Osteoporosis, DEXA and FRAX

Definition. A skeletal disorder of reduced bone mass with micro-architectural deterioration, leading to bone fragility and increased fracture risk. The WHO densitometric definition is a value 2.5 standard deviations or more below the young adult mean — a T-score ≤ −2.5. Osteopenia = T-score between −1 and −2.5; severe (established) osteoporosis = T ≤ −2.5 with a fragility fracture.

DEXA. Central dual-energy X-ray absorptiometry is the standard method for measuring bone mineral density at the spine, hip and forearm. The T-score compares with the young adult mean; the Z-score compares with age-matched peers and is used in younger patients and to flag secondary osteoporosis when ≤ −2.0. US guidelines recommend DEXA for all women aged 65 or older; the UK National Osteoporosis Guideline Group instead uses FRAX first and DEXA selectively. Geriatric pitfall: spinal osteoarthritis, vertebral fractures and aortic calcification falsely elevate lumbar BMD in the elderly — rely on the total hip / femoral neck.

FRAX. An algorithm integrating clinical risk factors, with or without femoral neck BMD, to compute the 10-year probability of a major osteoporotic fracture and of hip fracture. Inputs: age, sex, weight and height (BMI), previous fragility fracture, parental hip fracture, current smoking, glucocorticoid therapy, rheumatoid arthritis, secondary osteoporosis and alcohol ≥3 units/day. FRAX is country-specific, and an Indian FRAX model is available.

FRAX — use and limitations. Its main function is to set an intervention threshold: treat when the FRAX probability equals or exceeds the risk of someone with a prior fragility fracture. Limitations — it does not capture glucocorticoid dose, the number or recency of fractures, falls, lumbar spine BMD or diabetes. Probability can be modulated by the trabecular bone score (TBS), glucocorticoid dose, hip axis length, fall history and type 2 diabetes.

Major risk factors for fragility fracture. Age, female sex, low BMI, prior fragility fracture, parental hip fracture, height loss >4 cm, glucocorticoid therapy, smoking and excess alcohol; plus secondary osteoporosis — rheumatoid arthritis, hyperthyroidism, primary hyperparathyroidism, hypogonadism, diabetes, inflammatory bowel disease, aromatase inhibitors, anorexia nervosa, organ transplantation, prolonged immobility, COPD and HIV. In the oldest old, falls risk drives fracture risk at least as much as BMD does.

Investigating the older patient with a fragility fracture. Only 3% of hip fractures in the elderly are pathological, but over half of patients are osteoporotic and almost all are osteopenic; after 80, a woman with age-normal bone density already has a T-score of −2.5, so DEXA for diagnosis alone is chiefly useful under 75. Take a full medication (corticosteroid) and alcohol history and check CBC, ESR, calcium (mg/dL), phosphate, alkaline phosphatase, creatinine, liver and thyroid function, 25(OH) vitamin D and serum/urine protein electrophoresis. Secondary osteoporosis is uncommon in this age group, but hyperthyroidism is the dominant cause; also consider malnutrition, low body weight, hypogonadism, hyperparathyroidism and myeloma. Perform vertebral fracture assessment or spine X-ray if there is height loss or hyperkyphosis.

Non-pharmacological management — for every patient. Calcium 800–1000 mg/day (up to 1200 mg), vitamin D 800–1000 IU/day, protein ≥1 g/kg body weight/day, daily weight-bearing and resistance exercise, smoking cessation, alcohol ≤2 units/day, and multifactorial falls prevention with home hazard assessment and medication review. Hip protectors probably reduce hip fracture in nursing and residential care, but poor acceptance and adherence limit their use.

First-line drug therapy. Oral bisphosphonates — alendronate 70 mg weekly or risedronate 35 mg weekly (gastro-resistant risedronate may improve adherence). Take fasting, upright, with plain water, 30 minutes before food. Contraindications: eGFR <30–35 mL/min, oesophageal stricture or achalasia, inability to remain upright, and uncorrected hypocalcaemia or vitamin D deficiency. Adverse effects: oesophagitis, acute-phase reaction after IV zoledronate, and rarely osteonecrosis of the jaw and atypical femoral fracture. Zoledronic acid 5 mg IV yearly is the option when oral therapy fails or is not tolerated, and after hip fracture it reduces both re-fracture and mortality.

Other agents and sequencing. Denosumab 60 mg subcutaneously 6-monthly — usable in renal impairment, but monitor calcium and never stop it abruptly: discontinuation causes rebound multiple vertebral fractures, so it must be followed by a bisphosphonate for 1–2 years. For very high or imminent fracture risk, an anabolic agent first — teriparatide, abaloparatide or romosozumab (romosozumab is contraindicated within one year of myocardial infarction or stroke) — always followed by an antiresorptive. Menopausal hormone therapy and raloxifene/bazedoxifene are options in younger postmenopausal women; calcitonin has weak fracture-prevention efficacy.

Follow-up and duration. Assess adherence and side effects; use bone turnover markers at 3–6 months to verify compliance with bone-resorption inhibitors; repeat DEXA about every 2 years. Reassess after 5 years of oral or 3 years of intravenous bisphosphonate: continue in high-risk patients; consider a 2-year drug holiday in low-risk patients, reconsidered yearly; restart immediately if an incident fracture occurs. Fracture Liaison Services — systematic case-finding and treatment after every fragility fracture — are the best-established service model, and their benefits are well documented.

Screening works; supplements alone do not. The SCOOP randomised trial (Lancet) showed that community FRAX-based screening of older women reduces hip fractures, supporting systematic case-finding. Conversely, a meta-analysis of 33 randomised trials in 51,145 participants (Zhao et al., JAMA) found that calcium, vitamin D, or both were NOT associated with a lower fracture risk in community-dwelling older adults — supplements are a necessary adjunct to, but never a substitute for, specific anti-osteoporosis therapy.

The "very high risk" category and anabolic-first sequencing. Current international guidance (ESCEO/IOF, AACE, Endocrine Society and 2023–2025 updates) formally defines very high risk — a fracture within the last 24 months, a fracture while on treatment, multiple fractures, T-score ≤ −3.0, or very high FRAX probability — and recommends starting with an anabolic agent (romosozumab or teriparatide) followed by an antiresorptive in this group, because sequence matters: anabolic-then-antiresorptive produces substantially greater BMD and fracture-risk reduction than the reverse order.