Infections of bones, joints, muscles (clinical) - Stillwell

Question 1

nuclear medicine bone scan

-any inflammation looks “hot”

Answer 1

• intense uptake on early and delayed phases –> think osteomyelitis**
• intense uptake on early and less intense delayed –> think cellulitis**

Question 2

ostoemyelitis

Answer 2

• inflammatory process of bone from infection
• organism: Staph aureus most common**

chronic: dead bone, fibrous capsule, inflammatory infiltrates (lymphocytes for chronic, neutrophils for acute), weak bone

Question 3

periostitis

Answer 3

• inflammation of periosteum
• may/may not be infectious
• elevated/thickened periosteum**
• shin splints and trauma are cause

Question 4

sequestrum

Answer 4

• piece of dead/necrotic bone, most often from infection**
• lead to vascular thrombosis and bone ischemia
• no blood vessels –> antibiotics can’t reach

Question 5

involucrum

Answer 5

• layer of new bone growth outside of infected area, surround sequestrum**
• poor, weak bone from periosteum
• in chronic osteomyelitis

Question 6

bone abscess

Answer 6

• purulent material in bone/bone marrow cavity under the periosteum**
• Brodies abscess** –> walled off inefection, end of long bone, resembles osteoid osteoma
• Pott’s puffy tumor** –> subperiosteal abscess of frontal bone due to osteomyelitis, sinusitis, cocaine, brain abscess

Question 7

septic arthritis

Answer 7

• infected joint space with inflammation

- decreased ROM with synovial effusion**

Question 8

aseptic arthritis

Answer 8

• inflammation in joint - may or may not be infectious

- seen in osteoarthritis, autoimmune, gout/pseudogout, or after surgery

Question 9

prosthetic joint infection

Answer 9

-infection of artificial joint, hardware, or surrounding bone

Question 10

synovitis

Answer 10

-inflammation of synovial fluid/membrane –> fluid build up

Question 11

tenosynovitis

Answer 11

• inflamed synovial membranes around tendons (usually flexors)
• fluid filled
• secondary to infection –> Staph. aureus most common**
• also pasteurella, bartonella, eikenella, mycobacteria marinum**
• neisseria gonorrhea from disseminated gonorrhea**

Question 12

septic tendinitis

Answer 12

• infection of tendon

- hard to treat –> avascular –> antibiotics cannot enter site

Question 13

myositis

Answer 13

• inflammation of muscle tissue

- secondary to infection, overuse, autoimmune, meds, trauma

Question 14

polymyositis

Answer 14

• bacterial infection of muscle

- TROPICAL regions***

Question 15

abscess

Answer 15

1. muscle abscess - pus collection within muscle
   - psoas abscess in IV drug users
   - vertebral osteomyelitis can enter psoas
2. interfacial abscess - b/w fascial planes

Question 16

necrotizing fasciitis aka (gangrene, myonecrosis, flesh eating)

Answer 16

• polymicrobial –> synergistic
• rapid spread from fascial planes to muscle/soft tissue
• organisms: Clostridium perfringes; staph aureus and strep** producing exotoxins
• gas in the tissues**
• require debridement (antibiotics fail)

Question 17

osteomyelitis - hematogenous spread

Answer 17

• most common cause in children**
• develops in metaphysis (growth plate) of long bones**
• bone necrosis and infection from the stasis of blood
• in infants, spread to epiphysis causing medullary infection –> form involucrum**
• retained to metaphysis from 1–>puberty
• cortical thickening, less involucrum with aging
• in adults, leads to vertebral osteomyelitis** due to rich blood supply (starts in intervertebral disc) –> Staph aureus most common*; also TB –> Pott’s disease** in spine with Gibbus deformity** with kyphosis and anterior vertebrae collapse); brucellosis** –> spine infections that get worse over time; E. coli and Enterococcus** –> Batson’s plexus –> spine and GU infections**

Question 18

osteomyelitis caused by gram neg. rod (ex. E. coli, enterococcus)**

Answer 18

GYN infection

-check pelvis from GU infection**

Question 19

vertebral osteomyelitis

Answer 19

• starts in disc space and erodes vertebrae**

- lose disc space

Question 20

TB spread to the spine**

Answer 20

• Pott’s disease in vertebral osteomyelitis –> anterior wedging with Gibbus deformity**
• excess kyphosis forms

Question 21

batson’s plexus

Answer 21

how cancers spread from lungs, breast, prostate into spine

Question 22

osteomyelitis - direct inoculation

Answer 22

• mostly from open fractures (ex. ortho surgery)

- direct contact contamination of bone

Question 23

osteomyelitis - contiguous spread

Answer 23

-from infections adjacent to bone that enter (ex. septic arthritis, abscesses, periostitis, chronic ulcers)

Question 24

osteomyelitis pathogens***

Answer 24

1. newborns –> GBS (strep agalactiae)
2. young child –> kingella
3. nail punctures through shoe –> Pseudomonas
4. unvaccinated child –> H. influenza
5. sickle cell/thalassemia –> Salmonella
6. mandible trauma –> actinomyces
7. animal bite –> pasteurella, bartonella, capnocytophaga
8. human bite –> eikenella, strep. viridans
9. systemic yeast –> histo/blasto/coccidoidomycosis and cryptococcus
10. implanted hardware –> staph. coagulase neg., propionibacterium
11. old and foreign country –> TB
12. immunosuppression –> Pseudomonas, nocardia

Question 25

osteomyelitis pathology

Answer 25

• acute –> neutrophils infiltrate 1st –> bone necrosis
• lymphocytes recruited 2nd
• chronic –> dead bone forms sequestrum (poor penetration of antibiotics) due to body trying to wall area off
• chronic: risks to develop SCC due to sinus tracts**

Question 26

osteomyelitis diagnosis

Answer 26

1. physical: probe to bone test –> osteomyelitis if can tap bone with Q tip
2. lab tests: always high ESR and CRP, rather obtain bone biopsy than wound cultures (wound pathogen may not be correlated with infection), stop antibiotics 1-2 weeks before biopsy and send bone off for gram stain
3. X ray - initial test for bone disease**; must lose 50% of matrix to show up (usually neg. in 1st 1-2 weeks of osteomyelitis)
4. sinography/fistulagrams - inject dye into sinus tract then look at CT/Xray to see if it reaches bone
5. nuclear medicine - not good bc WBCs light up with inflammation
6. CT scan - better for looking at bone margins
7. MRI - best for looking at surround soft tissue (can use contrast); diagnostic modality for osteomyelitis**

Question 27

specific types of osteomyelitis

Answer 27

1. diabetic foot infection - neurophathies and vascular diseases
   - charcot feet** –> bone shifts
   - develop ulcers, decreased immune system
   - polymicrobial –> aerobic and anaerobic** –> Staph. aureus and strep from normal flora** and pseudomonas in shoes***
2. osteitis pubis - infection of pubic bones after OB-GYN surgery
3. sternal osteomyelitis - usually after cardiac procedures (ex. coronary bypass)**
   - infections due to staph. aureus and staph coagulase neg. species**
   - need prolonged antibiotics and debridement
4. sacral osteomyelitis - debilitated patients (para/quadriplegics)
   - bed ridden –> develop ulcers
   - need prolonged antibiotics and debridement

Question 28

treatment for osteomyelitis

Answer 28

1. debridement - I&D; antibiotics may not be able to get there
   - remove hardware or bacteria will be stuck to slime layers/biofilms on surface***
2. antibiotics - usually 4-6 weeks
   - emperic therapy** (guessing at what pathogen might be) –> broad spectrum usually
   - usually given IV to get into bone vessels easier
3. aggressive wound care
4. vascular eval - ex. bypass or stents if needed
5. antibiotic beads in wound spaces
6. hyperbaric oxygen

Question 29

antibiotic organism targets (pathogen directed therapy)

Answer 29

1. MRSA –> vancomycin, daptomycin, linezolid, ceftroline
2. MSSA –> nafcillin, oxacillin, cefazolin
3. salmonella –> Cipro/levofloxacin
4. Pseudomonas –> ceftazimide
5. strep (group A, B, C, F, G) –> all the cillins

for routine osteomyelitis, mixed aerobic/anaerobic infections, and vertebral osteomyelitis –> vancomycin and daptomycin
-add rifampin if infected, unremovable hardware –> penetrates biofilm

Question 30

septic arthritis

Answer 30

• joint infection due to hematogenous (most common) or contiguous spread or direct inoculation
• induration, heat, and pain around the joint
• loss of joint ROM with effusion (synovial build up)**
• hematogenous spread –> knees>hip>should>wrist>elbow
• direct inoculation –> hands, feet
• differential: many other things look like septic arthritis (ex. inflammatory arthritis, autoimmune, etc.)
• degradation of synovial membrane w/I 48 hours (treat ASAP)** –> synovitis starts and panus develops
• risk groups: IV drug users, RA (highest risk)**, immunosuppressed, diabetes, steroids, endocarditis, EtOH

Question 31

septic arthritis bacterial causes**

Answer 31

• staph aureus most common**
• N. gonorrhea and strep (#2 cause)**
• spirochetes in Lyme disease/syphilis*
• disseminated gonococcal infection (DGI) in sexually active adults under 40*** –> associated with tenosynovitis, polyarthritis, rash, pustules

Question 32

septic arthritis viral causes

Answer 32

• not as common, but can happen
• Parvovirus B19, Hepatitis B/C/E, Rubella, HIV and Chikungunya virus for inflammatory arthritis
• Chikungunya and parvo mimic RA**

Question 33

other bacterial causes of septic arthritis*****

Answer 33

1. H. influenza –> unvaccinated child
2. kingella kingae –> child 2 months - 2 years; found in normal flora
3. GBS and staph aureus –> neonates
4. staph aureus and staph coagulase neg. –> prostheticsE. *Staph. aureus- after penetrating trauma.
   F. *Eikenella and Strep. viridans- after human bites.
   G. *Pasteurella, Bartonella and Capnocytophaga- after animal bites.
   H. *Pseudomonas aeruginosa- after nail punctures through shoes and in snake bites.
   I. *Spirillum minus and Streptobacillus moniliformis- in rat bites (the two causes of rat bite fever)

Question 34

disseminated gonoccocal Infection (DGI)**

Answer 34

• most common cause of septic arthritis in sexually active under 40**
• 3x more common in women due to period**
• problems in those with terminal compliment pathway deficiency*

Question 35

septic arthritis diagnosis

Answer 35

1. blood tests - always high ESR/CRP***
2. joint/synovial fluid studies - arthrocentesis
   - fluid less viscous with inflammatory processes (no string sign and is cloudy)
   - bacterial arthritis: elevated LDH and WBCs (neutrophils) usually
   - fungal/mycobacterial arthritis: autoimmune diseases like gout, pseudo gout
3. synovial tissue studies - synovial biopsy
4. blood cultures may/may not be positive

Question 36

agar for N. gonorrhea**

Answer 36

Thayer Martin blood agar

Question 37

gout vs. pseudo gout**

Answer 37

• gout –> need-like crystals

- pseudogout –> rhomboid like crystals

Question 38

radiology of septic arthritis

Answer 38

1. x ray - not sensitive
2. nuclear medicine bone scans - nonspecific
3. CT scan - show bone abnormalities
4. MRI - best diagnostic tool**, soft tissue around joint

Question 39

septic arthritis treatment

Answer 39

• viral –> no treatment
• bacterial –> decompression/drainage (arthrocentesis)
• antibiotic coverage to a single pathogen bc that is normally the cause
• use vancomycin (covers staph/strep) and ceftriaxone (covers gram neg rods, H. influenza, N. gonorrhea)

Question 40

specific types of septic arthritis

Answer 40

1. septic prosthetic joint arthritis: infection of prosthetic joints (knees most common)
   - lead to prosthesis loosening
   - due to staph. aureus or staph coagulase neg species**
2. septic sternoclavicular and sternocostal joint arthritis - usually IV drug abusers or infected central line
   - need debridement and longterm antibiotics
3. septic sacroiliac joint arthritis: IV drugs users or from infected sacral ulcer
   - need debridement and longterm antibiotics
4. reactive arthritis: maybe from infection elsewhere or immune related inflammation
   - ex. post-streptococcal arthritis (rheumatic fever), chlamydia STI (Reiter’s syndrome), and GI infections
   - HLA-B27 gene associated**
5. septic bursitis: puncture bursa causing skin flora and other bacteria to enter –> do I&D and antibiotics
   - usually staph aureus***
   - usually prepatellar and olecranon bursae

Question 41

muscle infections

Answer 41

1. causes: hematogenous, direct inoculation, contiguous
2. pathology: myalgia due to myositis from acute phase reactants (IL-1, TNF-alpha) released in host immune rxn
   - pyomyositis if infected by bacteria
3. organism: usually staph aureus and strep species**
   - TB also common cause of muscle abscess
   - can be polymicrobial
4. diagnosis: x ray, ultrasound, nuclear medicine
   - CT and MRI best for looking muscle infection, abscess, and surrounding inflammation**
5. treatment: drainage of abscess or debridement
   - extensive debridement and fasciotomy if necrotizing fasciitis
   - antibiotics always needed

Question 42

pyomyositis

Answer 42

-bacterial infection of muscle - usually from tropical region***