I just had surgery to fix my tibial avulsion fracture. i cant do pt for 5 weeks (12 weeks total since break). how do i minimize the atrophy in my leg?

This is difficult: There aren't too many exercises you can do to avoid atrophy after surgery especially if you are limited in your activities (ie weight bearing vs non-weight bearing). The type of cast or splint you are in and type of surgery may also limit the activities you can do. If it is ok to do quad sets or straight leg raises with the splint or cast on, this can help prevent atrophy of the quadriceps.