Osteomyelitis – Causes, Symptoms, Diagnosis, Treatment and Ongoing care

Basics

Description

An acute or chronic inflammation of the bone. This may be limited to a single portion of the bone or may involve several regions. Osteomyelitis can occur as a result of hematogenous seeding, contiguous spread of infection, or direct inoculation into intact bone such as from trauma or surgery.Two major classification systems for osteomyelitis (1) Waldvogel classification: Classified according to the duration of the disease (acute or chronic), the mechanism of infection (hematogenous or contiguous), and the presence of vascular insufficiencyCierny-Mader classification: Based on the portion of bone affected, the physiologic status of the host, and other risk factorsSystem(s) affected: MusculoskeletalSpecial situations: Vertebral Osteomyelitis (2) Acute, subacute, or chronicMay result from hematogenous seeding, direct inoculation, or contiguous spreadBack pain (most common initial symptom)Lumbar spine (most commonly involved) followed by thoracicBone biopsy (open technique) has 93% pathogen recovery.Infections of prosthetic joints (3) Obtaining specific diagnosis and targeted therapy quicker (easy access)X-ray of joint initially done then 3-phase bone scanTreat with combination of antibiotics including Rifampicin.Post-traumatic infections Depends on type of fracture, level of contamination, and severity of tissue injuryTibia most commonly involved

Epidemiology

Predominant age: Commonly seen in older adultsPredominant sex: Male > FemaleHematogenous osteomyelitis (4): Adults (most patients >50 years old): vertebralChildren: long bonesContiguous osteomyelitis (1): Predominantly found in patients with diabetes mellitus or vascular insufficiency

Incidence

Incidence is low due to high resistance of normal bone to infection and occur in patients with risk factor (3).25% lifetime risk of diabetics of developing foot complication (5)

Prevalence

Up to 66% of diabetics with foot ulcers (1)

Risk Factors

Diabetes mellitusRecent trauma/surgeryForeign body (e.g., prosthetic implant)Neuropathy and vascular insufficiencyImmunosuppressionSickle-cell diseaseInjection drug usePrevious osteomyelitis

General Prevention

Antibiotic prophylaxis: Clean bone surgery: Antibiotics should be administered IV from 30 minutes before skin incision to no longer than 24 hours after the operation.Closed fractures: Antistaphylococcal penicillins or 1st- or 2nd-generation cephalosporinsOpen fractures: In patients who can receive antibiotics within 6 hours of injury and who receive prompt operative treatment, administration of antistaphylococcal penicillins or 1st- or 2nd-generation cephalosporins for 24 hours is appropriate.All patients with diabetes mellitus should have a complete foot examination by a health care professional yearly (1).

Pathophysiology

Infection is caused by biofilm bacteria, a community of bacteria surrounded by a matrix of polymers, which protects bacteria from antimicrobial agents and host immune responses (2).Acute: Suppurative infection of bone with edema and vascular compromise leading to sequestraChronic: Presence of necrotic bone or sequestra or recurrence of previous infection

Etiology

Hematogenous osteomyelitis (commonly a monomicrobial infection) (1): S. aureus (most common) with high percentage of MRSA (50%) (2)Coagulase-negative staphylococci and aerobic gram-negative bacteriaSalmonella sp. (sickle-cell patients)M. tuberculosis and fungi (rare) in endemic areas or in immunocompromised hostsContiguous focus osteomyelitis (commonly a polymicrobial infection) (): Diabetes or vascular insufficiency: Coagulase-positive and -negative staphylococciStreptococci, gram-negative bacilli, anaerobes (Peptostreptococcus sp.)Prosthetic device: Coagulase-negative staphylococci and S. aureus

Commonly Associated Conditions

See Risk factors

 

Diagnosis

History

Hematogenous osteomyelitis: Conditions predisposing to bacteremia (Diabetes and renal insufficiency) (2)Other sites of infectionContiguous osteomyelitis and vascular insufficiency–associated infection: Recent trauma/surgery within 1–2 monthsPresence of prosthetic deviceHistory of diabetesChronic osteomyelitis: History of acute osteomyelitis

Physical Exam

Restriction of movement of the involved extremity or refusal to bear weightPain or tenderness in the infected areaSigns of localized inflammationFever and/or chillsMotor and sensory deficits (vertebral infection)Visible or palpable bone with a metal probe (“positive probe-to-bone test”) (5)[A]Ulcer >2 cm wide and >3 mm deep increases likelihood in diabetic foot ulcers (1)[B].In patients with diabetes, classic signs and symptoms of infection may be masked due to vascular disease and neuropathy.

Diagnostic Tests & Interpretation

Lab

Initial lab tests

Labs (1)[C]:

WBC is not a reliable indicator and can be normal even when infection is present (2).CRP is usually elevated but nonspecific.ESR is high in most cases. ESR >70 mm/hour increases likelihood in diabetic lower extremity ulcer (6)[B].Drugs that may alter lab results: Antimicrobial agents given prior to cultureDisorders that may alter lab results: Immunosuppression, chronic inflammatory disease, other/adjacent sites of infection

Follow-Up & Special Considerations

A persistently elevated CRP but not ESR at 4–6 weeks can be associated with persistent osteomyelitis (1)[C].Patients receiving prolonged antimicrobial therapy should have the following tests to monitor for adverse reactions (1)[C]:

Imaging

Initial approach

Routine radiography standard 1st-line imaging (7)[C]: Classic triad for osteomyelitis is demineralization, periosteal reaction, and bone destruction (5). Bone destruction is not apparent on plain films until after 10–21 days of infection.Bone must undergo 30–50% destruction before it is evident on films.MRI For visualization of septic arthritis, spinal infection, and diabetic foot infections (7)[C]T1-weighted image: Low signal intensityT2-weighted image: High signal intensityMI with gadolinium sensitivity and specificity range from 60–100% and 50–90% respectively (2)[C]CT Better than standard radiography in fragments and sequestration but inferior to MRI in soft tissue and bone marrow assessmentUseful to define surrounding soft tissues and identification of sequestra

Follow-Up & Special Considerations

Radionuclide scanning (e.g., technetium, indium, or gallium) is useful when diagnosis is ambiguous or extent of disease in question but is limited by reports of low sensitivity and specificity.MRI is not helpful in assessing the response to therapy owing to persistence of bony edema (1)[C].

Diagnostic Procedures/Surgery

Cultures (4)[C]: Definitive diagnosis is made by blood culture (hematogenous) and by needle aspiration/bone biopsy with subsequent demonstration of the microorganism by culture and sensitivity or histology.Appropriate pathogen isolated in blood culture combined with radiographic evidence may obviate need for bone culture.Wound swabs and sinus tract cultures have utility for infection control and correlate well with the presence of S. aureus in deep cultures.Image-guided bone biopsy for vertebral osteomyelitis unless (+) blood culture and (+) radiographic evidence

Pathological Findings

Inflammatory process of bone with pyogenic bacteria, necrosis

Differential Diagnosis

Systemic infection from other sourceAseptic bone infarctionLocalized inflammation or infection of overlying skin and soft tissues (e.g., gout)Brodie abscessNeuropathic joint disease (Charcot foot)Fractures/traumaTumor

Treatment

Medication

Duration of therapy 4–6 weeks for acute osteomyelitis and generally >8 weeks for chronic osteomyelitis.Determine therapy based on culture results.Fluoroquinolones may be used as an alternative to ß-lactam antibiotics (use with caution to limit antibiotic resistance) (8)[A].

First Line

S. aureus (1)[C]: Methicillin-sensitive: Nafcillin or oxacillin 1.5–2 g IV q4–6h or cefazolin 1–2 g IV q8hMethicillin-resistant: Vancomycin 15 mg/kg or 1 g IV q12hPenicillin-sensitive Streptococcus sp.: Penicillin G 20 million U/d IV divided q4–6h or ceftriaxone 1–2 g IV/IM q24h or cefazolin 1–2 g IV q8hEnterococci or streptococci with MIC =0.5 µg/mL: Penicillin G 20 million U/24 h IV divided q4–6h or ampicillin 2 g IV q4h ± gentamicin 1 mg/kg IV q8hGram-negative bacilli: Quinolone 400–750 mg IV/PO q12hAnaerobes: Clindamycin 600 mg IV q6h or metronidazole 500 mg PO q6–8h

Second Line

S. aureus (1)[C]: Methicillin-sensitive: Vancomycin 15 mg/kg or 1 g IV q12h ± rifampin 600 mg q24h or daptomycin 6 mg/kg IV q24hMethicillin-resistant: Linezolid 600 mg PO/IV q12h or daptomycin 6 mg/kg IV q24hPenicillin-sensitive Streptococcus sp.: Vancomycin 15 mg/kg or 1 g IV q12hEnterococci or streptococci with MIC =0.5 µg/mL: Vancomycin 15 mg/kg or 1 g IV q12h ± gentamicin 1 mg/kg IV q8hGram-negative bacilli: Ciprofloxacin 400 mg IV q12h or 750 mg PO q12h or levofloxacin 500–750 mg IV/PO q24h; ceftriaxone 2 g IV q24h or cefotaxime 2 g IV q6–8h or ceftazidime 2 g IV q8h

Additional Treatment

General Measures

Adequate nutritionSmoking-cessation counselingControl of diabetes

Additional Therapies

Hyperbaric oxygen therapy may be useful as an adjunctive treatment, but data are limited.

Surgery/Other Procedures

Surgical drainage, dead-space management, adequate soft-tissue coverage, restoration of blood supply, and removal of necrotic tissues are of utmost importance to effect cure.

Pediatric Considerations

Medullary osteomyelitis (stage 1) in children may be treated without surgical intervention.

In-Patient Considerations

Initial Stabilization

Correct electrolyte imbalances, hyperglycemia, azotemia, and acidosis.Control pain.

Admission Criteria

Hospitalize the patient with suspected acute osteomyelitis for diagnostic workup and initial treatment.

Nursing

Bed rest and immobilization of the involved bone and/or joint

Discharge Criteria

Clinical and laboratory evidence of resolving infection and appropriate outpatient therapy

Ongoing Care

Follow-Up Recommendations

Patient Monitoring

Blood levels of antimicrobial agents, ESR, CRP, and repeat plain radiography

Patient Education

Diabetic glycemic control and foot care

Prognosis

Superficial and medullary osteomyelitis treated with antimicrobial and surgical therapy has a response rate of 90–100%.Morbidity and mortality are contingent on the underlying health of the host.Up to 36% recurrence in diabeticsIncreased mortality after amputation

Complications

Abscess formationBacteremiaFracture/nonunionLoosening of prosthetic implantPostoperative infection

References

1. Sia IG, Berbari EF. Osteomyelitis. Best Prac and Res Clin Rheum. 2006;20(6):1065–81.

2. Bhavan KP, Marschall J, Olsen MA, Fraser VJ, Wright NM, Warren DK et al. The Epidemiology of hematogenous vertebral osteomyelitis: a cohort study in a tertiary care hospital. BMC infectious diseases.2010;10:158.

3. Concia E, Prandini N, Massari L, Ghisellini F, Consoli V, Menichetti F, Lazzeri E et al. Osteomyelitis: clinical update for practical guidelines. Nucl Med Commun. 2006;27:645–60.

4. Calhoun JH, Manring MM. Adult Osteomyelitis. Infect Dis Clin N Am. 2005;19:765–86.

5. Hartemann-Heurtier A, Senneville E et al. Diabetic foot osteomyelitis. Diabetes Metab. 2008;34:87–95.

6. Dinh MT, et al. Diagnostic Accuracy of the Physical Examination and Imaging Tests for Osteomyelitis Underlying Diabetic Foot Ulcers: Meta Analysis. Clin Inf Dis. 2008;47:519–27.

7. Stumpe KD, Strobel K et al. Osteomyelitis and arthritis. Semin Nucl Med. 2009;39:27–35.

8. Karamanis EM, Matthaiou DK, Moraitis LI, et al. Fluoroquinolones versus beta-lactam based regimens for the treatment of osteomyelitis: a meta-analysis of randomized controlled trials. Spine. 2008;33:E297–304.

Codes

ICD9

730.00 Acute osteomyelitis, site unspecified730.10 Chronic osteomyelitis, site unspecified730.20 Unspecified osteomyelitis, site unspecified

Snomed

60168000 osteomyelitis (disorder)409780002 acute osteomyelitis (disorder)40970001 chronic osteomyelitis (disorder)

Clinical Pearls

Osteomyelitis can occur as a result of hematogenous seeding, contiguous spread, or direct inoculation into the bone.Hematogenous osteomyelitis is usually monomicrobial, whereas osteomyelitis owing to contiguous spread or direct inoculation is usually polymicrobial.S. aureus, coagulase-negative staphylococci, and aerobic gram-negative bacilli are the most common organisms.Acute osteomyelitis typically presents with gradual onset of pain. Local findings (e.g., tenderness, warmth, erythema, and swelling) and systemic symptoms (e.g., fever and chills) also may be present.Treatment of osteomyelitis often requires both surgical débridement and antimicrobial therapy. At least 6 weeks of antimicrobial therapy is recommended.