Compartment syndrome

Aetiology

• External compression
  • Cast/ACE wrap
  • Military antishock garments
  • Burn eschar
• Internal compartment expansion (most common)
  • Ischaemia and reperfusion (the classic example - swelling occurs once tissue is reperfused)
    • Muscle injury leads to increased microvascular permeability with efflux of plasma proteins and progressive interstitial oedema. Oxygen radical generation exacerbates both these factors.
    • Risk factors:
      • Ischaemia time >6 hours
      • Young age
      • Insufficient arterial collaterals
      • Acute time course of occlusion
      • Hypotension
      • Poor back-bleeding from distal arterial tree at embolectomy
  • Arterial injury, thrombosis, tourniquet
    • Injuries to popliteal artery are notorious for compartment syndrome (61%) compared with injuries above the knee
  • Burns, frostbite (when there is a circumferential eschar)
  • Cellular insult and swelling
    • Crush injury
      • Combination of direct muscle injury and ischaemia-reperfusion
    • Exercise/exertion/anterior leg compartment
    • Electrical injury/high voltage
  • Blood accumulation and oedema
    • Fractures
      • Mostly tibial/forearm fractures
    • Haemophilia
    • Anticoagulants
    • Venous occlusion (can occur with iliofemoral thrombosis/external pressure)
      • Only occurs with extensive multilevel DVT with occlusion of venous collaterals
  • Miscellaneous
    • IV infiltration/extravasation
    • Drug injection/soft tissue

Risk factors in a/w vascular trauma:

• Hypotension in field or continued hypotension with resus
• Delay in extremity reperfusion of more than 4 hours
• Disproportionate limb pain
• Extremity swelling without significant injury

Pathophysiology

• Occurs due to change in pressure of a closed compartment because of increase in volume, while the surrounding fascia is non-compliant
• Increasing pressure of the compartment tissues reduces the venous outflow, increasing venous capillary pressure
• If capillary pressure becomes higher than arterial pressure, inflow will be reduced
• Ischaemia to local tissues, especially muscle and nerves, results; irreversible necrosis may occur
• Acute compartment syndrome usually occurs at about 30mmHg
• Other relevant definitions:
  • Poiseuille's law:
    • Decreased arterial-venous pressure gradient impedes blood flow
    • Increased ICP may collapse capillaries, decreasing their radius and further increasing resistance to flow
  • 'Critical closing pressure'
    • The concept that there is a pressure above which capillaries collapse and blood flow is arrested
    • This has been disproved in favour of dynamic ICP threshold
  • Absolute ICP threshold
    • An ICP of 30mmHg for 8 hours causes necrosis in dogs, whereas pressures less than that don't tend to
    • However, tissues differ in their susceptibility to high ICP
  • Dynamic ICP threshold
    • Perhaps a better way of defining the threshold ICP required to cause necrosis is by using ICP relative to diastolic pressure
    • Can minimise unnecessary fasciotomy

History:

• Pain out of proportion - 'throbbing' and unrelenting
  • Not improved by immobilisation/reduction of fractures

Exam findings:

• Pressure - earliest objective finding - swollen, hard, tender muscle
• Pain on passive extension/stretch
• Paresis - weakness due to nerve compression - reliable finding in anterior compartment of leg
  • Document motor at compartment
• Paraesthesias or altered sensation distally
  • Early sign of ischaemia
  • Document sensation over the compartment and distally - focus on nerves traversing the compartment
  • Loss of two-point discrimination is a relatively sensitive indicator of developing compartment syndrome (see 'Diagnosis' for how to examine it)
• Paralysis
• Pulse gone (LATE SIGN - end stage - many patients with compartment syndrome still have a pulse)

Diagnosis

• Clinical
  • Overall, it's difficult to diagnose, but the negative predictive value of these exam findings is pretty good, so you can be reassured if they are NOT present
• Measuring compartment pressures
  • Indications:
    • Equivocal cases
    • Unconscious patients
    • Paediatric patients
  • Contraindications
    • Compartment syndrome is already suspected - just do the fasciotomy if you're worried
  • Technique
    • Can be done through an art line or via a handheld Stryker system
    • Record ICP, MAP and diastolic pressure
  • Compartment pressure >30mmHg or a difference between compartment pressure and diastolic BP <30mmHg warrants decompression
  • Normal pressure is <12mmHg

Criteria for fasciotomy: (from Rutherford's)

• Absolute indications:
  • Tense compartment plus either of:
    • Pain with passive motion of muscles traversing the same compartment
    • Paresis or paraesthesiae referable to the same compartment
  • Tense compartment in a patient who cannot be examined serially
  • ICP minus MAP <40mmHg
  • ICP minus DBP <10mmHg
• Relative indications: (ICP measurement may assist)
  • Acute ischaemia >6 hours with few collaterals
  • Combined arterial and venous traumatic injuries
  • Phlegmasia cerulea dolens
  • Tense compartment after crush injury
  • Tense compartment after fracture
  • Tense compartment alone - either fasciotomy or serial observation might be appropriate
• Contraindications:
  • Non-viable extremity
  • Be wary of crush injuries - reperfusion injuries can be significant

Non-operative management - there is NO ROLE for non-op management alone, but do these things pre-op

• Maintain normal BP (hypotension will reduce the arterial/venous gradient)
• Remove any constricting bandages
• Maintain the limb at heart level with no elevation
• Supplemental oxygen

Factors for serial observation:

• Serial observations should be by an experienced surgeon
• If muscle swelling is inevitable due to other factors, early fasciotomy is preferable
• Consider ICP measurement

Common systemic sequelae to watch for:

• Hyperkalaemia
• Myoglobinuria - aggressive resuscitation, forced diuresis, alkalinisation of urine (goal urine pH >6.5)

Specific compartments

Arm

• • Can get just anterior compartment after failed injections into ACF or both compartments in venous occlusion (lying on arm while overdosed) or crush injuries
  • Anterior compartment (deltoid/biceps)
    • Incise medial arm from just distal to deltoid, over biceps, can go across ACF into forearm
  • Posterior compartment (triceps)
    • Incise posteriorly over triceps in midline to about 3cm proximal to elbow, or by extending anterior incision proximally to rotator cuff

Forearm

• • All three compartments can be compromised after burns or extensive long bone trauma with vascular reconstruction
  • Volar - wrist and hand flexors - most commonly affected
    • Contains FDP, FPL and pronator quadratus, all supplied by anterior interosseous artery
    • AIA is especially vulnerable to occlusion by compartment pressures
    • Subcutaneous street drug injection, extravasation of IVF, or insect bites
    • Technique:
      • Incise at lateral part of elbow, descending medially in a curved manner for the proximal half of forearm, then curving laterally down to just above wrist along the ulnar side of FCU tendon (this incision also decompresses lateral compartment). Incorporate the palm by crossing the wrist flexor crease then incising in line with the radial border of the ring finger - basically to line up with carpal tunnel decompression. This incision also endorsed in Valentine's.
      • Large veins crossing incision path often require ligation
      • Elevate the flap along its entire length by developing the plane between fascia and muscle
      • Separate FCU and FDS, including the ulnar neurovascular bundle with the FDS
      • In most cases, the dorsal compartment muscles will be adequately decompressed by the full length volar decompression
  • Dorsal - extensors
    • 6-8cm incision in line from the lateral epicondyle to the radial styloid allows release
  • Lateral - brachioradialis and ECRL and ECRB
    • See above

Hand/foot

• • Rare
  • Try to avoid incising palm/sole

Buttock

• • The three major muscles each have their own fascial compartment
  • No universal technique
  • Longitudinal incision most frequently described

Thigh - rare

• • Occurs with crush injury, venous outflow obstruction, or extensive trauma (explosions/high-velocity rifle)
  • Likely to involve all three compartments when it occurs
  • Anterior - sartorius, quad femoris, femoral nerve
    • Almost always get pain with passive motion
    • Technique:
      • Incise from GT posterolaterally to just above the lateral epicondyle
      • Expose iliotibial band and incise longitudinally along the length of the skin incision, which decompresses the anterior compartment
  • Medial - gracilis, adductor, obturator nerve
    • Medial incision which stays posterior to Hunter's canal and opens the fascia over the gracilis and adductor muscles
    • Decompression is rarely necessary, but can be done through a medial incision over the adductor group
  • Posterior - biceps femoris, semitendinosus, semimembranosus, sciatic nerve
    • Technique:
      • Same incision as above
      • Then reflect vastus lateral medially to expose the lateral intermuscular septum, which is incised over the length of the skin incision to release the posterior compartment

Calf - most common location for compartment syndrome

• • Four-compartment fasciotomy is generally done with two incisions
  • Anterior - tibialis anterior, EHL, EDL, part of peroneus tertius, deep peroneal nerve (check sensation first dorsal webspace and ability to extend big toe)
    • Anterior compartment syndrome occurs after a period of increased physical activity, before the anterior calf tightened and became extremely painful. Needs urgent decompression by an incision from tibial tuberosity to just above the ankle in the midpoint of the anterior compartment mass.
  • Lateral - peroneus longus and brevis, superficial peroneal nerve
  • Superficial posterior - soleus, gastrocnemius, plantaris
    • Technique:
      • Be wary of injury to SPN - branches from common peroneal nerve at or below the proximal fibular head
  • Deep posterior - FHL, TP, FDL, popliteus. Peroneal artery, posterior tibial artery, deep peroneal nerve.

Four-compartment decompression (double-incision technique):

• • • Use a generous incision - 12-20cm - on both sides
    • Lateral/anterior:
      • Incise between fibular shaft and crest of tibia (about 4cm lateral to crest of tibia), right over the intermuscular septum between the anterior and lateral compartments.
      • Raise skin flaps medially and laterally to expose the fascia of the anterior and lateral compartments
      • Clearly identify the intermuscular septum so you can be sure they are both decompressed
      • Open both anterior and lateral compartments with separate, parallel, 12-20cm fascial incisions using Metz scissors (elevate scissors off muscle to avoid injury to nerves, and terminate incisions 5cm distal to fibular heads to avoid the nerves there)
    • Posterior compartments:
      • Incise 1-2cm posterior to tibia, avoiding GSV and nerve
      • Decompress superficial posterior compartment with a longitudinal incision along gastrocnemius fascia
      • To decompress the deep posterior compartment, divide the attachments of the soleus muscle to the tibia or push them away bluntly, exposing the fascia overlying tibialis posterior and the flexor muscles of the foot, then incise the fascia longitudinally, avoiding injury to the posterior tibial artery. Need to see the posterior tibial neurovascular bundle to be assured of having decompressed the deep compartment.
  • Single-incision technique
    • Single incision over fibula down to lateral malleolus
    • Most surgeons now favour double-incision technique
  • Selective decompression:
    • If opening the lateral, anterior and superficial posterior compartments normalises the pressure in the deep posterior compartment, no further decompression is required

Post-op management

• Goals:
  • Prevent further muscle injury or necrosis until muscle swelling subsides sufficiently to permit closure
• Dress open wounds with dry gauze and a soft wrap and elevate
• If questionable viability, saline gauze with daily review and debridement
• Consider VAC if extensive drainage, but not preferable right afterwards
• Posterior splint of leg recommended to prevent foot drop
• Some fasciotomy incisions can be closed in 5-7 days, but avoid closing too soon
• Closure:
  • Delayed primary closure - only for cases with minimal/non-existent muscle swelling, and don't generally do it early post-op
  • Closure by secondary intention - only if medically or nutritionally ill-suited for other options
  • Gradual dermal apposition
  • STSG
  • Myocutaneous flap coverage - for coverage of neurovascular structures or exposed bone in a limb that remains functional

Complications:

• Early:
  • Death - 11-15%
  • Major amputations - 5-21%
  • Wound complications - 4-38%
  • Renal failure - mainly if significant myonecrosis
  • Neurological defects 7-36%
• Late:
  • Impaired sensation at margins of wound 77%
  • Tethered tendons 7%
  • Recurrent ulcerations at fasciotomy site 13%
  • Chronic venous insufficiency 47%
  • Late amputation 7%
  • Volkmann contracture (for missed compartment syndrome) - ischaemic muscle and nerve replaced by fibrosis