Foot radiography

Indications for the examination and Ottawa rules

The prescription of an X-ray examination must be strictly justified by the clinical picture. When osteoarthritis of the foot joints (including the first metatarsophalangeal joint) is suspected, it is not recommended to limit the imaging to a single toe. A comprehensive X-ray in two projections is performed exclusively for differential diagnosis, before referring the patient to an orthopedic trauma surgeon, or at the surgical planning stage.

In case of traumatic injury, the decision to perform an X-ray is made based on the Ottawa rules. An X-ray is necessary if the patient complains of midfoot pain and at least one of the following criteria is present:

• Pronounced tenderness upon palpation of the navicular bone.
• Local pain upon palpation of the base of the fifth metatarsal bone.
• Inability of the patient to bear body weight (inability to take four independent steps immediately after the incident and during the doctor's examination).

Technique and special positioning views

To obtain a high-quality and informative image, the standard anteroposterior projection requires strict adherence to physical parameters. The focal distance from the X-ray tube to the limb must be exactly 1 meter — this is the only way to accurately determine the true dimensions of the metatarsal bones. The X-ray tube angle is set at 15 degrees to the vertical axis.

In situations where computed tomography cannot be performed (e.g., calcaneal fractures), additional projections are used to clarify the position of bone fragments:

1. Harris axial projection. Performed with the ankle joint in dorsiflexion. The beam is directed at an oblique angle to the plantar area. This makes it possible to assess the degree of impression of bone fragments and the extent of intra-articular damage.
2. Broden projection. The patient lies supine, and the foot is internally rotated so that the malleoli are parallel to the cassette. The beam, with a 30-degree cranial tilt, is centered on the subtalar joint. This positioning is optimal for visualizing fractures of the posterior aspect of the subtalar-calcaneal articular facet.
3. Canale projection. Used for fractures of the talar neck. The foot is in maximum plantar flexion and internally rotated by 15 degrees. The tube is tilted caudally by 15 degrees. The method is useful for assessing the contours of the neck and monitoring the accuracy of bone reduction during surgery.

Features of pediatric foot X-ray anatomy

Reading radiographs in children requires a deep understanding of the chronology of ossification. Growth plates, pseudo-epiphyses, and multiple ossification centers are normal physiological variants, but can outwardly resemble fractures.

Timing of appearance of ossification centers:

• At birth: ossification centers of the talus and calcaneus are already formed.
• First year of life: ossification of the cuneiform bones begins.
• From 6 to 24 months: secondary centers of the phalanges and metatarsal bones appear.
• From 2 to 4 years: the navicular bone begins to ossify. It is important to note that the presence of multiple ossification centers for this bone is considered an absolute norm.

The biomechanics of traumatic injuries in pediatric patients are also specific. A child's tendons and ligaments are much more elastic and relatively stronger than the epiphyseal plate. As a result, during severe trauma, the epiphyseal plate, being the weakest link, is affected first. Therefore, growth plate injuries in children are diagnosed much more frequently than ligamentous tears.

Diagnostic algorithm and treatment planning

Making a fracture diagnosis is based on four stages of examination. First, complaints and medical history are collected, followed by a physical examination assessing skin integrity, tenderness, deformities, edema, functional impairment, and abnormal mobility.

The baseline instrumental examination for injuries of the forefoot and midfoot is an X-ray in two projections. For talar injuries, an ankle X-ray serves as the basis, while foot X-rays are performed optionally. Outpatient laboratory diagnostics are ordered at the physician's discretion and are mandatory only upon hospitalization for surgical treatment planning.

The goal of all X-ray diagnostics is to determine the position of fragments and choose the management strategy. Conservative treatment is used for calcaneal fractures without displacement or with acceptable displacement (the clear criteria for which are individual) with the goal of early functional rehabilitation, as well as when surgery is contraindicated or declined.

Class and exam questions

What else to study on this topic

• Differential diagnosis of ossification centers and fractures in pediatric patients
• Criteria for individual determination of "acceptable displacement" in calcaneal injuries
• Intraoperative X-ray control: capabilities and limitations
• Indications for CT and MRI in complex bone injuries of the foot

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.