Surgery should be done in Level 4 whatever the age is, its the time not to think of the life of the implant but to think of the quality of life that girl. but it last almost 25 years or more.after replacement its not life threatening.

Avn level 4 mandates total hip replacement at all age groups. The choice of implant may vary from patient age group and surgeon preference. However you should discuss with surgeon and plan the future accordingly. For eg hip replacement patient might 've some difficulties in routine life. Which you need to discuss prior with the surgeon. As far life of implant is concerned, don't worry. In Indian patient they can last a lifetime.

You should definitely go for surgery. It would help to improve the quality of life.

AVN can be lethal if left untreated. Now since it has been detected , my friend dont think much about will the replacement last or not just go for the surgery. Only thing that you need to think about is , What make would be the prosthesis . generally speaking if the bones are healthy and a check on weight along with some precautions post surgery topped with a healthy diet plan the hip replacement prosthesis can easily do roughly 25 years it won't be life threatening after 10-15 years, and it is repeatable depending upon Bone mineral density at the time of resurgery.

She does not have any danger to life because if the surgery but the surgery ie the implants lasts from 15-20 years and require to he changed again. It is a matter of improving quality of life.