Struthers' ligament is a feature of human anatomy consisting of a band of connective tissue at the medial aspect of the distal

humerus The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a roun ...

. It courses from the supracondylar process of the humerus (also known as ''avian spur'') to the medial humeral epicondyle. It is not a constant ligament, and can be acquired or

congenital A birth defect, also known as a congenital disorder, is an abnormal condition that is present at birth regardless of its cause. Birth defects may result in disabilities that may be physical, intellectual, or developmental. The disabilities can ...

. The structure was highlighted by John Struthers, who discussed the feature's evolutionary significance with

Charles Darwin Charles Robert Darwin ( ; 12 February 1809 – 19 April 1882) was an English naturalist, geologist, and biologist, widely known for his contributions to evolutionary biology. His proposition that all species of life have descended fr ...

. Struthers originally reported that the ligament usually arose at a position 3.2 to 6.4 cm from the medial condyle, being 1.2 to 1.9 cm in length, and nearer to the anterior than the medial border of the humerus. The clinical significance of this structure is due to the

median nerve The median nerve is a nerve in humans and other animals in the upper limb. It is one of the five main nerves originating from the brachial plexus. The median nerve originates from the lateral and medial cords of the brachial plexus, and has contr ...

and brachial artery which may pass underneath the "arch" formed by the process and ligament over the humeral body. Within this space the nerve may be compressed leading to supracondylar process syndrome. The ligament may also affect the

ulnar nerve In human anatomy, the ulnar nerve is a nerve that runs near the ulna bone. The ulnar collateral ligament of elbow joint is in relation with the ulnar nerve. The nerve is the largest in the human body unprotected by muscle or bone, so injury is ...

after an anterior transposition surgery, which is a commonly performed to manage patients with a

cubital tunnel syndrome Ulnar nerve entrapment is a condition where the ulnar nerve becomes physically trapped or pinched, resulting in pain, numbness, or weakness, primarily affecting the little finger and ring finger of the hand. Entrapment may occur at any point from ...

, a form of

ulnar nerve entrapment Ulnar nerve entrapment is a condition where the ulnar nerve becomes physically trapped or pinched, resulting in pain, numbness, or weakness, primarily affecting the little finger and ring finger of the hand. Entrapment may occur at any point from ...

. It is unlikely that the ulnar nerves are affected in patients without transposition surgeries.

Prevalence

The ligament is not always present, and there is some debate as to its prevalence. Struthers originally estimated that it was present in 1% of humans.

Historical significance

The structure was originally depicted by Tiedemann, and later by Knox in the early 19th century, but John Struthers was the first to draw attention to this structure in 1848 as a "peculiar process" that bore curious resemblance to anatomy that he had seen in cats. This observation was one of many that Struthers made in subsequent investigations of vestigial and rudimentary structures, and in sharing these observations with his contemporary, Charles Darwin, provided significant evidence for the theories of evolution.

took the ligament to mean that humans and other mammals had a

common ancestor Common descent is a concept in evolutionary biology applicable when one species is the ancestor of two or more species later in time. All living beings are in fact descendants of a unique ancestor commonly referred to as the last universal comm ...

, and used Struthers' work as evidence in Chapter 1 of his ''

Descent of Man ''The Descent of Man, and Selection in Relation to Sex'' is a book by English naturalist Charles Darwin, first published in 1871, which applies evolutionary theory to human evolution, and details his theory of sexual selection, a form of biolo ...

'' (1871). Struthers went on to create a museum of Comparative Anatomy filled with zoological specimens to illustrate Darwin's theory of common descent.

References

{{Use dmy dates, date=April 2017 Ligaments of the upper limb Anatomical variations