Trochlear facet asymmetry (FA) refers to the condition of the medial facet being abnormally small if compared to the lateral facet in trochlear dysplasia 1.
On this page:
Images:
Usage
Facet asymmetry is also used as a measurement in magnet resonance imaging for trochlear dysplasia to make it more objective 1-3, this concept was adapted from axial radiographs 3.
Measurement
One option to measure facet asymmetry is the ratio between medial versus lateral trochlear facet length calculated as (medial facet) / (lateral facet) 1. Another option is to calculate it the other way around, that is (lateral facet) / (medial facet) 2.
Facet asymmetry is traditionally measured 3 cm above the joint line 1,3.
Interpretation
A threshold of <0.4 or 40% was suggestive of trochlear dysplasia and showed a sensitivity and specificity of 100% and 96% in that study 2.
History and etymology
The principle has been adapted for magnetic resonance imaging by Pfirrmann 1.
Unable to process the form. Check for errors and try again.