Exploring the quadrilateral space: Clinical anatomy, pathology, and imaging insights

Quadrilateral Space Syndrome (QSS) is a rare clinical entity characterised by neurovascular compression within the quadrilateral space, a confined anatomical region bounded by the teres minor, teres major, long head of the triceps brachii, and the surgical neck of the humerus. The syndrome primarily affects the axillary nerve and posterior circumflex humeral artery (PCHA), presenting with nonspecific symptoms such as shoulder pain, paresthesia, and muscle weakness. Imaging plays a pivotal role in diagnosing QSS, with magnetic resonance imaging (MRI) serving as the gold standard. Ultrasound complements MRI by dynamically assessing neurovascular structures and detecting vascular compromise using Doppler imaging. Other imaging modalities, including radiography and computed tomography (CT), are valuable for identifying bony abnormalities or associated space-occupying lesions like osteochondromas or bone tumours. Management of QSS involves a stepwise approach. Conservative treatments, such as physical therapy and ultrasound-guided steroid injections, are first-line interventions aimed at alleviating symptoms and addressing contributing factors. Surgical decompression is reserved for refractory cases, particularly when fibrous bands, space-occupying lesions, or vascular complications such as thrombosis or aneurysms are identified. A thorough understanding of the anatomical and radiological features of QSS, combined with a tailored management strategy, is crucial for optimising outcomes in affected patients. This review aims to provide a comprehensive overview of the clinical anatomy, imaging findings, and management strategies for QSS.