Introduction

This e-Anatomy module is dedicated to the anatomy of the ankle and foot, showing the normal CT appearance of the bones, joints, ligaments, tendons, and muscles.

The main indications for computed tomography (CT) of the ankle and foot are:

1. Detection and characterization of radiographically occult or complex fractures: CT is indicated when initial radiographs are negative or equivocal but clinical suspicion for fracture remains high, especially in cases of persistent pain, high-energy trauma, or complex anatomical regions such as the midfoot, hindfoot, or posterior malleolus. CT is superior to radiography for identifying subtle, comminuted, or intra-articular fractures, including talar, calcaneal, Chopart, and posterior pilon variant fractures. 
2. Assessment of fracture extent and preoperative planning: CT provides detailed multiplanar imaging for surgical planning in complex fractures and dislocations, including evaluation of alignment abnormalities, syndesmotic injuries, and transsyndesmotic ankle fracture dislocations.
3. Evaluation of chronic bone pathology: CT is useful for diagnosing and characterizing chronic conditions such as nonunion, osteochondral lesions, painful accessory ossicles, sesamoid stress fractures, and Freiberg’s infraction when radiographs are inconclusive.
4. Assessment of suspected osteomyelitis and soft tissue infection in diabetic foot: CT is indicated for evaluating the extent of osseous destruction, sequestrum, and soft tissue involvement, especially when radiographs are indeterminate or for pretreatment planning. CT with IV contrast is preferred for assessing soft tissue infection and fluid collections, though MRI is more sensitive for early osteomyelitis.

Material and methods

This CT of the ankle and foot was performed on a healthy 24-year-old male patient using a Siemens CT-Scan.

The main imaging planes used for CT of the ankle and foot were the axial, coronal, and sagittal planes. These planes are typically acquired as thin, contiguous slices and can be reformatted to optimize visualization of complex anatomy and pathology.

• Axial plane: This is the primary acquisition plane for most CT protocols. It is essential for evaluating the alignment of the ankle mortise, detecting fractures, and assessing the relationship of the distal tibia, fibula, and talus. It is also useful for identifying syndesmotic injuries and subtle fracture lines.
• Coronal plane: Coronal reformats are particularly valuable for assessing the integrity of the lateral and medial malleoli, the subtalar joint, and the extent of articular involvement in fractures. They are also important for evaluating hindfoot alignment and for surgical planning in complex injuries.
• Sagittal plane: Sagittal reformats are crucial for visualizing the anterior and posterior malleoli, the talar dome, and the longitudinal extent of fractures. They are also used to assess the plantar structures and the alignment of the midfoot and hindfoot.
• 3D VR reconstructions: Three-dimensional volume-rendered images can supplement multiplanar reformats to provide a comprehensive view of complex fractures, congenital deformities, or postoperative anatomy.

The anatomical structures were labeled by Antoine Micheau M.D. (Radiologist, Montpellier – France), following the Terminologia Anatomica 2.