Radiological landmarks,
lines and angles with explanatory notes on their importance are presented on the following:
Shenton's line Fig 15.
Projection Anteroposterior view (AP)
Description This is an imaginary curvilinear smooth and continuous line drawn from the inferior border of the superior pubic ramus along the inferomedial border of the neck of femur.
Indication Developmental dysplasia of the hip (DDH) and fractured neck of femur.
Tear drop distance Fig 3
Projection AP
Description The pelvic teardrop is a U-figure that results from the end-on projection of the bony ridge running along the floor of the acetabulum.
Teardrop distance is defined as the distance between the teardrop line and the most medial aspect of the femoral head.
It should be less than 11mm and demonstrate less than 2mm asymmetry when compared to the contralateral side.
Indication Joint effusion in and slipped upper femoral epiphyses in children.
Ileopectineal line Fig 15.
Projection AP
Description Defines the anterior column of the pelvis.
It runs along the medial border of the iliac wing,
along the superior border of the superior pubic ramus to the pubic symphysis.
Indication Disruption suggests anterior column fracture.
Ilioischial line Fig 15.
Projection AP
Description Defines the posterior column of the pelvis and runs from the medial border of the iliac wing along the medial border of the ischium to the ischial tuberosity.
Indication Disruption suggests posterior column fracture.
Hilgenreiner line Fig 5.
Projection AP
Description A horizontal line drawn through both triradiate cartilages.
Indication Developmental dysplasia of the hip (in conjunction with Perkins line and acetabular angle).
Perkins (Perkins-Omberdanne line) Fig 5.
Projection AP
Description A vertical line drawn perpendicular to the Hilgenreiner line at the most lateral aspect of the acetabular roof.
Indication Development dysplasia of the hip.
Acetabular angle Fig 4 and 8.
Projection AP
Description The angle between Hilgenreiner line and a line drawn parallel to the acetabular roof.
The angle decreases with age. Angles greater than 30 degrees after 4mo of age suggest acetabular dysplasia or neuromuscular disorders.
Shallow acetabuli are seen in Down syndrome and achondroplasia.
Indication: Useful for diagnosis and follow up of DDH patients
Klein's line Fig 6 and 7
Projection AP
Description A diagonal line drawn along the neck of femur,
which should intersect the lateral femoral epiphysis.
Indication Slipped upper femoral epiphysis.
Lateral centre edge angle of Wiberg Fig 9 and 10
Projection AP
Description Angle between a vertical line drawn through the centre of the femoral head and the centre of the femoral head to the superolateral acetabulum. This should be between 25-40 degrees.
In adult patients with over coverage of the femoral head, this angle exceeds 40 degrees.
Indication To assess acetabular coverage of femoral head in children with previous developmental dysplasia of the hip.
Femoral neck angle(Caput-collum-diaphyseal angle (CCD angle)
Fig 11,12 and 13
Projection AP
Description The angle formed between straight lines drawn through the axis of the femoral neck and shaft.
The normal angle should be approximately 125 degrees.
Coxa vara refers to an angle less than 120 degrees and coxa valga refers to an angle more than 130 degrees.
Indication To demonstrate hip alignment.
Skinners line Fig 14
Projection AP
Description A vertical line is drawn through the mid femoral shaft and a second line is drawn at right angles and tangential to the tip of the greater trochanter.
The fovea capitis should lie above or at the level of the trochanteric line.
Indication If the fovea capitis passes below the trochanteric line than abnormality of the hip joint,
such as fracture or coxa vara should be considered.
Tonnis angle (weight bearing acetabular index)
Projection AP
Description Angle formed between the lines that run from the medial edge of the sourcil horizontally and a line that runs tangentially between the medial to lateral sourcil.
Indication Measures inclination of weight bearing zone (acetabular roof) and is therefore an indirect marker for femoral incongruence.