Learn Turkish: Ameliyattan önce halama uğramam lazımdı. - I had to drop by my aunt before the surgery.

This sentence uses the past necessity structure you are currently learning. First, we take the verb uğra (drop by) and add the short verbal noun ending -ma, plus the possessive -m (my). This creates uğramam (my dropping by). Then, we add lazımdı (was necessary), which is lazım plus the past tense suffix -dı. Literally, it means "my dropping by was necessary."

Why does halam (my aunt) have an extra -a at the end to make halama?

The verb uğramak (to drop by / stop by) always requires the dative case (-a or -e) because you are directing your action towards a place or person. So, halam (my aunt) becomes halama (to my aunt).

Can I use hala for my mother's sister too?

No, Turkish has specific words for relatives on each side of the family. hala is strictly your father's sister (paternal aunt). If you were visiting your mother's sister, you would use teyze and say teyzeme uğramam lazımdı.

Why is it ameliyattan önce instead of just ameliyat önce?