Comparison of two minimally invasive approaches to the thoracolumbar spinal canal in dogs.

OBJECTIVE: To describe 2 minimally invasive approaches to the spinal canal for treatment of intervertebral disc disease and compare their efficacy to conventional hemilaminectomy. STUDY DESIGN: Experimental; randomized, controlled design. ANIMALS: Canine cadavers (n = 10; 5 small and 5 large dogs). METHODS: Barium-impregnated agarose gel (BA-gel) was injected into the spinal canal at 3 intervertebral spaces of the thoracolumbar spine in each cadaver. Sites were randomly assigned to 1 of 3 approaches: conventional (standard) hemilaminectomy (SH), endoscopic foraminotomy (EF), or foraminotomy via an illuminated port (FP). Computed tomographic scans were performed before and after the procedures. Procedures were compared for duration, bone window size, incision length, complications and percentage of BA-gel removed via repeated measures ANOVA. RESULTS: The incisions created during EF and FP were similar and smaller to that of a SH. The duration of EF was prolonged compared to FP and SH. The size of the vertebral window created was greater after SH in large dogs, while no difference was found between procedures in small dogs. The amount of simulated disc material removed from the spinal canal did not differ between procedures, regardless of the size of the dog. CONCLUSIONS: The two minimally invasive approaches were feasible in small and large dogs. Both techniques allowed similar removal of simulated disc material and may decrease soft tissue morbidity compared to SH.