Metabolic Bone Disease - Radiology Flashcards
What are radiographic signs?
Osteopenia – “poverty of bone” – reduced mineral content of bone (not as bad as osteoporosis) - Seen in both osteoporosis and osteomalacia
Osteosclerosis – abnormal hardening of bone and increased bone density
What do radiographic tools show?
- X-rays - density
- Bone Densitometry - density/attenuation
- CT scans - density/attenuation
- MRI scans - chemical/water content
What are the features of osteoporosis?
decreased quantity of bone (bone mass) but normal microstructure
Features:
- Decreased bone mass, microstructure normal
- Normal biochemistry
- Fragility fractures, deformity and pain common
What causes osteomalacia (and rickets)?
- Due to a vitamin D deficiency
- Biochemistry – low VitD, low/normal Ca2+, high PTH
- Inadequate/Delayed mineralisation of bone
What would you see in a radiological scan in osteomalacia?
- Radiology is proportional to age/growth plate closure
- Too little mineral – osteopenia & soft bones bend and deform
- Too MUCH osteoid – Looser’s zones (and fractures)
- Looser’s zones are pseudo-fractures - Show narrow lucency and are perpendicular to bone cortex - Occur in – pubic rami, proximal femur, scapula, lower ribs
- “Codfish vertebrae” (pictured left) shows:
- Biconcave loss of height
- Osteopenia and a “pencilled-in margin
Compare the features of osteomalacia and osteoporosis
Osteomalacia:
- Less mineral
- Osteopenia
- Bend & bow before breaking
- Feature “Codfish vertebrae” – uniform spine deformity
Osteoporosis:
- Less bone
- Osteopenia
- Breaks
- Anterior wedging
Compare the features of osteomalacia and rickets
Osteomalacia:
- Changes in mature bone
- Osteopenia
- Looser’s zone’s
- Feature “Codfish vertebrae”
- Bending deformities
Rickets:
- Changes before growth plate closure
- Changes related to growth plates dominate
- Changes of osteomalacia co-exist.
What are the features of rickets?
Metaphysis (area between the epiphysis and diaphysis) has the most rapid growth and thus shows the most obvious changes
- Frayed metaphyseal margin – so metaphysis is indistinct
- Widened growth plate (no calcification)
- Splaying/cupping metaphyses due to weight bearing
- “Rickety Rosary” – enlargement of anterior ends of ribs
- Bowing of weight-bearing legs
- Osteopenia
What are the types of hyperparathyroidism? What are their biochemical features?
Primary – PTH adenoma
- High PTH, high Ca, low phosphate
Secondary – Vitamin D deficiency (renal failure, low light, impaired liver, etc.)
- High PTH, low/normal Ca, low/normal phosphate
Tertiary – autonomous production of PTH
- High PTH, high Ca, low phosphate
What are the radiological features of hyperparathyroidism?
primary (high Ca) -> bone resorption
secondary (low/normal Ca) -> renal osteodystrophy, resorption/increased density (due to PTH features)
What are the types of bone resorption?
- Sub-periosteal – affects radial aspect of middle and ring finger phalanges
- Sub-chondral
- Intra-cortical
- Brown tumours
What causes fast and slow bone loss?
Slow – involutional osteoporosis
- Bone has time to remodel (bone loss occurs due to mechanical needs)
Fast – HPT, disuse osteoporosis
- Bone loss is too rapid and loss does not cater to mechanical needs
What are the radiological features of renal osteodystrophy?
Osteomalacia and osteoporosis
Secondary hyperparathyroidism features
- Sub-periosteal erosions, brown tumours
- Sclerosis – axial skeleton, vertebral end-plates and “Rugger Jersey” spine
- Soft-tissue calcification (extra-skeletal calcifications such as in arteries)
What are the mediators of bone metabolism?
- Ca, phosphate, Vit D, PTH, calcitonin
- Other hormones – T4, GH, glucocorticoids, oestrogens, androgens, insulin
- Other factors – Vit C, cytokines, prostaglandins, growth factors
