Written in Bone by Sue Black

Author:Sue Black
Language: eng
Format: epub
ISBN: 9781951627942
Publisher: Arcade
Published: 2021-05-13T00:00:00+00:00

PART III

THE LIMBS

Postcranial Appendicular Bones

6

The Pectoral Girdle

“Shoulder blades are where your wings were when you were an angel”

David Almond

Writer

There are two “girdles” in the human body. The word “girdle” is more commonly associated with women’s corsetry, but I gave up using such analogies with my students when references to my mother’s Playtex girdle and Cross-Your-Heart bra drew nothing but blank looks. Evidently I was showing my age.

Our upper bony girdle is the pectoral or shoulder girdle, which connects the bones of the arm (humeri) to the trunk and comprises paired clavicles (the collar bones) at the front and scapulae (shoulder blades) at the back. The lower one, the pelvic girdle, consists of the two hip bones, which form a junction between the sacrum at the back and the femora (thigh bones) of the lower limbs at the sides.

It is interesting that the pectoral girdle should contain both the bone that is the least likely, of all the bones in the body, to fracture—the scapula—and the one most prone to being broken: the clavicle. While all primates possess a collar bone, it is rudimentary in many mammals and absent altogether in the ungulates, which include a variety of animals from horses to pigs, and even the hippopotamus. Cats, for example, have very rudimentary clavicles, which is why they can squeeze through spaces that appear to be much too narrow to accommodate them.

In humans, the clavicle, as well as being a convenient location for muscle attachment, serves as a strut to keep our arms out to the sides of our body. In most quadrupedal animals, the forelimbs, positioned underneath the body, are used solely for locomotion, and as no dual function for the clavicle is required it does not need to be very large. Yet amazingly, the human clavicle isn’t really essential. We can have it taken out as long as the muscles can be stitched to each other. In the past, some jockeys used to have their clavicles surgically removed as a preventative measure. Since it was the bone most often broken in falls from their horses, there was a school of thought that maintained it was better to do without it than to risk the perils of a fracture.

And there is no question that a broken clavicle can be life-threatening. The bone is shaped like an elongated “S’ and a fracture will occur at the weakest point, the major bend in the lateral third. Unfortunately, that lies directly over the subclavian artery and vein, which are very large, and makes them susceptible to being ruptured or pierced by sharp shards of broken bone.

Sir Robert Peel, who served twice as Britain’s prime minister between 1834 and 1846 and is regarded as the father of modern policing (hence the antiquated nickname “peeler,” and the more enduring “bobby,” for a police officer), met his end as a result of a fractured collar bone. He had acquired a new horse, a hunter, which had a bit of a reputation as a kicker. Sir Robert

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