1. Core Clinical Definition & Assessment
Osteoporosis is a systemic skeletal disorder characterised by low bone mass and micro-architectural deterioration of bone tissue, leading to increased bone fragility and susceptibility to fracture.
Risk Factors for Fragility Fractures
- Demographic & Lifestyle: Advanced age, female sex, low Body Mass Index ($\text{BMI} < 19\text{ kg/m}^2$), parental history of hip fracture, smoking, and alcohol intake $\ge 3\text{ units/day}$.
- Endocrine & Inflammatory: Early menopause ($< 45$ years), rheumatoid arthritis, hyperthyroidism, primary hyperparathyroidism, and malabsorption syndromes (e.g., Coeliac disease, IBD).
- Medications: Systemic corticosteroids ($\ge 7.5\text{ mg}$ prednisolone equivalent daily for $\ge 3$ months), aromatase inhibitors (e.g., anastrozole), GnRH agonists, and long-term PPI or anticonvulsant use.
2. Risk Stratification: FRAX & NOGG Strategy
Step 1: When to Assess Risk
- All women $\ge 65$ years and all men $\ge 75$ years.
- Adults $< 65$ (women) or $< 75$ (men) in the presence of any risk factor listed above.
- Automatically assess anyone who has sustained a prior fragility fracture.
Step 2: Use FRAX (Fracture Risk Assessment Tool)
Input clinical parameters to estimate the 10-year probability of a major osteoporotic fracture (hip, spine, wrist, or proximal humerus).
- Without DEXA: Can be calculated initially based on clinical risk factors alone to determine the next step.
Step 3: Interpret Using NOGG Guidance
The FRAX output will plot the patient onto a traffic-light risk graph:
| Risk Category |
Clinical Action Required |
| Low Risk (Green) |
Reassure; provide lifestyle advice. Reassess in 5 years. |
| Intermediate Risk (Amber) |
Arrange a DEXA Scan to measure Bone Mineral Density (BMD). Re-enter the T-score into FRAX to recalculate risk. |
| High Risk (Red) |
Treat immediately. You do not need to wait for a DEXA scan if a patient has had a hip or vertebral fragility fracture, or if clinical FRAX scores are unequivocally high. |
3. Diagnostic Criteria (WHO Classification)
Diagnosis is based on the T-score, measured via Dual-energy X-ray Absorptiometry (DEXA) at the lumbar spine or femoral neck:
$$\text{T-score} = \frac{\text{Patient's BMD} - \text{Peak Young Adult Mean BMD}}{\text{Standard Deviation (SD)}}$$