Bone and joint infection - Orthopedics

Question 1

Pathogenesis of Acute Haematogenous Osteomyelitis

Answer 1

б Trauma is usually a predisposing factor.
б The organism is usually Staphylococcus aureus.
б The infection usually starts in the metaphysis of a long bone:
» This area in children has a peculiar arrangement of the blood vessels (the terminal branches of the nutrient artery twist back in hairpin loops),
» leading to: relative vascular stasis & consequently lower oxygen tension favouring bacterial colonization.
б In infants:
» the anastomoses between metaphyseal and epiphyseal blood vessels are still present & opened.
» Infection can reach the epiphysis and causes simultaneous septic arthritis.

Question 2

Stages of the disease in Acute hematogenous osteomyelitis ?

Answer 2

1. Early:
   » the acute inflammatory reaction elicited leads to a rapid increase in the intraosseous pressure causing intense pain and obstruction of normal blood flow.
2. by the second day:
   » pus forms within the bone and forces its way along the bone canals to the surface, causing a subperiosteal abscess.
   » from the subperiosteal abscess, pus can spread along the shaft or burst into the surrounding soft tissues.
   » the increased intraosseous pressure, vascular stasis, and periosteal stripping increasingly compromise the blood supply together with the bacterial toxins and leucocytic enzymes.
   » All lead to tissue destruction and necrosis.
3. by the end of a week:
   » there is evidence of bone death and pieces of dead bone may separate (sequestra).
   » new bone starts formation (involucrum) enclosing the sequestrum and infected tissue.

Question 3

Treatment in Acute hematogenous osteomyelitis ?

Answer 3

Four pillars for infection treatment:
1. Antibiotic therapy:
» First empirical, then specific once culture and sensitivity are obtained.
» IV antibiotics should be continued till the clinical and laboratory markers improve and are followed by oral antibiotics for a further 2 or 3 weeks.
2. Surgical drainage:
» Signs of pus collection or if pus is aspirated.
» Clinical features do not improve within 36 hours or even earlier improve.
3. Splinting and rest of the affected part.
4. Supportive treatment for pain and dehydration.

Question 4

Complications in Acute hematogenous osteomyelitis ?

Answer 4

1. Epiphyseal damage and growth disturbances.
2. Spread causing suppurative arthritis or metastatic infection.
3. Pathological fracture.
4. Chronic osteomyelitis.

Question 5

What is the Kocher four criteria ?

Answer 5

1. serum WBC > 12,000 cells/μl
2. inability to bear weight
3. fever > 38.5° C
4. ESR > 40 mm/h.
   б Probability of septic arthritis may be as high as 99.6% when all four are present.