Metabolic Bone Disease: Radiology Flashcards
principle issue in osteoporosis
decreased bone mass or density
principle issue in osteomalacia and rickets
defective mineralisation
what form of hyperparathyroidism accompanies chronic renal def?
secondary hyperparathyroidism
what is the radiological sign seen in both osteoporosis and osteomalacia?
Osteopenia – “poverty of bone” – reduced mineral content of bone (not as bad as osteoporosis).
what is osteosclerosis?
Osteosclerosis – abnormal hardening of bone and increased bone density.
bone formation that occurs after bone resorption
what radiological tools are used for bone density assessment?
X-ray
CT
bone densitometry
what radiological tool is used for assessment of biochemical composition of bone?
MRI
what radiological tool is used for bone turnover assessment?
radionuclide bone scan
what are the properties of osteoporotic bones?
o Decreased bone mass, microstructure normal.
o Normal biochemistry and microstructure
o Fragility fractures, deformity and pain common.
what does white in X-ray mean?
the whiter the bone, the denser
what is the biochemistry in osteomalacia?
o Biochemistry – low VitD, low/normal Ca2+, high PTH.
o Inadequate/Delayed mineralisation of bone.
what is the result of low mineralisation?
osteopenia
soft bones bend and deform
what is the result of too much osteoid?
looser’s zones and fractures (pseudo fractures )
these appear with narrow lucency and are perpendicular to bone cortex
where do Looser’s Zone fractures happen most of the time?
pubic rami
proximal femur
scapula
lower ribs.
what are the ranges in T score and the resulting pathology?
-1.5 to -2.5 –> osteopenia
< or = -2.5 –> osteoporosis
example of radiological finding in osteomalacia vertebrae
codfish vertebrae
- biconcave loss of height
- osteopenia
- pencilled in margin
what are the bone features of osteoporosis?
- reduced cortical bone
- thinning of cortex
- reduced trabecular
- insufficiency fractures under normal stresses on abnormal bone
- osteopenia
- anterior wedging
Honda sign shows greater uptake in the pelvis
Bone oedema on MRI
what are the bone features of osteomalacia?
- decreased mineralisation
- Looser’s zones at areas of higher tensile stress
- sclerotic margins (attempted bone healing thickens bone around fracture line)
- bending and bowing before breakage
- rickets centred in growth plates
- codfish vertebrae (uniform spine deformity)
how does osteomalacia differ to rickets?
osteomalacia: in mature bone
sees the normal features e.g. codfish vert, LZ, osteopenia
rickets: changes before growth plate closures i.e. in children is dominates the growth plates. Osteomalacia changes can co-exist
what does radiological imaging of osteomalacia/rickets depend on?
age and closure of growth plates
which part of the bone shows the most obvious changes in rickets and why?
metaphysis as this area has the most rapid growth
what are the bone features of rickets?
o Frayed metaphyseal margin – so metaphysis is indistinct.
o Widened growth plate (no calcification).
o Splaying/cupping metaphyses due to weight bearing.
o “Rickety Rosary” – enlargement of anterior ends of ribs.
o Bowing of weight-bearing legs.
o Osteopenia.
what are the types of hyperparathryoidism?
o Primary – PTH adenoma.
High PTH, high Ca, low phosphate.
o Secondary – Vitamin D deficiency (renal failure, low light, impaired liver, etc.).
High PTH, low/normal Ca, low/normal phosphate.
o Tertiary – autonomous production of PTH.
High PTH, high Ca, low phosphate (no negative feedback)
what occurs in bone in primary hyperPTism?
bone resorption therefore hypercalcaemia
what occurs to bone in secondary hyperPTism?
renal osteodystrophy e.g. sub-periosteal erosion as a result of chronic renal def
leads to resorption/ increased density
what are the forms of bone resorption?
o Sub-periosteal – affects radial aspect of middle and ring finger phalanges.
o Sub-chondral.
o Intra-cortical.
o Brown tumours.
what forms of bone loss are there?
o Slow – involutional osteoporosis. Bone has time to remodel (bone loss occurs due to mechanical needs).
o Fast – HPT, disuse osteoporosis. Bone loss is too rapid and loss does not cater to mechanical needs.
what are the radiological signs of renal osteodystrophy?
o Osteomalacia and osteoporosis.
o Secondary hyperparathyroidism features.
what are the main 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.
what are the hormones and factors that mediate bone metabolism?
hormones – T4, GH, glucocorticoids, oestrogens, androgens, insulin.
factors – Vit C, cytokines, prostaglandins, growth factors.
what are the bone features of Paget’s?
- Cortical thickening
- Bone expansion
- Coarsening of trabeculae
- Osteolytic, osteoclerotic and mixed lesions
- Osteoporosis circumscripta
- Bone pain, deformity, spontaneous fractures
- May get nerve entrapment, spinal stenosis
- deafness
- Osteogenic sarcoma
- Raised serum alk phos, urinary hydroxyproline, pyridinoline cross-links
