Overview
Definition:
Compartment pressure measurement is a diagnostic technique used to quantify the elevated intracompartmental pressure within a fascial compartment of a limb
It is crucial in the diagnosis of acute compartment syndrome (ACS), a surgical emergency characterized by increased pressure within a closed fascial space, compromising circulation and tissue viability
Measurement involves inserting a needle or catheter into the affected compartment and recording the pressure, typically using a manometric device or a digital monitor.
Epidemiology:
Acute compartment syndrome occurs most commonly after long bone fractures (tibia, femur), crush injuries, and severe soft tissue contusions
It is also seen post-reperfusion injury, with snake bites, and with prolonged external compression
The incidence varies greatly depending on the mechanism of injury, with tibia fractures reporting rates from 2-10%
Certain populations, such as those with pre-existing muscle hypertrophy or reduced compartment volume, may be at higher risk
Early and accurate diagnosis is paramount for limb salvage.
Clinical Significance:
Failure to diagnose and manage acute compartment syndrome promptly can lead to irreversible muscle and nerve damage, resulting in Volkmann's ischemic contracture, chronic pain, weakness, and eventual amputation
Compartment pressure measurement is the definitive diagnostic tool when clinical suspicion is high but signs are equivocal
Accurate measurement guides the decision for emergent fasciotomy, thereby preventing devastating sequelae and preserving limb function
Understanding this technique is vital for surgeons managing trauma, orthopedic, and vascular emergencies.
Clinical Presentation
Symptoms:
Severe pain disproportionate to the injury
Pain that is increased with passive stretch of the muscles in the compartment
Paresthesia or numbness in the distribution of the involved nerves
Pallor of the affected limb
Weakness or paralysis of the muscles in the compartment
The classic "5 Ps" (pain, pallor, pulselessness, paralysis, paresthesia) are often described, but pulselessness and pallor are late signs and indicate irreversible damage.
Signs:
Tense and swollen compartment on palpation
Pain with passive stretch of the affected muscles is a key physical finding
Decreased sensation in the distribution of sensory nerves supplying the compartment
Weakness of motor function of the muscles within the compartment
Absent distal pulses and pallor are late and ominous signs indicating significant ischemia.
Diagnostic Criteria:
No definitive universally accepted diagnostic criteria exist as it is primarily a clinical diagnosis supported by objective pressure measurements
However, a generally accepted threshold for intervention is an elevated compartment pressure
Some guidelines suggest a delta pressure (diastolic blood pressure minus compartment pressure) of less than 20-30 mmHg as indicative of compartment syndrome, prompting urgent surgical intervention
A compartment pressure greater than 30-40 mmHg in adults, or >20 mmHg in children, is often considered sufficient for fasciotomy, especially in the presence of clinical signs.
Diagnostic Approach
History Taking:
Detailed mechanism of injury is critical: type of trauma (blunt, crush, penetrating), energy of impact, duration of impaction
History of any comorbidities that might affect perfusion (e.g., peripheral vascular disease, diabetes)
Previous musculoskeletal injuries to the affected limb
Red flags include pain disproportionate to injury, pain with passive stretch, and altered sensation.
Physical Examination:
Systematic examination of the affected limb
Assess for swelling, tenseness, and tenderness of the compartments
Evaluate for pain with passive stretch of the muscles within each compartment
Assess distal pulses (radial, dorsalis pedis, posterior tibial)
Test sensation in the distribution of superficial and deep nerves supplying the compartment
Assess motor function of the muscles within the compartment.
Investigations:
The cornerstone investigation is compartment pressure measurement
Other investigations may include: Arterial Doppler Ultrasound: To assess distal pulses and blood flow, though it may be normal in early ACS
MRI: Can show muscle edema, but is time-consuming and not for acute settings
X-ray: To identify associated fractures
Lactate levels: May be elevated due to tissue ischemia.
Differential Diagnosis:
Peripheral nerve injury: Symptoms may overlap, but pressure is not elevated
Deep vein thrombosis: Pain, swelling, but typically not disproportionate pain with passive stretch
Arterial insufficiency: Pain, pallor, pulselessness, but often a history of vascular disease and not always compartment-specific pain
Cellulitis: Redness, warmth, tenderness, but usually associated with fever and often affects the skin more superficially
Fracture blisters: Localized edema and pain, but not diffuse compartment pressure elevation.
Management
Initial Management:
Immediate discontinuation of any constricting dressings, bandages, or casts
Elevation of the limb to the level of the heart (but not above, to avoid compromising arterial inflow)
Analgesia to manage pain
Correction of any coagulopathy
Avoidance of external compression.
Medical Management:
Primarily supportive and aimed at managing pain and preventing further complications
Aggressive pain control with systemic analgesics
Tetanus prophylaxis if indicated
Antibiotics are generally not indicated unless there is an open fracture or evidence of infection
Vasopressors should be avoided if possible due to risk of exacerbating ischemia.
Surgical Management:
Emergent fasciotomy is the definitive treatment for acute compartment syndrome
This involves incising the fascia overlying the tense compartments to relieve pressure and restore blood flow
The extent of fasciotomy depends on the involved compartments and the mechanism of injury
For the lower leg, lateral and medial fasciotomies are typically performed
For the forearm, volar and dorsal fasciotomies are indicated
In severe cases, multiple compartments may require decompression
The wounds are often left open and managed with delayed primary closure or skin grafting after several days.
Supportive Care:
Close monitoring of vital signs and limb perfusion
Serial physical examinations to assess for improvement or worsening of symptoms
Regular reassessment of compartment pressures if clinical suspicion persists
Wound care for open fasciotomy wounds
Physical therapy and rehabilitation are essential once the acute phase has resolved to regain function and prevent contractures.
Complications
Early Complications:
Infection of the fasciotomy wounds
Nerve injury (e.g., superficial peroneal nerve)
Muscle necrosis and infarction
Post-operative bleeding
Wound dehiscence.
Late Complications:
Volkmann's ischemic contracture (permanent functional deficit)
Chronic pain and paresthesia
Muscle atrophy and weakness
Limb length discrepancies if growth plates are involved in pediatric patients
Non-union or malunion of associated fractures
Amputation if diagnosis and treatment are delayed.
Prevention Strategies:
High index of suspicion for ACS in at-risk patients
Serial monitoring of compartment pressures in high-risk scenarios
Avoiding circumferential dressings or casts that can impede circulation
Prompt and complete fasciotomy when indicated
Meticulous surgical technique during fasciotomy
Careful wound management postoperatively.
Prognosis
Factors Affecting Prognosis:
The most critical factor is the time to fasciotomy
The longer the duration of ischemia, the worse the outcome
The severity of the initial injury and the extent of muscle and nerve damage also play significant roles
Patient factors such as age and comorbidities can influence recovery.
Outcomes:
With prompt diagnosis and fasciotomy (ideally within 6-12 hours of symptom onset), limb salvage rates are high and functional outcomes can be good
However, some degree of permanent functional deficit, including chronic pain, weakness, and altered sensation, is common even with timely intervention
Delayed treatment leads to a significantly higher risk of irreversible damage, contractures, and potential amputation.
Follow Up:
Regular follow-up is required to monitor wound healing, assess for complications, and initiate rehabilitation
This typically involves wound care evaluations, physical therapy, and ongoing assessment of motor and sensory function
Long-term follow-up may be necessary to manage chronic pain and functional limitations
Patients should be educated about warning signs of recurrence or new complications.
Key Points
Exam Focus:
The diagnosis of acute compartment syndrome is primarily clinical, supported by compartment pressure measurement
A delta pressure of <20-30 mmHg is a strong indicator for fasciotomy
Emergent fasciotomy is the definitive treatment
Time is muscle
prompt intervention is critical for limb salvage.
Clinical Pearls:
Always suspect compartment syndrome in severe lower extremity trauma, crush injuries, and post-reperfusion syndromes
Pain with passive stretch is a more sensitive indicator than decreased pulses
Never dismiss a patient's pain as "just fracture pain"
aggressively evaluate for ACS
Be proficient with different compartment pressure measurement techniques (needle, catheter, slit catheter).
Common Mistakes:
Delaying diagnosis due to reliance on late signs like pulselessness
Underestimating the severity of pain and its disproportion to injury
Failing to measure compartment pressures when clinical suspicion is high
Inadequate fasciotomy (missing involved compartments or insufficient decompression)
Over-reliance on imaging over clinical judgment for ACS diagnosis.