The fate of autogenous free-fat grafts after posterior lumbar surgery. Part 2. Magnetic resonance imaging and histologic studies in repeated surgery cases

Study Design. Histologic changes of free-grafted fat were investigated from surgical specimens taken at repeated lumbar surgery in 1B patients with degenerative spinal disease who previously had undergone posterior lumbar decompression and free fat graft. Objective. To clarify the clinical usefulness of freegrafted fat by histologic analysis. Summary of Background Data. The clinical postoperative serial magnetic resonance imaging studies in Part 1 showed that the size of grafted fat was reduced, and that the shape changed along with the shape of the dura mater. The shape of the grafted fat was remodeled in relation to the postoperative transient shrinkage and re-expansion of the dura mater. Methods. From repeated surgery cases, the status of the previously grafted fat tissue in the virgin operation was analyzed. Sections from the specimens resected surgically during repeated surgery were stained with hematoxylin and eosin or osmium. The size and quality of the grafted fat globules were analyzed by computer. Results. In all cases, grafted fat tissue was identified as a survival. Hematoxylin and eosin staining showed increased collagen fiber and hyperplasia of blood vessels entering the fat tissue that survived. From osmium staining, the size of fat globules was reduced. The shape and quality of the fat globules were analyzed by original staging. They showed various sizes, polymorphism, and vacuolar degeneration. Conclusions. Finding showed that the grafted fat used in posterior lumbar surgery reduced the size and quality of the fat globules, as compared with normal fat tissue. However, the grafted fat tissues were confirmed to be alive over the long term. This study clarified the fate of the grafted fat as observed by magnetic resonance imaging and histology from repeated surgery cases.