ObjectiveTo evaluate the efficacy of the modified transforaminal lumbar interbody fusion(TLIF) approach of unilaterally single cage bone grafting combined with pedicle screw internal fixation system in the treatment of multi segmental lumbar spinal canal stenosis and lumbar instability. MethodsThirtyone cases of multisegmental lumbar spinal canal stenosis and lumbar instability were treated with decompression of the modified TLIF approach, internal fixation device fixation of GSS or SINO, interbody mixed bone graft, and unilateral single cage. Lesions were located in L1-S1 in 2 cases ,L2-5 in 5 cases, L2-S1 in 2 cases, L3-S1 in 9 cases, and L4-S1 in 13 cases. Lumbar instability or slippage site was in L1-5 in 2 cases, L2-4 in 5 cases, L2-5 in 2 cases, L3-5 in 9 cases, and L4-5 in 13 cases. There was isthmic spondylolisthesis in 12 cases (2 cases of traumatic), and degenerative spondylolisthesis i n 19 cases. Postoperative improvements in symptoms and signs were analyzed. ResultsThe results were excellent in 26 cases, and good in 5 cases according to the Hou Shuxun formulation of the evaluating standard of curative effect evaluation of curative effect.All 31 cases were with satisfactory reduction, and good interbody fusion The improvement rate ranged from 90% to 98% (average, 96%) according to Low Back Pain Disease Curative Effect of Japanese Orthopaedic Association.ConclusionModified TLIF approach of unilaterally single cage bone grafting combined with pedicle screw internal fixation system has such merits as complete decompression, stable fixation, minimally invasive bone grafting, easy fusion, and less nerve injury,etc., indicating it as an ideal method in the treatment of multisegmental lumbar spinal canal stenosis and lumbar instability

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