Complex fractures with multiple fragments often require external fixation. You didn’t mention whether it was the femur (thigh bone) or tibia (lower leg bone).
Either one can have a long, spiral fracture of the diaphysis (shaft). This can require pins to hold it in place while healing takes place. External fixation also allows for earlier weight bearing. And there are fewer problems with the bone fragments moving or dislocating. A short fracture line might not need plates, pins, or screws to hold it in place. Intramedullary nailing is another name for this type of treatment.
When fractures can be realigned without an incision, the procedure is called a closed reduction. When the leg must be opened to give the surgeon a direct view of what’s going on, then it’s called an open reduction. Sometimes fractures of the long bones can be treated with a tiny incision. The procedure is referred to as minimally invasive.
It’s not too late to request more information about your daughter’s fracture. If she is still in the hospital, ask the nurse in charge to explain what was done and why. Or request this information at your next follow-up visit with the surgeon.