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Published on: September 29, 2023
Patellar morphology is different in patellofemoral instability: An MRI comparative case-control study
Clara Thouvenin1, Julien Erard2, Assala Abu Mukh3
1Orthopaedics Surgery and Sports Medicine Department, FIFA Medical Center of Excellence, Croix-Rousse Hospital, Lyon University Hospital, Lyon, France; Orthopaedic Surgery Department, Bordeaux University Hospital, Bordeaux, France.
Patellar morphology significantly differs in patients with recurrent patellofemoral instability (PFI). A wider lateral facet, narrower medial facet, flatter patella, and medialized crest contribute to PFI, highlighting the patella
Area of Science:
- Orthopedics and Sports Medicine
- Radiology and Medical Imaging
- Biomechanics
Background:
- Recurrent patellofemoral instability (PFI) is a common orthopedic condition affecting the knee joint.
- While femoral and patellar factors contribute to PFI, the specific role of patellar morphology has been underexplored in existing literature.
- Understanding patellar morphology is crucial for a comprehensive approach to PFI management.
Purpose of the Study:
- To evaluate distinct patellar morphology patterns identified on MRI in patients with recurrent PFI.
- To establish the contribution of these patellar morphological variations to the development of PFI.
- To compare patellar morphology between individuals with PFI and a control group.
Main Methods:
- Retrospective analysis of patellar MRI and X-ray data from 2018-2022.
- Comparison of 50 knees with recurrent PFI against 50 matched control knees (ACL reconstruction candidates without PFI history).
- Assessment of key indices including Caton-Deschamps' index, Wiberg's patellar morphotype, Dejour's trochlear dysplasia classification, and sagittal patellofemoral engagement index, alongside detailed patellar cartilage and bone measurements.
Main Results:
- Patients with PFI exhibited a significantly wider lateral facet (p=0.019) and narrower medial facet (p<0.001) compared to controls.
- The subchondral patellar crest was significantly medialized in the PFI group (p<0.001).
- While cartilaginous crest measurements showed no significant difference, the PFI group presented a wider Wiberg angle (p<0.001), indicating a flatter patellar surface.
Conclusions:
- Patellar morphology in PFI patients is characterized by a wider lateral facet, narrower medial facet, flatter surface, and a medialized patellar crest.
- A medialized patellar crest may increase patellar tilt, potentially destabilizing the patellar-trochlear groove congruence in PFI.
- PFI is multifactorial, involving both trochlear and patellar contributions; future research and clinical evaluation should incorporate patellar morphotype analysis.
