Acute compartment syndrome of the forearm
The case
A 25-year-old male motorcyclist sustained a closed fracture of both the radius and ulna of the right forearm 3 hours ago and was splinted in a volar backslab at the scene. He now has severe, escalating pain out of proportion to the injury, pain on passive extension of the fingers, tense swelling of the forearm, and reduced sensation in the distal median nerve distribution. Radial and ulnar pulses are palpable and capillary refill is 3 seconds. Analgesia has had minimal effect. What is the most appropriate immediate management?
Options
- AUrgent forearm fasciotomy in theatre
- BCT angiography before surgery
- CHigh-dose intravenous steroids and observe
- DRemove the backslab and observe for 4 hours
- EClosed reduction and cast, then reassess
Think it through before you read on. Which single option is best, and why are the other four wrong?
Show the answer and explanation
Answer
A. Urgent forearm fasciotomy in theatre
Why this is the right answer
This is acute compartment syndrome until proven otherwise. The diagnosis is clinical. The classic early signs are pain out of proportion to the injury, pain that increases with passive stretch of the muscles in the compartment (here, passive finger extension), a tense swollen compartment, and paraesthesia in the nerve that runs through it. Escalating opioid requirement is another warning sign.
Pulses and capillary refill are usually preserved. Compartment pressure only needs to exceed capillary perfusion pressure (about 30 mmHg) to cause muscle ischaemia, which is far below arterial pressure. Waiting for a pulseless limb means waiting until the muscle is already dead. 'Pulses present' is the trap in this question.
The only definitive treatment is fasciotomy: opening all compartments of the forearm to release the pressure. Irreversible muscle necrosis begins after about 4 to 6 hours of ischaemia and leads to Volkmann ischaemic contracture, permanent nerve damage and, with large muscle loss, rhabdomyolysis and acute kidney injury. Therapeutic Guidelines and the British Orthopaedic Association standards both state that the diagnosis should lead directly to surgical decompression without delay.
While theatre is arranged, all circumferential dressings and the backslab are removed and split, and the limb is kept at heart level. Elevation above the heart reduces arterial inflow and worsens ischaemia.
Compartment pressure measurement is used only when the clinical picture is unclear, for example in an unconscious patient. A difference between diastolic pressure and compartment pressure of less than 30 mmHg supports the diagnosis.
Why the other options are wrong
- B
Intact pulses make arterial injury unlikely; imaging would delay decompression and cost muscle.
- C
Steroids do not lower compartment pressure; the nerve signs are from ischaemia, not primary nerve injury.
- D
Removing constricting dressings is a first measure, but observing for hours with established signs risks permanent damage.
- E
Reduction and casting do nothing for compartment pressure and would compound the delay.
High-yield takeaway
Pain out of proportion plus pain on passive stretch after a fracture is compartment syndrome; pulses are usually present, and the treatment is immediate fasciotomy.
Reference: Therapeutic Guidelines / British Orthopaedic Association Standard for Trauma (BOAST): Diagnosis and Management of Compartment Syndrome of the Limbs (2016)
Common questions
Can compartment syndrome occur with normal pulses?
Yes, and it usually does. Muscle ischaemia starts at pressures well below arterial pressure. Pulselessness is a very late sign.
Should the limb be elevated?
No. Keep it at heart level. Elevation reduces arterial inflow and worsens the ischaemia.
Related free cases
No account. No card.
Try twenty of these, unmarked.
A worked case shows the reasoning. A session shows you where you stand.
No account. No card.