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The Double-Patella Sign: A Patellar Implant Loosening Case Report
Maximillian P Ganz1, Angelo Mannino2, Giles R Scuderi1,2
1Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, Hempstead, New York.
Case:
A 79-year-old man status post total knee arthroplasty (TKA) sustained atraumatic nondisplaced fracture of the inferior pole of the patella 1 year postoperatively. The patient had full radiographic healing and clinical resolution. Two years after injury, the patient reported new-onset knee pain and was found to have atraumatic inferior migration of the patellar component. The lateral radiograph appeared to demonstrate 2 patellae, coined "the double-patella sign."
Conclusion:
Nondisplaced patellar fractures after TKA should be monitored even after full osseous healing for component loosening. Inferior migration of a loose patellar component can mimic 2 patellae on the lateral radiograph, mimicking a double patella.

