Leg and Forearm Fasciotomy

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Chapter 42

Leg and Forearm Fasciotomy

Christopher J. Smith and Harry A. Hoyen

Introduction

Compartment syndrome of the lower extremity is a morbid condition that can lead to limb loss, functional impairment, renal failure, and death. Fasciotomy is required to treat the syndrome and prevent or minimize complications. Compartment syndrome can develop in any anatomic compartment, but the most common site is the lower extremity, in particular the leg. The lower-extremity compartments include those of the buttocks, thigh, leg, and foot.

Compartment syndrome of the forearm and hand is usually seen after blunt trauma. Other conditions that contribute to the development of upper-extremity compartment syndromes include blood dyscrasias, clotting abnormalities, metabolic fluid shifts, longstanding compression, direct fluid injection, and infection. Increased pressure in the forearm compartments results from direct muscle injury, hematoma from soft tissue and osseous injuries, or secondary swelling. The condition can occur in the rapid acute manner or after fluid resuscitation in a seriously injured patient.

The lower leg is divided into four compartments: anterior, lateral, superficial posterior, and deep posterior (Fig. 42-1). The anterior compartment is especially prone to ischemic injury because of its relative paucity of collateral arterial supply. Compared with the other compartments, especially the posterior compartments, the anterior compartment is also more firmly constrained. The spatial relationships among the nerve, vascular, muscular, and bony structures change from proximal to distal in the leg, an especially relevant consideration in performing complete lysis of the posterior compartments (Figs. 42-2 and 42-3).

FIGURE 42–1 Cross-sectional anatomy of leg and fascial compartments.

FIGURE 42–2 Cross-sectional leg anatomy, below knee.

FIGURE 42–3 Cross-sectional leg anatomy, middle and lower tibia.

Etiology of Compartment Syndrome

Compartment syndrome occurs when the compartmental pressure rises sufficiently to prevent adequate tissue perfusion. This condition can result from increased volume in the compartment caused by bleeding, infiltration of exogenous fluid, or reperfusion edema (Fig. 42-4). Increased compartment pressures can also result from external constraint on the compartment, such as with casts, braces, or bandages. A compartment pressure greater than 30 mm Hg is accepted as sufficiently elevated to cause compartment syndrome. This pressure is usually sufficient to restrict venous outflow from the compartment, thereby leading to further increases in compartment pressure.

FIGURE 42–4 Etiology of compartment syndrome.

Compartment syndrome can occur at lower compartment pressures, especially in the patient with hypotension. In clinical practice, compartment syndrome more often occurs in the setting of reperfusion after arterial revascularization for acute, limb-threatening ischemia, as well as in the trauma patient. Reperfusion injury after arterial revascularization is more common after a longer period of ischemia, and prophylactic fasciotomy should be considered when acute ischemia lasts longer than 4 to 6 hours. In the injured extremity, contributing factors to development of compartment syndrome include intracompartmental bleeding, crush or blast injury, and arterial insufficiency from direct vascular injury or shock. In the trauma patient, concomitant venous injury may also lead to venous hypertension, further increasing the risk of compartment syndrome.

Clinical Diagnosis and Decision Making

In the appropriate clinical setting, compartment syndrome should always be considered. Pain is the most prevalent symptom, but the patient may report diminished motor strength and altered or reduced sensation (Fig. 42-5). Pain with passive movement and palpation is extremely common, although the absence of pain in the extremity with compromised neurologic function can be misleading.

FIGURE 42–5 Clinical diagnosis of compartment syndrome.

Findings consistent with arterial insufficiency are not always present, so their absence does not exclude the presence of compartment syndrome. Therefore the presence of palpable pedal pulses (dorsalis pedis artery, posterior tibial artery) does not rule out the diagnosis of compartment syndrome. Because neuronal tissue is sensitive to ischemia, peripheral nerve dysfunction is common in the patient with compartment syndrome and is caused by neuronal ischemia. Diminished motor strength can be tested by assessing dorsiflexion and plantar flexion of the great toe and the ankle, which reflect function of the major muscle groups the leg.

Light touch sensation is often diminished before the development of motor weakness and can best be tested in the web space between the first and second toes. Touch sensation reflects the function of the deep peroneal nerve (Fig. 42-6).

FIGURE 42–6 Common fibular (peroneal) nerve: mixed motor/sensory function.

When findings are equivocal, compartment pressure can be measured by introducing a needle or intravenous catheter into the compartment(s) and directly measuring the pressure (Fig. 42-7). The decision to perform fasciotomy is made on the basis of the index of suspicion, clinical findings, and presence of increased compartment pressure. In the appropriate clinical setting with positive physical findings, compartment pressure measurements are not required to justify fasciotomy.

FIGURE 42–7 Measurement of intracompartmental pressure.

Surgical Principles

The fundamental objective of fasciotomy is to decompress the involved compartment(s) completely. Complete lysis of the containing compartmental fascia is mandatory to allow for adequate expansion of the involved soft tissues. Direct visualization of the fascial envelope is required, and the fasciotomy must extend the entire length of the compartment. Partial lysis of the compartment may provide incomplete decompression and contribute to further morbidity. Inadvertent injury to peripheral nerves can also occur as a result of fasciotomy.

Surgical Anatomy and Technique

Fasciotomy in the leg can be achieved with a single lateral incision. More frequently, both medial and lateral incisions are used (Fig. 42-8). The medial incision is used to decompress the posterior compartments, and the lateral incision addresses the anterior and lateral compartments. The medial incision is made approximately 1 to 2 cm posterior to the medial margin of the tibia.

FIGURE 42–8 Incisions for compartment syndrome of leg.

The posterior deep and superficial compartments are incised along the length of the leg, essentially from the proximal tibia to the medial malleolus. The long saphenous vein and its tributary branches may be encountered in the surgical field, and care should be taken to avoid injury to these vessels. The venous tributaries can be ligated and divided as needed, allowing the saphenous vein to be reflected either anteriorly or posteriorly to facilitate adequate fascial lysis.

The saphenous nerve is parallel and immediately adjacent to the long saphenous vein in the lower leg, and inadvertent injury to this sensory nerve should also be avoided. The proximal third of the soleus muscle is attached to the tibia and fibula. In addition to entering the posterior deep compartment in the middle and distal leg, the soleus must be detached from the tibia for adequate lysis of the proximal portion of the posterior deep compartment (Fig. 42-9).

FIGURE 42–9 Muscles of leg with superficial peroneal nerve: lateral view.

The lateral incision is placed approximately 1 cm anterior to the border of the fibula. The crural fascial envelope in the lateral compartment is identified and lysed. Care should be taken to avoid injury to the superficial fibular nerve as it emanates from beneath the fibularis (peroneus) longus muscle. Proximally, the common fibular (peroneal) nerve can also be inadvertently injured.

The anterior intermuscular septum is then identified and the anterior compartment crural fascia incised in a longitudinal direction.

Forearm Fascotomy

The forearm compartments consist of a single volar compartment and two dorsal compartments. The volar compartment has distinct septae within its muscle groups. There are typically two to three subcompartments arranged in a volar-to-dorsal direction. The most superficial of these contains the flexor carpi radialis, palmaris longus, flexor carpi ulnaris, and superficial portion of the pronator teres (Fig. 42-10). The next division contains the flexor digitorum superficialis, and the flexor digitorum profundus and flexor pollicis longus make up the final section. The main dorsal compartments are divided into the extrinsic finger extensors, thumb extensors with the index proprius, and the wrist extensors with the brachioradialis muscle. These anatomic divisions are important to consider during fasciotomy of the forearm.

FIGURE 42–10 Individual muscles of forearm: flexors and extensors.

The fascia overlying the respective compartments should be completely incised. The septae between the muscle groups is also incised to ensure full decompression (Figs. 42-12 and 42-13). Often the deepest or most dorsal volar subcompartment is involved in early cases. This compartment is not well visualized without a deeper dissection. In more severe cases this compartment often has the most muscle destruction. The relationship of the median and ulnar nerves within the compartments is such that the ulnar nerve lies adjacent to the flexor digitorum profundus muscle, and the median nerve is generally between the flexor digitorum superficialis and flexor digitorum profundus muscles in the midforearm. The anatomy can be quite distorted as a result of the excessive swelling. The necessity for further surgical intervention is determined by the extent of muscle necrosis.