Hands and Feet: Metacarpals

Your digits have numbers. Your thumb is digit number one. Your index finger is digit number 2. Your middle finger is digit number 3. Your ring finger is digit number 4. Your pinky is digit number 5.  I just want to be sure that we are on the same page as to the numbering. Identifying which digit a phalanx or a metacarpal belongs to is essential.  Also essential is the designation of left and right.  If the palm bone attached to the index finger is broken, it means the metacarpal of the 2nd digit on the left hand is broken.  I find that students sometimes forget to remember that the thumb is digit #1. It is very common to mistakenly think that the index finger is digit #1.

When we talk about the hands and feet, it’s better to compare these two structures. This is similar to comparing the long bones rather than looking at them alone.   The bones of your ankle are called tarsalsSeven ankle bones forming the hindfoot and midfoot. and the bones of your foot are called the metatarsalsLong bones of the foot; numbered big toe (1) to pinky toe (5)..  Compare this with the wrist bones called carpalsEight small wrist bones arranged in two rows; allow wrist flexibility. and the bones of your palms called metacarpals.  Your toes have bones called phalanges (singular: phalanx).  Unfortunately, your the bones of your fingers are also called phalanges.

Metacarpal #1 on a hand is usually a give away for the thumb. It is noticeably shorter than the other metacarpals. The trick is to then determine is you are seeing the anteriorThe front of the body or toward the front when standing in the anatomical position. or the posterior of the hand. This is where the sesamoid bones come into use. These are round and tiny protrusions on the distal part of the 1st metacarpal. If they are visible, you are viewing the anterior side of the hand. If they are not present, you are viewing the posterior.

When studying, it is important to think of a patient standing in front of you in the anatomical positionA standard reference position where the body stands upright, facing forward, with arms at the sides. It doesn’t matter what direction the picture is oriented, you need to put that into the anatomical position. If you know your patient, it doesn’t matter which way the picture points.