Effect of Posterlor Splen Fixation With Bone Cement on Vertebral Growth Plate and Disc in Dogs: A Histological Study

Ha, Kee Yong; Ok, In Young; Moon, Myung Sang

Abstract

In this study, author tried to clarify the chronological and histological change of the growing spine after posterior cement fixation in dogs. The material used for the study consisted of 24 male mongrel dogs, aged 8 weeks. Lumbar spines, from 3rd to 5th were fixed posteriorly with bone cement (Zimmer Co. U.S.A.). After posterior spinai fixation with bone cement, there dogs at a time were sacrificed every 4 weeks up to 32 weeks, and histologic changes of intervertebral disc, growth plate and the vertebral bodies were observed after hematoxylin & eosin stainning with light microscope. The results obtained were as follows: 1. Thinning of the growth plate and distortion of the cartilage columns developed gradually after posterior cement fixation of the spine, but premature closure of the growth plate did not develop and the growth of the vertebral body continued till 32 weeks after operation. 2. Intervertebral disc thinned posteriorly and widened anteriorly without any changes in subchondral cortices, though there is some bony atrophy in the body which is represented by the thinning and coarseness of bony spicules. 3. At 16 weeks the cartilage layer of the vertebral end plate became thinner, and at 32 weeks there were profound degenerative changes in the cartilages. 4. After fixation of the spine, the nucleus pulposus gradually degraded and was replaced by fibrous tissues, and began to adhere to the vertebral end plate at 24 weeks and completely adhered to it at 32 weeks after fixation. 5. The direction of the horizontally arranged annulus fibrosus began to derange from 24 weeks after fixation, and at 32 weeks all the fibers of the annulus fibrosus were vertically arranged completely. Through this study it is found that posterior spinal fixation with bone cement affects growths of the vertebral growth plate, and end plate slightly, but there were no cessation of cartilaginous growth which might later cause the vertebral deformity. Also it is clarified that posterior fixation of e spine with cement develops noticeable degenerative changes in the intervertebrai disc and thereby develops the lordotic curve of the cemented segment of the spine.