# CIM Case: Forearm Compartment Syndrome ## Clinical Scenario **Patient:** 30-year-old male **Presentation:** Right forearm pain following motorcycle accident (90km/hr), brought to ED by ambulance, very distressed with severe pain despite analgesia **Relevant history:** High-speed motorcycle vs car collision, landed on outstretched hand, no loss of consciousness, no other injuries identified in primary survey, GCS 15 **Examination findings:** - Right forearm markedly swollen and tense - Tense, "wood-like" feel to volar and dorsal compartments - Severe pain disproportionate to visible injury - Pain dramatically increased with passive finger extension - Radial and ulnar pulses palpable with good capillary refill - Sensation intact but patient reports "pins and needles" in median nerve distribution - Unable to actively extend fingers due to pain - X-ray shows both-bone forearm fracture (radius and ulna mid-shaft) - No open wounds --- ## Investigations Provided ### Laboratory Results | Test | Result | Normal Range | Interpretation | |------|--------|--------------|----------------| | Hb | 142 g/L | 130-180 g/L | Normal | | WCC | 12.8 ×10⁹/L | 4-11 ×10⁹/L | Mildly elevated (stress response) | | Platelets | 312 ×10⁹/L | 150-400 ×10⁹/L | Normal | | Creatinine | 98 μmol/L | 60-110 μmol/L | Normal | | CK | 2,450 U/L | 30-200 U/L | Elevated (muscle injury/ischemia) | | Lactate | 2.8 mmol/L | 0.5-2.0 mmol/L | Elevated | | Potassium | 4.8 mmol/L | 3.5-5.0 mmol/L | Normal | | Coagulation | Normal | - | Safe for surgery | | Group & Hold | Complete | - | For surgery | ### Imaging **Image 1: AP and Lateral Right Forearm Radiographs** **Radiological features:** - Both-bone forearm fracture (radius and ulna) - Radius: Mid-shaft transverse fracture - Ulna: Mid-shaft oblique fracture - Minimal displacement - Significant soft tissue swelling - No associated elbow or wrist pathology - No foreign bodies ### Compartment Pressure Measurements (if obtained) **Pressure readings:** | Compartment | Pressure | Diastolic BP | Delta P | |-------------|----------|--------------|---------| | Volar superficial | 42 mmHg | 80 mmHg | 38 mmHg | | Volar deep | 48 mmHg | 80 mmHg | 32 mmHg | | Dorsal | 35 mmHg | 80 mmHg | 45 mmHg | **Delta P (Diastolic - Compartment Pressure) <30 mmHg = Indication for fasciotomy** ## Questions & Model Answers **Definition:** Compartment syndrome is a limb-threatening condition where increased pressure within a closed osteo-fascial compartment compromises tissue perfusion, leading to ischemia and potential irreversible muscle and nerve damage. **The 6 Ps (in order of appearance):** | Sign | Description | Timing | |------|-------------|--------| | **Pain** | Disproportionate to injury, increased with passive stretch | EARLY | | **Pressure** | Tense, "wood-like" compartment | EARLY | | **Paraesthesia** | Altered sensation in nerve distribution | EARLY | | **Paresis** | Weakness, difficulty with active movement | LATE | | **Pulselessness** | Loss of distal pulses | VERY LATE | | **Pallor** | Pale, cold limb | VERY LATE | **IMPORTANT:** Pulses are often PRESENT until very late. Waiting for pulselessness means irreversible damage has occurred. **Clinical Examination:** | Test | Technique | Significance | |------|-----------|--------------| | **Pain with passive stretch** | Passively extend fingers | Most sensitive early sign | | **Two-point discrimination** | Test fingertip sensation | Nerve function | | **Compartment palpation** | Compare to uninjured side | Tense, firm feel | | **Active movement** | Ask patient to make fist | Pain and weakness | **This Patient Has:** - Severe pain disproportionate to injury ✓ - Pain with passive finger extension ✓ - Tense compartments ✓ - Paraesthesia (pins and needles) ✓ - Pulses present (does NOT exclude compartment syndrome) **Diagnosis: COMPARTMENT SYNDROME** - surgical emergency > **Consultant Tip:** Compartment syndrome is a CLINICAL diagnosis. Don't wait for absent pulses - that's a very late sign. Pain out of proportion + pain with passive stretch = fasciotomy. **Forearm Compartments:** **1. Volar (Anterior) Compartment:** | Layer | Muscles | |-------|---------| | **Superficial** | Pronator teres, FCR, Palmaris longus, FCU, FDS | | **Intermediate** | FDS (separate layer in some classifications) | | **Deep** | FDP, FPL, Pronator quadratus | **2. Dorsal (Posterior) Compartment:** | Layer | Muscles | |-------|---------| | **Superficial** | Brachioradialis, ECRL, ECRB, EDC, EDM, ECU, Anconeus | | **Deep** | Supinator, APL, EPL, EPB, EIP | **3. Mobile Wad (Lateral):** - Sometimes described separately - Contains: Brachioradialis, ECRL, ECRB **Nerves at Risk:** | Nerve | Compartment | Deficit if Injured | |-------|-------------|-------------------| | **Median nerve** | Volar (deep) | Thenar weakness, thumb-index-middle sensation | | **Anterior interosseous (AIN)** | Volar (deep) | FPL, FDP to index, pronator quadratus | | **Ulnar nerve** | Volar (between FDS and FDP) | Intrinsic hand weakness | | **Posterior interosseous (PIN)** | Dorsal (deep to supinator) | Finger/thumb extension | | **Radial nerve (superficial)** | Mobile wad | Dorsal hand sensation | **Vessels:** | Artery | Course | |--------|--------| | **Radial artery** | Lateral forearm, superficial distally | | **Ulnar artery** | Medial forearm, with ulnar nerve | | **Anterior/posterior interosseous** | Deep to muscles, between radius and ulna | **Critical Time Window:** | Time from Ischemia | Consequence | |--------------------|-------------| | 0-4 hours | Reversible if decompressed | | 4-8 hours | Variable recovery | | >8 hours | Irreversible necrosis, Volkmann contracture | > **Consultant Tip:** Know the compartments and nerves. In the exam, you'll need to describe a fasciotomy approach that decompresses all compartments and avoids nerve injury. **Compartment Pressure Measurement:** **Technique:** | Method | Details | |--------|---------| | **Stryker device** | Commercial pressure monitor | | **Arterial line transducer** | Connected to 18G needle | | **Measurement location** | Within 5cm of fracture site | | **Position** | At level of compartment (not elevated) | **Interpretation:** | Measurement | Interpretation | |-------------|----------------| | **Absolute pressure >30 mmHg** | Traditional threshold | | **Delta P <30 mmHg** | More reliable (Diastolic BP - Compartment pressure) | | **Delta P <20 mmHg** | Definite fasciotomy indication | **This Patient:** - Volar deep pressure: 48 mmHg - Diastolic BP: 80 mmHg - Delta P: 80 - 48 = 32 mmHg (borderline but with clinical signs = fasciotomy) **Indications for Fasciotomy:** **Absolute:** - Clinical diagnosis (pain, pressure, pain with passive stretch) - Delta P <30 mmHg with clinical suspicion - Absolute pressure >30 mmHg with symptoms - Obtunded patient with high-risk injury **Relative/Prophylactic:** - Prolonged ischemia (>4-6 hours) after revascularisation - High-energy fractures in unconscious patients - Combined arterial injury and fracture **When NOT to Measure:** - If clinical diagnosis is clear - go straight to theatre - Measurement should not delay treatment - A negative pressure reading does not exclude compartment syndrome if clinical signs are present **High-Risk Injuries:** | Injury Type | Risk | |-------------|------| | **Supracondylar fracture (paediatric)** | 3-15% | | **Both-bone forearm fracture** | 3-10% | | **Tibial shaft fracture** | 2-10% | | **Crush injuries** | High | | **Arterial injury with repair** | High after reperfusion | > **Consultant Tip:** Compartment syndrome is a clinical diagnosis. Pressure measurements support the diagnosis but should never delay treatment if clinical suspicion is high. **Forearm Fasciotomy Technique:** **Principles:** - Decompress ALL compartments (volar, dorsal, mobile wad) - Avoid nerve injury - Leave wounds open - Plan for delayed closure or skin graft **Approach - Single Volar Incision (Most Common):** **Incision:** - Curvilinear incision from medial epicondyle to palm - Cross wrist crease at an angle (avoid straight line) - Extend into carpal tunnel if needed **Surgical Steps:** | Step | Details | |------|---------| | 1. Skin incision | Full thickness, generous length | | 2. Release lacertus fibrosus | Biceps aponeurosis at elbow | | 3. Superficial volar compartment | Release fascia over FCU, PT, PL, FCR, FDS | | 4. Deep volar compartment | Release fascia over FDP, FPL, PQ | | 5. Identify and protect nerves | Median nerve, ulnar nerve | | 6. Carpal tunnel release | If symptoms extend to hand | | 7. Dorsal compartment | Through separate dorsal incision if needed | **Volar Incision Details:** | Structure | Action | |-----------|--------| | **Lacertus fibrosus** | Divide (may compress brachial artery) | | **Flexor-pronator fascia** | Divide longitudinally | | **FDS/FDP fascia** | Divide to see muscle bellies | | **Transverse carpal ligament** | Divide if carpal tunnel involved | **Dorsal Incision (if required):** - Straight longitudinal incision over dorsal forearm - Between EDC and ECU (through superficial fascia) - Release superficial and deep compartments - Identify and protect PIN **Mobile Wad:** - Can be released through volar incision (lateral extension) - Or through separate incision if needed **Wound Management:** | Stage | Timing | Action | |-------|--------|--------| | **Primary** | Day 0 | Leave open, moist dressings, splint | | **Return to theatre** | 48-72 hours | Reassess, debride if needed | | **Delayed primary closure** | 5-7 days | If swelling resolved | | **Split skin graft** | 7-14 days | If cannot close directly | > **Consultant Tip:** Be generous with your incision. An inadequate fasciotomy is worse than no fasciotomy. Don't try to close the skin - leave it open and plan for delayed closure. **Volkmann Ischemic Contracture:** **Definition:** Late sequela of untreated or inadequately treated compartment syndrome resulting in: - Muscle fibrosis and contracture - Fixed flexion deformity of wrist and fingers - Intrinsic muscle atrophy - Sensory loss in median ± ulnar nerve distribution **Classification (Tsuge):** | Type | Severity | Muscles Involved | |------|----------|------------------| | **Mild** | Localised | FDP (2-3 fingers), FPL only | | **Moderate** | Classic | FDP, FPL, FDS, FCU | | **Severe** | All flexors and extensors | All forearm muscles, fixed contracture | **Clinical Features:** | Finding | Description | |---------|-------------| | **Intrinsic minus posture** | MCP extension, IP flexion | | **Wrist flexion** | Passive - fingers extend; Active - fingers flex (tenodesis) | | **Muscle wasting** | Forearm appears atrophic | | **Sensory loss** | Median ± ulnar distribution | | **Fixed contracture** | Cannot passively extend fingers with wrist extended | **Investigation:** | Test | Purpose | |------|---------| | **Clinical examination** | Assess severity, differentiate from tendon adhesion | | **X-ray** | Assess any bony deformity | | **EMG/NCS** | Nerve function | | **MRI** | Assess muscle viability, fibrosis | **Management by Severity:** **Mild:** | Treatment | Details | |-----------|---------| | **Physiotherapy** | Stretching, splinting | | **Dynamic splinting** | Gradual extension | | **Muscle slide procedure** | If fails conservative | **Moderate:** | Treatment | Details | |-----------|---------| | **Flexor-pronator slide** | Origin release from medial epicondyle | | **Tendon lengthening** | Z-plasty of tight tendons | | **Neurolysis** | Release scarred nerves | **Severe:** | Treatment | Details | |-----------|---------| | **Muscle debridement** | Excise necrotic muscle | | **Free muscle transfer** | Gracilis for finger flexion | | **Tendon transfers** | Salvage function | | **Wrist fusion** | If severe fixed deformity | | **Amputation** | Rarely, for non-functional limb | > **Consultant Tip:** Volkmann contracture is a devastating complication of missed compartment syndrome. It's far better to do an "unnecessary" fasciotomy than to miss a compartment syndrome. **Delayed Complications:** **Differential Diagnosis:** | Diagnosis | Features | |-----------|----------| | **Refracture** | Pain at previous fracture site, deformity | | **Hardware failure** | Pain at plate site, may feel broken screw | | **Non-union** | Ongoing pain at fracture site, movement | | **Stress fracture** | New fracture through plate hole | | **Synostosis** | Loss of rotation, bridging bone | **Most Likely: Refracture or Hardware Failure** **Refracture:** | Risk Factor | Description | |-------------|-------------| | **Through plate holes** | Stress concentration at screw holes | | **After plate removal** | 3-6 month window of weakness | | **Early return to activity** | Before full bone remodelling | **Investigation:** | Test | Findings | |------|----------| | **X-ray forearm** | Fracture line, hardware position | | **CT if needed** | Complex fracture pattern | **Management of Refracture:** | Scenario | Treatment | |----------|-----------| | **Undisplaced, hardware intact** | Cast/splint, activity modification | | **Displaced, hardware intact** | Revision ORIF (longer plate, more screws) | | **Hardware failure** | Remove broken hardware, new fixation | | **Non-union** | Bone graft + revision fixation | **Prevention of Refracture:** | Strategy | Details | |----------|---------| | **Delayed plate removal** | Wait 18-24 months | | **Protected activity** | 6 weeks after plate removal | | **Bridge plate holes** | With new plate if refracture | **Other Late Complications:** | Complication | Management | |--------------|------------| | **Synostosis** | Excision if symptomatic, interposition membrane | | **Malunion** | Corrective osteotomy if functional limitation | | **CRPS** | Multidisciplinary pain management | | **Tendon rupture** | (Over prominent plate) - Plate removal, tendon repair | > **Consultant Tip:** After plate removal from forearm, counsel patients about the 6-week period of increased fracture risk. Screw holes act as stress risers until they remodel. --- ## Key Teaching Points ### Pattern Recognition **This pattern suggests Forearm Compartment Syndrome:** - High-energy forearm injury - Severe pain disproportionate to visible injury - Pain with passive finger extension - Tense, swollen forearm - Paraesthesia (even with intact pulses) **Early Signs (Act on These):** | Sign | Why Important | |------|---------------| | Pain out of proportion | Most sensitive early sign | | Pain with passive stretch | Earliest physical finding | | Tense compartment | Direct evidence of increased pressure | | Paraesthesia | Nerve ischemia | **Late Signs (Don't Wait for These):** | Sign | Significance | |------|--------------| | Paralysis | Irreversible muscle damage | | Pulselessness | Very late, damage already done | | Pallor | Severe ischemia | ### Critical Management Points 1. **Clinical diagnosis** - don't rely solely on pressure measurements 2. **Time is critical** - irreversible damage after 4-8 hours 3. **Adequate fasciotomy** - release ALL compartments 4. **Leave wounds open** - plan for delayed closure 5. **Don't miss the diagnosis** - "unnecessary" fasciotomy is better than Volkmann contracture 6. **Document carefully** - time of diagnosis, time to theatre --- ## Common Examiner Follow-ups **Q: "This patient is intubated and sedated after polytrauma. How do you diagnose compartment syndrome?"** In obtunded patients: - **Cannot rely on pain** - cardinal sign unavailable - **Serial examination** - tense compartments, swelling - **Low threshold for pressure measurement** - Delta P <30 mmHg - **Prophylactic fasciotomy** - in high-risk injuries (crush, vascular injury) - **Continuous monitoring** - if borderline Approach: Have a very low threshold for fasciotomy in unconscious patients with high-risk injuries. It's better to do a fasciotomy that wasn't needed than to miss compartment syndrome. --- **Q: "What is the pathophysiology of compartment syndrome?"** Pathophysiology: | Stage | Events | |-------|--------| | **Initiating event** | Haemorrhage, oedema from injury | | **Pressure rise** | Within fixed compartment | | **Venous outflow obstruction** | Capillary pressure exceeded | | **Further oedema** | Capillary leak | | **Arterial inflow affected** | When pressure exceeds diastolic | | **Ischemia** | Muscle and nerve | | **Necrosis** | If not decompressed | The key concept is that tissue perfusion depends on the difference between arterial pressure and compartment pressure, not arterial pressure alone. This is why Delta P (Diastolic - Compartment pressure) is the key measurement. --- **Q: "What are the causes of compartment syndrome?"** Causes: | Category | Examples | |----------|----------| | **Fractures** | Tibia, forearm, supracondylar (paediatric) | | **Soft tissue injury** | Crush, contusion, burns | | **Vascular** | Arterial injury with ischemia-reperfusion | | **Iatrogenic** | Tight casts, extravasation, positioning | | **External compression** | Prolonged pressure (coma, intoxication) | | **Increased volume** | Bleeding disorders, snake bite | Most common in orthopaedics: Tibial shaft fractures and paediatric supracondylar fractures. --- ## Related Topics - Tibial Compartment Syndrome - Supracondylar Fractures (Paediatric) - Volkmann Ischemic Contracture - Forearm Fractures - Vascular Injury in Trauma - Fasciotomy Techniques