Bone Disease Flashcards
Describe basic bone physiology, including
- structure (including long bones)
- cell types and function
- periosteum structure and anatomy
- composition of bone matrix
- Outer layer (compact/cortical) and inner layer (spongy/trabecular). Long bones also have a marrow (medullary) canal with bone marrow. Diaphysis (shaft) vs epiphysis (bone ends)
- osteoblasts (synthesis), osteoclasts (degrade), osteocytes (OBs when engulfed in matrix)
- osteons (concentric laminae, rings), which have Haversian canals (transmitting blood vessels and nerves)
- osteoid (35%, type I collagen), mineral (65%, hydroxyapatite - calcium and phosphorus)
Describe the metabolic processes of
- bone remodelling
- vitamin D metabolism
- OBs release RANKL, binding to OCs. OPG binds to RANKL, preventing it from binding to OCs, allowing OBs to lay down bone
- UVB light -> binds to D-binding protein (DBP), transfers to liver -> liver breaks down to 25(OH)D (from 25(OH)ases) -> kidney adds a branch (1a-hydoxylase enzyme to 1,25(OH)D) -> Increased GI absorption of Ca2+ and activation of OCs
Describe three main developmental disorders of bone:
- achondroplasia
- osteogenesis imperfecta
- osteopetrosis
- aka dwarfism. gain of function of FGFR3, inhibiting endochondral growth. limb lengthening, deformity correction (i.e. scoliosis)
- aka brittle bone disease. autosomal dominant deficiency of collagen type I. multiple fragility fractures, short stature/deformity, can be mistaken for NAI
- aka marble bone disease. resorption is impaired, meaning bone is brittle
Describe the key components of osteoporosis (definition, predisposing factors, pathology, investigation, management).
- bone mass < 2.5 standard deviations normal
- menopause (oestrogen stimulates osteoblasts), steroids, aging, vitamin D deficiency
- osteoblasts lose efficiency causing decreased bone mass
- DEXA is gold standard. CT also used
- prevent (exercise, Ca2+/vit D, general life improvement), drugs (bisphosphonates)
Describe the key components of Paget’s disease (pathology, presentation, investigation and management)
- osteoLYSIS, mixed stage, osteoSCLEROSIS. Rapid overcompensation by OBs in final stage makes bone unstable.
- 60-80% asymptomatic. Pain to bone, leontiasis ossea (lion face), platybasia (invagination of skull base), bowing and distortion of femur. May lead to cardiac disease (HFpEF).
- can be diagnosed with X-ray etc. also low vitamin D and high ALP/Ca2+
- calcitonin and bisphosphonates. surgery for deformity or extreme pain
Describe the key components of rickets and osteomalacia (causes, presentation, management).
- vitamin D deficiency (dietary, lack of sunlight) and rarer causes (refeeding syndrome, alcohol abuse, malabsorption)
- symptoms (bone pain, pathological fracture, hypocalcaemia, waddling gait), bloods (high ALP and PTH, low Ca2+ / PO4- / 1,25(OH)
- vitamin D therapy (loading dose, supplementary preventative weekly doses)
*Describe the key components of osteomyelitis with the main causative organisms.
Fracture or haematogenous spread.
Staph aureus is most common, followed by Haemophilus (children) and Salmonella (sickle cell)
Immobilize and debridement, usually with bone biopsy and antibiotics (teicoplanin, flucloxacillin)
Describe the key components of bone tumours (types and key feature of each, shared presenting feature, investigation, DDX by age, and treatment).
Benign
- osteoid osteoma: sclerotic halo in young men
- osteochondroma: pedunculated on a stalk
- chondroma: solid circumscribed translucency, tumour of cartilage
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Malignant
- osteosarcoma: codman triangle, proximal tibia/distal femur, most common tumour
- chondrosarcoma: malignant cartilage, usually pelvis or proximal femur
- Ewing’s: ‘onion skin’ pattern, t(11:22)
- fibrosarcoma occurs in already abnormal bone (infarct, fibrous dysplasia, Paget’s etc)
- giant cell: ‘soap bubble’ on X-ray
——-
- x-ray -> DEXA/MRI
- for metastasis: find the primary tumour. May require breast/PR exam, CXR (lung), FBC/U&E/LFTs, electrophoresis (myeloma)
——-
- surgery to remove tumour and adjuvant therapy
Describe the key components of osteoarthritis (pathology, clinical features (including hand OA), investigation, management).
- wear and tear of cartilage, causing it to be replaced by bone. ulceration may cause subchondral cysts
- achy pain worsening with use, morning stiffness, limitation of movement, crepitus, joint effusion, and bony instability
- Heberden and Bouchard nodes, CMC thumb joint causes ‘squaring’ of hand
- most likely diagnosis for patients > 45 with typical activity like pain. X-ray shows LOSS (loss of joint space, osteophytes, subchondral cysts, subarticular sclerosis
- lifestyle changes (e.g. losing weight), pain Mx (heat, ice packs, NSAIDs + PPIs), one-off steroid injection. Rarely arthoscopy
Give the DDX by age of tumours, and the most common areas of metastasis.
DDX by age - 1: neuroblastoma - 1-10: Ewing's - 10-30: osteosarcoma - 30-40: fibrosarcoma BLT with a Kosher Pickle: breast, lung, thyroid, kidney, prostate
Which type of bony tumour is indicated by the following feature?
Exocytosis (bony stalk)
Osteochondroma (benign)
Which type of bony tumour is indicated by the following feature?
Sclerotic halo
Osteoid osteoma (osteoblastoma)
Which type of bony tumour is indicated by the following feature?
Codman triangle, sunburst appearance
Osteosarcoma
Which type of bony tumour is indicated by the following feature?
Onion skin appearance
Ewing’s sarcoma (t11:22)
Which type of bony tumour is indicated by the following feature?
Soap-bubble appearance
Giant cell tumour
