My Question Is About Implanon/nexplanon. I Want To Know If

My question is about implanon/nexplanon. I want to know if there is any particular reason why it can only be inserted in the arm (as opposed to the leg or elsewhere). I'm guessing that clinical trials only included arm placement, so that's the only place approved, but is there any reason it couldn't go elsewhere, theoretically? Is there any chance its usage could be expanded in the future? Because of the possibility of nerve damage (though I DO know it's very low), I cannot accept placement in the arms because my livelihood requires very fine motor control in the hands.