In the existing literature on the rare reports of upper arm ACS, the following have all been reported as causes: limb compression , supracondylar fracture of the humerus in children , humeral shaft fracture , heroin injection poisoning , carbon monoxide poisoning , bicep muscle rupture [7, 8], triceps injury [15, 16], and severe bleeding secondary to venipuncture or thrombolytic treatment [17,18,19]. However, there were fewer reports of isolated anterior compartment syndrome, which were mostly caused by the injury of biceps [7,8,9] and secondary to drug toxicity [13, 18, 19] or fracture [11, 12]. We present a case of acute compartment syndrome of the isolated anterior compartment of the upper arm due to single brachial muscle injury after blunt trauma. To the best of our knowledge, this is the first report of this type of injury.
Only a few reports have detailed this [3,4,5,6]. However, there were fewer reports of isolated anterior compartment syndrome, which were mostly caused by the injury of biceps [7,8,9]. The present case report will discuss acute compartment syndrome of the isolated anterior compartment of the upper arm due to brachial muscle injury after blunt trauma in a 55-year-old man.
The injury mechanism of the presented case is rare. The force on the medial part of the upper arm only injured the brachial muscle (the deep part of the brachial muscle lies at the lower edge of the medial part of the forearm) and led to in internal hemorrhaging of the entire brachial muscle, which caused increased pressure in the compartment where the brachial muscle is located, ultimately resulting in a rare cause of upper arm compartment syndrome. In addition, the pathogenesis of the case is also very characteristic. In the early stage of the injury, no neuromuscular symptoms were found. The patient continued to engage in farm work for about 4 h after injury. However, the symptoms of the affected limbs gradually appeared and aggravated after the pressure of the upper arm fascia chamber increased. During the course of treatment, the patient was treated by splitting the extremely swollen brachial myomembrane, which also confirmed the diagnosis of single compartment syndrome in the anterior compartment of the upper right arm caused by simple brachial muscle injury.
The incidence of acute compartment syndrome in extremities is determined by its anatomical characteristics. Acute compartment syndrome is predominant in the forearm and lower leg due to the more abundant contents inside the compartments and the toughness of the interosseous and intercompartmental membranes . The upper arm contains a single bone (the humerus) and no interosseous membrane. The the upper arm is divided into two compartments through the medial and lateral interventricular membrane: the anterior compartment (containing biceps, brachialis, coracobrachialis) and the posterior compartment (containing triceps). The compartment is composed of the humerus, intermuscular fascia, and fascia, which has greater flexibility and expansion space. Therefore, the incidence of upper arm compartment syndrome is very low .
Timely, adequate, and complete decompression is the principal treatment that must be followed for upper arm compartment syndrome. Muscles can tolerate ischemia for 4 h, but functional changes may occur after 6 h, and damage is irreversible after 8 h . Once the presence of compartment syndrome of the upper arm is suspected, the reduction of tension should be carried out decisively. Any delay in diagnosis and treatment can have catastrophic consequences. Han  reported a case of upper arm compartment syndrome caused by blunt impact after fall, and followed by rhabdomyolysis, acute renal failure, ultimately resulting in the death of patient with intracerebral hemorrhage. Thomas  and Traub  described in detail the consequences of compartment syndrome, including permanent nerve damage, muscle necrosis, growth arrest, Volkmann muscle contracture, and even dry gangrene if not treated in time.
The key to successfully treating a upper arm compartment syndrome is early recognition. Abnormal pain may be the only symptom of early onset . Special vigilance should be exercised in children or patients with dull pain or sedation . In the diagnosis of compartment syndrome, physicians should be highly suspicious of compartment syndrome in patients with a history of related diseases if they have abnormal pain, high tension of the compartment, and passive traction pain. Compartment pressure measurements should not be relied upon , nor can the diagnosis be made until the limbs show late signs, such as motor palsy, paleness, or pulselessness .
Because of atypical injury mechanism and rare incidence, clinicians should fully recognize the fact that acute compartment syndrome can occur in the upper arm, rather than only the forearm and leg, and the increase of pressure in compartment caused by single brachial muscle is enough to cause compartment syndrome, therefore avoid serious consequences caused by missed diagnosis and misdiagnosis.