New MRI Measurement of Patellar Height in Knee Extension - IES-EV Control Study

The measurement of the patellar height is essential to decide and quantify the surgical correction to be made. The classic index is that of Cato and Deschamps. It has the advantage of its simplicity, with the measurement on a simple profile radiograph of the ratio between the distance from the patella to the tibia and the length of the patella. However, it has the disadvantage of measuring this height in relation to the tibia when the dislocation is located at the level of the patello-trochlear joint. The MRI index of sagittal patellar engagement on the trochlea (IES), described in 2012, does not have this drawback but it does not appear to be reliable: its value depends, in fact, on the flexion of the knee. This flexion, required by the MRI, is variable and is not specified by the radiologist. It is due to the use of an "antenna" that surrounds and lifts the knee.The hypothesis of the study is that it is possible to determine and validate a new IES, in knee extension and therefore reproducible, thanks to the measurement of knee flexion on MRI. The precise value of this flexion can allow a virtual correction of the original IES to obtain, by mathematical calculation, the new IES in virtual extension.

Inclusion Criteria:Subject, male or female, over 18 years oldSubject with an MRISubject without patellar pathology, in particular without patellar instabilitySubject having been informed and not objecting to the use of his dataExclusion Criteria:None