Neck problem

Looking for some advice about people who have neck problems and cycle, i have damage to the c7 facet joint and after 15 years it seems will no longer allow me to crane my neck when riding my mountain bike however i can ride my hybrid bike a trek navigator 300 due to the more upright position but looking to put a longer stem on my specialized hardrock mountain bike so i can still ride it, anyone else got this problem with there neck? And how did you overcome it?