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26 Cards in this Set
- Front
- Back
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Infectious (septic) arthritis: overview
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Infection involving the diarthrodial joint space
Typically acute in onset & monoarticular in localization with predominant involvement of the large weight-bearing joints Usually arises 2º to hematogenous seeding of joint from distant focus of infection -Synovial tissue with ↑’ed susceptibility to infxn d/t lack of basement membrane & high degree of vascularity Classic manifestations include pain with both passive & active motion, erythema & heat overlying joint, tenderness, swelling, & limited ROM Early diagnosis & appropriate Rx needed if joint damage & disability are to be avoided |
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Acute monoarthritis: causes
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Infectious arthritis* (~8-27% of cases)
Osteomyelitis Reactive arthritis Crystal-induced synovitis*→Gout/Pseudogout Trauma* Mechanical internal derangement RA/Other CVDs* Pigmented villonodular synovitis Metastatic tumors *"The big four" |
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Infectious arthritis: consequences of delayed dx and rx
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Enhanced intraarticular inflammation
-Release of cytokines & proteases -Pressure necrosis 2° to large effusion Damage to ground substance of articular surface Erosion of cartilage Joint space narrowing OUTCOME=Chronic pain with impaired joint function & mobility→Disability |
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Infectious arthritis: when should diagnosis be suspected
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Appropriate clinical setting→Defined risk factors for joint infection
+ Compatible clinical manifestations -Joint pain -Local inflammatory signs -Fever |
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Infectious arthritis: epidemiology
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Annual incidence of IA quite variable
-2 to 5 cases/100,000 in general population (20,000 cases per year in US) -5.5 to 12 cases/100,000 in children -28 to 32 cases/100,000 in pts with RA -40 to 68 cases/100,000 in pts with prosthetic jts Epidemiologic setting has major impact on causative organism -Elderly man with PJ→Staphylococci -Migratory arthritis in sexually active ♀→GC |
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Infectious arthritis: pathogenesis
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Multiple potential pathogenetic mechanisms
-Hematogenous seeding→50 to 75% of cases -Joint aspiration/inoculation→0.0002% of pts -Animal or human bites -Foreign body puncture wounds -Spread from contiguous infection→Osteo -Arthroscopic surgery→0.5% of procedures -Open surgical procedures Majority of pts (~90%) will have predisposing risk factor(s) |
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Infectious arthritis: predisposing risk factors
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Recent joint surgery +LR 6.9
Age >80 years +LR 3.5 Prosthetic joint +LR 3.1 Skin infection +LR 2.8 Diabetes mellitus +LR 2.7 Rheumatoid arthritis +LR 2.5 Skin infection + PJ +LR 15 [Remember: ~10% of pts will have no RFs] |
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Infectious arthritis: important historical features
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H/O prior joint damage or disease
-? Underlying noninfectious arthritis (RA, DJD) -? Previous joint surgery or trauma -How to distinguish underlying disease from superimposed infection? Local symptoms→Pain (85%), erythema, swelling (78%) Systemic symptoms→Fever (90-95%) Duration of symptoms→Days vs weeks # of involved joints→Polyarticular disease in 10% of pts (S. aureus, S. pneumoniae, GC) Sites of involved joints -Knee (~55%), ankle, wrist, shoulder, hip, elbow -“Unusual” joints→Think IDU ? joint prosthesis Age of affected patient Epidemiologic setting |
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Infectious arthritis: notable findings on examination
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Signs of joint inflammation
-Erythema -Warmth -Tenderness to palpation -Joint effusion Decreased ROM of affected joint Tenosynovitis Skin rashes Concurrent extraarticular infections |
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Infectious arthritis: sites of concurrent infection
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Skin infections
-Cellulitis -Abscesses (boils) Decubitus/pressure ulcers Pneumonia UTI “Primary” bacteremia REMEMBER: 30-50% of pts may not have an identifiable site of primary infection that serves as a source for bacteremia |
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Infectious arthritis: microbes involved in different presentations
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Polyarticular dz: S. aureus or GC
Tenosynovitis: GC Rashes: GC Skin infection: S. aureus or strep Pneumonia: S. pneumoniae |
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Infectious arthritis: laboratory and other assessments
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Joint fluid analysis→Arthrocentesis
Blood cultures (+ in up to 50% of pts) Cultures of other infected sites Radiology -Plain XRs -Radioisotope scans -CT or MRI Synovial biopsy Miscellaneous studies |
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Infectious arthritis: joint fluid analysis
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Provides diagnostic & therapeutic value
Should be performed in virtually all cases of suspected IA Studies on synovial fluid should include: -Color/Clarity/Viscosity -Total RBC & WBC counts with WBC diff -[Glucose] -Gram stain/Other special stains -Cultures -Crystal examination -[Joint fluid PCR] |
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Joint fluid analysis: classification
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Normal:
-Transparent -Clear - <200WBC -glucose = to blood Group 1 (noninflammatory) -Transparent -Yellow -200-2000 WBC - Glucose = to blood Group 2 (inflammatory) -Translucent -Opalescent -2000-100000 WBC -50% or more PMNs - >25 glucose Group 3 (septic -Opaque -Yellow-green ->100,000 WBC - > 75% PMN -Glucose <25 |
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Joint fluid ddx per classification
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Group I (noninflammatory)
-DJD -Trauma -Osteochondritis -Charcot joint -Hypertrophic osteoarthrop -Pigmented villonodular synovitis Group II Inflammatory -RA -Gout/Pseudogout -Reiter’s -AS -Psoriatic arthritis -Reactive arthritis -Rheum fever -SLE -PSS Group III -Bacterial infections Hemorrhagic -Hemophilia -Coagulopathies -Trauma -Charcot joint -Pigmented villonodular synovitis -Synovioma -Hemangioma |
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Infectious arthritis: microbiology
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Bacterial IA tends to be acute in onset
Most cases of GC IA in females & gay males -Incidence of GC IA is decreasing Most cases of pyogenic (non-GC) IA in males S. aureus most impt non-GC pathogen in adults GBS emerging pathogen in diabetics & the elderly GNRs associated with CA, immunosuppression, older age, narcotic use, chronic debilitating illness, or prior joint disease Staphylococci the predominant pathogen in pts with prosthetic joints |
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Infectious arthritis: management
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Successful management requires both:
-Adequate drainage → Closed vs open --Repeated closed needle aspirations --Arthroscopy --Open arthrotomy -Appropriate ATB Rx Indications for open drainage: -Hip infections -Incomplete drainage with closed needle aspiration -Clinical failure of closed aspiration Principles of ATB therapy: -Selection of empiric Rx based on clinical setting & results of preliminary studies (GmS) -Parenteral Rx the norm, at least for the induction phase of Rx (ie, minimum 1-2 wks) -Intraarticular ATB instillation not required -Rx duration is usually organism-dependent: --Strep, H. flu, GC→2 wks at minimum --S. aureus, GNRs→4 wks or more |
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Infectious arthritis: prognosis
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If Rx is initiated promptly & infection is 2° to GPC or GC, recovery usually complete
Poor prognostic factors include: -Delay in initiation of Rx (>1 wk after sx onset) -GNRs -Age >60 -Pre-existing RA -Infection of the hip or shoulder -Polyarticular infections (>4 joints involved) -Persistently + cxs after 7d of Rx |
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Infectious arthritis: summary
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Usual presentation is as an acute monoarthritis involving the knee
Hematogenous in origin & monomicrobial in etiology (S. aureus>>>GC) Pain & swelling are the cardinal features Arthrocentesis with synovial fluid analysis should ALWAYS be done Joint fluid is septic in character (Group III) Effective Rx requires both adequate drainage & appropriate antibiotics |
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Osteomyelitis: overview
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Inflammatory process of bone→Bone destruction
Usually 2° to pyogenic bacteria Facilitated by relative dearth of local host defenses Classification schemes: -Acute vs chronic --Acute: 1st presentation --Chronic: Previously Rx’ed & now relapsing -Pathogenetic --Hematogenous --Contiguous focus --Peripheral vascular disease (PVD)-associated Spectrum changing from hematogenous disease in children to contiguous or PVD-assoc disease in older adults |
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Osteomyelitis: classification
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Hematogenous
-1-20 yo or >50 at onset -Long bones, vertebrae -Precipitated by bacteremia -1 organism, S. aureus, GNR -Fever, local tenderness, ltd ROM Contiguous focus ->40 at onset -Femur, tibia -Precipitated by surgery/trauma, ST infection -Mixed, S.aureaus, GNR -Fever, erythema, swelling, heat PVD-associated ->50 yo at onset -Feet -Precipitated by diabetes, PVD -Mixed, Staph/Strep, GNR/Anaerobes -Pain, swelling ,erythema, drainage, ulcer |
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Osteomyelitis: Hematogenous
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Bimodal occurrence→Children/teenagers > middle-aged/older adults
Special populations at risk→SSD, IDU, HD Blood-borne seeding >>> trauma Long bones in children; vertebrae in adults Monomicrobial→S. aureus >> GNRs Local pain, point TTP, ↓ROM; fever ≤50% Blood cultures + in ~50% ATBs alone usually curative; sgy rarely needed Cure rate >80-90% |
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Osteomyelitis: Contiguous focus
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Older adults 2° to post-op infection, contiguous ST infxn, or puncture wound
Direct inoculation or contiguous spread Distal LEs (tibia, feet) > pelvis Mixed flora that usually includes S. aureus Indolent onset; variable local symptoms XR changes often but not always present Bone biopsy usually required for micro dx Aggressive I&D + long-term IV ATBs True “cure” in <50% of pts |
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Osteomyelitis: PVD-associated
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Diabetics >50 yo→Infected pedal ulcers with contiguous spread to underlying bone
Bones of the LEs, toes, & feet usually involved Mixed flora→Staph, strep, GNRs, anaerobes Local signs→Chronic ulceration with assoc cellulitis & purulent drainage=>If bone visible in base of ulcer, likelihood of osteomyelitis ~75+% XRs +/- abnl; MRI best test Bone biopsy with cultures req’ed for micro dx Medical Rx often unsuccessful→Sgy Relapse rates high w/o amputation |
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Osteomyelitis: special forms
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Chronic OM: Persistent/relapsing disease with necrotic bone present. S. aureus. Poorly responsive to Rx.
Vertebral OM: Indolent onset of back pain in older adults. LS spine. S. aureus. MRI. TB OM: 1% of cases of TB. 50% involve spine. Pain. Abnl CXR; +PPD. Fungal OM: Blood-borne. Indolent in onset. Candida, Blasto, Aspergillus. Bx. |
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Osteomyelitis: Summary
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May present as an acute (hematogenous) or chronic (contiguous, PVD) process
Multiple pathogenetic mechanisms Hematogenous=monomicrobial (S. aureus); contiguous & PVD=polymicrobial Local signs variable→Fistula = chronic OM XRs & scans +/- helpful; bone bx usually needed for dx ATBs alone for hematogenous; ATBs + sgy for contiguous & PVD |
