Patella tangential projection

Question 1

• Name the 2 methods used to demonstrate the tangential projection of the patella

Answer 1

Settigast method, and merchant method.

Question 2

Describe how the patient is positioned for each one.

Answer 2

Settigast - the patient is seated or prone, knee flexed as much as possible, patella perpendicular to IR, typically a 15-20 degree tube angle, centered at patellar femoral joint.

Merchant method - Patient is seated, bilateral image, SID is 6ft to decrease magnification, femur parallel to table and tib fib on an angle, flex knee 40 degrees, angle tube 30 degrees caudad from horizontal, center midway between patella at level of patellar femoral joint.