Graf method for ultrasound classification of developmental dysplasia of the hip

The Graf method for ultrasound classification system for developmental dysplasia of the hip (DDH) in infants describes both alpha and beta angles.

As a general rule, the alpha angle determines the type, and the beta angle determines the subtype. The angle is formed by the acetabular roof to the vertical cortex of the ilium and thus reflects the depth of the bony acetabular roof. This corresponds to 90° minus the acetabular angle. 

Classification

The descriptions used in the Graf method assume the standard projection is an ultrasound image of the hip that is set up as a vertical right hip AP view.

• type I

  • centered hip

  • alpha angle >60° (normal)

    • type Ia: beta angle <55°

    • type Ib: beta angle >55°

• type II

  • centered hip

  • type IIa (physiologically immature): alpha angle 50-59° (<3 months)

  • type IIb: alpha angle 50-59° (>3 months)

  • type IIc 

    • alpha angle 43-49° 

    • beta angle <77°​

• type D ("about to decentre")

  • alpha angle 43-49°

  • beta angle >77°

• type III 

  • decentred hip

  • alpha angle: not measured in a decentred hip

  • cartilage roof pushed partly upwards (cephalad), partly downwards (caudal)

  • perichondrium goes upward (ultrasound image set as right hip AP) 

    • type IIIa: no echos in cartilaginous roof

    • type IIIb: echos in cartilaginous roof due to structural alteration and damage

• type IV

  • decentred hip

  • alpha angle: not measured in a decentred hip

  • cartilage roof pushed entirely downwards (cephalad)

  • perichondrium goes horizontal (ultrasound image set as right hip AP) 

  • the hyaline cartilage of the lateral edge of the acetabulum along with fibrocartilaginous labrum is interposed between the femoral head and the acetabulum

History and etymology

Both the beta angle and the alpha angles were originally described by Reinhard Graf in 1980 ¹.