Graf Classification of Hip Dysplasia: Types 1–4 (α/β Angles and Management)
Method Basics
The classification is based on measuring the bony angle α and the cartilaginous angle β on a standard coronal ultrasound plane of the hip joint. According to the source, the β angle is less critical than the α angle. The terminology used is developmental dysplasia of the hip (DDH); the term congenital dysplasia of the hip (CDH) is considered less accurate.
Definition
Hip dysplasia is the underdevelopment of the acetabular component of the joint. Assessment is conducted according to the modified Graf staging.
Types According to the Modified Graf Classification
| Type | Characteristic | Angle α | Angle β |
|---|---|---|---|
| Ia | Mature joint, angular bony prominence (promontory) | > 60° | < 55° |
| Ib | Mature joint, rounded bony prominence | > 60° | < 55° |
| IIa | Physiological immaturity < 3 months | 50–59° | 55–77° |
| IIb | Delayed ossification, immaturity > 3 months | 50–59° | 55–77° |
| III | [clarify] | [clarify] | [clarify] |
| IV | [clarify] | [clarify] | [clarify] |
Clinical Interpretation
The distinction between types IIa and IIb is based on the patient's age: up to 3 months, α values within 50–59° are interpreted as physiological immaturity, whereas maintaining the same values after 3 months is considered delayed ossification. Specific criteria for types III–IV and the corresponding treatment strategy are not provided in the given excerpts [clarify].
Frequently asked questions
What α angle corresponds to a mature joint?
For a mature joint (type Ia and Ib), the α angle is > 60° with β < 55°.
How do types IIa and IIb differ?
Type IIa is physiological immaturity under 3 months (α 50–59°, β 55–77°); type IIb is delayed ossification with immaturity over 3 months with the same angle values.
Which angle is more important — α or β?
According to the source, the β angle is less critical than the α angle.
What is the correct term for the pathology?
The preferred term is developmental dysplasia of the hip (DDH); the term congenital dysplasia of the hip (CDH) is considered less accurate.
Are criteria for types III and IV provided?
The criteria for angles and management for types III and IV are not specified in the provided excerpts [clarify].