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