How to speed up fracture healing of tibia and fibula?

You can't: Unfortunately, nothing you can do to speed it up. I would suggest that you take enough calcium and vitamin d through your diet (well balanced diet), follow the instructions given to you and wait patiently.

Ultrasound: Tibial shaft fracture are slow healers. The average time to healing in a simple tibia fracture is about 4.5 months. There is one study that suggests applying a medical device that emits pulses of ultrasound waves to the bone for twenty minutes a day can decrease the healing time approximately by three weeks. You can argue if this is a benefit or not in a slow healing fracture.