One of my implants never formed a capsule, how rare is this & could it form completely now?

Thanks for your question. All breast implants will form a capsule as this is what happens when any foreign material (in this case the breast implant) is inserted into your body. If your wounds have now healed and you still have your implant, then yes a capsule will form around it. The incision opening up would not be due to the lack of capsule formation, but for another reason such as poor quality soft tissues, infection, or implant dimensions. Best of luck with your ongoing care.

Dear Bright905055,
you probably mean soft tissue pocket that is created to hold the implant. Sometimes if the soft tissue is poor or implant is too big, it can cause this kind of problem. You should follow your surgeon's instructions.
Daniel Barrett, MDCertified, American Board of Plastic SurgeryMember, American Society of Plastic SurgeryMember, American Society of Aesthetic Plastic Surgery

It is possible that the capsule was never able to fully form. If the implant was exposed due to the incision opening it could be contaminated. Keep a close eye for signs and symptoms of infection. If you have thin skin or large implants you may benefit from placement of mesh to give support to the tissues.