This examination shows a good morphology of the bony acetabular roof with a sharp angular bony rim.
Normal acetabular roof angle.
At birth it should be less than 28 degrees and should progressively reduce with maturation of the hip.
Derived from a line drawn along the lateral bony margin of the ilium and from a line drawn across the bony acetabular roof.
Angles above 47º are seen in patients with acetabular.
In type 2 dysplasia the angulation of the roof may be less than 10 but the roof is short providing less coverage of the femoral head.
First a line is drawn running through the medial.
A hilgenreiner line connects the inferior tips of the iliac bones at the triradiate cartilage.
This line is used to measure the acetabular angle and as a reference for perkin line.
The acetabular index also called acetabular roof angle or tönnis angle is a radiographic measurement of femoral head bony coverage by the acetabulum it is useful in assessing for developmental dysplasia of the hip ddh as well as pincer morphology in femoroacetabular impingement fai.
B perkin line is perpendicular to hilgenreiner line touching the lateral margin of the acetabular roof.
3 4 roof arc angle is a method to evaluate adequate acetabular coverage and stability of the femoral head matta and merritt study based on clinical findings.
Acetabular fracture involving superior weight bearing area shows significantly poor results.
The acetabular angle is a plain film measurement used when evaluating developmental dysplasia of the hip ddh which is measured between hilgenreiner s line and a line parallel to the acetabular roof.
There is nice coverage of the femoral head by the cartilaginous roof and the labrum.
The angle should become progressively shallower with age and should measure less than 22º at and beyond 1 year of age.
The alpha angle is above the 60 degrees and the beta angle is way below 55 degrees.
An acetabular index or roof angle of less than 10 is normal but more than 10 15 is considered dysplastic with higher risks of instability see graphic above.
No problem here in depicting the lateral rim of the bony roof of the acetabulum.
The acetabular angle using hilgenreiner s line should be less than 28º at birth.
Values for bony acetabular roof angle and percentage femoral head cover in a selective ultrasound neonatal hip screening programme.
Acetabular version is measured as the angle between a line connecting the anterior acetabular margin with the posterior acetabular.
This leads to four quadrants and a normal femoral head has to be located in the inferomedial quadrant.
Type 2 dysplasia short roof.
Normal values in children.
It is measured on ap pelvic radiograph.
Normal values in adults.
Standing lateral radiograph normal.
The normal range is 33º to 38º.
The acetabular version angle is influenced by pelvic obliquity and pelvic tilt which might lead to measurement errors if not considered 1 2 it is also influenced by physeal closure and with increasing distance from the acetabular roof 3.
