The radiographs protocol consists in AP weight bearing of pelvis and modified Dunn which is the prefered projection for the authors.
Consists in patient supine with pelvis in neutral rotation,then the hip is flexed 90° and abducted 20°,
while pelvis remains in neutral rotation.
The centering point is the midpoint between the anterior superior iliac spine and the pubic symphysis,angulated 10º cephalic.
The collimation is laterally to proximal third of femur,
superiorly to anterior superior iliac spine,
inferiorly to crease of buttock and medially to midline.
The result is a perfect view from the femoral neck profile,
bilaterally,
enabling a good comparison of both hips and it provides a clear view from the head-neck junction.
In normal AP weight bearing view,
this findings could be unclear because of different postural patient stand,
anatomical varieties or pelvic different angles.
Also,
the femoroacetabular impingement findings are located in the anterior part of the femur neck and along the femoral neck-head head transition,
which is most of the times unclear in this projection.
Fig. 1: Lateral perspective of modified Dunn projection
References: CHP
Fig. 2: Perspective from above of modified Dunn projection
References: CHP
The authors show an example of a 31 year old man,
ex-footballer with recurrent hip pain.
At the physical examination we was not able to abduct his hip and had an internal and external rotation hip limitation.
Fig. 3: AP weight bearing projection of pelvis
In the AP weight bearing Pelvis projection it is unclear to characterize completely the femoroacetabular impingement.
Fig. 4: Modified Dunn projection
Using the authors modified projection,
it was easy to identify the femoroacetabular impingement,
not only in the left hip,
but in both,
as it was given a clear view from the head-neck junction