6 months seems to be standard for surgery in getting back to tennis. One of my hitting buddies had surgery twice on his shoulder and started playing again after six months both times. The second time was due to a construction accident - not tennis-related.
Any chance that they could replace the missing cartilage with lab-grown or synthetic?
4 x IG Prestige MP, 70 cm, 376 grams, 386 SW, ALU Power @50