Convert it into a beautiful and concise point wise 6 marks answer under the heading of PYOGENIC OSTEOMYELITIS reference from above images from HARSH MOHAN TEXTBOOK OF PATHOLOGY 2ND YEAR MBBS .
PYOGENIC OSTEOMYELITIS
Definition
- Pyogenic (suppurative) osteomyelitis is bacterial infection of bone, rarely caused by fungi.
Routes of Spread
- Haematogenous route - more common; affects metaphyseal region of long bones, especially in children.
- Direct extension / implantation - from contiguous infection or trauma; can affect any part of bone in adults or children.
Predisposing Factors
- Compound fractures, surgical procedures, prosthesis/implants
- Gangrene of limb in diabetics
- Debilitation and immunosuppression
Causative Organisms
- Staphylococcus aureus - implicated in the vast majority of cases
- Less frequently: Streptococci, E. coli, Pseudomonas, Klebsiella, anaerobes
- Mixed infections are common in post-traumatic osteomyelitis
- Transient bacteraemia may precede osteomyelitis; blood cultures may be positive
Clinical Features
- Painful and tender limb, fever, malaise, leucocytosis
- Radiologic examination confirms bony destruction
- Chronic cases: discharging sinus tract
- Pathological fracture in long bone or vertebra
Pathology - Sequence of Changes (Fig. 29.2)
| Step | Change |
|---|---|
| 1 | Infection begins in metaphyseal marrow cavity, occupied by pus; microscopy shows congestion, oedema, neutrophilic exudate |
| 2 | Raised tension in marrow spreads infection along marrow cavity → endosteum → Haversian & Volkmann canals → causes periostitis |
| 3 | Infection reaches subperiosteal space → subperiosteal abscess → may penetrate cortex → draining skin sinus tracts |
| 4 | Suppuration + impaired blood supply → erosion and infarction necrosis of cortex = sequestrum |
| 5 | New bone formation beneath periosteum forms encasing sheath around necrosed bone = involucrum (irregular surface with perforations for sinus tracts) |
| 6 | Long-continued neo-osteogenesis → dense sclerotic pattern = chronic sclerosing nonsuppurative osteomyelitis of Garré |
| 7 | Localised containment by fibrous/granulation tissue = Brodie abscess |
| 8 | In vertebral pyogenic osteomyelitis: infection begins at disc (discitis), spreads to vertebral bodies (Fig. 29.4A) |
Complications
- Septicaemia
- Acute bacterial arthritis
- Pathologic fractures
- Draining sinus in long-standing cases → development of squamous cell carcinoma
- Secondary systemic amyloidosis (AA type) - due to persistence and chronicity
- Vertebral osteomyelitis → vertebral collapse, paravertebral abscess, epidural abscess, cord compression and neurologic deficits
Basic pathologic changes at any stage: suppuration, ischaemic necrosis, healing by fibrosis and bony repair. (Ref: Harsh Mohan - Textbook of Pathology, Chapter 29 - Musculoskeletal System)
PYOGENIC OSTEOMYELITIS histopathology diagram
Histopathology diagram of Pyogenic Osteomyelitis for medical students (2nd year MBBS), labeled scientific illustration showing: necrotic bone (sequestrum) with empty lacunae, dense neutrophilic infiltrate and purulent exudate in marrow cavity, congested capillaries, periostitis with new bone formation (involucrum), subperiosteal abscess, Haversian canals with inflammatory cells, granulation tissue, and draining sinus tract. Clean medical textbook style diagram with clear labels and arrows, H&E stain appearance, educational pathology illustration
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