Hip hip hooray: Orienting and identifying features of the os coxae

One of the ranges in my museum is decorated with a number of different osteological puns, and every time I walk past their on point door makes me jealous.  I’ve always been particularly envious of the “Hip Hip Hooray” slogan, since I have a close friend who studies the bony pelvis in fossil hominins.

Unfortunately, I think few novice osteologists share my positive reaction to the pelvis. Though orienting the ossa coxae and identifying features of the bony pelvis seems intuitive after a few years of experience with osteology, in the beginning this is a deplorably tricky anatomical region to master.

1.  First, the dimensions of the os coxae are tough to break down into an anterior/posterior or medial/lateral surface because of the distinctive orientation of features like the pubic symphyseal face and the ischial tuberosity.
2. Second, these bones are particularly difficult for beginner osteologists to orient. In contrast to the relatively simple “proximal end – shaft – distal end” structure of the long bones, the pelvis expands in multiple directions, making it seem impossible to decipher which end is up.
3. Third, there’s no real visible reference point on the human body to double-check your orientation. With regions like the mandible or the bones of the hand, you can use the proportions and appearance of your own body, but with the pelvis, no such luck – it’s buried in too much soft tissue.

Keeping all of these difficulties in mind, this post provides a series of tips and visualization tricks that will allow novice osteologists to familiarize themselves with the os coxae and learn how to orient isolated hip bones and identify specific features with ease. As a terminological note, a single hip bone is referred to as an os coxae or innominate bone, while more than one are pluralized as ossa coxae or innominate bones. All tips are available as a pdf at the end of the post.

PDF: Bone Broke Guide to Orienting and Identifying Features of the Os Coxae

In conclusion, HAPPY BIRTHDAY CAROLINE VANSICKLE!!!

Image credits: Hip Hip hooray image found here. Picasso photo found here. Colored pelvic girdle from Teach Me Anatomy, found here. Mouse lemur photo found here. Alien image found here. Pacman found here. Croissant found here. Delicate arch photo found here. Pachycephalosaurus head by Eloy Manzanero, found here. Kidney bean photo found here. Thumb found here. Stone steps found here. Bread dough found here. 90˚ angle found here. Fan found here. All images of the left os coxae are photographs of a Bone Clones European Male innominate.

References: I double checked my feature names and orientation in HBM and aging in the JS.

Scheuer, Louise, and Sue Black. 2004. The Juvenile Skeleton. Elsevier, Academic Press: Amsterdam.

White, T. D. and P.A. Folkens. (2005) The Human Bone Manual. Elsevier, Academic Press: Amsterdam.