Healed from a torn left pectoral muscle - Can fat be injected for strength gains?

I am a powerlifter on an international level. I tore my left pectoral severly a few years ago, but it healed nicely. It did become somewhat disfigured with some loose skin underneath the torn area. I will now have this fixed by injecting fat into the torn area (prime grafting). The doctor said I could also inject fat into my shoulders, biceps, triceps etc. I don't need this for aesthetic purposes as these muscles are already huge. But I have been told that the prime grafting method will also increase strength and protect the muscles from wear and tear. This seems odd to me. I am afraid that my worn left shoulder - which is already sore and stiff - will get worse from "ballooning" it up with mere fat. Stem cells FROM fat is another matter. But I don't know if this is the idea