Ortho / Diabetic

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    Osteomyelitis

    • Progressive inflammatory destruction of bone, necrosis and new bone formation.
      • Acute (days to weeks)
      • Chronic (several weeks, months, years)
    • Origin
      • Hematogenous spread (children, elderly)
        • Stuck in end vessels (metaphysis of lone gones in children, and vertebral bodies in elderly)
      • Direct spread (begins adjacent to bone + spreads to bone)
        • Diabetic food infections (neuropathic or vascular ulcer)
        • Penetrating trauma

    Hematogenous Spread

    • Microbiology
      • Usually depends on age:
        • Young:
          • E.coli
          • Group B Strep
          • Staph aureus.  (predominates later in Adults)
          • Coag-negative staph
        • In Adults:
          • S.aureus
        • Also:
          • Gram-negative rods (Ederly b/c they are susceptible to gram negative bacteremias).
          • Fungal (Immunocompromized & IV catheters)
          • Pseudomonas (IV Drug users)
    • Symptoms:
      • Long-bones: Fever, chills, malaise + soft tissue swelling/pain. (children)
      • Vertebral osteomyelitis: Back pain, localized tenderness, high ESR / C-reactive protein.
    • DX:
      • Xray:
        • Takes 2-3 weeks to become positive. (6-8 weeks for vertebral)
        • demineralization (50% of calcium needs to be lost to show on Xray)
        • Findings:
          • Periosteal elevation
          • Loss of sharp bony margin ("Moth-eaten" look).
          • Soft tissue swelling.
          • Late-stage: increased calcification or sclerosis.
      • CT scan: Imaging study of choice when MRI cannot be obtained.
      • MRI: can detect early changes. (Sn 90%, Sp 80%)
        • False positives from fractures, tumors, healed osteomyelitis
      • Bone Scan: Quite sensitive (helpful if negative).
        • Inflammation or bone turnover can give false positives. (trauma, neoplasm, degenerative joint disease)
      • Pathology 
        • Children are treated empirically b/c metaphyseal osteomyelitis is close to empiphyseal plates.  Hard to operate and get biopsies.
        • Adults: long-bone: bebridement  or incission&Draginage is often needed.  Need deep tissue sample for culture and pathology.
        • Vertebral osteomyelitis:
          • Needle biopsy under CT guidance.  Evaluation:
            • Bacteriologic
            • Pathologic  (if suspected mycobacterial or fungal disease, or prev abx.)
          • Need culture for vertebral, because too many possible organisms to treat.
      • Screen shot 2013-09-21 at 6.01.14 PM.pngScreen shot 2013-09-21 at 6.01.00 PM.png
      • Screen shot 2013-09-21 at 6.02.06 PM.png
      • Taken from "Infections Diseases: A short clinical Course" 2nd ed. Frederick Southwick
    • Treatment:
      • Children treat empirically due to high risk metaphyseal biopsies (close to epiphyseal plate)
      • Spinal osteomyelitis: need culture because too many potential organisms.  No real empiric management.
      • Empiric abx should be avoided, try to culture organism.
      • Treat for 6 weeks.
        • s. aureus (MSSA - nafcillin or oxacillin, MRSA: vancomycin).  Oral: cipro-rifampin for MSSA.
        • Streptococci: pen G
        • Enteric G- organisms: cipro
        • Serratia or Pseudomonas: pip-tazo or imipenem.
        • Anaerobes: clindamycin or metronidazole.
      • Surgical debridement to:
        • Remove necrotic bone
        • Instability, cord compression, abscess drainage.

    Direct Spread (Contiguous Infection)

    • Types of osteomyelitis from contiguous infection:
      • Ortho surgery
      • Sinusitis spread (i.e. Pott's puffy tumor - edema of forehead)
      • Dental root infection.
      • Deep-seated pressure sores. (polymicrobial)
    • Symptoms (hard to pick up by symptoms)
      • Increasing pain.
      • Mild fever and minimal discharge.
    • Imaging: too difficult to interpret.
    • Causes:
      • S.aureus (most common by far)
      • Others:
        • Enterobactreciae
        • Pseudmonas (chronic osteomyelitis, puncture wounds to heel, comminuted fratures)
        • Anaerobic organisms (pressure sores, mandible from dental work)

    General Osteomyelitis Treatment Principles

    • General Notes:
      • When possible: only abx after results of cultures and susceptibility available.
      • Can give empiric therapy if need debridement (prevent hematogenous seeding). 
      • Generally poor abx penetration into bones (except fluoroquinolones!, great bone penetration)
      • Need IV therapy for 4-6 weeks (revascularization after debridement takes 3-4 weeks).
      • If bone necrosis, may need therapy up to 12 weeks.
      • Early abx before bone destruction improves outcomes.
      • Prefer fluoroquinolones for treatment (best bone penetration!!!!)
        • Enterobacterciae
        • Pseudomonas
        • Cipro (or levo) + rifampin for oral therapy.
      • Gentamicin-laden beads placed in wound in some countries (but no evidence yet!)
      • Treatment can take a year
      • Can monitor ESR and CRP (along with symptoms) for response to treatment.

     

    Prosthetic Joint Infections

    • Three categories:
      • Contiguous infections 6mo after surgery.
      • Chronic infections dxed 6-12mo post-op.  (contamination at time of surgery with low patogenic organisms)
      • Hematogenous spread (>2y post-op).
    • Organisms:
      • Coag-Positive staph + Coag-Negative staph  (both account for 3/4 of all prosthesis infections).
        • Coag-negative more insiduous, slow infection.
      • S.aureus (more acture presentation, less common).
    • Clinically hard to tell from mechanical loosening.
      • Joint pain
      • Fever often not present.
    • Diagnosed by joint-aspiration.
      • Relapse 10% in 3 years, and 26% in 10 years.
    • Treatment:
      • Early local debridement and abx therapy
        • Rifampin containing ab for Staph
      • If prosthetic loosened, need to remove.
        • Replace prosthesis with abx-impregnated cement (spacer to keep muscles taught)
        • Removal, debridements, and minimum 4-6wks of abx.
          • Replace joint in 3 months for "less virulent" organisms.
          • in 1 year for "more virulent" organisms.
      • Chronic Lifelong Antibiotic Therapy Guidelines:
        • Inclusion criteria
          • No systemic or severe local signs of infection.
          • Prosthesis is not loose
          • Surgery is not possible or desired.
        • Treatment
          • Do not use rifampin (high resistance rates with monotherapy).
          • Often septra or doxycycline for MRSA....

    Septic Arthritis

    • Hematogenous seeding of bacteria on synovial membrane.
    • Cytokines and proteases released into joint break down cartilage --> joint space narrowing.
    • Medical emergency --> irreversible joint damage can occur.
    • Risk factors:
      • Bacterial endocarditis (particularly S. aureus, and Enterococcus)
      • Joint disease (RA or Osteoarthritis)  
      • HIV (fungus or mycobacteria)
      • Intra-articular corticosteroids.  (fungus or mycobacteria)
      • IV drug use (Sternoclavicular joint - often S. aureus and Pseudomonas)
      • TNF therapy  i.e. in RA  (Listeria, Salmonella)
    • Organisms:
      • S.aureus (most common) - including MRSA
      • Neisseria gonorrheae (disseminated gonococcal infection)
      • Gram-negative bacilli in elderly  (secondary to UTI)
      • Listeria/Salmonella (if TNF therapy)
      • Viruses
        • Parvovirus B19
        • Hepatitis B virus
        • Rubella
        • Mumps
        • HIV
      • Lime Disease (Borrelia burgdorferi) - acute transient.
    • Symptoms:
      • Swelling, pain in a single joint accompanied by fever.
      • Any patient presenting with a monoarticular arthritis has septic arthritis until proven otherwise!
      • Joints involved:
        • Adults:
          • Knee (40-50%)
          • Hip (15-20%)
          • Followed by shoulder, wrist, ankle, elbow.
        • Children
          • hip (60%)
          • Knee (35%)
      • Half the patients with septic arthritis have underlying joint arthropathy (OA, RA, etc..) b/c synovial membrane already damaged and susceptible to seeding.
    • Dx:
      • Joint fluid aspirate
        • Leukocytes >200/mm^3  --> inflammatory  (often >50,000 with predominance of PMNs)
      • Gram stain often diagnostic.
      • Blood cultures often positive.
    • Treatment:
      • Joint drainage
        • Need to drain + wash the joint with arthroscopy (esp knee joints)
        • if hip joint -- cannot do arthroscopy, need surgery.
        • Idea is to wash out all the PMNs, to stop them from secreting powerful inflammatory mediators that damage the joint.
      • Systemic abx x3-4 weeks
        • nafcillin or oxacillin for S. aureus; 
        • 3rd gen cephalosporin or fluoroquinolone for gram-negatives
        • Vancomycin for MRSA
      • Despite abx 1/3 of people have residual joint damage (elderly and arthropathy pts).

    Disseminated Gonococcal Infection

    • Requires gonococcal entry into blood stream.
    • Typically spread of asymptomatic disease (women more likely)
      • Often following menstrual bleeding - bacteria gain entry into blood stream.
      • Terminal complement cascade important in killing Neisseria
        • Pts with congenital or acquired comlement deficiencies (i.e. SLE) have higher risk of disseminated gonococcal and meningococcal infection.
        • Specific Neisseria strains more often cause dissemination (lack of oute rmembrane protein II that form clear colonies or plates) --> often also penicillin sensitive.
    • Typically disease of sexually active young adults or teenagers.
    • Present with one of two syndromes:
    1. Tenosynovitis, dermatitis, and polyarthritis syndrome.
      • Fever, malaise, and arthralgias -->
      • Tenosynovitis:
        • Inflammation of tendons in wrist, fingers, and (less commonly) ankles, toes 
        • On exam: tenderness over tendon sheathes, pain with movement.
        • Tenosynovitis in a young person is pathognomic for disseminated gonococcemia.
      • Skin lesions
        • Pustular, pustular-vesicular and (less common) hemorrhagic or papular skin lesions.
        • Often periarticular and few in number. (4-10), transient, resolve in 3-4 days.
    2. Purulent arthritis without skin lesions
    • Dx:
      • Blood samples for culture (50% positive)
      • Culture & Gram stain of cervical and urethral exudates of skin lesion scrapings.
      • PCR of urine is also good.
    • Treatment
      • Disseminated pen-resistant gonococcus very common.
      • Use ceftriaxone (1g daily IV or IM) for 24-48h after clinical improvement.
        • Can then switch to cefixime, ciproflox, ofloxacin, levoflox to complete 7-10d therapy if strain is senstive.
      • If purulent joint:
        • Same management as septic arthritis.
        • Usually does not result in joint damage like S. aureus.
    • Prognosis:
      • Usually does not result in joint damage as S. aureus is.
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