5. • In nature, bacteria exist in mixed-species
communities adherent to a surface.
6. What happens to an implant after
implantation?
• Surface is electrochemically active and proteins
rapidly adsorb onto the surface.
7. Gristina AG: Biomaterial-centered infection: microbial adhesion
versus tissue integration. Science 1987;237:1588-1595
“The Race for the Surface”
• Metal surfaces rapidly
covered with proteins.
• Bacteria attracted by
nutrients concentrated at
implant surfaces
• Stimulated by adhesion to
proliferate and to excrete a
polysaccharide coating.
10. Bacterial Resistance in Biofilms
• Bacteria survive within
biofilms even when exposed
to antibiotic levels 100 -
1000x greater than MIC
• Even sensitive bacteria may
have reduced sensitivity to a
given antibiotic when in a
biofilm.
11. Small Colony Variants (SVC’s)
• Small subpopulations form by differential
gene expression, with reduced growth rate,
increased bacterial resistance.
• “Persister Cell” neither grow nor die in the
presence of antibiotics. Can revert to normal
cells when antibiotics are stopped.
12.
13. • Defect in electron-transport system confers
aminoglycoside resistance and ability to reside
intracellularly.
• Existence can be overwhelmed on routine culture media;
prolonged culturing and genetic phenotyping may be
needed to confirm.
14. Infected Fractures: The Role of
Fracture Stability.
• The presence of a foreign-body increases the risk
of infection.
• Experience suggests that internal fixation of open
fractures reduces the infection rate.
?
15. • Rabbit model
• Tibia fractures were stabilized with either a
dynamic compression plate (stable group) or a
loose intramedullary rod (unstable group), and
inoculated with S. aureus.
• The infection rate was double in the unstable
group (71% versus 35%).
Melcher GA, et al. Infection after intramedullary nailing: an
experimental investigation on rabbits. Injury 1996;27(Suppl
3):S-C23–S-C26.
16. Why?
• Internal fixation reduces ongoing soft tissue
damage caused by fx instability
– Promotes vascular invasion & improves
microcirculation.
– Stable surface more likely to be covered with host
tissues.
– Makes the wound a less hospitable environment for
bacterial growth.
18. These signs/symptoms are often
not present in orthopedic infections
• Systemic signs absent
• WBC often normal
• In early postop infections,
xrays normal
20. Traditional imaging studies are nonspecific
• Periosteal new bone,
demineralization, or a
sequestrum may be seen
in chronic infections.
• Indium scans and MRI
may also be useful, but
are infrequently
diagnostic.
21. Laboratory studies
• Elevations in total leukocyte count, ESR, or
C-reactive protein.
• A rising CRP after 48 hours is predictive of
a septic complication.
22. • CRP > 96 mg/L after
the 4th day predictive
of sepsis
32. Factors to consider:
• Health of host
• Extent of bone healing
• Soft tissue integrity
• Duration symptoms
• Organisms
• Implant
33. Infections before Fracture Union
• Treatment depends on maintaining stability
but this must be balanced against possible
need to remove colonized hardware.
34. Acute infection following operative fracture
treatment: is the removal of implants
mandatory?
• Goals:
– Eradication of infection
– Maintenance of internal fixation, if possible.
• Protocol:
– Repeated debridement every 48 hours, with local and
systemic antibiotic therapy.
– Wound must be bacteriologically clean after 4
surgeries.
– If not, the implant was removed.
Hofman et al, Chirurg 1997
35. Results
• 34 Cases
• Infection eradicated in all patients.
• 11 cases successfully treated without
implant removal.
• In 23 cases implant removal was necessary.
Hofman et al, Chirurg 1997
37. • 123 patients with infections within 6 weeks of internal fixation.
• 71% achieved union with debridement, retention of hardware,
and prolonged antibiotic suppression.
– Of these, 36% had recurrence after union and had later hardware removal,
with resolution
38. • Predictors of failure:
– Open fracture
– IM nail
• Multiple comorbidities/diabetes associated
with a higher rate of success ???
44. • Nail removed at 6 – 76 weeks
• Reaming cultures negative at nail removal in 18/19 cases
– 1 failure could not complete Rx due to abx intolerance.
50. Summary
• Knowledge of the pathophysiology of implant-related
infections leads to a logical approach for management.
– Skeletal stability must be maintained
– Antibiotic therapy and debridement are the
cornerstones of treatment.
51. • In acute infections with favorable soft-tissues, the
implant may be successfully retained as long as
fracture union seems to be progressing favorably.
• If exchange of implant is necessary, consider a
“hardware holiday”, but don’t forget about
stability.
52. “… there is only one thing worse than a
stable infected fracture and that is an
unstable infected fracture”.
McNeur JBJS 52B: 54-60, 1970
