STUDY DESIGN: The preoperative and postoperative lateral radiograms and clinical results were analyzed in 22 cases of lumbar spinal stenosis with osteoporosis treated by posterior decompression and posterior lumbar interbody fusion. OBJECTIVES: To assess the efficiency of the cage-instrumented posterior lumbar interbody fusion in lumbar spinal stenosis with osteoporosis. SUMMARY OF LITERATURE REVIEW: Problems in surgical treatment of osteoporotic spinal stenosis were early screw loosening and early reversal to the original deformity because of insufficient mechanical stability in the bone-screw interface, and special strategy is essential for transpedicle screwing to sustain axial and screw cut-up load applied by flexion-extension motion in vivo. MATERIALS AND METHODS: We reviewed 22 cases of lumbar spinal stenosis with osteoporosis(Jikei grade I, II/III) from June 1996 to July 1998 with an average follow up period of 1.4 years. Inclusion criteria was combined segmental instability, deformity, spondylolisthesis and herniated nucleus pulposus with significant disc space narrowing. We asssessed the radiographic results of sagittal angle correction(SAC) of the instrumented segment and disc height restoration(DHR) on the preoperative, postoperative and last follow up lumbar lateral views, and clinical results according to the Kirkaldy-Willis criteria. RESULTS: Postoperative mean SAC gain was 10degree(p<0.05) and mean SAC loss at last follow up was 1.1degree(p>0.05). Postoperative mean DHR gain was 21.3%(p<0.05) and mean SAC loss at last follow up was 3.9%(p>0.05). The clinical result was analyzed as 2 excellent(9.1%), 16 good(72.7%), 4 fair(18.2%) and no poor. There were 2 intraoperative complications of a dural tear and a nerve root injury and 2 postoperative complications of a transient radiculopathy and a pseudoarthrosis. CONCLUSIONS: Cage-instrumented posterior lumbar interbody fusion can be an option for the lumbar spinal stenosis with osteoporosis requiring instrumentation because of instability, deformity or postdiscectomy anterior column deficiency.