Bone Infections

Outline Acute Osteomyelitis

Subacute Osteomyelitis

Post-Operative Infections

Defining Osteomyelitis

What’s in a Name?

Osteomyelitis (Osteo- bone, Myelo- Marrow, and –itis -Inflammation)

Defining Osteomyelitis

What is it?

It is an infection of the of the bone or bone marrow which leads to a subsequent

Inflammatory process.

Defining Osteomyelitis

Where does it come from?

Micro-Organisms may reach bones via the Bloodstream or by Direct Invasion.

Defining Osteomyelitis

What affects it’s development?

Organism involved

Host Factors (i.e. Age, Immunity, Diseases)

Site of Involvement (i.e. local factors)

Defining Osteomyelitis

What affects it’s development?

Organism involved

Host Factors (i.e. Age, Immunity, Diseases)

Site of Involvement (i.e. local factors)

Acute OsteomyelitisTypes of Acute Osteomyelitis

I. Hematogenous Osteomyelitis

II. Direct Inoculation Osteomyelitis

Acute OsteomyelitisHematogenous Osteomyelitis:

Bacterial seeding from the blood.

Seen primarily in Children.

The most common site is the Metaphysis at the growing end of Long Bones in Children, and The Vertebrae and pelvic in Adults.

Acute OsteomyelitisDirect Inoculation

Osteomyelitis

Direct contact of the tissue and bacteria as a result of an Open Fracture or Trauma.

Tend to involve multiple organisms.

Acute OsteomyelitisCausative Organisms: Staphylococcus aureus (Mainly)

Streptoccous pyogens or pneumoniae. (Less)

H.Influenzae (Young Children)

Salmonella (Sickle-Cell)

Acute OsteomyelitisPathology: Inflammation.• Earliest Change• Increase interaosseous pressure leads to Pain.

Suppuration.• Pus @ Medulla =Volkmann canals=>Surface =>

Subperiosteal Abscess=> spread along the shaft=> re-enter the bone or burst into the soft tissue

• May extend to Epiphysis and Metaphysis in Neonates and Children. May extend to Interverteberal Discs in Adults.

Acute OsteomyelitisPathology: Necrosis.• Begin to see signs with in one week.

New-bone formation.• Bone thickens to form an involucrum enclosing the

infected tissue.• Perforation may occur converted acute into chronic

osteomyelitis.

Resolution.

Acute OsteomyelitisClinical Features: Pain Fever and Malaise Tenderness Restricted Joint Movement Redness, Edema, Warmth (Signify Pus) History preceding Skin Lesion or Sore

Throat.

Acute OsteomyelitisImaging: First 10 days X-Rays Show No Abnormality. By the end of the 2nd Week signs of

rarefaction of Metaphysis and New Bone Formation.

With Healing there is Sclerosis and thickening of Cortex.

MRI may help to distinguish between Bone and Soft-Tissue Infection.

Acute OsteomyelitisInvestigations: CBC

Leucocytosis C-reactive protein level usually is elevated

ESR usually is elevated

Investigations

1. Lab studies

2. Radiological studies

Lab studies CBC: leucocytosis

The C-reactive protein level usually is elevated (nonspecific but more useful than ESR).

ESR usually is elevated (90%) nonspecific.

Aspiration of the pus from the subperiosteal abscess and culture, and test sensitivity for antibiotics

Blood culture results are positive in only 50% of patients with hematogenous osteomyelitis.

Radiological studiesX-Ray:

First sign is soft-tissue edema at 3-5 days after infection.

Bony changes are not evident for 14-21 days: 1. early radiographic signs of rarefraction (thining of bony tissue

sufficient to cause decreased density of bone) of the metaphysis and periosteal new bone formation

2. increasing ragged if treatment is delayed3. sclerosis and thickening of the bone at healing

Approximately 40-50% focal bone loss is necessary to cause detectable lucency on plain films.

Plain-film radiograph showing osteomyelitis of the second metacarpal (arrow). Periosteal elevation, cortical disruption and medullary involvement are present.

The above X-ray of the right ankle of a 10-year-old boy shows lucency in the tibial metaphysis secondary to acute hematogenous osteomyelitis (AHO).

The above X-ray of the left ankle of a 10-year-old boy shows lucency in the tibial metaphysis secondary to acute hematogenous osteomyelitis (AHO).

Here is an X-ray of an AHO lesion extending into the growth plate.

Radiological studies MRI :

Early detection and surgical localization of osteomyelitis.

Sensitivity ranges from 90-100%. Radionuclide bone scanning :

A 3-phase bone scan with technetium 99m is probably the initial imaging modality of choice

Show increase activity but it is a non specific sign of inflamation.

This MRI sagittal section shows the same AHO lesions with the right lesion extending into the growth plate.

Bone scans, both anterior (A) and lateral (B), showing the accumulation of radioactive tracer at the right ankle (arrow). This focal accumulation is characteristic of osteomyelitis.

Radiological studiesCT scan (spinal vertebral lesions, complex

anatomy: pelvis, sternum, and calcaneus)Ultrasound

In children with acute osteomyelitis. May demonstrate changes as early as 1-2 days after

onset of symptoms. Abnormalities include soft tissue abscess or fluid

collection and periosteal elevation. Ultrasonography allows for ultrasound-guided

aspiration. It does not allow for evaluation of bone cortex

DiagnosisDiagnosis requires 2 of the 4 following criteria:

◦ Localized classic physical findings of bony tenderness, with overlying soft-tissue erythema or edema.

◦ Purulent material on aspiration of affected bone. ◦ Positive findings of bone tissue or blood culture. ◦ Positive radiological imaging study.

TreatmentPrinciples of treatment:

1. Analgesia an general supportive measures.

2. Rest of the affected part

3. Antibiotic treatment.

4. Surgical eradication of pus and necrotic tissue(debridement).

TreatmentAntibiotic treatment:

Start with IV antibiotics for 1-2 weeks then oral for 3-6 weeks.

Take cultures to detect the organism and its sensitivity pattern.

Start empirical treatment before the results came back, then modify it according to the results.

TreatmentAntibiotic choices:

Older children and adults (staph infection): fluloxacillin and fusidic acid.MRSA: Vancomycin

Children younger than 4 year-old or those with gram negative organisms: 3rd generation cephalosporins.

Heroin addicts and immuno-compromised patients: more specific antibiotics.

Cont… Sickle cell anemia and osteomyelitis: fluoroquinolone antibiotic

(not in children). A 3rd cephalosporin (eg, ceftriaxone) is an alternative choice.

Nail puncture occurs through an athletic shoe (S aureus and Pseudomonas aeruginosa): ceftazidime or cefepime. Ciprofloxacin is an alternative treatment.

Trauma (S aureus, coliform bacilli, and Pseudomonas aeruginosa): nafcillin and ciprofloxacin. Alternatives include vancomycin and a 3rd cephalosporin with antipseudomonal activity.

Treatment # Drainage:

Subperiosteal abscessPyrexia and local tenderness more than 24 hour

after adequate antibiotic treatment.

# Removal of prosthetic implants:If they become unstable after a trauma.Or intractable infection following joint replacement.

# Severe cases may lead to the loss of a limb.

Prevention Improve immunity.

Post-traumatic infection (regular wound dressing for established infection):

1. Debridement of open fractures.2. Stabilization of fractures.3. Antibiotics.4. Closure of exposed bone surfaces.

Postoperative infection:

1. Cleanest possible surgical environment.2. Careful haemostasis.3. Suction drainage.4. Prophylactic antibiotics in high risk surgeries.

Subacute Osteomyelitis Results from a less virulent Microorganism,

or a patient with an elevated resistance. Occurs Mostly at the Distal Femur or

Proximal Tibia On X-Ray we See Brodie’s Abcess:

Small and Oval in shape It is surrounded by sclerotic boneMay be mistaken for Ostieoid Osteoma

Subacute Osteomyelitis An image depicting subacute osteomyelitis

Post Operative Infections Prophylaxis is KEY in prevention.

Treated According to Infection

Post Operative Infections Not Uncommon, about a 5% incidence.

Predisposed by:1. Debility2. Chronic disease3. Previous Infection 4. Tight Dressing5. Corticosteroid Treatment6. Long Surgery7. Hematoma8. Foreign Material Implants