Ch 47 Osteomyelitis and implant-infections Flashcards
(68 cards)
1
Q
Osteomyelitis
A
- inflammatory condition of bone, is usually considered to be caused by an infectious agent (bacteria, fungi, or viruses)
- Under normal physiologic conditions, bone is resistant to colonization and subsequent infection
- an inciting event must occur to lead to the development of osteomyelitis > Trauma, the implantation of foreign material (implants), inoculation with infectious organisms, and/or an immunocompromised patient
- osteomyelitis > classified as hematogenous or posttraumatic
2
Q
Waldvogel staging system
A
based on the cause of the infection (hematogenous spread vs. direct inoculation or contiguous spread from soft tissues)
3
Q
- acute osteomyelitis = infections that occur within days to weeks of the inciting event
- chronic = develop over months or years with key characteristics of low-grade inflammation, persistence of microorganisms, and the presence of sequestrum and fistulous tracts.40
A
4
Q
treatment success influenced by three central factors
A
(1) viability and stability of the bone
(2) virulence and antimicrobial susceptibility of the organism
(3) condition of the soft tissue envelope
5
Q
variables that can determine whether or not an infection develops (3)
A
The presence of virulence characteristics (i.e., different adhesins, production of toxins)
antimicrobial susceptibility patterns
propensity to form a biofilm
6
Q
most common bacteria
A
Staphylococcus spp. (approximately 60% cases)
E.coli
Streptococcus
Polymicrobial infections > one retrospective study identifying mixed populations in 42% of cases
Staphylococcus intermedius as most common, whereas recent reports suggest S. pseudintermedius is more common
7
Q
other bacteria
A
- in some cases methicillin-resistant strains represent close to 50% of the bacteria being isolated > reflects the outcomes of phylogenetic reclassification
- Gram-negative: Pasteurella, Pseudomonas, Proteus and Klebsiella
- Gram-positive: Corynebacterium spp, enterococci
- Anaerobic: Bacteroides, Nocardia, Clostridium, Actinomyces, Fusobacterium isolated from 64% of cases in one retrospective study
- Fungal:Blastomyces, Aspergillus, Candida, Coccidioides
8
Q
Pathogenesis
A
- Posttraumatic/direct inoculation is thought to be the most common in dogs and cats.
- Hematogenous occur most frequently in young animals.
- Rarely, osteomyelitis the result of direct spread from an adjacent soft tissue infection.
9
Q
Describe the pathogenesis of osteomyelitis
A
- Cytokines and growth factors are found in altered local concentrations during infection
- Normal osteoclast and osteoblast activity is influenced by cytokines/GF > Contribute to necrosis and resorption of the bone
- Leads to ischaemia due to collapse of vascular channels (Haversian, volksman and canaliculi)
- Segments of bone lacking an adequate blood supply have a propensity to form sequestra and offer a protected environment for bacterial organisms > presence of bone ischemia alone is enough
- At the edge of the ischemic bone is a reactive hyperaemia > increase in osteoclastic resorption > development of osteoporosis
10
Q
How is the degree of periosteitis correlated with the aggressiveness of the infection
A
- osteoblastic production of new bone occurs secondary to periosteal irritation: The degree of periostitis correlated to the aggressiveness of the infection.
- less aggressive > slowly separates the periosteum from the bone, resulting in thickening of the cortex
- more aggressive > lamellar changes where layers of bone are laid down adjacent to one another
11
Q
Posttraumatic Osteomyelitis
when microbial organisms are inoculated into areas adjacent to bone: penetrating wounds (FB, bite wound), spread from local soft tissue, or from surgical wounds i.e. implant
A
- bacterial-host interactions are complex and multifactorial, many variables if infection
- Host defense mechanisms (competent immune response) are critical in the prevention
>not every colonized implant result in infection
Competent host defence can be hampered by tissue trauma, (surgical or trauma) > vascular compromise and tissue ischemia
- tissue trauma is central in the development of posttraumatic osteomyelitis
- Data from human > tissue trauma may occur at the cellular level.
- Study:
inflammatory cells (neutrophils) collected from intraop lavage fluid. Analysis demonstrated that although activated, they were unable to clear the bacteria, presumably because of biofilm formation.
During activation and attempted phagocytosis of the bacteria within the biofilm, neutrophils release cytotoxic and proteolytic substances > contribute to tissue injury and osteolysis
12
Q
osetomyelitis: patient and bacterial factors?
A
- patient factors:
presence of sepsis
systemic trauma
major organ dysfunction - bacterial characteristics:
virulence (i.e., different adhesins, production of toxins)
antimicrobial sensitivity patterns
biofilm
13
Q
Dogs with pre-op TPLO nasal/rectal swabs which isolated methicillin resistant sS.Pseud were….
A
13-14 times more likely to develop a SSI cause by the rganism within 30 days
14
Q
Implant-Associated Infections
A
- many have a nosocomial origin with some degree of antimicrobial resistance
- attributable to the presence of biofilms > more resistant to antimicrobial therapy compared to their free-floating, or planktonic, counterparts
- Implant-associated infections and osteomyelitis classified as deep or organ/space surgical site infection
- The presence of an implant +/- procedure performed for implant application can result in the development of osteomyelitis.
- trauma can lead to bone necrosis > predispose to bacterial colonization and biofilm formation within the necrotic bone.
15
Q
most common sx site infection
A
- Recent studies document S. pseudintermedius as the predominant isolate associated with surgical site infections in dogs
- methicillin-resistant strains represent close to 50%
- nosocomial origin is supported by Nazarali et al
16
Q
presence of implant
A
- implant is present > conditioning layer of proteins and polysaccharide molecules adsorbed to the implant surface develops
- bacterial adhesion can occur via fibronectin within the conditioning film and bacterial adhesins
- Successful treatment of an implant-associated infection is influenced by the presence or absence of a biofilm
17
Q
bioflim
concept > was proposed by Costerton 1978
A
- a microbially derived sessile community
- cells are irreversibly attached
- are embedded in a matrix they have produced called glycocalyx, a slimy exopolysaccharide material.
- exhibit an altered phenotype: growth rate and gene transcription
The development dependent on bacterial, substrate, and host factors
- initiated by the reversible adherence of planktonic organisms
- complex molecular pathways and genetic regulation are responsible for biofilm formation.
» importance of quorum sensing, the ability of bacteria to coordinate gene expression based on population density by monitoring the concentration of autoinducers
- also important in the production of virulence factors (e.g., exotoxins).
- S. aureus interactions with receptors of innate immunity alter the bone remodelling activities of osteoblasts and osteoclasts
18
Q
quorum sensing,
A
the ability of bacteria to coordinate gene expression based on population density by monitoring the concentration of autoinducers
19
Q
five main phases involved in the biofilm formation
A
reversible attachment,
irreversible attachment,
EPS production,
maturation of biofilm
dispersal/detachment
20
Q
Biofilm documented advantages
tolerance to antibiotic therapy, and resistance to host defences, contribute to the high rate of treatment failure in osteomyelitis
A
- extracellular matrix > capture and concentrate nutrients required to survive.
- Growth within the matrix provides protection from:
shear stresses
host phagocytic activities
host protease and oxygen radical defenses - Resistance to antimicrobial therapy >genotypic and phenotypic alterations cause quiescent growth pattern.
- resistance is mediated through:
low metabolic levels
radically downregulated rates of cell division - antimicrobial agents rely on bacterial growth > efficacy is diminished
- extracellular matrix itself acts as a diffusion barrier to slow down the infiltration of some antimicrobial agents, leading to an increase in minimum inhibitory concentration (MIC) of up to 100-fold in most cases
- changes to the microenvironment caues changes in hydration level, hypoxia, and lower pH
- protects bacteria from host defences (phagocytosis, reduce proinflammatory immune responses)
21
Q
Hematogenous Osteomyelitis
A
- generally caused by a single bacterial species introduced via the bloodstream and localized to a distant site
- predominantly affecting young, whereby direct seeding of bone occurs during an episode of bacteremia.
- exact mechanism of hematogenous osteomyelitis is not clear, there are a number of theories.
- commonly affects the metaphyseal regions of long bones
- Unopposed infection in the metaphyseal region can spread However, transphyseal vessels are lacking at birth in dogs and cats, thus restricting the infection to the metaphyseal side of the physeal plate
22
Q
proposed mechanisms (4)
for haematogenous osteo
A
- attributed to the anatomy > capillaries are characterized by an incomplete basement membrane > mechanism for bacterial translocation during bacteraemia, allowing the bacteria to localize in an area that is relatively inaccessible to the host inflammatory cells
- sluggish blood flow within the metaphyseal capillaries allows bacteria to settle and initiate colonization (not supported by any published data.)
- Alterations in the host immune response have also been implicated.
Experimental studies in mice > Staphylococcus aureus infection may alter the immune response via downregulation of T-cell immunity and immunocytokine production, thus increasing the severity of local osseous destruction - Minor trauma likely plays a role> In experimental studies involving model in rabbits> hematoma, resulting in vascular obstruction and bone necrosis, which creates an ideal site for bacterial colonization
23
Q
post-truamatic: CS
A
- acute
Erythema, swelling, localized pain
A fever
systemic WBC elevated,
animal is systemically ill
Signs within a few days of the traumatic event and are often difficult to differentiate from a soft tissue/wound infection - Chronic
most have no systemic clinical signs, history of surgery/implant or other traumatic event.
new or worsening lameness
draining tracts are noted
24
Q
post-truamatic: Dx rads
A
Radiographic evaluation
-variable.
- sensitivity 62.5% and specificity 57%
- Initial > soft tissue swelling
- cortical resorption, periosteal proliferation, and loss of trabecular markings.
- lucency around surgical implants
- involucrum = area of live, encasing bone that surrounds dead bone (sequestrum) within a compromised soft tissue envelope
- A nonviable piece of bone that has lost its blood supply is called a sequestrum (can be sterile or infected)
- draining tract develops from the radiolucent area of necrosis that surrounds the sequestrum and extends to the skin surface.
25
describe this
- A sharply marginated sclerotic piece of bone (sequestrum) surrounded by a radiolucent zone that separates it from the parent bone, both of which are surrounded by sclerotic bone (involucrum).
26
post-truamatic: Dx u/s
Ultrasonography
- detecting radiolucent foreign bodies (e.g., plant material) in soft tissues adjacent to an area of osteomyelitis
- detecting abscess formation
- evaluation of draining tracts that may be associated with a surgical implant.
27
post-truamatic: Dx CT/MRI
- (CT) and (MRI)
- useful in identifying sequestra and foreign material
- limited use in the presence of a metallic implant.
- positron emission tomography (PET), and nuclear scintigraphy (technetium-99m)
- intravenous administration of ultrasmall superparamagnetic iron oxide nanoparticles during MRI has shown potential for early detection of vertebral osteomyelitis.
28
post-truamatic: Dx C&S
- gold standard = positive microbial culture
- collected with care (representative and handled appropriately)
- percutaneous aspirates may deliver positive results, interpret with caution because contamination by surface bacteria
- Image-guided collection of samples is advised (needle biopsy)
- cytologic evaluation and Gram stain should be performed
- Aerobic and anaerobic of swabs
- during surgical (necrotic tissue or implant)
- Improvement in sensitivity implants > sonicated
29
reasons for C&S negative
| Incubation should be maintained at least 5-7d before considered negative
Negative culture results
- improper specimen handling or processing
- insufficient specimen volume
- presence of fastidious bacteria: anaerobes, Bartonella, Brucella, Nocardia, or Mycobacterium
- biofilm formation increase false negative
- indications of an anaerobic infection > foul odor, sequestra, or the presence of multiple bacterial species
- fungal infections
(Cultures and cytologic or histologic evaluation of biopsies may be diagnostic in these cases)
30
needle biopsy outcome
sensitivity and specificity using this modality has been reported as 87% and 93%, respectively
31
fastidious bacteria
anaerobes,
Bartonella,
Brucella,
Nocardia,
Mycobacterium
32
What is a rapid molecular technique for the diagnosis of osteomyelitis?
multilocus PCR electrospray ionisation mass spectrometre (PCR/EXI-MS)
91% correctly identified to genus level
74% correctly identified to species level
33
How can you improve the culture and sensitivty results from surgical implants?
Sonication of the implants after retrieval and culturing the sonication fluid
34
Hematogenous Osteomyelitis: CS
- animals are often systemically ill, but a fever is not always present.
- Clinical signs: lameness, inappetance, lethargy, and unthriftiness.
- Metaphyseal regions of long bones may be swollen and painful ddx hypertrophic osteodystrophy
35
Hematogenous Osteomyelitis: bloods and rads,
Blood work
- elevated leukocyte count +/- mild anemia, elevated band neutrophils
- biochemical/urinalysis usually unremarkable
Radiographic
- polyostotic lesions metaphyses of long bones.
- bone resorption, bone lysis, or periosteal new bone formation and also increased medullary opacity
- typically do not extend into the adjacent joint
- Aerobic and anaerobic blood cultures and susceptibility> Sampling the affected area of bone culture and pathologic evaluation
- To rule out joint involvement > arthrocentesis
36
Treatment
Posttraumatic Osteomyelitis
treating acute is to prevent the development of a chronic
- should be aggressive > drainage, debridement, direct bone/tissue culture, and, in some cases, delayed closure.
- debridement of all necrotic tissue; this includes bone, hematomas, and abscesses.
- improve the microenvironment and treat the infection in order to achieve a successful outcome.
- Copious lavage with sterile isotonic fluids
- ensure that the fixation is sufficiently rigid because fracture instability disrupts local blood supply, which can promote microbial colonization and growth
37
Bacteria growing in biofilms are up to 1000 times more resistant to antibiotics than in planktonic state (Depypere et al. 2020).
-
- alteration in blood flow, poor local immunity, presence of inflammation > tissue ischemia and affects the distribution of systemically administered antimicrobial agents = why systemic antimicrobial therapy alone is insufficient.
- Biofilm > only way to remove it is to remove the implant or the affected tissue.
38
surgical treament
(1) removal necrotic tissue, sequestra, and foreign material
(2) meticulous debridement such that further disruption in the vascular environment is minimized
(3) biofilm removal and/or disruption.
- Samples for culture and susceptibility and histopathology
- Copious lavage with isotonic fluid
- Changing instruments
- removal of all implants once the fracture has healed because they remain a substrate for perpetuation.
Use of ESF + open wound management, has proven successful in resolving some infected fractures in dogs. Provide stability without further disrupting the biology, removed once the fracture has healed.
- In chronic and implant-associated osteomyelitis, antibiotic therapy alone does not yield satisfactory success rates
- surgical treatment (debridement) is often necessary (Hofstee 2020).
- debridement reduces the bacterial load at the site of infection, increasing the efficacy of antibiotics and reducing the risk of development of antimicrobial resistance
- - Although no clinical studies have confirmed the importance of fracture stability, there are abundant experimental data supporting the principle that stability is crucial for optimal outcome of an infected osteosynthesis
39
What are the recommendations regarding systemic and local treatment with ABx?
Systemic
- IV for 3-5 days
- Followed by oral for at least 4-6 weeks
Local
- ABx impregnated beads
- Initial concentration is 500x greater than typical serum concentrations
- heat-stable, hydrophilic and active against methicillin-resistant Staph (aminoglycosides, vancomycin)
40
Antimicrobial therapy
| - Bacteriostatic antibiotics should be avoided
- broad recommendations are difficult because of antimicrobial resistance.
- knowledge of local susceptibility patterns is useful
- guided by results of antimicrobial susceptibility testing and response to treatment
- Multiple antimicrobial agents may be necessary
- There is not a general consensus in either human or veterinary medicine on the duration and method of administration of treatment. Large, high-quality clinical trials are scarce
problems:
- inability to achieve sufficient antimicrobial concentrations in affected tissues i.e. some antimicrobials will distribute to the bone only to bind to calcium or other cations (e.g., tetracyclines and potentially fluoroquinolones). -
- Drug penetration and distribution dependent on the molecular weight, lipid solubility, and protein binding of the drug.
- Systemic administration of antibiotic in high doses and for prolonged periods can lead to toxic effects.
Clindamycin is not recommended as a first-choice drug because its use may induce antibacterial-resistant staphylococci.
TMS > keratoconjunctivitis sicca, arthropathy, and other idiosyncratic effects
41
recommended antibiotics
| Biofilms present 30–80%, and culture cannot detect the presence
- In dogs, high susceptibility rates to amoxicillinclavulanic acid, ceftiofur, ceftriaxone and ciprofloxacin have been found in osteomyelitis-causing bacteria
- Acute uncomplicated > ab's alone 4-6 weeks. The success rate is approximately 80%.
- IV for 3 to 5 days, followed by oral therapy for up to 8 weeks.
- Patient monitoring is essential (clinical assessment, radiographs 2 to 3 weeks after intervention and then q 4 weeks)
- historical recommendation > implant removal and systemic antibiotic therapy
current recommendation > surgical debridement and local application of antibiotics > reduces the need for systemic therapy and contributes to prevent relapse
- New antibiotics, like **dalbavancin**, have been tested in vitro and in vivo against biofilm-forming enterococci and staphylococci
| Siqueira 2014
42
local antibiotics
- delivery vehicles: hydrogels, cements, micro- and nanoparticles, coating/films, scaffolding, and sponges.
Antimicrobial impregnated beads
- successfully treat chronic osteomyelitis and septic arthritis in dogs.
- they can deliver initial concentrations that are **500-fold greater** than typical serum concentrations achieved with systemic
- Efficacious concentrations are sometimes present for several weeks without adverse systemic effects.
- The antimicrobial drugs often have activity against methicillin-resistant staphylococci. These agents include aminoglycosides (amikacin, gentamicin, or tobramycin) and vancomycin.
- **Bacteriocidal**, effective against gram negative bacteria such as E coli and Pseudomonas species as well as gram-positive Staphylococcus species.
Polymethylmethacrylate (PMMA) beads
gentamicin-impregnated sponges
used as adjuvant therapy of osteomyelitis (Wainberg 2015).
43
biological reasons for treatment failure
| Hayes 2013 A review of local antibiotic implants and applications to vet
biological reasons for treatment failure
1) the drug fails to reach its target
For systemically administered drugs, this mandates good vascular supply
Porin channel absence or mutation may prevent antibiotic entry
2) the drug is not active against the target pathogen
pus can bind antibiotics, reducing the active free drug fraction.
Antibiotic modifying enzymes can be produced by the target bacteria,
3) the target is altered
antibiotic-impregnated dextran polymer hydrogel, To date, no results of case series or treatment trials have undergone peer-reviewed publication
44
antibiotic-impregnated cement in joint arthroplasty
In summary, there is some evidence, even though it is cross-species, for the use of antibiotic-impregnated cement in joint arthroplasty, although this may come at the expense of shortened fatigue life. There is also good experimental data demonstrating the efficacy of antibiotic-impregnated cement beads in the treatment of osteomyelitis.
45
gentamicin ifused collagen sponge
cross-species data suggests
- there may be a role for GICS in antibiotic prophylaxis for clean surgeries where consequences may be devastating,
- there is also the potential for GICS to worsen infection rates when used in the face of bacterial contamination (56, 57).
- Canine data evaluating intra-articular GICS suggests a rapid decline in eluted gentamicin to sub-MIC levels,
- persistence of collagen-associated inflammation for several weeks> deleterious effects on wound healing
There is currently no high quality data on the efficacy or safety of GICS for the treatment of established infections.
46
PMMA beads - concerns?
- effective, disadvantage of requiring a subsequent surgery to remove to prevent nidus
- growing concerns over burst release (then subtherapeutic dose) of antibiotics, along with microbial colonization of the nondegradable cement biomaterial, may further exacerbate antibiotic resistance
Potential negatives surrounding the use of antibiotic impregnated cement include the risk of systemic toxicity and the generation of resistant organisms by prolonged exposure to sub-therapeutic concentrations of antibiotic.
47
Stainless steel implants infection
associated with significantly greater infection rates than titanium implants, although the topic is controversial
A postulated reason > soft tissue adheres firmly to titanium implant surfaces, while a fibrous capsule containing a fluid filled void is formed around steel implants.
The consequent dead space is more susceptible to bacterial colonization, and less accessible to host defence mechanisms
experimental study
Staphylococcus aureus biofilm formation found biofilm to form more readily on stainless steel than on titanium implant surfaces
48
Factors contributing to surgical site infections include lack
of carpal soft tissue coverage, surgery length, injury type,
thermal damage and external coaptation all of which may
compromise local vasculature.3 A recent systematic review
concluded that there is no advantage for titaniumimplants in
reducing implant-associated infection; however, implants
that preserved periosteal vascularity and soft tissue showed
statistical reduction in infection.23
Tanner MC, Fischer C, Schmidmaier G, Haubruck P. Evidencebased
uncertainty: do implant-related properties of titanium
reduce the susceptibility to perioperative infections in clinical
fracture management? A systematic review. Infection 2021;49
(05):813–821
49
metal implant coatings
hydrophobic materials
antibiotics,
nitric oxide releasing compounds
silver
have been assessed in both in vitro and in vivo
**hydrophobic** material polycation N,N- dodecyl,methylpolyethylenimines (PEI) was shown to prevent implant colonization in a sheep osteomyelitis model
theoretical risk of inducing resistant bacterial strains if the **antibiotic** release profile shows prolonged periods of sub-MIC antibiotic concentrations (Experimental studies in rats have demonstrated efficacy of a gentamicin-coated)
A method of covalently linking antibiotics to a titanium implant surfacehas been developed
In vitro studies evaluating **silver nanoparticle** coat- ings have shown promise, > yet to be fully assessed in appropriate in vivo or clinical trials
RCT trial
silver-coated ESF pins compared with standard stainless steel pins in 24 human patients identified a 10% reduction in positive culture rates.
Pages 2022 Long-term outcome of tibial plateau leveling osteotomy using an antimicrobial silver-based coated plate in dogs PLOS one
50
Lee 2019: Use of an amikacin-infused collagen sponge concurrent with implant removal for treatment of tibial plateau leveling osteotomy surgical site infection in 31 cases.
- Retrospective study.
Animals
Thirty-one client-owned dogs.
- Antimicrobial agents can be added to bioabsorbable materials and can also be engineered to control the duration and concentration of antibiotic treatment at the site
- Amikacin collagen sponge for TPLO SSI
- This procedure had a 96.8% long-term resolution of SSI. It should be considered as a treatment option for TPLO SSI.
51
- Savicky 2013 treated TPLO SSI with TPLO implant removal in 78 dogs. Resolution documented in 56 of 60 (93.3%) dogs treated with implant removal and empirical oral antibiotics and in 17 of 18 (94.4%) dogs treated with implant removal alone.
52
- Antimicrobial Photodynamic Therapy (aPDT) has recently been proposed to combat clinically relevant biofilms, including prosthetic joint infections (Hu 2018).
53
Pages 2022 Long-term outcome of tibial plateau leveling osteotomy using an antimicrobial silver-based coated plate in dogs PLOS one
Retrospective case study.
Animals: Dogs (n = 323, 337 stifles).
HyProtect
providing protection from local infection for at least 100 days.
clinical efficacy > debated, lack of clinical trials, standardization in coating manufacturing, and lack of evidence
mechanism of its bactericidal activity is not completely understood
- inactivation of enzymes of the respiration chain by metal binding to thiol groups
- induction of hydroxyl radicals
antimicrobial effect may be limited to tissue in contact with the coated material, and may be ineffective in reducing superficial SSI or SSI located on non-coated screws.
SSI rates were similar between the BioMedtrix™ group and the control group.
The antimicrobial HyProtect® did not reduce SSI in this study.
54
Prognosis
variable and depends on host and microbial factors.
- Side effects of antimicrobial chemotherapy must be balanced with likelihood of success and the animal’s quality of life
- relapse or reinfection can occur weeks, months, or even years later.
- Multiple surgeries increase the chance of complications that can ultimately result in fixation failure and even amputation.
- Fungal infections are particularly problematic
55
Hematogenous Osteomyelitis Tx
- Because of nonspecific clinical signs
- immediate and aggressive therapy
- IV 3 to 5 days before changing to oral
- Oral >21 days minimum, the choice of antibacterial agent based on C&S
- Empirical > include bactericidal agents that are active against β-lactamase–producing Staphylococcus
- Because bacteremia, septicemia, and other organ injury can occur, treatment should also be directed to correct these issues and progress monitored.
- Radiographic evaluation 2 to 3 weeks to evaluate response
- should improve within days of initiation of ab
prognosis.
Systemic manifestations and the presence of joint involvement indicate a worse
56
Infected Joint Prostheses
| tx goals: eradicate infection, alleviate pain, restore joint function
limited information in the veterinary literature regarding the most appropriate treatment
- Implant infection = catastrophic complication
- prevalence of **infection for cementless THR 0 to 3·7%**
- Traditionally, removal advised with preservation of surrounding bone stock.
cases series ( 3 dogs)
- described successful revision of infected cemented total hip prostheses with a one-stage removal and replacement with cementless components (Torres 2009)
case report
- describes the diagnosis and treatment of THR infection with surgical debridement, appropriate antibiotic therapy and prosthesis retention (Dan 2014)
In many cases, implant removal is required > excision arthroplasty, arthrodesis, or amputation.
human
- two-stage revision considered to be the gold standard (meta-analysis 2011)
- consists of implant removal followed by treatment of the infection until complete resolution.
- infection is resolved, reimplantation of a prosthesis
- Although numerous reports from the human literature describe successful implant retention and/or one-stage revisions, there is growing concern for increasing antimicrobial resistance given the frequent use of vancomycin
57
Open fractures
- retrospective 1085 open fractures in human concluded that combining antibiotic-impregnated PMMA beads with systemic antibiotics significantly decreased infection rates from 12% to 3.7%
- best outcome with early start of ab’s
Tx
- appropriately lavaged, cleaned, and thoroughly debrided,
- rigid bone fixation
- soft tissue reconstruction
- The goals of treatment are to (1) prevent infection, (2) promote bony union, (3) repair soft tissue damage, and (4) restore function
- Methods to improve fracture healing:
bone grafting
bone graft substitutes
purified recombinant stimulatory factors.
- Types of bone grafts:
autogenous cancellouso/corticocancellous grafts
allogenic frozen,corticocancellous, cancellous
demineralized bone matrix.
- Corticocancellous or cortical grafts can be useful for large defects.
- **Cancellous bone graft can be safely placed in a contaminated wound**
- A cortical bone graft is at risk for infection and subsequently becoming a sequestrum
- The proportions of open fractures that developed delayed or non-union were significantly (P < 0.05) increased
Marshall 2022:
58
surgical site infection
- Reported rates are variable and it is difficult to compare between studies because of different (or inadequately described) criteria for identification of surgical site infections.
- Variations in study design, statistical power, study population, and variables that were assessed impact the ability to identify risk factors
- duration of surgery
risk doubling for each hour of surgery
use halsteads
- duration of anaesthesia
- method of wound closure
stainless steel skin staples, absorbable intradermal suture, or external skin sutures has been evaluated and results are conflicting
- antimicrobial prophylaxis
- comorbidities
found in and on patients, clinical personnel, and the environment and include S. pseudintermedius, Staphylococcus aureus, Enterobacteriaceae, Enterococcus spp., and Pseudomonas spp
59
Management of Surgical Site Infections
- prompt recognition of an abnormality and diagnosis of the surgical site infection
- surveillance plan of some sort. Good communication with owners and within the clinic staff, along with use of a standard definition of surgical site infection
- Culture is almost always indicated in suspected surgical site infections
- Assessment of culture results from superficial sites that have a commensal microbiota is difficult
- Draining tracts can be externally colonized with different bacteria than those that are causing the infection, so collection of more representative deep samples should be performed
- withdrawal of antimicrobials to collect samples should not be performed if there is a clear need for systemic antimicrobial therapy > potential for false-negative results must be considered
- Empirical antimicrobial therapy is usually indicated.
- based on
> expected bacteria at the site (e.g., staphylococci for orthopedic infections)
> expected susceptibility profile ( the region or at the facility)
> drug (e.g., safety, cost, route of administration, frequency of administration)
> patient (e.g., comorbidities, owner to administer medications)
- If an infection is present at the site of an implant, it is reasonable to assume that biofilm has been established
- study of tibial plateau leveling osteotomy surgical site infections where antimicrobial therapy alone failed in 89% of cases but clinical signs resolved in 95% of dogs that had implants removed
60
Tx wound infections
One antibiotic attacks the metabolically active organisms
near the surface, while the other targets the sessile organisms. Another strategy
is to apply topical antibiotics, where a much higher concentration of drug is
delivered to overcome the biofilm MIC with low to no systemic absorption and less
risk of resistance. Such drugs as rifampicin, daptomycin, or colistin can easily penetrate
the biofilm matrix, but resistance often rapidly develops. Following with a second antibiotic,
however, clears the biofilm.
Biofilm-based
wound care uses frequent, aggressive debridement to break up the biofilm and
temporarily make the bacteria more susceptible to systemic antimicrobials, combined
with an individualized topical treatment
Commercially available antibiofilm agents include lactoferrin, xylitol, and LipoGel
61
reported SSI rates:
clean 2.7-5.7%,
clean-contaminated 3.2%,
contaminated 4.3%
dirty 12.5%
62
Risk of infection after double locking plate and screw fixation
of tibial plateau leveling osteotomies in dogs weighing greater
than 50 kilograms
Jayson Tuan
Retrospective study (January 2003-October 2017).
Animals: Two hundred seventy-five dogs
double locking plate
and screw fixation (DLP), standard locking plate and screw fixation (LP), and conventional
nonlocking plate and screw fixation (NLP
Dogs with NLP, LP, and DLP had postoperative
infection rates of 24.5%, 13.3%, and 9.1%, respectively
Fixation of TPLO with DLP in dogs weighing >50 kg does
not seem to increase the risk of SSI compared with LP and NLP
63
Protocol changes to reduce implant-associated infection rate after
tibial plateau leveling osteotomy: 703 dogs, 811 TPLO (2006-2014)
Stine 2018
retrosepctive
iodophore-impregnated adhesive drape, cefazolin administration every 90 minutes
intraoperatively and then every 4 hours until hospital discharge,
orthopedic surgical gloves,
triclosan-coated intradermal sutures (instead of staples),
soft-padded bandage with mupirocin ointment, use of single-use gloves while handling
Elizabethan collar
postchange cohort was decreased by 88%
Postoperative infections after implementation
of this protocol should be monitored to evaluate its potential impact on the
emergence of antibiotic resistance.
64
Timing of and risk factors for deep surgical site infection
requiring implant removal following canine tibial plateau
leveling osteotomy
McDougall 2021
retrospective. risk factors for deep SSI in TPLO
Deep SSI and implant removal 144 of 4813 (3.0%)
All of the dogs received postoperative antimicrobials
male dogs and GSDs
Among dogs undergoing the TPLO, SSI reported 3%–15.8%
breed (GSD),
intact male dog status,
increased body weight,
preoperative colonization with (MRSP), anesthesia time,
certain types of implants,
performance of a meniscectomy,
lower experience of the attending surgeon,
lack of postoperative antibiotics
conflicting result re postoperative abs as protective against SSI
- postoperative cefpodoxime did not reduce risk in a prospective study (Spencer et al)
- antimicrobials not alter the risk of either superficial or deep SSI in a more recent study (Clark 2020)
65
Investigation of Variables Associated with Surgical Site
Infection following the Management of Canine Cranial
Cruciate Ligament Rupture with a Lateral Fabellotibial
Suture
Thomas Cox 2020
SSI rate was 17.3% and removal of the lateral fabellotibial suture was performed in 53%
of SSI.
Bodyweight and induction with propofol were identified as significant risk factors
66
Calcium sulfate antibiotic-impregnated bead implantation
for deep surgical site infection associated with orthopedic
surgery in small animals
Peterson 2020
Retrospective,16, Calcium sulfate antibiotic-impregnated bead implantation for Deep SSI orthopedic
calcium sulfate – similar elution characteristics to PMMA but substrate is bio-resorbable
- SSI resolution: 6/10 treated therapeutically; prevention 6/6 treated prophylactically
- unresolved treatment 3/4 susceptibility not confirmed
- complications: 1/16 – extrusion of beads from ESF pin tracts Resolution of SSI was inconsistent > when bacteria were susceptible to the antibiotic implanted, SSI resolved in all but one case.
67
Number of previous surgeries and antibiotic resistance decreases the success of local administration
of antibiotic-impregnated poloxamer 407 hydrogel
when managing orthopedic surgical site infections in dogs
Smith 2023
34, retrospective. previous surgeries and antibiotic resistance decreases the success of vancomycin-impregnated poloxamer 407 hydrogel and sysetemic ab’s.
Surgical implants: removed in 8 dogs, replaced in 12, or retained in 2
The rate of infection clearance was 77%. hydrogel had a high success rate improve treatment outcomes in dogs with complicated SSI
8 unsuccessfull > explant or euthanised, 2 nonunion
outcomes were negatively impacted by:
- multidrug or methicillin resistance
- number of surgeries before gel implantation.
Systemic antimicrobials have varying success in cases of orthopedic SSI in the presence of an implant, with reported rates at approximately 70%.
68
Clark 2020 – inflence of post-operative antimicrobials on SSI
- incidence: 25.6% - MRSP, Staph. pseudintermedius, MRSA
- post-operative antimicrobials not protective but did not predispose to resistance
- groups dissimilar (31 dogs no antimicrobials vs 277 treated)
- risk factors: body weight associated with deep incisional SSI and resistant infection
sx and ga duration associated with incisional/deep SSI and resistance
surgeon correlated with deep SSI
