Vulnerability of the spinal cord to injury from extracorporeal shock waves in rabbits.

We studied the vulnerability of the spinal cord to extracorporeal shock wave treatment (ESWT). In this experiment, 12 rabbits were divided into three groups (4 in each group). All animals underwent a preceding lumbar laminectomy at L4 1 week before ESWT. In group 1, 2000 impulses of high dose (0.62 mJ/mm2 energy flux density) shockwave energy were applied to the spinal cord at the laminectomy site. In group 2, 2000 impulses of low dose (0.18 mJ/mm2 energy flux density) shockwave energy were applied to the same site as group 1. Group 3 did not receive ESWT and served as a control. None of the rabbits in the study groups (groups 1 and 2) showed weakness or paralysis of the hind limbs throughout the entire post-ESWT period. The spinal cord at the L4 level of all animals was harvested on day 13 after laminectomy. On gross morphology, the cord from the study groups and the control group showed normal surface appearance. On microscopic examination, the cord from the control group was normal, whereas the cords from the study groups showed varying degrees of myelin damage and neuronal loss. These microscopic findings were dose-dependent. For the low-energy group (group 2), neuronal loss was insignificant compared to that in the control group. ESWT produced varying degrees of microscopic changes of the treated cords, but no neurological symptoms. The neuronal injury was dose-dependent and mild in the low-energy group.