Residency · Residency · Orthopedic Surgery

Compartment Syndrome: Diagnosis, Monitoring, and Fasciotomy

Pathophysiology

Mechanism

Compartment syndrome occurs when elevated pressure within a closed fascial compartment compromises tissue perfusion. As tissue pressure rises above capillary perfusion pressure, ischemia develops and cellular death follows. Normal compartment pressure ranges from 0 to 8 mmHg. The critical threshold is reached when compartment pressure approaches diastolic blood pressure. An ischemic cascade ensues: rising pressure decreases the arteriovenous gradient, which reduces capillary blood flow, leading to tissue hypoxia, which causes cellular edema, which further elevates pressure in a self-reinforcing vicious cycle.

Tissue Tolerance

Muscle and nerve are the tissues most sensitive to ischemia. Irreversible muscle damage begins after 4-6 hours of ischemia. Nerve tissue develops functional deficits after 2-4 hours and sustains irreversible damage after 8 hours. Once significant muscle necrosis begins, myoglobin release into the circulation can trigger rhabdomyolysis and acute renal failure.

Etiology

Compartment syndrome results from either decreased compartment volume (tight casts or dressings, burn eschar, closure of fascial defects) or increased compartment contents (fracture hematoma, bleeding from coagulopathy or anticoagulation, reperfusion injury after vascular repair, crush injury, intravenous fluid extravasation, or snake bite). The most common cause is fracture, particularly tibial shaft fractures, which account for approximately 40% of compartment syndrome cases.

Clinical Diagnosis

The 6 Ps (Classic Teaching)

The classic teaching describes six P signs: Pain (out of proportion and with passive stretch), Pressure (tense, swollen compartments), Paresthesias (early nerve ischemia), Paralysis (a late finding indicating advanced ischemia), Pulselessness (very late, as pulses often persist until late stages), and Pallor (unreliable as skin color may appear normal).

Key Clinical Features

Pain out of proportion to the injury is the most sensitive early clinical finding. This manifests as pain disproportionate to the fracture pattern, increasing analgesic requirements, and failure to respond to appropriate doses of pain medication. Pain with passive stretch of muscles in the affected compartment is highly specific: passive plantarflexion of the toes provokes pain in the anterior compartment, passive dorsiflexion of the toes in the deep posterior compartment, and passive extension of the fingers in the volar forearm compartment. Tense compartments on palpation (firmness or woodiness) provide direct physical evidence. Paresthesias develop in the distribution of nerves traversing the affected compartment; first web space numbness (deep peroneal nerve territory) suggests anterior compartment involvement. Paralysis and pulselessness are late findings that should never be waited for before intervening.

Clinical Diagnosis Challenges

Clinical diagnosis is unreliable in obtunded or intubated patients, those with head injuries, pediatric patients, and those under regional anesthesia. In these populations, the threshold for pressure measurement should be very low. Importantly, peripheral pulses typically remain palpable even in established compartment syndrome; their presence does not exclude the diagnosis. Regional anesthesia (nerve blocks, epidurals) may mask early symptoms, and in high-risk patients, these techniques should either be avoided or supplemented with continuous pressure monitoring.

Pressure Monitoring

Absolute Pressure Thresholds

The traditional threshold for fasciotomy is a compartment pressure exceeding 30 mmHg. However, this approach has significant limitations because it does not account for the patient's perfusion status. A hypotensive patient may develop compartment syndrome at lower absolute pressures.

Delta Pressure (Differential Pressure)

The delta pressure (diastolic blood pressure minus compartment pressure) provides a more physiologically meaningful measurement. Fasciotomy is indicated when delta P falls below 30 mmHg, as described by McQueen and Court-Brown. This threshold accounts for patient hemodynamics and is the recommended clinical standard at most institutions. For example, if the diastolic blood pressure is 60 mmHg and the compartment pressure is 35 mmHg, the delta P is 25 mmHg, indicating fasciotomy is needed.

Measurement Techniques

The Stryker needle device is a handheld, single-use instrument that is widely available. Using sterile technique, the needle is inserted into the compartment, a small volume of saline is injected, and the equilibrium pressure is read. An arterial line transducer provides continuous monitoring and is useful for ICU patients. The Whitesides technique uses a manometer with a saline-filled syringe and tubing. All compartments at risk must be measured, with the highest pressure guiding the decision. Measurements should be taken at the level of the fracture, where pressures are highest. If clinical suspicion is high, treatment should proceed even when pressure measurements are borderline, as clinical judgment supersedes numbers.

Continuous Monitoring

Continuous monitoring is indicated for obtunded patients, polytrauma patients in the ICU, and those with equivocal clinical examinations. A catheter is placed in the at-risk compartment and connected to a continuous pressure monitor. Serial measurements are taken every 1-2 hours. The catheter is removed when pressures remain consistently below 20 mmHg and the clinical examination is reassuring.

Anatomy of Compartments

Lower Leg (4 Compartments)

The anterior compartment contains the tibialis anterior, extensor hallucis longus, extensor digitorum longus, deep peroneal nerve, and anterior tibial artery. It is the most commonly affected compartment. Pain is elicited by passive plantarflexion of the toes. The lateral compartment contains the peroneus longus and brevis along with the superficial peroneal nerve. Pain occurs with passive inversion of the foot. The superficial posterior compartment houses the gastrocnemius, soleus, and sural nerve, with pain on passive dorsiflexion of the ankle. The deep posterior compartment contains the tibialis posterior, flexor hallucis longus, flexor digitorum longus, posterior tibial artery, tibial nerve, and peroneal artery. Pain is provoked by passive dorsiflexion of the toes. This is the most commonly missed compartment during fasciotomy.

Forearm (3 Compartments)

The volar (anterior) compartment contains the flexor muscles, median nerve, ulnar nerve, and anterior interosseous nerve. It is the most commonly affected forearm compartment, with pain elicited by passive finger and wrist extension. The dorsal (posterior) compartment houses the extensors and posterior interosseous nerve. The mobile wad contains the brachioradialis, ECRL, and ECRB.

Thigh (3 Compartments)

The thigh has anterior, posterior, and medial (adductor) compartments. Thigh compartment syndrome is less common but can occur with femoral fractures, crush injuries, and anticoagulation.

Hand (10 Compartments)

The hand contains 4 dorsal interossei, 3 volar interossei, thenar, hypothenar, and adductor pollicis compartments.

Foot (9 Compartments)

The foot has medial, lateral, superficial central, deep central (calcaneal), and 4 interosseous compartments. Foot compartment syndrome is associated with calcaneus fractures and crush injuries. If missed, it results in claw toe deformity.

Fasciotomy Technique

Lower Leg -- Two-Incision Four-Compartment Release

Anterolateral Incision

A 15-18 cm longitudinal incision is made over the anterolateral leg, approximately 2 fingerbreadths lateral to the anterior tibial crest. The intermuscular septum between the anterior and lateral compartments is identified. The anterior compartment fascia is released longitudinally, followed by the lateral compartment fascia. The superficial peroneal nerve must be avoided as it exits the lateral compartment in the distal third.

Posteromedial Incision

A 15-18 cm longitudinal incision is placed 2 cm posterior to the medial tibial border. The greater saphenous vein and saphenous nerve (which lie anterior to this incision) are avoided. The superficial posterior compartment fascia is released. The soleal bridge (attachment of the soleus to the tibia) is then detached to access the deep posterior compartment, which is the most commonly missed during fasciotomy and must be actively released along the full length of the incision.

Key Technical Points

Fasciotomy incisions must extend the full length of the compartment because the entire compartment must be decompressed. An incomplete fasciotomy is worse than no fasciotomy at all, as it creates a localized window of further pressure increase. Fasciotomy skin incisions are left open and should never be primarily closed. Sterile dressings or NPWT are applied. The wound is reassessed at 48-72 hours for delayed primary closure, skin grafting, or continued NPWT management.

Forearm Fasciotomy

Volar fasciotomy uses a curvilinear incision extending from proximal to the medial epicondyle, across the antecubital fossa, and ulnar to the carpal tunnel. The lacertus fibrosus is released along with the superficial and deep flexor compartments and the carpal tunnel. Dorsal fasciotomy uses a straight longitudinal incision over the mobile wad to release the dorsal compartment. In most cases, both volar and dorsal compartments must be released.

Thigh Fasciotomy

The lateral approach uses a single lateral incision that releases both the anterior and posterior compartments through the lateral intermuscular septum. A separate medial approach may be needed for the adductor compartment.

Wound Management After Fasciotomy

Negative Pressure Wound Therapy (NPWT)

NPWT applied to open fasciotomy wounds reduces edema, promotes tissue contraction, and facilitates delayed primary closure. Dressing changes occur every 48-72 hours.

Closure Options

Delayed primary closure at 5-7 days, when swelling has subsided, is the preferred approach. The shoelace technique (vessel loop closure) allows progressive daily approximation of wound edges. If skin edges cannot be approximated, split-thickness skin grafting is performed. Dermal substitutes are used for larger defects. Wound closure or coverage should ideally be achieved within 5-10 days to minimize infection and desiccation risk.

Delayed Presentation and Missed Compartment Syndrome

Volkmann Contracture (Upper Extremity)

Volkmann contracture is the sequela of missed forearm compartment syndrome. Ischemic contracture of the forearm flexor muscles produces the classic posture: flexed wrist, extended MCP joints, and flexed IP joints. Treatment depends on severity: mild cases are managed with splinting and therapy, moderate cases with a flexor muscle slide procedure, and severe cases with free functional muscle transfer.

Late Fasciotomy

If more than 8-12 hours of ischemia have elapsed, fasciotomy may actually be harmful. Release of necrotic muscle can trigger reperfusion syndrome characterized by hyperkalemia, metabolic acidosis, and renal failure (crush syndrome). If muscles are clearly necrotic and nonviable after 8-12 hours, some authors advocate against fasciotomy, though this remains a clinical judgment call with no absolute time cutoff. If late fasciotomy is performed, the team must prepare for reperfusion complications with aggressive hydration, monitoring for hyperkalemia, and consideration of sodium bicarbonate infusion.

Lower Extremity -- Missed Compartment Syndrome

Missed compartment syndrome in the lower extremity results in characteristic sequelae: claw toe deformity from deep posterior compartment involvement, foot drop from anterior compartment necrosis, contractures, chronic pain, and significant disability. These patients may require reconstructive procedures including tendon transfers, osteotomies, and soft tissue releases.

<image>A cross-sectional anatomical diagram of the lower leg at the mid-calf level showing all four compartments. Label the anterior compartment (tibialis anterior, EHL, EDL, deep peroneal nerve, anterior tibial artery), lateral compartment (peroneus longus and brevis, superficial peroneal nerve), superficial posterior compartment (gastrocnemius, soleus, sural nerve), and deep posterior compartment (tibialis posterior, FHL, FDL, posterior tibial artery, tibial nerve). Show the two fasciotomy incision locations: anterolateral (2 fingerbreadths lateral to the tibial crest) and posteromedial (2 cm posterior to the medial tibial border). Indicate the tibia, fibula, and interosseous membrane.</image>

<image>A clinical illustration of the two-incision four-compartment fasciotomy technique of the lower leg. Show a lateral view of the leg with the anterolateral incision marked and a medial view with the posteromedial incision. For each incision, show the fascial release with the fasciotomy scissors opening the fascia longitudinally. Include an inset showing the soleal bridge being released to access the deep posterior compartment. Label each compartment being released and the key structures to avoid (superficial peroneal nerve, saphenous vein).</image>

<image>A flowchart for the clinical decision-making pathway for suspected compartment syndrome. Start with clinical suspicion (pain out of proportion, tense compartment, increasing analgesic requirements). Branch to: (1) Alert, cooperative patient — clinical diagnosis sufficient if classic findings present — proceed to fasciotomy; (2) Obtunded/unreliable exam — measure compartment pressures — if delta P less than 30 mmHg, proceed to fasciotomy; if delta P greater than 30 mmHg, continuous monitoring. Include a decision point for late presentation (greater than 8-12 hours) with considerations for reperfusion syndrome.</image>

Clinical Pearls

Pain out of proportion to the injury and pain with passive stretch are the earliest and most reliable clinical findings; do not wait for the late findings of paralysis and pulselessness. Peripheral pulses are typically present even in established compartment syndrome, so a palpable pulse does not rule out the diagnosis. Delta pressure (diastolic BP minus compartment pressure) less than 30 mmHg is the recommended intervention threshold, superior to absolute pressure measurement alone. The deep posterior compartment is the most commonly missed during fasciotomy; the soleal bridge must be actively released. Fasciotomy incisions must extend the full length of the compartment because incomplete release worsens the condition. Regional anesthesia (nerve blocks, epidurals) can mask compartment syndrome symptoms in high-risk patients and should be used with caution or supplemented with continuous pressure monitoring. In obtunded, intubated, or pediatric patients, the threshold for pressure measurement should be very low since clinical examination is unreliable. Late fasciotomy (beyond 8-12 hours) may cause reperfusion injury, and the team must be prepared for hyperkalemia, metabolic acidosis, and renal failure.

References

• McQueen MM, Court-Brown CM. Compartment monitoring in tibial fractures: the pressure threshold for decompression. J Bone Joint Surg Br. 1996;78(1):99-104.
• McQueen MM, et al. Acute compartment syndrome: who is at risk? J Bone Joint Surg Br. 2000;82(2):200-203.
• Schmidt AH. Acute compartment syndrome. Injury. 2017;48 Suppl 1:S22-S25.
• Whitesides TE, et al. Tissue pressure measurements as a determinant for the need of fasciotomy. Clin Orthop Relat Res. 1975;(113):43-51.
• Matsen FA 3rd. Compartmental syndromes. N Engl J Med. 1979;300:1210-1211.

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