Compartment Syndrome Testing

John E. Glorioso

John H. Wilckens

INTRODUCTION

Exertional leg pain is a common complaint in the running athlete. The differential diagnosis includes stress fracture, tibial stress reaction such as periostitis or medial tibial stress syndrome (shin splints), tendonitis, nerve compression or entrapment, and chronic exertional compartment syndrome (CECS).
Although a classic history may suggest the diagnosis of CECS, an exercise challenge and measurement of compartmental pressures are essential to confirm the diagnosis.
Intracompartmental pressure measurement is the most clinically useful test to rule out or confirm CECS as the etiology of exertional leg pain.

COMPARTMENT SYNDROMES

Compartment syndrome exists when tissue pressures are elevated in a restricted fascial space, resulting in decreased perfusion causing nerve and muscle ischemia.
Compartment syndromes in the athlete can occur in two forms, acute and chronic. The distinction between the two is in the reversibility of the ischemic insult.
In acute compartment syndrome, the ischemia is irreversible and rapidly leads to tissue necrosis unless emergently decompressed via fasciotomy.
- Most commonly occurs with acute trauma (fracture) or soft tissue/muscle injury (crush injury, rhabdomyolysis).
- A clinical diagnosis is made by historical and physical examination findings. Characteristic findings include pain out of proportion to injury, presence of paresthesias and sensory deficits, tense and swollen compartment on palpation, decreased or loss of active motion, and severe pain with passive stretch.
- Treatment is emergent surgical decompression via fasciotomy.
- If doubt exists as to the diagnosis in the acute presentation, intracompartmental pressure measurements may be indicated prior to emergent fasciotomy.
- Resting intracompartmental pressure of > 30 mm Hg is the generally accepted level that can be associated with decreased blood flow and resultant muscle and nerve ischemia (2).
CECS involves reversible ischemia that is exercise induced and occurs at a predictable distance/intensity of exertion.
- This form is much more common in athletes.
- The reversible ischemia of exertional compartment syndrome occurs secondary to a noncompliant osseofascial compartment that is not responsive to the expansion of muscle volume that occurs with exercise.
- CECS is characterized by recurrent episodes of a transient elevation in the intracompartmental pressure, which subsides with rest or cessation of activity.
- Any athlete can develop CECS; however, runners are most commonly affected (6,15,20).
Although compartment syndrome testing is useful in the diagnosis of acute compartment syndrome, the following discussion applies to the use of intracompartmental pressure measurements for the chronic exertional form of compartment syndrome.

The Leg Compartments

The leg contains four anatomically distinct muscle compartments with structural support provided by the tibia and fibula. Each compartment is covered by a tight fascia and has a unique neurovascular supply that creates distinct pathology (Table 23.1).
The anterior compartment contains muscles used for extension of the toes and dorsiflexion of the ankle: the tibialis anterior, the extensor hallucis longus, and the extensor digitorum longus. Blood supply to the anterior compartment is from the anterior tibial artery. The deep peroneal nerve provides innervation as it passes through the compartment.
The lateral compartment contains the evertors of the foot: the peroneus longus and the peroneus brevis. Nerve supply is via the superficial peroneal nerve. Blood supply is from branches of the peroneal artery.
The superficial posterior compartment contains the plantarflexors of the foot: the gastrocnemius, soleus, and plantaris. These muscles are supplied by branches of the tibial nerve.

The deep posterior compartment contains the muscles of toe flexion, ankle plantar flexion and inversion, the flexor hallucis longus, the flexor digitorum longus, and the tibialis
posterior. These muscles are supplied by the tibial nerve and posterior tibial artery.

Table 23.1 Muscle Compartments

Compartment	Nerve	Muscles	Vascular
Anterior	Deep peroneal	Tibialis anterior Extensor hallucis longus Extensor digitorum longus Peroneus tertius	Anterior tibial artery and vein
Lateral	Superficial peroneal	Peroneus longus Peroneus brevis
Superficial posterior	None	Gastrocnemius Soleus Plantaris	None
Deep posterior	Tibial nerve	Posterior tibialis Flexor hallucis longus Flexor digitorum longus Popliteus	Posterior tibial artery and vein Peroneal artery and vein

A fifth compartment has been described. The fascia surrounding the posterior tibialis has been described as a separate and distinct compartment (5).

PATHOPHYSIOLOGY

Four factors have been identified that may contribute to an increase in the intracompartmental pressure seen during exercise (17):
- Enclosure of compartmental contents in an inelastic fascial sheath
- Increased volume of the skeletal muscle with exertion resulting from blood flow and edema
- Muscle hypertrophy as response to exercise
- Dynamic contraction factors due to the gait cycle
The transient increase in pressure within the myofascial compartment compromises blood flow. When tissue perfusion is not adequate to meet the metabolic demands, the result is traversing neurologic and muscular ischemia, pain, and impairment of muscular function.

CLINICAL PRESENTATION

In CECS, the characteristic complaint is recurrent exercise-induced leg discomfort that occurs at a well-defined and reproducible point of activity and increases if the training persists.
The quality of pain is described as a tight, cramp-like, or squeezing ache over a specific compartment of the leg. Relief of symptoms occurs only with discontinuation of activity.
Neurologic complaints such as paresthesias of the leg or foot with exertion may indicate involvement of the nerve traversing the compartment.
- Nerve entrapment syndromes of the lower extremity often present with similar complaints and should be included in the differential diagnosis.
At rest, the physical examination is commonly unremarkable with a normal gait and normal lower extremity examination. A muscle herniation through a fascial defect may be the only clinical abnormality noted.
An exercise challenge followed by postexercise clinical examination is helpful in establishing the diagnosis (11).
- After reproduction of discomfort, the athlete should be assessed for tenderness, tightness, and swelling over the involved compartment.
- The tenderness noted should involve the muscle mass and not the bone or muscle-tendon junction.
- Neurologic and vascular examination should be completed.
Although history may be suggestive of CECS, no physical examination finding can firmly establish the diagnosis (14,25). Diagnosis based solely on clinical presentation can lead to misdiagnosis, inappropriate therapy, and/or delay of proper therapy (20).

INDICATIONS FOR INTRACOMPARTMENTAL PRESSURE MEASUREMENTS

Any patient with clinical evidence of CECS should be considered for intracompartmental testing.
- Significant historical features include a recurrent, exercise-induced leg discomfort that increases as the training persists and dissipates on cessation of activity.
- Pain quality described as a tight, cramp-like, or squeezing ache over a specific compartment of the leg.
- Paresthesias of the leg or foot with exertion.
An exercise challenge with detailed physical examination immediately after reproduction of symptoms will lead to a more judicious use of invasive techniques (11).