This is a syndrome that results from swelling of a muscle. The muscle is retained in its fixed volume fascia, however, and thus the swelling of the muscle causes occlusion of the blood supply. this can result in infarction, and can cause 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.
- Trauma – compartment syndrome is often a complication of fracture.
- Continued pressure on a limb – e.g. lying for hours in the same position on the same limb – often seen in drug and alcohol abuse.
- 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
- 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:
- <30mmHg is normal
- >40mmHg is high
- Compare diastolic arterial and compartmental pressures – the difference needs to be >30mmHg for adequate perfusion.
- In children – compartment pressures are not routinely monitored
- Fasciotomy – of the muscle compartments involved. Do it as soon as possible! To minimise the risk of irreversible ischaemia.
- If there is any doubt over the diagnosis, perform fasciotomy anyway!