Long-term outcome and effect of diagnostic analgesia in horses undergoing interspinous ligament desmotomy for overriding dorsal spinous processes.
Authors: Brown Kara A, Davidson Elizabeth J, Ortved Kyla, Ross Michael W, Stefanovski Darko, Wulster Kathryn B, Levine David G
Journal: Veterinary surgery : VS
Summary
# Editorial Summary: Interspinous Ligament Desmotomy for Overriding Dorsal Spinous Processes Overriding dorsal spinous processes (ORDSP) represent a significant source of back pain in horses, yet determining which cases warrant surgical intervention remains clinically challenging. Between 2013 and 2018, researchers at the University of Pennsylvania evaluated 18 horses undergoing interspinous ligament desmotomy (ISLD) for ORDSP-associated pain, with particular focus on whether preoperative diagnostic analgesia—local anaesthetic infiltration around the affected spinous processes—could predict surgical success. At median follow-up of 14.5 months, 72% of horses showed improvement in clinical signs overall; however, horses that had responded positively to diagnostic analgesia preoperatively achieved improvement in 90% of cases (9/10), compared with only 50% improvement in those without prior diagnostic testing (4/8), suggesting a 6.3-fold increase in likelihood of long-term success, though this difference narrowly missed statistical significance. For practitioners, these findings support the integration of diagnostic analgesia into the clinical decision-making process when ORDSP is suspected, as a positive response provides reasonably strong prognostic value for identifying cases where ISLD will resolve the horse's pain and functional impairment. Conversely, horses that fail to improve with diagnostic analgesia may warrant further investigation for concurrent or alternative sources of back pathology before committing to surgery.
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Practical Takeaways
- •Use diagnostic analgesia (likely interspinous ligament injection) before committing to ISLD surgery—horses that respond to the diagnostic block have ~90% chance of clinical improvement versus ~50% in untested horses
- •ISLD appears effective for ORDSP-related pain in most cases (72% improvement rate), but preoperative diagnostic confirmation substantially increases success likelihood
- •Patient selection via diagnostic analgesia should be standard practice to avoid surgery in horses where ORDSP is not the primary pain source
Key Findings
- •13 of 18 horses (72%) showed improved clinical signs at median 14.5 months post-ISLD surgery
- •9 of 10 horses (90%) responding to preoperative diagnostic analgesia improved long-term versus 4 of 8 (50%) without diagnostic analgesia testing
- •Preoperative diagnostic analgesia response increased odds of long-term improvement by 6.3-fold, though this did not reach statistical significance (P = 0.09)