TKA Periprosthetic Fracture

Introduction

Categories of TKA periprosthetic fractures
- location
  - distal femur periprosthetic fractures
  - proximal tibia periprosthetic fracture
  - patellar fractures
- 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
      - 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 (described above) unable to accommodate intramedullary device
      - fracture distal to flange of anterior femoral component (Su Type III)
    - 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

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

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

Distal periprosthetic femur fracture non-union in a 60F (C101087)

Open Periprosthetic Tibial Fracture in an 84F (C2898)

periprosthetic supracondylar femur fx (C1179)