Anatomy, Shoulder and Upper Limb, Arm Quadrangular Space

Excerpt

The quadrangular (or quadrilateral) space is named because of the shape of its anatomic boundaries. Located along the posterolateral shoulder, the quadrangular space serves as a passageway for the axillary nerve and posterior humeral circumflex artery. Quadrangular (or quadrilateral) space syndrome can occur secondary to various compressive pathologies that cause axillary nerve compression and/or posterior humeral circumflex artery compression.

Although such pathologies are rare, quadrangular space syndrome has a known predilection for subgroups of athletic populations. These athletes can often suffer misdiagnosis or are clinically under-appreciated. Thus, clinicians should maintain a heightened clinical suspicion for quadrangular space syndrome in patients 20 to 40 years of age presenting with a history of current contact or overhead athletic performance (eg, baseball pitchers, volleyball players, swimmers, baseball players, etc), or overhead laborers secondary to repetitive stress mechanics on the shoulder such as electricians and painters.

A significant percentage of the patients visiting primary care physicians do so because of shoulder pain and debility. Quadrangular space syndrome is relatively rare but important in the etiology of shoulder pain.

The condition commonly presents with posterolateral shoulder pain that worsens with abduction and external rotation of the arm at the shoulder.

Quadrangular space syndrome is easily confused with rotator cuff tears and frozen shoulder syndrome. This condition can also be confused with thoracic outlet syndrome, cervical radiculopathy, and suprascapular nerve entrapment syndrome.

The quadrangular space syndrome involves compression of the axillary nerve and posterior humeral circumflex artery due to fibrous bands, trauma, and hypertrophy of adjacent muscle.