Revisiting 35: the protuberant acromion

A few days back, an inquiry into a bodypart of personal interest to me: my 9/14/19 posting “Clavicular knobs”, in which these bony protuberances were illustrated on the body of a Scruff guy “Ricardo”. Ricardo’s photo cropped to focus on his shoulder handles:

(#1) Ricardo’s very visible clavicles, aka collar bones, terminating on either side in bony protrusions — an anatomical feature shared by my first male lover Danny and my husband-equivalent Jacques

I noted that clavicular knobs seemed to be very rare, even in lean-bodied men with very noticeable clavicles; and that Danny and I each believed we once knew a name for them but now we couldn’t recall it (or them).

First to arrive on Facebook with some nomenclatural clarity was Chuk Craig, who supplied the term acromion (Gk. ‘top of the shoulder’). Which led to the relevant joint, the AC, acromioclavicular, joint; to separated shoulders; and, in other directions, towards anatomical rarities (like protuberant acromia) and the psychology of perception and attention (if you’ve read my earlier posting, you’ve probaby been noticing clavicles a lot).

On the noun acromion, from OED3 (Dec. 2011) (in the context of Ricardo above, note the “robust, peg-like acromion” in the 1999 cite):

Etymology: < post-classical Latin acromion (1528 or earlier) and its etymon ancient Greek ἀκρώμιον (Hippocrates) < ἄκροacro– comb. form + ὦμος shoulder (see omo– comb. form) + -ιον, suffix forming nouns. Compare Middle French, French acromion (1534 in Rabelais).

Anatomy and Zoology. A bony process forming the lateral or distal end of the spine of the scapula, with which (in humans and certain other mammals) the clavicle articulates. Also attributive, esp. in acromion process. [1st cite in English 1578. Then:]

1653 T. Urquhart tr. F. Rabelais 1st Bk. Wks. xliii. 193 Then did the Monk with his staffe of the Crosse, give him such a sturdie thump and whirret betwixt his neck and shoulders, upon the Acromion bone, that he made him lose both sense and motion, and fall down stone dead at his horses feet.

1999 Nature 25 Mar. 328/2 This new taxon..has a robust, peg-like acromion and a low elevation on the spine that resembles the metacromion of Didelphis. [The noun metacromion in OED3 (Dec. 2011): Zoology. In some mammals: a process of the spine of the scapula [i.e. the shoulder blade] posterior to the acromion. [1st cite 1867]]

So Ricardo’s knobs are prominent or protuberant acromia, and we might say of them, “I admired his beautfully formed acromia”.

Etymological note: the acro– of acromion. From Michael Quinion’s affixes site on acr(o)- ‘a tip, height, or extremity’ [Greek akron, a tip or summit.]:

An acrobat (Greek bainein, to walk) is literally someone who walks on tiptoe; an acropolis (Greek polis, city) was a fortified part of an ancient Greek city, typically on a hill; an acronym (Greek onuma, name) is a word formed from the initial [‘top’] letters of a phrase.

In medicine, the acromion is the outward end of the spine of the shoulder blade. Medical conditions include acromegaly (Greek megas, great), abnormal growth of the extremities and face caused by excessive production of growth hormone, and acrophobia, extreme or irrational fear of heights.

[AZ: and in pidgin and creole studies in linguistics: acrolect vs. mesolect vs. basilect]

The rarity of Ricardo’s acromia. My search for images of prominent acromia — Ricardo’s acromia, as I will now call them, after Scruff-Man Ricardo as an archetype — was fruitless a couple of days ago, and a couple hours of searching through images of shrirtless / bare-chested men yesterday didn’t turn up any more. For a while I focused on images of athletes, especially football players (American football, rugby of all kinds, and soccer), for reasons that will become clear below. Eventually I realized that Ricardo’s acromia were unlikely to be visible in such men, because they would be concealed by the men’s massive shoulder musculature.

So I shifted my strategy to searching through shirtless twinks / teens etc. Tons of prominent clavicles amidst all the boysex, but none (that I found) with protuberant acromia.

If there’s a medical term for Ricardo’s acromia, I haven’t discovered it, despite searches on all sorts of possible descriptions and names, many of them floated in my discussion above.

In any case, I’ve been viewing it just as a rare variant (like the AB-negative blood type I mentioned in my previous posting), rather that as  some sort of pathology. However, there’s a possibility that some instances of Ricardo’s acromia are the consequence of injury.

Shoulder separation. From Misty, a reader of this blog:

the cause of the clavicle knob could be minor shoulder separation, at the joint where the clavicle and shoulder blade (acromion) meet. That joint is the AC [acromioclavicular] joint. I suppose the bone grows in to fill the gap with repeated reinjury. Perhaps your lovers were football players.

Before I get into the anatomical and medical stuff, just a note to scotch the idea that Danny and Jacques were football players, or athletes in any sort of contact sport. As young men, they were not, I believe, nearly as profoundly unathletic as I was — but no, not jocks. And I’m pretty sure neither of them ever had a separated shoulder.

However, real people do get separated shoulders, and they can be tremendously painful, requiring serious medical attention. From the Stack site on the condition:

(#2) Ouch on the right shoulder

The shoulder is an incredible joint. It’s capable of extreme ranges of motion that allow you to throw a ball, swing a bat or push off against an opponent with extreme force. But it’s also one of the most vulnerable joints in the body. It’s a common targets for tackles and bodychecks, and it’s one of the first areas of the body that hits the ground during a fall.

This makes the joint susceptible to shoulder separations. In fact, 50 percent of shoulder injuries in contact sports are separated shoulders, which, depending on the severity of the injury, can keep an athlete out of action for up to 12 weeks.

(Note: A shoulder separation is distinct from (and generally more serious than) a shoulder dislocation, an injury in which the humerus, the upper arm bone, pops out of the cup-shaped socket that’s part of the shoulder blade.)

Perception and attention. Along the way, Dennis Lewis responded on Facebook to my posting about (visible) clavicles and their acromia:

I hadn’t noticed until the skeletal diagram. I’ve never noticed. And now I can’t help but noticing. 😲

Dennis and others. Dozens, maybe hundreds, of people will, at least for a while, be attentive to clavicles and their properties, now that I’ve shown them features distinguishing different types; the distinctions have become salient for them, and might even stick with them for a long time — slightly sharpening their perceptions of human bodyparts. (The effect is well known in psychological studies of attention and its effects on perception.)

My response to Dennis:

Alas, that is the way of such things. You can go through life happily not noticing that some people have attached (rather than free) earlobes — there seems to be continuous variation here, but attached earlobes are definitely the minority variant — until someone points out to you that there are two kinds of earlobes (you don’t even have to have names for the types), and then you can’t help noticing.

No one pointed out attached vs. free earlobes to me until I was a teenager. (As a free-lober, I’m in the majority. There must have been atached-lobers in my circle of acquaintances, but I just didn’t notice.)

(#3) Attached on the left, free on the right

Not long thereafter, earlobes turned up in our biology textbook as an example of classic dominant vs. recessive Mendelian inheritance. This, as it turns out, was wishful thinking, though attached lobes are very much in the minority.

(I’m a solidly free-lobe guy, Ann Daingerfield (Zwicky) was as close to lobeless as you can get. Elizabeth Daingerfield Zwicky? She got one of each. Others have intermediately lobed ears. Genetics can be complicated.)

In any case, once I’d learned there was a distinction, I was inclined to notice it as a feature of human anatomy.


7 Responses to “Revisiting 35: the protuberant acromion”

  1. julianne taaffe Says:

    Attached. I always knew I was special. Also, I have never had wisdom teeth. Does that make me more highly evolved? I’d like to think so.

    • arnold zwicky Says:

      Didn’t know about wisdom teeth, but it turns out that agenesis (failure to develop in a fetus) is pretty common, though probably a minority thing. But complicated: more common in females than males; more common for maxillary (top) third molars than for mandibular (bottom) ones — yes, you can have anywhere from 0 to 4 third molars (or extras!); wildly variable in different populations.

  2. Carl Lindfors Says:

    I have protuberant acromia. Very noticeable and have had it since childhood. It used to be extremely noticeable when I was very skinny. I used to refuse to wear T-shirts after someone pointed out to me how weird it looked.

    Lifting weights has alleviated the problem but it will take some serious muscle and bulk to hide them completely.

    I wish I could have them shaved down.

  3. Tim perrin Says:

    I have them also never played any sports

  4. Kendrick Carrey Says:

    It seems I have them too. Always thought it was because I was too skinny. One of my exes even said it was a problem for them.

  5. Amy Says:

    Always self-conscious of mine. I lift weights to disguise them. I have always had them.

  6. Jinil Says:

    I have them too and I am skinny already 🙁 I think I have seen very few people having them!

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