Septic Arthritis and Tenosynovitis Flashcards
What are some of the causes of septic arthritis or tenosynovitis?
- Iatrogenic from joint injection
- Hematogenous from foal with FPT
- Lacerations or punctures
- Local infections (less common- cellulitis, abscesses)
- Idiopathic (not common)
T/F: Every post-injection and post-op increase in lameness should be treated as an emergency
True- often this could be a sign of infection. Need to act fast as you could be held liable
What are some signs associated with iatrogenic infection after IA injection?
-mild to moderate increase in white cell count
-lameness and swelling can slowly develop over days
-can take 2 weeks to present
What are the common septic processes in foals which can lead to septic joints?
Systemic infections, umbilical infections, lung infections, GI tract infections
What are some unique signs of hematogenous spread of infections to joints?
-can affect multiple joints
-more often associated with the bone/physis than in adults
What clinical signs are associated with hematogenous septic joints?
Lameness, effusion, soft tissue edema/swelling, heat, pain on palpation, fever (more common in foals)
What are some chemistry changes that you may expect with septic joints?
Elevated white cell count
-Elevated fibrinogen (>1000 could indicate septic osteomyelitis)
-increased serum amyloid A concentration (over 60)
What may be seen on US when working up a septic joint case that can help you with your diagnosis?
Increased synovial fluid, increased echogenicity of synovial fluid, gas in synovial structure, thickened synovium, fibrin in joint, soft tissue disruption, or foreign body
What may be seen on radiographs in a septic arthritis case?
Gas in synovial structures, tracking of wound direction, foreign bodies, fractures
If there is a nail in the foot, what should you always do before attempting removal?
Take radiographs to see what structures are involved
-mark on the nail how much was exposed on outside, so after removal you can determine how much was inside
How can you contrast inflammation from infection in terms of the total protein, WBC, and cell type?
Inflammation: TP <2.5 g/dL, WBC 500-20,000, 10-20% neutrophils
Infection: TP> 4.0 g/dL. WBC >30,000, neutrophils >80%
What percent neutrophils is pathognomonic for sepsis?
95%
What agents are most typically involved with septic arthritis?
Aerobic/Facultative anaerobes make up 91%: Salmonella, Strep Zpp, Ecoli, Staph aureus, borellia
-anaerobes (clostridium)
-mycoplasma
-rhodococcus
-candida spp
What percent of lacerations/punctures involve the foot?
60%
Define septic arthritis based on the NRC classifications
Clean- no sepsis present, no signs of inflammation
Clean contaminated- minor sepsis
Contaminated- acute non purulent inflammation
Dirty infected- traumatic wound, devitalized tissue, fecal contamination, foreign bodies, bacterial inflammation with pus
What does the prognosis in a septic arthritis case depend on?
Involvement of synovial structures, tendons/ligaments, blood vessels, nerves, virulence of bacteria, drug resistance of bacteria
Describe some of the complications associated with puncture wounds
-bacteria and foreign bodies are often driven into the depths of the wound and are difficult to drain
-penetration of synovial structure may not be recognized
-depth and location are difficult to assess
If the joint infection is open, will it be painful?
Yes, but not nearly to the degree it would be if it was closed
How do you assess for synovial involvement?
-Direct palpation of the wound with sterile gloves
-ultrasonography
-radiography
-arthrocentesis (away from contaminated area)
Describe how you would perform through and through lavage on the tarsus of a horse?
Place 2 needles into the front of the joint, one needle in the lateral plantar pouch
-flush through the needle in the pouch until fluid runs clear
What is the first line of defense in acute cases?
Broad spectrum antibiotics and thorough lavage
-systemic penicillin and gentamicin and intraarticular amikacin + regional wound perfusion with amikacin
What is the first thing you should do in cases of chronic synovial infections?
Culture prior to antibiotic administration
What are the two factors that complicate treatment of chronic infections?
Biofilm and fibrin presence make bacteria resistant to most antibiotics and hard to access
What is the first gross thing that occurs when there is damage to the articular cartilage?
Yellowing- due to loss of proteoglycan
-occurs within the first 24 hours of joint inflammation
What is one of the main concerns when there is damage to the tendon sheath?
Inflammatory mediators can cause adhesions
When would an arthrotomy be indicated?
In chronic, severe, or persistent cases
-must be aware that synovial fistula can form
-requires very careful maintenance
What are some factors that impact ability to close in cases of lacerations over joints?
Duration, degree of devitalized tissue, size of synovial communication with wound, severity of synovial sepsis, amount of motion in the joint
When should primary closure be attempted?
Wound occurred less than 4 hours ago
-minimal trauma, sepsis, and adequate blood supply
-should not be based solely on duration
When should you pursue delayed primary closure?
-wound that has been present more than 8 hours
-wounds that benefit from serial debridement and topical antibiotics prior to closure
-dont do this if synovial structures are involved
When should delayed secondary closure be attempted?
In wounds with severe contamination or tissue devitalization
-close after 4 days
-managed as 2nd intention
When should second intention healing be attempted?
Avulsion injuries with contamination, skin loss and soft tissue damage
-wound debridement and lavage is critical for granulation
-utilize skin grafting as needed
What are some different techniques to improve antibiotic delivery into joints?
-Regional limb perfusion
-intraarticular catheters
-constant intraarticular infusion of antibiotics, joint infusion systems
-absorbable antibiotic delivery gel
Describe how regional limb perfusion is performed?
-horse is sedated deeply
-can use saphenous, cephalic or digital veins
-clip and aseptically prep area
-use brown gauze roll and tourniquet the limb
-use a 20 g butterfly catheter
-add 2g amikacin into 20 mL LRS
-inject slowly, checking for extravasation
-apply topical diclofenac to vessel
-place pressure bandage for 24 hours
How are intra-articular catheters placed and maintained?
Place via arthroscopy
-used for IA infusions daily
-may be used to flush joint standing 4x/day after initial placement
-bandage and cap must be changed once daily
What are some pros and cons to intraarticular catheters?
Fairly cost effective
-sterile technique is critical
-risk of cap disconnecting could be catastrophic
-ascending infection and tract formation can occur if left for too long
What is the dose of gentamicin and amikacin that should be used if pursuing a constant intra-articular infusion?
1/3 body weight dose IA, remaining 2.3 systemic
Max doses: gentocin 600 mg/day, amikacin 2500 mg/day
What is the absorbable antibiotic gel we discussed in lecture?
Vetrigel
- elutes antibiotics slowly over time
Which has a better prognosis: septic joint or septic tendon sheath?
Joint!
