# Anderson-D'Alonzo — Anderson and D'Alonzo classification of odontoid fractures

> Classifies fractures of the odontoid process (dens) of C2 by anatomic location into three types.

**Situação:** vigente · **Órgão:** Coluna · **Órgão emissor:** Orthopedic / spine consensus · **Versão:** 1974 · **Ano:** 1974

## Procedência e vigência
- Família: léxico
- Tipo de lógica: flat
- Modalidade: CT, XR
- Fonte primária: Stulík J, Vyskocil T, Sebesta P, Kryl J (StatPearls); after Anderson LD, D'Alonzo RT 1974. Anderson and D'Alonzo classification of odontoid (dens) fractures (2024) — https://www.ncbi.nlm.nih.gov/books/NBK441956/
- Última verificação: 2026-06-26
- Última checagem: 2026-06-26

## Categorias

| Código | Rótulo | Critérios | Conduta | Risco | Localizador | Verificado |
| --- | --- | --- | --- | --- | --- | --- |
| I | Type I, apex (tip) of the dens | Type I: fracture involving the apex (tip) of the odontoid process, above the transverse ligament, generally representing an avulsion at the alar ligament insertion. | Generally stable and treated conservatively; if instability is suspected (e.g., alar ligament avulsion), dynamic radiographs are recommended to evaluate. | Usually stable; least common type. Instability is a concern only if associated ligamentous disruption is present. | StatPearls NBK441956 (Odontoid Fractures): 'Type I odontoid fractures involve the apex of the dens and are generally stable. However, if instability is suspected... dynamic radiographic imaging is recommended.' | ✓ |
| II | Type II, base/neck of the dens | Type II: fracture through the neck (base) of the odontoid process, at the junction with the C2 body. Subtypes by fracture-line pattern (anterior oblique, posterior oblique, horizontal); the type IIA variant is an unstable comminuted fracture at the dens base. | Most common subtype and generally considered unstable; management is individualized (immobilization vs surgical fixation) given the well-known risk of nonunion, particularly in the comminuted IIA variant. | Highest nonunion risk of the three types because the fracture crosses the watershed neck of the dens; generally unstable. | StatPearls NBK441956: 'Type II... involve the neck of the odontoid process... the most common subtype and are generally considered unstable. The type IIA variant specifically features unstable comminuted fractures at the base of the dens.' | ✓ |
| III | Type III, fracture extending into the C2 body | Type III: fracture extending below the base of the dens into the cancellous body of C2 (and may involve the C1-C2 facet joints). | Non-surgical treatment with external immobilization is the preferable option for most patients, owing to the broad cancellous fracture surface and better union potential. | Better healing potential than type II because of the large cancellous bone contact area; generally treated nonoperatively. | StatPearls NBK441956: 'Type III fractures extend into the body of C2. Non-surgical treatment with external immobilization remains the preferable option for most patients with this type of fracture.' | ✓ |

### Citações por categoria
- **I**: Stulík J, Vyskocil T, Sebesta P, Kryl J (StatPearls); after Anderson LD, D'Alonzo RT 1974. Anderson and D'Alonzo classification of odontoid (dens) fractures (2024) — https://www.ncbi.nlm.nih.gov/books/NBK441956/ · StatPearls NBK441956 (Odontoid Fractures): 'Type I odontoid fractures involve the apex of the dens and are generally stable. However, if instability is suspected... dynamic radiographic imaging is recommended.'
- **II**: Stulík J, Vyskocil T, Sebesta P, Kryl J (StatPearls); after Anderson LD, D'Alonzo RT 1974. Anderson and D'Alonzo classification of odontoid (dens) fractures (2024) — https://www.ncbi.nlm.nih.gov/books/NBK441956/ · StatPearls NBK441956: 'Type II... involve the neck of the odontoid process... the most common subtype and are generally considered unstable. The type IIA variant specifically features unstable comminuted fractures at the base of the dens.'
- **III**: Stulík J, Vyskocil T, Sebesta P, Kryl J (StatPearls); after Anderson LD, D'Alonzo RT 1974. Anderson and D'Alonzo classification of odontoid (dens) fractures (2024) — https://www.ncbi.nlm.nih.gov/books/NBK441956/ · StatPearls NBK441956: 'Type III fractures extend into the body of C2. Non-surgical treatment with external immobilization remains the preferable option for most patients with this type of fracture.'


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> Conteúdo de referência reescrito. Confira a publicação primária vigente. Não é dispositivo médico nem substitui o julgamento clínico. O radiologista responsável pelo laudo permanece o autor e o responsável.

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