Bone and Joints (pathology) Flashcards
What makes up normal bone?
Outer solid cortical bone Inner trabecular (spongy bone) Outer surface - periosteum Inner space (medulla) contains fat or haemopoietic marrow Inorganic (ca hydroxyapatite) 65% Organic 35%
Functions of bone?
Mineral homeostasis
Houses haemopoietic system
Mechanical - not a static scaffold (constantly remodelled)
What are the types of bone diseases?
Infecs, tumours, trauma/degeneration
Specific derangements of bone’s particular specialised processes and function
Specific bone diseases: disorders of matrix formation, mineralisation and bone turnover
What occurs in the bone remodelling cycle?
Activation of osteoclasts Resorption of bone Death of osteoclasts Formation of new matrix by osteoblasts Mineralisation of new matrix Quiescence
What cells form and resorb bone?
Osteoblasts = form Osteoclasts = resorb
How does bone resorption and bone formation work together?
When is coupling lost?
Coupling of bone formation and resorption usually balances, except where a local imbalance is required for the purposes of growth
Coupling is lost in osteoporosis = loss of bone volume
Types of bone matrix formation diseases?
Mutations in collagen type 1 in bone: - Osteogenesis imperfecta - Also affects ears / eyes / skin / teeth Other abnormalities of bone matrix Mucopolysaccharidoses - Morquio syndrome - Hurler syndrome
How do cartilage matrix formation disorders occur?
Failure of cartilage maturation at the growth plate
Caused by a mutation of fibroblast growth receptor receptor 3 which causes it to be continually activated (it is a negative regulator of bone growth)
Examples of cartilage matrix formation disorders?
Achondroplasia = Autosomal dominant
Examples of mineralisation diseases?
Osteomalacia / Ricketts
Causes of mineralisation diseases?
Caused by deficiency in vitamin D or calcium
Can be dietary or metabolic
Failure to mineralise ->cartilage overgrowth, failure of longitudinal growth
Bone remodelling problems (osteoporosis) due to?
Increased porosity of bone due to a reduction in bone mass Age Hormonal influences Lifestyle (smoking, alcohol) Activity Genetics (Vit D receptor polymorphisms) Nutrition (including malabsorption)
How does osteoporosis occur?
Uncoupling of bone resorption and formation - too much bone resorption, too little bone formation
Loss of trabecular then cortical bone
Complications of osteoporosis?
Fragility fractures (vertebrae, femoral neck, distal radius) Kyphosis (dowager’s hump) Loss of height
Tx of osteoporosis?
Inhibit bone resorption (bisphosphonates)
Increase bone formation (experimental treatments)
Abnormal turnover: Paget’s disease?
Excess turnover
Genetic
Bone infection: Osteomyelitis features?
Complication of compound fractures Blood borne Necrosis of bone fragments New bone formation Sinuses drain pus
What are most tumours in bone?
Metastases
Features of primary bone tumours?
Many are benign
Malignant ones = rapidly fatal
Chondrogenic features?
60% benign:
Osteochondroma
Chondroma
40% malignant:
Chondrosarcoma
Osteogenic features?
13% benign:
Osteoid osteoma
Osteoblastoma
87% malignant:
Osteosarcoma
Examples of malignant bone tumours?
Osteosarcoma
Chondrosarcoma
Ewing’s sarcoma
Undifferentiated sarcoma
Site and age of osteosarcoma?
Metaphyses, most commonly knee
15-30
Site and age of Chrondrosarcoma?
Pelvis, ribs, proximal long bones
Middle aged - elderly
Site and age of Ewing’s sarcoma?
Diaphyses
<20
Site and age of undifferentiated sarcoma?
Mainly metaphyses
Middle aged - elderly
Types of joint diseases?
Infections Crystal arthropathies Chronic inflammatory arthritis Osteoarthritis Tumours
Septic arthritis features?
Can be very trivial causes Insect bites / small cuts near joints punching people in teeth Very painful IV antibiotics +/- drainage
Name the types of crystal arthropathies, features?
Gout = urate crystals 2ndry to raised serum uric acid Pseudogout = calcium pyrophosphate crystals, age related
Chronic inflammatory arthritis features?
Generally autoimmune
Rheumatoid arthritis is the commonest form
There are a variety of other types:
HLA B27-associated diseases such as ankylosing spondylitis and psoriatic arthritis
Systemic lupus and related conditions
Features of rheumatoid arthritis?
Inflammation of synovium
- Lymphocytyes / plasma cells / macrophages
- ‘Pannus’ formation (inflamed fibrous tissue)
Multiple joints
Extra articular features
Joint destruction caused by a cascade of cytokines driven by tumour necrosis factor-alpha
Anti-TNF-alpha antibodies are an effective treatment of severe rheumatoid disease
Osteoarthritis/osteoarthrosis features?
Common Degenerative disease Cartilage erosion - minimal inflam, leads to changes in underlying bone Mechanical Predisposed by pervious joint damage
What occurs in ostoearthritis?
Effective tx?
Fragmentation of cartilage
(‘fibrillation’)
Osteophyte formation
Cysts in underlying bone
The only effective treatment is arthroplasty (surgical removal of the joint and replacement with a prosthesis)
