Indications for imaging
Trauma, congenital abnormalities, rheumatology.
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Anatomy Demonstrated
The first metacarpal and trapezium.
Rt Thumb PA Anatomy
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Basic Patient Position
The PA position is easiest for the patient however the AP
projection produces less magnification and better detail as the
thumb is in contact with the cassette.
PA Position,
The patient sits alongside the end of the table elbow flexed
palm downwards, or at the end of the table with he elbow flexed
at 90 degrees, the hand is rotated into the true later position projecting
the thumb clear of superimposition with the fifth metacarpal.
AP Position, The patient stand with their back to the table and
the arm is extended and internally rotted to bring the palmar
aspect of the thumb facing upwards, adjust the table height to a
comfortable position, adjust the rotation of the arm to bring
the thumb into true AP position.
Rt Thumb PA Patient Position
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Radiation protection
Direct lead rubber gonad protection using a "half
apron".
Ensure the lower limbs and torso are not below the table top in
the primary beam.
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Central Ray
The vertical central ray is directed to the center of the1st
metacarpophalangeal joint.
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Exposure Factors
| Kv |
mAS |
FFD (cm) |
Grid |
Focus |
AEC |
Cassette |
| 60 |
4 |
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, distally the tip of the distal
phalanx, proximally the trapezium, the skin surface externally
and the 2nd metacarpal medially.
The thumb should be projected true AP with equal concavity on
either side of the 1st metacarpal.
The joint spaces should be open.
Exposure, adequate penetration to visualise all bone detail and
low enough contrast to visualise the soft tissues.
Rt Thumb PA Radiograph
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Related Projections
Thumb Lat.
Wrist for carpal bones
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Additional modalities
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