Let´s see if any vets in the house can shed some light in here.
I have to make a skeletal setup for a 3D cat, it has to work as closely as the real thing as possible. The problem is that I haven´t figured out how the front legs articulate at the torso.
One funny thing I´ve learned while doing research is that cats don´t have clavices (right? :dubious: ), so I´m a bit baffled at what the shoulder blades are attached.
So far I´m thinking that maybe the whole shoulder is not actually articulated but rather a floating attachment, is that correct? If so, how does it work?
That’s exactly correct. The shoulder blade articulates with the humerus, but not with any other part of the skeleton. The shoulder is held in place purely by muscles attaching to the spine and sternum.
Cats have clavicles, but they are rudimentary and do not articulate with other bones. Actually, primates are somewhat unusual among mammals in retaining the clavicle, a primitive feature. Most carnivores and ungulates lack clavicles.
Couldn’t describe it any better than Colibri has. I would only say that the differences between the cat and dog anatomy allows the cat to supinate (as when they play with a toy) while the dog cannot.
As mentioned, that is correct. You can slice off a cat’s front leg, complete with shoulder blade, and never have to cut through ligaments (note: I’ve only done this when doing dissections). The lack of solid shoulder girdle attachment is part of what makes cats so agile (and why their scapulae stick out so far when they are crouching).
I’ve done just that therapeutically. That said, if possible when doing feline forelimb amputations I like to leave a little bit of the proximal humerus, covered with a muscle sling. When using the litter box, feline amputees will “dig” at the air with their stump. I have had pet owners tell me that they think the cat “feels good” about being able to do this.
I’ve heard cat humerus articulation described like this: there’s a sling running from one shoulderblade to the other, under the ribcage. The ribcage rests in the sling. Since the sling is loose and nicely lubricated, you can usually see the shoulderblades alternately pop up on the cat’s back as he walks. I read also that this allows cats to walk on extremely narrow paths, though I don’t see exactly what one thing has to do with the other.
It’s not direct, but the absence of a clavicle or firm connection between the leg and the rest of the skeleton means that cats are very compressible side to side, and can squeeze their flexible shoulders through very narrow openings.
Aha, verrrry interesting; specially the description by Napier.
So, I assume that the pivot point of the humerus moves up and down as the cat walks, unlike, for example the hip articulation that remains fixed (although, of course, it moves with the hip) So the skeletal setup I have to build should be able to move the shoulder pivot around the torax a little. It is to cry…
Now if anyone knows of any x-ray footage of a cat walking that would be just peachy to understand how things move.
Yes, the position of the articulation between the scapula and humerus is not fixed in relation to the spine, unlike the articulation between the pelvis and femur. The shoulder joint can move to some degree relative to the spine, though of course this is limited by the muscles.
I’ve done just that therapeutically. That said, if possible when doing feline forelimb amputations I like to leave a little bit of the proximal humerus, covered with a muscle sling. When using the litter box, feline amputees will “dig” at the air with their stump. I have had pet owners tell me that they think the cat “feels good” about being able to do this.
