Fractures After Total Knee Replacement

Introduction:

Fracture occurring around a Knee which has undergone Total Knee Replacement are called Periprosthetic Fractures. Although not very commonly seen, Fractures in a prosthetic Knee have been reported in international literature. Fractures of Femur, Tibia and Patella can all occur following injury to the prosthetically replaced Knee.

Periprosthetic Fractures involving Femur

Risk Factors: 

  • Femoral notching done during the Total Knee Replacement
  • Osteoporosis
  • Osteonecrosis of Femur

Investigations: 

X-rays:
Anterior-Posterior views, lateral views and oblique views are all required.

Conservative Management: 

Non-operative treatment is avoided, except in patients with excessive comorbidity. This may include traction or plaster cast.

Surgical Management: 

The Fractures can be fixed by retrograde nailing of the Femur Fracture or by fixation with a plate and screws.

Periprosthetic Fractures involving the Tibia

These Fractures usually involve the Medial or Lateral Condyle of the Tibia.

Risk Factor: 

Osteoporosis

Investigations: 

X-rays: Anterior Posterior Views and Lateral Views

Conservative Management: 

  • No role of Conservative Management

Surgical Management: 

  • Removal of the original Tibia tray.
  • Fixing a Fracture with screws and using bone graft if required.
  • If the fragment cannot be fixed then a step cut is done for the Tibia and the step is replaced by metal wedge on the Tibial tray.

Periprosthetic Fracture involving the Patella 

Risk Factors: 

  • Not leaving adequate Patella after shaving (Patella left behind is less than 12mm)
  • Use of central pegged implant
  • Devascularization of Patella after a lateral retinacular release
  • Excessively thick Patella
  • Component malalignment

Investigations: 

Lateral X-rays:
Fracture may be missed if undisplaced
Bone Scan:
If strongly suspected Fracture due to anterior Knee Pain and not visible on X-ray.

Conservative Management: Indicated in the following

  • Intact extensor mechanism
  • Patellar component is in place
  • No comminution
  • Displacement is < 2 cm

Conservative management involves immobilization in a plaster cast from groin to ankle for a period of 6 weeks, after which Knee is mobilized with the help of continuous passive movement machine.

Surgical Management: 

This involves partial or complete Patellectomy depending upon whether the component is in place.
Partial Patellectomy: If component is in place.
Complete Patellectomy : If component is loose.