Updated: 11/6/2018

Osteomyelitis - Adult

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Introduction
  • Overview
    • Infection of bone characterized by progressive inflammatory destruction and apposition of new bone
      • treatment is often a combination of culture-directed antibiotics and surgical debridement of nonviable tissue
  • Epidemiology
    • incidence
      • the exact incidence is unknown
    • location
      • spine and ribs in dialysis patients
      • medial or lateral clavicle in IV drug abusers
      • foot and decubitus ulcers in diabetics
    • risk factors
      • recent trauma or surgery
      • immunocompromised patients
      • illicit IV drug use
      • poor vascular supply
      • systemic conditions such as diabetes and sickle cell
      • peripheral neuropathy
  • Pathophysiology
    • mechanism of spread
      • hematogenous
        • originated or transported by blood
        • most common etiology in children
        • vertebrae are the most common hematogenous site in adults
        • S. aureus is the most common organism
      • contiguous-spread
        • associated with previous surgery, trauma, wounds, or poor vascularity
        • can be bacterial (most common), mycobacterial, or fungal in nature
      • direct-inoculation
        • penetrating injuries
        • open fractures
        • surgical contamination
    • pathobiology
      • biofilm formation
        • planktonic bacteria attach to an inert substrate and undergo apoptosis to create a matrix for biofilm
        • biofilm is then made of an extracellular polymeric substance or exopolysaccharide
        • antibiotics are less effective due to difficulty penetrating the biofilm and bacteria lowering their metabolic rate
    • organism (see table below)
      • organism varies by age of the patient
      • S. aureus is most common in adults
  • Associated conditions
    • orthopaedic manifestations
      • septic arthritis
      • abscess
    • medical conditions
      • immunosuppression
      • dialysis
      • IV drug use
      • diabetes
      • poor nutrition
      • vascular disease
  • Prognosis
    • despite surgical debridement and long-term antibiotics, recurrence rate of chronic osteomyelitis in adults is 30%
    • poor prognosis in patients with major nutritional or systemic disorders
 
Osteomyelitis Organism Table
Age group Most common organisms
Newborns 
(younger than 4 mo)
S. aureusEnterobacter species, and group A and B Streptococcus species
Children 
(aged 4 mo to 4 y)
S. aureus, group A Streptococcus species, Kingella kingae, and Enterobacter species
Children, adolescents 
(aged 4 y to adult)
S. aureus (80%), group A Streptococcus species, H. influenzae, and Enterobacter species
Adult S. aureus and occasionally Enterobacter or Streptococcus species


Unusual Osteomyelitis Organism Table
Organism Patient characteristic
Salmonella Sickle cell anemia patients (S. aureus is still most common)
Pseudomonas IV drug use with AC or SC joint infection or puncture wound through rubber soled shoes
Bartonella HIV/AIDS patient following cat scratch or bite
Fungal osteomyelitis Immunosuppressed, long-term IV medications, or parentarel nutrition
Tuberculosis Manifestations include Potts disease
 
Classification
  • Timing classification
    • acute
      • within 2 weeks
    • subacute
      • within one to several months
    • chronic
      • after several months
  • Cierny-Mader classification
Cierny-Mader Classification of Osteomyelitis 
(describes anatomic involvement, host, treatment, prognosis)
 Anatomic Location
Stage I Medullary
Stage 2 Superficial
Stage 3 Localized
Stage 4 Diffuse
Host Type
Type A Normal  
Type BL Locally compromised  
Type BS
Systemically compromised
 
Type C Treatment is worse to the patient than infection  
 
Presentation
  • History
    • duration
    • prior treatments
    • characterize host
      • immunocompromised
  • Symptoms
    • pain
    • fever
      • more common in acute osteomyelitis
  • Physical exam
    • vital signs
      • fever, tachycardia, and hypotension suggest sepsis
    • inspection
      • erythema, tenderness, and edema are commonly seen
      • draining sinus tract  
        • more common in chronic osteomyelitis
        • if able to probe bone through sinus chronic osteomyelitis is present 
    • motion
      • limp and/or pain inhibition with weight-bearing or motion may be present
      • assess the joints above and below the area of concern
    • neurovascular
      • assessment of vascular insufficiency locally or systemically
Imaging
  • Radiographs
    • recommended views
      • orthogonal plain radiographs of the affected extremity
    • findings
      • acute 
        • imaging findings lag behind by 2 weeks
        • bone loss must be 50% before evident on plain films
      • chronic
        •  bone lucency, sclerotic rim, osteopenia periosteal reaction, and lysis around hardware
        • sequestrum: devitalized bone that serves as a nidus for infection 
        • involucrum: formation of new bone around an area of bony necrosis 
    • sensitivity and specificity is variable
  • CT
    • indications
      • assist in diagnosis and surgical planning by identifying necrotic bone
    • sensitivity and specificity may be affected by hardware artifact and scatter
  • MRI
    • indications
      • assists in the diagnosis and surgical planning
      • best test for diagnosing early osteomyelitis and localizing infection
    • views
      • T2 sequences will show bone and soft tissue edema
    • findings
      •  penumbra sign 
        • T1 - dark central abscess with bright internal wall and dark external sclerotic rim 
    • sensitivity and specificity
      • if negative rules out osteomyelitis
      • if positive may overestimate the extent of osteomyelitis
  • Nuclear medicine
    • technetium bone scan
      • indications
        • when radiographs are normal and MRI is not an option
      • sensitivity and specificity
        • highly sensitive but not specific
        • if negative rules out osteomyelitis
    • gallium scan
      • indications
        • diabetic foot or if MRI is not an option
      • sensitivity and specificity
        • cellulitis may cause false positive
        • if negative rules out osteomyelitis 
Studies
  • Laboratory analysis
    • leukocyte count (WBC)
      • only elevated in 1/3 of acute osteomyelitis
    • erythrocyte sedimentation rate (ESR)
      • usually elevated in both acute and chronic osteomyelitis (90%)
        • a decrease in ESR after treatment is a favorable prognostic indicator
    • C-reactive protein
      • most sensitive test with elevation in 97% of cases
        • decreases faster than ESR in successfully treated patients 
    • blood cultures
      • often negative, but may be used to guide therapy for hematogenous osteomyelitis
  • Microbiology
    • sinus tract cultures
      • not reliable for guiding antibiotic therapy
    • culture of bone
      • gold-standard for guiding antibiotic therapy
  • Histology
    • acute osteomyelitis 
      • live osteocytes with numerous acute inflammatory cells (neutrophils)
    • chronic osteomyelitis 
      • no nuclei in osteocytes with fibrosis of marrow and chronic inflammatory cells (lymphocytes) 
Differential
  • Key differential
    • Benign tumor
      • biopsy all infection, cultures all tumors
    • Malignant tumor
      • biopsy all infection, cultures all tumors
    • healing fracture
Treatment
  • Goals
    • success in the treatment is dependent on various factors 
      • patient factors
        • immunocompetence of patient
        • nutritional status
      • injury factors
        • the severity of the injury as demonstrated by segmental bone loss
      • infection location
        • metaphyseal infections heal better than mid-diaphyseal infections
      • other factors affecting prognosis and treatment include:
        • residual foreign materials and/or ischemic and necrotic tissues
        • inappropriate antibiotic coverage
        • lack of patient cooperation or desire
  • Nonoperative Treatment
    • suppressive antibiotics
      • indications
        • when operative intervention is not feasible 
    • hyperbaric oxygen therapy 
      • indications
        • can be used as adjunct in refractory osteomyelitis
  • Operative treatment
    • irrigation and debridement followed by organism specific antibiotics
      • indications
        • acute osteomyelitis that fails to improve on IV antibiotics
        • subacute osteomyelitis
        • abscess formation
        • chronic osteomyelitis
          • draining sinus
    • amputation
      • indications
        • chronic infection with pervasive wound or bone damage that is unable to be salvaged
Surgical Techniques
  • Antibiotic therapy
    • technique
      • antibiotics should be tailored to a specific organism, preferably after a bone biopsy is obtained
      • chronic suppressive antibiotics may be useful in patients who are immunocompromised or in whom surgery is not feasible
        • high rates of recurrence if suppressive antibiotics are discontinued
  • Irrigation & Debridement
    • soft tissue
      • all devitalized and necrotic tissue should be removed
      • extensive debridement is essential to eradicate the infection
    • bone work
      • sequestrum must be eliminated from the body, or infection is likely to recur
      • debride bone until punctate bleeding is seen - "paprika sign"  
    • hardware removal
      • any non-essential hardware should be removed
    • dead space management
      • goal is to replace dead bone and scar tissue with vascularized tissue
      • options include
        • vascularized bone grafts
        • local tissue flaps or free flaps
        • antibiotic-impregnated acrylic beads (PMMA)
        • vacuum-assisted closure
          • improve wound healing and dead space closure in multiple ways 
            • remove interstitial fluids
            • eliminate superficial purulence or slime
            • allow arterioles to dilate, which allows granulation tissue to proliferate
            • decrease in capillary afterload to promote inflow of blood
            • mechanical force on wound edges draws them in
    • instrumentation
      • bony stability is required for successful eradication of infection
      • external fixation preferred to internal fixation
      • surgical fixation techniques 
      •  
        • Ilizarov technique
        • intramedullary nail with or without external fixation
        • Masquelet technique
        • in situ reconstruction
      • mechanism is thought to be related to improved angiogenesis
    • outcomes
      • often requires staged approach with multiple debridements and delayed soft tissue coverage 
      • when combined with postoperative antibiotics tailored to a specific organism, treatment is often successful
  • Amputation
    • technique
      • amputation at the level that will eradicate infected tissue to healing tissue with capacity to heal
Complications
  • Persistence or extension of infection
  • Amputation
  • Sepsis
  • Malignant transformation (Marjolin's ulcer) 
    • incidence
      • 1% in chronic osteomyelitis
      • most commonly squamous cell carcinoma  
    • risk factors 
      • chronic draining sinus
    • treatment
      • wide surgical resection

 

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Questions (12)
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(OBQ13.63) A 34-year-old man is involved in a motor vehicle accident and sustains an open tibia fracture and is treated with intramedullary nailing. For the next 4 years, he continues to have pain and persistent discharge from a sinus over his shin. He ambulates with crutches and refrains from putting weight on the extremity. The clinical appearance and radiographs are seen in Figures A and B. Wound culture reveals methicillin-resistant Staphylococcus aureus (MRSA). What is the next step in treatment? Review Topic

QID: 4698
FIGURES:
1

Retention of tibial nail, lifelong intravenous antibiotic suppression

0%

(7/2784)

2

Debridement and lavage, exchange nailing using a larger diameter nail, intravenous antibiotics for 6 weeks.

5%

(133/2784)

3

Debridement and lavage, excision of sinus tract, implant removal, intravenous antibiotics for 6 weeks.

11%

(303/2784)

4

Debridement and lavage, addition of ring fixator, intravenous antibiotics for 6 weeks.

4%

(112/2784)

5

Debridement and lavage, excision of sinus tract, exchange nailing using antibiotic impregnated-cement nail, intravenous antibiotics for 6 weeks.

79%

(2206/2784)

ML 2

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PREFERRED RESPONSE 5
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(OBQ05.274) A 45-year-old homeless hemophiliac male presents with chronic tibial osteomyelitis. Which of the following factors has been shown to predict a better prognosis? Review Topic

QID: 1160
1

Polymicrobial infection

7%

(31/441)

2

Use of external fixation

17%

(77/441)

3

Infection with Methicillin-resistant Staphylococcus aureus

3%

(14/441)

4

Metaphyseal infection

71%

(315/441)

5

Contralateral lower extremity amputation

1%

(3/441)

ML 2

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PREFERRED RESPONSE 4

(OBQ12.153) A 33-year-old motorcyclist is involved in a motor vehicle accident and sustains a Grade III open fracture of his tibia that is treated surgically. Over the next 35 years, he undergoes multiple debridements for a persistently draining wound. Over the last year, he has noticed "tissue growing out of the wound" and a malodorous smell. A photograph of the wound and a recent radiograph are seen in Figure A. A biopsy of the mass is shown in Figures B, and C. What is the most likely pathologic process? Review Topic

QID: 4513
FIGURES:
1

Infection

3%

(175/5305)

2

Squamous cell carcinoma

89%

(4734/5305)

3

Basal cell carcinoma

2%

(100/5305)

4

Melanoma

0%

(15/5305)

5

Soft-tissue sarcoma

5%

(259/5305)

ML 1

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PREFERRED RESPONSE 2

(OBQ07.239) A 34-year-old man sustained a gunshot wound to the knee 18 months ago and was treated with bullet removal and a 10 day course of oral antibiotics. He now complains of 12 months duration of pain in the thigh and recent ulceration and drainage of the skin near the site of his gunshot wound. Physical exam is notable for a draining sinus tract, erythema and tenderness of the mid-thigh. He is afebrile. An MRI image of this patient is shown in Figure A. Which of the following is the most appropriate management? Review Topic

QID: 900
FIGURES:
1

Two week course of oral cephalosporin

0%

(3/2401)

2

Core needle bone culture followed by intravenous antibiotics

6%

(137/2401)

3

Surgical debridement, culture, and intravenous antibiotics

91%

(2180/2401)

4

Core needle biopsy, chest CT scan, and bone scan

3%

(64/2401)

5

Neoadjuvant chemotherapy and wide resection followed by adjuvant chemotherapy

0%

(9/2401)

ML 1

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PREFERRED RESPONSE 3
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