Supracondylar spur

A supracondylar spur, supracondylar process, supratrochlear spur, or avian spur of the distal anteromedial humeral cortex is an anatomical variant present in ~1% ^1,2 of the population. 

Gross anatomy

The supracondylar spur is typically located on the anteromedial humeral cortex, 5 cm proximal to and pointing towards the medial epicondyle of the humerus ³. 

This structure is often considered a vestigial structure, as a supracondylar canal (or foramen), can be found as a normal structure in many more primitive mammals, such as in felines ¹.

The ligament of Struthers may be present and join the tip of this process with the medial epicondyle ¹, forming a supracondylar canal through which the median nerve and brachial artery pass ². This ligament is thought to represent the vestigial third head of coracobrachialis. The two main heads surround the musculocutaneous nerve and then fuse in human fetuses, explaining why the nerve passes through the muscle ⁴.

Clinical presentation

Most patients are asymptomatic although it should be considered if patients present with symptoms of median nerve compression and there is no pathology on imaging of the carpal tunnel.

This can also result in compression of the brachial artery. 

Radiographic features

Plain radiograph

Typically, it is seen as a small bony spur projecting anteromedially from the humeral metadiaphysis towards the elbow joint.

Treatment and prognosis

Complications

• supracondylar process syndrome: associated neuropathy of the median nerve ¹
• brachial artery compression

Differential diagnosis

• osteochondroma: usually points away from the joint