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% 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 indications nondisplaced fractures with stable prosthesis operative antegrade intramedullary nail indications supracondylar fracture proximal to the femoral component (Su Type I) retrograde intramedullary nail technical considerations at least 2 distal interlocking screws (rotational stability) use end cap to lock most distal screw if available femoral component may cause starting point to be more posterior than normal and lead to hyperextension at the fracture site nail must be inserted deep enough (not protrude) to not abrade on patella/patellar component indications intact/stable prosthesis with open-box design to accommodate nail fracture proximal to femoral component (Su Type I) fracture that originates at the proximal femoral component and extends proximally (Su Type II) ORIF with fixed angle device indications intact/stable prosthesis Lewis-Rorabeck II or Su Types I or II that are unable to accommodate intramedullary devices (i.e. closed box PS implants or stemmed TKA implants) fracture distal to flange of anterior femoral component (Su Type III) can be combined with retrograde IMN to allow for earlier weight bearing techniques condylar buttress plate (non-locking) does not resist varus collapse locking supracondylar / periarticular plate polyaxial screws allow screws to be directed into best bone before locking into plate, and can avoid femoral component blade plate / dynamic condylar screw difficult to get adequate fixation around PS implants complications nonunion increased risk in plating via extensile lateral approach compared with submuscular approach malunion increased risk with minimally-invasive approach/MIPO revision to a long stem prosthesis indications loose femoral component Lewis-Rorabeck III or Su Type III (described above) with poor bone stock distal femoral replacement indications elderly patients with loose (Su type III) or malpositioned components and poor bone stock advantages immediate weight-bearing decreased operative time of procedure no difference in major complications or reoperation rate vs ORIF 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 indications nondisplaced fracture with stable prosthesis operative ORIF indications unstable fracture with stable prosthesis long-stem revision prosthesis indications displaced fractures with loose tibial component 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 indications stable implants with intact extensor mechanism non-displaced fractures operative indications loose patellar component extensor mechanism disruption techniques (indications for each have not been clearly defined) ORIF with or without component revision partial patellectomy with tendon repair patellar resection arthroplasty and fixation total patellectomy