Other Bone Pathologies Flashcards
What is Paget’s Disease?
Larger & overactive osteoblasts & osteoclasts leading to mixed phase bone remodelling & breakdown
Increased woven bone - therefore it is thicker (compresses on structures) and weaker (easily fractured)
What is osteomalacia & Rickets?
Demineralisation of bones leading to soft bones
Caused by Vitamin D deficiency
Less Vit D means need more PTH, increased excretion of phosphate in urine and increased bone resorption
Osteomalacia in adults, rickets in children
What causes Hyperparathyroidism & what is it effect on the bone?
Primary cause - parathyroid hyperplasia or paraneoplastic effects
Secondary causes - prolonged hypercalcaemia or hyperphosphetaemia
Causes increased PTH leading to increased oesteoclast activity - increased bone resorption - risk of microfractures
What cancers commonly metastasise to the bone?
What bones commonly get mets?
What are signs & consequences of bony mets?
Lung, prostate, breast and kidney cancer
Spinal cord, also pelvis, ribs, proximal limb girdles
Bone pain, hypercalcaemia, bone marrow failure, pathological fracture
How can infection be introduced to the bones?
Haematogenous spread
- aysmptomatic bacturia, septicaemia
Non-haematogenous spread
- Direct - surgery or trauma
- indirect - periodontal disease, sinusitis, pressure ulcer
What is the basic pathophysiology of osteomyelitis from haematogenous spread?
There is slow blood flow through the looped sinusoids and capillaries at the diaphysis/epiphysis junction - seeding of bacteria
Bacteria are protected from the immune system (poor penetration of WBCs) allowing abcess formation
Pus builds and causes increase pressure, resulting in lifting of the periosteum
Allows spread along diaphysis
Why is septic arthritis more common in children?
In children there are vessels that cross the growth plate (not present in adults)
This allows seeding of bacteria from the abscess in diaphysis to cross the growth plate and invade the epiphysis and joint
What type of injury increases the risk of seeding of bacteria into the bone?
Microtrauma to the capillaries increases risk of seeding of bacteria as the blood flow is already slow
What organism is the most common cause of bone infection?
What is used to treat it?
S. aureus
Has specific virulence factors allowing it to cause bone infection
Flucoxacillin
What other organisms can cause bone infection in which circumstances?
Pseudomonas - shoe penetration injury, particularly in adolescence
S. agalactiae (GBS) in neonates - exposure in birth cannal
HIB - newbornes and developing countries - not vaccinated
Coagulase negative staphyloccoi - trauma/injury
S. pyogenes (GAS) - post-chicken pox infection, access via skin lesions
TB - developing countries
What groups are most susceptible/have a higher rate of bone infection?
Which group makes up more than 50% of cases?
Children - < 5 yo make up more than 50% cases
Immunocompromised
Sickle cell disease
Indigenous population
What bones are most affected by bone infection?
Fast growing tubular bones - humorous, femur, tibia
Other bones can be affected but less common
What is the presentation of bone infection?
Bone pain
Signs of inflammation
Hx of trauma
Fever
Limp
Non-specific signs in neonates i.e. crying, poor feeding
Pelvic and vertebral infection as late presentation
How can bone infection be diagnosed?
Inflammatory markers - CRP rapidly increases & decreases, ESR steadily increases
Culture - bone, blood and pus aspirate - 50% chance of finding
Imaging
- MRI most accurate but expensive
- XRAY to rule out differentials
- Bone Scan (T-99m dye) more sensitive early on (senesce increased blood flow, inflammation & osteoblast activity
How are bone infections treated?
For gram positive causes - flucloxacilin
- Oral 3 weeks or IV 3-5 days (if complicated)
3rd generation cephlasporins (gram negative causes) or 4th generation (difficult cases)
Rifampicin can be added for synergy in difficult cases
