this is not an ordinary case of a hip replacement, and I would only go with recommendations from the physical therapist who should be familiar with his history and should be able to advise you.
I agree with Daniel and Karin. But, what is cause of heel fracture. But primarily, hip stability is number 1. Hip abduction, hip extension, hip flexion (up to 90 degrees-make sure there are not hip precautions-no hip adduction past midline, no hip flexion past 90 and no internal rotation.
Otherwise hip strengthening. And based on his current status with the ankle, maybe seated exercises if he is non weight bearing on that side.
Hello Kathleen! Please aware that after a hip replacement, the gluteus medius is the primary muscle that needs strengthening, hip bridging, standing terminal knee extension, multi-directional leg raises, and some balance activies. Also be aware that your client should not perform any hip flexion >90*, hip adduction across the midline of the body, and hip internal rotation. Definitely want to stay away from doing a combined movement of these three joint actions.
Best of luck!