Model Answer
0 min readIntroduction
Acute osteomyelitis is an infection of the bone, typically caused by bacterial pathogens. It’s a relatively uncommon but serious condition, particularly in children, though it can occur at any age. The infection usually originates from hematogenous spread (bacteria traveling through the bloodstream) or direct inoculation (e.g., following trauma or surgery). Understanding the pathological changes and potential complications is vital for prompt diagnosis and effective management, preventing long-term morbidity. This answer will detail the sequential pathological changes and the resulting complications associated with acute osteomyelitis.
Pathological Changes in Acute Osteomyelitis
The pathological changes in acute osteomyelitis evolve through distinct stages:
1. Initial Inflammatory Phase (0-48 hours)
- Bacterial Invasion: Typically Staphylococcus aureus is the causative agent, though others like Streptococcus pyogenes, Escherichia coli (in neonates), and Salmonella can also be responsible.
- Inflammation: Bacteria trigger an intense inflammatory response characterized by vasodilation, increased vascular permeability, and neutrophil infiltration.
- Edema & Congestion: The bone marrow becomes congested with inflammatory cells and edema fluid, increasing intra-medullary pressure.
- Pain: This pressure causes significant pain, often exacerbated by movement.
2. Suppurative Phase (48-72 hours to 2 weeks)
- Pus Formation: Neutrophils die and release enzymes, leading to liquefactive necrosis and pus formation within the medullary cavity.
- Periosteal Reaction: The periosteum (outer covering of the bone) becomes inflamed and elevated, forming a subperiosteal abscess. This is a key radiographic finding.
- Cortical Destruction: The pus extends through Volkmann's canals, eroding the cortical bone.
- New Bone Formation (Involucrum): The periosteum attempts to isolate the infection by forming a shell of new bone around the infected area – the involucrum.
3. Sequestrum Formation (2 weeks onwards)
- Necrosis & Separation: Areas of bone that are completely deprived of blood supply undergo necrosis, forming a sequestrum – a segment of dead bone separated from the living bone.
- Cloaca Formation: The pus tracks through the cortical bone, creating a draining sinus tract (cloaca) that opens onto the skin surface.
- Chronic Inflammation: The infection becomes chronic, with persistent inflammation and pus discharge.
Complications of Acute Osteomyelitis
1. Local Complications
- Pathological Fracture: Weakening of the bone due to cortical destruction increases the risk of fracture.
- Chronic Osteomyelitis: Failure to eradicate the infection leads to chronic osteomyelitis, characterized by persistent pain, drainage, and recurrent exacerbations.
- Abscess Formation: Subperiosteal or soft tissue abscesses can develop, requiring drainage.
- Growth Disturbances (in children): Infection near the growth plate can lead to premature closure or angular deformities.
- Osteonecrosis: Prolonged vascular compromise can result in osteonecrosis (bone death).
2. Systemic Complications
- Sepsis: Bacteria can enter the bloodstream, causing sepsis – a life-threatening systemic inflammatory response.
- Septic Arthritis: The infection can spread to adjacent joints, causing septic arthritis.
- Endocarditis: In rare cases, bacteria can seed the heart valves, leading to endocarditis.
- Toxic Shock Syndrome: Certain strains of Staphylococcus aureus can produce toxins that cause toxic shock syndrome.
3. Complications based on location
| Location | Specific Complications |
|---|---|
| Metaphysis of long bones (common in children) | Growth disturbances, angular deformities |
| Vertebrae | Spinal instability, neurological deficits |
| Flat bones (e.g., pelvis) | Extensive abscess formation, chronic pain |
Conclusion
Acute osteomyelitis is a serious infection with a complex pathological course. Early diagnosis and appropriate antibiotic therapy are crucial to prevent progression to suppurative stages and subsequent complications like sequestrum formation and chronic osteomyelitis. Systemic complications, though less common, can be life-threatening. A multidisciplinary approach involving orthopedic surgeons, infectious disease specialists, and radiologists is essential for optimal patient management. Ongoing research focuses on improving diagnostic techniques and developing novel therapeutic strategies to minimize long-term morbidity.
Answer Length
This is a comprehensive model answer for learning purposes and may exceed the word limit. In the exam, always adhere to the prescribed word count.