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Lower Extremities

9 Calcaneous

Anatomy

  • Calcaneus (os calcis) – largest tarsal bone, weight-bearing heel bone.
  • Sustentaculum tali – medial projection supporting the talus.
  • Posterior tuberosity – attachment site for Achilles tendon.
  • Anterior, middle, posterior articular facets – articulate with talus to form the subtalar joint.
  • Subtalar joint (talocalcaneal joint) – diarthrodial, gliding type.
  • Sinus tarsi – space between calcaneus and talus seen best on oblique or lateral.
  • Calcaneocuboid joint – articulation between calcaneus and cuboid.

Projections

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).
  • Why is the Harris-Beath (weight-bearing axial) method sometimes used?
    It demonstrates calcaneotalar coalition (abnormal bony fusion) and stress fractures under physiologic load.

 

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Radiographic Procedures Review Guide Copyright © 2025 by Carla M. Allen and Taylor M. Otto. All Rights Reserved.