Clinical calculator
Böhler Angle
The Böhler angle is measured on a lateral radiograph of the hindfoot between a line from the highest point of the anterior process to the highest point of the posterior facet and a line from that point to the top of the tuberosity, and it normally measures 20° to 40° — a flattened or negative angle indicates depression of the posterior facet.
What the Böhler Angle score means
Böhler Angle scores run from -90 to 90, where a higher score is better. The bands below are conventional reporting categories, not diagnostic cut-offs.
- Negative — severe articular depression-90–-0.1
The posterior facet has collapsed below the line joining the anterior process and the tuberosity. Associated with severe joint depression and a poorer functional result.
- Reduced — depressed intra-articular fracture likely0–19.9
Below the normal range. In the context of trauma this strongly suggests a depressed intra-articular calcaneal fracture; get a CT.
- Within the normal range20–40
A normal angle does not exclude a calcaneal fracture. Extra-articular fractures, tongue-type fractures with minimal depression and anterior process fractures all leave it intact.
- Above the normal range40.1–90
Uncommon. Re-check the landmarks and the lateral positioning before accepting it — an obliquely projected film is the usual explanation.
Published criteria and reliability
The published cut-offs that define this instrument, and the measured agreement between observers using it. Each is reported with the population it was derived in.
| Type | Value | Subscale | Population | Follow-up | Source |
|---|---|---|---|---|---|
| Criterion | Normal range 20° to 40° | — | Uninjured adult hindfoot on a true lateral radiograph | — | Böhler L 1931 |
| Criterion | An angle below 20° in the context of trauma indicates depression of the posterior facet and should prompt CT | — | Adults with suspected calcaneal fracture | — | Isaacs JD 2013 |
| Criterion | A markedly reduced initial angle is associated with a worse functional outcome, and restoration of the angle with a better one, in displaced intra-articular fractures | — | Displaced intra-articular calcaneal fractures treated operatively and non-operatively | — | Loucks C 1999 |
Criterion is a published cut-off, definition or performance figure belonging to a classification or decision rule — it is not a change score and should not be read as one.
How the score is calculated
Stated in full so the calculation can be independently checked, and reproduced by hand if needed.
Two lines are drawn on a true lateral radiograph of the hindfoot. The first runs from the highest point of the anterior process of the calcaneus to the highest point of the posterior facet. The second runs from that same point on the posterior facet to the most superior point of the calcaneal tuberosity. The Böhler angle is the angle subtended between them, and it normally measures between 20° and 40°. When the posterior facet is driven downwards by an axial load, the apex of the angle flattens, so the angle falls; if the facet drops below the line joining the anterior process and the tuberosity, the angle becomes negative. The measurement therefore describes the loss of sagittal height of the posterior facet, and nothing else — it is not a fracture classification and carries no information about the number of articular fragments, the width of the heel or the position of the tuberosity. Because the normal range is wide and varies between individuals, a measurement from the uninjured side is a more useful comparator than the population range when it is available.
Instrument profile
- Developer
- Lorenz Böhler
- Institution
- Vienna, Austria
- First published
- 1931
- Items
- 1
- Response format
- A single measured angle in degrees
- Score range
- -90 to 90
- Direction
- Higher score = better
- Completion time
- About 1 minutes
- Regions
- Foot & Ankle
- Conditions
- Calcaneal fracture, Intra-articular calcaneal fracture, Hindfoot trauma, Subtalar joint depression
- Procedures
- Open reduction and internal fixation of the calcaneus, Percutaneous reduction of a calcaneal fracture, Subtalar arthrodesis
- Validity
- Correlates with the degree of posterior facet depression and, in displaced intra-articular fractures, with functional outcome — both the angle at injury and the angle achieved at reduction carry prognostic information. Its sensitivity as a screening test for calcaneal fracture is only moderate, because several fracture patterns leave it normal.
- Reliability
- Agreement between observers is reasonable but depends entirely on lateral positioning; an obliquely projected film shifts the landmarks and the measurement with them. Agreement improves when the same observer measures both heels on the same study.
When to use the Böhler Angle
Well suited to
- Assessing a lateral hindfoot radiograph after an axial-load injury, as a quick indicator of posterior facet depression.
- Judging the adequacy of reduction intraoperatively and at follow-up, against the measurement from the uninjured side.
- Communicating the severity of a calcaneal fracture in a single number that other clinicians will interpret the same way.
Limitations and poor fits
- To exclude a calcaneal fracture. Extra-articular, anterior process and minimally depressed tongue-type fractures all leave the angle normal.
- In place of CT for surgical planning — the Sanders classification, which is derived from the coronal CT, is what describes the articular fragments.
- On an oblique or poorly positioned lateral film, where the landmarks are not where they appear to be.
- In children, whose normal values differ and in whom the ossification of the apophysis changes the landmarks.
Böhler Angle compared with other instruments
Instruments measuring a related construct, with the practical difference between them.
| Instrument | Items | Range | What it adds |
|---|---|---|---|
| Sanders | 3 | 1–4 | The Sanders classification grades displaced intra-articular calcaneal fractures into four types by the number of posterior facet fragments seen on the widest coronal CT image — type I non-displaced, type II two-part, type III three-part and type IV four-part or comminuted — and the type number predicts the outcome of internal fixation. |
| Hawkins | 3 | 1–4 | The Hawkins classification grades talar neck fractures by how many of the talus’s articulations are dislocated — none in type I, the subtalar joint in type II, the subtalar and tibiotalar joints in type III, and all three including the talonavicular joint in type IV — and the reported rate of avascular necrosis rises steeply with each type. |
| Weber | 3 | 1–3 | The Danis-Weber classification sorts ankle fractures into three types by the level of the fibular fracture relative to the tibiotalar joint line — type A below the syndesmosis, type B at it, and type C above it — because the height of the fibular fracture predicts how much of the syndesmosis is torn. |
| AOFAS Ankle-Hindfoot | 9 | 0–100 | The AOFAS Ankle-Hindfoot Scale is a 100-point clinician-administered rating combining 40 points for pain, 50 for function across seven items and 10 for alignment — and although it remains the most-reported outcome in the foot and ankle literature, the society that published it withdrew its endorsement in 2011 because it was never validated. |
Copyright and permitted use
Published openly because it is the question every clinician and researcher asks before using an instrument, and almost nobody answers it.
A published radiographic measurement. No licence is required.
References
- Böhler L. Diagnosis, pathology and treatment of fractures of the os calcis. Journal of Bone and Joint Surgery. 1931.
- Loucks C, Buckley R. Böhler’s angle: correlation with outcome in displaced intra-articular calcaneal fractures. Journal of Orthopaedic Trauma. 1999.
- Isaacs JD, Baba M, Huang P, et al.. The diagnostic accuracy of Böhler’s angle in fractures of the calcaneus. Journal of Emergency Medicine. 2013.
Editorial status
This page has not yet been signed off by a named clinical reviewer. The scoring logic is stated in full above so it can be independently verified, and every threshold is traceable to its source. See our editorial methodology.