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Aims

To determine the incidence of synovial sepsis following intra-articular and intrathecal injections. Synovial sepsis is a serious potential complication of intrasynovial medication.

Methods

Available case records for all horses receiving intrasynovial medications (ISMs) performed by 9 ambulatory clinicians were examined over 5 years (2006–2011). Intrasynovial medications were defined as therapeutic interventions, based on clinical history and orthopaedic examination; nontherapeutic injections for diagnostic analgesia were excluded. Routine protocol was not to clip injection sites; the skin was prepared using standard aseptic technique. Scrupulous aseptic injection technique was employed at all times. All horses were under the care of a single practice, dealing with mainly Thoroughbred racehorses. Records were cross-referenced against synovial cytology submissions and hospital admissions for synovial sepsis. Development of 2 out of 4 clinicopathological signs of synovial sepsis (lameness, joint distension, synovial white blood cell count >10,000/l, synovial total protein >25 g/l) within 8 weeks of medication of the same synovial space was considered to represent a post medication complication (PMC). Failure of the PMC to resolve with conservative therapy was considered to represent post medication synovial sepsis (PMSS).

Results

During the study period 9456 ISMs were recorded, in 4332 sessions, in 1732 horses. Corticosteroids were included in 92.3% of ISMs, 94.8% included amikacin and 0.15% (14/9456) included polysulphated glycosaminoglycans (PSGAGs). Twelve horses developed PMC (0.0013% ISM), 4 horses developed PMSS (0.0004% ISM). All 4 horses returned to use following joint lavage. Administration of intrasynovial PSGAGs, was significantly associated with PMSS (P<0.0001 OR = 787 95% CI 145–20,337). Intrasynovial medications that included amikacin were less likely to develop PSSM (P = 0.005 OR = 0.0181 95% CI 0.0019–0.174); however if the PSGAGs group was excluded the difference became nonsignificant (P = 0.0981).

Conclusions and practical significance

The risk of iatrogenic sepsis following intrasynovial medication is extremely low. Intrasynovial medication with PSGAGs should be avoided without concomitant antimicrobials.

Acknowledgements

A. Wilson and K. Batteate for case collation.

Ethical animal research

Not required by this Congress: retrospective analysis of case records. Sources of funding: None. Competing interests: None.