What’s a bimalleolar fracture?

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A bimalleolar fracture is a type of ankle injury in which the bones that form the top portion of the joint break in two places at the same time. Also known as a Pott fracture after an 18th-century physician who published an article about the injury after sustaining it himself, a bimalleolar fracture involves the lateral and medial malleoli, the pair of bony projections that form the rounded bumps felt on either side of the ankle. This injury occurs when a powerful lateral force rolls the ball of the foot outward in a motion known as eversion and at the same time rotates the foot at the ankle in a motion known as external rotation. A forceful enough movement can cause both the medial malleolus, a bump on the inside of the tibia bone in the lower leg, and the lateral malleolus, a similar prominence on the outside of the fibula bone next to it, to rip apart. respective bones.

The bones of the ankle joint are the parallel bones of the tibia and fibula of the shinbone and the talus of the hindfoot, which sits atop the calcaneus or heel bone. These bones are connected to each other by several ligaments, including the greater deltoid ligament which connects the medial malleolus of the tibia along the inside of the ankle to the underlying talus, and the anterior and posterior talofibular ligaments which connect the lateral malleolus of the fibula to the talus along the outside of the ankle. When excessive forces are placed on the joint, as in an athlete colliding with another athlete in such a way that the ankle rotates abruptly in one direction, damage can occur to one or more of these ligaments and/or to the bones to which they are attached. they attack.

In the case of a bimalleolar fracture, the blow comes from the outside of the ankle, contacting the lateral malleolus in a horizontal direction. This causes the foot to move and externally rotate so powerfully that the deltoid ligament along the inside of the ankle is overstretched to the point of tearing the medial malleolus to which it attaches from the body of the tibia. Simply rolling the ankle is typically not an injury strong enough to damage the bone. Normally, the ligament itself is sprained or torn, although it most often affects the talofibular ligaments on the outside of the ankle rather than the tough deltoid ligament.

As the deltoid ligament pulls down on the medial malleolus, the underlying talus bone, to which the other end of the ligament attaches, abruptly moves laterally. This action of the talus tears the lateral malleolus when the talus contacts the distal or inferior end of the fibula or causes the fibula bone to snap into the underside of its shaft. In both cases, the injury can be termed a bimalleolar fracture, even if both malleoli are unaffected. To fix a bimalleolar fracture, surgeons realign the bones and reattach the broken pieces using surgical screws or other implants.

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