Normal Böhler's Angle Size on Radiography and CT
Böhler's angle is a geometric measurement on the lateral foot radiograph formed between two lines drawn along the superior calcaneal surface, reflecting the overall height and architecture of the calcaneus. It is a fundamental parameter in evaluating calcaneal integrity and posterior facet alignment. Accurate measurement is essential for identifying fracture depression and guiding surgical planning in heel injuries.
Normal Reference Values
| Orientation | Measurement |
|---|---|
| Lateral | 25-40¡ |
Clinical Significance
A normal Böhler's angle of 25–40° indicates preserved calcaneal height and posterior facet congruency. A reduced angle — typically below 20–25° — strongly suggests depression of the posterior subtalar facet, most commonly due to an intra-articular calcaneal fracture from axial loading. A flattened or reversed (negative) angle indicates severe comminution and significant loss of calcaneal height, which correlates with poorer functional outcomes if left unreduced.
Elevations above 40° are less common but may be seen in pathological bone conditions or measurement error. It is important to recognize that a normal Böhler's angle does not completely exclude occult calcaneal fracture, particularly tongue-type variants; CT remains the gold standard for fracture characterization.
- Intra-articular calcaneal fracture (most common cause of angle reduction)
- Extra-articular calcaneal fracture (angle may be preserved)
- Subtalar joint arthritis with bony remodeling
- Pathological fracture (e.g., metastatic disease, insufficiency fracture)
- Post-traumatic malunion with calcaneal flattening
Reference: Browner BD, Levine AM. Skeletal Trauma, Basic Science, Management, and Reconstruction. W B Saunders Company. p. 2631 (2009)
Imaging Notes
On lateral radiography, Böhler's angle is constructed by drawing a line from the highest point of the anterior calcaneal process to the highest point of the posterior facet, and a second line from the latter point to the superior aspect of the calcaneal tuberosity. The angle formed at their intersection is measured. Strict lateral positioning — with no rotation — is critical for reproducibility; even minor obliquity can artificially alter the measurement.
On CT, the angle can be reconstructed on sagittal reformats and is particularly valuable when plain radiograph quality is suboptimal or when fracture comminution obscures landmarks. CT also allows simultaneous evaluation of the posterior facet step-off, Sanders classification, and three-dimensional fracture morphology, making it indispensable in operative planning.