 hours)
17. Disposition
- Admission criteria: All confirmed or strongly suspected ACS cases require emergent surgical consultation and admission [3][7]
- ICU admission if rhabdomyolysis with renal failure, hyperkalemia, metabolic acidosis, or hemodynamic instability [1][13]
- Observation: High-risk patients (forearm fractures, crush injuries, vascular injuries, "found down") require serial exams every 1–2 hours for 24–48 hours [3]
- Specialist consultation triggers:
- Orthopedic surgery / hand surgery — for fasciotomy
- Vascular surgery — if arterial injury suspected
- Nephrology — if acute kidney injury from rhabdomyolysis
- Never discharge a patient with a high-risk injury and inadequate observation period
18. Follow Up / Return Precautions
- Post-fasciotomy: return to OR at 48–72 hours for wound assessment, debridement, and closure/grafting [5][16]
- Long-term follow-up with hand surgery for functional assessment, contracture prevention, and rehabilitation
- Return precautions (for patients discharged with high-risk injuries under observation):
- Worsening pain despite medication
- Numbness or tingling in the hand/fingers
- Inability to move fingers
- Swelling or tightness of the forearm
- Dark-colored urine
- Expected recovery: With timely fasciotomy (<6 hours), outcomes are generally favorable; delays are associated with complications in ~33% of patients, including neurological deficits, contractures, infection, and need for amputation [1][16]
- Volkmann contracture may develop as a late sequela of missed or delayed ACS, requiring reconstructive surgery [1][17]
References
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