Compartment Syndrome of the Forearm
Compartment Syndrome of the forearm is a condition in which pressure inside the closed osteofascial compartment increases to such an extent that there is a compromise of microcirculation, leading to tissue damage. In other words, it can be described as a bleeding or edema that leads to increased pressure within the fascial compartment and compromises circulation within that space, as well as the function of tissues in that area, causing ischemia. It may or may not be preceded by fracture or traumatic injury. Although uncommon, compartment syndrome of the forearm is a well recognized diagnosis that can lead to significant morbidity and mortality if not diagnosed and treated early in the clinical course.
- Acute, sensory changes develop after 30 minutes of ischemia
- Acute, irreversible nerve damage in 12 to 24 hours
- Acute, irreversible muscle changes (i.e., necrosis) in 3 to 8 hours
- Fractures of the forearm - including both diaphyseal forearm fractures and fractures of the distal radius (most common)
- Crush injuries
- Penetrating trauma
- Reperfusion injury
- Angioplasty or angiography
- Intravenous line extravasations
- Injection of illicit drugs
- Coagulopathies or bleeding disorders
- Hematoma in patients treated with anticoagulants
- Constrictive dressings or casts
- Insect bites
There are four compartments of the forearm: dorsal, superficial volar, deep volar, and the mobile wad. The dorsal and volar compartments are separated by the interosseous membrane.
Houses the finger extensors and is innervated by the posterior interosseous nerve. It includes:
- Extensor digitorum
- Extensor digiti minimi
- Extensor carpi ulnaris
- Abductor pollicis longus
- Extensor pollicis brevis
- Extensor pollicis longus
- Extensor indicis.
The volar compartment consists of the superficial volar and deep volar compartment. The superficial volar compartment is innervated by median and ulnar nerve and includes:
- Flexor carpi ulnaris
- Palmaris longus
- Flexor digitorum superficialis
- Flexor carpi radialis
- Pronator teres
Deep volar compartment (Innervated by Anterior Interosseous Nerve (AIN))
- Flexor digitorum profundus (medial half by Median nerve and lateral half by AIN)
- Flexor pollicis longus
- Pronator quadratus
Mobile wad compartment
It is the fourth compartment in the forearm and includes the:
- Extensor carpi radialis longus & brevis. The mobile wad compartment is innervated by the superficial radial nerve
In general, the deeper forearm musculature is more prone to ischemic and compressive injury due to fascial boundaries that prevent expansion of these muscles.
The radius and the ulna are bridged by the very stiff interosseous membrane. Immediately volar to this membrane are the flexor pollicis longus and flexor digitorum profundus muscles. These are the more frequently damaged muscles in end-stage compartment syndrome.
The superficial flexor muscles of the forearm (flexor digitorum superficialis, flexor carpi ulnaris, and flexor carpi radialis) are also prone to ischemic injury but appear to be less so because of their more superficial position and somewhat less-stiff superficial fascia.
On the dorsum of the forearm are the wrist and finger extensors that again can be damaged with forearm compartment syndrome but not as frequently as those of the deep flexor compartments.
Finally, the mobile wad of the forearm consisting of the brachioradialis and the radial wrist extensors can also be damaged in the setting of forearm compartment syndrome. Contractures of the mobile wad are not common.
The median nerve is most frequently damaged with forearm compartment syndrome because of its deeper course in the volar forearm, and is often encased by fibrosis in the setting of Volkmann’s ischemic contracture. In the mid-forearm, the median nerve runs between the deep and superficial volar forearm compartments. Additionally, the anterior interosseus nerve (AIN) is found in the floor of the deep volar compartment. The AIN provides motor innervation to the deep flexors (flexor digitorum profundus and flexor pollicis longus), thus a compartment syndrome primarily affecting the deep volar compartment can have a doubly devastating result on these finger flexors.
The ulnar nerve can also be affected by compartment syndrome, especially those resulting in a severe ischemic contracture. In the mid-forearm, the ulnar nerve is bounded by the flexor digitorum superficialis, the flexor carpi ulnaris, and the flexor digitorum profundus. Despite being relatively more superficial than the median nerve, the ulnar nerve can certainly suffer significant damage as a result of compartment syndrome.
The radial nerve runs in the floor of the mobile wad and the posterior interosseus nerve (PIN) is in the floor of the dorsal compartment. The position of the radial nerve and PIN makes them somewhat less prone to ischemic damage; however, they can still be affected by forearm compartment syndrome, especially if severe enough to involve the dorsal forearm or mobile wad.
Patients typically present with swelling of the forearm and complains of pain and difficulty with hand and wrist motion, particularly with passive motion. It may also be accompanied with paresthesias of the hand depending on the clinical course. Compartment syndrome hallmarks have been the 5 Ps: pain out of proportion, pallor, paresthesias, paralysis, and pulselessness. Pain out of proportion and pain with passive stretching of the fingers are considered the first and most sensitive signs of compartment syndrome in an awake patient.
Clinical presentation according to forearm compartments:
- Pain with passive flexion of finger (MCP)
- Extension posture of fingers
- Weak MCP joint sensation
- Minimal to no sensory deficit
- Pain with passive extension of fingers/ wrist
- Tenderness over volar aspect of forearm
- Flexion posture of fingers
- Weak finger/wrist flexion
- Decreased sensation in median and ulnar nerve distribution
Mobile wad compartment
- Pain with passive wrist flexion/ elbow extension
- Weak wrist extension
- Decreased sensation in superficial radial nerve distribution
Diagnosis of compartment syndrome of forearm is typically made by clinical examination and compartment pressure measurement.
The clinical hallmarks have been the 5 Ps: pain out of proportion, pallor, paresthesias, paralysis, and pulselessness. A sixth symptom - pain with passive stretching, is now also included as part of the diagnostic signs. Pain out of proportion and pain with passive stretching of the fingers are considered the first and most sensitive signs of compartment syndrome in an awake patient. In contrast, pulselessness is a late-stage or even end-stage symptom and compartment syndrome has usually been present for some time before pulses are lost.
Surgical decompression and fasciotomy is done for acute forearm compartment syndrome to avoid irreversible muscle and nerve damage. Adequate decompression of the forearm requires fascial release of both the dorsal and volar compartments, with the volar compartment best released from the carpal tunnel distally to across the lacertus fibrosus proximally. Fasciotomy wounds must be assessed every 48 hours to 72 hours and additional soft tissue coverage procedures for wound closure are common.
Nonoperative management includes removal of tight bandages or splints, however, there should be an extremely low threshold to proceed with compartment pressure measurement or decompression if the patients do not rapidly improve.
Physical Therapy Management
Physiotherapy post fasciotomy includes scar tissue mobilization for the formed scar tissues and gentle stretching exercises a week after surgery. This is followed by range of motion exercises and manual therapy techniques to improve tissue flexibility and mobility of the surrounding fascia.
Physiotherapy following chronic exertional compartment syndrome (CECS) would involve cessation of causative activities or exercises. It is however pertinent to note that CECS of the forearm is rare with 95% of cases occurring in the lower leg. The forearm, foot and thigh are less affected. See Compartment Syndrome of the Lower Leg
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