Compartment Syndrome - MUHS PG Theory

Definition

• Campbell's Operative Orthopaedics, 15th Ed

Classification

Aetiology / Causes

Causes that INCREASE content (volume) in compartment:

• Fractures - most common (70%); tibial shaft fractures (1.5-11% risk)
• Soft-tissue contusions (23%)
• Vascular injury / arterial ischaemia with reperfusion (swelling post-revascularisation)
• Burns (circumferential third-degree)
• Crush injuries
• Spontaneous haematoma (bleeding disorders, anticoagulants)
• IV fluid / contrast extravasation under pressure
• Post-ischaemic reperfusion swelling
• Drug abuse / limb compression during altered consciousness
• Military antishock trousers (MAST)

Causes that DECREASE compartment volume:

• Tight casts and dressings
• Circumferential burns causing eschar

MUHS Exam Point: Fractures (70%) + soft tissue contusion (23%) = 93% of cases. Tibial shaft fractures carry highest risk.

Anatomy - Compartments of the Leg (Most Commonly Affected)

Four compartments of the leg (Campbell's Operative Orthopaedics, 15th Ed)

Compartments and Contents:

Key fact: Anterior and deep posterior compartments of the leg are MOST commonly involved (non-compliant walls). Anterior compartment of thigh is most vulnerable due to stiffest walls (fascia lata + IT band).

Pathophysiology

1. Increased interstitial pressure (from haematoma, oedema, external compression)
2. Reduced capillary perfusion pressure
3. Tissue ischaemia - oxygen deprivation to muscle and nerve
4. Cellular anoxia → irreversible muscle necrosis
5. If >30 mmHg sustained for >8 hours → significant muscle necrosis even with normal systemic blood flow
6. Nerve fibres (especially unmyelinated type-C sensory fibres) are most sensitive to hypoxia - explains early paraesthesia

Clinical Features - "6 Ps"

MUHS Exam Point: "Pulselessness is an extremely late sign. Pulses may be present even in established compartment syndrome." - Bailey & Love 28th Ed. Never rely on absence of pulse to rule out CS.

Diagnosis

Clinical Diagnosis (Primary)

• Pain out of proportion
• Pain on passive muscle stretch (most sensitive)
• Paraesthesia in nerve distribution
• Tense compartment

"The absence of clinical findings is more useful for excluding the diagnosis than the presence is for confirming it." - Campbell's

Compartment Pressure Monitoring (Adjunct)

• Altered level of consciousness (head injury, intubation, sedation)
• Unreliable clinical examination
• Epidural anaesthesia masking pain
• Peripheral nerve injury / tourniquet palsy
• Children (difficult physical assessment)

• Stryker handheld compartment pressure monitor (commercial)
• Whitesides three-way stopcock apparatus
• Wick/slit catheter monitor
• Arterial line manometer

Note: Pressure measurements are erroneous in 30-35% of patients. Never use pressure alone - combine with clinical assessment. CPK and myoglobinuria are LATE markers and should NOT be used to establish diagnosis.

Treatment

Emergency (Immediate) - "Decompression"

1. Remove all external constricting causes immediately - split casts, dressings down to skin level; remove circumferential bandages
2. Limb should be kept at heart level (not elevated - reduces perfusion pressure)
3. High-flow oxygen
4. IV access, fluids
5. Urgent senior surgical review

Definitive Treatment - Fasciotomy

• <6 hours: excellent results
• <12 hours: 68% good results

• 12 hours: only 8% good results → risk of permanent disability, Volkmann's contracture

Four-Compartment Fasciotomy of Leg (Double Incision - Mubarak & Hargens Technique)

• Releases anterior compartment (in line with anterior tibial muscle)
• Releases lateral compartment (in line with fibular shaft)
• Identify and protect superficial peroneal nerve posterior to the lateral intermuscular septum

• Saphenous vein and nerve retracted anteriorly
• Releases superficial posterior compartment (over gastro-soleus)
• Releases deep posterior compartment (over flexor digitorum longus)
• If soleus bridge extends >halfway down tibia, release the extended origin

• Leave wound OPEN - never attempt primary closure
• Vacuum-assisted closure (VAC) device applied
• Return to OT at 48-72 hours for debridement + viability check
• Intravenous fluorescein + Wood's light to assess muscle viability
• Closure options: primary closure, secondary intention, split-thickness skin grafting (needed in ~50%)
• Delayed primary closure with "shoelace" vessel loop technique

• Volar and dorsal forearm compartments released
• If swelling extends to hand: carpal tunnel release + hand fasciotomies

• Indicated after revascularisation of prolonged ischaemic limb (>6 hours ischaemia)
• "Liberal concomitant calf ± thigh fasciotomies following revascularisation of prolonged ischaemic limb is advisable" - Bailey & Love

Complications of Untreated / Delayed Compartment Syndrome

• Aggressive IV fluid resuscitation - target urine output >100 mL/hour until CPK <5000 U/L
• Urinary alkalinisation with bicarbonate
• Monitor electrolytes (K+ leak from necrotic cells)

Chronic Exertional Compartment Syndrome (CECS)

• Most common: anterior and deep posterior compartments of leg
• Athletes - long-distance runners, military recruits
• Forearm in weightlifters, rowers, welders
• Exercise increases muscle volume by ~20%
• 15-40% have associated fascial hernias
• Treatment: Fasciotomy (definitive)

Special Situations

Open Fractures

• Compartment syndrome CAN occur with open fractures - do NOT assume open wound decompresses the compartment
• High index of suspicion required

Children

• Physical findings more difficult to detect; diagnosis often delayed
• Altered pain expression

Incidence

• High and low-energy injuries have nearly equal incidence of compartment syndrome - do not underestimate low-energy injuries

Summary Box (MUHS Quick Points)

Percutaneous Endoscopic Gastrostomy (PEG) - MUHS PG Theory

Definition

Indications

Contraindications

Absolute

• No identifiable safe puncture site (e.g. interposing bowel on transillumination)
• Uncorrectable severe coagulopathy
• Haemodynamic instability / inability to safely perform endoscopy
• Life expectancy very short (procedure futile)
• Pharyngeal obstruction (tube cannot pass - use introducer/Russell technique)
• Peritonitis

Relative

• Prior abdominal surgery with adhesions
• Ascites
• Obesity (difficult transillumination)
• Hepatomegaly (liver between stomach and wall)
• Gastric varices
• Active gastric ulcer
• Sepsis

MUHS Exam Note: Oropharyngeal/oesophageal malignancy is NOT an absolute contraindication - but use Introducer (Russell) technique to avoid tumour seeding in the PEG tract. Pull/Push techniques carry risk of seeding oropharyngeal cancers into the tract.

Techniques

1. Pull Technique (Ponsky-Gauderer) - Most Common (~90%)

1. Patient supine/semi-Fowler; abdomen prepped and draped
2. Endoscope passed, stomach distended with air insufflation
3. Brief endoscopic survey of oesophagus, stomach, duodenum
4. Assistant fingers the abdomen - identify the point of maximum transillumination and indentation (ideally 2-3 cm below costal margin, left upper quadrant - or lower/more central for antral placement to ease PEG-J conversion)
5. Safe tract technique: 22-gauge spinal needle + saline syringe passed through abdominal wall. Bubbles should appear in syringe ONLY when needle enters gastric lumen (seen by endoscopist). If bubbles appear BEFORE - intervening hollow viscus present - choose new site
6. Skin incision (7-9 mm), 14G cannula advanced into gastric lumen, snare tightened around it, stylet removed
7. Blue looped guide wire passed through cannula into stomach, snared by endoscopist ("blue through" the silver loop of feeding tube)
8. Endoscope + snare withdrawn through oesophagus and out of mouth, bringing guidewire out of mouth
9. Wire looped to PEG tube; tube pulled down through oesophagus, stomach and out through abdominal wall
10. Endoscope reinserted to confirm internal bolster position against anterior gastric wall
11. External bolster placed loosely - allow one finger between bolster and skin

2. Push Technique (Sachs-Vine)

• Single-stranded guidewire passed through trocar, brought out of mouth
• Long plastic leader attached to PEG tube pushed over guidewire and out through abdominal wall
• Otherwise same steps as Pull technique

3. Introducer / Russell Technique (Percutaneous, no transoral passage)

• Uses Seldinger technique + peel-away sheath + fluoroscopy
• Tube placed percutaneously without passing through oropharynx
• Preferred for: oropharyngeal malignancy (avoids tumour seeding), obstructed oesophagus
• Endoscope used for mucosal counterpressure during insertion only
• Inflatable balloon tip instead of mushroom bumper

Pre-procedure Preparation

• Antibiotic prophylaxis: Single IV dose of 3rd-generation cephalosporin (e.g. cefazolin 1g) before procedure - mandatory
• Aspirin does NOT need to be stopped
• Warfarin: switch to LMWH 1 week before, hold dose on morning of procedure
• Clopidogrel: ideally switch to aspirin alone 5 days before; if not possible, proceed with caution (epinephrine in local anaesthetic, tighter external bolster)
• NPO (nil by mouth) for 4-6 hours before
• INR, platelets, coagulation screen

Post-procedure Care

• Feeding may begin 4 hours after placement
• Clean stoma with soap and water daily; split 4x4 gauze sponge placed OVER (not under) external bolster
• Antibacterial ointment NOT routinely recommended
• Tube irrigated with water before and after feeds/medications
• Rotate tube daily to prevent buried bumper syndrome
• External bolster should allow one finger beneath it at all times

PEG-J (Jejunal Extension through PEG)

• Indicated when patient cannot tolerate gastric feeding (gastroparesis, severe GORD, recurrent aspiration)
• Jejunal tube passed through PEG lumen under endoscopic guidance, advanced beyond ligament of Treitz
• 24 Fr PEG accommodates 12.5 Fr J-tube; 20 Fr PEG accommodates 8.5 Fr J-tube
• Note: aspiration pneumonia is usually from aspirated oropharyngeal secretions, NOT necessarily from gastric reflux

Complications

Early / Periprocedural

Late / Post-procedure

MUHS Exam Key Point: Buried bumper syndrome - caused by external bolster too tight → internal bolster grows into gastric wall. Prevented by leaving one finger's breadth between bolster and skin.

Advantages of PEG over Surgical Gastrostomy

Removal of PEG Tube

• Can be removed when no longer needed (after tract matures in ~4-6 weeks, tract closes spontaneously after removal)
• Methods:
  1. Traction removal (cut-and-push): For mushroom/bumper-type internal fixator - snip tube at skin level, push internal bumper into bowel to pass per rectum (suitable for mushroom bumpers <28 Fr)
  2. Endoscopic removal: Snare the internal bumper and withdraw through mouth - more controlled
  3. For buried bumper: endoscopic or surgical incision over bumper

Summary Table for Quick Revision