Septic Arthritis

Question 1

What are some causes of septic arthritis?

Answer 1

Naturally Occurring - hematogenous (seen in foals), traumatic

Iatrogenic - arthroscopy, arthocentesis, fracture repair, etc

Usually bacterial but can viral/ mycobacterial/ fungal

** Can prevent with lavages, antibiotics, effective drainage

Question 2

What processes occur that damage cartilage in septic arthritis?

Answer 2

• Fibrin is deposited
• Degradative enzymes ( colagenase, stromelysin, MMP) and cytokines (IL-1, 6, TNF) enter capsule

-Result is a loss of PG, decreased HA synthesis, joint effusion, pain, decreased synovial blood flow

Question 3

What are the different types of septic arthritis in foals?

Answer 3

S (synovial), E (epiphysis), P

Must ID all joints when diagnosing

Question 4

What is S-type foal septic arthritis?

Answer 4

Affects synovial fluid and synovial membrane

Occurs in foals < 1 week old

Affects larger/ multiple joints (stifle, tibiotarsal)

CS: acute severe lameness and effusion

Question 5

What is E-type foal septic arthritis?

Answer 5

Affects bones next to articular cartilage –> appears as subchondral lysis on rads)

 Age: weeks old
 Hx: FPT, other dz (pneumonia, diarrhea)
Joints:
 Multiple
 Distal femur, talus, tibia, radius
 CS: mild intermittent lameness +-fever…THEN acute exacerbation of lameness/effusion

Question 6

What is P-type foal septic arthritis?

Answer 6

Occurs on physis of long bone, may include joint

Will appear healthy without disease history

Affects distal physis of MC/T III, radius, tibia –> only one site though

CS: Premonitory lameness THEN acute severe
lameness/swelling, and periarticular swelling without effusion

Question 7

How do you diagnose P-type septic arthritis?

Answer 7

Radiographs

Physis aspirate

Bone biopsy

DON’T DEBRIDE –> DAMAGES AND CLOSES PHYSIS

Question 8

What values would you see on a blood work in foal septic arthritis?

Answer 8

Synovial fluid
 >50,000 cell count, >90% neuts
 Color –normal to cloudy, red, orange, pink

Bloodwork:
Increased fibrinogen +-leukocytosis
 Fibrinogen usu. >900 mg/dL with bone involvement

US –> hypercellular fluid detail (hyperechoic)

Question 9

What is the prognosis for septic arthritis in foals?

Answer 9

77% –> pretty good

Question 10

What can predispose foals to septic arthritis?

Answer 10

Failure of passive transfer leads to bacteremia, resulting in septic arthritis

Question 11

What is the difference between swelling and joint effusion?

Answer 11

Effusion is the accumulation of fluid within the joint

Swelling is an accumulation of fluid outside the joint

Question 12

What risk factors can predispose adult horses to septic arthritis?

Answer 12

Iatrogenic –> Staph usually infects joint

Trauma –> many different possibilities, Enterobacteriaceae most commonly infects (Staph, pseudomonas, sometimes fungi)

** an open joint is an infected joint

Question 13

What are the clinical signs of septic arthritis in adults?

Answer 13

Similar to foals

Acute severe onset of lameness (important)

Synovial effusion

Peri-articular heat and swelling

May or may not have fever

Question 14

How do you diagnose septic arthritis?

Answer 14

Joint tap and microbiology –> GOLD STANDARD

Gross exam

TP, cell count, smear stains

C/ S –> Enrichment culture and blood culture *better yield

**In foals, aspirate physis for physitis potential

Question 15

T/F

When tapping a septic joint, you should tap TOWARDS the wound

Answer 15

FALSE

Tap AWAY from the wound to get a false reading

Question 16

What Imaging modalities do you want to run to diagnose septic arthritis?

Answer 16

Radiograph –> effusion, soft tissue swelling, osseous involvement

US –> guide for aspirate, hypercellular fluid, umbilicus check in foals

Nuclear scintigraphy

Question 17

Why do you not want to add chlorhexidine/ povidone iodine in septic arthritis lavages?

Answer 17

Kills healthy cells and doesn’t do anything to fix the disease

Question 18

What are consequences of septic arthritis?

Answer 18

• Acute synovitis w/ suppurative effusion
• Cartilage destruction
• Capsular fibrosis/ ankylosis
• Degenerative joint disease
• Contralateral limb laminitis
• Possible euthanasia

Question 19

How do you want to treat septic arthritis?

Answer 19

• Start off with broad spectrum ABs locally–> pen/gen (give for at least 30 days and continue to give 2 weeks after resolution)
• Lavage early and often in large volumes (5-10 L) –> VERY IMPORTANT!!!!!
• Arthroscopic lavage ideal but can use large needle lavage
• Sedate and give local anesthesia (2% mepivacaine in jiont) for arthoscopy/ -otomy

Question 20

What type of lavage solutions do you want to use for lavage solutions?

Answer 20

• Balanced electrolyte solutions –> LRS, normosol
• DON’T USE CHLORHEXIDINE, POVIDONE-IODINE
• Maybe DMSO

Question 21

How often do you want to lavage and when should you stop?

Answer 21

• Perform daily if severe enough

- Stop once lameness, effusion/ swelling, other signs resolve

Question 22

What antibiotics are septic arthritis susceptible to?

Answer 22

Aminogylcosides –> concentration dependent AB

• Give 50 mg Amikacin

Question 23

How do you perform regional limb perfusion?

Answer 23

• Give local anesthesia and sedation
• Apply tourniquet above and below joint if possible
• Inject solution slowly with butterfly catheter
• Leave tourniquet for 30 min
• Give 1/3 of systemic dose

Question 24

What antibiotic do you want to use in a regional limb perfusion in cows?

Answer 24

Florfenicol - effective againts F. necrophorum and A. pyogenes

Question 25

How do you give intra-osseous antibiotics

Answer 25

• Local anesthesia
• Apply Esmarch tourniquet
• Inject solution slowly and leave tourniquet on for 30 min

Question 26

What other drugs do you want to give for septic arthritis?

Answer 26

• Morphine/ opiates –> very painful condition
• NSAIDs (give GI protectants too)
• Lidocaine and ketamine CRI
• Epidural for hindlimb –> opiates and detomidine

Question 27

What is the most important way to measure the effectiveness of treatment?

Answer 27

• Clinical lameness and pain

– NSAIDs can mask pain