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Musculoskeletal System II > 12- Infection > Flashcards

12- Infection Flashcards

1
Q

What are the 3 broad categories of orthopedic infections?

A
  • Infection of the Joint (Septic Arthritis)
  • Infection of the Bone (Osteomyelitis)
  • Soft tissue or bone infection adjacent to a surgical implant or joint prosthesis
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2
Q

Why does the blood supple to the bone and joint tissue make infections different than the rest of the body?

A

supply to bone and joint tissue is not as rich as other parts of the body –> less bacteria can get into the skeletal tissue but harder to rid if it does get there

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3
Q

What is the role of mechanical function in orthopedic infections?

A

predicted on the precise geometry of the adjacent bones and cartilage surfaces

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4
Q

The frequent use of what devices increases the risk of infections?

A

surgical implants

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5
Q

What is septic arthritis?

A

infection and inflammation of a joint caused by bacterial, fungal, or viral invasion of the synovium.

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6
Q

Does septic arthritis typically involve 1 joint or multiple?

A

90% of the time only 1

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7
Q

What is the most commonly affected joint in septic arthrtis?

A

knee > hip, shoulder, ankle and wrist

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8
Q

What are the acute signs of septic arthritis?

A

Acute swelling and warmth around the joint, effusion, tenderness to palpation and extreme pain with minimal range of motion.

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9
Q

What are the 4 most common ways bacteria can reach the joint?

A
  • From the blood – hematogenous seeding during bacteremia
  • Direct inoculation from outside environment – due to trauma or surgery
  • From the localized spread of a nearby soft tissue infection
  • From the spread of a bone infection near the joint – particularly osteomyelitis
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10
Q

What are the risk factors for septic arthrtis?

A

history of rheumatoid arthritis or IV drug use.

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11
Q

RA typically has an infection where?

A

RA patient more likely to have multiple joints involved

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12
Q

IV drug users typically has an infection where?

A

Intravenous drug users often have infections in atypical joints like sternoclavicular, sacroiliac and manubriosternal joints.

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13
Q

What is the most common culprit to joint infections?

A

Staph Aureus

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14
Q

I have a good feeling

A

my fingers are going to bleed when these flashcards are through

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15
Q

How can bacteria seed from the synovial capillaries?

A

Hematogenous septic arthritis occurs when bacteria are able to seed the joint after escaping from the synovial capillaries, which do not have a basement membrane.

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16
Q

What is special about staph aureus that makes it the most common culprit to septic arthritis?

A

Staphylococcus Aureus has an increased ability to bind to articular cartilage

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17
Q

What is the major cause of joint destruction in septic arthritis?

A

neutrophilic immune response

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18
Q

What is the neutrophilic immune response?

A

Begins within 48 hours and as a result of the release of proteases and cytokines from inflammatory cells, and an increase in intra-articular pressure

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19
Q

What % of all cases of septic arthritis is caused by Staph aureus?

A

60%

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20
Q

Besides S. aureus, what other bacteria can cause septic arthritis?

A

Streptococci and gram negative organisms.

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21
Q

What bacteria are often the culprit in septic arthritis in IV drug users?

A

In IV drug abusers, gram-negative bacteria are most likely. Pseudomonas is especially prevalent.

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22
Q

What are the most common culprits of septic arthritis in children from birth-6wks old?

A

Strep Pneumo, E. Coli and N. Gonorrhea (via maternal transmission)

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23
Q

What are the most common culprits of septic arthritis in children <5 years old?

A

Kingella Kingae, H influenza, Strep Pneumo

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24
Q

What are the most common culprits of septic arthritis in children >5 years old?

A

Staph Aureus, Strep Pneumo

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25
Q

What is the difference between disseminated and septic gononococcal infections?

A

Disseminated gonococcal infections are classically associated with fever, chills, rash and migratory arthritis of the large joints.
Gonococcal Septic Arthritis normally involves a single joint

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26
Q

Give a classical clinical presntation of a pt with septic arthritis

A

Old, nursing home resident being treated with corticosteroids and methotrexate for RA. Knee pain for the last 2 days with minor trauma. Temp is elevated to 100 degrees F. Large warm effusion on knee that is tender to palpation, Extreme pain with minimal range of motion. Weight bearing is painful. Skin infection is common.

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27
Q

What typically shows up on radiographs for septic arthritis?

A

Radiographs typically show soft-tissue swelling and periarticular osteopenia consistent with long term RA

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28
Q

What test is needed in hip infections are suspected because they can detect an effusion with great sensitivity?

A

ultrasound or MRI

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29
Q

What lab test can you do to Dx infections?

A

analysis of fluid obtained from joint aspiration that is used for WBC count

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30
Q

What WBC count do you need to be indicative of an infection?

A

50,000 Cells/mm3

Seriously, this is the 3rd time this objective came up so far. If it’s not a test question, I don’t know what I’m doing with my life.

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31
Q

What is the differential Dx to septic arthritis?

A

inflammatory arthritis, reactive arthritis, trauma, superficial infection or abscess near but not in the joint, and collagen vascular disorders.

32
Q

What are the goals for treating septic arthritis?

A

sterilization of the joint, removal of inflammatory cells and their enzymes, elimination of destructive synovial pannus, and restoration of function

33
Q

How can you achieve these goals?

A

Meditation, 4-7-8 breathing techniques, acupuncture, osteopathy in the cranial fields and Star Wars emperor shock therapy

Oh wait, it isn’t Wednesday morning. Antibiotics and arthrocentesis treat septic arthritis.

34
Q

How can you drain an infected joint?

A
  • Repeated needle aspirations
  • Arthroscopic lavage
  • Arthrotomy (open surgery)
35
Q

When do you need to drain an infected joint?

A

If repeated aspirations are attempted and systemic antibiotics are administered, failure to improve within 48 hours is an indication for surgical drainage.

36
Q

What should to do post-op after draining a joint?

A

Splint that mofo (but not for too long)

37
Q

How do you manage gonococcal infection?

A

Gonococcal septic arthritis may not need surgical drainage. IV ceftriaxone and aspiration may be sufficient. Once there is clear improvement, oral antibiotics can be given for 14 days

38
Q

What is osteomyelitis?

A

infection of the bone and marrow

39
Q

Where is the most common location of adult osteomyelitis?

A

distal tibia

40
Q

What is the most common way of bacterial spread to the bone in children?

A

Hematogenous spread

41
Q

What are the Sy/Sx of osteomyelitis in children?

A

Presenting symptoms are listlessness, poor feeding, and pseudoparalysis of the involved limb.

42
Q

What is the most common way of bacterial spread to the bone in adults?

A

Direct inoculation (after trauma/surgery)

43
Q

What is another way of bacterial spread to the bone?

A

extension from adjacent soft-tissue infections

44
Q

What are the risk factors for osteomyelitis development in adults?

A

History of prior open fracture, immune compromise, IV drug use, and blood disorders such as hemophilia and sickle cell disease. Osteomyelitis may also be found on the feet of patients with diabetes, vascular insufficiency, and prior puncture wounds through shoes.

45
Q

What is a bone infarction?

A

ischemic death of the bone; occurs because the endosteal blood supply is blocked by thrombosis and the superficial blood supply is diverted as the periosteum is elevated off the bone.

46
Q

What is the sequestrium of the bone infarction?

A

area of necrotic bone

47
Q

What is the involcrum of the bone infarction?

A

new bone that forms over the sequestrum; produced by the periosteum

48
Q

Which bacteria is most common in all age categories for osteomyelitis?

A

YOU GUESSED IT- Staph aureus

49
Q

Which bacteria is most common in neonates for osteomyelitis?

A

group B Strep and gram negatives

50
Q

Which bacteria is most common in sickle cell pt’s for osteomyelitis?

A

salmonella

51
Q

Why does the metaphyseal vessels cause an increase risk of spread to the epiphysis in neonates rather than in older children?

A

In a neonate, the metaphyseal vessels penetrate directly into the chondroepiphysis, allowing an infection in the metaphysis to readily invade and destroy the chondroepiphysis and subsequently invade the joint.

In an older child, the physis serves as a mechanical barrier to the spread of infection.

52
Q

Why does bacteria invade during post-traumatic osteomyelitis?

A

Posttraumatic osteomyelitis occurs because the combination of clotted blood, dead space, and injured soft tissue provides an ideal medium for bacterial growth

53
Q

What is the most common bacteria for post-traumatic osteomyelitis?

A

S. aureus

54
Q

What are the Sx of osteomyelitis in kids?

A

A typical presentation in a child would include a short history of pain in the affected area. Most young children will not seem very sick, however infants with bone infections may have a toxic appearance. Usually the child refuses to bear weight on the extremity, has a fever, and will have tenderness over the bone with or without erythema or effusion. The child may also have pain with movement of the joint, but can still typically demonstrate full range of motion

55
Q

What are the Sx of osteomyelitis in adults?

A

Physical exam will reveal tenderness over the site but no erythema, skin breakdown or sinus tracts. The WBC and erythrocyte counts would be normal, C reactive protein would be slightly elevated. No fever or chills. History of trauma or surgery is a big indicator of osteomyelitis.

56
Q

What is the treatment regimen for osteomyelitis?

A

Treatment is IV antibiotics for a short time (typically 5-10 days) then the use of oral antibiotics for 3 weeks

57
Q

When do you need surgical debridement?

A
  • When pus is obtained on initial aspiration
  • When there is radiographic evidence of a metaphyseal sequestrum
  • When there is no clinical improvement within 24-48 hours of antibiotic therapy
58
Q

When do you need an indium-III scan when a prosthesis is expected to be infected?

A

An indium-111 white blood cell scan shows areas of high uptake around the prosthesis in a patient with an infected prosthesis.

59
Q

What can you do for an elderly pt who has osteomyelitis but cannot undergo surgery?

A

The effects of the multiple procedures required to eliminate infection and restore skeletal integrity may be more detrimental than the disease itself. In these cases, intermittent courses of antibiotics can be used to suppress exacerbations as needed.

60
Q

What are periprosthetic infections?

A

Periprosthetic Infections are a combination of septic arthritis and osteomyelitis. The infection involves not only the joint but also the adjacent bones in which the prostheses have been implanted.

61
Q

Periprosthetic infections have a rate of occurrences in the USA at what %?

A

1%

62
Q

How can you prevent periprosthetic infections?

A

prophylactic antibiotics should be used before all orthopedic surgical procedures, especially those that involve the implantation of foreign material.

63
Q

What is the Tx regimen for periprosthetic infections if the case occurs <4 wks post-op?

A

treatment consists of irrigation and debridement followed by 4 weeks of antibiotic therapy.

64
Q

What is the Tx regimen for periprosthetic infections if the case occurs >4 wks post-op?

A

the prosthesis must be removed and the patient must be treated with IV antibiotics. 2 weeks after the antibiotic therapy, the joint should be reaspirated, and if it’s sterile, new prosthesis can be considered. Positive cultures require further debridement and antibiotic therapy.

65
Q

Which organisms can cause osteomyelitis in an immunocompromised host?

A

Immunocompromised hosts are at risk for septic arthritis and osteomyelitis caused by atypical mycobacteria and fungi. Common mycobacteria found in this patient population are Mycobacterium Kansaii and Mycobacterium Avium-Intracellulare. Fungal infections are Candida species, Cryptococcus and Aspergillus.

66
Q

Which organism causes TB?

A

Mycobacterium Tuberculosis

67
Q

Where does skeletal TB often spread?

A

It spreads from the lungs to the large weight bearing joints and the spine. Spinal tuberculosis is called Pott’s disease.

68
Q

Which organism causes Lyme disease?

A

Borrelia Burgdorferi

69
Q

What is the transmisison of Borrelia Burgdorferi?

A

Transmitted to humans via the bite of deer ticks.

70
Q

What are the Sx and Tx of stage 1 lyme disease?

A

Localized lesions appear on the skin. Treated with 14-21 days of doxycycline.

71
Q

What are the Sx and Tx of stage 2 lyme disease?

A

Disseminated infection occurs, following the first stage by days to weeks. Migratory pain without swelling of the articular and periarticular surfaces. Treated with 14-21 days of doxycycline.

72
Q

What are the Sx and Tx of stage 3 lyme disease?

A

Late or persistent infection occurs. Treated with 30 days of doxycycline or IV ceftriaxone.

73
Q

What is the frequency of diabetic foot infections in hospitalized patients?

A

Approximately 25% of all hospitalizations associated with diabetes mellitus occur for the treatment of foot infections.

74
Q

What are the factors for diabetics to develop foot infections?

A
  • Diabetics are more likely to injure their feet because they often have decreased sensation from peripheral neuropathy.
  • Diabetes causes peripheral vascular disease which causes poor wound healing
  • Diabetics typically have impaired vision which increases the risk of injury and prevents full appreciation of the extent of injury
  • Once infected, impaired immunity due to slow blood flow makes eradication of foot infections extremely difficult
75
Q

What are the organisms involved in diabetic foot infections?

A

Infections tend to be polymicrobial, involving both aerobic and anaerobic organisms including Pseudomonas.

Musculoskeletal System II (24 decks)

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