PATHOLOGICAL FRACTURES - FEMUR
Metastatic Disease | Mirels' Score | IMN vs Arthroplasty | Palliative Treatment
MIRELS' SCORE (IMPENDING FRACTURE)
Critical Must-Knows
- Mirels' score ≥8 = prophylactic fixation recommended (≥9 = 33% fracture risk at 6 months, ≥10 = 50% risk)
- Life expectancy over 3-6 months = surgery beneficial (use Katagiri or PATHFx score to estimate)
- Surgical principles: Fix normal bone to normal bone, bypass lesion by ≥2 cortical diameters, cement augmentation, construct must outlast patient
- IMN for diaphyseal lesions, arthroplasty for periarticular - cemented implants for immediate stability
- Postoperative radiation essential - 30 Gy in 10 fractions at 2-3 weeks postop for local control
Examiner's Pearls
- "Mirels' score ≥8 = prophylactic fixation - Site (1-3), Pain (1-3), Lesion (1-3), Size (1-3)
- "Most common primaries: Breast, Lung, Prostate, Kidney, Thyroid (BLT with Kosher Pickle - BL P K T)
- "Fix normal bone to normal bone, bypass lesion by ≥2 cortical diameters, cement augmentation for lytic lesions
- "Nonunion common (30-40%) but not problematic if construct stable - durable fixation more important than biological healing
Critical Pathological Fracture Exam Points
Mirels' Score ≥8
Mirels' score ≥8 = prophylactic fixation recommended - Score ≥9 = 33% fracture risk within 6 months, ≥10 = 50% risk. Calculate: Site (UL 1, LL 2, peritroch 3), Pain (mild 1, mod 2, functional 3), Lesion (blastic 1, mixed 2, lytic 3), Size (under 1/3 cortex 1, 1/3-2/3 is 2, over 2/3 is 3).
Life Expectancy Estimation
Life expectancy over 3-6 months = surgery beneficial - Use Katagiri or PATHFx score. Factors: primary tumor type (breast/prostate better than lung/melanoma), visceral mets, multiple bone mets, performance status. If under 3 months, consider non-operative.
Surgical Principles
Fix normal bone to normal bone, bypass lesion by ≥2 cortical diameters, cement augmentation for lytic lesions, construct must outlast patient - IMN for diaphyseal, arthroplasty for periarticular. Allow immediate weight bearing.
Postoperative Radiation
Postoperative radiation essential - 30 Gy in 10 fractions at 2-3 weeks postop. Provides local control and pain relief. Coordinate with radiation oncology. Nonunion common (30-40%) but not problematic if construct stable.
Pathological Fractures - Quick Decision Guide
| Scenario | Mirels' Score | Life Expectancy | Treatment |
|---|---|---|---|
| Impending fracture | ≥8 | over 3-6 months | Prophylactic fixation |
| Complete fracture | N/A | over 3-6 months | IMN or arthroplasty |
| Diaphyseal lesion | Any | over 3-6 months | IMN + cement |
| Periarticular lesion | Any | over 3-6 months | Arthroplasty (cemented) |
SPLSMirels' Score Components
Memory Hook:SPLS: Site (1-3), Pain (1-3), Lesion (1-3), Size (1-3) - Score ≥8 = prophylactic fixation!
BLT K PMost Common Primaries
Memory Hook:BLT K P: Breast, Lung, Thyroid, Kidney, Prostate - most common primaries metastasizing to bone!
FIXSurgical Principles
Memory Hook:FIX: Fix normal to normal, Involve bypass ≥2 diameters, X-ray (cement) augmentation!
Overview and Epidemiology
Pathological fractures of the femur occur through bone weakened by disease (most commonly metastatic cancer). Treatment is palliative - goal is to restore function, relieve pain, and improve quality of remaining life. Surgery is indicated if life expectancy over 3-6 months and Mirels' score ≥8 for impending fractures.
Most Common Primary Tumors
BLT with Kosher Pickle (BL P K T):
- Breast: Most common (lytic or blastic)
- Lung: Lytic metastases
- Prostate: Blastic metastases
- Kidney: Lytic metastases (hypervascular)
- Thyroid: Lytic metastases
Lytic vs Blastic:
- Lytic: Lung, kidney, thyroid, breast, melanoma (weaken bone)
- Blastic: Prostate, breast (may be mixed)
- Mixed: Breast (can be both)
Palliative Treatment
Pathological fracture treatment is palliative, not curative - goal is to restore function, relieve pain, and improve quality of remaining life. Surgery beneficial if life expectancy over 3-6 months. Construct must outlast patient (median survival 6-12 months, so fixation must last 12-24 months minimum).
Epidemiology
- Incidence: 5-10% of patients with bone metastases develop pathological fractures
- Location: Femur most common (proximal femur 50%, shaft 30%, distal 20%)
- Age: Peak 50-70 years (cancer population)
- Gender: Depends on primary tumor (breast = female, prostate = male)
- Laterality: Usually unilateral, but bilateral possible
Anatomy and Pathophysiology
Femoral Anatomy
The femur:
- Proximal: Head, neck, greater/lesser trochanter
- Shaft: Diaphyseal region
- Distal: Condyles, metaphysis
- Blood supply: Endosteal and periosteal
Metastatic involvement:
- Proximal femur: 50% of pathological fractures (weight-bearing, high stress)
- Shaft: 30% (diaphyseal lesions)
- Distal: 20% (metaphyseal lesions)
Pathophysiology
Metastatic spread:
- Hematogenous: Tumor cells spread via bloodstream
- Bone tropism: Certain tumors prefer bone (breast, prostate, lung, kidney, thyroid)
- Lytic vs blastic: Depends on primary tumor type
Bone destruction:
- Lytic lesions: Osteoclast activation destroys bone (weakened cortex)
- Blastic lesions: Osteoblast activation forms abnormal bone (may be weaker)
- Mixed lesions: Combination of both
Fracture mechanism:
- Normal bone: Requires high energy
- Pathological bone: Low energy (pathological fracture) or normal activity (impending fracture)
- Location: Proximal femur most vulnerable (weight-bearing, high stress)
Tissue Diagnosis Essential
If no known primary cancer, MUST obtain tissue diagnosis before surgery - treating undiagnosed lesion as metastasis when it's actually primary bone sarcoma is catastrophic error. Use CT-guided biopsy or open biopsy following oncologic principles.
Classification Systems
Mirels' Score for Impending Fracture
Site:
- Upper limb: 1 point
- Lower limb: 2 points
- Peritrochanteric: 3 points
Pain:
- Mild: 1 point
- Moderate: 2 points
- Functional (affects activities): 3 points
Lesion type:
- Blastic: 1 point
- Mixed: 2 points
- Lytic: 3 points
Size:
- Less than 1/3 cortex: 1 point
- 1/3 to 2/3 cortex: 2 points
- Over 2/3 cortex: 3 points
Interpretation:
- Score ≥8: Prophylactic fixation recommended
- Score ≥9: 33% fracture risk within 6 months
- Score ≥10: 50% fracture risk within 6 months
Mirels' score guides prophylactic fixation decisions.
Clinical Assessment
History
Cancer history:
- Primary tumor: Type, stage, treatment history
- Metastases: Known bone metastases, visceral metastases
- Systemic therapy: Chemotherapy, radiation, immunotherapy
- Performance status: ECOG or Karnofsky score
Fracture history:
- Mechanism: Low energy (pathological) or normal activity (impending)
- Pain: Location, severity, functional impact
- Function: Ambulatory status, weight-bearing ability
Physical Examination
Inspection:
- Deformity (if complete fracture)
- Swelling
- Skin condition (previous radiation, surgical scars)
Palpation:
- Tenderness over lesion/fracture
- Crepitus (if complete fracture)
- Soft tissue mass (if large tumor)
Range of Motion:
- Hip ROM (if proximal)
- Knee ROM (if distal)
- Pain with movement
Neurovascular Status:
- Distal pulses and sensation
- Motor function
Clinical Examination Key Point
Assess performance status and goals of care - surgery is palliative. If patient is bedbound with weeks to live, surgery may not benefit. If ambulatory with months to live, surgery can restore function and improve quality of life.
Associated Conditions
- Visceral metastases: Liver, lung, brain
- Other bone metastases: Multiple skeletal lesions
- Systemic therapy: Ongoing chemotherapy
- Radiation: Previous radiation to affected area
Investigations
Standard X-ray Protocol
Views: AP and lateral femur (full length).
Key findings:
- Fracture: Complete or impending (lytic lesion)
- Lesion characteristics: Lytic, blastic, or mixed
- Size: Assess cortical destruction (Mirels' score)
- Location: Proximal, shaft, or distal
Full-length views essential - assess entire femur for other lesions.
Management Algorithm
Management Pathway
Pathological Fracture Management
Confirm metastatic disease (history, imaging, biopsy if needed). Stage with CT chest/abdomen/pelvis. Estimate life expectancy (Katagiri or PATHFx score). Calculate Mirels' score if impending fracture.
If life expectancy over 3-6 months and Mirels' score ≥8 (impending) or complete fracture, proceed with surgery. If under 3 months, consider non-operative (palliative care).
Diaphyseal lesion: IMN + cement augmentation. Periarticular lesion: Arthroplasty (cemented). Fix normal bone to normal bone, bypass lesion by ≥2 cortical diameters.
Postoperative radiation essential - 30 Gy in 10 fractions at 2-3 weeks postop. Provides local control and pain relief. Coordinate with radiation oncology.
Surgical Technique
Intramedullary Nailing
Indications:
- Diaphyseal lesions (shaft)
- Proximal or distal shaft lesions
Technique:
- Long nail: From proximal to distal metaphysis
- Bypass lesion: Minimum 2 cortical diameters (4x bone diameter) beyond lesion
- Interlocking: Both ends (static locking)
- Cement augmentation: Inject PMMA through cortical window at lesion site
- Cement timing: After nail insertion (or before - cement first technique)
Advantages:
- Less invasive
- Allows immediate weight bearing
- Good stability
IMN is gold standard for diaphyseal pathological fractures.
Tumor Spillage
Minimize tumor spillage during surgery - use gentle handling, copious irrigation. If open approach, consider curettage through limited window. Postoperative radiation provides local control, but minimizing spillage reduces risk.
Complications
| Complication | Incidence | Risk Factors | Prevention/Management |
|---|---|---|---|
| Nonunion | 30-40% | Tumor progression, radiation | Not problematic if construct stable |
| Fixation failure | 10-15% | Inadequate bypass, no cement | Bypass ≥2 diameters, cement augmentation |
| Local recurrence | 20-30% | Inadequate radiation | Postoperative radiation essential |
| Periprosthetic fracture | 5-10% | Tumor progression, short implant | Long implant, bypass lesion widely |
| Infection | 5-10% | Immunosuppression, radiation | Prophylactic antibiotics, careful technique |
Nonunion
30-40% incidence:
- Cause: Tumor progression, radiation, poor bone quality
- Prevention: Not applicable (expected with pathological fractures)
- Management: Not problematic if construct stable - durable fixation more important than biological healing. Nonunion acceptable if patient comfortable and functional.
Fixation Failure
10-15% incidence:
- Cause: Inadequate bypass of lesion, no cement augmentation, tumor progression
- Prevention: Bypass lesion by ≥2 cortical diameters, cement augmentation, long implant
- Management: Revision fixation or conversion to arthroplasty
Local Recurrence
20-30% incidence:
- Cause: Inadequate radiation, tumor progression
- Prevention: Postoperative radiation essential (30 Gy in 10 fractions)
- Management: Additional radiation or surgical revision if symptomatic
Postoperative Care
Immediate Postoperative
- Immobilization: None (early mobilization)
- Weight bearing: Immediate weight bearing as tolerated (construct designed for this)
- ROM: Early hip/knee ROM (immediate)
- PT: Ambulation training, strengthening
Rehabilitation Protocol
Weeks 0-2:
- Weight bearing as tolerated
- Ambulation training
- Hip/knee ROM exercises
- Pain management
Weeks 2-4:
- Postoperative radiation: 30 Gy in 10 fractions (2-3 weeks postop)
- Continue ambulation
- Progressive activity
Weeks 4-12:
- Full activity as tolerated
- Continue monitoring
- Systemic therapy (if indicated)
Return to Function
Goals:
- Pain relief
- Restore ambulation
- Improve quality of life
- Maintain function until death
Timeline: Immediate weight bearing - goal is rapid return to function.
Outcomes and Prognosis
Overall Outcomes
Surgical fixation outcomes:
- Success rate: 80-90% (pain relief, function restoration)
- Functional outcomes: 70-80% return to ambulation
- Complications: 20-30% (nonunion, failure, recurrence)
Median survival:
- Overall: 6-12 months (varies by primary tumor)
- Breast/prostate: 12-24 months (better prognosis)
- Lung/melanoma: 3-6 months (poorer prognosis)
Functional Outcomes
Return to ambulation:
- Timeline: Immediate (weight bearing as tolerated)
- Rate: 70-80% return to ambulation
- Factors: Performance status, life expectancy, rehabilitation
Pain relief:
- Immediate: 80-90% pain relief with surgery
- Long-term: Maintained with radiation
- Factors: Tumor type, radiation response
Long-Term Prognosis
Survival:
- Depends on primary tumor: Breast/prostate better than lung/melanoma
- Visceral metastases: Poorer prognosis
- Multiple bone metastases: Poorer prognosis
Local control:
- With radiation: 70-80% local control
- Without radiation: 50-60% local control
- Recurrence: 20-30% (may require additional treatment)
Factors Affecting Outcomes
Positive factors:
- Good performance status
- Longer life expectancy (over 6 months)
- Single or few bone metastases
- Responsive to systemic therapy
Negative factors:
- Poor performance status
- Short life expectancy (under 3 months)
- Multiple bone metastases
- Visceral metastases
- Poor response to systemic therapy
Prevention and Return to Sport
Prevention
Primary prevention:
- Early detection and treatment of primary cancer
- Systemic therapy for metastatic disease
- Bisphosphonates or denosumab (prevent skeletal-related events)
Secondary prevention (after diagnosis):
- Monitor bone metastases with imaging
- Calculate Mirels' score for impending fractures
- Prophylactic fixation if score ≥8
Return to Function
Goals (palliative):
- Pain relief
- Restore ambulation
- Improve quality of life
- Maintain function until death
Timeline: Immediate - goal is rapid return to function, not return to sport.
Evidence Base
Mirels' Score
- Score ≥8 = prophylactic fixation recommended
- Score ≥9 = 33% fracture risk within 6 months
- Score ≥10 = 50% fracture risk within 6 months
Life Expectancy Estimation
- Life expectancy estimation using validated score
- Surgery beneficial if life expectancy over 3-6 months
- Factors: primary tumor, visceral mets, bone mets, performance status
Surgical Principles
- Fix normal bone to normal bone
- Bypass lesion by ≥2 cortical diameters
- Cement augmentation for lytic lesions
- Construct must outlast patient
Postoperative Radiation
- Postoperative radiation provides local control
- Reduces local recurrence from 50-60% to 20-30%
- Timing: 2-3 weeks postoperatively
Nonunion in Pathological Fractures
- Nonunion common (30-40%) but not problematic if construct stable
- Durable fixation more important than biological healing
- Nonunion acceptable if patient comfortable and functional
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
Scenario 1: Impending Fracture with Mirels' Score 9
"A 60-year-old woman with known breast cancer and bone metastases presents with increasing right thigh pain. She has difficulty walking due to pain. X-ray shows a large lytic lesion in the femoral shaft involving 70% of the cortex. The lesion is in the lower limb, and she has moderate pain that affects her activities."
Scenario 2: Complete Pathological Fracture Proximal Femur
"A 65-year-old man with known prostate cancer and multiple bone metastases presents after a fall. He has a complete pathological fracture through the proximal femur with femoral head and neck involvement. He is otherwise healthy and ambulatory. CT shows blastic metastases throughout skeleton but no visceral metastases."
MCQ Practice Points
Mirels' Score Threshold
Q: What Mirels' score indicates prophylactic fixation? A: Score ≥8 - Mirels' score ≥8 = prophylactic fixation recommended. Score ≥9 = 33% fracture risk within 6 months, ≥10 = 50% risk. Components: Site (1-3), Pain (1-3), Lesion (1-3), Size (1-3).
Life Expectancy
Q: What is the minimum life expectancy for surgery to be beneficial in pathological fractures? A: 3-6 months - Surgery beneficial if life expectancy over 3-6 months. Use Katagiri or PATHFx score to estimate. If under 3 months, consider non-operative (palliative care).
Surgical Principles
Q: What are the key surgical principles for pathological fractures? A: Fix normal bone to normal bone, bypass lesion by ≥2 cortical diameters, cement augmentation for lytic lesions, construct must outlast patient - IMN for diaphyseal, arthroplasty for periarticular. Allow immediate weight bearing.
Most Common Primaries
Q: What are the most common primary tumors metastasizing to bone? A: Breast, Lung, Prostate, Kidney, Thyroid (BLT with Kosher Pickle - BL P K T) - Breast most common. Lytic: lung, kidney, thyroid. Blastic: prostate. Mixed: breast.
Postoperative Radiation
Q: What is the postoperative radiation protocol for pathological fractures? A: 30 Gy in 10 fractions at 2-3 weeks postop - Provides local control and pain relief. Reduces local recurrence from 50-60% to 20-30%. Essential for local control. Coordinate with radiation oncology.
Nonunion
Q: What is the nonunion rate in pathological fractures? A: 30-40% - Nonunion common but not problematic if construct stable. Durable fixation more important than biological healing. Nonunion acceptable if patient comfortable and functional.
Australian Context
Clinical Practice
- Pathological fractures common in cancer patients
- Multidisciplinary approach (orthopaedics, medical oncology, radiation oncology, palliative care)
- Mirels' score used for prophylactic fixation decisions
- Postoperative radiation standard protocol
Healthcare System
- Public hospitals handle most cases
- Private insurance covers procedures
- Radiation therapy accessible through public/private
Orthopaedic Exam Relevance
Pathological fractures are a common viva topic. Know that treatment is palliative (not curative), Mirels' score ≥8 = prophylactic fixation, life expectancy over 3-6 months = surgery beneficial, surgical principles (fix normal to normal, bypass ≥2 diameters, cement augmentation), IMN for diaphyseal vs arthroplasty for periarticular, and postoperative radiation essential. Be prepared to discuss Mirels' score calculation and life expectancy estimation.
PATHOLOGICAL FRACTURES - FEMUR
High-Yield Exam Summary
Key Concepts
- •Pathological fracture = fracture through abnormal bone weakened by disease
- •Treatment is palliative (not curative) - restore function, relieve pain, improve quality of life
- •Most common primaries: Breast, Lung, Prostate, Kidney, Thyroid (BLT K P)
- •Lytic: lung, kidney, thyroid, breast. Blastic: prostate. Mixed: breast
Mirels' Score
- •Site: Upper limb 1, Lower limb 2, Peritrochanteric 3
- •Pain: Mild 1, Moderate 2, Functional 3
- •Lesion: Blastic 1, Mixed 2, Lytic 3
- •Size: Under 1/3 cortex 1, 1/3-2/3 is 2, over 2/3 is 3
- •Score ≥8 = prophylactic fixation, ≥9 = 33% risk, ≥10 = 50% risk
Treatment Algorithm
- •Life expectancy over 3-6 months = surgery beneficial (use Katagiri or PATHFx score)
- •Mirels' score ≥8 (impending) or complete fracture = surgical fixation
- •Diaphyseal lesion: IMN + cement augmentation
- •Periarticular lesion: Arthroplasty (cemented) with long stem
Surgical Pearls
- •Fix normal bone to normal bone
- •Bypass lesion by ≥2 cortical diameters (4x bone diameter)
- •Cement augmentation for lytic lesions (40-80g PMMA)
- •Long implant (proximal to distal metaphysis)
- •Allow immediate weight bearing
Complications
- •Nonunion: 30-40% (not problematic if construct stable)
- •Fixation failure: 10-15% (prevent with adequate bypass, cement)
- •Local recurrence: 20-30% (reduced with radiation)
- •Periprosthetic fracture: 5-10% (prevent with long implant)