Osteomyelitis

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Contents 1 More Specific Terms 2 Introduction 3 Classification 4 Etiology 5 Pathology 6 Clinical-manifestations 7 Laboratory 8 Radiology 9 Management 10 More General Terms 11 References

More Specific Terms

• petrositis; petrous apicitis; Gradenigo's syndrome
• sacroiliac osteomyelitis

Introduction

• Infection of the bone.

Classification

• acute hematogenous osteomyelitis

• infection of intervertebral disc space & 2 adjacent vertebrae

• contiguous focus osteomyelitis

• patients > 50 years of age with diabetes mellitus or peripheral vascular disease
• secondary spread of infection from adjacent soft tissue or joints, or due to surgery or trauma
• rheumatoid arthritis

• sternal osteomyelitis

• wound healing complications
• unstable sternum
• fever after thoracic surgery

• clavicular osteomyelitis

• pain, cellulitis, or drainage in the sternoclavicular area after subclavian vein catheterization

• sternoclavicular joint osteomyelitis

• pain & fever in an injection drug user [4]

Etiology

• Staphylococcus aureus & coagulase-negative staphylococci are the most common pathogens
• gram-negative rods (Pseudomonas, Serratia, Salmonella E. coli)

• Pseudomonas aeruginosa is a common cause of osteomyelitis in a patient who has stepped on a nail while wearing a tennis shoe

• anaerobes
• polymicrobial infection may occur in the setting of diabetic foot ulcer & other forms of contiguous focus osteomyelitis
• less frequent causes

• tuberculosis, brucellosis, histoplasmosis, coccidioidomycosis, blastomycosis

• risk factors for hematogenous osteomyelitis

• hemodialysis with tunneled intravascular catheters
• long-term intravascular catheters
• high-grade bacteremia
• endocarditis
• sickle cell disease

Pathology

• microorganisms enter the bone by hematogenous spread or directly via a wound or from an adjacent infection
• the metaphyses of long bones ( tibia, femur, humerus) & vertebrae are the most frequently involved sites in children
• in adults, the vertebrae, sternum, clavicle, sacrum, ilium & metaphyses of long bones ( tibia, femur, humerus) are most commonly affected
• in older adults, the vertebrae are most commonly affected
• bones of the foot in patients with diabetic foot ulcers
• infection may traverse cortical bone to involve the marrow

Clinical-manifestations

• fever
• 50% of patients present with vague pain of the affected limb or back
• in vertebral osteomyelitis, pain is secondary to nerve root irritation
• pain may be present for 1-3 months with little or no fever
• children may present with acute onset of fever, irritability, lethargy & local inflammation of < 3 weeks duration
• findings on physical exam may include

• point tenderness, muscle spasm, & draining sinus
• sinus tract overlying a bone
• purulent, serous or serosangineous discharge
• foot ulcer with exposed bone

Laboratory

• complete blood count ( CBC)
• culture:*

• blood (all patients with suspected vertebral osteomyelitis)
• needle aspiration of pus from bone
• bone biopsy: gold standard

• biopsy through uninvolved skin (if associated with wound)

• sinus tract & wound drainage cultures not useful [4]

• ESR > 100 mm/hour is confirmatory, but ESR is variable & may not be elevated

• * it is not possible to predict the etiologic agent based upon epidemiology, thus cultures are essential to direct antibiotic therapy

Radiology

• Plain films are not positive for at least 10 days,
• lytic lesions may not be visible for 2-6 weeks.
• radionuclide bone scan may be positive within 2 days of infection
• computed tomography ( CT)

• soft tissue swelling around affected bone
• later, erosive changes in the bone are seen
• CT-guided percutaneous needle biopsy if suspected vertebral osteomyelitis with negative blood cultures [4]

• magnetic resonance imaging ( MRI)

• may be positive early (T1 & T2 images)
• may aid in localization of lesions & demonstration of sequestra
• not specific
• with gadolinium enhancement, identification of epidural abscess

Management

• < 5% of patients receiving prompt treatment progress to chronic osteomyelitis
• antibiotics should be administered only after appropriate specimens have been obtained for culture.
• duration of antibiotic therapy

• 6-8 weeks of IV antibiotics are indicated for acute hematogenous osteomyelitis; may require longer [4]
• 4-6 weeks of IV antibiotics in addition to surgical debridement for contiguous focus osteomyelitis or chronic osteomyelitis

• initial empiric antibiotics

• nafcillin 2 g IV every 4 hours or cefazolin 2 g IV every 8 hours plus rifampin
• 3rd generation cephalosporin if suspecting gram negative rod
• osteomyelitis in patients with diabetic foot ulcer

• beta-lactam/beta-lactamase inhibitor
• 3rd generation cephalosporin or 4th generation cephalosporin plus metronidazole

• antibiotic agents for specific pathogens

• Staphylococcus aureus or empiric therapy:

• nafcillin 2 g every 4 hours or cefazolin 2 g every 8 hours
• clindamycin or vancomycin are alternatives
• vancomycin 1 g IV every 12 hours for MRSA

• Streptococci

• penicillin G 4 million units every 6 hours
• ceftriaxone 2 g every 24 hours clindamycin & vancomycin are alternatives

• Enteric gram-negative organisms:

• ceftriaxone 1 g every 12 hours, or other 3rd generation cephalosporin
• Ciprofloxacin 750 mg PO every 12 hours if sensitivity permits

• Pseudomonas aeruginosa or Serratia

• ceftazidime 2 g IV every 8 hours plus gentamicin twice a week
• alternatives imipenem 500 mg IV every 6 hours or Cefepime or Zosyn plus aminoglycoside twice a week

• anaerobes

• clindamycin
• Unasyn 2 g IV every 8 hours or Flagyl 750 mg IV every 8 hours {alternatives}

• mixed aerobe/ anaerobe

• Unasyn
• Imipenem

• surgery

• debridement should be considered if there is poor response to therapy within 48 hours, or if there is undrained pus ( abscess) or septic arthritis
• chronic osteomyelitis requires complete drainage, debridement of sequestra, & removal of any prosthetic material in addition to 4-6 weeks of antibiotic therapy based on culture of bone
• primary wound closure is contraindicated [8]

• hyperbaric oxygen as adjunctive therapy in post- traumatic or chronic osteomyelitis
• skin flaps & bone grafts may facilitate healing 9 ) hardware-related osteomyelitis

• for most patients, orthopedic hardware should be removed with surgical debridement of infected bone
• if symptoms last < 1 month, surgical debridement with retention of hardware plus 3-6 months of antibiotic therapy with a fluoroquinolone + rifampin [4]

More General Terms

• bone disease
• bacterial infection

References

1. Harrison's Principles of Internal Medicine, 13th ed., Companion Handbook, Isselbacher et al (eds), McGraw-Hill Inc. NY 1995, pg 200
2. contributions from Robert Libke, M.D., UCSF Fresno
3. The Sanford Guide to Antimicrobial Therapy, 29th ed., Gilbert DM et al (editors), Antimicrobial Therapy, Inc., Hyde Park, VT, 1999
4. Medical Knowledge Self Assessment Program (MKSAP) 11, 14, 15, American College of Physicians, Philadelphia 1998, 2006, 2009
5. Lazzarini L, Mader JT, Calhoun JH. Osteomyelitis in long bones. J Bone Joint Surg Am. 2004 Oct;86-A(10):2305-18. Review. PMID: [1]
6. Parsons B, Strauss E. Surgical management of chronic osteomyelitis. Am J Surg. 2004 Jul;188(1A Suppl):57-66. Review. PMID: [2]
7. Carek PJ, Dickerson LM, Sack JL. Diagnosis and management of osteomyelitis. Am Fam Physician. 2001 Jun 15;63(12):2413-20. Review. Erratum in: Am Fam Physician 2002 May 1;65(9):1751. PMID: [3]
8. Geriatric Review Syllabus, 7th edition Parada JT et al (eds) American Geriatrics Society, 2010
9. National Guideline Clearinghouse Suspected osteomyelitis in patients with diabetes mellitus. American College of Radiology ngc-guideline: [4]
   - Best evidence statement (BESt). Treatment of acute hematogenous osteomyelitis. Cincinnati Children's Hospital Medical Center ngc-guideline: [5]

osteomyelitis