Scapula retraction and protraction

[sameeralord]

I hope this is the right place to put it.

Anyway when I checked wikipedia it says

Protraction is the movement of an anatomical part of the body forward (anteriorly)

However in the scapula protraction is movement to left and retraction to the right. It is not forward bending. Then I checked some youtube videos and they do the test like wiki. I'm confused!

Thanks

 

[Moonbear]

No, if that's what wiki is telling you, then wiki is wrong (not the first time). Think of retraction of the scapula as trying to pull your shoulder blades more posteriorly. Protraction is in a more anterior direction. It's hard to demonstrate these movements in a normal person since the muscles controlling these movements work antagonistically to maintain the scapula in its correct, stable position.

Do a search for the condition "winged scapula" and you will see an example of a retracted scapula (this occurs when the long thoracic nerve supplying the serratus anterior muscle is damaged).

 

[sameeralord]

Thanks Moonbear you seem to be very helpful in these type of questions. I checked the winged scapula and now I get it. So retraction is basically going posterioly and abduction of the scapula. When I read about winged scapula I understood that serratus anterior protracts the scapula. So when the nerve for this muscle is damaged why does the opposite reaction (retraction) occur. I know this is some simple logic but it didn't click for me yet. Thank you!

 

[Moonbear]

Retraction is NOT abduction. The scapula can't abduct, the arm does. Abduction is generally a lateral motion increasing the angle of a limb from the trunk.

The reason the scapula retracts when the nerve to the serratus anterior is damaged is that the serratus anterior doesn't contract to protract it. Instead, the other muscles attached to the posterior side of the scapula are functioning unopposed, such as the rhomboid major and minor. Stability of body parts and joints is maintained by groups of muscles working in opposition to one another. If you have a loss of function of one, you have to think about what the others are doing.

 

[Proton Soup]

the easiest way i can think of to demonstrate protraction/retraction is to get in the top of the pushup position, with elbows locked. now, let your torso relax and fall to the floor, then push up your torso (remember, elbows are locked, only the torso goes up and down). if you're not strong enough for that, or it seems awkward, lean into a wall with elbows locked and do the same movement, but pulling/pushing your torso to/from the wall instead of floor.

 

[Moonbear]

Great example, Proton Soup. And, incidentally, that last part you described, of putting your arms up and pushing against a wall is precisely the test used for identifying "winged scapula" that I mentioned above. It isolates that movement to make it very evident if there is an injury to the long thoracic nerve.

 

[Proton Soup]

now if i could only remember innervations longer than a week or two :uhh:

actually, clinical tests would probably go a long way towards accomplishing that...