October 15th, 2018

Injury-to-order: hand injury that would allow someone to use a knife but not a gun?

*dusts off LJ account*

Hi all! I need some help puzzling out an inconsistent canon injury for fic.

Setting: Modern-day (urban), character is in a street gang and may have limited access to medical care
Scenario: Man, late teens-early 20s has his fingers injured in a knife fight. The moment itself is a discretion shot, but he's shown in canon to have a thick scar spanning the back of his hand between the base and middle knuckles. He's able to make a fist and use a knife with some dexterity, but supposedly can't squeeze a trigger to use a gun. Most of my searches brought me either a tendon injury or having the digits cut off/reattached completely, but I think he has too much movement for the latter...? Have googled various combinations of "tendon injury", "tendon injury and gun recoil", "extensor tendon knife injury", but all I seem to find are emergency medicine instructionals and vague forum posts.

Can anyone think of an injury that would fit the bill?

He needs to not be able to squeeze a trigger (also, please tell me why -- would there be a problem with recoil, or would the pressure be too much?). Maybe a botched treatment/surgery is the way to go?

Thank you so much.