The Patellotrochlear Index (PTI) is an index used for assessing patellar height. This is helpful for identification of patella alta.
Exam: MRI of the knee, sagittal view
Parameters:
(1) distance between (the most superior aspect of the trochlear articular surface) to (most inferior aspect of patellar articular cartilage)
(2) distance between (the most superior aspect of articular cartilage of the patella) to (the most inferior aspect of the articular cartilage), measured on the posterior aspect of the patella
patellotrochlear index =
= (distance 1) / (distance 2)
Interpretation:
• The index ranges from 0.03 and 0.60, with most patients in the range 0.10 to 0.40.
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