Epidemiology on Orthopedic Infections

University:
The University Of Western Ontario
Course:
Biology 2290F | Scientific Method in Biology
Academic year:

2022
Views:

107

Pages:

3
Author:

Kyuwon J.

Epidemiology on Orthopedic infections Incidence ● Post fracture fixation infection ○ 1~2% closed fractures ○ 10~30% in open fractures ○ prosthetic joint infections (PJI) ■ 1-2% after primary arthroplasty ■ may be higher if revision cases Burden ○ Lead to prolonged hospitalization ○ multiple surgeries ○ functionality losses ○ Have possibility on progressing it into chronic osteomyelitis once not controlled Pathophysiology on Bones ● Bone environments ○ poor vascularity in necrotic bones => antibiotics are poorly penetrated ○ sequestrum serves in nidus for bacteria ■ dead bone fragments ■ Necrotic bones lack in vascular structure seen in histology image ■ Antibiotics are not able to reach into deeper bones, no way for body to respond to infections ● Biofilm formations ○ Bacteria forms biofilms (attack on implants) ■ Staphylococcus aureus ■ Staph ■ Epidermidis ■ Pseudomonas ○ These bacteria of biofilms are more likely to be resistant to antibiotics compared to planktonic forms ● Host immune limitations ○ inflammatory cell will have no/less access to devascularized area ○ systemic therapy ■ insufficient ■ need surgical debridement Limitations of Systemic Antibiotics ● High doses of bone penetration needed ● increase in system toxicity ○ renal ○ hepatic ○ ototoxics ● Aminoglycosides + Vancomycin could be effective ○ toxic once given systemically ● local delivery is crucial to bypass limitations Rationale on Local Antibiotic Delivery ● Advantage over systemic therapy ○ high local concentrations ■ Increased concentration than achievable in blood ■ avoiding systemic toxicity ■ maintaining antibiotic levels in infected cavity ■ dead space treated within weeks ○ Target infection site directly Development on antibiotic beads ● First used in 1970s ○ PMMA mixed with gentamicin ○ molded into shape of beads ○ place beads in debris cavity => elutation of antibiotic gradually over period of time Mechanisms ● Elution kinetics ○ initial burst release => very high antibiotics ○ Gradual tapering ■ release lasting upto 4 weeks ● Drug stability ○ must be heat stable antibiotics ○ PMMA curing generates over 80C ● Coverages ○ chosen to target Staph aureus ○ most common cause of bone infections