Clinical Inv: Bone, Joint, Soft Tissue Flashcards
Soft Tissue lab work?
Culture of superficial skin at site of infection is rarely helpful in identifying specific pathogens- it will often come up polymicrobial.
+If you suspect bacteremia or sepsis, then blood cultures would be important to consider
+Biopsy is sometimes helpful, Send tissue samples to lab
+Labs such as CBC, BMP, etc are typically normal or non-specific as to the exact cause
Septic Joint or Septic Arthritis labs?
+Do not hesitate to perform joint arthrocentesis to make the diagnosis if there are no contraindication otherwise
+Be able to interpret fluid analysis results
Septic Joint DDx
Non-gonococcal
Gonococcal arthritis
Gout or pseudogout
Knee trauma
RA
Rheumatic fever (rare, but still on boards)
Adult Still’s disease
Lyme disease
Septic Joint DDx
Gonococcal
Endocarditis
Sarcoidosis
Meningococcemia
Acute Monoarthritis DDx
Inflammatory:
Infection
Crystal-induced: gout or pseudogout
Reactive arthritis
Seronegative spondyloarthropathy, connective tissue disease
Acute Monoarthritis DDx
Non-inflammatory
Trauma
Nontraumatic bleeding, eg. Coagulopathy
Sickle cell crisis
Synovial fluid Gram stain
A positive Gram stain confirms the diagnosis of septic arthritis, but is only positive in 50% of cases; therefore, a negative Gram stain does not rule out septic arthritis
Synovial fluid culture:
In cases of non-gonococcal septic arthritis, the synovial fluid culture is positive over 60% of the time
Synovial Crystals:
The presence of crystals in synovial fluid suggests crystal arthritis. Of note, patients with crystal arthropathy (e.g., underlying gout or pseudogout) can also develop concurrent septic arthritis; the presence of crystals on arthrocentesis does not exclude septic arthritis
Types of osteomyelitis and pathogenesis:
Hematogenous osteomyelitis
Vertebral osteomyelitis
Non-hematogenous osteomyelitis
Hematogenous osteomyelitis
Develops in the setting of bacteremia (e.g., endocarditis or another endovascular infection).
Vertebral osteomyelitis:
Develops due to hematogenous spread, local tissue invasion (e.g., from a psoas abscess), or direct inoculation after a procedure.
Non-hematogenous osteomyelitis:
Develops in the setting of poor wound healing, such as diabetic foot ulcers and sacral decubitus ulcers, followed by direct inoculation from the skin and soft tissue to the exposed bone.
Osteomyelitis DDx (9)
Cellulitis
+Septic arthritis
+Gout
+Diabetic or arterial insufficiency ulcer
+Tuberculous or mycotic bone infection
+Rheumatic fever
+Metastatic cancer
+Multiple myeloma
+Avascular necrosis
Osteomyelitis Investigations - most sensitive test?
MRI is the most sensitive imaging modality.
