A 50‐step walking test for analysis of recovery after decompressive surgery for thoracolumbar disc herniation in dogs

Abstract Background Despite its importance, there is no agreed definition of recovery of ambulation in dogs with spinal cord injury. Objectives To validate a new walking test in dogs recovering from thoracolumbar spinal cord injury. Animals Two hundred twenty‐four dogs weighing <20 kg: 120 normally ambulatory dogs, plus 104 dogs undergoing decompressive surgery for acute thoracolumbar intervertebral disc herniation. Methods Prospective cohort studies. The distance each freely‐ambulatory dog walked during 50 step cycles was regressed on ulna length. For each postsurgical dog, we recorded when the calculated 50‐step distance was completed without falling, or their inability to complete this distance by 4 months or more after surgery. Bayesian analysis compared outcomes for presurgical neurologic categories; association of recovery with several preoperative variables was explored using logistic and time‐to‐event regression. Results For control dogs, 50‐step distance (m) = 1.384 × ulnar length (cm) + 2.773. In postsurgical dogs, the 50‐step test provided decisive evidence that deep pain‐negative dogs were less likely to recover ambulation than dogs with intact pain perception (12/29 recovered vs 71/75; Bayes factor [BF] = 5.9 × 106) and, if they did recover, it took much longer (median 91 days vs median 14 days; BF = 1.5 × 103). Exploratory analysis suggested that presurgical neurologic status (subhazard ratio [SHR] = 0.022; P < .001) and duration of presurgical anesthesia (SHR = 0.740; P = .04) were associated with rapidity of recovery. Conclusions and Clinical Importance This straightforward 50‐step walking test provides robust data on ambulatory recovery well‐suited to large scale pragmatic trials on treatment of thoracolumbar spinal cord injury in dogs.