osteomyelitis. objectives epidemiology major classification systems and types pathogenesis,...
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Osteomyelitis
Objectives
• Epidemiology• Major classification systems and types • Pathogenesis, Microbiology• Clinical Manifestations• Diagnosis• Treatment
Epidemiology
• Incidence of acute osteomyelitis– 10 per 100,000 in Sweden– Higher incidence in warm and humid climates and
lower socioeconomic areas
• Incidence of chronic osteomyelitis– Estimated to be 15-30 per 100,000 over the last
10 years
Epidemiology
• Prosthetic implants– 1.8 million prosthetic joint implants and 2 million
devices for hip fractures per year– In the 1970’s, 10% of all major hip procedures
involving an implant resulted in infection– Currently, antibiotic prophylaxis has decreased
infection rates to <1% in hip and 2% in knee prosthetic surgery
– HOWEVER prosthetic joint implants remain the most common cause of joint infections
• 1-2% for total knee and hip arthroplasty
ClassificationCierny and Mader Classification SystemBased on:
Affected portion of the bone - “Stages”Physiologic status of the host – “Classes”Factors affecting the local environment
Combines 4 anatomic “stages” with three physiologic host “categories”12 possible combinations
Lends itself to the treatment and prognosis of osteomyelitisE.g. stage 1 (medullary osteomyelitis) can usually be
treated with antibiotics alone
Cierny and Mader Classification
Classification
• Waldvogel Classification System– Based on PATHOGENIC mechanisms of infection
• Waldvogel System– Hematogenous osteomyelitis
• Acute vs chronic– Contiguous focus osteomyelitis – soft tissue
infection, abcess, prosthesis• Vascular insufficiency (DM, PVD)• Without vascular insufficiency (trauma, prosthesis)
– Acute vs chronic
Pathophysiology
• Progressive infection of bone– Inflammatory destruction– New bone formation
• Three major categories (Waldvogel)– Contiguous focus without vascular insufficiency
• Trauma, surgery, prosthesis– Contiguous focus with vascular insufficiency
• DM or PVD– Hematogenous spread
PathophysiologyACUTE
Bacterial seeding, suppurative infectionVascular compromise
Pre-existing – DM or PVDTraumatic – disruption due to traumaAs a consequence of osteomyelitis
Acute suppurative infection = edema , increased intramedullary pressure = loss of medullary and periosteal blood supply
CHRONICAvascular areas of infection with necrotic bone
Nidus of dead bone refractory to clinical care
Pathophysiology: Acute vs. Chronic
• Chronic Osteomyelitis– Dead bone (sequestrum)– Bony encasement of the sequestrum(involucrum)– Local bone loss– Persistent drainage and/or sinus tracts
Clinical Manifestations• Acute – gradual onset over days
– Typical: dull pain with or without movment– Other (some, all, or none…)
• Local findings (tenderness, warmth, erythema, swelling)• Systemic findings (fever / chills)
– Hip, vertebrae, pelvis with fewer SXs – Septic arthritis – knee, hip, shoulder
• Subacute and chronic – mild pain over several weeks
• Chronic - sinus tracts, prosthesis, chronic soft tissue ulceration (DM)
Hematogenous Osteomyelitis
• Disease of children– 20% of all adult osteo cases– 85% of hematogenous osteo cases in pts < 17
• M:F 2:1 for unknown reasons• Site of infection varies with age
– Children: metaphyses of long bones– Adults: vertebrae > clavicles, pelvis/SI, long bones
• Predilection for specific sites based on blood supply
Blood Supply Based on Age
osteo-bloodsupply.jpg
Hematogenous Osteomyelitis
osteo-bloodsupply2.jpg
Hematogenous Osteomyelitis
• Risk factors:– IVDU, central lines, HD, urethral catheters, sickle
cell disease• Adult long bone
– Diaphysis with extension• May enter joint -> septic arthritis• Sinus tracts -> adherent periosteum
• Ususally monomicrobial– Staph aureus
Hematogenous Osteomyelitis: Infecting Organisms
Infants Children AdultsStaph aureus Staph aureus Staph aureusStrep agalactiae Strep pyogenesE. coli H. influenzae
Microorganisms Associated with Certain Conditions
Lancet 2004 364:369-79.
• Sickle cell- Salmonella, S pneumoniae
• HIV- Bartonella henselae, B quintana
• Human or animal bites- Pasteurella multocida, Eikenella corrodens
• Foreign-body – coag (-) Staph, Proprionibacterium sp
• Immunocompromised- Aspergillus sp, Candida albicans
• IVDU: Pseudomonas, Serratia m, Tb
Hematogenous Osteomyelitis: Clinical Presentation
• Neonatal– Paucity of systemic and local findings– Edema and decreased motion of a limb
• Children– Abrupt fever, irritability, lethargy– Local signs of inflammation
• Adults– Nonspecific pain and few constitutional symptoms– Occasional acute presentations
Vertebral Osteomyelitis
• Route of infection most often hematogenous• Disease of adults• Increasing incidence• Route of infection: segmental arteries
– Freq involvement of 2 adjacent vertebrae and disk due to bifurcation of the artery
• Microbiology:– Staph aureus > 50%– Enteric GNRs with urologic instumentation
Vertebral Osteomyelitis: Sources of Infection
• S= Surgery of spine or disc• P= Pulmonary infection with bacteremia• I= IVDU• N= Nephrologic disease• E= Endocarditis• D= Dental work• I= Infected catheter• S= Soft tissue infection
Vertebral Osteomyelitis: Symptoms
• Insidious onset of spinal pain over 3 weeks to 3 months - near universal
• Exam and lab findings:– Local tenderness – near universal– Fevers – 50%– Leukocytosis – 50%– Elevated ESR – 80%
• Prognostic value– Erythema over the involved bones– Motor and sensory deficits in 6-15% of patients
Contiguous Spread Without Vascular Compromise
• Predisposing factors:– Surgical reduction and internal fixation of a fracture– Trauma, open fractures– Prostheses– Chronic soft tissue infections
• Presents ~ 1 month after inoculation of the organisms• Infecting organisms
– Polymicrobial infection common– S. aureus, Gram negative bacilli, anaerobes
• Loss of bone stability, necrosis, soft tissue damage common
Contiguous Spread With Vascular Compromise
• DM and PVD• Most common site = small bones of feet• Combined risk factors
– Peripheral neuropathy, lack of sensation = repetitive microtrauma
– Inadequate tissue perfusion = poor wound healing
• Polymicrobial– Coag (+/-) Staph, Strep spp, Enterococcus, GNR,
anaerobes
Contiguous Spread With Vascular Compromise
• May present later due to lack of patient complaints– Concurrent peripheral neuropathy– Fever and systemic toxicity are frequently absent
• Physical exam– Diminished dorsalis pedis and posterior tibial pulses– Poor capillary refill– Decreases sensation
• DX– Exposed bone before or after debridement of ulcer bed– Probe to bone
• Resection or amputation almost always needed
Contiguous focus osteomyelitis in a 40-year-old male patient with diabetes mellitus. Bony destruction is visible around the proximal and distal phalanges of the first toe.
Osteomyelitis: Special Situations
• Hemodialysis patients– Most are hematogenous in origin– S. aureus and S. epidermidis– Ribs and thoracic vertebrae most common sites
• Sickle cell patients– Salmonella spp, Proteus, S. aureus– Difficult to differentiate thrombotic marrow crisis
from osteomyelitis– May have multiple sites of bone infection
Osteomyelitis: Special Situations
• IV drug users– Common sites include vertebrae, SI, pubis,
clavicles/SC– Pseudomonas, S. aureus, S. epidermidis, GNR, Candida
spp.– Clinical signs and symptoms may be subtle
• Brodie’s Abscess– Subacute osteomyelitis of – classically – distal tibia– Chronic dull pain– Mimics tumor, etc
Diagnosis
• Difficult to diagnose noninvasively– Symptoms, exam, labs, and imaging studies can help
to establish an index of suspicion• Definitive diagnosis = bacterial isolation via bone
BX with compatible histologic findings• Lack of good prospective studies using this
standard– Newman et al. DM foot ulcers and osteo
• Osteo DX in 9/41 (22%) pts without bone CX• Osteo DX in 28/41 (68%) by bone BX
Diagnosis
• Factors affecting the accuracy of current noninvasive tests:– Intensity of the inflammation– Chronicity of the infection– Site of the infection– Vascularity– Presence or absence of a foreign body– Presence or absence of associated pathology
Diagnosis: Bone Biopsy
• Gold standard– Isolation of pathogen via sterile bone BX– Compatible histopathologic features
• Necrotic bone with inflammatory exudate
• CX (+) in up to 87% of cases– ABX can be held 48-72 hours prior to increase yield
• When is bone BX not needed?– Positive blood CX and consistent radiographic studies– Further compromise site with vascular compromise
Diagnosis: Bone Biopsy
• Non invasive CX techniques
• Swab CX correlate poorly with bone BX – 20%
• Sinus tract CX generally not useful – 44% of sinus tract CX contained pathogen on bone
BX– Correlation higher with S. aureus and Salmonella
Diagnosis: Bone Biopsy
• Invasive techniques– Open preferred to percutaneous (PC) needle BX
• Sampling error• Limited sensitivity in post operative and trauma• (-) PC needle BX and high index of suspicion? = open BX
– Percutaneous• ALWAYS thru intact tissues• 2 specimens; CX and path• Always thru uninvolved skin• Fluro guided• Hold ABX
Diagnosis: Plain Films
• Pros– Relatively inexpensive– Readily available– May help make DX– Help in selection and
interpretation of other studies
– Allow exclusion of other conditions
• Cons– Lack sensitivity,
specificity in DX – Lag progress of infection
and healing– Difficult to distinguish
etiology of bony changes– Difficult to tell whether
infection is active or inactive
Diagnosis: Plain Films• Earliest changes
– Sublet soft tissue changes (3-5 days)– Regional osteopenia– Periosteal thickening
• Additional findings– Mixed lucency and sclerosis– Fracture non union, periprosthetic lucency
• Confounding osseous findings– Healing fracture: Charcot joint– Tumors: osteosarcoma, giant cell– Post traumatic changes
Diagnosis: CT Scan• Study of choice when MRI is contraindicated
• Evaluation of areas with focal exam findings but normal plain films
• Order with and without contrast• Accurate in detecting:
– Cortical destruction– Intraosseous gas– Periosteal reaction– Soft tissue extension
Diagnosis: MRI
• Excellent spatial resolution– Helpful in differentiating bone vs. soft tissue changes
• Very sensitive– ABNL marrow edema 3-5 days– High Negatie predictive value
• Osteo effectively ruled out if SXs > 1 week and no MRI changes
• Non specific• May overestimate extent of infection,
underestimate response to TX
Diagnosis: MRI
• Especially useful in vertebral or foot involvementSpine– Delineates soft tissue/epidural involvement– May show cord impingementFoot– Equally specific and more sensitive than bone scan
Diagnosis: Nuclear Modalities
• Types– Three phase bone scan– Gallium scan– Tagged WBC scan
• When to use?– Equal sensitivity to MRI, less specific in acute
osteo– Loses sensitivity in complicated / chronic cases– Not affected by metal hardware
Diagnosis: 3 Phase Bone Scan• Tc-99 bound to phosphorus • Accumulates in areas of increased osteoblastic activity / bone
turnover• Images
– Immediate (blood flow phase)– 15 minute (blood pooling phase)– 4 hour (osseous phase)
• Interpretation– Osteomyelitis: Intense uptake in all 3 phases– Cellulitis: Increased activity in the phase 1 and 2, normal or diffuse
increased activity in phase 3• TRACER UPTAKE IS DEPENDANT ON BLOOD FLOW
– Limits sensitivity in DM, chronic osteo
Diagnosis: 3 Phase Bone Scan
• Pros– Excellent sensitivity and
specificity (95%) in 2 to 3 days IF PLAIN FILMS NL
– Considered the test of choice if plain films normal
• Cons– Decreased sensitivity in
chronic osteo– Multiple possible false
positives: post-injury post-surgery diabetic feet septic arthritis cancer healed osteomyelitis Paget’s disease
Diagnosis: Other Tests• Indium labeled leukocyte scans
– Accumulate at site of infection – NOT SPECIFIC FOR BONE
• Gallium and dual tracer scans– Use gallium-67 alone or with Tc-99– Ga-67 has affinity for acute phase reactants– May be more specific than triple phase study– Scan typically performed 24 hours after injection
• Ultrasound– Fluid collections next to the bone, periosteal elevation and thickening– May improve the yield from needle biopsies
Imaging: Diagnosis Overview
Acute Plain films + Done if + Blood Cx_
MRI or Bone Scan
Complicated Spine or Diabetic Foot?
Yes MRI
No
Hardware? MRI (or CT)NoYes
Bone Scan
Osteomyelitis: Treatment
• Frequently requires surgical and antimicrobial TX– Sugery for drainage, debridement, dead space
management, removal of hardware– Specific antimicrobial coverage
• Bone infection may recur years after apparently successful treatment
• Predisposing factors to recurrence– Trauma to the area– Suppression of the host’s immune response
Treatment: Antibiotic Selection
• Tailored to culture and sensitivity findings• Broad spectrum if CX not obtainable
Treatment: Duration • Int J Infect Dis 2005 9(3):127-38 . 93 clinical trials
from 1968-2000. Available literature on the treatment of osteomyelitis is inadequate to determine the best agent(s), route, or duration of therapy.
• Infect Dis Clin N Am 19(2005): 765-786– Duration: 4-6 weeks
• Animal models• Obervations re: bone revascularization (4 wks)• Lack of improved outcomes with courses of ABX > 6 wks (some up to 6
months)
Treatment: Route• Infect Dis Clin N Am 19(2005): 765-786
– Oral quinolone regimens can be started as soon as tolerated
– “Before changing to a nonquinolone oral regimen, the authors usually treat with 2 weeks of parenteral ABX.”
– “The decision to use oral vs. parenteral ABX should be based on microorganism sensitivity results, pt compliance, infectious disease consultation, and surgeon experience.”
• ID pager: 782-1663– Ask for Josh
Treatment: Additional Considerations
• Serial measurments of ESR and CRP can be useful– Add’l clinical / radiographic eval if ABNL at end of
TX• Suppressive TX warrented if infected
hardware must be retained• Shorter ABX regimens with full resection
(amputation) • ID pager: 782-1663
Questions?
Hyperbaric Oxygen Therapy
• Chronic osteomyelitis: HBO MAY be useful– Appropriate surgery and antibiotics also needed
• Increases intramedullary O2 tension more efficient phagocyte killing vs Staph aureus
• Potentiates the effect of tobramycin vs Pseudomonas• Promotes wound healing
Treatment: Acute Hematogenous Osteomyelitis
Children• Identify pathogen• Antibiotic therapy• 2 weeks of parenteral abx
before changing to oral antibiotics
• 4-6 weeks total • Avoid quinolones
Adults• Identify pathogen• Debridement surgery-
especially if no response to abx in 48hrs
• 4-6 weeks of parenteral abx
Osteomyelitis: Treatment• Intravenous Antibiotics and Bone Penetration with Staph
aureus infection
Clindamycin 98.3%Vancomycin 14.5%Nafcillin 9.6%Tobramycin 9.5%Cefazolin 5.7-6.1%Cephalothin 3.7%
• Significance of antibiotic concentrations is unclear
Treatment: Hematogenous Osteomyelitis
• Empiric regimen for adults
1. Nafcillin 2g IV q 4 hr2. Ceftriaxone 2g IV q 24 hr3. Vancomycin 1g IV q 12 hr and
Ciprofloxacin 400mg IV q 12 hr
Note: Regimen slightly different if on hemodialysis, IV drug abuser, sickle cell patient
Recommendations per ePocrates
Treatment: Vertebral Osteomyelitis
• Biopsy Debride Antibiotics • Open surgery not usually necessary
– Only needed for paravertebral or epidural abscesses, failure of abx, or instability
– Spontaneous bony fusion occurs in 1 to 12 months after abx
• Closely monitor neurologic status• Bed rest vs ambulation plus stabilization
Treatment: Vertebral Osteomyelitis
• Empiric regimen for adults
1. Nafcillin 2g IV q 4 hr and Ciprofloxacin 400mg IV q 12 hr2. Vancomycin 1g IV q 12 hr and
anti-pseudomonal beta-lactam or fluoroquinolone
Recommendations per ePocrates
Treatment: Contiguous Focus Osteomyelitis
• Primary problem is infected, necrotic bone• Must remove the nidus to adequately tx
– Includes removal of hardware– Antibiotic beads may be helpful
• Revascularization of bone after debridement takes approximately 3-4 weeks
• Antibiotics should be given for 4-6 weeks after the last major debridement surgery
Antibiotic Recommendations:Post-amputation
Surgical Procedure Duration1. Surgical transection of 4 wks
infected bone2. Excision of infected bone 2 wks3. Amputation proximal to 1-3 days
the infection
Contiguous Focus Osteomyelitis: With Vascular Disease
• Difficult to treat• Often beyond simple salvage by the time of
presentation• Determination of the vascular status of the
infected tissue is crucial• Several management options
Contiguous Focus Osteomyelitis: With Vascular Disease
• Management options– Suppressive antibiotic therapy– Local debridement surgery– Amputation– Adjunctive hyperbaric oxygen therapy