First and second year — the floor first, then every step
Fall from height: measure Böhler's angle on the lateral radiograph, then classify the posterior facet on the coronal CT (Sanders) — and look at the lumbar spine and the other foot.
Orient first
Most calcaneal fractures are intra-articular through the POSTERIOR FACET of the subtalar joint, driven by the talus acting as a wedge.
Böhler's angle flattens when the posterior facet is depressed; a normal angle does not exclude a fracture.
The mechanism (axial load) injures the other calcaneus and the thoracolumbar spine in a significant minority — examine both.
Acquire the study
Lateral and axial (Harris) views of the calcaneus; include the contralateral side if the mechanism is a fall.
The manoeuvre
Lateral: BÖHLER'S ANGLE — the angle between a line from the posterior tuberosity to the top of the posterior facet and a line from the top of the posterior facet to the anterior process (normal about 20–40°).
Lateral: CRITICAL ANGLE OF GISSANE at the junction of the posterior facet and the anterior process.
Lateral: tongue-type (fracture line exiting posteriorly through the tuberosity) versus joint-depression (the facet fragment separate from the tuberosity).
Axial (Harris) view: calcaneal widening and varus of the tuberosity.
What confirms it
A fracture line through the calcaneus; intra-articular extension into the posterior facet on CT.
What licenses you to exclude it
A normal Böhler's angle does not exclude a fracture.
The classic misread
Missing an anterior process fracture — it hides on the lateral view and is often called a sprain.
Reporting the injury
Classification to use
Sanders (CT, coronal at the widest posterior facet): I undisplaced; II two-part; III three-part; IV four-part or comminuted — with the letter for the fracture line position. Essex-Lopresti tongue-type versus joint-depression on the lateral view.
Measurements — and how to take them
Böhler's angle (normal about 20–40°) and the side-to-side difference.
Posterior facet step-off and gap in mm.
Heel height and width compared with the other side.
What to report
Extra- versus intra-articular; Sanders type; posterior facet step-off; Böhler's angle; calcaneocuboid extension; lateral wall and peroneal tendons; heel height and width.
How to report it
CT: "Intra-articular joint-depression calcaneal fracture, Sanders IIB, with 4 mm step-off of the posterior facet. Böhler's angle 8°. Lateral wall blow-out with dislocation of the peroneal tendons. Extension into the calcaneocuboid joint."
What not to report
Do not quote a Sanders type from a slice that is not at the widest part of the posterior facet.
Peroneal tendon dislocation; compartment syndrome of the foot (clinical).
Reference values
Each value carries the caveat that keeps it from being misused. Normal limits and diagnostic criteria are kept apart on purpose: a disease cut-off read as a normal range is the more dangerous mistake.
Lateral calcaneal/ankle radiograph. Line 1: highest point of the anterior process to the highest point of the posterior facet. Line 2: tangent from the posterior facet to the superior edge of the tuberosity. The angle between them.
Below 20° suggests a depressed intra-articular calcaneal fracture. ⚠️ A NORMAL ANGLE DOES NOT EXCLUDE A FRACTURE — an undisplaced or extra-articular fracture leaves it intact. Paediatric values differ from adult.
X-ray · CT
Calcaneus · Critical angle of Gissaneapproximately 120–145°
Lateral calcaneal radiograph. The angle between the downward slope of the posterior facet and the upward slope of the anterior process, at their junction in the lateral wall.
Increases when the posterior facet is depressed; read together with Böhler, never alone. Published ranges vary between texts — confirm which range your department reports against.
WEIGHT-BEARING lateral foot radiograph. The angle between the plantar surface of the calcaneus and the supporting horizontal surface.
Reduced in pes planus, increased in pes cavus. ⚠️ MUST BE WEIGHT-BEARING — a non-weight-bearing film does not reproduce the deformity and the measurement is meaningless without it.
X-ray
See it on real cases
Direct links to Radiopaedia — the reference article and worked cases with their images. Each opens on Radiopaedia.