Classification of congenital (congenital) hip dysplasia by sonography (ultrasound) according to R. Graf.
| Type | Description | Alpha angle | Beta angle | Measures and therapy |
| Type I – Normally developed and mature hip. | ||||
| Ia | Any age: normally developed hip. With pointed cartilaginous notch. | > 60° | < 55° | No therapy. |
| Ib | Any age: normally developed hip. With blunt cartilaginous notch. | > 60° | > 55° | No therapy. Control should or can be done. |
| Type II – Maturation delay of the hip (dysplasia). | ||||
| IIa (+) | Until 3 months of age: physiological delay of hip development. Without maturation deficit of bones. | 50°-59° | > 55° | No therapy. But control necessary. |
| IIa (-) | Until 3 months of age: physiological delay of hip development. With maturation deficit of bones. | 50°-59° | > 55° | Control at short intervals. Spread treatment. |
| IIb | After 3 months of age: true maturation delay (delayed bone maturation). | 50°-59° | 55°-70° | Spreading treatment required. |
| IIc | Hip at risk or critical. Hip is luxatable. | 43°-49° | 70°-77° | Immediate spreading treatment. Without treatment, the dysplasia will worsen. |
| D(IId) | Hip begins to decenter. | 43°-49° | > 77° | Immediate spreader treatment. Secure immobilization (for example, spreader cast) required. |
| Type III – Decentered hip joints (dysplasia with malalignment). | ||||
| IIIa | Upward shifted cartilaginous oriel without alteration of the same. | < 43° | > 77° | |
| IIIb | Upward shifted cartilaginous oriel with alteration of the same. | < 43° | > 77° | |
| Type IV – Complete hip dislocation (severe dysplasia with severe deformity). | ||||
| IV | Complete dislocation. | < 43° | > 77° | Immediate treatment mandatory. Inpatient admission to a hospital. Correction of hip position. Immobilization with plaster cast. |
