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Bone & Joints Infections
Osteomyelitis• Osteomyelitis is infection of the bone.
• Infections can reach a bone by traveling through the bloodstream, spreading from nearby tissue or begin in the bone itself after an injury.
• Common involved bones:
o In children: long bones of the legs and upper arm.
o In adults: the vertebrae.
o In Diabetics: osteomyelitis may complicate foot ulcers.
Diabetic septic foot
Symptoms and signs:
• Fever & chills.
• Pain, swelling, warmth and redness over the area of the infection.
• Sometimes osteomyelitis causes no signs and symptoms or signs and symptoms that are difficult to distinguish
Causes:
Microorganisms can enter the bone in a variety of ways:
• Via the bloodstream (Hematogenous: bacteria from distant infection deposit in a weak spot of the bone).
• From a nearby infection (internal source: joint infection or deep tissue infection).
• Direct contamination (external source: bone fracture or surgery).
Causative Agents of Osteomyelitis: S. aureus is the most common causative organism in all patients
Age group Most common organisms
Newborns ≤ 4 months Enterobacter species, and group A and B Streptococcus species
Children ≤ 4 yrsgroup A Streptococcus species, Haemophilus influenzae, and Enterobacter species
Children, adolescents (aged 4 y to adult)
S. aureus (80%), group A Streptococcus species, H. influenzae, and Enterobacter species
AdultS. aureus and occasionally Enterobacter or Streptococcus species
Sickle cell anemia Salmonella species. S. aureus is still most likely.
Vertebral osteomyelitis Staphylococci (50%), and Tuberculosis (50%).
Acute Osteomyelitis
Vertebral osteomyelitis can occur in adults secondary to a UTI or prostatitis. Or bone tuberculosis (Pott’s disease )
Candidemia from infected central venous catheters can lead to fungal osteomyelitis
Causative bacteria related to primary focus includes: gram positive cocci, gram negative bacilli, anaerobes or poly-microbial infection esp. in diabetics.
Bones are resistant to infection.
Risk factors include:
oInjury or orthopedic surgery: bone fracture, deep puncture wound, surgery, deep animal bites.
oCirculation disorders: Poorly controlled diabetes, arterial disease (smoking), sickle cell disease.
oIntravenous lines or catheters: Dialysis machines.
oImpaired immune system: Chemotherapy, organ transplant, corticosteroids. For unclear reasons people with HIV/AIDS don't seem to have an increased risk of osteomyelitis.
oDrugs users: Non sterile needles, unsterilized skin before injections.
Complications Bone death (osteonecrosis and sequestrum
formation).
Septic arthritis.
Impaired growth
Permanent deformities.
Skin cancer
Tests and diagnosis
oImaging tests
• X-rays
• Computerized tomography (CT) scan
• Magnetic resonance imaging (MRI)
oBlood culture: positive in 33% of cases
oBone aspiration or biopsy: if blood culture are negative.
Treatments:• Hospitalization is usually necessary
• Antibiotics: according to sensitivity results. Should be given intravenously and then orally for at least six weeks.
• Surgery: to drain the infected area, remove necrotic bone, remove prosthetics or any foreign object, restore blood flow to the bone or to amputate the limb.
Arthritis
• Inflammation of the joint space.
• Usually affects a single joint.
• Symptoms: Fever, pain, swelling, limitation of movement.
• Risk factors: age, diabetes, immunosuppression, IV drug use, catheters, prior joint damage, sexually transmitted diseases.
• Two types:o Septic (suppurative) arthritis: bacterial
infection.
o Non septic: gout, rheumatoid arthritis, viral
• Source of infection in septic arthritis:
o Internal:
o Hematogenous (the most common)
o Near infected bone.
o External: Trauma, arthroscopy or surgery.
Etiology:
Neisseria gonorrhoeae (gonococcal arthritis) is the leading cause in sexually active adults.
Non gonococcal: S. aureus is the most common causative bacteria and affects all age groups.
Other bacteria include: streptococci, gram negative bacilli and spirochetes (Lyme disease).
Prognosis & complications:
Gonococcal arthritis has an excellent outcome.
Nongonococcal arthritis can result in scarring with limitation of movement in 50% of cases.
Risk factors for complications include:
Age, prior rheumatoid arthritis, poly-articular joint involvement, hip or shoulder involvement, virulent pathogens and delayed initiation or response to therapy.
Diagnosis:
• Examination of synovial fluid: cloudy with high number of WBCs especially neutrophils. Gram stain.
• Culture: Blood, synovial fluid or skin lesions culture.
• PCR: synovial fluids or urine.
Treatment:
• Drainage of infected synovial fluid by aspiration (arthrocentesis) or surgically.
• Antimicrobial therapy: should be directed at suspected and susceptibility results. Given parentally then orally for 3- 4 weeks.
• Gonococcal & Enterobacteriaceae arthritis: Ceftriaxone Ciprofloxacin
• Nongonococcal arthritis: MSSA: nafcillin or cefazolin. MRSA: Vancomycin. Pesudomonas: piperacillin and Aminoglycoside. Animal bite : Ampicillin-Sulbactam. Lyme disease arthritis: Doxycycline