Orthopaedic infections Flashcards
There are 3 main underlying causes of orthopaedic infection in animals?
- Haematogenous spread
- Direct contamination from trauma / puncture wound
- Post-operative infection, usually associated with an implant
If only bone is infected, it is classified as?
osteitis
if bone marrow is infected, it is correctly termed?
osteomyelitis
Most common cause of orthopaedic infection of Neonates of all species?
- Navel haematogenous – joint ill.
- Acute haematogenous osteomyelitis.
- Management.
Most common infectious agents causing osteomyelitis in Neonates of all species?
Enterobacteriacae (poop)
E.coli
Most common cause of orthopaedic infection of dogs?
- Iatrogenic – orthopaedic sx
- Contaminated wounds –> extension of soft tissue wounds to bone
Most common infectious agents causing osteomyelitis in dogs?
Staphylococcus, strep, E.coli, proteus
Most common cause of orthopaedic infection in cats?
Contaminated wounds – CBA à extension of soft tissue wounds to bone
Iatrogenic – orthopeaedic sx
Most common infectious agents causing osteomyelitis in cats?
Anaerobes – CBA: Pasteurella multocida and bacteroides sp.
Staph and streps from skin
Most common cause of orthopaedic infection in Farm animals (sheep and cows)?
Haematogenous
Direct spread from neighbouring tissue
Trauma
Deep digital sepsis
Most common infectious agents causing osteomyelitis in Farm animals (sheep and cows)?
Epiphyseal osteomyelitis – salmonella
Physeal osteomyelitis – Corynebacterium pyogenes and salmonella
Actinomyces
Deep digital sepsis: Treuperella pyogenes
Most common cause of orthopaedic infection in Horses?
Septic arthirits 2° to surgery or injections
Osteomyelitis – wound, implant infection, fracture repair
Most common infectious agents causing osteomyelitis Horses?
Staph aureus and staph coagulase -ve
Enterobacteriacae - pseudomonas
Strep
Most common cause of orthopaedic infection in birds?
Haematogenous
Extension from soft tissie (tendontits à bone)
Bumblefoot
Most common infectious agents causing osteomyelitis in birds?
Poultry: Mycoplasma synoviae, Staph (can be vertically transmitted), E.coli (less common)
Why do post-operative / implant associated infections need to be treated differently?
- Greatest treatment challenge – multiple bacteria à broad spectrum antibiotics
- Biofilm formation on implant – antibiotics can’t penetrate
If you have a fracture which has been fixed with implants, and it develops a post-operative infection, should you remove the implants, and if so, when?
Indications for removal
- If the fracture is healed – doesn’t need implant
- If the implant isn’t providing any stability
Indications for leaving in
- If the fracture is unstable and not healed and the implants are providing stability.
- Bone CAN heal with infection provided its kept stable.
In Early disease (< 2 weeks) (NB bony changes usually take at least 14 days to develop) what radiographic changes may be seen?
- Soft tissue swelling, can have bone lysis in later stages of acute disease.
- Rarely gas shadows – IF the causative bacteria is gas producing (eg:clostridia)
In Late / advanced disease what radiographic changes may be seen?
- Bone lysis
- Periosteal new bone
- Sclerosis
- Cortical thinning
- Involucrum (area of sclerotic bone surrounding sequestrum)
- Delayed fracture healing/non union
- Sequestrum
What other differential diagnoses can cause similar radiographic changes which can appear like the early stages of osteomyelitis?
Soft tissue swelling: Muscle bruising, neoplasia, seroma, joint instability
What other differential diagnoses can cause similar radiographic changes which can appear like Late / advanced osteomyelitis?
Malignant neoplasia, bone cyst, disuse osteopenia, vascular infarctions
In early disease (< 2 weeks) (NB bony changes usually take at least 14 days to develop) what diagnostic tests to confirm diagnosis of infection vs other disease can be done?
Bloods – haematology for infection, bacteriology of blood.
Joint tap (if soft tissue swelling near joint) – Rule out septic arthiritis
Bone scintigraphy à Facilitates early diagnosis (rule in)
FNA of anything lumpy
In late/advanced disease what diagnostic tests to confirm diagnosis of infection vs other disease can be done?
Bone biopsy – Jamshidi
Swabs from discharging sinuses
Tissue samples for culture and sensitivity
FNA
Other problems / complicating factors that may be present in cases with osteomyelitis in early disease (< 2 weeks) (NB bony changes usually take at least 14 days to develop)?
- Sepsis (cause).
- Look for failure of passive transfer of colostrum in neonates as a cause.
Other problems / complicating factors that may be present in cases with osteomyelitis in late / advanced disease?
Sepsis – because of infection spread
Anaerobes hard to culture
Pathological fracture – makes infection management for complicated.
Involvement of surrounding structures: muscle, soft tissue, nerves (neuro defecits), joint involvement.
What can be seen here?
Mediolateral radiograph of a humerus showing chronic osteomyelitis.
Although the # has healed, a large sequestrum is present (arrow) surrounded by an involucrum.
Treatment should be considered in three stages:
1) Identify and treat underlying causes
2) Use of antimicrobials
3) Medical vs surgical treatment
Identify three underlying problems that could cause recurrent / resistant infection?
Antibiotic resistance
Immune compromise (failure of passive transfer)
Implants – persistent FB, sequestrum –> BIOFILM
What is a sequestrum and how would you treat it?
- Area of necrotic bone surrounded by sclerosis. Formed within a diseased bone. Common in chronic osteomyelitis.
- Treatment: Remove sequestrum, debride affected area and sinus tracts, remove necrotic bone, alow for drainage and obliterate dead space –> don’t close skin and just pack to allow drainage –> primary closure when discharge stops, antibiotcs to treat and prevent infection.
- In severe cases with joint and soft tissue complications –> amputate
How would you identify fungal osteomyelitis, and where does it usually occur (http://cal.vet.upenn.edu/projects/saortho/chapter_37/37mast.htm is a helpful resource)?
- Common in hot, wet regions
- Young/immunosuppressed animals most at risk
- Abnormalitis on haem and biochecm
- ALWAYS thoracic rads – resp signs common
- Plumonary granulomas may be mistaken for lung metastases with bone lesions
- May present with lameness and limb swelling
- DIAGNOSIS: Histopathology and isolation of organism
- TREATMENT: Ketoconazole – 10mg/kg sid for 2 months then 5mg/kg for a further 2 months.
- Prognosis poor for aspergillus infections – Will need to be on permanent treatment ith ketoconazole or itraconazole.
Antimicrobial options to use in osteomyelitis (including route of administration, and duration) of dogs?
- Amoxiclav (can add metronidazole – anaerobes –> broader spectrum)
- Clindamycin
- 1st gen cephalosporins – Cephalexin (can add metronidazole – anaerobes –> broader spectrum)
- Long course: 6-8 weeks
Antimicrobial options to use in osteomyelitis (including route of administration, and duration) Farm animals (sheep and cows)?
- Penicillin IM
- Sodium iodide
Antimicrobial options to use in osteomyelitis (including route of administration, and duration) in Horses?
Enterobacteriacae and staph –> Amikacin (aminoglycoside)
Strep –> Cephalothin
Enterobacteriacae à Sefotaxmine
Penicillin IM
Gentacicin IV
Metronidazole PO or IV
Antimicrobial options to use in osteomyelitis (including route of administration, and duration) in Birds?
Amoxyclav
Which antibiotics would you avoid in neonates?
- Bacteriostatic or orals
- Tetracyclines
- Chloramphenicol
What are the screening tests/diagnosis and surgical treatment for Sequestrum?
- Diagnosed by characteristic appearance on radiography – presence of sequestrum +/- involucrum
- All dead / necrotic bone must be removed or will act as a nidus for infection. Good prognosis once removed.
What are the screening tests/diagnosis and surgical treatment for Foreign material present?
- Radiography, Ultrasound
- Remove it
What are the screening tests/diagnosis and surgical treatment for Associated synovial infection?
- Joint tap
- Could flush?
- Antibiotics mostly
What are the screening tests/diagnosis and surgical treatment for Umbilical infection in neonates?
- Palpation
- Culture bloods
- none
What are the screening tests/diagnosis and surgical treatment for Unstable fractures?
- Radiographs
- Stabilise fracture
What are the screening tests/diagnosis and surgical treatment for Dead space / soft tissue defects?
- Radiographs
- Drain and oppose
What are the screening tests/diagnosis and surgical treatment for Implants present?
- Radiographs
- Discussed earlier
What are the screening tests/diagnosis and surgical treatment for Antibiotic resistance?
- C & S
- Appropriate antibiotic
What are the screening tests/diagnosis and surgical treatment for Tissue necrosis / vascular impairment?
- Visualisation
- Radiographs
- Debride, remove sequestrum
What are the basic principles of surgical treatment in these cases – i.e. what is the underlying principle that you are trying to achieve?
- Make it clean
- Fix it
- Remove dead stuff or underlying cause
- Minimise dead space
How can you minimise the risk of post-operative infection?
- Good sterile technique
- Prophylactic antibiotics 1 hr before, 24h after… should be avoided.
- Longer antibiotics if clean-contaminated surgery
