Periprosthetic Fractures in Total Knee Replacement (TKR)

Introduction

• Definition: A fracture is considered periprosthetic if the fracture line lies within 15 cm of the knee joint or within 5 cm of an intramedullary stem.
• Incidence: 0.3-1.1% after primary TKA; rises to 2.5-8% after revision TKA.
• Most affected bone: Distal femur (most common) > Proximal tibia > Patella.
• Typical patient: Elderly women, mean age 70-80 years, low-energy mechanism.
• Mortality: 6% at 30 days, 18% at 6 months, 25% at 1 year (comparable to hip fracture mortality).

Etiology and Risk Factors

Patient Factors

Surgical / Technical Factors

Anatomy of Periprosthetic Fractures in TKR

         DISTAL FEMUR              TIBIA                PATELLA
        ___________             ___________            _______
       |           |           |           |          |       |
       |  Femoral  |           |  Tibial   |          |Patella|
       |Component  |           | Component |          |Comp.  |
    ---+---+---+---+---     ---+---+---+---+---       +---+---+
       |   |   |   |           |   |   |   |
    Supracondylar  |           |   Stem    |
    Region         |           |   Region  |
       |      Stem tip         |Distal shaft

Classification Systems

1. DISTAL FEMORAL PERIPROSTHETIC FRACTURES

A. Lewis and Rorabeck Classification (1997) - Most Widely Used

┌──────────────────────────────────────────────────────┐
│         LEWIS AND RORABECK CLASSIFICATION            │
│                                                      │
│  TYPE I   │  Non-displaced fracture                  │
│           │  Component INTACT (well-fixed)           │
│           │  ████████████████████░░░░░               │
│           │  [Fracture line, no displacement]        │
├───────────┼──────────────────────────────────────────┤
│  TYPE II  │  DISPLACED fracture (>2mm)               │
│           │  Component INTACT (well-fixed)           │
│           │  ████████████████░░░░░░░░░░              │
│           │  [Gap/step at fracture site]             │
├───────────┼──────────────────────────────────────────┤
│  TYPE III │  Displaced OR undisplaced fracture       │
│           │  Component LOOSE or FAILING              │
│           │  [Requires revision arthroplasty]        │
└──────────────────────────────────────────────────────┘

B. Su and Associates Classification (Based on fracture location relative to anterior flange)

┌─────────────────────────────────────────────────────┐
│            SU CLASSIFICATION                        │
│                                                     │
│   TYPE I   Fracture PROXIMAL to femoral component   │
│            ─────────────── fracture line            │
│                ┌─────────┐                          │
│                │ Femoral │                          │
│                │  Comp.  │                          │
│                                                     │
│   TYPE II  Fracture originates AT proximal aspect   │
│            of femoral component, extends proximally │
│            ──┬──────────── fracture line            │
│              │┌─────────┐                           │
│              └│ Femoral │                           │
│               │  Comp.  │                           │
│                                                     │
│   TYPE III Any part of fracture line is DISTAL to   │
│            upper edge of anterior flange            │
│                ┌─────────┐                          │
│               ─┤ Femoral ├─ fracture line           │
│                │  Comp.  │                          │
└─────────────────────────────────────────────────────┘

• Type I and II: ORIF
• Type III: Revision arthroplasty (fracture involves or is distal to the anterior flange - cannot be bridged with standard fixation)

C. DiGioia and Rubash Classification (1991)

2. PERIPROSTHETIC TIBIAL FRACTURES

Felix and Associates Classification (1997)

┌──────────────────────────────────────────────────────────┐
│           FELIX CLASSIFICATION - TIBIAL PPF              │
│                                                          │
│                 ┌──────────┐                             │
│                 │  Tibial  │ TYPE I: Tibial plateau      │
│   TYPE I ───>   │  Plateau │ (at implant level)          │
│                 │  Comp.   │                             │
│                 ├──────────┤                             │
│   TYPE II ──>   │  Stem    │ Adjacent to prosthetic stem │
│                 │  region  │                             │
│                 │          │                             │
│   TYPE III ─>   │  Distal  │ Distal to tibial stem       │
│                 │  shaft   │                             │
│                 └──────────┘                             │
│   TYPE IV:  Fracture of the TIBIAL TUBERCLE              │
│                                                          │
│  Each type further classified by implant stability:      │
│  A = Component WELL-FIXED                                │
│  B = Component LOOSE                                     │
│  C = INTRAOPERATIVE fracture                             │
└──────────────────────────────────────────────────────────┘

3. PERIPROSTHETIC PATELLAR FRACTURES

A. Ortiguera and Berry Classification (Most Clinically Useful)

┌──────────────────────────────────────────────────────────┐
│        ORTIGUERA AND BERRY CLASSIFICATION                │
│                                                          │
│  TYPE I    Extensor mechanism INTACT                     │
│            Patellar component STABLE                     │
│            → Non-operative treatment                     │
│                                                          │
│  TYPE II   Extensor mechanism DISRUPTED                  │
│            Component STABLE or LOOSE                     │
│            → Surgical repair of extensor mechanism       │
│                                                          │
│  TYPE IIIa Extensor mechanism INTACT                     │
│            Component LOOSE                               │
│            Bone stock ADEQUATE (thickness ≥10 mm)        │
│            → Component revision                          │
│                                                          │
│  TYPE IIIb Extensor mechanism INTACT                     │
│            Component LOOSE                               │
│            Bone stock POOR (<10 mm / comminuted)         │
│            → Patellectomy or custom implant              │
└──────────────────────────────────────────────────────────┘

B. Goldberg Classification

Unified Classification System (UCS) - Current Preferred System

UCS DECISION ALGORITHM

Step 1: Location
        ↓
   Does fracture involve bone SUPPORTING the implant?
   YES → involves host-implant construct
   NO  → distant from implant
        ↓
Step 2: Implant fixation status
        ↓
   Is implant WELL-FIXED or LOOSE?
        ↓
Step 3: Bone stock quality
        ↓
   ADEQUATE or INSUFFICIENT?

Clinical Presentation

• History: Low-energy fall, twisting injury in an elderly patient with pre-existing TKA
• Symptoms: Sudden knee/thigh pain, inability to weight bear, deformity
• Signs: Swelling, ecchymosis, shortening/rotation, tenderness at fracture site
• Red flags: Prior loosening symptoms (start-up pain, worsening pain), recent infection

Investigations

Radiological Assessment

1. Plain X-rays (first line): AP and lateral views of knee AND full-length femur/tibia
   • Assess: fracture pattern, displacement, angulation, implant position, signs of loosening (radiolucent lines >2 mm, cement fracture, component migration)
2. CT scan: For complex fractures, intraoperative fractures, to assess bone stock, rotational alignment
3. MRI: Limited use due to implant artifact; useful for stress fractures, soft tissue assessment
4. Bone scan: Detect occult fractures, differentiate loosening from fracture

Key Radiographic Signs of Implant Loosening

• Continuous radiolucent line at cement-bone interface
• Progressive subsidence or migration of component
• Cement mantle fracture
• De-bonding of cement from implant

Management

General Principles - Decision Making Algorithm

PERIPROSTHETIC FRACTURE AROUND TKR
              │
              ▼
   ┌─────────────────────┐
   │  Is implant STABLE? │
   └─────────────────────┘
          │               │
         YES              NO
          │               │
          ▼               ▼
   OSTEOSYNTHESIS    REVISION ARTHROPLASTY
   (ORIF / IMN)      (± Distal Femoral
                      Replacement)
          │
          ▼
   Is fracture DISPLACED?
          │               │
         YES              NO
          │               │
          ▼               ▼
    Surgical fixation   Non-operative
    (ORIF/IMN)         if suitable

Management of Distal Femoral PPF

NON-OPERATIVE TREATMENT

• Indications: Non-displaced fractures (Type I Lewis/Rorabeck), medically unfit patients
• Methods: Cast/splint immobilization, traction
• Disadvantages: High non-union rate, muscle wasting, DVT risk, loss of knee motion
• Rarely used as primary treatment due to poor outcomes in elderly

OPERATIVE TREATMENT - ORIF Options

RETROGRADE NAIL IN DISTAL FEMORAL PPF

        ─────────────────────────
        Fracture site
     ───┼───────────────────────
        │   Retrograde nail
        │   inserted through
        │   femoral box
        ▼
        ┌─────────┐
        │ Femoral │  ← Nail must pass through
        │ Comp.   │    intercondylar notch
        └─────────┘

• Best for: Type I & II fractures (Su), implant with open box (cruciate-sacrificing designs)
• Advantages: Load sharing, early mobilization, minimal soft tissue stripping
• Disadvantages: Cannot use if posterior-stabilized (PS) implant with closed box; limited distal purchase in very distal fractures
• Contraindicated in PS/constrained implants without adequate intercondylar space

LISS PLATE IN DISTAL FEMORAL PPF

        ════════════════════════ ← Locking plate
        ■ ■ ■  ║║║║║║║║║║║║║║║  (lateral aspect)
        ─────────────────────── ← Fracture site
        ■ ■ ■  
               ┌─────────┐
               │ Femoral │
               │ Comp.   │
               └─────────┘
        ← Locked screws cannot cross prosthetic stem
          but can be placed around it

• Best for: All displaced fractures with stable implant; especially Su Type III where nail cannot reach
• Advantages: Minimally invasive, no reaming, angular stability, good in osteoporotic bone
• Technique: Locked screws inserted around the prosthetic stem (unicortical in stem zone, bicortical proximally)
• Dual plating: Increasingly used for comminuted/osteoporotic fractures (medial + lateral plates)

• Older technique, requires larger incision, less favored now
• Useful when IM nail not feasible

OPERATIVE TREATMENT - REVISION ARTHROPLASTY

• Loose/failing implant (Type III Lewis/Rorabeck; Type B2/B3 UCS)
• Su Type III fractures with distal fragments too small for fixation
• Very comminuted fractures with insufficient bone for fixation
• Failed prior ORIF
• Pre-existing implant malposition or malalignment

1. Revision TKA with stems: Uses press-fit intramedullary stems to bypass fracture
2. Distal Femoral Replacement (DFR): Oncologic-type tumor implant
   • Best for severely comminuted fractures, bone loss, elderly patients
   • Allows immediate mobilization
   • Higher risk of infection, extensor mechanism issues
3. Hinged total knee prosthesis: For ligamentous instability combined with fracture

Management of Tibial PPF

FELIX CLASSIFICATION - TREATMENT GUIDE

Felix Type Ia (plateau, stable component)     → ORIF
Felix Type Ib (plateau, loose component)      → Revision TKA
Felix Type Ic (intraoperative)                → Immediate ORIF
Felix Type IIa (stem adjacent, stable)        → Cast/brace if non-displaced; ORIF if displaced
Felix Type IIb (stem adjacent, loose)         → Revision with long-stem tibial component
Felix Type IIIa (distal shaft, stable)        → ORIF (plate/nail)
Felix Type IIIb (distal shaft, loose)         → Long-stem revision TKA
Felix Type IVa (tibial tubercle, stable)      → ORIF
Felix Type IVb (tibial tubercle, loose)       → Revision

• Locked plates with screws placed around/adjacent to the tibial stem provide best fixation
• Long-stemmed tibial components bypass the fracture zone in revision cases

Management of Patellar PPF

ORTIGUERA-BERRY - TREATMENT GUIDE

Type I  (intact mechanism, stable component)  → NON-OPERATIVE
                                                 (cylinder cast 6 wks)

Type II (disrupted mechanism, any component)  → SURGICAL REPAIR of extensor mechanism
                                                 (ORIF, wire tension band, fragment excision)

Type IIIa (loose component, adequate bone)   → COMPONENT REVISION / ORIF

Type IIIb (loose component, poor bone)       → PATELLECTOMY or
                                                 Custom implant reconstruction

Specific Complications

Prevention

1. Surgical technique: Avoid anterior femoral notching - use femoral sizing guides correctly; if notch occurs, consider prophylactic plating
2. Implant selection: Avoid posterior-stabilized box in osteoporotic bone if nail fixation may be needed later
3. Bone management: Address osteoporosis peri-operatively (bisphosphonates, calcium, Vitamin D)
4. Early detection: Vigilant follow-up X-rays for early loosening; stress fractures can progress
5. Fall prevention: Physiotherapy, walking aids, home hazard assessment
6. Cement technique: Adequate cementation reduces stress risers

Post-Operative Rehabilitation

• After ORIF: Partial weight-bearing for 6-12 weeks; passive ROM exercises early; progress to full weight-bearing at radiological union
• After Revision/DFR: Immediate full weight-bearing often possible; early mobilization critical in elderly to prevent complications
• Physiotherapy: Quadriceps strengthening, gait re-education, proprioception training
• Monitoring: Serial X-rays at 6 weeks, 3 months, 6 months, 1 year

Summary Algorithm

┌─────────────────────────────────────────────────────────────────┐
│           MANAGEMENT SUMMARY - PPF AROUND TKR                  │
│                                                                 │
│  DISTAL FEMORAL PPF                                             │
│  ├─ Type I (undisplaced, stable implant)  → Brace/Cast         │
│  ├─ Type II (displaced, stable implant)                        │
│  │   ├─ Su I/II, open box → Retrograde IMN                     │
│  │   ├─ Su I/II, closed box → Locking Plate (LISS)             │
│  │   └─ Su III            → Locking Plate or Revision TKA      │
│  └─ Type III (loose implant) → Revision TKA ± DFR              │
│                                                                 │
│  TIBIAL PPF                                                     │
│  ├─ Stable component, non/minimally displaced → Conservative   │
│  ├─ Stable component, displaced → ORIF (locking plate)         │
│  └─ Loose component             → Revision TKA (long stem)     │
│                                                                 │
│  PATELLAR PPF                                                   │
│  ├─ Intact extensor, stable component → Conservative           │
│  ├─ Disrupted extensor mechanism → Surgical repair             │
│  └─ Loose component + poor bone → Patellectomy                 │
└─────────────────────────────────────────────────────────────────┘

Recent Evidence (2024-2026)

• Dual-plate fixation of periprosthetic distal femur fractures (Andring et al., J Orthop Trauma 2024) shows promise for comminuted osteoporotic fractures
• A 2026 systematic review (Zagra et al., EFORT Open Rev, PMID 42227259) addresses management of infected periprosthetic fractures, highlighting the complexity of simultaneous infection and fracture management
• Robot-assisted TKA is associated with a small but recognized risk of periprosthetic fractures at pin placement sites (systematic review, J Robot Surg 2026, PMID 42009908)

Conclusion

1. Classification of fracture (location, displacement)
2. Assessment of implant stability (most critical decision point)
3. Assessment of bone stock quality ...guides management toward either ORIF (stable implant) or revision arthroplasty (loose implant, poor bone). Early mobilization - especially in elderly patients - is the key goal of surgical treatment, as prolonged immobilization carries its own mortality risk.