1. Osteomyelitis:
Osteomyelitis is the inflammation of bone and marrow due to infectious agents or other causes.
Osteomyelitis can result from:
1-Bloodborne infection;
Hematogenous dissemination.
2-Direct introduction of microbe from external sources:
(Post-traumatic or surgical contamination).
3-Contiguous sources:
Soft tissue or joints infection;
A special type occurs in foot bones of diabetic patients.

2. Hematogenous Osteomyelitis:
-It occurs mainly in the growing ends or metaphysis of
long bones; where rapid growth depends on rich vascular
supply.
-It is seen mainly in childhood and adolescence.
-It could occur in infancy.
-Pathophysiology:
1-The anatomy of the vascular supply of metaphysis
predisposes the area to infection.
2-The capillaries from nutrient arteries of bone make
sharp loops close to growth plate.

3. 3-Capillaries expand to large sinusoidal vessels that
connect venous network of medullary cavity of bone.
4-This slows the
blood flow;
formation of
micro-clots of blood.
5-Adherence of bacteria (bacteremia origin) to blood clots;
inflammation, creation of acidic pH, bacterial
proliferation, Bone necrosis and destruction. n

4. A-Osteomyelitis in Infants:(Hematogenous origin):
-It begins in metaphysis of long bone.
-The bones of an infant are soft and the periosteum is
loosely attached to the cortex.
-Due to infection of medullary
bone; rupture through
thin cortex in subperiosteal
space; Subperiosteal abscess.
-Periosteal cells transform into
osteoblasts; new bone
formation; Involucrum.

5. Figure and Radiology: Involucrum:
Formation of new bone due to osteomyelitis. N

6. B-Osteomyelitis in Children: -Age 1 year to puberty.
-Occurs in long bone and contained within metaphysis.
-In Bones of children:
1-Thicker cortex.
2-Periosteum adheres more
tightly to cortex.
-Infection persist within bone; increased pressure causes
large clots formation in arterioles and capillaries;
necrosis of bone (dead bone, Sequestrum formation).
-Loss of immunity and blood supply; bone calcification.

7. C-Osteomyelitis in Adults : Vertebral osteomyelitis:
-Shown in the bones that make up the spine
(Vertebral bodies).
-It could be associated with:
1-Degenerative bony changes with age.
2-Vascular proliferation in disk space.
-Infection begins in the disk space
(Intervertebral)and then spreads to contiguous vertebrae.
-Abnormal disk space with erosion.
-Staphylococcus aureus is the most common causative
agent (50% of cases). n

8. -Other causative agents of vertebral osteomyelitis:
Enteric Gram’s negative bacilli, Streptococcus viridans,
and Enterococci.
-In case of pulmonary tuberculosis:
Mycobacterium tuberculosis is the most common cause
(50% of cases).
-Drainage of infected pelvic organs through pelvic veins
into the complex venous networks surrounding spinal
column (Batson plexus) causes vertebral osteomyelitis.
-Primary infection of gallbladder, urinary tract, Prostatitis. n

9. Osteomyelitis secondary to contiguous foci of infection:
-Bone infection caused by direct microbial entry from
external source.
-Risk factors: Recent injury or orthopedic surgery:
A severe bone fracture or a deep puncture wound.
Surgery (Prosthetic fixation device).
Deep animal bites.
-Loss of immunity and vascular supply in traumatized bone
after surgery.
-Staphylococcus aureus is most common ;postoperative
infection.
-Staphylococci forms Biofilms on foreign device surface.

10. -Contamination of wound by dirt or water leads to:
Gram’s negative bacilli infection, mainly Pseudomonas
aeruginosa.
-Circulation disorders are associated with this type
infection:
When blood vessels are damaged or blocked
What begins as a small cut can progress to a deep ulcer that may expose deep tissue and bone to infection
Diseases that impair blood circulation include:
Poorly controlled diabetes
Peripheral arterial disease
;often related to smoking
Sickle cell disease n

11. Osteomyelitis in persons with diabetes:
-Skin and soft tissue ulceration of foot may go unnoticed
due to sensory neuropathy and impaired immunity.
-Poly-microbial etiology:
Staphylococcus aureus,
Streptococci, Enterococci,
G-ve bacilli, Anaerobic bacteria.
-Difficult to be treated; poor vascular supply to necrotic bone:
1-Surgical intervention.
2-Intravenous antibiotic therapy.

12. Causes of Osteomyelitis:N
Age group
Most common organisms
Newborns; Infancy: (younger than 4 months)
Staphylococcus aureus, Enterobacter species, and group A and B Streptococcus species
Children (aged 4 months to 4 years)
Staphylococcus aureus, group A Streptococcus species, Haemophilus influenzae, and Enterobacter species
Children, adolescents (aged 4 y to puberty)
Staphylococcus aureus (80%), group A Streptococcus species, H. influenzae, and Enterobacter species
Adult
S. aureus and occasionally Enterobacter or Streptococcus species
Sickle cell anemia patients
Salmonella species are more common in patients with sickle cell disease than in normal patients. However, S. aureus is still most likely to occur.
Vertebral osteomyelitis
Staphylococci (50%), and Tuberculosis (50%).

13. Complications of Osteomyelitis:
Osteomyelitis complications may include:
Bone death (osteonecrosis)
Septic arthritis.
Impaired growth and bone deformity.
Malignancy.

14. Diagnosis and Treatment:
-Pus aspiration or bone sampling.
-Blood culture.
-Both are diagnostic for 90% of cases.
-Elevated C-reactive protein Elevated ESR
-Computerized tomography (CT) scan -Radiology (X-Rays)
-Treatment:
1-Methicillin resistant Staphylococci; Vancomycin or
Clindamycin in addition to Beta-Lactam (Amoxicillin).
2-Peripherally inserted central catheter.
3-Long-term therapy: 4-6 weeks: to penetrate bone.

15. Arthritis: -It is the inflammation of joint space due to invasive
microbes or other causes.
-Classification: Septic and Aseptic arthritis.
-Septic (infectious) arthritis:
1-Generally affects a single joint and
result in suppurative inflammation.
2-Hematogenous seeding of joint is most common.
3-Pain, swelling, limitation of movement are the common
symptoms.

16. Etiology of Septic Arthritis:
-Gonococcal infection most common cause in sexually
active young adults (caused by Neisseria gonorrheae).
-Non-Gonococcal arthritis occurs in older adults.
-Non-Gonococcal arthritis is associated with:
1-Staphylococcus aureus infection(most common; 40-50%).
2-Streptococci and Aerobic Gram negative bacilli.
3-Borrelia species (Lyme disease in endemic area).

17. -Septic Arthritis could be established due to:
Pathogenesis:
-Synovial A cells.
-Cytokines:TNF,IL-8:
Neutrophils Chemotaxis.
-Proteoglycan &
collagen destruction.
-Pressure; cartilage destruction
and necrosis.
-Septic Arthritis could be established due to:
1-Direct Trauma Contiguous soft tissue infection.
3-Medical procedures:
Arthroscopy or Prosthetic joint fixation device. n

18. Diagnosis of Septic (Infectious) Arthritis:
Risk factors predisposing for Septic Arthritis:
Age, Diabetes, Immunosuppression, IV drug use, Catheters, Prior joint damage ,and sexually transmitted diseases.
Diagnosis of Septic (Infectious) Arthritis:
-History/examination to exclude systemic illness.
-Clinical specimens:
1-Synovial fluid Blood Urine or discharge.
-In Microbiology:
1-Culture: For bacteria on blood and chocolate agar.
2-Microscopy: Gram’s stain of smear prepared from synovial
fluid.
3-PCR: to detect microbial DNA in specimens. n

19. Treatment & Management:
-Arthrocentesis with drainage of infected synovial fluid
-Repeated therapeutic arthrocentesis often needed.
arthroscopic or surgical drainage/debridement
-Antimicrobial therapy should be directed and suspected
according to susceptibility results:
Gonococcal arthritis: IV Ceftriaxone ( or Ciprofloxacin or Ofloxacin) then switch to oral Quinolone or Cefixime for 7-10 days. n

20. Nongonococcal infectious (septic) arthritis:
MSSA: Nafcillin or Cefazolin.
MRSA: Vancomycin
Streptococci: Penicillin or Ceftriaxone or Cefazolin
Enterobacteriaceae: Ceftriaxone or Fluroquinolone
Pesudomonas: Piperacillin and Aminoglycoside.
Lyme disease arthritis: Doxycycline for 1 month
Risk Factors predisposing to Arthritis:
Age, prior rheumatoid arthritis, poly-articular joint involvement, hip or shoulder involvement, virulent pathogens and delayed initiation or response to therapy. n