10.1 Foot, Toes & Ankle

10.1 Foot, Toes & Ankle

Quick Answer: Distal lower-extremity general radiography for the RTR candidate is built on true planes, correct centering, and joints that frame the injury. Toes need AP (or slight AP axial), 45° oblique, and true lateral. The foot is AP (dorsoplantar), medial oblique, and lateral, centered near the base of the 3rd metatarsal. The calcaneus needs an axial (plantodorsal) and lateral. The ankle is AP, mortise (15–20° medial rotation), and lateral. Weight-bearing foot/ankle series answer alignment and arch questions that non–weight-bearing views cannot. Critique stems often hide a Jones, Lisfranc, bimalleolar, or trimalleolar injury—or a mortise that is not truly open.

General radiography — skeletal (lower limb distal) sits inside the high-weight clinical procedures and image-analysis cluster of the CAMRT Radiological Technology exam (RTR.3–RTR.6). Examiners expect you to choose projections that demonstrate the anatomy the requisition implies, mark laterality correctly, collimate tightly, and adapt for trauma without creating secondary injury.

Shared Positioning Principles (Distal LE)

• Part parallel to the IR for joints and long bones when possible; elevation of one end foreshortens shafts and closes joint spaces.
• CR perpendicular to the IR for standard AP/PA and laterals unless a named axial projection specifies angulation (calcaneus, some toe AP axial protocols).
• SID typically 100–115 cm (about 40 in) for tabletop extremities; follow department technique charts and AEC rules if used (many distal extremities remain manual technique).
• Collimate to skin margins plus required joints—tight for scatter/ALARA, never so tight that distal tufts, calcaneal tuberosity, or malleoli are clipped.
• Lead markers (R or L) must appear in the primary field without overlying critical bone; electronic annotation is not a substitute for correct side-marking culture.
• Remove shoes, socks, jewelry, and opaque dressings when clinically safe; explain the reason so patients cooperate without feeling rushed.

Immobilization (sponges, tape, sandbags, commercial holders) is a care-provider skill. Never force a suspected fracture into textbook position—use horizontal-beam laterals, support the limb, and document limitations on the requisition/PACS note.

Toes (Digits 2–5)

Exam traps: Centering at the MTP instead of the PIP for a toe series misplaces the field. A “lateral” that remains oblique superimposes fracture lines at phalangeal heads. Always isolate the injured digit on the lateral so soft-tissue margins are not double-exposed by a neighbor.

Great toe (1st digit)

The hallux is often imaged alone for trauma, sesamoid evaluation, or post-op alignment. AP and lateral of the 1st digit center near the 1st MTP; include the distal first metatarsal. Sesamoid views (tangential, patient prone or supine with toes dorsiflexed) project the sesamoids free of the first metatarsal head—know that they exist when a stem mentions plantar first-MTP pain after forced dorsiflexion.

Foot

Medial oblique is the workhorse for the base of the 5th metatarsal (Jones and avulsion territory) and for lateral midfoot structures. Lateral answers height of the arch, calcaneal pitch, and talar alignment. Some departments add lateral oblique or weight-bearing AP/lateral for alignment and flatfoot/pes cavus questions.

Weight-bearing foot notes

Weight-bearing AP and lateral foot projections assess functional alignment of the arch, tarsometatarsal joints, and hindfoot under load. They are preferred for many outpatient alignment and pre-op planning exams when the patient can stand safely. Non–weight-bearing views remain standard for acute trauma, non-ambulatory patients, and portable work. On CAMRT stems, match the clinical question: alignment/arch → weight-bearing if possible; acute fracture with inability to bear weight → tabletop series with trauma adaptations.

Calcaneus (Os Calcis)

Bohler’s angle (tuber angle) is measured on the lateral calcaneus and is a classic trauma critique concept—severe depression of the posterior facet flattens the angle after calcaneal compression fracture. You are not expected to memorize every measurement method, but you must produce a true lateral so angles and joint relationships are trustworthy.

If the patient cannot dorsiflex for plantodorsal axial, reverse (dorsoplantar) axial with the patient prone or with CR angled from the plantar aspect per protocol is an accepted adaptation—document the method.

Ankle

Why the mortise matters

A true AP does not fully open the lateral clear space because the fibula sits slightly posterior. The mortise view rotates the leg so the intermalleolar line is parallel to the IR, opening the entire ankle mortise for joint-space symmetry and detecting subtle talar shift (e.g., after deltoid or syndesmotic injury). Under-rotation leaves the lateral mortise closed; over-rotation opens it asymmetrically and can mimic pathology. Critique: equal joint spaces medial and lateral with the talus centered under the tibial plafond.

Stress views (manual or gravity eversion/inversion) may be ordered by the referring clinician for ligamentous stability—perform only as protocol and patient condition allow; they are not routine primary trauma series.

Weight-bearing ankle

Standing AP/mortise and lateral ankle projections evaluate tibiotalar alignment under load and are common in chronic instability and pre-op pathways. Acute non-weight-bearing patients stay on the table with horizontal-beam lateral if needed.

High-Yield Fractures & Critique Links

| Injury | Classic radiographic idea | Positioning / critique note | |---|---|---|---|n| Jones fracture | Transverse fracture of proximal 5th metatarsal metaphysis/diaphysis (typically 1.5–2 cm distal to tuberosity), high non-union risk | Foot medial oblique and AP essential; do not confuse with tuberosity avulsion (pseudo-Jones) at the styloid | | 5th MT tuberosity avulsion | Avulsion at peroneus brevis/plantar aponeurosis insertion on tuberosity | Same series; more proximal/styloid than true Jones | | Bimalleolar fracture | Fractures of both medial and lateral malleoli (or equivalent ligamentous injury creating unstable ankle) | True AP, mortise, lateral; assess talar shift; do not force dorsiflexion or rotation if grossly unstable | | Trimalleolar fracture | Bimalleolar pattern plus posterior malleolus (posterior tibial lip) | Lateral is decisive for posterior fragment; include full distal tibia | | Lisfranc injury | Tarsometatarsal fracture–dislocation; malalignment at midfoot | Weight-bearing AP/oblique if possible; non-weight-bearing may underestimate diastasis | | Calcaneal compression | Fall from height; Bohler angle reduced; often bilateral/ lumbar association clinically | True lateral + axial; trauma history may trigger lumbar imaging per protocol |

On CAMRT-style stems, match the projection deficiency to the missed diagnosis: a foot series without medial oblique under-calls base-of-5th injuries; an “AP only” ankle misses mortise diastasis; a lateral that is rotated underestimates posterior malleolar step-off; forced positioning of an unstable ankle is a care-provider and safety failure, not a technical victory.

Technique & Image Quality Reminders

Distal extremity work is high spatial-resolution territory. Use the small focal spot when tube loading allows, adequate mAs for noise control on digital detectors, and kVp in the typical extremity range (often ~50–65 for toes/foot; slightly higher for ankle/calcaneus axial—follow charts). Check exposure index against department targets. Soft-tissue detail matters for swelling patterns around the malleoli and fifth metatarsal. Motion from pain is common—immobilize and coach brief stillness rather than blindly increasing mA.

Grid use is uncommon for toes and most feet on tabletop; thicker ankles or portable grids follow department rules. Always apply gonadal shielding when it does not obscure anatomy of interest and is consistent with current departmental/provincial practice—distal LE exams usually keep the beam far from the gonads, but shield the pelvis when the patient is seated or the primary beam could include it.

CAMRT Application Focus

When an item describes lateral midfoot pain after inversion and a “bump” over the 5th metatarsal base, prioritize foot AP and medial oblique evaluation of the proximal 5th metatarsal, and distinguish Jones from tuberosity avulsion. When the stem mentions inability to bear weight after ankle twist with medial and lateral tenderness, demand AP, mortise, and lateral, and look for talar shift and posterior malleolar involvement on the lateral. When calcaneal trauma follows a fall from height, produce a true lateral and axial and remember associated injuries may be investigated elsewhere. Positioning knowledge, fracture pattern recognition, and safe adaptation for unstable ankles form one competency chain for RTR.4 / RTR.6, not separate silos.