FRAX Calculator
Fracture Risk Assessment Tool - Calculate 10-year probability of major osteoporotic and hip fractures
Patient Information
Clinical Risk Factors
10-Year Fracture Risk
Treatment Thresholds
Treatment Options
- • Bisphosphonates: Alendronate, risedronate, zoledronic acid
- • Denosumab: RANK-L inhibitor, subcutaneous injection
- • Teriparatide: Anabolic agent for severe osteoporosis
- • Raloxifene: SERM, reduces vertebral fractures
⚠️ Note
This is a simplified FRAX estimate. Use the official FRAX tool at shef.ac.uk/FRAX for country-specific calculations.
Understanding FRAX Score
The FRAX (Fracture Risk Assessment Tool) is a validated algorithm developed by the World Health Organization to calculate the 10-year probability of major osteoporotic fractures. It integrates clinical risk factors with or without bone mineral density (BMD) measurements to provide individualized fracture risk estimates.
Clinical Risk Factors
- Age: Risk increases substantially with age (40-90 years)
- Gender: Women have higher fracture risk than men
- BMI: Calculated from weight and height; low BMI increases risk
- Previous Fracture: History of fragility fracture after age 50
- Parental Hip Fracture: Family history of hip fracture
- Current Smoking: Active tobacco use
- Glucocorticoids: Oral steroids ≥5mg prednisone equivalent for ≥3 months
- Rheumatoid Arthritis: Confirmed diagnosis
- Secondary Osteoporosis: Conditions causing bone loss (hyperthyroidism, malabsorption, etc.)
- Alcohol: ≥3 units daily (≥21 units/week)
FRAX Outputs
- Major Osteoporotic Fracture: 10-year probability of hip, spine, humerus, or forearm fracture
- Hip Fracture: 10-year probability of hip fracture specifically
Treatment Thresholds
According to NOF (National Osteoporosis Foundation) guidelines, pharmacologic treatment is recommended when:
- 10-year hip fracture probability ≥ 3%
- 10-year major osteoporotic fracture probability ≥ 20%
- T-score ≤ -2.5 at femoral neck or spine (by WHO criteria)
- History of hip or vertebral fracture
BMD Considerations
While FRAX can be calculated without BMD, including femoral neck T-score improves accuracy. The T-score represents standard deviations from young adult mean bone density:
- Normal: T-score ≥ -1.0
- Osteopenia: T-score -1.0 to -2.5
- Osteoporosis: T-score ≤ -2.5
Secondary Osteoporosis Causes
| Category | Conditions |
|---|---|
| Endocrine | Hyperthyroidism, hyperparathyroidism, Cushing's syndrome, diabetes type 1 |
| Gastrointestinal | Celiac disease, inflammatory bowel disease, malabsorption, liver disease |
| Hematologic | Multiple myeloma, leukemia, lymphoma, sickle cell disease |
| Renal | Chronic kidney disease, renal tubular acidosis |
| Rheumatic | Rheumatoid arthritis, ankylosing spondylitis, SLE |
| Other | Immobilization, organ transplant, HIV, COPD |
Frequently Asked Questions
Do I need a bone density scan (DEXA) to use FRAX?
No, FRAX can be calculated without BMD using clinical risk factors alone. However, including femoral neck BMD T-score improves the accuracy of risk prediction. DEXA is recommended for postmenopausal women and men ≥50 years with risk factors, or all women ≥65 and men ≥70.
What is considered a "fragility fracture"?
A fragility fracture is one that occurs from low-energy trauma, such as a fall from standing height or less. Common sites include spine, hip, wrist, and humerus. Vertebral fractures are often silent and should be assessed with spine X-rays in at-risk patients. Hand, foot, face, and skull fractures are not counted as fragility fractures.
Are there different FRAX models for different countries?
Yes, FRAX has country-specific models that account for differences in fracture epidemiology and life expectancy. The official FRAX tool (shef.ac.uk/FRAX) includes models for over 60 countries. Using the appropriate country model provides more accurate risk estimates for your population.
How often should FRAX be reassessed?
For patients not on treatment, reassess FRAX every 2-5 years, or sooner if risk factors change. For patients on treatment, clinical response is better monitored with serial BMD measurements every 1-2 years rather than repeat FRAX calculations. FRAX is primarily used for treatment decisions, not monitoring.
Can FRAX be used in patients younger than 40 or older than 90?
FRAX is validated for ages 40-90 only. For younger patients, fractures are usually due to secondary causes that should be addressed directly. For patients over 90, clinical judgment should guide treatment decisions as life expectancy and competing mortality risks become more significant factors.
What are the limitations of FRAX?
FRAX limitations include: doesn't account for dose-response of risk factors (e.g., number of prior fractures), doesn't include falls risk, assumes average adherence to treatment, and may underestimate risk in certain populations (e.g., diabetes). Despite these limitations, FRAX remains the most validated tool for fracture risk assessment and guides treatment in major guidelines.
Should I use spine or hip T-score for FRAX?
FRAX specifically requires femoral neck BMD T-score, not spine or total hip. This is because the femoral neck site was used in the cohorts that developed FRAX. If you use spine or total hip T-scores, the risk estimates will be incorrect. Always use femoral neck BMD when including BMD in FRAX calculations.
What treatments are available if FRAX indicates high risk?
First-line treatments include bisphosphonates (alendronate, risedronate, zoledronic acid) which reduce fracture risk by 30-50%. Denosumab (RANK-L inhibitor) is an alternative, particularly for renal impairment. For very high risk or treatment failures, anabolic agents like teriparatide or abaloparatide can be used. All patients should receive adequate calcium (1200mg/day) and vitamin D (800-1000 IU/day), engage in weight-bearing exercise, and implement fall prevention strategies.