INITIAL STUDIES OF HOLMIUM-YAG LASER CREATION OF SPINAL DEFECTS IN FETAL RABBITS - MODEL FOR UROLOGIC EFFECTS OF MYELOMENINGOCELE

Myelomeningocele (MMC) is characterized by paraplegia and incontinence , often necessitating surgery. Current models of MMC in sheep and prim ates create a spinal defect long after anomalous neural tube closure o rdinarily occurs. An ideal model of MMC would allow creation of the de fect at the earliest age in a low-cost species with a short gestation. We present a method utilizing the holmium laser to create spinal defe cts in rabbits in utero for the study of the pathophysiology and repai r of MMC, Pregnant rabbits of 22 to 23 days' gestational age were prep ared and draped in sterile fashion for laparotomy under general anesth esia, The abdomen was opened, and both uterine horns were inspected. D ouble opposing pursestring sutures were placed to secure the chorioamn iotic membranes over the fetal lumbar spine, Amniotic fluid was remove d with a needle and saved. Electrocautery was used to open the uterus within the pursestring suture, exposing the fetal dorsum, The spine wa s exposed by laser dissection of the fetal dorsal musculature. Posteri or laminectomy was accomplished with laser incisions of each side of t he spinous process, leaving the underlying dura and cord exposed. The pursestring was then cinched, amniotic fluid was returned, and the ute rus and trocar sites were closed. Cesarian section was performed at 30 to 31 gestational days, and the pups were examined and then humanely sacrificed for histologic evaluation of the lesion. The rabbit is an i nexpensive species with a short gestation (33-35 days), and four or mo re fetuses may be operated on per litter, with the remainder serving a s controls. Utilization of minimally invasive techniques including hol mium:YAG laser dissection facilitates creation of spinal defects at an early age in this small-animal model.