Radiologic and computed tomography image evaluation of bone regrowth afterwide surgical decompression for lumbar stenosis

Study Design. Retrospective study of bone regrowth after decompressive surg ery for lumbar spinal stenosis. Objectives. To assess bone regrowth at the operation site, to compare the b one regrowth rate calculated from plain radiographs with computed tomograph ic image examinations, to determine the effects of bone regrowth on clinica l outcome, and to investigate the factors promoting bone regrowth. Summary of the Background Data. Moderate or marked bone regrowth in a surgi cal defect has been reported in most patients after decompression for lumba r spinal stenosis. Postoperative bone regrowth is related to recurrence of neurologic symptoms in the middle of and later on in follow-up periods. Methods. Twenty-three patients who underwent decompressive surgery for lumb ar spinal stenosis, with an average follow-up of 8 years, were evaluated re trospectively regarding the degree of bone regrowth at the posterior arch. Early postoperative radiographs and computed tomographic images were compar ed with those obtained at final follow-up. Bone regrowth at the operation s ites was evaluated as a regrowth percentage of the original laminectomy sit e. Results. Decompressive surgery caused bone regrowth to occur at the operati on site in most of the patients. However, this regrowth was mild because th e mean bone regrowth rate evaluated from plain radiographs averaged 11% and from computed tomographic images 7.7%. In only 20% of the patients was the bone regrowth rate more than 20%. Changes were found to be more elevated a t the facet joint level than at the pedicle level-Evaluations of regrowth o btained from plain films and computed tomographic image examinations were c ompared. Radiographs seemed to overestimate the bone regrowth. The associat ion of postoperative spinal instability with the development of new bone wa s statistically significant. No relation between bone regrowth and clinical outcome was found. Conclusions. Bone regrowth in a surgical defect occurs in most patients aft er posterior decompression. In this study the bone regrowth rate was mild a nd did not affect the clinical outcome.