Repost of my old thread
Head shape classification
Anatomical terms for the three types of the head shapes (that we know as, Long oval, intermediate, and round)
Dolichocephalic (long head : what we call “long oval” head)
Brachycephalic (short head : what we call “ round head”)
The head shapes are classified by
Cephalic Index = x/y × 100
(CI = (bipareital diameter or BPD, side to side measurement) / (occipitofrontal diameter or OFD, front to back measurement) ) × 100
click on the picture to see larger image
[/url]Hot spot 18, on Flickr
CI < 75 (female) 75.9 (male) is Dolichocephalic
CI 75 to 83 (female) , 76 to 81 (male) is Mesocephalic
CI > 83 (female), 81.1 (male) is Brachycephalic
Note : There’s a difference between male and female skull. That’s why the numbers are different for male and female.
What matters for helmet fitment are
Smooth, more vertical frontal bone (forehead) on female skull
Male skull has more angled (tilted back) forehead
Rounded chin (female skull) vs Square chin (Male skull)
The more blocky and massive cranial mass on male skull vs rounder and tapering at the top female skull
Male skull have a deeper cranial structure
(I should probably explain the difference between caucasoid vs mongoloid skull shape , but let me keep on explaining about round head hot spot problem (pain on temple area) for now.)
(There’s also CRANIAL INDEX, which is essentially the same thing except for the fact that it uses the measurement taken from the skull.
For the people who deal with live human’s head (such as helmet manufacturers), Cephalic Index (which takes flesh and skin in account) is the one that matters.
For the people who deal with the skull (such as forensic artist), Cranial Index (which takes shrinkage of the dried bone in account) is the one to use.)
Now, this Cephalic Index would have been really useful if the helmet manufacturers had used this, to indicate the internal shape of their helmets.