# CIM Case: Atypical Femoral Fracture ## Clinical Scenario **Patient:** 72-year-old woman **Presentation:** Fall from standing while walking, sudden right thigh pain and inability to weight-bear **Relevant history:** Postmenopausal osteoporosis on alendronate for 8 years, left thigh aching for past 4 months (intermittent, worse with walking), rheumatoid arthritis on low-dose prednisolone, previous vertebral compression fractures (T11, L1), vitamin D deficiency (treated) **Examination findings:** - BMI 22, thin habitus - Right leg shortened and externally rotated - Tenderness at mid-thigh level - Unable to perform straight leg raise - Neurovascularly intact distally - Left thigh: tenderness over lateral mid-femur on palpation - No wounds or bruising - Kyphotic thoracic spine --- ## Investigations Provided ### Laboratory Results | Test | Result | Normal Range | Interpretation | |------|--------|--------------|----------------| | Hb | 118 g/L | 115-155 g/L | Normal | | WCC | 7.2 ×10⁹/L | 4-11 ×10⁹/L | Normal | | Platelets | 245 ×10⁹/L | 150-400 ×10⁹/L | Normal | | CRP | 8 mg/L | <5 mg/L | Mildly elevated | | Calcium | 2.35 mmol/L | 2.2-2.6 mmol/L | Normal | | Phosphate | 1.1 mmol/L | 0.8-1.5 mmol/L | Normal | | ALP | 95 U/L | 30-120 U/L | Normal | | Vitamin D | 65 nmol/L | >50 nmol/L | Adequate (supplemented) | | PTH | 4.5 pmol/L | 1.5-6.5 pmol/L | Normal | | Creatinine | 82 μmol/L | 45-90 μmol/L | Normal | | eGFR | 68 mL/min | >60 | Mildly reduced | ### Imaging **Image 1: AP and Lateral Radiographs of Right Femur** **Radiological features:** - Transverse fracture through lateral cortex of femoral diaphysis - Located distal to lesser trochanter, proximal to supracondylar flare - Non-comminuted (simple fracture pattern) - Short oblique component - Focal lateral cortical thickening ("beaking") at fracture site - Medial spike (characteristic morphology) - Generalised cortical thickening of diaphysis - No periosteal reaction beyond immediate fracture site **Image 2: Full-Length Bilateral Femur X-rays** **Findings:** - Right: Complete atypical femoral fracture as described - Left: Lateral cortical thickening ("dreaded black line") at mid-diaphysis - Localised periosteal reaction over lateral cortex - Incomplete stress fracture (lateral cortex only) - No complete fracture --- ## Questions & Model Answers **Diagnosis: Bilateral Atypical Femoral Fractures** - Right: Complete atypical femoral fracture - Left: Incomplete atypical femoral fracture (stress reaction) **ASBMR Criteria for Atypical Femoral Fracture:** **Major Features (All 5 Required for Diagnosis):** | Feature | This Patient | |---------|--------------| | Located along femoral diaphysis (below lesser trochanter to above supracondylar flare) | ✓ Mid-diaphysis | | Associated with no trauma or minimal trauma | ✓ Fall from standing | | Transverse or short oblique configuration | ✓ Transverse with short oblique | | Non-comminuted | ✓ Simple fracture | | Complete fractures extend through both cortices; incomplete involve only lateral cortex | ✓ Complete on right, incomplete on left | **Minor Features (Not Required but Supportive):** - Localised periosteal reaction at lateral cortex ✓ - Generalised increase in cortical thickness ✓ - Prodromal symptoms (thigh or groin pain) ✓ (left thigh pain 4 months) - Bilateral involvement ✓ - Delayed fracture healing > **Consultant Tip:** All 5 major criteria must be met. The key distinguishing features are location (subtrochanteric/diaphyseal, not neck or intertrochanteric), transverse orientation, and minimal trauma. **Bisphosphonate Association:** | Duration of Use | Relative Risk | Absolute Risk | |-----------------|---------------|---------------| | <2 years | Baseline | Rare | | 2-5 years | 2× | Low | | 5-10 years | 8-10× | 5-100 per 100,000/year | | >10 years | Higher | Still low absolute risk | **Mechanism:** - Bisphosphonates inhibit osteoclast-mediated bone resorption - Prolonged suppression of bone remodelling ("frozen bone") - Accumulation of microdamage without repair - Lateral femoral cortex under tension during gait - Stress fractures develop at tension side - Propagate to complete fractures **Risk Factors for Atypical Femoral Fracture:** - Duration of bisphosphonate use (strongest factor) - Concurrent glucocorticoid use (this patient on prednisolone) - Asian ethnicity - Femoral bowing - Short stature - Lower limb geometry abnormalities **Important Context:** - Benefits of bisphosphonates in preventing typical osteoporotic fractures (hip, spine) far outweigh risks - Typical fractures prevented: 50-70 per 100,000 patient-years - Atypical fractures caused: 5-100 per 100,000 patient-years - Net benefit remains positive, especially in high-risk patients > **Consultant Tip:** Don't over-attribute fractures to bisphosphonates. The absolute risk is low, and many patients benefit enormously from treatment. Individualise duration of therapy. **Immediate Management:** **Step 1: Emergency Department** - Analgesia (IV morphine) - Above-knee backslab or Thomas splint - IV fluids - Cross-match blood (2 units) - Full metabolic workup **Step 2: Medication Review** - STOP bisphosphonate immediately - Continue calcium and vitamin D supplementation - Review need for glucocorticoid (discuss with rheumatology) **Step 3: Imaging** - Full-length bilateral femur X-rays (ESSENTIAL) - CT of fracture if complex - DEXA scan (if not recent) **Step 4: Surgical Planning** | Consideration | Rationale | |---------------|-----------| | Cephalomedullary nail preferred | Spans stress-riser at subtrochanteric region | | Long nail (hip to knee) | Protects entire bone | | Reaming controversial | May stress abnormal cortex | | Prophylactic contralateral fixation | Consider for symptomatic incomplete fracture | **Step 5: Post-operative Care** - Protected weight-bearing initially - Monitor for delayed union (common) - Bone metabolic workup if not already done - Consider anabolic therapy (teriparatide) for healing > **Consultant Tip:** Always get full-length bilateral femur X-rays. Missing an incomplete fracture on the contralateral side is a preventable error. **Cephalomedullary Nail Fixation:** **Setup:** - Supine on fracture table - Traction applied via skeletal traction or boot - Image intensifier for lateral and AP views - Radiolucent leg support **Reduction Challenges:** | Deformity | Cause | Correction | |-----------|-------|------------| | Varus | Abductors on proximal fragment | Adduction of leg, lateral blocking screw | | Flexion | Iliopsoas on proximal fragment | Extend hip, anterior blocking screw | | External rotation | Short external rotators | Internal rotation of leg | **Technique:** 1. Entry point: Tip of greater trochanter (piriformis fossa if non-cephalomedullary) 2. Guidewire placement with fluoroscopic guidance 3. Sequential reaming (1-1.5mm over nail diameter) - controversial in atypical fractures 4. Insert long cephalomedullary nail 5. Proximal locking (cephalic screw/blade into femoral head) 6. Distal locking (2 screws) **Technical Considerations:** - May need open reduction if closed fails - Consider cerclage wire for unstable patterns - Avoid excessive reaming (brittle cortex) - Bone graft to fracture site if open **Fixation Alternatives:** | Option | Indication | |--------|------------| | Plate fixation | Periprosthetic, very distal fracture | | Short nail | NOT recommended (stress-riser at tip) | > **Consultant Tip:** Use a LONG nail. Short nails create stress-risers at the tip which can cause a new fracture in this abnormal bone. **Contralateral Limb Assessment:** This patient has an incomplete (lateral cortex only) atypical fracture with: - Cortical beaking ("dreaded black line") - Periosteal thickening - Prodromal symptoms (4 months of thigh pain) **Management Options:** | Option | Indication | Outcome | |--------|------------|---------| | **Prophylactic nailing** | Symptomatic, significant cortical changes, high activity level | Prevents fracture, immediate rehabilitation | | **Protected weight-bearing + serial imaging** | Asymptomatic, minimal changes | May heal with cessation of bisphosphonate | | **Observation** | Minimal changes, not symptomatic | Risk of progression to complete fracture | **For This Patient:** Given symptomatic incomplete fracture with dreaded black line, **prophylactic nailing is recommended**. **Timing:** - Can be done during same anaesthetic as index procedure - Or delayed 1-2 weeks (patient preference, surgical capacity) **Additional Management:** - Cease bisphosphonate (already recommended) - Consider teriparatide (anabolic agent) - Promotes bone healing - May accelerate healing of incomplete fracture - 24 months course - Calcium 1000-1200mg daily - Vitamin D 1000-2000 IU daily - Falls prevention program - Physiotherapy for mobility > **Consultant Tip:** A symptomatic incomplete atypical fracture with a visible cortical defect has high risk of progression. Prophylactic nailing is generally preferred over observation. **Fracture Healing:** | Outcome | Atypical Fracture | Typical Fracture | |---------|-------------------|------------------| | Non-union rate | 15-25% | 1-2% | | Delayed union | 30-40% | 5-10% | | Time to union | 6-12 months | 3-4 months | | Revision surgery | 10-25% | <5% | **Factors Affecting Healing:** - Continued bisphosphonate use (negative) - Smoking (negative) - Malnutrition (negative) - Teriparatide use (positive) - Bone grafting (positive if delayed union) **Management of Delayed/Non-union:** 1. Exchange nailing with bone graft 2. Plate augmentation 3. Teriparatide if not already on 4. Diamond concept: cells, scaffolds, growth factors, mechanical stability **Long-term Osteoporosis Management:** | Option | Considerations | |--------|----------------| | Drug holiday | 3-5 years after 5+ years of bisphosphonate | | Teriparatide | Anabolic, may heal stress fractures, 24 month limit | | Denosumab | Alternative anti-resorptive, also associated with atypical fractures | | Romosozumab | Anabolic then anti-resorptive, newer agent | **Monitoring:** - Serial X-rays until union - DEXA scan (baseline and monitoring) - Fracture liaison service involvement - Bone turnover markers (if available) > **Consultant Tip:** Expect delayed healing. Warn patients that these fractures take longer than typical fractures and may require additional procedures. Teriparatide may help. --- ## Key Teaching Points ### Pattern Recognition **This pattern suggests Atypical Femoral Fracture:** - Postmenopausal woman on long-term bisphosphonate (>5 years) - Minimal trauma mechanism (standing fall) - Subtrochanteric or diaphyseal location - Transverse/short oblique pattern (NOT spiral) - Lateral cortical beaking on X-ray - Prodromal thigh pain (may have had for weeks/months) **Distinguishing from Typical Osteoporotic Fracture:** | Feature | Atypical | Typical | |---------|----------|---------| | Location | Subtrochanteric/diaphyseal | Femoral neck, intertrochanteric | | Pattern | Transverse, non-comminuted | Variable, often comminuted | | Lateral cortex | Beaking, thickening | Normal | | Prodromal pain | Common (weeks-months) | Rare | | Healing | Delayed | Usually uneventful | ### Critical Management Points 1. **Full-length bilateral X-rays** - 30-40% have contralateral involvement 2. **Stop bisphosphonate** - but continue calcium and vitamin D 3. **Long cephalomedullary nail** - never short nails 4. **Expect delayed union** - warn patient, consider teriparatide 5. **Prophylactic fixation** - for symptomatic incomplete fractures 6. **MDT involvement** - orthopaedics, endocrinology, fracture liaison --- ## Common Examiner Follow-ups **Q: "What is the 'dreaded black line'?"** The dreaded black line refers to the radiolucent line visible on the lateral cortex of the femur in incomplete atypical femoral fractures. It represents the stress fracture propagating through cortical bone. Its presence indicates high risk of progression to complete fracture and is an indication for prophylactic nailing if symptomatic. --- **Q: "Should all patients on bisphosphonates have a drug holiday?"** Drug holiday considerations: - After 5 years of oral bisphosphonate (or 3 years IV) - For patients at moderate fracture risk - Continue in high-risk patients (previous fragility fracture, very low BMD) - Monitor during holiday with DEXA and bone turnover markers - Resume if fracture risk increases Current guidelines (ASBMR 2016, NICE 2017): - Individualise based on fracture risk - Benefits of treatment generally outweigh risks of atypical fracture - Reassess after 3-5 years of treatment --- **Q: "What is the role of teriparatide?"** Teriparatide (recombinant PTH 1-34): - Anabolic agent - stimulates bone formation - May promote healing of atypical fractures - Duration: 24 months maximum (lifetime) - Contraindicated if prior radiation, Paget's, hypercalcaemia - Expensive, requires daily injection - Consider for incomplete fractures or delayed union Evidence: Case series suggest improved healing, but no RCTs specifically for atypical fractures. --- **Q: "How do you counsel a patient who presents with prodromal thigh pain on long-term bisphosphonate?"** Counselling approach: 1. Explain concern for stress reaction/incomplete fracture 2. Order full-length bilateral femur X-rays 3. If positive: discuss prophylactic fixation vs observation 4. If negative: consider MRI if high clinical suspicion 5. Stop bisphosphonate 6. Modify activity (avoid high-impact exercise) 7. Ensure adequate calcium, vitamin D 8. Follow up in 4-6 weeks with repeat imaging --- ## Related Topics - Osteoporosis Management - Bisphosphonate Therapy - Subtrochanteric Fractures - Femoral Shaft Fractures - Intramedullary Nailing Techniques - Pathological Fractures