There are some people who have very flat faces. Their cheek bones are very sunken. There are several ways of fixing the flatness:
Fat injection. However, this needs to be done a number of times to get to the point of satisfaction. Each repeat procedure needs to wait three months for the swelling to subside completely before the next episode.
The second way is to put in silicone (or other material) implants under the skin over the cheek bones. The possible complication of this procedure is infection and extrusion of the implant.
The third method is using bone or cartilage from a rib of the chest to add to the cheek bone. Using your own tissue has less danger of infection but requires another operation on the chest to obtain the needed piece of rib.
The picture shows the lady with silicone implants in her cheeks. She looks like a completely different person.