summary TKA Periprosthetic Fractures are a complication of knee arthroplasty that may involve the distal femur, the proximal tibia, or the patella. Diagnosis can be made with plain radiographs. CT can be helpful in surgical planning to assess for bone stock. Treatment can be nonoperative or operative depending on location of fracture, implant stability, available bone stock, and patient comorbidities. Epidemiology Anatomic location distal femur periprosthetic fractures proximal tibia periprosthetic fracture patellar fractures Etiology Timing intraoperative medial femoral condyle fracture most common postoperative Risk factors (general) poor bone quality age steroid use rheumatoid arthritis stress-shielding mechanical stress-risers screw holes local osteolysis stiffness neurological disorders epilepsy Parkinson's disease cerebellar ataxia myasthenia gravis polio cerebral palsy Distal Femur Periprosthetic Fractures Incidence 0.3%-2.5% recent literature suggests the medial femoral condyle is the most commonly fractured structure intraoperatively Believed to be secondary to incomplete sagittal cuts between the intercondylar notch and the medial femoral condyle Fracture specific risk factors anterior femoral notching (debatable) mismatch of elastic modulus between metal implant and femoral cortex rotationally constrained components Classification systems Lewis and Rorabeck is most commonly used Neer and Associates (1967) Type I Nondisplaced (<5 mm displacement and/or <5 degrees angulation) Type II Displaced > 1 cm Type IIa Displaced > 1 cm with lateral femoral shaft displacement Type IIb Displaced > 1 cm with medial femoral shaft displacement Type III Displaced and comminuted DiGioia and Rubash (1991) Group I Extra-articular, non-displaced (<5 mm and/or <5 degrees angulation) Group II Extra-articular, displaced (>5 mm and/or >5 degrees angulation) Group III Loss of cortical contact or angulated (10 degrees); may have intercondylar or T-shaped component Chen and Associates Classification (1994) Type I Nondisplaced Type II Displaced and/or comminuted Lewis and Rorabeck Classification (1997) Type I Nondisplaced; component intact Type II Displaced: component intact Type III Displaced; component loose or failing Su and Associates' Classification of Supracondylar Fractures of the Distal Femur Type I Fracture is proximal to the femoral component Type II Fracture originates at the proximal aspect of the femoral component and extends proximally Type III Any part of the fracture line is distal to the upper edge of anterior flange of the femoral component Treatment nonoperative casting or bracing login to view 2 more bullets operative antegrade intramedullary nail login to view 2 more bullets retrograde intramedullary nail login to view 9 more bullets ORIF with fixed angle device login to view 18 more bullets revision to a long stem prosthesis login to view 3 more bullets distal femoral replacement login to view 6 more bullets Tibial Periprosthetic Fractures Incidence 0.4%-1.7% Fracture specific risk factors prior tibial tubercle osteotomy component loosening component malposition insertion of long-stemmed tibial components Classification Felix and Associates' Classification of Periprosthetic Fractures of the Tibia Associated with TKA Type I Fracture of tibial plateau Type II Fracture adjacent to tibial stem Type III Fracture of tibial shaft, distal to component Type IV Fracture of tibial tubercle Treatment nonoperative casting or bracing login to view 2 more bullets operative ORIF login to view 2 more bullets long-stem revision prosthesis login to view 2 more bullets Patellar Periprosthetic Fractures Incidence 0.2%-21% in resurfaced patella 0.05% in unresurfaced patella Fracture specific risk factors patellar osteonecrosis asymmetric resection of patella inappropriate thickness of patella implant related central single peg implant uncemented fixation metal backing on patella inset patellar component Classification Goldberg Classification Type I Fracture not involving implant/cement interface or quadriceps mechanism Type II Fracture involving implant/cement interface and/or quadriceps mechanism Type III Type A: inferior pole fracture with patellar ligament rupture Type B: inferior pole fracture without patellar ligament rupture Type IV All types with fracture dislocations Ortiguera and Berry Classification of Postoperative Periprosthetic Patella Fractures Extensor Mechanism Component Type I Intact Stable Type II Disrupted Stable or loose Type IIIa Intact Loose, reasonable bone stock (patellar thickness ≥10 mm) Type IIIb Intact Loose, poor bone stock (<10 mm, marked comminution) Treatment nonoperative casting or bracing in extension login to view 3 more bullets operative indications login to view 2 more bullets techniques (indications for each have not been clearly defined) login to view 4 more bullets