lecture 6 - bone & joint infections Flashcards
What is osteomyletis?
Inflammatory process of bone, secondary to infection
Is osteomyletis a primary or secondary infection?
secondary
What are the 3 classification of osteomyelitis, based on duration?
acute, sub-acute, chronic
What are the 2 routes of infection in osteomyelitis?
haematogenous (from the blood), exogenous (from outside of the bone)
What is haematogenous osteomyelitis?
secondary bone infection arising from blood borne bacteria from another source of infection
What are the 2 key host responses to osteomyelitis?
pyogenic/purulence (pus production), granulomatus (granuloma formation)
What is the most common route of infection for osteomyelitis in children?
Haematogenous
Is haematogenous osteomyelitis generally polymicrobial or monomicrobial?
Monomicrobial
Why do children usually develop the haematogenous form of osteomyelitis?
They have vascular stasis (slow moving, convoluted vessels) at their growth plates which allows bacteria to more readily enter the bone
What are the 2 causes of exogenous osteomyelitis?
direct inoculation of the bone, contiguous (spread from local infection)
How does direct exogenous osteomyelitis usually arise?
trauma (compound fracture), surgery
What disease increases the risk of contiguous exogenous osteomyelitis, and why?
Diabetes - poor circulation in the feet can lead to infection that spreads to the bone
Is exogenous osteomyelitis generally polymicrobial or monomicrobial?
polymicrobial
What is the key bacteria that most commonly causes osteomyelitis across all age groups?
Staphylococcus aureus
What are the risk factors for developing osteomyelitis?
immunosupression (diabetes, steroids, cancer, asplenia), age (children & elderly), peripheral vascular disease (smoking, diabetes), injecting drug uses, chronic joint disease, recent surgery/trauma
Where does osteomyelitis typically develop in children?
metaphysis/growth plates of long bones
What is the clinical presentation of osteomyelitis in children?
severe pain, oedema, erythema, pseudoparalysis, fever, nausea, vomiting
What are the potential complications of osteomyelitis?
septic arthritis, dvt (deep vein thrombosis), sepsis, metastatic infection, recurrent osteomyelitis, altered bone growth, fracture
What condition can be caused by the spreading of osteomyelitis to the joints?
septic arthritis
What are the consequences of inflammation in osteomyelitis?
increased pressure diminishes blood supply leading to ischaema & necrosis, osteolysis (bone destruction)
What is the term for breakdown in bone structure?
osteolysis
What can occur in osteomyelitis when pus formation causes pressure and eruption to the skin?
sinus formation
What are the pathological features of chronic osteomyelitis?
sinus, sequestrum, involucrum
What is a sequestrum in osteomyelitis?
Focus of devitalised/dead bone, caused by necrosis
What is an involucrum in osteomyelitis?
Formation of healthy bone over a sequestrum (area of dead bone)
What are the 6 key diagnostic tools for diagnosing osteomyelitis?
1.) aspiration of pus for gram stain/culture
2.) bone biopsy
3.) blood culture (for haematognenous osteomyelitis)
4.) blood count for leukocytosis, raised CRP
5.) imaging (CT, X-ray, MRI)
6.) bone scans
What class of osteomyelitis can often be detected with blood cultures?
haematogenous osteomyelitis
What are the features of a blood count with osteomyelitis?
Leukocytosis (particularly high neutrophil count), raised CRP
What imaging technique is best for early detection of osteomyelitis?
Bone scan - scintigraphy (also MRI)
What is the initial treatment for osteomyelitis?
IV empiric broad-spectrum antibiotics
What is the most common antibiotic first prescribed for osteomyelitis?
Flucloxacillin - because most infections caused by Staph aureus infections
Why must antibiotic treatment change from empiric once the cause is known?
Changing to narrow spectrum antibiotics avoids drug resistance
What is the surgical treatment for osteomyelitis?
debridement - removal of damaged/infected tissue, amputation
What is a Brodie’s Abcess?
Localised region of osteomyelitis forming an abscess
Are Brodie’s abscess acute, sub-acute or chronic?
Sub-acute or chronic - may persist for years until symptoms develop
What is the treatment for sub-acute osteomyelitis, such as Brodie’s Abscess?
long course antimicrobials, surgical debridement
Is chronic osteomyelitis typically monomicrobial or polymicrobial?
Polymicrobial
What is septic arthritis?
pathogenic invasion of a joint causing arthritis
What is septic arthritis characterised by?
colonisation of synovial fluid, inflammation, joint effusion (swelling), synovial membrane erosion
What bacteria most commonly causes acute septic arthritis?
staph. aureus
What bacteria is the most common cause of acute septic arthritis in young sexually active people?
Neisseria gonorrrhoeae
What pathogens typically cause chronic septic arthritis?
HIV, rubella, TB, syphilis, fungi (candida)
What bacteria typically causes early onset (<3 months post-op) septic arthritis following joint surgery/replacement?
staph. aureus
What mechanism of infection occurs in s. epidermidis septic arthritis following joint surgeries?
biofilms
What are the risk factors for developing septic arthritis?
damaged joints, joint replacement surgery, injecting drug use, immunosupression, age
What are the clinical symptoms of septic arthritis?
inflammation/swelling (joint effusion), arthralgia (joint pain)
What are the routes of entry for pathogens causing septic arthritis?
direct innoculation (surgery, trauma, injection), infection of adjacent tissues (e.g. osteomyelitis), haemotogenous spread (in blood)
What are the complications of septic arthritis?
sepsis, osteomyelitis, joint destruction
What are the treatments for septic arthritis?
IV empirical antibiotics, aspiration/drainage, debridement
What is reactive arthritis?
Autoimmune disease in joints following an infection such as STI or gastroenteritis
What STI typically causes reactive arthritis?
Chlamydia
What triad of symptoms are typically present in reactive arthritis?
urethritis/cervicitis of UGT, uveitis/conjunctivitis of eyes, arthritis of large joints/sacroilieum
What is the treatment for reactive arthritis?
anti-inflammatory/immunsuppressant drugs if unresolved
