Osteoporosis OSCE — FRAX Score, DEXA Scan, Bisphosphonates, and Falls Prevention

Why Osteoporosis Is Examined

Osteoporosis affects approximately 3.5 million people in the UK and is responsible for 500,000 fragility fractures annually, including 70,000 hip fractures. It is increasingly examined in OSCEs as a prescribing station (initiate bone protection for a patient on long-term steroids), communication station (explain osteoporosis and bisphosphonate treatment to a patient), and clinical reasoning (post-fracture bone health assessment). Examiners test FRAX application, DEXA interpretation, and safe prescribing.

Definition and Pathophysiology

Osteoporosis: Reduced bone mineral density (BMD) defined by T-score of -2.5 or below on DEXA scan. Reflects an imbalance between osteoblast (bone formation) and osteoclast (bone resorption) activity, with resorption predominating.

Osteopaenia: T-score between -1.0 and -2.5 — below normal but not yet osteoporotic.

Fragility fracture: A fracture from a fall from standing height or less — indicates clinically significant bone fragility regardless of T-score.

Risk Factors

FRAX Score — 10-Year Fracture Risk

FRAX (Fracture Risk Assessment Tool) calculates 10-year probability of major osteoporotic fracture (hip, vertebral, wrist, or proximal humerus) and hip fracture specifically.

Inputs: age, sex, weight, height, previous fracture, parental hip fracture, smoking, glucocorticoids, rheumatoid arthritis, secondary osteoporosis, alcohol, and optionally femoral neck BMD.

Thresholds for treatment (NOGG 2023):

• FRAX major osteoporotic fracture above 10% at age 50 → treat
• FRAX above the intervention threshold for age → treat
• Any prior fragility fracture → treat without waiting for FRAX

DEXA Scan — Interpretation

T-score: SD units below the mean peak bone density of a young adult of the same sex.

Z-score: SD units below age-matched normal — used in premenopausal women and men under 50 (where low Z-score prompts secondary cause investigation).

Treatment

First-Line: Bisphosphonates

Alendronic acid (alendronate):

• 70 mg once weekly oral (most common UK prescription)
• Must be taken on an empty stomach with a full glass of water; remain upright for 30 minutes after
• Oesophageal contraindications: inability to sit/stand upright for 30 minutes, active oesophageal disease, achalasia

Risedronate:

• 35 mg once weekly — alternative if alendronate not tolerated
• Similar administration requirements

Zoledronic acid:

• 5 mg IV infusion once yearly — for patients unable to tolerate oral bisphosphonates or with poor adherence
• Requires calcium supplementation 1-2 weeks before infusion

Duration: 5 years first-line; reassess at 5 years — high-risk patients (T-score below -2.5, previous hip/vertebral fracture) continue to 10 years; IV zoledronate reassess at 3 years.

Calcium and Vitamin D

Prescribe with bisphosphonates (and as standalone treatment for dietary deficiency):

• Calcium carbonate 1.2 g OD + colecalciferol 800 IU OD (Adcal-D3 or equivalent) — if dietary intake inadequate
• Check serum calcium and eGFR before prescribing
• Serum 25-OH vitamin D: replace if below 50 nmol/L (deficient) before bisphosphonate

Second-Line Agents

Frequently Asked Questions

"What is the difference between a fragility fracture and a pathological fracture?"

A fragility fracture results from low-energy trauma (fall from standing height or less) in bone with reduced strength — typically from osteoporosis. A pathological fracture occurs through diseased bone — most commonly from metastatic cancer (breast, lung, prostate, kidney, thyroid), myeloma, or primary bone tumours. Clinical clues to pathological fracture: occurring through normal bone on imaging, no adequate trauma mechanism, known primary cancer, night pain, systemic features.

"How should you counsel a patient on starting alendronate?"

"This tablet is taken once a week on the same day. Take it first thing in the morning on an empty stomach with a full glass of plain water — not tea, coffee, or juice. Remain sitting upright or standing for at least 30 minutes before eating or lying down — this protects the food pipe from irritation. Common side effects include heartburn or difficulty swallowing — if these occur, stop and contact your GP. Rarely, the medicine can affect the jaw — please tell your dentist you are on this medication before any dental work."

"Why must bisphosphonate therapy be reassessed at 5 years?"

Bisphosphonates accumulate in bone and continue to have an antiresorptive effect for years after stopping — a phenomenon called the "bisphosphonate holiday." Prolonged continuous use (beyond 5-7 years) is associated with atypical femoral fractures (stress fractures from oversuppression of bone turnover). A drug holiday of 2-3 years after 5 years in lower-risk patients allows bone turnover to normalise while retaining some protective effect. High-risk patients (ongoing very low BMD or prior fragility fracture) may continue with specialist guidance.

"What secondary causes of osteoporosis should be excluded?"

Before attributing osteoporosis to primary (postmenopausal or age-related) causes, exclude secondary causes with blood tests: FBC (haematological malignancy), U&E, LFTs (hepatic disease), calcium and phosphate (hyperparathyroidism, malabsorption), TFTs (hyperthyroidism), testosterone in men (hypogonadism), 25-OH vitamin D, serum protein electrophoresis and Bence Jones protein (myeloma), coeliac antibodies (tTG IgA) in young patients with low bone density. Secondary causes should be treated first — untreated secondary causes make bone protection less effective.

"What is the role of falls prevention in osteoporosis management?"

Osteoporosis causes fractures only when bones are subjected to force — usually a fall. Falls prevention is therefore an integral part of osteoporosis management. Interventions with evidence: balance and strength exercises (Tai Chi, OT assessment), medication review (reduce or stop sedatives, antihypertensives causing postural hypotension, anticholinergics), vision correction, home hazard assessment and modification, hip protectors in care home residents. NICE CG161 recommends a multifactorial falls risk assessment for all older people who fall.

Related Posts

• Falls Assessment OSCE — systematic falls risk assessment integrating bone health
• Frailty Assessment OSCE — frailty, sarcopaenia, and their relationship to fracture risk
• Medication Review OSCE — reviewing fall-risk and bone-loss medications in older adults