Any time a horse suffers an infection of any synovial structure, there is a risk that the infection could be so damaging as to lead to loss of use or even euthanasia. An Australian retrospective study sought to identify factors that might influence return to function and survival in horses with direct contamination of a joint or tendon sheath. Most breaches of a synovial structure in this study were due to a penetrating wound.
Information gleaned from the report might be helpful for making decisions in managing a synovial injury as well as to help provide insights for prognosis.
The study reviewed medical records of 186 horses with synovial infections in the 10-year period of 2008-2017. Horses that survived to discharge were followed up with phone conversations [Crosby, D.E.; Labens, R.; Hughes, K.J.; et al. Factors Associated with Survival and Return to Function Following Synovial Infections in Horses. Frontiers in Veterinary Science, Oct 2019, vol. 22; https://doi.org/10.3389/fvets.2019.00367].
Of the 186 horses in the study, 86.6% received treatment, and of those, 90.1% survived to discharge.
Treatment consisted of synovial lavage in nearly 94% of cases, as well as systemic antimicrobials. Lavage methods included needle, endoscopy, arthrotomy or a combination. Some cases received more than one lavage.
The use of systemic antimicrobials was associated with increased likelihood of survival, although horses treated with doxycycline were less likely to return to function. The report noted that “the likelihood of return to function is lower than for survival.”
Complications occurred in 15 horses that included laminitis, antimicrobial-associated diarrhea, thrombophlebitis, right dorsal colitis and a nosocomial wound infection.
There were follow-up reports for 145 horses that survived. Of the 120 cases considered in the analysis for return to function, 65% did achieve return to function. Twenty-five of the 145 sruvivors were not considered in this assessment due to loss to follow-up or they were too young for active athletic pursuits.
The 42 horses that did not return to function included 28 racehorses and 14 involved in other equestrian disciplines. Four of the 14 were later euthanized due to complications associated with the synovial infection.
The report identified better survival success with longer duration of treatment with systemic antimicrobials. That said, prolonged antimicrobial treatment was also associated with decreased likelihood of return to function. The authors suggested that this could be due to the presence of refractory infections that adversely affected soundness.
This retrospective study summary stated that:
- Time from onset of a synovial infection to initiation of treatment did not affect survival or return to function.
- There was no association between after-hours anesthesia and survival or return to function as has been reported in other studies.
- Bone and tendon involvement did not affect outcomes of survival or return to function.
- Method of lavage or number of lavages did not affect outcomes.
- The study concluded that high-volume lavage is important no matter the method.
In conclusion, horses treated for synovial infections have a good prognosis for survival and a moderate prognosis for return to desired use.