Bone and Joint Infections Flashcards
what is septic arthritis
Septic arthritis, also known as joint infection or infectious arthritis, is the invasion of a joint by an infectious agent resulting in joint inflammation.
how many people experience septic arthritis
8 per 100,000 in UK, higher in developing countries
How old are the people experiencing septic arthritis
45% are older than 65 years
What are the types of septic arthritis
Mono-articular 90%
Poly-articular 10%
can also have acute and chronic
what is more common in septic arthritis mono-articular or poly-articular
Mono-articular 90%
describe the symptoms of acute septic arthritis
pyogenic
mild (60 - 80% of cases)
> 39oC (1/3rd of cases)
Limitation of joint movement
Swelling (synovial effusion)
describe chronic septic arthritis
usually non pyogenic (not pus production)
- Can be due to TB, TB is slow growing
- joint does not feel hot and instead it feels cold
What does pyogenic stand for
involving or relating to the production of pus.
Why does septic arthritis affect the elderly population more
45% in the elderly population this is because they have more damage to the joints and rubbing on the periosteum tearing the synovial membrane
what is the most common joint affected by septic arthritis
Knee joint
what is the pathogenesis for septic arthritis
Infective organism reaches joint via blood supply is the most common pathogenesis
- can have direct contamination or post operative infection as well
- can spread from muscle or connective tissue into he bone
- untreated systemic infection
- penetrating trauma - can have an open feature this tears the skin and allows bacteria from the skin to enter the blood stream and into the joint
name the common organisms that cause septic arthritis
Gram positive cocci
- Staphylococcus aureus
Streptococci
- Pyogenes, Pneumoniae, Group B
Gram positive bacilli
- Clostridium sp
Gram negative cocci
- Neisseria gonorrhea
Gram negative bacilli
- Escherichia coli
- Pseudomonas aeruginoa
- Eikenella corrodens (human bites)
- Haemophilus influenza (paediatric before immunization)
what bacteria is the most common organism to cause septic arthritis
Staphylococcus aureus - causes greater than 90% of cases
how does Staphylococcus aureus and other bacteria cause septic arthritis
- release pro-inflammatory cytokines
- bacterial cell wall proteins form a super antigen that activate immune cells that create lots of cytokines that damage the joint
- form adhesions that allow them to spread into the bone
what is commonly affected by septic arthritis
Most commonly: knee
Also: hip, ankle, elbow
what joints are infrequently affected by septic arthritis
Infrequent: wrist, shoulder, fingers
what do the laboratory results show in septic arthritis
- Elevated ESR
- Neutrophilia
- turbid or purulent
- leukocytes > greater than 50,000mm3 = predominelty neutrophils
- gram stain positive in one third
- <25mg/dL glucose (much lower than serum)
- blood culture positive in one - to two thirds
- culture other sites such as urethra and biopsy
what can you see in radiology for septic arthritis
- may see soft tissue swelling
- joint capsule distension
destructive changes seen after at least two weeks
- erosion of articular surface
- associated tissue swelling
in radiology what would you see in a mycobacterial infection
joint space narrowing
effusion
erosions
cyst formation
why do you use a radiograph to look for septic arthritis
- do it to rule out anything else
what can you see in an MRI for septic arthritis
- joint diffusion and swelling
- abscess of cysts filled with bacteria
what are differential diagnosis to septic arthritis
acute rheumatoid arthritis
gout
chondrocalcinosis
What is the treatment for septic arthritis
Drainage
- wash out multiple times with sterile saline
- wash it out until you get a dry tap and nothing else is coming out
Antibiotics
- depends on Gram stain and patient background
- IV 3-4 weeks
- Possibly start with broad spectrum modify when Gram stain known
what is another word of reactive arthritis
Reiter’s arthritis
describe reactive arthritis (Reiter’s arthritis)
- reactive or post infectious
- common in presence of HLA-B27
- sterile inflammatory processes - no infection takes place after infection
- usually has extra-articular symptoms
what HLA is reactive arthritis (Reiter’s arthritis) associated with
HLA-B27
what infections does reactive arthritis (Reiter’s arthritis) usually proceed
Preceded by enteric or genitourinary infection
- STI (chlamydia trachomatis)
- Enteritis (salmonella, campylobacter etc)
how does TB affect the joints
TB affects the lungs and causes lung infections with granulomas
- these granulomas can spread out into the bone
- tend to go to the vertebrae
What two vertebra are commonly affected by TB
T10 and T11
What is Potts disease
Pott disease is tuberculosis of the spine, usually due to haematogenous spread from other sites, often the lung
What is osteomyelitis
Osteomyelitis is an infection that most often causes pain in the long bones in the legs.
How does osteomyelitis spread
- haematogenous spread
- contiguous spread from an infected focus
how does osteomyelitis spread in adults versus in children
Acute hematogenous osteomyelitis - primarily in children
Direct trauma and contiguous focus osteomyelitis – more common in young adults
who is spinal osteomyelitis common in
Spinal osteomyelitis – more common in adults over 45 years
what is acute blood born osteomyelitis primarily in
children
- epiphyseal growth plate are open and this area of bone is quickly growing and twister and therefore you have slow flow of blood through the new bone
- children have a weaker immune system so they are more at risk
- bones are mainly woven bone that is softer and weaker
what are the consequences of osteomyelitis
area of the bone is dead in the centre
- new bone has formed around it to keep the pus and bacteria in place
-
What are the predisposing factors factors that lead to osteomyelitis
Impairment of immune surveillance
- malnutrition
- extremes of age
impairment of local vascular supply
- diabetes mellitus (30-40% of patients)
- venous stasis
- radiation fibrosis
- sickle cell disease (0.36% of patients)
What are the clinical features of osteomyelitis
Hematogenous long bone – abrupt onset of high fever (only 50% in children; less in adults)
Decreased limb movement, adjacent joint effusion (infants)
Hematogenous vertebral and chronic – insidious onset, vague complaints over 1 to 3 months
Local non-specific pain
Elevated neutrophil count (<50% of cases)
Elevated ESR
what is a Brodies abscess
Lytic lesion oval in shape, surrounded by thick dense reactive sclerosis that fades into surrounding bone.
- full of pus
What can progress to chronic osteomyelitis
Haematogenous and contiguous spread osteomyelitis can progress to chronic osteomyelitis
what is the result of chondric osteomyelitis
- local bone loss and persistent drainage through sinus.
- Squamous cell carcinoma and amyloidosis are rare complications
How do you investigate osteomyelitis
Bone biopsy
Blood cultures
- Sinus tract culture NOT reliable
Neutrophil count,
ESR of limited value in monitoring response to treatment
Radiography (changes lag infective course by 2 weeks)
Bone scintingraphy shows the active bone that is being produced
How do you treat osteomyelitis
Surgical debridement to remove dead bone
- Sequestrum
Reconstruct bone (allograft or autograft) - New bone shell involucrum
Antibiotics for 4-6 weeks (at least 2wks IV)
name the antibiotics that you use to treat osteomyelitis and the way in which they are given
Vancomycin cement beads
Flucloxacillin (gram positive)
Clindamycin (oral and foam)
Piperacillin (broad spectrum, IV, IM only)
Ciprofloxacin (broad spectrum
where does prosthetic bone and joint infection occur
Occurs in osseous tissue adjacent to prosthesis
bone cement interface
bone contiguous with prosthesis (cementless devices)
what does prosthetic bone and joint infection result from
local inoculation at surgery or post-op spread from wound sepsis
haematogenous spread
what are the changes in the X ray of the prosthetic bone and joint infection
lucencies at bone-cement interface
changes in component position
cement fractures
Periosteal reactions
gas in joint
how do you investigate a prosthetic bone and joint infection
- X rays
- radio-isotopes scans
- elevated ESR, neutrophil count
- culture of biopsy/joint fluid
how do you manage a prosthetic bone and joint infection
Retain/replace prosthesis
- simple debridement (retaining prosthesis) plus antibiotics - only successful in 20% of cases
- removal of prosthesis, antibiotics for 6wks, re-implantation of prosthesis - 90%+ success (has no joint for 6 weeks)
- removal of prosthesis, immediate re-implantation, antibiotics - 70%+ success
- suppressive long term antibiotics
