DDH Radiology

DDH radiology measurements is essential in diagnosis the developmental dysplasia of the hip after the age of 6 months.

All the parameters should be determined on the AP pelvic radiograph with the legs in the neutral position and the knees pointing forward. Up to 10-15° of knee flexion is allowed.

DDH Radiology Parameters

There are many parameters that can be determined on the AP pelvic radiograph, these are:

Hilgenreiner Line (Y-Line)

The Hilgenreiner line is a horizontal line drawn across the lowest points of both iliac wings, tangent to the inferolateral edge of the ilium above the triradiate cartilage.

It serves as a reference line for various measurements used in the detection and classification of hip dysplasia.

See Also: Developmental Dysplasia of the Hip

Perkins Line

The Perkins line is drawn perpendicular to the Hilgenreiner and passes through the most lateral point of the acetabular roof.

It is used to determine various parameters for evaluating hip dysplasia.

Shenton Line:

Aline traced along the medial aspect of the femoral neck and the superior border of the obturator foramen normally forms a smooth, unbroken arc called the Shenton Menard line.

When the hip is dislocated, the arc is broken because the femoral neck occupies an abnormally high position (as it also does in Perthes disease).

An externally rotated position of the lower limb will also cause a break in the Shenton Menard line.

Calve line:

The calve line is a curved line drawn along the Lateral border of the iliac wing, the superior acetabular rim to the femoral neck. It should form a smooth, uniform arc.

If the proximal femur creates a break or bulge in the line, this is considered evidence that the hip is dislocated.

Tonnis Grades of Hip Dislocation

The Hilgenreiner and Perkins lines divide the hip joint into four quadrants.

The four grades of hip dislocation are based on the position of the femoral head ossification center in relation to the four quadrants.

Grade of dislocation	Findings
Grade I	Normal findings. The capital femoral ossification center is medial to the Perkins line
Grade II	Dislocation. The capital femoral ossification center is lateral to the Perkins line and below the superior acetabular rim (lower outer quadrant)
Grade III	Dislocation. The capital femoral ossification center is lateral to the Perkins line and is at the level of the superior acetabular rim
Grade IV	Complete high dislocation. The capital femoral ossification center is lateral to the Perkins line and above the superior acetabular rim

See Also: Developmental Dysplasia of the Hip Risk Factors

Acetabular Index (AC Angle of Hilgenreiner)

The acetabular index is the angle formed by the Hilgenreiner line and a line tangent to the acetabular roof. The tangent appears as a straight line passing through the inferior edge of the ilium and the lateral rim of the acetabulum.

The acetabular index is age dependent. It should be less than 25° in patients older than 6 months.

Newborns	Angle ≈ 27.5 degrees
At 6 months of age	Angle ≈ 23.5 degrees
2 years of age	Angle ≈ 20 degrees

References & More

1. Tönnis D, Brunken D. Eine Abgrenzung normaler und pathologischer Hüftpfannendachwinkel zur Diagnose der Hüftdysplasie. Auswertungen von 2294 Pfannendachwinkeln kindlicher Hüftgelenke [Differentiation of normal and pathological acetabular roof angle in the diagnosis of hip dysplasia. Evaluation of 2294 acetabular roof angles of hip joints in children]. Arch Orthop Unfallchir. 1968;64(3):197-228. German. doi: 10.1007/BF02171260. PMID: 5730180.
2. Tonnis D, et al. Hiiftluxation und Huftkopfnekrose. Eine Sammelstatistik des Arbeitskreises fur Huftdysplasie. Bucherei des Orthopaden, Vol. 21. Stuttgart: Enke, 1978
3. Tonnis D. Die angeborene Huftdysplasie und Huftluxation im Kindes- und Erwachsenanalter. Chapter 9: Allgemeine Rontgendiagnostik des Huftgelenks. Berlin: Springer; 1984; 129-134