Long-term outcome and effect of diagnostic analgesia in horses undergoing interspinous ligament desmotomy for overriding dorsal spinous processes.

Objective: To report the long-term outcome of horses treated with interspinous ligament desmotomy (ISLD) for pain associated with overriding dorsal spinous processes (ORDSP) and determine the influence of preoperative diagnostic analgesia on long-term outcome.

Study Design: Retrospective study.

Animals: Eighteen horses.

Methods: Data were collected from horses presenting for ISLD to the University of Pennsylvania New Bolton Center between January 2013 and May 2018. Follow-up of ≥3 months postsurgically was obtained from the owner, trainer, or referring veterinarian. Long-term improvement was compared between horses that improved with diagnostic analgesia presurgically and horses that did not undergo diagnostic analgesia presurgically by using a χ test. Univariate logistic regression was used to test associations between long-term improvement and independent variables.

Results: Clinical signs had improved in 13 of 18 horses at long-term follow-up (median, 14.5 months; range, 3-57). Clinical signs improved in nine of 10 horses responding to diagnostic analgesia but only in four of eight horses that did not undergo diagnostic analgesia (χ [1], N = 18) = 3.55; P = .06). Although the likelihood of long-term improvement increased with prior diagnostic analgesia (odds ratio = 6.3; 95% confidence interval = 0.73, 55.0; P = .09), it did not reach statistical significance.

Conclusion: A higher proportion of horses experienced long-term improvement in clinical signs after ISLD when horses responding to preoperative diagnostic analgesia were compared with horses that were not tested.

Clinical Significance: This study provides some evidence to support the use of diagnostic analgesia in conjunction with clinical examination for identification of clinically relevant ORDSP.