CT Scan – Ankle

About an ankle CT scan

The ankle joint is where the two bones of the lower leg, the tibia and fibula, meet the talus bone of the foot. Below it, the talus joins the heel bone (calcaneus) at the subtalar joint. A CT (computed tomography) scan uses X-rays and a computer to make detailed cross-section pictures of these bones, which can be turned into 3D images. CT shows bone in more detail than any other scan.

The most common reason for an ankle CT is a fracture. Many ankle fractures are diagnosed and treated using X-rays alone, but some, especially those involving the back of the tibia (posterior malleolus), the joint surface or the talus and heel bone, are complex or hard to see. A CT shows exactly where the breaks are and how the pieces sit, which can change how the fracture is classified and helps surgeons plan an operation. It is also used to check how a fracture is healing.

A CT may also be used to look at:

• arthritis and bone spurs, including before joint fusion or replacement
• osteochondral lesions, where a piece of cartilage and the bone beneath it is damaged
• tarsal coalition, a bony or fibrous bridge between two foot bones that can cause stiffness and pain, often first noticed in teenagers
• loose fragments of bone in the joint and bone lumps or cysts

For ligament injuries, tendon problems and bone bruising, an ankle MRI is usually better. Your referrer will say which scan is best. When you book, choose the left or right side.

What happens during the scan

You lie on the scanner bed, usually feet first, with your foot and ankle supported by pads so they stay still. Only your lower leg goes through the scanner, which is a short, open ring. If you have a cast or splint, it can usually stay on. The radiographer controls the scanner from the next room, but can see, hear and talk to you throughout. The scan itself takes only a few minutes. Contrast dye is not usually needed; where contrast is needed, it is charged separately.

Is CT safe?

CT uses X-rays, which are a type of ionising radiation. An ankle CT gives a low dose, because the area scanned is small and far from the organs most sensitive to radiation. The risk from a single scan is very small, and every CT scan is checked by a radiologist or radiographer to make sure the benefit of the scan outweighs the risk, as required by the Ionising Radiation (Medical Exposure) Regulations. If you have had other CT scans recently, tell us when you book.