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The purpose of the present study was to investigate structural stability of extensive laminectomy and the effect of subcutaneous fat autograft on restricting formation of postlaminectomy membrane (fibrous tissue). Eighteen healthy dogs of both sexes and of mixed breeding were divided into 6 groups : (1) unilateral hemilaminectomy (group H) on 3rd, 4th and 7th vertebrae ; (2) modified dorsal laminectomy (group D) on 3rd, 4th and 7th vertebrae. Hemilaminectomies were carried out incontinuously at 16 sites in 4 dogs, then subcutaneous fat autografts (group F) were applied to 8 laminectomy sites and no treatment (group C) was assigned to 8 laminectomy sites, too. Operating time of group H *30.9±10.4 minutes) was significatnly shorter (p<0.05) than that of group D (43.1±12.2 minutes), but surgical hemorrhage of group H is severer than that of group D. General states, such as standing, gait, defecation and urination, were normal. Upper motor neuron/lower motor neuron signs were not found and superficial/deep pain, proprioception and anal sphincter tone were normal. Gross postmortem findings and superficial/deep pain, proprioception and anal sphincter tone were normal. Gross postmortem findings were similar in all groups. The laminectomy sites of groups H and D were filled with fobous connective tissue at 4 months after operation and histopathological abnormalities of spinal cord were not found. One of eight laminectomy sites in group F was filled with fibrous tissue at 2 months after operation, but all operating sites of group C were covered with fibrous tissue. The present study indicated that extensive laminectomy on 7 vertebrae, using unilateral hemilaminectomy and modified dorsal laminectomy technique, maintained structural stability and subcutaneous fat autograft was effective on reducing the formation of fibrous membrane in laminectomy sites.
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