Radiographs of the infected joints are important to determine if there is any
radiographic change of the associated subchondral bone, epiphysis or physis and to
serve as a reference point to determine if the affected areas are increasing in size
over time. Foals have many physes and separate centres of ossification and “normal
areas of abnormal looking bone” and even when one is used to evaluating foal
radiographs it is can be very helpful to acquire images of the contralateral joint for
comparison. Radiographs help to identify regions that need to be debrided and to
determine future prognosis.
Ultrasound may be used to visualise the amount of fibrinous debris within the joint
and can also give an indication of the cellularity of the fluid, as higher concentrations
increase the echogenicity of the fluid. Physes, joints and bone surfaces are relatively
easy to differentiate ultrasonographically which is often a useful adjunct to
radiography. Ultrasound is very important to help locate the more difficult sources of
septic arthritis and tenosynovitis that are often radiographically normal.
Treatment
Lameness resulting from septic focus should be managed aggressively to control
and eliminate the infection.
One should try to identify the primary source of sepsis and broad spectrum
parenteral antibiotic cover is the first line of defence. Acquiring a blood sample for
culture prior to administration of antibiotics is often helpful in managing primarily
young septicaemic foals (up to 2 weeks); in my experience older foals typically have
negative blood cultures.
Foals with umbilical infections should ideally have urachal–umbilical resections
performed, or in mild cases may be managed medically.
Foals with S-type infections generally respond well to flushing of the synovial
structure.
This can be done under heavy sedation or general anaesthesia with a through-andthrough large bore needle lavage after aseptic preparation of the affected region.
This works well provided there is not a large amount of fibrinous debris within the
synovial cavity, which tends to either repeatedly block the needles or just simply
create a “holey cheese” effect where the lavage fluid runs through the path of least
resistance through the fibrin clots. In these cases a thorough lavage of the joint is not
possible as all the “solids” stay behind and remain a nidus for infection.
Intravenous (or intraosseous) regional limb perfusion (IVRP) is used alone or more
commonly as an adjunct to joint lavage and is best performed with appropriate
antibiotics according to antibiogram results.
One must be mindful of the fact that there are numerous case reports of ischaemic
limb or skin necrosis following IVRP in foals. Keeping total tourniquet time to around
20-25 minutes and using no more than one third of a total systemic antibiotic dose
for the procedure in heavily sedated foals has resulted in no such cases in our clinic
over the last 8 years. Routinely used antimicrobials in our clinic for IVRP are
Amikacin, Gentamicin, Ceftiofur, Benzyl penicillin potassium, Cefquinome and, on
rare occasions, Imipenem.
Proceedings
of
the
South
African
Equine
Veterinary
Association
Congress
2016
232