Fractures Around a Knee Replacement (Dr)

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
  • Treatment
    • nonoperative
      • casting or bracing
        • indications
          • nondisplaced fractures with stable prosthesis
    • operative
      • antegrade intramedullary nail
        • indications
          • supracondylar fracture proximal to the femoral component
      • retrograde intramedullary nai
        • 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
          • fracture that originates at the proximal femoral component and extends proximally
      • ORIF with fixed angle device
        • indications
          • intact/stable prosthesis
          • fracture distal to flange of anterior femoral component
        • 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
          • Poor bone stock
      • distal femoral replacement 
        • indications
          • elderly patients with loose 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
  • 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