Identifying the Metacarpals in Three Easy Steps

This week I have come to three important realizations.

1. I am terrible at drawing the bones of the hand. I can spend ages working feverishly on intricate drawings of articular surfaces, and the finished product still basically comes out looking like this:

2. If you are, hypothetically, rushing around your apartment in a panic because the professional development workshop you signed up for is on February 4th, not at 4 PM as you initially gathered from the email, it is always best to double-check that the lid of your coffee thermos is screwed tightly onto its body, otherwise the last-minute, high-speed grab to transfer your caffeinated beverage to your bag might result in the majestic and unanticipated release of a breathtaking cascade of coffee all over your kitchen table;

3. Soaking white paper in coffee can really lend it an antiquated, old-timey finish that seems deliberate.

Without further ado, on to learning how to identify the metacarpals. Metacarpals are only likely to be confused with metatarsals, but their shafts are stout, rather than slim and straight like metacarpal shafts. Metacarpals also have rounder heads than metatarsals. Metacarpals are basically the corgis to the metatarsals’ greyhounds (and if anyone expresses any interest, I can write another post that’s more explicit about differentiating between the two).

Once you know you have a metacarpal (MC), the process for identifying which one you’ve got is fairly straightforward. The reason it’s possible to ID an MC in only three steps is because they can be divided into three distinct groups: Lateral (MC1), Middle( MC2-3), and Medial (MC4-5). Once you’ve got the group right, all you need to do is figure out which of the pair you have (and if you’ve got the lateral group, you’re golden). The names of the groups refer to the positions of the metacarpals when the hand is in Standard Anatomical Position (SAP). All images shown are sketches of right metacarpals, and directions refer to the hand in SAP.

STEP 1: Familiarize yourself with the features of the metacarpals
Unfortunately, the first step is most complicated. To be able to side a metacarpal quickly, you need to have a good understanding of the form of the shafts, as well as the proximal and distal ends.

STEP 2. Identify whether your bone is from the lateral, middle or medial group
Use your enhanced understanding of the features of each different portion of the metacarpal to make a decision about which group your bone should go in.

STEP 3. Identify which member of the group you have.

The easiest way to do this is to examine the proximal and distal ends. In my experience, the distal ends of the metacarpals tend to be more variable in their appearance and harder to differentiate, though I do have some tips if that is the only portion of the bone you’re working with. I find the distal articular surfaces of the bones to be most diagnostic, as each of the MCs has a fairly unique distal end.

As always, I’ve compiled a pdf of my tips below. It includes an extra blank page with my coffee-dyed sketches unlabelled, so you can jot down any more tricks you come up with when working with the metacarpals on your own.

How to Identify the Metacarpals in 3 Easy Steps

References:
White, T.D. 2000. Human Osteology. 2nd Edition. Academic Press, San Diego.
Credit is also due to my Bone Clones magnetic hand, which I spent several hours manipulating (and several minutes cleaning coffee off of) in order to produce this post.

Image Credits: Turkey handprint found here. Coffee spilling image found here. Old-timey photo found here. Corgi running found here, greyhound running found here. Coconut Octopus found here. Face of the moon found here, Everest peak found here, human high five here, ursine high five here, sad,repellent blobfish found here.