Bone and Joint Infections Flashcards
If you expect osteomyelitis, what tests should you order?
x-ray
CBC
blood culture
sedimentation rate/CRP
What does a sedimentation rate measure?
inflammation!
TMI: Sed rate, or erythrocyte sedimentation rate (ESR), is a blood test that can reveal inflammatory activity in your body.
When your blood is placed in a tall, thin tube, red blood cells gradually settle to the bottom. Inflammation can cause the cells to clump together. Because these clumps of cells are denser than individual cells, they settle to the bottom more quickly.
The sed rate test measures the distance red blood cells fall in a test tube in one hour. The farther the red blood cells have descended, the greater the inflammatory response of your immune system.
What tests are good early on for osteomyelitis?
bone scan
MRI
What’s the most likely organism causing osteomyelitis?
S. Aureus
maybe Strep
Do you need to perform a needle biopsy for osteomyelitis?
no
How to treat osteomyelitis?
oral antibiotics
What organism is most likely to cause a pathologic fracture?
S. Aureus
If you suspect a pathologic fracture, what specimens should you send to the lab? What culture would NOT be helpful?
send a bone culture; do not use a sinus tract culture, usu not helpful unless you can isolate a single organism
What is the gold standard for determining the cause diagnosis of a fracture?
open bone biopsy
T/F: Sinus tract cultures are a great tool for determining the cause of a bone infection.
No, sinus tract cultures correlate poorly with bone cultures; don’t trust sinus cultures unless the results yield a single organism or S. aureus
If there is “hardware” in the leg prior to a break and subsequent infection, what should be done?
hardware removal, antibiotics, new hardware later
**might be OK if you don’t remove the hardware if the infection is detected early
What is a good antibiotic to put a patient on while waiting for results of a culture for bone infection?
vancomycin
So, prosthetic devices like those inserted in a hip replacement can become infected with MRSA and enterococcus. What should be done in this case?
2 stage replacement w 2-6 weeks b/w surgeries
give antibiotics
Under what circumstances can a prosthesis be retained after debridement?
symptoms <3weeks
stable implant
easy to treat organism
When would it be OK to use single stage replacement for a prosthetic infection?
symptoms <3weeks
soft tissue in good shape
no co-morbidities
easy to treat organism
If an IV drug user comes in with infection, what bugs do you expect? What imaging study might be helpful? What drugs would you prescribe?
staph > strep > Gram negative bacteria > fungi;
MRI;
nafcillin + gentamycin or
vancomycin + gentamycin
Why might a patient with a vertebral osteomyelitis complain of mid-thoracic radicular pain?
spinal ache - first sign of epidural abscess
When might you use debridement for vertebral osteomyelitis?
instability abcess cord compression cervical infection neuro signs and symptoms
For vertebral osteomyelitis, what antibiotics would you use and for how long?
quinolones for 4 weeks or longer if hardware in place or abscesses not drained
Why might it be bad to order an MRI while a spinal osteomyelitis is healing?
MRI less than 4 weeks into Rx often look worse even in patients improving – don’t order! Follow clinically.
MRI later – don’t follow bone changes – often progress. Focus on epidural and soft tissue changes – if these are equivocal or progress suggests failure
Gold standard for osteomyelitis?
histopathologic evidence with supporting microbial data
**usu the diagnosis rests on clinical, laboratory, and radiographic date
In diabetic foot infections, what are some exam findings that predict bone involvement?
larger (>2cm) and deeper suggest osteomyelitis
ESR >70
probe to bone
What are the best imaging modalities for diabetic foot infections?
plain film
CT
MRI
nuclear medicine studies
When are plain films useful? Why are they not helpful in cases of acute osteomyelitis?
in chronic infection, like sclerosis or periosteal elevation and sequesta; you need like 30-50% mineral loss for anything to be notable of x-ray
Best method for detecting small areas of necrosis, gas, foreign bodies; metallic foreign bodies compromise the image
CT
Best single test for diabetic foot infections; great sensitivity
MRI
Will be positive on bone scan immediately and in 15 minute phase
soft tissue infection
Will be positive on bone scan immediately, 15 minute phase, and in delayed (>4hour) images
osteomyelitis
What organisms are likely involved in diabetic foot ulcers that are chronically infected or necrotic and malodorous?
S. aureus, B strep, enterococci, enterobacteriaceae, pseudomonas species
other anaerobic species
How to treat nasty diabetic foot and bone ulcers?
surgical debridement
re-vascularization if needed
long-term antibiotics
**AB alone probably insufficient
What antibiotics should you use for diabetic foot infections?
- always cover gram +, esp staph
- add gram - coverage for chronic wounds or if pt previously treated with anbx for moderate/severe wounds
- anaerobic coverage if necrotic wound or feculent odor
Is anbx coverage for enterococci and pseudomonas usually necessary in diabetic foot infections?
not usually; if enterococci is the only organism, OK; if pseudomonas is present and the pt is not improving, OK
Duration of anbx therapy for diabetic foot infections?
4-6 weeks or longer
MRI of his spine reveals complete destruction of T6, a 20 anterior acute angle deformity and a large para-spinal fluid collection. Biopsy reveals granulomas, no AFB. What is going on??
TB - patient needs anti-TB therapy and surgery
Responsible for 1/3 of cases of skeletal TB.
Infection begins in the anterior aspect of the vertebral body leading to anterior collapse and spread of the infection along the anterior ligament
Most cases involve the lumber and lower thoracic spine
50% of cases have associated abscesses (if calcified is diagnostic for TB)
Pott’s disease
Indications for surgery in Pott’s disease?
neuro deficits
instability
cervical spine disease
medical therapy failure
In developed countries (blank) is a disease of adults and represents reactivation of an old focus of infection.
In the developing world most cases occur in patients who recently acquired TB. Therefore, most cases occur in childhood. Many patients give a history of recent trauma to the involved area.
skeletal tuberculosis
Accounts for 35% of cases of extra-pulmonary TB and 2% of all cases of TB
Indolent course, average duration of symptoms prior to diagnosis: 16 to 19 months.
Local swelling, pain, fluctuance; systemic symptoms (fever, sweats, etc) often absent.
Pulmonary disease present in 30%. PPD+ in > 85%
skeletal TB
How can you differentiate infected vs non-infected joint fluid?
aspiration –> gram stain –> culture
In 80% of cases of RA, what bug can cause infection of joints? Does the joint need to be drained?
S. aureus; serial aspiration or open procedure
A 23 year old female reports to the ER with 2 days of diffuse arthralgias, low grade fever and then the development of swelling and increased pain in her right knee and wrist. She has a new boyfriend. Diagnosis?
gonorrhea
What are some risks for gonorrhea infection?
female
menstruating
complement deficinecy
Gout has (blank) birifringent crystals, while pseudogout has (blank) birifringent crystals
negative; positive
When would glucose be low in a synovial fluid analysis?
inflammatory arthritis
septic arthritis
Should joints be drained if gonorrhea suspected?
yes
What anbx should ya give for gonorrhea?
ceftriazone for 7-10 days
**treat partner, too
