Recent study results revealed that trochlear dysplasia types on an axial view based on Dejour classification are not representative of the entire trochlear geometry. Therefore, multiple axial planes should be used clinically to more accurately describe the entire shape of the trochlear.
Investigators assessed 90 knees from 81 patients with patellar instability and 15 knees from 10 healthy volunteers. They used MRIs to create 3D knee models. They defined femoral trochlear planes as virtual cross sections. The reference plane was the femoral trochlear plane 0 (FTP 0), which included the proximal edge of the femoral trochlea. Researchers assessed trochlear dysplasia types at every 10° of FTP 10 up to FTP 60. A normal trochlear had a sulcus angle less than 145°. Investigators assessed changes in trochlear type based on the FTPs and agreement with clinical classification.
They noted 86 knees in patients with patellar instability and 12 knees in healthy volunteers demonstrated changes in the trochlear types based on different FTPs. The patterns of change were different among patients with patellar instability and the healthy volunteers, which demonstrated morphological variation in the dysplastic trochleae. In patients with patellar instability, the agreement of trochlear type on each FTP with Dejour classification was 42% on FTP 10, 49% on FTP 20, 33% on FTP 30, 22% on FTP 40, 22% on FTP 50% and 22% on FTP 60. In healthy volunteers, the agreement of classification type was 20% at FTP 10, 80% at FTP 20 and 100% on FTP 30 through FTP 60.
These results showed trochlear type in the clinically used plane may not always match the trochlear types on planes that describe contact surface of the patella. – by Monica Jaramillo
Disclosure: The researchers report no relevant financial disclosures.