What exercises would be best for a 23-year-old male with excavates pectus? He has had two surgeries and is still concave. He has been consistently lifting for the past year, and his arms, shoulders and back are growing, but his chest has not responded.
As always, I will begin by recommending that you consult with your client's physician, preferably the one who oversaw his surgeries/treatments. The research I've done has suggested that in this condition, some individuals may have been born without certain portions of the pectoralis major (i.e., upper/mid-lower) all together. This would certainly make it difficult to make his chest "grow," as it is impossible to hypertrophy a muscle fiber that doesn't exist. So once again, it is VITAL to find out the particulars of your client's situation by speaking with his doctor.
Another item to consider in this and in any given "normal" human anatomy, the sternum/rib cage serves as an anatomical pulley for the pec, creating a force angle to "move" the shoulder girdle. Depending on the severity of your client's condition, this may also be hindering his growth.
My advice would be to be very careful here. Creating muscular imbalances anterior to posterior is a very likely possibility. "Hypertrophy" should certainly NOT be the only goal to work toward. Flexibility, postural alignment and stability will also be crucial in this case due to the client's pre-exposure to kinetic chain dysfunction. If the doctor has given the OK to train, than I would recommend referring your client to a specialist.