Norwich Image Interpretation Course

Heidi Nunn (Advanced Practice Reporting Radiographer)


The Foot

Normal anatomy Accessory ossicles Phalanges 5th metatarsal Stress fractures Tarsal injuries Lisfranc Midtarsal fracture-dislocation

(hover over images to zoom, click to enlarge)

Learning outcomes
  • Assess skeletal radiographs using a systematic approach
  • Use common lines which are helpful in interpreting the image
  • Understand importance of good radiographic positioning
  • Describe tarsal, metatarsal and phalangeal anatomy
  • Understand mechanisms of injury and the likely fractures/dislocations which may result
  • Search for subtle injuries and understand their clinical significance
  • Accurately describe dislocations and associated fractures
  • Understand common eponyms
  • Understand paediatric anatomy
  • Recognise normal variants and their significance (eg, accessory ossicles)
Normal anatomy
  • DP radiograph - The medial border of the base of the 2nd metatarsal should be in line with the medial border of the middle cuneiform. There is overlap of the lateral metatarsal bases and tarsal bones (cuboid and lateral cuneiform).
  • Oblique radiograph - The medial border of the base of the 3rd metatarsal should be in line with the medial border of the lateral cuneiform. Now the 1st/2nd mt bases, and the medial and middle cuneiforms overlap:
Normal foot alignment    Normal foot alignment
Accessory ossicles - Normal variants
Os tibiale externum
    • Os peroneum - lateral to the cuboid:
Os peroneum
    • Os calcaneus secundarius - adjacent to the anterior process of the calcaneum:
Os calcaneus secundarius
    • Os intermetatarseum - between 1st and 2nd metatarsals:
Os intermetatarseum
    • Hallux sesamoids - these are often bipartite:
Hallux sesamoids
Phalanges
  • Fractures and dislocations are common. Magnification and correct windowing of the image is often necessary for detection.
Fifth metatarsal fractures
  • Avulsion fractures are common at the tuberosity at the base of the 5th metatarsal. This is at the insertion of the peroneus brevis tendon, and avulsions occur due to inversion injuries:
Fracture base 5th metatarsal
  • Jones fracture - refers to a transverse fracture of the proximal shaft of the 5th metatarsal. Has a poorer prognosis and different treatment to avulsion fractures (requires non-weight bearing).
Jones fracture
  • Beware in children the normal unfused apophysis. This should not be mistaken for a fracture, by observing that the apophysis lies longitudinal to the long axis of the metatarsal. A fracture line will run transversely:
Fracture base 5th metatarsal / normal apophysis
  • The normal apophysis may appear displaced and/or fragmented. However this is usually normal:
Normal paediatric apophysis    Normal paediatric apophysis    Normal paediatric apophysis
  • An apophysis is located at a site of ligament or tendon attachment. The apophysis does not contribute to the longitudinal growth of bone. This differs from an epiphysis which is located adjacent to a joint and does contribute to longitudinal growth.
Stress fractures of the metatarsals
  • Radiographic findings are often not evident initially, however approx. 10 days later a transverse radiolucency indicates the site of fracture followed by periosteal reaction and fluffy callus formation indicating healing. Profuse callus formation often subsequently develops. Usually 2nd/3rd distal metatarsal shaft affected:
Stress fracture, 3rd metatarsal    Subtle stress fracture, 2nd metatarsal
Injuries of the tarsal bones
  • Check the lateral cortex of the cuboid for subtle avulsion fractures:
Cuboid avulsion fracture
  • Avulsion fractures of the dorsal surface of the navicular and head of talus are common and often missed. These can only be identified by a lateral view:
Avulsion dorsal aspect talus, navicular
  • Avulsion of the anterior process of the calcaneum by the bifurcate ligament is relatively common but can be subtle, resulting from an inversion injury. This is usually seen on the oblique view of the foot:
Avulsion anterior process calcaneum
  • A second common avulsion site of the calcaneum is seen laterally (on the DP foot) at the insertion of the extensor digitorum brevis muscle:
Avulsion anterolateral calcaneum
  • Injuries to the anterolateral aspect of the calcaneum may be very subtle but, if missed, can be debilitating:
Missed fracture anterolateral calcaneum - 1st attendance    Missed fracture anterolateral calcaneum  - 2nd attendance    Missed fracture anterolateral calcaneum - follow-up
Lisfranc fracture-dislocation (tarso-metatarsal)
  • Refers to fractures at the base of the metatarsals (usually the 2nd) accompanied by lateral subluxation at the tarso-metatarsal joints. The base of the 2nd metatarsal is held in a mortise by the three cuneiform bones. When it is fractured distal to this, the base often remains held in the mortise by the ligaments, with lateral subluxation of the metatarsals:
Lisfranc fracture-dislocation    Lisfranc fracture-dislocation
  • This injury may be subtle. However, by observing the alignment at the base of the 2nd and 3rd metatarsals with the adjacent cuneiforms, this significant injury should not be missed.
Lisfranc fracture-dislocation
Midtarsal fracture-dislocation
  • Disruption of the talo-navicular and calcaneo-cuboid joints, with medial or lateral dislocation of the foot. Occurs due to high velocity trauma; these injuries are usually easy to detect as the foot is obviously deformed:
Midtarsal fracture-dislocation    Midtarsal fracture-dislocation

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