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Osteomyelitis, Emergency Medicine

Basics

Description

- Hematogenous OM: - Primarily in children, elderly, IV drug abuse (IVDA) patients - Seeding of bacteria to bone from remote site of infection via bloodstream - Children have acute OM and adults subacute or chronic. - Hematogenous OM of long bones rarely occurs in adults. - Most children with acute hematogenous OM have no preceding illness. - 1/3 have history of trauma to affected area. - Staphylococcus aureus is the most common cause of OM in all ages. - Neonates: S. aureus, Enterobacteriaceae, group A and B streptococci, and Escherichia coli - Children: S. aureus, group A streptococci, Haemophilus influenzae, Enterobacteriaceae - Salmonella: Common in sickle cell disease - Adults: S. aureus, Enterobacteriaceae, Pseudomonas, gram-negative rods, Staphylococcus epidermidis, gram-positive anaerobes, especially Peptostreptococcus - Illicit drug users: Candida, Pseudomonas, Serratia marcescens - Prolonged neutropenia: Candida, Aspergillus, Rhizopus, Blastomyces, coccidioidomycosis

- Hematogenous vertebral OM: - Uncommon - Most prevalent in adults >45 yr - Involves the disk and vertebra above and below - Often in the setting of long-term urinary catheter placement, IVDA, cancer, hemodialysis, or diabetes - IVDA: OM of pubic symphysis, sternoclavicular, and sacroiliac (SI) joints - Lumbar vertebrae most common, followed by thoracic, then cervical - Posterior extension leads to epidural/subdural abscess or meningitis. - Anterior extension may lead to paravertebral, retropharyngeal, mediastinal, subphrenic, retroperitoneal, or psoas abscess.

- Vascular insufficiency/diabetes: - Small bones of feet are common sites. - Infection resulting from minor trauma, infected nail beds, cellulitis, or skin ulceration - Polymicrobial, including anaerobes

- Chronic OM: - OM that persists or recurs - Distinguishing characteristic is necrotic bone (sequestrum) that must be debrided. - S. epidermidis, S. aureus, Pseudomonas aeruginosa, S. marcescens, and E. coli

- MRI: - Best modality to obtain detailed anatomy and extension of soft tissue and bone marrow involvement - Sensitivity and specificity of ¢ ¼90% - Reveals bone edema, cortical destruction, periosteal reaction, joint surface damage, and soft tissue involvement before x-rays - Effective in early detection (3 " 5 days from onset of infection) - Test of choice to identify vertebral OM and OM in diabetic foot ulcers - Occasional false-positive results in trauma, previous surgical procedures, or neuropathic joint disease - Negative study after 1 wk of symptoms rules out acute OM

- CT: - Modality of choice when MRI cannot be done - Reveals bone edema, cortical destruction, periosteal reaction, small foci of gas or foreign bodies, joint surface damage, and soft tissue involvement when plain films not helpful - Useful in OM of vertebrae, sternum, calcaneus, pelvic bones - Useful to surgeons in guiding debridement and biopsy

- Leukocyte scintigraphy: - Indium111-labeled WBCs - More specific but less sensitive than bone scan - Difficult to distinguish bone inflammation from soft tissue inflammation (i.e., cellulitis, tumors, inflammatory arthritis)

  • Osteomyelitis (OM): Infection of bone with ongoing inflammatory destruction
  • Usually bacterial, but fungal OM does occur
  • Could be acute or chronic

Etiology

  • Hematogenous OM:Primarily in children, elderly, IV drug abuse (IVDA) patientsSeeding of bacteria to bone from remote site of infection via bloodstreamChildren have acute OM and adults subacute or chronic.Hematogenous OM of long bones rarely occurs in adults.Most children with acute hematogenous OM have no preceding illness.1/3 have history of trauma to affected area.Staphylococcus aureus is the most common cause of OM in all ages.Neonates: S. aureus, Enterobacteriaceae, group A and B streptococci, and Escherichia coliChildren: S. aureus, group A streptococci, Haemophilus influenzae, EnterobacteriaceaeSalmonella: Common in sickle cell diseaseAdults: S. aureus, Enterobacteriaceae, Pseudomonas, gram-negative rods, Staphylococcus epidermidis, gram-positive anaerobes, especially PeptostreptococcusIllicit drug users: Candida, Pseudomonas, Serratia marcescensProlonged neutropenia: Candida, Aspergillus, Rhizopus, Blastomyces, coccidioidomycosis
  • Hematogenous vertebral OM:UncommonMost prevalent in adults >45 yrInvolves the disk and vertebra above and belowOften in the setting of long-term urinary catheter placement, IVDA, cancer, hemodialysis, or diabetesIVDA: OM of pubic symphysis, sternoclavicular, and sacroiliac (SI) jointsLumbar vertebrae most common, followed by thoracic, then cervicalPosterior extension leads to epidural/subdural abscess or meningitis.Anterior extension may lead to paravertebral, retropharyngeal, mediastinal, subphrenic, retroperitoneal, or psoas abscess.
  • Direct or contiguous OM:Organism(s) directly seeded in bone due to trauma, especially following open fractures:Spread from adjacent site of infection or from surgeryMore common in adults and adolescentsS. aureus, Enterobacteriaceae, PseudomonasNormal vascularity:S. aureus and S. epidermidis, gram-negative bacilli, and anaerobic organismsVascular insufficiency/diabetes:Small bones of feet are common sites.Infection resulting from minor trauma, infected nail beds, cellulitis, or skin ulcerationPolymicrobial, including anaerobesPuncture wound through tennis shoe: S. aureus, PseudomonasClavicular OM can occur as complication of subclavian vein catheterization.
  • Chronic OM:OM that persists or recursDistinguishing characteristic is necrotic bone (sequestrum) that must be debrided.S. epidermidis, S. aureus, Pseudomonas aeruginosa, S. marcescens, and E. coli

Diagnosis

Signs and Symptoms

Vary with duration of disease

History

  • Mainly nonspecific symptoms
  • Pain: Localized, deep, dull, and throbbing; occurs with and without movement
  • Fever and chills; may be absent in chronic OM
  • Malaise, nausea, vomiting
  • Reluctance to use extremity
  • Nonhealing ulcers despite proper therapy
  • Consider OM as a cause of fracture nonunion
  • Predisposing factors: DM, vasculopathy, IVDA, invasive procedures, trauma

Physical Exam

  • Tenderness to palpation, warmth, erythema, edema, decreased range of motion
  • Drainage of sinus tract
  • Deep ulcers and palpable bone (+ "probe to bone " test has very high positive predictive value)
  • If ulcer size >2 cm2 and >3 mm in depth, bone involvement is likely.

Essential Workup

  • CBC
  • ESR and C-reactive protein
  • Radiographs
  • Blood and wound cultures and sensitivities

Diagnosis Tests & Interpretation

Lab

  • CBC; WBC may be elevated but often normal
  • ESR; elevated in >90% of cases
  • C-reactive protein (usually elevated)
  • Blood cultures (positive in ¢ ¼50% of cases)

Imaging

  • Plays a central role in evaluation
  • Start with plain films; other tests often required
  • Radiographs:May be normal for the 1st 2 " 3 wk of symptomsEarliest finding is periosteal elevation, followed by cortical erosions, then new bone formation.40 " 50% of focal bone loss needed to detect lucency on radiograph; fewer than 1/3 of cases have diagnostic findings at 10 daysObtain CXR if TB suspected
  • MRI:Best modality to obtain detailed anatomy and extension of soft tissue and bone marrow involvementSensitivity and specificity of ¢ ¼90%Reveals bone edema, cortical destruction, periosteal reaction, joint surface damage, and soft tissue involvement before x-raysEffective in early detection (3 " 5 days from onset of infection)Test of choice to identify vertebral OM and OM in diabetic foot ulcersOccasional false-positive results in trauma, previous surgical procedures, or neuropathic joint diseaseNegative study after 1 wk of symptoms rules out acute OM
  • CT:Modality of choice when MRI cannot be doneReveals bone edema, cortical destruction, periosteal reaction, small foci of gas or foreign bodies, joint surface damage, and soft tissue involvement when plain films not helpfulUseful in OM of vertebrae, sternum, calcaneus, pelvic bonesUseful to surgeons in guiding debridement and biopsy
  • Bone scan:Technetium 99m methylene diphosphonate (99mTc-MDP)Measures increase in bone metabolic activity ¢ ¼95% sensitive but less specific than MRIBone scan abnormal after 2 " 3 days of symptomsFalse-positive may occur in trauma, surgery, chronic soft tissue infection, tumorHigh radiation burden, useful if suspect multifocal disease
  • Leukocyte scintigraphy:Indium111-labeled WBCsMore specific but less sensitive than bone scanDifficult to distinguish bone inflammation from soft tissue inflammation (i.e., cellulitis, tumors, inflammatory arthritis)
  • US:An emerging modality for OM especially in childrenPeriosteal elevation or thickening, fluid collections adjacent to bone often seenMay show findings of OM days prior to plain filmsUseful in guiding biopsy

Diagnostic Procedures/Surgery

  • Gold standard for diagnosis is bone biopsy with histology and tissue Gram stains, including culture and sensitivities.
  • Needle aspiration has lower sensitivity than open biopsy.
  • Culture of sinus or drainage from wound can be misleading; correlates well with S. aureus, but not as reliable for other organisms.
  • 70 " 85% of children have fever higher than 38.5 °C.
  • Neonates are commonly afebrile.
  • Only ¢ ¼1 in 3 of children will have leukocytosis.
  • Blood cultures positive in ¢ ¼50%
  • US

Differential Diagnosis

  • Cellulitis
  • Paronychia/felon
  • Bursitis, toxic synovitis, septic arthritis
  • Extremity fracture
  • Bone infarction in sickle cell patients
  • Acute leukemia, malignant bone tumors
  • Mechanical back pain
  • Spinal epidural abscess
  • Brucellosis, especially in SI joint
  • TB, more common in thoracic spine (Pott disease)

Treatment

Initial Stabilization/Therapy

Emergent stabilization if septic or if neurologic deficits from spine involvement

Ed Treatment/Procedures

  • Empiric antibiotic treatment in ED
  • Cultures should guide subsequent antibiotic regimen.
  • Antibiotics: Depend on patients age and organism (see Medications section)
  • Orthopedic and infectious disease consultation
  • Surgical intervention may be needed to optimize treatment (e.g., infected fracture or hardware, bone necrosis).
  • Parenteral antibiotic treatment for 4 " 6 wk

Medication

  • Newborn " 4 mo: Penicillinase-resistant synthetic penicillin (e.g., nafcillin: 37 mg/kg IV q6h) plus a 3rd-generation cephalosporin (e.g., ceftriaxone: 50 " 75 mg/kg/d IV); if suspect methicillin-resistant S. aureus (MRSA) then vancomycin (40 " 60 mg/kg IV q6h) plus a 3rd-generation cephalosporin. (Note: Doses are based on age >28 days)
  • Children (>4 mo): Penicillinase-resistant synthetic penicillin (e.g., nafcillin: 37 mg/kg IV q6h to max. 8 " 12 g/d). If suspect MRSA, then vancomycin (40 " 60 mg/kg IV q6h to max. 2 " 4 g/d). Add 3rd-generation cephalosporin if suspicion for gram-negative rods, or presence on Gram stain noted (e.g., ceftriaxone: 50 " 75 mg/kg IV per day to max. 2 " 4 g/d)
  • Adult: Penicillinase-resistant synthetic penicillin (e.g., nafcillin: 2 g IV q4h); if suspect MRSA, vancomycin (15 mg/kg IV q12h)
  • Gram-negative (including pseudomonas) chronic OM: Ciprofloxacin 750 mg PO BID or Levofloxacin 750 mg PO QD
  • Sickle cell anemia with OM: Ciprofloxacin 400 mg IV q12h, or levofloxacin 750 mg IV q24h (not in children); alternative: 3rd-generation cephalosporin
  • Post nail puncture through tennis shoe: Ciprofloxacin 750 mg PO BID or Levofloxacin 750 mg PO q24h; alternative: Ceftazidime 2 g IV q8h
  • Involving orthopedic prosthesis or hardware: Add rifampin (10 mg/kg/d PO/IV to max. of 600 mg/d) to regimen for S. aureus. Hardware removal generally required.
  • Post-traumatic OM: Vancomycin and ceftazidime
  • If vancomycin-resistant enterococcus present: Linezolid 600 mg IV q12h 6 wk

Children with hematogenous OM may undergo short-course IV antibiotics and then be changed to oral for additional 1 " 2 mo.

Follow-Up

Disposition

Admission Criteria

  • Patients with acute OM should be admitted.
  • Patients with chronic OM usually require admission for surgical procedures, debridement, and obtaining bone cultures and histology.

Discharge Criteria

Subacute or chronic OM patients may be considered for outpatient management if home IV antibiotics arranged, bone specimens obtained, and necrotic bone debrided.

  • Cases refractory to debridement and antibiotics benefit from hyperbaric oxygen as an adjunct to standard treatment.
  • ¢ ¼2/3 of these cases will demonstrate benefit.

Pearls and Pitfalls

  • WBC may be normal in many cases.
  • Radiographs may be normal in the 1st 2 " 3 wk of symptoms.
  • Wound cultures are low yield in guiding antibiotic therapy.

Additional Reading

  • Butalia S, Palda VA, Sargeant RJ, et al. Does this patient with diabetes have osteomyelitis of the lower extremity? JAMA. 2008;299(7):806 " 813.
  • Hatzenbuehler J, Pulling TJ. Diagnosis and management of osteomyelitis. Am Fam Physician. 2011;84(9):1027 " 1033.
  • Lalani T, Sexton D. Overview of osteomyelitis in adults. In: Rose BD, ed. UpToDate. Waltham, MA: UpToDate, 2013.
  • Weichert S, Sharland M, Clarke NM, et al. Acute haematogenous osteomyelitis in children: Is there any evidence for how long we should treat? Curr Opin Infect Dis. 2008;21:258 " 262.
  • Winters ME, Kluetz P, Zilberstein J. Back pain emergencies. Med Clin North Am. 2006;90:505 " 523.

Codes

ICD9

  • 730.00 Acute osteomyelitis, site unspecified
  • 730.10 Chronic osteomyelitis, site unspecified
  • 730.20 Unspecified osteomyelitis, site unspecified
  • 730.28 Unspecified osteomyelitis, other specified sites

ICD10

  • M86.9 Osteomyelitis, unspecified
  • M86.10 Other acute osteomyelitis, unspecified site
  • M86.60 Other chronic osteomyelitis, unspecified site
  • M86.50 Other chronic hematogenous osteomyelitis, unspecified site
  • M86.8X8 Other osteomyelitis, other site

SNOMED

  • 60168000 Osteomyelitis (disorder)
  • 409780002 Acute osteomyelitis (disorder)
  • 40970001 Chronic osteomyelitis (disorder)
  • 203179003 Acute hematogenous osteomyelitis (disorder)
  • 203241002 osteomyelitis of vertebra (disorder)
  • 61011009 Bacterial osteomyelitis