Besides bone deterioration, what are some other side effects from prolonged use of prednisone?

Many: Weight gain, adrenal insufficiency (body can't make cortisol, drug needs to be tapered not stopped suddenly), increased risk of infection, cataracts, high blood pressure, diabetes, other rare bone issue ("avascular necrosis"). Toxicity is often proportional to higher dose and longer duration.

Many: Thin skin, fragile blood vessels, avascular necrosis, increase risk of heart attacks, cushinoid syndrome, weight gain etc.