MSK & Rheumatology Flashcards
cortical v trabecular bone?
cortical
- compact
- only spaces for cells and blood vessels
trabecular
- spongy
- many holes filled with bone marrow
woven v lamellar bone
woven
- made quickly
- disorganised
lamellar
- made slowly
- organised
adult bone composition?
50-70% mineral - HYDROXAPATITE (crystaline form of calcium phosphate)
20-40& organic mix - type 1 collagen and non collagenous proteins
5-10% water
MINERAL = STIFF COLLAGEN = ELASTIC
OSTEOARTHRITIS (OA):
Cartilage loss with accompanying periarticular (around the joint) bone response
• Inflammation of articular (actually in contact with bone) and periarticular structure
and alteration in cartilage structure
epidemiology of oesteoarthiritis?
- > 55
- F>M
risk factors of oesteoarthritis
- joint hyper-mobility
- diabetes
- increasing age
- genetic predisposition
- obesity -> pro inflammatory state
- occupation
- local trauma
- inflammatory arthritis
pathophysiology of oesteoarthisits?
Progressive destruction and loss of articular
cartilage with an accompanying periarticular
bone response
- Cartilage is a matrix of collagen fibres,
enclosing a mixture of proteoglycans and water;
it has a smooth surface and is shock-absorbing
- Under normal circumstance, there is a dynamic
balance between cartilage degradation by wear and its production by
chondrocytes
- Early in the development of OA this balance is lost, the cartilage become oedematous
- Subsequently focal erosion of cartilage develops and chondrocytes die
Cartilage ulceration exposes the underlying bone to increased stress,
producing micro-fractures and cysts
- The bone attempts repair but produces abnormal
SCLEROTIC SUBCHONDRAL BONE and overgrowths
at the joint margins which become calcified - known as
OSTEOPHYTES
There is also some secondary inflammation
clinical presentation of oesteoartheritis?
Symptoms are usually gradual in onset and progressive
- Joint pain - made worse by movement and relieved by rest
- Joint stiffness after rest (gelling)
- transit morning stiffness
- nodes and bone swellings at DIPJ
investigations of oesteoarthritis
- CRP can be elevated
- negative RF and ANA
- XRAY (LOSS (loss of joint space, osteophytes, subarticular sclerosis and subchondral cysts)
treatment of oesteoarthritis?
- non medical; exercise, weight loss, alternative therapy
- pharm - paracetamol, opiods and intra-articular corticosteroid injections
- surgery; arthroscopy, arthroplasty
rheumatoid arthritis
A chronic systemic AUTOIMMUNE disorder causing a SYMMETRICAL
POLYARTHRITIS
disease of synovial joints
epidemiology of rheumatoid arthritis?
- 30-50 yrs peak age
- F>M
risk factors for rheumatoid arthritis?
- female -> oestrogen
- genetics -? HLA DR4
- smoking
- family history
- immune system
pathophysiology of rheumatoid arthritis?
RA is primarily a synovial disease and synovitis
(inflammation of the synovial lining) occurs when
chemoattractants produced in the joint recruit
circulating inflammatory cells
- Over-production of TNF-alpha leads to synovitis
and joint destruction - the interaction of
macrophages, T and B lymphocytes drives this overproduction In RA the synovium becomes greatly thickened and becomes infiltrated by
inflammatory cells
Generation of new synovial blood vessels is induced by angiogenic
cytokines and activated endothelial cells produce adhesion molecules which
FORCE LEUCOCYTES into the synovium - where they can trigger
inflammation
- The synovium proliferates and grows
out over the surface of the cartilage
(past the joint margins), producing a
tumour-like mass called ‘pannus’
- This pannus of inflamed synovium
DAMAGES the underlying cartilage
by blocking its normal route for
nutrition and by direct effects of
cytokines on the chondrocytes
- The cartilage becomes thin and the underlying bone exposed
- The pannus DESTROYS the articular cartilage and subchondral bone
resulting in bony erosions
clinical presentation of rheumatoid arthritis?
- usually MCP and PIP
- joints warm and tender
- morning stiffness > 30 mins
- symmetrical
- hand deformities; swan neck
- pain eases with use
- extra-articular; lungs (pleural effusion), heart (pericarditis), eyes (scleritis), neurological (carpal tunnel, cord compression, peripheral sensory neuropathies), kidneys (amyloidosis) and subcutaneous nodules in skin
investigations for rheumatoid arthritis?
- FBC ; low hB, ESR AND CRP raised, RF positive and ANTI CCP positive
- XRAY (soft tissue swelling, joint space narrowing and peri-articular erosions)
- MRI and USS
rheumatoid arthritis tretament?
- lifestyle changes
- pain management -> NSAIDs and PARACETAMOL
- corticosteroids (can risk osteoporosis)
- DMARD (inhibits inflammatory cytokines) eg METHOTEXTRATE (GOLD STANDARD)
- biological therapy (TNF alpha blocker eg, INFLUXIMAB) , B cell inhibitors (RITUXIMAB - CD20)
osteoporosis?
A systemic skeletal disease characterised by low bone mass and a micro
architectural deterioration of bone tissue, with a consequent increase in
bone fragility and susceptibility to fracture
bone mineral density (BMD) MORE than 2.5 standard deviations
BELOW the young adult mean value (T score < 2.5)
osteopenia?
Pre-cursor to osteoporosis characterised by low bone density - Defined as BMD between 1-2.5 standard deviations BELOW the young adult mean value (-1< T score < 2.5)
osteomalacia?
Poor bone mineralisation leading to soft bone due to lack of Ca2+
epidemiology of osteoporosis?
- > 50 yrs
- F>M (women lose trabecular with age)
- Caucasian and asians
risk factors for osteoporosis?
- old age
- women
- family history
- smoking
SHATTERED
S - steroid use
H - hyperthyroidism/hyperparathyroidism (increase bone turnover)
A - alcohol and tobacco
T - thin (BMI <22)
T - testosterone decreased
E - early menopause
R - renal or liver failure
E - erosive/inflammatory bone disease
D - dietary calcium decreased
pathophysiology of osteoporosis
Osteoporosis results from increased bone breakdown by osteoclasts and
decreased bone formation by osteoblasts, leading to loss of bone mass
Genetic factors are the SINGLE MOST SIGNIFICANT INFLUENCE on peak
bone mass
Bone strength is determined by bone mineral density, bone size and bone quality (mineralisation)
Oestrogen deficiency - Postmenopausal osteoporosis:
• Results in increased numbers of remodelling units (osteoclasts),
premature arrest of osteoblastic synthetic activity and perforation of
trabeculae with a loss of resistance to fracture
• High bone turnover (resorption greater than formation)
Changes in trabecular architecture with ageing:
• Decrease in trabecular thickness - as we age the strain is felt on bones
from head to tail, in response, we tend to preferentially preserve
VERTICAL TRABECULAE and LOSE HORIZONTAL TRABECULAE
clinical presentation of osteoporosis
- fractures
- colles fracture of wrist