Impotence is a harsh term. We tend to use the term erectile dysfunction.
Erectile dysfunction is the term used if the nerves responsible for erection are preserved.
Impotence is when these same nerves are cut. The nerves responsible for an orgasm are not the same as those responsible for an erection. With surgery, orgasms tend not to be a problem. The strength of the erection tends to be a problem. You do not need an erection to have an orgasm.