POSTOPERATIVE BONE REGROWTH IN LUMBAR SPINAL STENOSIS - A MULTIVARIATE-ANALYSIS OF 48 PATIENTS

Study Design. Forty-eight patients who underwent posterior decompressi ve surgery for lumbar spinal stenosis were studied. The effect of bone re-growth after posterior decompression in lumbar spinal stenosis on clinical outcome and the factors promoting the bone re-growth were inv estigated with a multivariate analysis model. Methods. Bone re-growth at the sites operated upon was evaluated as a percentage of re-growth of the original laminectomy site based upon plain radiographs. The deg ree of bone re-growth was classified into four groups: 1) no significa nt re-growth (Group I, bone regrowth rate 10% or less); mild (Group II , 11% to 40%), moderate (Group III, 41% to 70%), and marked (Group IV, 71% to 100%). The average follow-up period was 4.5 years (range, 2 to 7 years). Results. No significant bone re-growth was shown in 6% of t he patients, Mild re-growth was shown in 50%, moderate re-growth in 29 %, and marked re-growth in 15%. A multivariate analysis indicated that a total block in the preoperative myelogram, a follow-up period of mo re than 5 years, decompression at more than three spinal levels, and a ge under 60 years were associated with moderate or marked bone re-grow th. Spinal instability accelerated the bone re-growth mainly in the mi d and later follow-up intervals. Spinal levels adjacent to a fusion sh owed more bone re-growth. Patients with moderate and marked bone re-gr owth had poorer clinical outcomes than those with no significant and m ild bone re-growth. Conclusion. Bone re-growth in a surgical defect wi ll occur in most patients after posterior decompression. Moderate and marked postoperative bone re-growth are possibly related to recurrence of neurologic symptoms in the middle of and later on in follow-up per iods.