Lower Extremities
Calcaneous
Anatomy
Routine Projections (ARRT Required)
Axial Plantodorsal
CR Location & Positioning
- SID: 40″
- Patient position: Supine or seated with leg fully extended
- Adjustments: Dorsiflex foot so plantar surface is perpendicular to IR (use gauze or strap if needed)
- CR: 40° cephalad, entering at base of 3rd metatarsal
- Pt. Instructions: Hold still
- Exposure: 65–75 kVp, small focal spot
Evaluation Criteria
- Coverage: Entire calcaneus from posterior tuberosity through subtalar joint
- Rotation checks: Equal appearance of 1st and 5th metatarsals, no medial or lateral shift
- Motion checks: Sharp trabecular detail, Achilles tendon region distinct
- Technique checks: Similar brightness in anterior and posterior calcaneus; if not, consider two images with compensating filter
- Clinical aim: Demonstrates calcaneus and subtalar joint; common for heel pain, stress fractures
Lateral (Mediolateral)
CR Location & Positioning
- SID: 40″
- Patient position: Lateral recumbent with affected side down
- Adjustments: Dorsiflex foot, place calcaneus centered to IR, align plantar surface perpendicular to IR
- CR: Perpendicular, directed 1″ distal to medial malleolus (enters subtalar joint)
- Pt. Instructions: Hold still
- Exposure: 65–75 kVp
Evaluation Criteria
- Coverage: Entire calcaneus, including ankle joint and adjacent tarsals
- Rotation checks: Open sinus tarsi, tuberosity in profile, calcaneocuboid and talonavicular joints open
- Motion checks: Sharp bony detail
- Technique checks: Adequate penetration to show trabecular pattern and soft tissue outline
- Clinical aim: Lateral profile of calcaneus and subtalar joint, evaluation of alignment/displacement
Hows & Whys of Calcaneous Radiography
Anatomy
- What major bone is demonstrated on calcaneus imaging?
The calcaneus (os calcis), the largest tarsal bone. - Which joint is best demonstrated on the axial calcaneus projection?
The subtalar joint. - Which anatomy should be seen in profile on the lateral calcaneus?
The calcaneal tuberosity, subtalar joint, and sinus tarsi.
Positioning
- Why must the foot be dorsiflexed for the axial plantodorsal calcaneus?
To place the plantar surface perpendicular to the IR, preventing elongation and ensuring the subtalar joint is demonstrated. - Why is a 40° cephalic CR angle used on the axial plantodorsal projection?
To project the calcaneus free of superimposition with the leg and open the subtalar joint. - Why is the lateral projection essential in the calcaneus series?
It provides a true profile of the calcaneus, subtalar joint, and surrounding articulations. - Why should the lateral foot be dorsiflexed as much as possible?
To prevent the calcaneus from obscuring the lateral malleolus and to demonstrate the tibiotalar joint.
Technique & Image Evaluation
- How do you know the calcaneus was not rotated on the axial plantodorsal view?
The first and fifth metatarsals should appear equally to either side of the calcaneus, showing symmetry. - What error is indicated if the calcaneus appears elongated on the axial plantodorsal view?
The foot was under-dorsiflexed or the CR angle was excessive. - What error is indicated if the calcaneus appears foreshortened on the axial plantodorsal view?
The foot was over-dorsiflexed or the CR angle was insufficient. - How do you know the lateral calcaneus was positioned correctly?
The sinus tarsi is open, the tuberosity is in profile, and the calcaneocuboid joint is visualized. - What error is indicated if the sinus tarsi is closed on the lateral view?
The foot was rotated rather than placed in a true lateral position. - How can you confirm patient cooperation on calcaneus images?
Sharp trabecular markings and well-defined posterior tuberosity margins indicate no motion.
Clinical Applications
- Why are calcaneus images often obtained in trauma cases?
To rule out fractures of the calcaneus and subtalar joint, which are common with axial loading injuries (e.g., falls from height).
