Compartment syndrome is a condition that results from swelling of a muscle. The muscle is retained in its fixed volume fascia (its “compartment”), however, and thus the swelling of the muscle causes an increase in pressure within the fascia, and subsequent occlusion of the blood supply and normal functioning of the tissues in the compartment. This can result in infarction, and is usually excruciatingly painful. If left untreated, it can result in loss of limb, or less severely an ischaemic contraction known as Volkmann’s Ischaemic Contracture.
It typically occurs in the forearm and calf, but can also occur in the thigh and foot.
It is usually acute as the result of trauma, but occasionally occurs chronically in athletes.
It is often a clinical diagnosis, but it can be confirmed by the measurement of compartment pressures.
It requires an urgent fasciotomy to prevent irreversible ischaemia. Irreversible damage can occur within 4-8 hours of the onset of ischaemia.
Epidemiology and Aetiology
- Trauma – compartment syndrome is often a complication of fracture
- Most commonly seen in fractures of the distill radius or tibial diaphysis
- Fractures account for 75% of all cases of acute compartment syndrome
- About 10% of fractures of the tibia will result in compartment syndrome
- Fractures may be open or closed
- Continued pressure on a limb – e.g. crush injury, or lying for hours in the same position on the same limb – often seen in elderly patients after a fall, or in drug and alcohol abuse
- Occasionally can be iatrogenic – such as secondary to overly tight bandages, or prolonged use or tourniquets
- In cases without fracture, diagnosis if often delayed, with increased risk of muscle necrosis
- Rare causes include
- Athletes (chronic) – possibly due to recurrent episodes of rhabdomyolysis and / or the effect of dietary supplements
- More common in young men (aged under 35)
- Thought to be due to relatively larger muscle size of young men
- Compartment syndrome is the reason that we use a ‘back-slab’ as opposed to a ‘full cast’ in an acute fracture. The swelling seen with an acute fracture injury would quickly cause compartment syndrome if a full cast was applied.
- Swelling of the muscle – usually as a result of post-traumatic bleeding and oedema.
- Initially only venous flow is disturbed, and arterial flow (due to its greater pressure) still occurs.
- Eventually, the pressure within the compartment exceeds the arterial pressure, and the muscle begins to undergo ischaemia.
- The main arteries in the compartment have a higher pressure than the arterioles, and thus these may not be occluded until late on, if at all
- Other structures close by are also affected by the ischaemia – e.g. nerves, but the nerves are not affected until the pressure is very high
- This means that distal pulses and neurological exam are usually normal until VERY LATE ON!
- If there are reduced or absent pulses, then it is likely the diagnosis is too late to stop severe ischaemic damage.
Clinical features and diagnosis
- Often co-exists with fractures
- You should be suspicious if there is:
- Pain increasing over time – despite appropriate analgesia and joint immobilisation
- Pain is often disproportionate to the original injury
- Not relieved by immobilisation
- People particularly at risk are children/young adults with:
- Tibial shaft fractures
- Forearm injuries
- Crush injuries
- There is often increased pain on passive flexion and extension of the fingers and toes of the affected limb
- Measure compartment Pressure:
- Normal compartment press is 0-10mmHg
- Capillary blood flow may be reduced at around 20mmHg
- <30mmHg is unlikely to cause ischaemia or necrosis
- >40mmHg is high
- A more sophisticated method is to compare diastolic arterial and compartmental pressures – the difference needs to be >30mmHg for adequate perfusion. This is known as the Delta Pressure (as opposed to the absolute pressure). Any delta pressure <20mmHg is diagnostic for compartment syndrome
- In children – compartment pressures are not routinely monitored
- Measurement of pressure is not required for diagnosis
- Ischaemic injury occurs after 4 hours of ischaemia
- This becomes irreversible within the following 4 hours (i.e. by 8 hours since time of onset of ischaemia)
- Imaging – not indicated for the diagnosis of compartment syndrome – but obviously often useful for the diagnosis of any underlying fractures!
- Refer to surgery early if you have any suspicion
The “6P’s” of critical limb ischaemia
- Pain – often on passive stretching of the limb
- Perishingly cold
These are often late signs – denoting severe ischaemia. Pain is the key features (and often thinly feature early on) in making a prompt diagnosis
The compartment itself is often very swollen and tender
Complications of Compartment Syndrome
- Loss of limb
- Ischaemic contractures / loss of limb function
- Renal failure
- Fasciotomy – of the muscle compartments involved. Do it as soon as possible! To minimise the risk of irreversible ischaemia.
- Immediate actions
- Remova constrictive dressings
- Raise the limb above the level of the heart
- Call surgeon to arrange fasciotomy!
- Analgesia (e.g. morphine 2.5 – 5mg PRN)
- IV fluids
- Monitor urine output – aim to prevent rhabdomyolysis with fluid therapy
- Frequent re-examination for neuromuscular deficit
- If there is any doubt over the diagnosis, perform fasciotomy!