Why does a blunt trauma injury cause lacerations?

Question

My daughter banged her upper cheek/temple onto the top of a table (sigh). There was no swelling, and there was no sharp edges that she hit, so what caused the laceration that took four stitches to close it?

Answer 1

Good question, and intersting. I think you're looking for the evidence behind the question.

Crime scene analysis:
Bang
Hit
Table
No Swelling
No Sharp edge
Cheek
Skin

You mentioned 2x's hit and bang, then hard surface. Here is what happens in blunt trauma. A blunt, hard, non-pliable object (table) collides with the pliable, soft tissue of a young girl. Even with no sharp edges she is going to get damage. Could have been the height of the fall (fall from a long distance?), weight of the fall (did she catch herself on the way down?) the condition of the skin (is she very thin, if so she would have less padding). All of this comes into play, you are right most kids don't actually break their skin and require stitches, very often they don't even have ecchymosis.

In summary when soft tissue comes rec. trauma from a blunt object something's got to give.

Answer 2

The force of the blow catching the skin between the table and her facial bones would cause the skin to split.

Answer 3

the skin is only so strong, hit it hard enough and it will split creating a laceration like wound.