Bone and Joint Infections Flashcards
What is septic arthritis?
- most common destructive arthroplasty
- mostly mono-articular (90%) poly (10%)
- in extremes of ages (very young and very old)
- increase intra-articular injections/joint replacements/investigations have greater risk of infection so increased in adults
What is acute septic arthritis?
- pyogenic
- mild in most cases
- limitation of joint movement
- synovial effusion = swelling
What is the difference between acute and chronic septic arthritis?
- acute = pyogenic
- chronic = non-pyogenic
What is the pathogenesis of septic arthritis?
- most common = infection via haematogenous route
- other mechanisms involve adjacent osteomyelitis, penetrating trauma..
What are the common organisms which destroy bones/joints?
- gram positive cocci = s. aureus, streptococci (pyogenes, pneumonia, Group B)
- gram positive bacilli (clostridium sp.)
- gram negative cocci (Neisseria gonorrhoea)
- gram negative bacilli (Escherichia coli, pseudomonas aeruginosa, haemophilus influenzae (before immunisation), eikenella corrodens (human bites))
What is the most common causative organism for septic arthritis?
- staph apart from 16-50 year olds where gonococcus is
What are the predisposing factors of septic arthritis?
- previous joint damage
- untreated systemic infection
- condition affecting blood supply to joint
Which joints are most commonly affected by septic arthritis?
- knee
- also hip/ankle/eblow
- rarely wrist/shoulder/fingers
How is septic arthritis diagnosed?
- elevated ESR/CRP
- neutrophilia (inflammation marker)
- synovial fluid examination (turbid or purulent, leukocyte no., glucose)
- blood culture
- culture other sites
What may be seen in radiology for septic arthritis?
- destruction changes seen at least after 2 weeks so not useful in early stages
- soft tissue swelling, erosion of articular cartilage, associated soft tissue swelling
- mycobacterial infection = joint space narrowing, effusion, erosions, cyst formation
What is the differential diagnosis of septic arthritis?
- acute rheumatoid arthritis
- gout
- chondrocalcinosis
What is the treatment for septic arthritis?
- drainage of joint
- antibiotics (start with broad spectrum if stain not known, IV 3-4 weeks)
What is reactive arthritis?
- reiter’s arthritis
- reactive to bacteria or post-infections
- common in presence of HLA-B27
- proceeded by genitourinary infection (STI - chlamydia trachomatis or enteric infections (enteritis - salmonella)
- sterile inflammatory process
- usually extra-articular symptoms (lower back pain and diarrhoea)
How can TB cause joint infection?
- often goes into soft tissues secondarily
- slow growing but very destructive
- Pot’s disease = vertebra destruction as TB on spine = spinal compression
How is osteomyelitis spread?
- haematogenous
- contiguous spread from infected focus
What are the types of osteomyelitis? Who are they more common in?
- acute haematogenous = primarily in children
- contiguous focus = more common in young adults
- spinal = adults over 45
Where do lesions form in osteomyelitis?
- at metaphysis of EGP where there is a rich blood supply as constant remodelling
- abscess grows and pushes/dislodges periosteum
What are the consequences of an osteomyelitis abscess?
- microabscess = bone tries to prevent spread making a bony barrier
- however bacteria eventually eats through
What are the predisposing factors of osteomyelitis?
- impairment of immune surveillance (malnutrition, extremes of age)
- impairment of local vascular supply (diabetes mellitus, venous stasis, radiation fibrosis, sickle cell disease)
What are the clinical features of osteomyelitis?
- haematogenous spread in long bone (abrupt onset of high fever, decreased limb movement, adjacent joint effusion)
- local and non-specific pain
- elevated neutrophil count
- elevated ESR
What are the clinical features of chronic osteomyelitis?
- local bone loss
- persistent drainage through sinus
What are the rare complications of chronic osteomyelitis?
- squamous cell carcinoma
- amyloidosis
What is Broca’s abscess?
- lytic lesion in oval shape
- surrounded by thick dense reactive sclerosis
What are the investigations made in diagnosis of osteomyelitis?
- bone biopsy
- blood cultures
- neutrophil count/ESR
- radiography/isotope scan
What is the management of osteomyelitis?
- surgical debridement to remove dead bone
- reconstruct bone (allograft to autograft)
- antibiotics for 4-6 weeks
What antibiotics are used for osteomyelitis?
- vancomycin
- flucloxacillin (gram positive)
- clindamycin (oral and foam)
- piperacillin (broad spectrum IV)
- ciprofloxacin (broad spectrum)
How can a prosthetic bone have a joint infection?
- in osseous tissue adjacent to prosthesis
- bone contiguous with prostehesis
- from haematogenous spread
- from local inoculation at surgery or post-op spreads from wound sepsis
What are the risk factors of infection in prosthetic bone and how are they prevented?
- prior surgery at site of prosthesis -> eliminate infected foci before surgery
- RA -> use peri-operative antibiotics
- diabetes mellitus -> use laminar flow theatre ventilation
- obesity -> exhaust ventilated body suits worn by surgical team
- malnutrition -> prophylaxis
What are the clinical features of prosthesis joint infection?
- usually gradual onset with progressive pain
- occasional sinus development
What are the investigations for prosthesis joint infection?
- x-rays (lucencies at bone cement interface and change in component composition)
- cement fractures
- periosteal reactions
- gas in joint
What is the management for prosthesis joint infection?
- simple debridement and retain prosthesis plus antibiotics (20% success)
- removal of prosthesis, antibiotics for 6 weeks, re-implantation (90% success)
- removal of prosthesis, immediate reimplantation, antibiotics (70% success)
