Compartment syndrome

Compartment syndrome is raised pressure within a closed osteofascial compartment that reduces perfusion to less than the level needed for tissue viability, leading to muscle and nerve necrosis. It is a limb threatening surgical emergency, and diagnosis rests on clinical suspicion in an at risk patient, with pressure measurement as an adjunct.

Clinical relevance. It complicates about 1 to 10% of tibial shaft fractures and a similar share of forearm and supracondylar fractures. Irreversible muscle damage begins after about 4 to 6 hours of ischaemia.

Delay causes contracture, loss of function, rhabdomyolysis, kidney failure and amputation.

Anatomy. The leg has four compartments (anterior, lateral, superficial posterior and deep posterior), the forearm has volar and dorsal (and mobile wad) compartments, and the thigh, gluteal region, hand, foot and abdomen can also develop compartment syndrome.

Mechanisms. Compartment volume rises (haemorrhage, oedema, extravasated fluid, reperfusion swelling) or compartment size falls (tight casts, dressings, burns eschar, closure of fascial defects). Rising pressure impairs venous outflow and then capillary and arterial perfusion.

Classification.

• Acute (hours): trauma and reperfusion.
• Exertional (chronic): recurrent exercise related pain that resolves with rest. Acute exertional compartment syndrome occurs with extreme exertion.
• Abdominal compartment syndrome: sustained intra-abdominal pressure over 20 mmHg with new organ dysfunction.
• By site: leg, forearm, hand, foot, thigh, buttock, upper arm, shoulder, abdomen.

Key distinctions. Pain out of proportion to the injury and pain with passive stretch are the earliest signs. Pulselessness, pallor and paralysis are late and indicate established ischaemia. Pulses are often present when compartment syndrome is diagnosed.

History.

• Mechanism: fracture (tibia, forearm, supracondylar, femur, pelvis), crush, burns, blunt trauma, snake bite, injection or extravasation (intravenous fluids, contrast, intraosseous infusion), arterial injury, reperfusion after ischaemia or revascularisation, prolonged immobilisation or positioning (lithotomy, lateral, drug overdose), vigorous exercise, tight cast or bandage.
• Increasing pain despite analgesia, swelling, tightness, paraesthesia and weakness.
• Anticoagulants, bleeding disorders, steroid use, nephrotic syndrome, hypothyroidism.
• In children: anxiety, agitation and increasing analgesic requirement (the "three As").

Examination.

• Inspect for swelling, tense shiny skin, bruising, blisters and wounds. Remove casts, splints and circumferential dressings and re-examine.
• Palpate each compartment for tension and tenderness (a wooden hard compartment).
• Passive stretch of the muscles in the compartment causes severe pain (flex fingers or toes in extension, extend them when the flexors are tense).
• Sensation: paraesthesia or reduced two point discrimination in the territory of nerves crossing the compartment (first web space of the foot for the deep peroneal nerve).
• Power, pulses and capillary refill (often normal), and Doppler signals. Examine other limbs and the abdomen.

Red flags.

• Severe pain out of proportion or uncontrolled by usual analgesia.
• Pain on passive stretch of the muscles in a compartment.
• Tense, swollen compartment with paraesthesia or weakness.
• Pulselessness, pallor or paralysis (late).
• Dark urine, rising creatine kinase, or hyperkalaemia (rhabdomyolysis).
• Unconscious, sedated or intubated patient with a swollen limb and risk factors (examination unreliable).
• Fracture with compartments that become tense after reduction or fixation.
• Circumferential full thickness burn.

Special groups. Children cannot always report pain. Patients with regional blocks or epidurals may have masked pain. Sedated and ventilated patients need pressure monitoring. Anticoagulated patients bleed into compartments.

Causes of compartment syndrome.

• Fractures (tibial shaft, forearm, supracondylar humerus, femoral, pelvic, calcaneus), crush, penetrating injury.
• Ischaemia reperfusion injury (arterial embolism, thrombosis, injury, tourniquet, vascular repair).
• Burns, frostbite, snake envenomation, extravasation, intraosseous infusion, pressure infusion.
• Haematoma (anticoagulants, bleeding disorders), infection (necrotising fasciitis, pyomyositis).
• Drug overdose with prolonged immobilisation, exertion, rhabdomyolysis.
• Iatrogenic: tight casts, lithotomy position, pneumatic compression, military antishock garments.

Conditions that mimic or accompany it.

• Vascular: acute limb ischaemia (arterial occlusion), deep vein thrombosis, phlegmasia cerulea dolens, pseudoaneurysm.
• Infective: cellulitis, necrotising soft tissue infection, pyomyositis, osteomyelitis, septic arthritis.
• Musculoskeletal: fracture pain, muscle rupture and haematoma, severe sprain, rhabdomyolysis, myositis.
• Neurological: nerve injury or entrapment, spinal cord injury, Guillain-Barre syndrome, peripheral neuropathy, complex regional pain syndrome.
• Other: chronic exertional compartment syndrome, medial tibial stress syndrome, stress fracture, popliteal artery entrapment.

Step 1. Diagnose on clinical grounds in an awake patient: severe pain, pain on passive stretch, and a tense compartment in a patient with an at risk injury. Do not wait for pulselessness.

Repeat examination every 1 to 2 hours in at risk patients for 24 to 48 hours (every hour after reduction or revascularisation).

Step 2. Pressure measurement for patients who are unconscious, sedated, uncooperative or young, or with equivocal findings, using a handheld monitor or an arterial line transducer with a side port needle placed in each compartment within 5 cm of the fracture.

• Delta pressure (diastolic blood pressure minus compartment pressure) under 30 mmHg supports the diagnosis and is preferred. A compartment pressure over 30 mmHg alone is a less reliable threshold, and 20 to 25 mmHg may be tolerated in hypertensive patients.
• Continuous monitoring may be used in high risk patients.

Step 3. Laboratory tests: creatine kinase (rises over 6 to 12 hours; over 5000 U/L carries a risk of kidney injury), potassium, urea, creatinine, calcium (low), phosphate, urate, lactate, blood gas, urinalysis for myoglobin (positive dipstick blood without red cells), full blood count and coagulation.

Step 4. Imaging does not diagnose compartment syndrome but excludes other problems: radiographs for fracture, duplex ultrasound for thrombosis, and CT angiography for arterial injury. Do not delay fasciotomy for imaging.

Limitations. Pain assessment is unreliable with sedation, nerve blocks, spinal injury, head injury and in children. Pulses and capillary refill may be normal until late. Pressure measurement varies with technique and site.

Immediate steps (while preparing for theatre).

• Remove all circumferential dressings, bandages and casts (bivalve and spread the cast, and cut padding to skin), loosen splints, and put the limb at heart level (do not elevate, which reduces arterial inflow).
• Give oxygen, treat hypotension (target a normal blood pressure to preserve perfusion), and give isotonic crystalloid.
• Analgesia: paracetamol 1 g IV every 6 hours (maximum 4 g daily; 3 g daily if weight under 50 kg, malnutrition, alcohol excess or liver disease) and morphine 2 mg IV boluses every 5 minutes titrated to effect (reduce the dose in older adults and kidney impairment; monitor sedation and respiratory rate). Avoid regional anaesthesia and epidural infusions until compartment syndrome is excluded, since they mask pain.
• Notify the senior surgeon and anaesthetist immediately and consent for fasciotomy.

Definitive treatment: emergency fasciotomy.

• Fasciotomy is indicated for clinical diagnosis, or for a delta pressure under 30 mmHg, and should be performed as soon as possible, ideally within 6 hours of onset. Late fasciotomy after 24 to 48 hours carries a high infection risk and is considered only when muscle is viable.
• Leg: two incision, four compartment fasciotomy (lateral incision for anterior and lateral compartments, medial incision for the superficial and deep posterior compartments), with skin incisions at least 15 to 20 cm long.
• Forearm: volar incision (with carpal tunnel release) and dorsal incision when needed. Hand: dorsal interosseous incisions. Thigh: lateral incision. Foot: dorsal or medial incisions. Gluteal and abdominal as needed.
• Leave wounds open, debride non-viable muscle, apply negative pressure dressings, stabilise fractures, and return for planned wound review at 24 to 72 hours. Close by delayed primary closure, or use skin grafting.
• Antibiotics and tetanus cover directed by the injury (cefazolin 2 g IV every 8 hours, maximum 6 g daily; for CrCl 10 to 34 mL/min give half the dose every 12 hours).

Rhabdomyolysis and reperfusion.

• Isotonic saline 1 to 1.5 L/hour for the first hours, then 200 to 300 mL/hour, to maintain urine output of 200 to 300 mL/hour (adjust with cardiac and kidney function), continued until creatine kinase is under 1000 U/L and myoglobinuria has cleared; monitor fluid balance, creatinine, potassium, calcium and acid base status every 4 to 6 hours.
• Hyperkalaemia (potassium 6.5 mmol/L or more, or ECG changes): calcium gluconate 10% 30 mL IV over 10 minutes (repeat after 5 to 10 minutes if ECG changes persist), insulin soluble 10 units IV with glucose 50% 50 mL (25 g) (monitor glucose hourly for 6 hours), and salbutamol 10 to 20 mg nebulised; consider renal replacement therapy for refractory hyperkalaemia, oliguric kidney injury, acidosis or volume overload.
• Do not give calcium for asymptomatic hypocalcaemia (rebound hypercalcaemia). Alkalinisation with bicarbonate has limited evidence.
• Avoid nephrotoxic drugs (NSAIDs, aminoglycosides, contrast when possible).

Exertional compartment syndrome. Acute exertional cases need emergency fasciotomy within 6 hours.

Chronic exertional cases are treated with activity modification and physiotherapy, and fasciotomy for persistent disease after confirmed pressure testing (pre-exercise over 15 mmHg, 1 minute post exercise over 30 mmHg, or 5 minutes over 20 mmHg).

Venous thromboembolism prophylaxis. Enoxaparin 40 mg subcutaneously once daily (20 mg daily if CrCl 15 to 30 mL/min; unfractionated heparin 5000 units subcutaneously every 8 to 12 hours if CrCl under 15 mL/min) once bleeding is controlled; monitor platelets from day 4 and creatinine.

Monitoring. After fasciotomy: hourly neurovascular observations for 24 hours, urine output hourly, creatine kinase and creatinine every 6 to 12 hours until falling, potassium every 4 to 6 hours initially, wound inspection at 24 to 72 hours, and temperature and CRP for infection. Monitor at risk patients every 1 to 2 hours clinically.

Referral and escalation. Orthopaedic, plastic or general surgeon on call immediately. Critical care for rhabdomyolysis with kidney injury, hyperkalaemia or multiple injury. Nephrology for renal replacement therapy. Plastic surgery for wound coverage. Rehabilitation and occupational therapy for nerve and muscle recovery.

Admission criteria. All patients with suspected or confirmed compartment syndrome, and at risk patients (high risk fractures, reperfusion injury, crush, burns) for observation of at least 24 to 48 hours. Discharge and safety netting. Discharge after wound healing or closure, normal kidney function, controlled pain, and a physiotherapy plan. Patients return for increasing pain, numbness, weakness, fever, wound discharge or dark urine.