What Is an Atypical Femoral Fracture?

An atypical femoral fracture (AFF) is a rare type of break in the thigh bone (femur) that differs from more common fractures caused by major trauma. Instead of occurring in the hip or upper part of the femur, AFFs typically happen along the midshaft or just below the lesser trochanter—the bony bump near the top of the femur. Although uncommon, these fractures deserve attention because they can develop with minimal or no trauma and may be linked to certain medications or underlying conditions.

Why “Atypical”?

The word “atypical” highlights how these fractures behave differently:

• They often occur after minimal impact (e.g., a minor fall or simple twist).
• The break tends to be transverse (straight across) or short oblique (slanted slightly).
• The “fracture line” can start as a stress reaction—thickening of the outer bone cortex—before it snaps completely.
• Bilateral occurrence (both legs) is possible in up to 30% of cases.

Who Is at Risk?

Although anyone can experience an atypical femoral fracture, certain factors raise the risk:

• Prolonged use of bisphosphonates
– Medications such as alendronate (Fosamax) or risedronate (Actonel) prescribed for osteoporosis have been linked to AFF when used for more than 5 years.
• Other osteoporosis therapies
– Denosumab (Prolia) or teriparatide (Forteo) in rare instances, especially when combined with other bone‐strengthening drugs.
• Age and gender
– AFFs are most often reported in women over age 65, though men and younger adults can be affected.
• Certain medical conditions
– Rheumatoid arthritis, lupus, or other chronic inflammatory diseases.
– Kidney disease, vitamin D deficiency, or other metabolic bone disorders.
• Mechanical factors
– Anatomical variations like a bowed femur may concentrate stress in one area.
• Genetics
– Rare inherited disorders affecting collagen or bone turnover.

Signs and Symptoms

An atypical femoral fracture often begins as a subtle stress reaction. Early awareness can prevent a complete break:

• Dull, aching pain in the thigh or groin
– Pain may worsen with weight bearing or walking.
• Discomfort on both sides
– Bilateral pain can signal stress reactions in both femurs.
• Prodromal symptoms
– Weeks to months of mild symptoms before a full fracture.
• Sudden, severe pain
– Indicates a complete break, often accompanied by an inability to walk or bear weight.

If you experience persistent thigh or groin pain without a clear cause, especially if you take medications for osteoporosis, it’s wise to seek medical attention.

How Is It Diagnosed?

Early diagnosis of an atypical femoral fracture helps prevent complications:

1. Medical History and Physical Exam
   – Your doctor will review medications, past bone‐density tests, and any history of thigh pain.
   – Physical exam focuses on tenderness along the femur, range of motion, and gait assessment.

2. Imaging Studies
   – X-rays: The first step, often revealing a transverse fracture line and cortical thickening.
   – MRI or bone scan: More sensitive for detecting stress reactions before a complete break.
   – CT scan: Helps map the exact location and extent of a fracture.

3. Laboratory Tests
   – Blood tests may check calcium, vitamin D, parathyroid hormone, and markers of bone turnover.

Treatment Options

Treatment depends on whether the fracture is incomplete (stress reaction) or complete:

Incomplete Fracture (Stress Reaction)

• Activity modification
  – Weight‐bearing activities may be limited. A walker or crutches can reduce stress on the femur.
• Medication review
  – Your doctor may stop bisphosphonates or other osteoporosis drugs temporarily.
• Supplementation
  – Ensure adequate calcium (1,000–1,200 mg/day) and vitamin D (800–1,000 IU/day) intake.
• Close monitoring
  – Repeat imaging in 6–8 weeks to check for healing or progression to a complete fracture.

Complete Fracture

• Surgical repair
  – Intramedullary nailing is the most common method, placing a metal rod inside the femur to stabilize the bone.
  – Plates and screws may be used in certain cases.
• Rehabilitation
  – Early, guided physical therapy helps restore mobility and muscle strength.
  – Gradual return to weight‐bearing as healing permits.

Recovery and Outlook

Recovery from an atypical femoral fracture varies:

• Healing time
– Complete fractures often take 4–6 months to heal fully, depending on age, health, and the exact surgical approach.
• Physical therapy
– A structured program can help regain hip and thigh strength, balance, and flexibility.
• Medication management
– Your doctor may recommend switching to alternative osteoporosis treatments (e.g., teriparatide) after healing.
• Long‐term monitoring
– Periodic imaging ensures that bone quality improves and no new stress reactions appear.

Most patients regain significant function, though some may have lingering stiffness or mild discomfort.

Preventing Atypical Femoral Fractures

While you can’t eliminate all risk, you can take steps to protect your femurs:

• Maintain bone health
  • Balanced diet rich in calcium and vitamin D
  • Regular weight‐bearing and muscle‐strengthening exercises
• Review medications
  • Discuss the duration of bisphosphonate therapy with your doctor
  • Consider “drug holidays” if you’ve taken bisphosphonates for more than 5 years
• Monitor bone density
  • Periodic DEXA scans to assess osteoporosis treatment effectiveness
• Report new pain promptly
  • Early evaluation of thigh or groin discomfort can catch stress reactions before they become full fractures

When to Seek Help

If you experience:

• Sudden, severe thigh or groin pain after minor activity
• Inability to bear weight on one leg
• Ongoing aching in the thigh or groin for more than a week

…you should have a healthcare provider evaluate you right away. For a free, online symptom check, using the doctor approved Ubie Symptom Checker, click here.

Always treat persistent or severe pain seriously—delay can lead to a complete fracture requiring surgery.

Talk to a Doctor

The information here aims to help you understand atypical femoral fractures. It does not replace professional medical advice. If you have any serious or life‐threatening symptoms, such as sudden inability to walk, severe pain, or signs of infection after surgery (fever, redness, swelling around a wound), please speak to a doctor immediately. Your health and safety are paramount.