Anatomy of the Foot and Ankle
The foot is a structure of the body with numerous joints, bones, muscles, ligaments, and tendons. It is responsible for the coordinated movements of gait and the body’s ability to stand upright(1).
The primary bones in the foot are the tarsals (bones connecting the lower leg to the foot), metatarsals (long bones of the foot), and phalanges (five bones in the toes)(2).
The bones are connected by the tarsometatarsal joints (the joints between the tarsals and metatarsals), midtarsal joint (joints connecting the tarsals and metatarsals), and metatarsophalangeal (MTP) joints (joints between the metatarsals and the phalanges)(3).
Meanwhile, the ankle is a hinge joint found in the talus bone where two bones, tibia and fibula, meet. A strong ligament thickens the ankle on its sides(4).
Ankle and Foot CT
The foot is prone to several types of damage and injuries. Pain and inflammation of the foot may cause limited movement(5).
Medical professionals use advanced imaging procedures to diagnose medical problems in the foot. A computed tomography scan of the foot and ankle may help doctors examine any injury or fractures(6).
An ankle and foot computed tomography (CT) may detect the following(7):
- Osteomyelitis or bone infection
- Foreign bodies
What to Expect From an Ankle and Foot CT
Before the Procedure
The patient must ask the hospital about the individual preparation requirements for their planned ankle and foot CT exam.
Some CT of the feet and ankles may require the injection of intravenous contrast agents. However, the need for a contrast dye depends on the reason for the exam.
If a doctor recommends a CT scan with contrast dye, the patient must submit a recent blood test to assess the function of their kidneys. This requirement should be accomplished before their appointment.
Before the procedure, the patient must also inform their radiologist if they are pregnant.
If a patient suspects that they may be pregnant, then a pregnancy test must be performed before the patient proceeds to take the ankle and foot CT exam.
The patient must also accomplish medical paperwork, such as questionnaires and consent forms, which they must complete upon their arrival at the hospital.
In some hospitals, individuals under the age of 16 must have a consent form signed by a guardian before undergoing the procedure.
Patients should remove all their jewelry and metal items before they enter the room with the CT machine. The items must be removed as they may affect and obscure the images(8).
During the Procedure
If the CT scan includes contrast agents, the doctor may administer the contrast dye before the procedure begins.
The contrast agent highlights the blood vessels in the body during the procedure, allowing the machine to make blood flow more visible in the images(9).
The patient may lie on the CT examination bed, which slides in and out of the CT scanner multiple times.
Once the machine has captured enough images of the ankle and foot, the examination is complete.
A radiologic technologist must always be a short distance away, watching the patient at all times during the procedure.
After the Procedure
After completing a CT examination with intravenous contrast, the patient must flush the contrast dye out of their body by drinking plenty of fluids.
If the patient who took a contrast dye injection is also taking medications for diabetes, the doctor may advise them to stop taking their diabetes medication for two days after the scan.
Stopping the medication may prevent a buildup of the drugs in the patient’s system(10).
A radiologist analyzes the images produced by the CT scan machine. They may draft a report of the results to the referring doctor, who may discuss these findings with the patient.
Risks of a CT Scan
There is a low risk of radiation exposure during the procedure since the CT machine emits a small amount of radiation during a scan.
Patients must tell their physician if they are pregnant or if they suspect they may be pregnant. Exposure to radiation during pregnancy may result in congenital problems(11).
Another risk associated with the procedure is an allergic reaction to the contrast dye. Before the exam, patients must notify their doctor if they are sensitive or allergic to iodine, a chemical present in the contrast dye.
Patients with kidney problems must also notify their physician before the procedure. In some cases, a contrast dye may cause kidney failure(12).
To minimize the risks of ankle and foot CT scan, the patient should discuss any medical concerns with their physician before undergoing the procedure.
- Ficke, J. & Byerly, D. (2020). Anatomy, Bony Pelvis and Lower Limb, Foot. StatPearls. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK546698/
- Bone And Joint Decade. Global Alliance for Musculoskeletal Health. The Foot & Ankle. Retrieved from http://bjdonline.org/the-foot-ankle/
- O’Rahilly, R., Müller, M., Carpenter, S., & Swenson, R. (2004) BASIC HUMAN ANATOMY A Regional Study of Human Structure. https://www.dartmouth.edu/~humananatomy/part_3/chapter_17.html
- University of Rochester Medical Center. Anatomy of the Foot. Retrieved from https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=85&contentid=P07387
- South Western Sydney Local Health District. Foot and Ankle CT. Retrieved from https://www.swslhd.health.nsw.gov.au/medicalImaging/serv_CT_Extremities_Foot.html
- Stanford Healthcare. Risks of Computed Tomography (CT) Scan. Retrieved from https://stanfordhealthcare.org/medical-tests/c/ct-scan/risk-factors.html