Anderson-D'Alonzo Classification (Odontoid Fracture)
Anderson-D'Alonzo classification of an odontoid (dens) fracture of C2, types I/II/III, by the level of the fracture line.
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- Anderson-D'Alonzo type
- Type II - through the base / neck of the dens
Result: Anderson-D'Alonzo type II: a fracture through the base (neck) of the odontoid, at its junction with the C2 body. The most common type and the most prone to non-union.
The tool opens with these values already filled in. Replace them with your own.
What the result means
- Type I
- Through the tip of the odontoid, above the transverse ligament (rare, usually stable).
- Type II
- Through the base / neck of the dens (most common, highest non-union risk).
- Type III
- Extending into the cancellous body of C2 (usually heals with immobilization).
What you enter
- Anderson-D'Alonzo type
How this is calculated
Anderson LD, D'Alonzo RT. Fractures of the odontoid process of the axis. J Bone Joint Surg Am. 1974;56(8):1663-1674. Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.