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]

Branch 2: the hypophosphatasia trap

The examiner asks what a low alkaline phosphatase means in a fracturing child. The candidate answers hypophosphatasia, an inherited deficiency of tissue-nonspecific alkaline phosphatase, and warns that bisphosphonates, which might be considered for the fractures, worsen the mineralisation defect and must be avoided. The candidate explains that the alkaline phosphatase is read before any bisphosphonate is prescribed, and that the treatment of the perinatal and infantile forms is enzyme replacement rather than an antiresorptive. [4]

Branch 3: the osteogenesis imperfecta distinction

The examiner presents a six-year-old with recurrent fractures, blue sclerae, and a positive family history. The candidate recognises osteogenesis imperfecta, a defect of type one collagen, and explains that it is a primary bone disease carrying its own multidisciplinary pathway — bisphosphonates, orthopaedics, rehabilitation, audiology, dentistry, and genetics — distinct from secondary osteoporosis. The candidate distinguishes it from idiopathic juvenile osteoporosis, which is a diagnosis of exclusion in the prepubertal years and often remits at puberty. [4]

Branch 4: the safeguarding question

The examiner closes with fractures in a pre-mobile infant. The candidate states that unexplained fractures in a non-ambulant infant must always hold non-accidental injury alongside osteogenesis imperfecta, and that the two are not mutually exclusive. The mechanism history, the fracture pattern on skeletal survey (classic metaphyseal lesions, rib fractures, fractures of different ages), the biochemistry, and the collagen testing are all part of the assessment, and a bone-disease diagnosis never closes the safeguarding enquiry on its own. [1] [4]

Closing: surveillance and the family

The examiner closes with the surveillance programme. The candidate states that the glucocorticoid-exposed child has a DXA and lateral spine at baseline and at intervals, because the vertebral-fracture risk clusters in the first one to three years after steroids start. The candidate explains that the family is counselled that bone health is a marathon alongside the primary disease, that calcium and vitamin D are sustained, and that the transition to adult care is planned through adolescence because the peak bone mass built in childhood determines the adult osteoporosis risk. [3] [5]