Chapter 86 - Synovial and Osseous infection Flashcards
What are the main causes of orthopedic infection in horses?
Penetrating wounds, hematogenous spread, and iatrogenic introduction (surgical intervention or intrasynovial injection).
Why is the distal limb of a horse at higher risk for infection?
Due to poor muscle and soft tissue coverage with reduced vascular supply.
What can the strong inflammatory response in a synovial cavity lead to during infection?
Significant cartilage damage and subsequent osteoarthritis.
Why is fracture fixation in horses associated with a high risk of surgical site infection?
How can orthopedic infections affect a horse’s future performance?
They can cause chronic pain, joint stiffness, and reduce future performance.
Why are neonate foals more susceptible to infection compared to adults?
Due to their immature immune system and potential failure of passive transfer of immunity (IgG).
What is the role of failure of passive transfer in foals developing septic arthritis and osteomyelitis?
It leads to bacteremia and septicemia, which can localize in bones and joints via hematogenous spread.
What percentage of foals in neonatal intensive care units are affected by septic arthritis and osteomyelitis?
Up to 13%.
Which bacteria are commonly isolated from the joints of foals with septic arthritis?
Gram-negative bacteria like Escherichia coli, Actinobacillus spp., and Klebsiella spp..
What factors are associated with a negative outcome in foals with septic arthritis?
Multiple septic joints and the presence of multisystemic disease.
What is an S-type infection?
An infection associated with the synovial membrane and fluid, typically in very young foals under 2 weeks old.
What is the prognosis of foals with multiple septic joints?
Negative outcome in the presence of multisystemic disease
Which joints are most commonly affected in S-type infections?
Tarsocrural, stifle, and metacarpo-/metatarsophalangeal (MCP/MTP) joints.
What is an E-type infection?
An infection localized to the articular epiphyseal complex or the bone adjacent to the articular cartilage.
Which joints are commonly affected by E-type infections?
Distal femur, talus, proximal and distal radius, distal tibia, and patella.
In what age group of foals do E-type infections typically occur?
Older foals with multiple joints affected and often with a prior history of illness.
What is a P-type infection?
An infection that localizes in the long bone physes of older, generally healthy foals.
Which bacterial isolates are commonly found in P-type infections?
Streptococcus, Rhodococcus, Actinobacillus, and Escherichia coli.
What are the typical clinical signs of S- and E-type infections?
Joint effusion, lameness, synovial distension, periarticular edema, and pain on palpation.
What additional clinical findings are common in P-type infections?
Periarticular swelling with marked sensitivity to palpation and intermittent lameness.
What hematological change is a reliable indicator of osteomyelitis in E- and P-type infections?
Plasma fibrinogen levels of 900 mg/dL or higher.
What imaging modality is used as a baseline to assess bone involvement in these infections?
Radiographs.
What are the common causes of synovial infections in adult horses?
Penetrating traumatic injury, iatrogenic causes following surgery, or intrasynovial injections
What is the most commonly isolated bacterium in synovial infections in adult horses?
Staphylococcus aureus.
What diagnostic test is essential for confirming synovial sepsis?
Synovial fluid analysis, including cytology and bacterial culture.
hat is the typical nucleated cell count (NCC) indicating a synovial infection?
More than 20,000 cells/μL.
What adjunctive biomarker is useful for diagnosing septic synovitis?
Serum and synovial fluid serum amyloid A (SAA).
hat role does D-lactate play in diagnosing septic synovitis in horses?
It has no significant diagnostic value in differentiating septic from nonseptic arthritis in horses.
What are the clinical signs of synovial infections in adults?
Joint effusion, pain on palpation, and sometimes subchondral bone lysis.
What percentage of horses survive to hospital discharge after treatment for septic synovial infections?
85% to 90%.
What factor is associated with a lower likelihood of return to athletic function in horses with synovial infections?
Delay in treatment, increased synovial fluid total protein, undergoing more than 1 endoscopic procedure, and presence of osteitis or osteomyelitis.
How many hours are the timeline for treating synovial contamination?
Horses treated within 24 hours of synovial contamination were less likely to develop septic arthritis and more likely to return to athletic activity compared to those treated after 24 h
96% horses responded to one endoscopic lavage survived to hospital discharge, how many% of horses when it was more than one lavage?
46%
Figure 86-1. Lateromedial radiographic projection of the shoulder (A) and of the elbow (B) showing E-type osteomyelitis of the distal scapula (A) and P-type osteomyelitis of the olecranon.
What are teh reference values for nucleated cell count? TP?
orange or red and may sometimes be an opaque pink or yellow. A nucleated cell count (NCC ) of more than 20,000/μL should be suspected as infected, especially when combined with an elevation in total protein (TP) greater than 3.5 to 4 g/dL.
Typically, the presence of ___% degenerate neutrophils with or without the presence of intracellular bacteria is definitive for infection but the absence of degenerative change of neutrophils does not exclude synovial infection.
Typically, the presence of 90% degenerate neutrophils with or without the presence of intracellular bacteria is definitive for infection but the absence of degenerative change of neutrophils does not exclude synovial infection.
Blood SAA sensitivity %, blood SAA specifiticty % and synovial fluid SAA have moderate to h
sensivity % and specificity %
Blood and synovial fluid SAA have moderate to high sensitivity (82% and 80%) and specificity (89% and 73%) for diagnosis of seps
What is the SAA that is important to note in serum and synovial fluid in cases of infectious and noninfectious arthritis?
A more significant increase (1000–2000 mg/L) can be seen in horses with acute infectious synovitis compared with noninfectious synovitis
What is considered the gold standard for diagnosing sepsis?
Microbial culture.
What should be submitted before starting antimicrobial therapy?
A culture and sensitivity test.
What factors influence obtaining a positive culture from synovial fluid?
Culture method, organism number, virulence, and organism defense mechanisms.
What range of positive culture results from synovial fluid is reported?
64% to 89%.
How does using blood culture medium affect bacterial culture results?
It improves results, with a 79% success rate.
Is there an advantage to culturing the synovial membrane over synovial fluid?
No, bacterial isolation is similar or higher in synovial fluid.
What should be done if intraarticular antimicrobials have already been administered?
A sample for culture and sensitivity should still be obtained.
How much fluid do typical blood culture vials require?
8 to 10 mL.
Does a positive culture significantly affect survival to hospital discharge?
No, survival is not significantly affected by culture results.
What should be cultured in cases of hematogenous spread of infection?
The primary infection site (e.g., umbilicus, urachus) or direct aspiration of the physis.
When is fungal culture particularly important?
If the infection is associated with a wound or intrasynovial medication.
What imaging is typically used to detect early soft-tissue swelling in S-type infections?
Radiographic imaging.
What diagnostic imaging modality provides excellent sensitivity for detecting bone lesions?
Computed tomography (CT).
What imaging technique is superior for detecting cartilage lesions and synovial proliferation?
Magnetic resonance imaging (MRI).
Which imaging modality is excellent for localizing axial skeleton lesions?
Nuclear scintigraphy.
What are typical sonographic findings in septic synovitis?
Marked effusion, hyperechogenic particles, and synovial thickening.
What is the goal of synovial lavage in treating septic synovitis?
Remove foreign material, microorganisms, and inflammatory cells.
What type of anesthesia is recommended for high-volume synovial lavage?
General anesthesia with endoscopic guidance.
What solution is preferred for synovial lavage?
A balanced electrolyte solution.
What additive to lavage fluids may result in inflammatory changes if used at bactericidal concentrations?
Chlorhexidine (CHD).
What free-radical scavenger is reported as safe for use in lavage fluids?
Dimethyl sulfoxide (DMSO).
What marker has been evaluated for use in determining when to stop synovial lavage?
Serum amyloid A (SAA).
How do synovial fluid values change after repeated lavage?
Inflammation causes alterations in synovial fluid values.
What synovial fluid parameters decrease in horses with favorable outcomes after lavage?
Nucleated cell count (NCC) and total protein (TP).
What concentration of TP after endoscopic lavage may indicate reduced survival?
5 to 5.5 g/dL.
What imaging modality provides early detection of intramedullary bone lysis?
MRI.
What technique is often used in places difficult to palpate for synovial effusion?
Ultrasonography.
What type of antimicrobial therapy is recommended for adult horses with synovial sepsis?
Broad-spectrum antimicrobials including penicillin and aminoglycosides.
What condition can synovial sepsis lead to if not treated properly?
Loss of cartilage structure and intrathecal adhesions.
What percentage of horses with positive synovial cultures have reduced athletic function when infected with Staphylococcus aureus?
30%.
What is often required for the resolution of chronic or refractory infections?
Arthroscopic lavage, débridement, and synovectomy.
What risk is associated with arthrotomy and lavage in septic arthritis?
Increased risk of ascending bacterial infection.
What is the preferred technique for managing septic arthritis?
Arthroscopy with synovectomy and lavage.
What should be done for chronic, progressive infectious osteomyelitis?
Arthrodesis or stimulated ankylosis.
Why is surgical management of septic osteomyelitis controversial in foals?
It may cause irreversible growth plate disruption.
What combination of therapy is used to treat septic osteomyelitis in adult horses?
Surgical débridement and local antimicrobial therapy.
When is medical treatment alone successful in foals with infectious lesions?
In cases with minimal lameness and subtle radiographic lesions.
What complications can arise from surgical débridement of physeal lesions in foals?
Pathologic fractures or angular limb deformities.
What antimicrobial treatments are used until culture results are available?
Broad-spectrum antimicrobial therapy.
What broad-spectrum antimicrobial combination is typically used in horses?
A ß-lactam and aminoglycoside.
Which antimicrobial should be added if anaerobic infection is suspected?
Metronidazole.
What is the purpose of regional limb perfusion (RLP)?
To deliver high concentrations of antimicrobial at the site of infection.
What limits the use of regional limb perfusion (RLP) in certain cases?
Vascular damage or severe soft tissue compromise.
What type of tourniquet is recommended for regional limb perfusion?
A wide-elastic or pneumatic tourniquet.
What size catheter is advised to minimize vascular trauma in RLP?
Small butterfly catheters (25- to 27-gauge).
What should be applied after drug administration in regional limb perfusion?
A pressure bandage.
What technique can be combined with RLP for synovial infection treatment?
Joint lavage.
What is ideal for treating infections with concentration-dependent antimicrobials?
Regional limb perfusion (RLP).
What technique delivers antimicrobials directly into the bone or joint?
Intraosseous or intraarticular antimicrobial regional perfusion.
What are the advantages of intrasynovial constant rate infusion (CRI)?
Avoids daily synoviocentesis and allows joint lavage.
Which antimicrobials are commonly used for intrasynovial administration?
Amikacin and ceftiofur.
What antimicrobial has been shown to be safe for intrasynovial constant rate infusion (CRI)?
Gentamicin.
Why are antibiotic-impregnated biomaterials used more in bone infections?
There is a risk of cartilage damage with their use in synovial structures.
What is the limitation of polymethylmethacrylate (PMMA) in synovial infections?
It can cause damage due to motion within the synovial structure.
Which antibiotic-impregnated biomaterial is absorbable and useful in foals?
Plaster of Paris (POP).
What type of lesions are collagen sponges safe to use in?
Tarsocrural joints of healthy horses.
What is a major disadvantage of using constant rate infusion (CRI) for antibiotics?
It requires extensive management and nursing care.
What type of antimicrobials are less suited for constant rate infusion (CRI)?
Concentration-dependent antimicrobials.
Why are foals with severe swelling and progressive lesions managed surgically?
Due to the increased risk of joint sepsis and failure of medical treatment.
What should be used for antimicrobial delivery in cases of limited vascular access?
Intraosseous regional limb perfusion.
Figure 86-4. (A) Gross image of a draining tract and (B) craniocaudal radiographic projection of the elbow region of surgical site infection post olecranon fracture repair. Intraoperative images of the draining tract
Figure 86-4. Intraoperative images of the draining tract (C, arrow) extending down to the distal screw (D, arrow) and biofilm formation visible on the distal aspect of the plate and screw head (E). The draining tract was débrided, the screw removed and replaced and copious antibiotic lavage was performed. The surgical site was packed with collagen sponge impregnated with ceftiofur. Preoperative (F), immediately postoperative (G), and 1 year postoperative (H) lateromedial radiographic projections of infected olecranon fracture repair with successful management of postoperative surgical site infection.
What are acute phase proteins (APP)?
APPs are proteins that increase in plasma in response to inflammation.
Which APPs are mentioned in the text?
SAA, haptoglobin (Hp), and fibrinogen.
Can APPs specifically detect infections?
No, they are not specific for infection but can indicate inflammation.
Which measurement is more reliable for determining treatment response?
The trend in SAA measurement.
What is a limitation of radiography in early infection stages?
Soft-tissue swelling limits its effectiveness.
What can imaging in advanced infection show?
Bone lysis and periosteal reaction consistent with implant loosening.
Why is culture and susceptibility testing of fluid samples important?
It guides treatment selection and direction.
How does ultrasonography help in detecting infection?
It detects fluid accumulation and accurate fluid aspirates.
What happens during implant sonication?
It dislodges the adherent biofilm to improve culture diagnostics.
Does a negative sonicate result rule out infection?
No, a negative result does not rule out infection.
What is the advantage of local antimicrobial therapies?
They deliver high drug concentrations with reduced systemic side effects.
What should treatment be based on?
Culture and sensitivity results.
What nearly always fails in infected internal fixations?
Parenteral antimicrobial treatment.
How are antimicrobial impregnated beads used?
They are strategically placed around stable fixation sites.
What is one way to facilitate later removal of beads?
Placing them on a “string”.
What type of needles are recommended for regional limb therapy?
Small gauge butterfly needles (25–27 gauge).
What should be applied immediately after needle removal?
Compression to the vessel.
What additional treatment is essential for infected tissues?
Drainage and débridement of necrotic tissue.
What is often required to eliminate implant-associated infection?
Implant removal.
What is the ideal timing for implant removal?
After infection control and sufficient healing.
What options exist if there’s unstable repair and continued infection?
Replace or remove implants, manage with external fixation.
What can be done to cleaned and sterilized implants?
They can be reimplanted with new screws.
Why is the prognosis for orthopedic infections concerning?
They increase treatment costs and risk mechanical failure.
What should be done to the previous screw holes?
They can be packed with absorbable antibiotic-eluting materials.
What can prompt euthanasia in severe cases?
Delayed or non-union due to infections.
What have local antimicrobial delivery techniques improved?
The management and outcomes of orthopedic infections.
What advantage do minimally invasive techniques offer?
They have fewer complications and greater success rates.
