Final answer:
A tri malleolar fracture is an ankle injury affecting both malleoli and the posterior surface of the tibia.
Step-by-step explanation:
The term for an ankle fracture that affects both the medial and lateral malleoli, as well as the posterior surface of the tibia, is a tri malleolar fracture. This type of fracture involves the medial malleolus of the tibia, the lateral malleolus of the fibula, and the posterior edge of the tibia. It is considered a severe injury and usually occurs due to high-impact trauma or awkward landings that may result in significant ankle distortion.