Osteomyelitis; Septic arthritis Flashcards
[] is the most common causative pathogen in osteomyelitis.
Staph aureus is the most common causative pathogen in osteomyelitis.
What are the two types of osteomyelitis? [2]
State common causes for each
There are two types of osteomyelitis as defined by their source: haematogenous and nonhaematogenous.
Haematogenous:
* Indwelling intravascular catheter (e.g. Hickman line)
* Haemodialysis
* Endocarditis
* IV drug use
Non-haematogenous:
* Skin ulcers
* Trauma
* Surgery (especially when foreign material is placed)
* Animal / insect bites
Which bones are more commonly affected by haematogenous vs non-haematogenous osteomyelitis? [2]
Haematogenous:
- axial skeleton, primarily the vertebral bones
- sternum and pelvis
Non-Haematogenous:
- ares of trauma / surgery
Clinical features of acute [3] and chronic osteomyelitis [3] ?
Acute osteomyelitis:
- Pain is the most common symptom
- Warm and erythema
- Systemic symptoms
Chronic osteomyelitis:
- Tends to present only with local symptoms such as swelling, erythema and pain
- Systemic symptoms such as fever are often ABSENT
- Often secondary to DM vascular injury - diabetics with ulcers >2cm2 are very likely to have osteomyelitis, even if no bone is visible
- A draining sinus tract may be seen - this is pathognomonic of osteomyelitis
-
In patients with a history of intravenous drug use, what organism is the most common cause for osteomyelitis?
Salmonella spp.
S. aureus
P. aeruginosa
E. coli
In patients with a history of intravenous drug use, what organism is the most common cause for osteomyelitis?
Salmonella spp.
S. aureus
P. aeruginosa
E. coli
Investigations for osteomyeltis? [+]
Serology:
- Acute = raised WCC / CRP
- Chronic = often has normal WCC
- Blood cultures are positive in around half of cases
X-ray:
- Acute = first two weeks of infection may show normal
- Soft tissue swelling, osteopaenia (bone thinning), bone destruction, periosteal reaction (changes to the surface of the bone), endosteal scalloping and new bone apposition
MRI:
- Best imaging for dx
- Sequestrum: Refers to a dead piece of devitalised bone that has been separated (i.e. sequestered) due to necrosis from the surrounding bone.
- Involucrum: New growth of periosteal bone around a sequestrum.
- Cloaca: An opening in an involuvcrum that allows the internal necrotic bone and pus to discharge out.
Label A-C
Sequestrum: Refers to a dead piece of devitalised bone that has been separated (i.e. sequestered) due to necrosis from the surrounding bone.
Involucrum: New growth of periosteal bone around a sequestrum.
Cloaca: An opening in an involuvcrum that allows the internal necrotic bone and pus to discharge out.
Describe the difference between sequestrum vs involucrum? [1]
A sequestrum is the necrotic bone which has become walled off from its blood supply and can present as a nidus for chronic osteomyelitis.
An involucrum is a layer of new bone growth outside existing bone seen in osteomyelitis.
What is A? [1]
Sequestrum
What is shown in this image? [1]
draining sinus tract
What is the arrow pointing to? [1]
involucrum: formation of new bone around an area of bony necrosis
What is the arrow pointing to? [1]
sequestrum: devitalized bone that serves as a nidus for infection
Describe the treatment for osteomyelitis [3]
Antibiotics +/- surgical debridement forms the mainstay of management.
Abx:
- Should be held until bone cultures are completed
- Guided by microbiology
- BNF: flucloxacillin for 6 weeks; possibly with rifampicin or fusidic acid added for the first 2 weeks
- Chronic osteomyelitis usually requires 3 months or more of antibiotics.
- Clindamycin in penicillin allergy
- Vancomycin or teicoplanin when treating MRSA
Surgery:
- More common in non-haem. spread
- infected necrotic bone must be removed
- Irrigation & debridement - sequestrum must be eliminated from the body, or infection is likely to recur; replace dead bone and scar tissue with vascularized tissue
What are the indications for surgery in osteomyelitis? [3]
- Failure to respond to antibiotic therapy
- Formation of discrete abscess
- Neurological deficit (vertebral osteomyelitis)
S. aureus
Salmonella
Describe investigations for septic arthritis? [2]
Joint aspiration is key and should be obtained prior to antibiotics (whenever possible):
- Also decompresses joint space
- synovial fluid appearance: often yellow/green and turbid on aspiration compared to uninfected fluid which is clear and usually colourless.
- Cultures of synovial fluid in cases of gonococcal septic arthritis yield positive results in only 25% of cases.
- Synovial fluid WCC: is often raised with neutrophil predominance. WBC: >50 000 cells/mm3 with Neutrophils: >75 %
A patient presents with ?osteomyelitis. An MRI is performed.
What does the arrow point at? [1]
involucrum: formation of new bone around an area of bony necrosis
A patient presents with ?osteomyelitis. An MRI is performed.
What does the arrow point at? [1]
sequestrum: devitalized bone that serves as a nidus for infection
Describe the positions of a sequestrum vs a involucrum [2]
A sequestrum is the necrotic bone which has become walled off from its blood supply and can present as a nidus for chronic osteomyelitis.
An involucrum is a layer of new bone growth outside existing bone seen in osteomyelitis.
