Location/type of fx. Oi has several sub forms and the type & location of their fx are often used to help classify their subgroup. That said, the type and pattern of intentional trauma is recognizable. Breaks that show symetrical shoulder fx from shaking of a child lifted by his upper arms/ circumferential skull fx, etc. I believe a sub-board of pediatrics recognises those with the added training to sort these out.
Yes and No. Well, oi is a disorder of irregular collagen which leads to weaker bones and easy fractures. Most kids with oi present with multiple fractures early in life. Oi does not cause brain injury, or really contribute to significant intracranial bleeding or brain injury and does not cause significant retinal hemorrhaging. So, no, oi is not really similar at all to abusive head trauma except fractures.