Osteomyelitis

Question 1

What are the classifications for osteomyelitis?

Answer 1

Hematogenous or post-traumatic. Post-traumatic can be further subdivided into acute, subacute or chronic.

Question 2

What does the successful treatment of osteomyelitis depend on?

Answer 2

The viability and stability of bone, the virulence of the pathogen, state or condition of the soft tissue envelope

Question 3

What is the most common type of osteomyelitis?

Answer 3

Bacterial

Question 4

What is the most common organism implicated with bacterial osteomyelitis?

Answer 4

Staph pseud (multi resistant in up to 50% of cases), followed by E.coli and strep.

Question 5

How does the radiographic appearance of aggressive bacterial osteomyelitis differ from less aggressive forms?

Answer 5

Less aggressive: slowly separates the periosteum leading to smooth thickening.
Aggressive: new lamellar bone is deposited, this is often perpendicular to the periosteum

Question 6

What are the benefits of biofilm formation to bacteria?

Answer 6

ECM concentrates and captures nutrients, provides protection from shear stress, from phagocytic activities, and from protease and oxygen free radicals, acts as a barrier to antimicrobial agents, and alters the extracellular environment limiting efficacy (pH, partial pressure of O2, CO2 etc). The altered growth pattern of bacteria (quiescent) also limits antimicrobial efficacy.

Question 7

What is the conditioning layer in biofilm formation?

Answer 7

A layer of proteins and polysaccharide molecules from the host that are adsorbed onto an implant. This allows bacteria to adhere to the implant via fibronectin.

Question 8

What is the most common location of hematogenous osteomyelitis?

Answer 8

Metaphyseal regions of the bone. Potential reasons include capillaries lacking a basement membrane, sluggish blood flow +/- minor trauma.

Question 9

Is hematogenous osteomyelitis more common in adult or juvenile patient?

Answer 9

Juvenile

Question 10

What is an involucrum?

Answer 10

An area of live encasing bone that surrounds dead bone

Question 11

What are some radiographic changes associated with post-traumatic osteomyelitis?

Answer 11

Cortical resorption, periosteal proliferation, loss of trabecular markings +/- sequestrum and involucrum

Question 12

What are some radiographic changes associated with hematogenous osteomyelitis?

Answer 12

Polyostic lesions in the metaphysis of long bones +/- those signs seen for posttraumatic osteomyelitis

Question 13

With the use of antimicrobial beads how much higher are concentrations than with systemic administration?

Answer 13

500 times. Normally use heat stable hydrophilic agents with activity against staph (aminoglycosides, vancomycin)