Septic Arthritis & Osteomyelitis Flashcards
infectious (septic) arthritis - overview
*infection involving the diarthrodial joint space
*rheumatologic emergency!
*typically acute in onset & monoarticular in localization, with predominant involvement of large, weight-bearing joints
*usually arises secondary to hematogenous seeding of the joint from distant focus of infection
*synovial tissue with increased susceptibility to infection due to lack of basement membrane & high degree of vascularity
causes of acute monoarthritis
*infectious arthritis
*osteomyelitis
*reactive arthritis
*crystal-induced synovitis
*trauma
*mechanical internal derangement
*rheumatoid arthritis and other connective tissue disorders
*pigmented villonodular synovitis
*metastatic tumors
“big four” causes of acute monoarthritis
- infectious arthritis
- crystal-induced synovitis
- trauma
- RA / other connective tissue disorders
infectious (septic) arthritis - clinical manifestations
*pain with BOTH passive & active motion
*erythema & heat overlying joint
*tenderness
*SWELLING
*limited range of motion
infectious (septic) arthritis - consequences of delayed diagnosis and treatment
*enhanced intraarticular inflammation:
-release of cytokines & proteases from PMNs
-pressure necrosis secondary to large effusion
*damage to ground substance of articular surface
*erosion of cartilage
*joint space narrowing
*OUTCOME: chronic pain with impaired joint function & mobility, causing disability
when to suspect diagnosis of infectious (septic) arthritis
*appropriate clinical setting: patient with defined risk factors for joint infection AND
*compatible clinical manifestations: joint pain, local inflammatory signs, fever
infectious (septic) arthritis - pathogenesis
- hematogenous seeding (most common)
- joint aspiration/inoculation
- animal or human bites
- foreign body puncture wounds
- spread from contiguous infection (osteomyelitis)
- arthroscopic surgery
- open surgical procedures
infectious (septic) arthritis - predisposing factors
*recent joint surgery
*age > 80
*prosthetic joint
*skin/soft tissue infection
*diabetes
*rheumatoid arthritis
*skin infection
infectious (septic) arthritis - historical features
*history of prior joint damage or disease (underlying non-infectious arthritis or previous joint surgery/trauma)
*presenting symptoms: pain, erythema, swelling, fever, acute in onset
*number of involved joints is important
*sites of involved joints (common = knee, ankle, wrist, shoulder, hip, elbow)
*age of affected patient
infectious (septic) arthritis - physical exam findings
- signs of joint inflammation: erythema, warmth, tenderness to palpation, joint effusion
- decreased ROM of affected joint
- tenosynovitis
- skin rashes
- concurrent extraarticular infections
infectious (septic) arthritis - common sites of concurrent infection
*skin infections (cellulitis, abscesses)
*decubitus/pressure ulcers
*pneumonia
*UTI
*“primary” bacteriemia
presence of polyarticular disease as a clue for bacterial etiology
polyarticular disease = Staph aureus or Neisseria gonorrheae
presence of tenosynovitis as a clue for bacterial etiology
tenosynovitis = Neisseria gonorrheae
presence of rashes as a clue for bacterial etiology
rashes = Neisseria gonorrheae
presence of skin infection as a clue for bacterial etiology of septic arthritis
skin infection = Staph aureus or Strep
presence of pneumonia as a clue for bacterial etiology
pneumonia = Strep pneumoniae
infectious (septic) arthritis - labs & other assessment
*joint fluid analysis (arthrocentesis)
*blood cultures
*cultures of other infected sites
*radiology (plain X-ray, radioisotope scans, CT or MRI)
*synovial biopsy (rare)
infectious (septic) arthritis - joint fluid analysis (overview)
*provides diagnostic and therapeutic value
*should be performed in virtually all cases of suspected inflammatory arthritis
*studies should include: color, clarity, viscosity, RBC & WBC counts, glucose, gram stain, cultures, crystal examination
*can be classified based on: normal, non-inflammatory, inflammatory, and septic
joint fluid findings consistent of a diagnosis of infectious (septic) arthritis
*WBC > 100K with >75% PMNs
*gram stain may be positive
common pathogens that cause infectious (septic) arthritis
*bacteria most common:
1. Staph aureus (majority of cases)
2. Neisseria gonorrhoeae
3. Strep spp
*mycobacteria, fungi, and viruses can cause some
top 3 pathogens that cause infectious (septic) arthritis
- Staph aureus
- Streptococcus
- Neisseria gonorrhoeae (mostly in females and MSM)
infectious (septic) arthritis - management
*NEED BOTH:
1. adequate drainage (open or closed)
2. appropriate antibiotic therapy
*indications for open (surgical) drainage:
-hip/shoulder infections
-incomplete drainage with closed needle aspiration
-clinical failure of closed aspiration
infectious (septic) arthritis - principles of antibiotic therapy
*select an empiric Rx
*parenteral Rx is the traditional norm
*duration depends on organism:
-Staph aureus, GNRs = 4+ weeks
-Strep, H flu, gonorrhea = 2+ weeks
infectious (septic) arthritis - poor prognostic factors
*delay in initiation of therapy
*GNRs
*age > 60
*pre-existing RA
*infection of hip or shoulder
*polyarticular infections (>4 joints involved)
osteomyelitis - overview
*chronic or acute infection of the bone
*inflammatory process of bone, leading to bone destruction
*usually secondary to pyogenic bacteria
*facilitated by relative lack of local host defenses in bone
osteomyelitis - pathogenesis & predisposing factors
development of area of “damaged” bone (trauma, impaired blood supply, metabolic abnormalities)
*introduction of microbes (contiguous spread, direct inoculation, hematogenous seeding) with subsequent growth in a “protected” environment
*generation of local inflammation with production of toxins and cytokines that enhance osteoclastic & inhibit osteoblastic activity & PMN function
*bone necrosis and death cause formation of sequestra
osteomyelitis due to hematogenous seeding
*age of onset: 1-20yo & > 50
*bones involved: long bones, vertebrae
*precipitating factors: bacteremia
*microbiology: monomicrobial, Staph aureus or GNRs most common
*clinical findings: acute onset of fever, local tenderness, limited ROM
*usually curable with antibiotics alone
osteomyelitis due to contiguous spread
*age of onset: 40+ yo
*bones involved: femur, tibia
*precipitating factors: surgery, trauma, ST infection
*microbiology: mixed flora, usually includes Staph aureus or GNRs
*clinical findings: indolent onset of fever, erythema, swelling, heat
*requires aggressive debridement and long term IV antibiotics
osteomyelitis associated with peripheral vascular disease
*age of onset: 50+ yo
*bones involved: feet
*precipitating factors: diabetes, PVD
*microbiology: mixed flora, Staph/Strep, GNRs/anaerobes
*clinical findings: pain, swelling, erythema, drainage, ulcer
*requires surgery for treatment; relapse rates high without amputation
acute vs. chronic osteomyelitis
*acute: first presentation with short duration of preceding symptoms/signs
*chronic: clinical or X-ray evidence of infection or 6+ weeks
-XR evidence of sequestrum formation or sclerosis in addition to bone destruction
-relapse or persistence after Rx
-bone infection associated with a foreign body
osteomyelitis - potential complications
*sinus tract formation
*contiguous soft tissue infection
*abscess
*septic arthritis
*systemic infection
*bony deformity
*fracture
*malignancy
