Bone and Joint Infection Flashcards
What is osteomyelitis
Osteomyelitis = infection of bones
What is septic arthritis?
infection of joints
What is osteomyelitis
Osteomyelitis = infection of bones 25% of open fractures lead to osteomyelitis and
What is prosthetic joint infection?
infection of an artificial joint replacement 1% of joint replacements lead to prosthetic joint infections
Name some Microbes which cause bone and joint infections?
Staphylococcus aureus (including MRSA) Streptococci (β-haemolytic Streptococci species & Strep. pneumoniae) Enteric bacteria (eg. E. coli & Salmonella species) Coagulase-negative Staphylococci (eg. Staph. epidermidis) Mycobacterium tuberculosis (& other Mycobacteria too) Others (Lyme borreliosis, gonorrhoea, brucellosis, fungi, parasites)
Name some risk factors for bone and joint disease
Direct inoculation eg. trauma, medical procedures, skin ulcers Contiguous spread eg. nearby skin or soft tissue infection (SSTI) Haematogenous dissemination eg. IV devices, IV drug abuse Immunosuppression eg. diabetes mellitus, renal failure, sickle cell disease
What microbial factors affect how a bacteria causes infection?
Access : can they reach a suitable site for adherence & invasion ? Adherence : can they stick or bind to a suitable site for invasion ? Invasion : can they penetrate the barriers to infection ? Multiplication : can they replicate to cause infection ? Evasion : can they evade the host immune system ? Resistance : can they resist anti-microbial treatments ? Damage : do they damage host cells (directly or indirectly) ? Transmission : can they be released to infect other hosts ?
MICROBIAL FACTORS SLIDE 13
HOST RESPONSE SLIDE 14
HOST RESPONSE SLIDE 15
If acute infection progresses to become chronic infected bone can become necrotic, what changes in the bone would be seen?
A sequestrum is a piece of dead bone that has become separated during the process of necrosis from normal or sound bone. It is a complication (sequela) of osteomyelitis.
In chronic infection, bacteria in an organic matrix can collect on an inert surface, this is called?
Biofilm
In chronic infection when new bone forms outside sequestrum this is called…
Involucrum
In chronic infection when pus from sequestrum escapes through involucrum via holes this is called..
Cloacae
In chronic infection, infection & pus from cloacae causes skin necrosis, this is called…
discharging sinuses
Explain what would be seen in bone with an acute infection that has progressed to become a chronic infection
Infected bone becomes necrotic = sequestrum
Bacteria in an organic matrix on an inert surface = biofilm
New bone formation outside sequestrum = involucrum
Pus from sequestrum escapes through involucrum via holes = cloacae
Infection & pus from cloacae causes skin necrosis = discharging sinuses
(Biofilms also form on prosthetic joints & assist infection)
HOST RESPONSE CHRONIC OSTEOMYELITIS SLIDE 17
BIOFILMS SLIDE 18
What are the clinical features of inflammation caused by infection?
pain,
swelling,
redness,
warmth,
loss of function
What are the clinical features of osteomyelitis?
- Pain
- swelling
- redness
- warmth
- loss of function
- fever
- pathological fractures
- discharging sinuses
Wha are the clinical features of septic arthritis?
- Pain
- swelling
- redness
- warmth
- loss of function
- fever
- damage to articular surfaces
What investigations would you request if you were suspecting a bone or joint infection?
Full blood count (FBC) & inflammatory markers (eg. CRP)
Other blood tests to look for evidence of severe sepsis
Blood cultures (x2) & skin/ulcer swabs (inc. MRSA)
What imaging studies would you request if you were suspecting bone or joint infection?
Plain radiographs : show late changes well, but not early changes (periosteal reaction is earliest sign visible)
CT scans : show bone changes well, but not as good for soft tissues changes
MR scans : show soft tissue changes well, but not as good for bone changes
Outline treatment steps for bone and joint infection
Manage sepsis
Obtain samples (if possible) before starting antibiotics
Empirical antibiotics = IV flucloxacillin & IV benzylpenicillin
Targeted antibiotics = dependent on culture & sensitivities
Duration of antibiotics = 2-6 weeks IV then 4-6 weeks PO
Septic arthritis requires a joint “washout” (in theatre)
Osteomyelitis requires surgery if chronic changes have developed
Prosthetic joint infections require removal & then replacement
(with antibiotics continued in between operations)
How can we best prevent bone and joint infections in clinical practice?
Prompt diagnosis & treatment of predisposing conditions
Strictest possible aseptic conditions for joint replacements
Antibiotics embedded into cement used for prosthetic joints
