Prolonged postoperative antimicrobials may not be necessary following endoscopic lavage for blackthorn‐induced synovitis in horses

Abstract

Summary Background Synovial thorn penetration has mainly been studied within the broader category of septic arthritis and treated accordingly. However, blackthorn‐induced synovitis may represent a severe aseptic inflammatory response to irritant phenolic compounds of the blackthorn. Studies evaluating treatment, prognosis and complications of blackthorn‐induced synovitis as a distinct condition are limited. Objectives To report outcomes and complications of blackthorn‐induced synovitis treated with endoscopic synovial lavage. Study design Retrospective case series. Methods Clinical records of horses undergoing endoscopic synovial lavage for blackthorn synovial penetration only (2018–2025) were reviewed. Data regarding signalment, diagnosis, antimicrobial treatment, complications, and outcome were collected. Follow‐up was obtained by telephone and/or medical or competition records. Results Sixty‐three horses (87 synovial structures) were included. Forty‐one horses (56 synovial structures; Group 1) received <48 h of injectable antimicrobials; 22 horses (31 synovial structures; Group 2) received an additional 5‐day oral course. Mean total nucleated cell counts at presentation were 183.38 × 10 9 cells/L (SD: ±120.04 × 10 9 cells/L) and 100.7 × 10 9 cells/L (SD: ±97.8 × 10 9 cells/L), respectively. Surgery occurred a median of 1 day post‐injury [range: 0–22], with a median hospitalisation of 2 days (range: 1–8). Complications occurred in 19/62 horses (30.6%; Group 1: 26.8%; Group 2: 36.4%). Three horses (4.8%) required repeat synovial lavage for retained intrasynovial blackthorn and sixteen (25.8%) developed local complications, mainly cellulitis and local infections. Fourteen horses (22%) received further antimicrobials after discharge. All complications resolved. Of horses with long‐term follow‐up, 57/58 (98.2%) returned to their previous level of exercise within a median of 28 days (range: 8–195). One horse failed to return to work due to an unrelated orthopaedic injury. Main limitations Retrospective study; small sample size. Conclusions Blackthorn‐induced synovitis has an excellent long‐term prognosis following endoscopic lavage. Complete removal of blackthorn fragments is essential, and prolonged antimicrobials may not be necessary in cases with synovial involvement only.

The authors' abstract, as published at the source. Equine Veterinary Education, 2026 · DOI ↗