Osteoporosis and fragility fractures in children — branching viva

Opening: define and treat

The candidate opens by diagnosing osteoporosis. The defining move is that a vertebral compression fracture alone satisfies the ISCD definition of paediatric osteoporosis regardless of the bone density, so the T12 wedge makes the diagnosis even though the Z-score of minus 1.8 is not below the minus two threshold. The candidate states that the Z-score, never the T-score, is used in a child, and that a low Z-score alone is only low bone mass for age. The cause is secondary: glucocorticoid therapy compounded by immobility in Duchenne muscular dystrophy. ^{[1] [3]}

The treatment is the foundation first — correct calcium and vitamin D, review the glucocorticoid regimen, and maximise safe weight-bearing — then an intravenous bisphosphonate because a fracture is present. The candidate names zoledronic acid as the first-line agent, established by the phase three randomised trial in paediatric glucocorticoid-induced osteoporosis, and states that the child must be calcium and vitamin D replete before the first infusion to avoid symptomatic hypocalcaemia. ^{[2] [4]}

Branch 1: the low Z-score with no fracture

The examiner presents a child with a lumbar spine Z-score of minus 2.6 and no fracture history. The candidate refuses to label this osteoporosis: it is low bone mass for age, and the management is the foundation — calcium, vitamin D, weight-bearing, and treating any underlying cause — without a bisphosphonate. The candidate explains that the fracture, not the number, decides the drug, and that over-treating with a bisphosphonate exposes the child to the first-dose reaction and the hypocalcaemia risk without the diagnostic justification. ^{[1] [4]}