Binary subtraction with numbers in 2’s complement

How can i perform binary subtraction of two numbers that are already in 2’s complement? I have to subtract 01010011 from 10100110,both numbers are in 2’s complement. I know that 10100110 is -90,and 01010011 is 83,so the result should be -173. So if i use 8 bits that means that there’s overflow. But i don’t get how can i perform the subtraction when both the numbers are in 2’s complement. If i just perform the subtraction i get the same number 01010011. How do i show the result and that there’s overflow?