Compartment Syndrome

Background

Definition: Compartment syndrome occurs when there is a raised intracompartmental pressure within a closed osteo-fascial space resulting in initial microvascular ischaemia.
You must define: Compartmental Pressure >40mmhg or DeltaP <30mmhg (Difference between the Diastolic BP and Compartmental pressure).
- Be aware that if the stem mentions that compartmental pressure is measured in theatre. The diastolic number has to be the Pre-Anaesthesia BP as often anaesthesia can lower BP.
Time sensitivity: Irreversible muscle and nerve damage develops within 4–6 hours if untreated.

Causes

Anyone can list a number of causes of compartment syndrome. The key point is to be aware when reading the scenario. For example: if your stem has a patient with the following, you should start mentally preparing for a compartment syndrome:

Fractures – tibial shaft, supracondylar humerus (children), forearm fractures.
Crush injuries.
Burns (circumferential eschar)
IV fluid extravasation.
Bleeding/anticoagulation-related haematoma (MMA Fighter developed a thigh haematoma post fight)

Clinical Presentation

Early and most reliable signs:

Pain out of proportion to the injury, not controlled with opioids.
Pain on passive stretch (PPS):
- Flexor compartment → pain on extension.
- Extensor compartment → pain on flexion.
Paresthesia (tingling, numbness).

Late signs:

Paralysis.
Absent/weak pulses (very late and often irreversible).

Investigations & Pressure Monitoring

Mainly a clinical diagnosis – do not delay for imaging.
Indications for intracompartmental pressure monitoring:
- Unconscious or intubated patients.
- Polytrauma or reduced GCS.
- Equivocal clinical findings.

Techniques:

Stryker needle or arterial line manometer.
Measure within 5 cm of fracture site.
Normal: 0–10 mmHg.
Thresholds:
- Absolute pressure ≥ 30 mmHg.
- Δp = (Diastolic BP – Compartment pressure) ≤ 30 mmHg.

Importance of blood pressure control:

Hypotension reduces diastolic pressure, narrowing the Δp and precipitating ischaemia.
Ensure aggressive resuscitation and normotension in polytrauma/intubated patients.

Definitive Management: Fasciotomy

Lower Leg Fasciotomy (Standard)

Double incision --> Four Compartment Decompression (recommended):

Lateral incision:
- Extends midway between tibia and fibula.
- Releases anterior and lateral compartments.
- Protect superficial peroneal nerve.
Medial incision:
- Along posteromedial tibia.
- Releases superficial and deep posterior compartments.
- Protect long saphenous vein and nerve.

Note the perforators are marked with a red marker.

Key principles:

All compartments must be fully released.
In your question, mention that this is the four compartment decompression. If the deep posterior compartment is not released then you cannot say you have done a four compartment fasciotomy.
Wounds must be left open at index surgery.
Apply non-adherent dressing + light bandages.
Plan for delayed primary closure or skin grafting at 48–72 hrs.

Other anatomical sites (less common in exams but need to know)

Forearm: Volar incision (Henry) ± dorsal incision. Carpal tunnel must also be released.
Thigh/arm/foot: Tailored incisions as per anatomical compartment involvement.

Key Exam Questions

Why is blood pressure control so important?
How to approach the intubated patient?
‘You’re called to the bedside to address a patient with pain, how do you approach?’
What is the surgical approach?
Describe the key anatomical land marks in a fasciotomy?
What anatomical structures are at risk?
Describe the importance of the perforator branches when completing your fasciotomy?

These questions are discussed in the Question Bank section of the website.

Scotland ST1 Orthopaedic National Selection Preparation