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).
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.
