Bone and Joint Infections

Question 1

Osteomyelitis

Answer 1

etiology:

• Medullary osteomyelitis
  
  • caused by hematogenous spread of bacteria
• Superficial osteomyelitis
  
  • caused by spread from contiguous focus of infection (overlying soft tissue infection) w/ or w/o vascular insufficiency or atherosclerosis (inadequate tissue perfusion)

S/O:

• infection may be acute, w/ abrupt development of local sxs and systemic toxicity, or indolent with indsidious onset of vague pain over site of infection, progressing to local tenderness and constitutional sxs (fever, malaise, anorexia, night sweats)
• back pain is often only sxs in vertebral osteomyelitis
• draining sinus tracts occur in chronic infections or infections of FB implants
• long bones and vertebrae are usual sites of infection

A:

• recognizing the disease
  
  • often occult presentation, missed-DX often
  • high index of suspicion for hematogenous disease
• confirming the DX
  
  • non-specific invasive tests (many)
  • radiiology can be confusing w/ verlying soft tissue infection
  • superficial cultures often not helpful (chronic open wounds)
  • most helpful diagnostic test is invasive procedure (bx of the bone); also provides cx info
• diagnostic criteria chart
  
  • definite
    
    • positive bone cx and positive histology
    • pus in bone at sx
    • atraumatically detached bone fragment removed from ulcer
    • intraosseus abscess on MRI
  • probable
    
    • visible cancellous bone in ulcer
    • MRI showing bone edema w/ other signs of osetomyelitis
    • bone sample w/ positive cx but neg/absent histology
    • bone sample w/ positive histology but neg/absent cx
  • possible
    
    • plain XR show cortical destruction
    • MRI shows bone edema or cloaca
    • probe to bone positive
    • visible cortical bone
    • non-healing wound despite adequate off-loading, and perfusion for >6 weeks OR ulcer of >2 weeks duration w/ clinical evidence of infection

P/TX:

• complicated by multiple host-factors (such as neuropathy, DM, vascular disease, immobility, tolerability and access to care for long-term therapy)
• chronic or recurrent if tx inadequate
• long-term abx therapy often needed
• surgical/medical therapy often needed
• serious morbidity as a consequences of tx failure

https://www.clinicalkey.com/topics/orthopedic-surgery/osteomyelitis-in-adults.html

Question 2

Hematogenous Osteomyelitis

Answer 2

= when bone tissue is seeded by pathogenic organisms during course of bacteremia

etiology:

• Staph aureus and beta-hemolytic strep (Group A and B)
• E coli in infants while > 1 yo, may see H. influenzae
• Salmonella spp. - sickle cell disease
• drug abuse: Gram-pos, Gram-neg, or Candida spp.
• vertebrae are most common site, but long bones, pelvis, and clavicle may also be affected

epidemiology:

• most common in infants and kids w/ minor trauma
  
  • metaphyses of tibia and femur
• in adults see more often in diaphysis with +/- extension into joint space

O:

• often ass w/ overlying soft tissue infection +/- abscess if extends beyond cortex
• may develop abrupt fever, lethargy or irritability but up to 50% vague c/o pain

Question 3

Vertebral Osteomyelitis

Answer 3

etiology:

• usually hematogenous in origin (segmental arteries)
  
  • 45% lumbar, 35% thoracic, 20% cervical
• categories:
  
  • ​pyogenic infections (commonly caused by Staph aureus)
  • nonpyogenic (granulomatous) infections (commonly caused by Mycobacterium tuberculosis)
• ​normal host and IV drug abusers - Staph aureus
• IV drug abusers, also Pseudomonas aeruginosa and other Gram-neg organisms

epidemiology:
* most commonly in men b/n 60 and 70 yo and involves lumbar spine

O:

• progressive, insidious pain develops over weeks-mos
• 50% of pts afebrile
• 90% have tenderness at site
• <15% may have motor-sensory deficits
• inflamm markers (sedimentation rate or C-reactive protein) may be elevated
• EXTENSION of infection outside vertebra can cause:
  
  • extension towards posterior
    
    • epidural, subdural abscesses or meningitis
      
      • epidural abscess = suspect if fever and severe back or neck pain are accompanied by radicular pain or sxs and signs indicative of spinal cord compression (eg incontinence, extremity weakness, pathologic reflexes)
    • concern for spinal cord compression and/or disruption
  • extension towards anterior
    
    • retropharyngeal, mediastinal, subphrenic or retroperitoneal abscesses

Question 4

Contiguous-Focus Osteomyelitis

Answer 4

**Without Vascular Insufficiency **

pathology:

• direct inoculation by traumatic bone injury, iatrogenic or spread from adjacent soft tissue infection
  
  • decubitus ulcers (bedsores)

etiology:

• often multiple organisms, Staph aureus
  epidemiology:
• common associated factors = h/o surgical reduction and internal fixation of fractures, prosthetic devices, open fx, chronic soft tissue infections, decubitus ulcers, burn, or regional soft tissue infection
• more common in older pts who generally develop infections following cellulitis or arthroplasties
• infection in younger pts usually occurs as a result of trauma or sx

O:

• history, low grade fever, pain, drainage

P/TX:

• difficult to treat, often sx/medical therapies required
• pts have good blood flow- allows the abx to penetrate tissues

**With Vascular Insufficiency **

etiology:

• cx often show mixed organisms:
  
  • Staph aureus, coagulase negative Staph
  • Strep, Enterococcus, Gram negative bacteria and anaerobes
• caused by impaired blood supply to susceptible tissues

epidemiology:

• minor trauma to feet of DM, often chronic
• usually in older pts and those with DM or severe atherosclerosis
  
  • in DM, small bones of feet most often involved; neuropathy may be present
  • risk of developing osteomyelitis in pts w/ large and deep diabetic ulcers and if the bone is exposed

P/TX:

• difficult to DX, can be chronic
• complications:
  
  • neuropathy and blunted tissue response
  • skin and deep soft-tissue infections
• Goals of therapy:
  
  • remove/tx/suppress infection
  • revascularize limb
  • maintain functional integrity of limb
• education
  
  • always inspect feet
  • dont cut toenails on own
  • dont wear socks or shoes too tight

Question 5

Infectious Arthritis

Answer 5

Arthritis = inflamm reaction w/n joint space (infectious vs non)

etiology:

• infectious causes
  
  • bacterial
    
    • Gonococcal (STD)
    • Non-gonococcal (not sexually transmitted)
  • viral, fungal, mycobacterial
  • post-infectious inflamm complications
• synovial tissue is highly vascular and lacks basement membrane so susceptible to hematogenous seeding of bacteria

epidemiology:

• pre-exisiting inflamm arthritis (ex: Osteoarthritis, rheumatoid arthritis)
• pre-existing joint disease (Charcot’s joint)
• intra-articular injections
• underlying DM, steroids, malignancy
• extra-articular infections (STDs, skin, UTIs)
• IV Drug Use (IVDU) or IV catheters
• Sx or penetrating trauma
• prosthetic joints

O:

• warm joint, not very mobile joint, erythematous
• all inflamed joints should be evaluated for infection
• blood cx not always positive
• inflammatory markers ie erythrocyte sedimentation rate (ESR) or C-reactive protein may be elevated - not non specific
• Diagnostic aspiration:
  
  • identifies infectious from non-infectious
  • therapeutic
  • microbial id allowing appropriate antimicrobial therapy

Question 6

Acute Bacterial Arthritis

Answer 6

etiology:

• infants
  
  • Group B Strep, Gram-neg bacilli, Staph aureus
• adolescents, adults <30 yo
  
  • N gonorrhoeae (GC)
• adults
  
  • Staph aureus
  • others: Gram-neg bacilli, Strep pneumo, Group B, C, and G strep

O:

• monoarticular 90% (knee)
• fever (60-90%)
• palpable joint effusion
• joint motion ltd, painful
• increase in pain w/ joint extension is common
• warmth, swelling, and tenderness over joint
• synovial fluid exam:
  
  • often purulent
  • leukocyte count high
  • differential of WBC >75%
  • elevated protein and low glc lvl
  • gram stian = 1/3 are + for organism
  • cx: non-GC cultures are + in 90% and GC<50% are +

Question 7

Gonococcal Arthritis

Answer 7

epidemiology:

• young adults and adolescents
• women during menses/pregnancy

Gonococcal Septic Arthritis

O:

• monoarticular
• synovial cx often +

Disseminated Gonoccoal Infection

O:

• polyarticular
• fever
• chills
• skin rash w/ erythematous papules - pustules (few, scattered)
• joint pains may be ass w/ tenosynovitis (inflamm of tendon sheath) (classic sign)
• blood cx often +
• synovial cx often negative
• GC can be cultured from genital, rectal, and pharyngeal cultures

Question 8

Septic Bursitis

Answer 8

= most commonly infected joints are olecranon bursae and prepatellar bursae \

• distinguished from septic arthritis by PE
  etiology:
• bacteria usually introduced through trauma or accidental percutaneous puncture
• >80% due to Staph species
• Strep, GNRs, mycobacteria

S:

• painful swelling, redness noted by pt
• often ass w/ systemic sxs (fever, chills)

O:

• overlying cutaneous injury often present on PE
• focal warmth, erythema, visible swelling
• joint ROM may be reduced due to pain or edema of extremity
• differentiate from arthritis by extension/flexion of joint - bursa pain worse w/ flexion

A:

• DX made with exam and aspiration of bursa fluid
  
  • inflamm (WBC elevated)
  • Gram stain and cx

P/TX:

• abx tapered to cx or empirically to cover Staph/Strep
• daily aspiration combo w/ abx for best clinical results often required
• some pts require surgical drainage or “bursectomy”
• prolonged abx therapy (2-3 weeks)