Septic Arthritis and Tenosynovitis

Question 1

What are some of the causes of septic arthritis or tenosynovitis?

Answer 1

1. Iatrogenic from joint injection
2. Hematogenous from foal with FPT
3. Lacerations or punctures
4. Local infections (less common- cellulitis, abscesses)
5. Idiopathic (not common)

Question 2

T/F: Every post-injection and post-op increase in lameness should be treated as an emergency

Answer 2

True- often this could be a sign of infection. Need to act fast as you could be held liable

Question 3

What are some signs associated with iatrogenic infection after IA injection?

Answer 3

-mild to moderate increase in white cell count
-lameness and swelling can slowly develop over days
-can take 2 weeks to present

Question 4

What are the common septic processes in foals which can lead to septic joints?

Answer 4

Systemic infections, umbilical infections, lung infections, GI tract infections

Question 5

What are some unique signs of hematogenous spread of infections to joints?

Answer 5

-can affect multiple joints
-more often associated with the bone/physis than in adults

Question 6

What clinical signs are associated with hematogenous septic joints?

Answer 6

Lameness, effusion, soft tissue edema/swelling, heat, pain on palpation, fever (more common in foals)

Question 7

What are some chemistry changes that you may expect with septic joints?

Answer 7

Elevated white cell count
-Elevated fibrinogen (>1000 could indicate septic osteomyelitis)
-increased serum amyloid A concentration (over 60)

Question 8

What may be seen on US when working up a septic joint case that can help you with your diagnosis?

Answer 8

Increased synovial fluid, increased echogenicity of synovial fluid, gas in synovial structure, thickened synovium, fibrin in joint, soft tissue disruption, or foreign body

Question 9

What may be seen on radiographs in a septic arthritis case?

Answer 9

Gas in synovial structures, tracking of wound direction, foreign bodies, fractures

Question 10

If there is a nail in the foot, what should you always do before attempting removal?

Answer 10

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

Question 11

How can you contrast inflammation from infection in terms of the total protein, WBC, and cell type?

Answer 11

Inflammation: TP <2.5 g/dL, WBC 500-20,000, 10-20% neutrophils

Infection: TP> 4.0 g/dL. WBC >30,000, neutrophils >80%

Question 12

What percent neutrophils is pathognomonic for sepsis?

Answer 12

95%

Question 13

What agents are most typically involved with septic arthritis?

Answer 13

Aerobic/Facultative anaerobes make up 91%: Salmonella, Strep Zpp, Ecoli, Staph aureus, borellia
-anaerobes (clostridium)
-mycoplasma
-rhodococcus
-candida spp

Question 14

What percent of lacerations/punctures involve the foot?

Answer 14

60%

Question 15

Define septic arthritis based on the NRC classifications

Answer 15

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

Question 16

What does the prognosis in a septic arthritis case depend on?

Answer 16

Involvement of synovial structures, tendons/ligaments, blood vessels, nerves, virulence of bacteria, drug resistance of bacteria

Question 17

Describe some of the complications associated with puncture wounds

Answer 17

-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

Question 18

If the joint infection is open, will it be painful?

Answer 18

Yes, but not nearly to the degree it would be if it was closed

Question 19

How do you assess for synovial involvement?

Answer 19

-Direct palpation of the wound with sterile gloves
-ultrasonography
-radiography
-arthrocentesis (away from contaminated area)

Question 20

Describe how you would perform through and through lavage on the tarsus of a horse?

Answer 20

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

Question 21

What is the first line of defense in acute cases?

Answer 21

Broad spectrum antibiotics and thorough lavage
-systemic penicillin and gentamicin and intraarticular amikacin + regional wound perfusion with amikacin

Question 22

What is the first thing you should do in cases of chronic synovial infections?

Answer 22

Culture prior to antibiotic administration

Question 23

What are the two factors that complicate treatment of chronic infections?

Answer 23

Biofilm and fibrin presence make bacteria resistant to most antibiotics and hard to access

Question 24

What is the first gross thing that occurs when there is damage to the articular cartilage?

Answer 24

Yellowing- due to loss of proteoglycan
-occurs within the first 24 hours of joint inflammation

Question 25

What is one of the main concerns when there is damage to the tendon sheath?

Answer 25

Inflammatory mediators can cause adhesions

Question 26

When would an arthrotomy be indicated?

Answer 26

In chronic, severe, or persistent cases -must be aware that synovial fistula can form -requires very careful maintenance

Question 27

What are some factors that impact ability to close in cases of lacerations over joints?

Answer 27

Duration, degree of devitalized tissue, size of synovial communication with wound, severity of synovial sepsis, amount of motion in the joint

Question 28

When should primary closure be attempted?

Answer 28

Wound occurred less than 4 hours ago -minimal trauma, sepsis, and adequate blood supply -should not be based solely on duration

Question 29

When should you pursue delayed primary closure?

Answer 29

-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

Question 30

When should delayed secondary closure be attempted?

Answer 30

In wounds with severe contamination or tissue devitalization -close after 4 days -managed as 2nd intention

Question 31

When should second intention healing be attempted?

Answer 31

Avulsion injuries with contamination, skin loss and soft tissue damage -wound debridement and lavage is critical for granulation -utilize skin grafting as needed

Question 32

What are some different techniques to improve antibiotic delivery into joints?

Answer 32

-Regional limb perfusion -intraarticular catheters -constant intraarticular infusion of antibiotics, joint infusion systems -absorbable antibiotic delivery gel

Question 33

Describe how regional limb perfusion is performed?

Answer 33

-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

Question 34

How are intra-articular catheters placed and maintained?

Answer 34

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

Question 35

What are some pros and cons to intraarticular catheters?

Answer 35

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

Question 36

What is the dose of gentamicin and amikacin that should be used if pursuing a constant intra-articular infusion?

Answer 36

1/3 body weight dose IA, remaining 2.3 systemic Max doses: gentocin 600 mg/day, amikacin 2500 mg/day

Question 37

What is the absorbable antibiotic gel we discussed in lecture?

Answer 37

Vetrigel - elutes antibiotics slowly over time

Question 38

Which has a better prognosis: septic joint or septic tendon sheath?

Answer 38

Joint!