Osteomyelitis & Septic Arthritis Overview

Osteomyelitis & Septic Arthritis

• Osteomyelitis is an inflammation of bone caused by infection

• It can be localized or spread to bone marrow, cortex, periosteum, and surrounding soft tissue

• Classification is based on symptom duration, infection mechanism, and host response

  • Acute (<2 weeks)
    • Early acute
    • Late acute (4-5 days)
  • Subacute (2 weeks – 6 weeks)
  • Chronic (>6 weeks)

• Types of osteomyelitis

  • Exogenous
    • Direct (trauma, surgery)
    • Contiguous (from adjacent infection)
  • Hematogenous (bacteremia)

• Common organisms

  • Staphylococcus aureus (most common in all types)
  • Coagulase-negative staphylococci
  • Propionibacterium
  • Pseudomonas
  • Streptococci, anaerobic bacteria
  • Salmonella
  • Bartonella henslae
  • Pasturella or Eikenella
  • Fungal (e.g., Mycobacterium tuberculosis)
  • Group B streptococci
  • H. influenzae

• Risk factors

  • Recent trauma or surgery
  • Immunodeficiency
  • IV drug use
  • Poor vascular supply (e.g., diabetes, sickle cell)
  • Peripheral neuropathy

• Pathogenesis

  • Bacteria reach the metaphysis (long bones in children, vertebral bodies in adults)
  • Causes inflammatory response
  • Leads to necrosis (tissue death).
  • Abscess formation is a possible result

• Acute Hematogenous Osteomyelitis

  • Most common in children under 15
  • Slightly more common in males
  • Occurs in the metaphysis of long bones (Relative lack of phagocytosis activity in metaphyseal region)
  • Frequent trauma
  • Highly vascular tissues can aid the introduction of infectious materials

• Diaphyseal Osteomyelitis

  • Occurs in the diaphysis of long bones (mostly in children)
  • Result from direct trauma, particularly in children, where growth causes previously infected metaphyseal regions to shift to the diaphysis
  • Tubercular osteomyelitis is a possible cause

• Chronic Osteomyelitis

  • A progressive inflammatory process caused by infection
  • Tissue destruction and sequestrum formation is common
  • Infected foci within bone develop a sclerotic (hardened), relatively avascular, bone layer, surrounded by a thickened periosteum and scarred muscle and subcutaneous tissue

• Brodie's Abscess

  • Localized subacute osteomyelitis
  • Common in children ages 11 to 20
  • Intermittent deep boring pain, worse at night, relieved when at rest.
  • Contains pus or jelly-like granulation tissue surrounded by fibrous tissue.

• Septic Arthritis

  • Infection of the synovial membrane, often accompanied by purulent effusion in the joint capsule
  • Considered a medical emergency
  • Can lead to septic shock (potentially life-threatening)

• Clinical Picture (general)

  • History taking (duration of symptoms, prior trauma, treatment, and host factors)
    • Patient symptoms like pain, swelling, fever, and inability to use joint
    • Examination may reveal redness, tenderness, swelling and edema.

• Physical examination for septic arthritis, including vital signs

  • Decreased or absent range of motion
  • Signs of inflammation (swelling, warmth, tenderness, erythema)
  • Joint orientation to minimize pain (position of comfort)
    • Joint characteristics for certain regions like the hip, shoulder and knee

• Laboratory Findings (for both osteomyelitis and septic arthritis)

  • Elevated white blood cell count
  • Elevated erythrocyte sedimentation rate
  • Elevated C-reactive protein.
  • Aspiration of pus (often a definitive diagnosis)

• X-ray findings

  • Early stages may not reveal abnormality, so X-rays can be used to rule out trauma
  • Late-stage imaging may show cortical destruction (lytic lesion), periosteal reaction (involucrum), and sequestrum
  • Localized osteoporosis often occurs in early osteomyelitis

• Sonography

  • Can indirectly detect osteomyelitis via identifying periosseous soft tissue abnormalities.
  • Edematous swelling in the deep soft tissue may occur prior to any periosteal reaction

• Bone scan

  • Radioisotopic bone scanning valuable for bone infection localization within 48 hours

• CT and MRI

  • Useful for precise cortical bone and soft tissue imaging
    • May be used in the later phases of osteomyelitis and septic arthritis to display and define bony lesions

• Differential Diagnosis

  • Tuberculosis
  • Soft tissue infection
  • Ewing sarcoma
  • Osteoid osteoma
  • Eosinophilic granuloma
  • Trauma
  • Hemophilic bleed
  • Rheumatic fever
  • Juvenile rheumatoid arthritis
  • Sickle cell disease
  • Gaucher's disease
  • Gout
  • Pseudogout

• Treatment

  • General supportive treatment (nutrition, fluids)
  • Antibiotic therapy (usually intravenous)
  • Surgical treatment (drain abscess, debridement, sequestectomy)
  • Immobilization for a period of time (potentially a splint)

• Nade's principles of antibiotic therapy in osteomyelitis

  • Antibiotics are more effective if done before pus formation in tissue
  • Antibiotics cannot sterilize avascular tissue
  • Antibiotics can reduce pus reformation after removal
  • Pus removal restores periosteum (and subsequent blood flow)

• Nade's indications for surgery

  • Abscess formation
  • Severe acute osteomyelitis
  • Failure to respond to IV antibiotics for >48 hours

• Goal of surgery: surgical drainage and remove nonviable/necrotic tissue

• Complications

  • Chronic osteomyelitis
  • Septic arthritis
  • Growth disturbance
  • Septicemia
  • Deep vein thrombosis (DVT)
  • Pulmonary embolism

• Subacute Hematogenous Osteomyelitis

  • Insidious onset, lacking symptom severity
  • Diagnosis often delayed for >2 weeks
    • Pathogen identification limited (~60%)
  • Common organisms are S. aureus and Staphylococcus epidermidis
  • Requires biopsy and culture for diagnosis
    • Often involves large abscess formation

• Treatment of COM

  • Conservative approach (rest, antibiotics)
  • Surgical debridement - Bone curettage, with sealing large cavities with cancellous bone graft.
  • Antibiotic duration, often controversial

• Clinical features and laboratory data

• Detailed physical examination of the effected area

• Laboratory test data, including white blood cell counts, ESR, and CRP.

Septic Arthritis

• Infection of the synovial membrane of a joint

• Often caused by pathogens, and can cause severe inflammation

• Epidemiology

  • All ages, infants, and older adults susceptible

  • 50% of cases occur before 3 years old

• Etiology in Septic Arthritis

  • Staphylococcus aureus (most common)

• Microbiology

  • Other pathogens like gram-negative bacteria (e.g., Escherichia coli)
    • Pseudomonas aeruginosa

• Pathogenesis (details)

  • Bacteria reach the joint (hematogenous spread, contiguous spread, direct inoculation)
  • Joint inflammation, formation of pus (purulent effusion)
    • Damage to cartilage caused by bacterial enzymes
  • Can lead to a loss of joint space
  • Can cause joint dislocation

• Clinical Manifestations

  • Fever (toxic)
  • Severe pain in one joint
  • Severe swelling
  • Severe tenderness
  • Warmth
  • Limited range of motion
  • Signs of sepsis, possibly

• Physical examination

  • Decreased/absent range of motion
  • Swelling, warmth, tenderness, erythema in the involved joint

• Investigation

• Lab. Tests: elevated WBC, CRP, ESR

  • Aspiration and examination of synovial fluid (turbid, purulent, high leukocyte count, damaged white blood cells)

• Imaging

  • X-rays may reveal widening of joint space in early stages, joint space narrowing and irregularity in later stages
  • Ultrasonography, MRI are helpful for joint effusion and other joint anomalies

• Differential diagnosis

  • trauma
  • hemophilic bleed
  • Rheumatic fever
  • Juvenile rheumatoid arthritis
  • Sickle-cell disease
  • Gaucher's disease
  • Gout and Pseudogout

• Treatment

  • Aspiration and fluid analysis
  • General supportive care
  • Analgesics/IV fluids
  • Antibiotic therapy (specific antibiotics based on causative organism)
    • Needle aspiration followed by arthrotomy(open or arthroscopy) to examine the articulation.
    • Subsequent medical/surgical management based on causative factors

• Complications

  • Bone destruction and dislocation of joints (especially hip)
  • Cartilage destruction
  • Fibrosis/bony ankylosis (stiffening of joint)
  • Secondary osteoarthritis
  • Growth disturbance

This quiz covers essential aspects of osteomyelitis and septic arthritis, including causes, classifications, and common organisms involved. Understand the different types of osteomyelitis and the risk factors associated with these infections. Test your knowledge on this critical medical topic.