إِنِّي وَهَنَ الْعَظْمُ مِنِّي
My bones have indeed grown weak.
In Maryam 19:4, Zakariyyā describes weakness reaching the bones, an especially sturdy framework of the body. Mentioning this foundation makes the condition of advanced frailty vivid.
Inni adds emphasis; al-ʿaẓm is singular in form and can express the bodily structure generically. Do not turn every vivid detail into a separate figure without a defensible relation.