Here’s an example of an orthotic that doesn’t fit properly in the shoe. An orthotic shouldn’t push the sides of your shoes and heels apart as seen in this right shoe.
What an orthotic should do, is easily fit into the back and arch of your shoe. Notice how the heel of the shoe with the orthotic in it is round in shape, whereas the shoe without the orthotic, is much tighter in the back of the heel?
Custom orthotics should not cause your heels to slip or push out the sides of your shoes. Since different types of orthotics can be made for all of your different types of shoes (heels vs. flats vs. running shoes), you should ask your podiatrist about getting multiple pairs of orthotics if you wear lots of different shoes.