Periprosthetic patella fractures are very rare overall (1.19% of all knee replacements [TKR]) [14]. However, they represent a serious complication after primary TKR or even after endoprosthetic revision surgery. A periprosthetic patella fracture is rarely associated with direct trauma but often occurs atraumatically during treatment [4]. This complication occurs most frequently after implantation of a retropatellar joint replacement [2, 4, 17, 19, 21]. The pathogenesis is multifactorial, and predisposing risk factors have been described [4, 19, 24, 25]. Two classification systems are known for describing fractures [11, 17]. Nonoperative treatment is possible for undisplaced, stable fractures and stable implant positioning. Surgical intervention is recommended as soon as the extensibility of the affected knee joint is impaired or implant loosening occurs [4, 11, 17, 19, 21, 24, 25]. The previously high complication rates can be significantly reduced through the further development of osteosynthesis procedures, especially angle-stable plate systems.
