Indications for imaging
Trauma, Congenital abnormalities and Patella pathologies e.g.,
chondromalacea patella.
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Anatomy Demonstrated
The patella is projected at right angles to the
lateral projection and demonstrates linear fractures and especially
the posterior articular surface.
Patella Axial Rt "skyline" Anatomy
Meschan, I. 1955 An Atlas of Normal Radiographic Anatomy
Saunders, London
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Basic Patient Position
The patient sits on the table with the long axis of the leg
in line with the long axis of the table, the affected limb is
flexed to bring the internal angle to 45 degrees, the tibia and
fibula are in line with the femur.
Patella Axial Rt "skyline" Patient Position
Meschan, I. 1955 An Atlas of Normal Radiographic Anatomy
Saunders, London
There are several variations to this projection
in position of the patient for minimising radiation dose to the
gonads by avoiding directing the central ray in line with the
rest of the body and comfort and ease of performing the
examination.
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Radiation protection
Direct lead rubber gonad protection using a "half
apron".
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Central Ray
The central ray is angled 45 degrees cranially and centered tot
he palpable apex of the patella.
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Exposure Factors
| Kv |
mAS |
FFD (cm) |
Grid |
Focus |
AEC |
Cassette |
| 65 |
5 |
100 |
No |
Fine |
No |
18 x 24 cm |
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Evaluation of the Image
ID and markers must be present and correct in the appropriate
area of the film
Evidence of collimation on four sides equally around the
centering point.
Limits of the examination, superiorly the skin surface superior
to the patella, inferiorly the anterior femoral condyles,
laterally and medially the skin margins.
The intercondylar groove and the patella should be viewed in
profile , the patella femoral joint space should be projected
with no superimposition of the patella on the femur.
Optimal exposure should penetrate all the bone structures and
contrast should be low enough to visualise fully the bone and
soft tissue structures.
Patella Axial Rt "skyline" Radiograph
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Related Projections
Knee AP, Lateral, oblique patella projections.
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Additional modalities
CT
MRI
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