ISAKOS: 2019 Congress in Cancun, Mexico

2019 ISAKOS Biennial Congress ePoster #1445


Classification of Dysplastic Femoral Trochlea Depends on Evaluation Plane in Patients with Patellar Instability

Yuzo Yamada, MD, PhD, Yao, Osaka JAPAN
Yukiyoshi Toritsuka, MD, PhD, Nishinomiya, Hyogo JAPAN
Norimasa Nakamura, MD, PhD, Osaka, Osaka JAPAN
Shuji Horibe, MD, PhD, Habikino, Osaka JAPAN
Tomoki Mitsuoka, MD, Kashiba City, Nara JAPAN
Kazuomi Sugamoto, MD, PhD, Suita, Osaka JAPAN
Hideki Yoshikawa, MD, PhD, Suita, Osaka JAPAN
Konsei Shino, MD, PhD, Osaka, Osaka JAPAN

Yao Municipal Hospital, Yao, Osaka, JAPAN

FDA Status Not Applicable


Classification of Dysplastic Femoral Trochlea Depends on Evaluation Plane



Trochlear dysplasia is a major predisposing factor of patellar instability (PI). Dysplasia types are generally evaluated on one axial plane using Dejour classification, but it is unclear whether this classification covers the entire spectrum.


To evaluate trochlear types on multiple axial planes in patients with patellar instability and healthy volunteers, and to show changes of dysplastic femoral trochlear types and their agreement with clinical classification.
Study Design: Descriptive laboratory study.


Ninety knees from 81 patients with PI and 15 knees from 10 healthy volunteers (HV) were evaluated. Three-dimensional (3D) computer-generated knee models were created by magnetic resonance imaging (MRI) scans obtained at 10° of knee flexion. The femoral trochlear planes (FTPs) were defined as virtual cross-sections including the trans-epicondylar axis (TEA). FTP 0 was defined as the reference plane including the proximal edge of the femoral trochlea and FTP ? as the plane making optional angle ? to FTP 0. Trochlear dysplasia type according to Dejour classification was evaluated on FTP 10, 20, 30, 40, 50 and 60. A trochlea with a sulcus angle <145° was defined as normal. Changes of trochlear types according to FTPs were evaluated and agreement with clinical classification was evaluated.


Downgrading of dysplasia was observed as FTPs moved distally, but patterns of change varied among PI patients and HV. Eighty-seven (97%) knees in patients with PI and 12 (80%) in HV showed changing trochlear types in different FTPs while three (3%) knees in patients with PI and three (20%) in HV consistently presented a normal trochlea from FTP 10 to FTP 60. This suggested that one axial image could not represent the entire trochlear type. Overall agreement of trochlear type on each FTP was 38% on FTP 10, 41% on FTP 20, 31% on FTP 30, 20% on FTP 40, 20% on FTP 50 and 21% on FTP 60 in patients with PI, and 20% at FTP 10, 80% at FTP 20, and 100% on FTP 30 through FTP 60 in HV.


Dejour classification of trochlear dysplasia type differed among axial evaluation planes, and changes in the types varied among individuals.