What are the classification and treatment guidelines for a patient with a periprosthetic fracture after total knee arthroplasty (TKA)?

Periprosthetic Fracture After TKA: Classification and Treatment Guidelines

Treatment of periprosthetic fractures after TKA must be guided by a systematic classification that evaluates fracture location, prosthesis stability, bone quality, and fracture reducibility—with the primary goal of restoring function and minimizing mortality in this elderly, high-risk population.

Epidemiology and Risk Factors

Periprosthetic fractures occur in 0.3-2.5% of TKA patients, typically presenting 2-4 years post-operatively in elderly patients with poor bone stock 1. The distribution by location is:

• Supracondylar distal femur fractures: Most common (86% of cases) 1, 2
• Tibial fractures: 8% of cases, strongly associated with loose components and malalignment 1, 2
• Patellar fractures: Rare (6% of cases), associated with rheumatoid arthritis, steroid use, osteonecrosis, and malalignment 1, 2

Most fractures occur following low-energy trauma in osteopenic patients 1.

Classification Systems

Femoral Periprosthetic Fractures: Modified Classification

The most clinically useful classification system stratifies treatment based on prosthesis stability, bone stock quality, and fracture reducibility 3, 4:

• Type I: Good bone stock + stable, well-positioned prosthesis

  • Type IA: Nondisplaced or easily reducible → Conservative treatment or plate/nail fixation 3, 4
  • Type IB: Irreducible → Open reduction and internal fixation required 3

• Type II: Good bone stock + reducible fracture BUT loose or malpositioned components → Revision arthroplasty 3, 4

• Type III: Poor bone stock + loose or malpositioned components (regardless of reducibility) → Distal femoral replacement with stemmed components 3, 2

Tibial Periprosthetic Fractures: Felix Classification

The Felix classification guides tibial fracture management 4:

• Type A and C (stable implant): Plate fixation or intramedullary nailing 4
• Type B (loose prosthesis): Hinged revision arthroplasty 4

Patellar Fractures: Pattern-Based Approach

• Transverse fractures: Associated with patellar maltracking, often require surgical stabilization 1, 5
• Vertical fractures: Typically occur through fixation holes, may require surgical intervention 1, 5

Diagnostic Imaging Algorithm

Initial Evaluation

Radiographs are the mandatory first-line imaging and must include the entire prosthesis plus surrounding bone 1. Standard views include anteroposterior, lateral, and axial projections 6.

Advanced Imaging for Surgical Planning

• CT without contrast: Use when assessing component stability, measuring axial malrotation, or evaluating bone stock for revision planning 1, 6, 7
• MRI with metal artifact reduction: Reserve for detecting radiographically occult fractures or assessing soft tissue complications 1, 6
• Bone scan: Can detect occult fractures but requires 48-72 hours in osteopenic patients; avoid isolated interpretation within 1-2 years post-TKA due to normal postoperative uptake 1

Treatment Algorithm

Step 1: Assess Prosthesis Stability

This is the most critical decision point. Loose or malpositioned components mandate revision surgery regardless of fracture pattern 3, 4, 2.

Step 2: Evaluate Bone Stock Quality

• Good bone stock + stable prosthesis → Internal fixation viable 3, 4
• Poor bone stock + any component loosening → Revision with stemmed components 3, 2

Step 3: Select Fixation Method (for stable prostheses)

Plate fixation (preferably polyaxial locking systems):

• Indicated for most fractures around stable implants 4, 8
• Minimally invasive plating reduces soft tissue complications 4
• Allows fixation around intramedullary implants 4

Retrograde intramedullary nailing:

• Only feasible with open box TKA designs 4
• Suitable for Rorabeck Type I-II fractures 4

Revision arthroplasty with stemmed components:

• Mandatory for loose prostheses (Rorabeck III, Felix B) 4, 2
• Consider for far distal fractures, severe comminution, or inability to achieve stable fixation 2

Step 4: Reduction Technique Selection

• Open technique: Direct reduction for simple fracture patterns 4
• Mini-open technique: Direct reduction with cerclage/lag screws + percutaneous plating for OTA 32/33-A1 fractures 4
• Minimally invasive: Indirect reduction with percutaneous fixation for all other patterns 4

Outcomes and Complications

• Fracture union rate: 87% within 6 months with appropriate treatment 8
• Failure of fixation: 21% require reoperation for technical failures 8
• Mortality: 3% perioperative mortality in elderly cohorts 8
• Functional recovery: 68% return to pre-injury activity level 8
• Revision surgery demonstrates superior knee society scores compared to fixation in patients with poor bone stock 2

Critical Pitfalls to Avoid

• Never attempt internal fixation with loose components—this guarantees failure and necessitates revision 3, 4
• Do not rely on isolated bone scans within 2 years of TKA—normal postoperative uptake mimics fracture 1
• Avoid inadequate imaging—radiographs must include entire prosthesis and sufficient proximal/distal bone 1
• Recognize that instability (7.5% of failures) is closely linked to fracture risk—address component malposition during revision 6, 7
• Early mobilization is essential—prolonged immobilization increases mortality in elderly patients; allow partial weight-bearing with frames for 6 weeks post-fixation 4