What is Hematogenous Osteomyelitis
Hematogenous osteomyelitis is a bone infection that occurs when bacteria from a distant site in the body travel through the bloodstream and lodge in bone tissue, most commonly affecting the vertebral spine in adults over 50 years and the metaphysis of long bones in children. 1, 2
Pathophysiology
Route of Infection
- The infection develops when bacteria circulating in the bloodstream seed bone tissue from a remote focus of infection 1, 3
- In vertebral osteomyelitis (the most common form in adults), bacteria typically seed the avascular disc space first, then spread to adjacent vertebral endplates 1
- In children, the metaphysis of long bones is the primary target because looping nutrient vessels create slow blood flow in this region, providing an ideal environment for bacterial adherence and proliferation 2
Age-Specific Anatomical Considerations
- In children ≤18 months: Transphyseal vessels allow infection to spread directly from the metaphysis into the epiphysis and adjacent joint space, explaining why >50% of pediatric cases have concurrent septic arthritis 2
- In older children and adults: The growth plate (physis) typically acts as a barrier preventing epiphyseal spread 2
- In adults >50 years: Hematogenous osteomyelitis represents 3-5% of all osteomyelitis cases but is the most common form in this age group 1
Clinical Characteristics
Microbiology
- Staphylococcus aureus is the predominant pathogen across all age groups, causing the majority of hematogenous osteomyelitis cases 1, 2, 3
- The infection is typically monomicrobial in hematogenous osteomyelitis, unlike contiguous spread osteomyelitis which is often polymicrobial 1, 3
- Age-specific pathogens include Group B streptococcus in neonates, Kingella kingae in children <4 years, and Salmonella species in patients with sickle cell disease 2
Distinguishing Features from Other Forms
- Hematogenous osteomyelitis originates from bloodstream seeding and is usually monomicrobial 1, 3
- Contiguous spread osteomyelitis (such as diabetic foot osteomyelitis) arises from direct extension of adjacent soft tissue infection through compromise of the soft tissue envelope and periosteum, and is typically polymicrobial 1
- Diabetic foot osteomyelitis affects 20% of mild-moderate infections and 50-60% of severe infections, but develops via contiguous spread rather than hematogenous seeding 1
Common Pitfalls
Diagnostic Delays
- Vertebral osteomyelitis diagnosis is often delayed several months and may be initially misdiagnosed as a degenerative process 1
- In children, the classic triad of fever, pain, and diminished mobility occurs in only ~50% of cases, making prompt recognition challenging 2
- Plain radiographs are insensitive for early diagnosis, as bone changes require 10-14 days to become visible; MRI has 82-100% sensitivity and is the diagnostic modality of choice 2
Risk Factors
- Susceptible populations include intravenous drug users, hemodialysis patients, immunocompromised hosts, advanced age, long-term steroid use, and patients with liver or renal failure 1, 4
- In tropical regions, sickle cell disease, thalassemia, HIV infection, and tuberculosis significantly increase morbidity from hematogenous osteomyelitis 5