modifier 51 means you do not expect to collect 100% of the normal amount from the carrier. Bit if the carrier thinks that the multiple procedure(s) reduced the value of the services, that is when they will apply the reduction, and even if you do not apply the modifier, they will append it and they will pay 50% of their normal amount. In the case of the injections, normally the doctor's work effort was not reduced, so it probably would not apply. Bill the codes without the modifier, and if the carrier reduces the payment, write an appeal stating that the doctors' effort was not reduced and the reduction was unfair. (Before writing the appeal, make sure the doctor approves it!)
jm