This updated guideline on progesterone-only implants is from the FSRH. There a few points of interest. Some just clarify old advice, others are completely new. I’ve listed the most useful bits:
Replacing the implant. If the implant is replaced within 3 yrs of insertion, there is no need for extra precautions as it is rare for ovulation to occur within 7d of its removal.
Dysmenorrhoea. The implant may improve dysmenorrhoea. In endometriosis, there are some small studies that suggest it may be helpful, but its use is not included in current guidelines.