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 chi(2) 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 (chi(2)[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.