Radiologic and computed tomography image evaluation of bone regrowth after wide surgical decompression for lumbar stenosis.

STUDY DESIGN: Retrospective study of bone regrowth after decompressive surgery for lumbar spinal stenosis. OBJECTIVES: To assess bone regrowth at the operation site, to compare the bone regrowth rate calculated from plain radiographs with computed tomographic image examinations, to determine the effects of bone regrowth on clinical outcome, and to investigate the factors promoting bone regrowth. SUMMARY OF THE BACKGROUND DATA: Moderate or marked bone regrowth in a surgical defect has been reported in most patients after decompression for lumbar 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 lumbar spinal stenosis, with an average follow-up of 8 years, were evaluated retrospectively regarding the degree of bone regrowth at the posterior arch. Early postoperative radiographs and computed tomographic images were compared with those obtained at final follow-up. Bone regrowth at the operation sites was evaluated as a regrowth percentage of the original laminectomy site. RESULTS: Decompressive surgery caused bone regrowth to occur at the operation site in most of the patients. However, this regrowth was mild because the 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 at the facet joint level than at the pedicle level. Evaluations of regrowth obtained from plain films and computed tomographic image examinations were compared. Radiographs seemed to overestimate the bone regrowth. The association of postoperative spinal instability with the development of new bone was statistically significant. No relation between bone regrowth and clinical outcome was found. CONCLUSIONS: Bone regrowth in a surgical defect occurs in most patients after posterior decompression. In this study the bone regrowth rate was mild and did not affect the clinical outcome.