Compartment syndrome, dislocations and pelvic injury

Acute Compartment Syndrome (ACS)

Acute compartment syndrome is a surgical emergency characterized by elevated tissue fluid pressure within an unyielding osteofascial compartment that compromises microvascular capillary perfusion, leading to irreversible muscle and nerve ischaemia.

Pathophysiology

Rising compartment pressure compromises microvascular perfusion and can cause irreversible muscle and nerve injury. The time course varies; do not wait for a six-hour deadline or a lost pulse before seeking fasciotomy assessment.

Common Aetiologies

• Fractures: Tibial shaft fractures (most common overall, $40\%$ of cases), forearm fractures (distal radius, both-bone radius/ulna), calcaneal fractures.
• Soft-tissue injuries: Severe crush injury, prolonged external compression (e.g., unconscious patient lying on hard floor following alcohol/drug intoxication).
• Iatrogenic causes: Excessively tight circumferential plaster casts, tight bandages, pneumatic anti-shock garments.
• Vascular reperfusion: Revascularization of an acutely ischaemic limb following prolonged arterial occlusion.

Clinical Presentation: The "6 Ps"

1. Pain Out of Proportion: Severe, relentless, crescendo pain that is totally disproportionate to the underlying injury and poorly responsive to escalating doses of intravenous opioids.
2. Pain on Passive Stretch: The earliest, most sensitive, and most reliable clinical physical sign. Passive stretching of the muscles traversing the affected compartment (e.g., passive extension of the toes for the deep posterior leg compartment, or passive ankle plantarflexion for the anterior compartment) elicits excruciating agony.
3. Paresthesia: Diminished sensation or burning dysesthesia along the sensory distribution of peripheral nerves traversing the compartment (e.g., numbness in the first dorsal web space from deep peroneal nerve compression in the anterior compartment). An early sign of nerve ischaemia.
4. Palpable Tenseness: The compartment feels palpably firm, wooden, and non-compressible.
5. Pallor: Late sign indicating microcirculatory shut-down.
6. Paralysis: A late ominous sign requiring immediate surgical assessment; it does not by itself establish irreversible necrosis.
7. Pulselessness: A very late finding. Peripheral arterial pulses (dorsalis pedis, posterior tibial) typically remain palpable because normal systolic arterial blood pressure ($100\text{ to }130\text{ mmHg}$) is far higher than intracompartmental pressure ($30\text{ to }60\text{ mmHg}$). The presence of palpable distal pulses never excludes acute compartment syndrome.

Compartment Pressure Monitoring

In obtunded, unconscious, or uncooperative patients, direct intracompartmental pressure measurement using a needle manometer (e.g., Stryker device) is required.

• Absolute Pressure: A compartment pressure $> 30\text{ mmHg}$ is indicative of ischaemia.
• Delta Pressure ($\Delta P$): The difference between diastolic blood pressure and measured intracompartmental pressure:

$$\Delta P = \text{Diastolic Blood Pressure} - \text{Compartment Pressure}$$

• Compartment pressure: A diastolic-pressure minus compartment-pressure difference of at most 30 mmHg is concerning in the appropriate setting. Serial clinical findings, measurement reliability and senior surgical judgement matter; one reading does not independently prove or exclude the diagnosis.

Emergency Management

1. Release All Constricting Materials Immediately: Completely bivalve and split all plaster casts, circumferential splints, dressings, and bandages down to the bare skin. Splitting a cast and underlying padding reduces intracompartmental pressure by up to 70%.
2. Limb Positioning: Maintain the limb strictly at heart level. Never elevate the limb above the heart, as elevation decreases local arterial perfusion pressure and worsens tissue ischaemia. Never place the limb in a dependent position, as this increases venous congestion.
3. Emergent Surgical Decompression: Perform emergency operative decompressive fasciotomy. In the lower leg, this requires a two-incision, four-compartment fasciotomy:
   • Anterolateral incision: Decompresses the anterior and lateral osteofascial compartments.
   • Posteromedial incision: Decompresses the superficial posterior and deep posterior osteofascial compartments.

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Joint Dislocations: Shoulder and Hip

Anterior Shoulder Dislocation

• Mechanism: The most common major joint dislocation ($> 95\%$ of shoulder dislocations). Results from a fall onto an abducted, externally rotated, and extended arm.
• Clinical Presentation: Severe shoulder pain, arm held in slight abduction and external rotation. Loss of the rounded lateral deltoid contour ("squared-off shoulder"), prominent acromion process, and palpable humeral head anteriorly.
• Neurovascular Assessment: Specifically examine the axillary nerve:
  • Sensory patch over the lateral deltoid muscle (the "regimental badge" area).
  • Motor innervation to the deltoid muscle (isometric contraction against resistance).
• Associated Pathologies:
  • Bankart lesion: Avulsion of the anteroinferior glenoid labrum from the glenoid rim.
  • Hill-Sachs lesion: Compression fracture of the posterolateral humeral head caused by impaction against the anterior glenoid rim during dislocation.
• Reduction Techniques: Cunningham method (gentle trapezius/biceps relaxation with steady downward traction), Milch technique, Kocher manoeuvre, or Stimson technique.
• Post-Reduction: Re-examine the axillary nerve, obtain confirmation post-reduction radiographs, and immobilize in a broad arm sling.

Posterior Hip Dislocation

• Mechanism: High-energy motor vehicle collision where the flexed knee impacts the dashboard ("dashboard injury"), transmitting an axial load along the femur while the hip is flexed, adducted, and internally rotated.
• Clinical Presentation: The affected lower limb is shortened, internally rotated, and adducted. The femoral head may be palpable in the gluteal region.
• Complications:
  • Sciatic Nerve Injury: The sciatic nerve (particularly the common peroneal division) is stretched or compressed by the displaced femoral head in up to $10\%\text{ to }20\%$ of cases. Manifests as foot drop (loss of active ankle and toe dorsiflexion) and numbness over the dorsum of the foot.
  • AVN: Injury to the predominantly medial circumflex femoral arterial supply threatens the head. Prompt reduction and follow-up are essential; avoid unsupported exponential-risk claims.
• Urgency: Reduce a dislocated hip as soon as safely possible, commonly aiming within six hours, using appropriate expertise and analgesia. Examine and document neurovascular status before and after, then assess associated fracture and joint congruity.
• Management: Emergent closed reduction under deep procedural sedation or general anaesthesia (e.g., Allis or Captain Morgan technique). Obtain post-reduction CT pelvis to evaluate for intra-articular osteochondral fragments and posterior acetabular rim fractures.

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Pelvic Fractures & Life-Threatening Haemorrhage

High-energy pelvic ring fractures carry an acute mortality of $15\%\text{ to }30\%$, primarily due to exsanguinating retroperitoneal haemorrhage.

Young-Burgess Classification

1. Lateral Compression (LC): Most common ($60\%$ to $70\%$). Caused by lateral side impact. The hemipelvis crushes inwards; usually mechanically stable with lower bleeding risk.
2. Anteroposterior Compression (APC / "Open-Book"): Direct frontal impact crushes the pelvis, causing diastasis of the pubic symphysis ($> 2.5\text{ cm}$) and disruption of the anterior sacroiliac ligaments. The pelvic volume expands markedly, tearing retroperitoneal vessels.
3. Vertical Shear (VS): Fall from height onto an extended lower extremity, causing cranial displacement of the entire hemipelvis with complete disruption of all pelvic ligaments. Highly unstable with massive haemorrhage.

Source of Haemorrhage

• Presacral Venous Plexus (85% to 90%): Extensive low-pressure bleeding from torn retroperitoneal venous plexuses and raw cancellous bone fracture surfaces.
• Internal Iliac Arterial Branches (10% to 15%): Superior gluteal artery, internal pudendal artery, and obturator artery.

Critical Clinical Examination Rule

Do not perform repeated manual pelvic rocking or compression. Manually compressing the iliac crests repeatedly to assess pelvic stability is strictly contraindicated: it dislodges newly formed, fragile haemostatic blood clots and precipitates catastrophic haemorrhage. A single gentle assessment or direct reliance on an AP pelvic radiograph is the standard of care.

Emergency Stabilization & Resuscitation

• Pelvic Binder Application: Immediately apply a commercial pelvic circumferential compression device (e.g., SAM Pelvic Sling) or tightly wrapped pelvic bedsheet centered directly over the greater trochanters (not over the iliac crests). This closes the open-book diastasis, reduces pelvic volume, promotes tamponade of venous bleeding, and mechanically stabilizes bone fragments.
• Haemodynamic Resuscitation: Activate the Massive Transfusion Protocol; administer intravenous tranexamic acid.
• Refractory Shock Management:
  • Transcatheter Angiographic Embolisation (TAE): For persistent arterial extravasation identified on CT angiography or ongoing bleeding in the interventional radiology suite.
  • Preperitoneal Pelvic Packing (PPP): Direct surgical retroperitoneal packing via an infra-umbilical midline laparotomy incision in the operating theatre to tamponade presacral venous bleeding, coupled with external skeletal fixation.

Primary references (checked 7 October 2026): NSW trauma pathway.