Objective To invest igate the ef fect iveness and signi f icance of percutaneous endoscopic discectomy followed by interbody fusion using B-Twin expandable spinal spacer for degenerative lumbosacral disc disease. Methods Between January 2007 and August 2008, 21 patients with degenerative lumbosacral disc disease were treated with endoscopic discectomy followed by interbody fusion using B-Twin expandable spinal spacer. Among them, there were 13 males and 8 females with an average age of 52 years (range, 28-79 years). And the disease duration ranged from 3 months to 40 years (median, 9 months). The affected segments included T11, 12, T12-L1, L1, 2, and L2, 3 in 1 case respectively, L4, 5 in 4 cases, and L5, S1 in 13 cases. All patients had intractable low back pain or lower extremity radicular symptoms. The placement methods of B-Twin expandable spinal spacer were double sides in 15 cases and single side in 6 cases. Oswestry Disabil ity Index (ODI) and Macnab grading were used to determine the function recovery after operation. And Suk’s standard was used to determine the fusion effects by X-ray. Results All 21 patients were followed up 18 months to 3 years (mean, 23.8 months). Sciatica symptoms disappeared after operation in 19 cases, no significant improvement occurred in 2 cases of thoracic disease. The ODI scores were 79% ± 16% at preoperation, 30% ± 9% at 1 month, 26% ± 10% at 3 months, 21% ± 12% at 6 months, and 20% ± 10% at 18 months after operation, showing significant differences between pre- and postoperation (P lt; 0.05). According to Macnab grading at 6 months postoperatively, the results were excellent in 14 cases, good in 5 cases, and fair in 2 cases with an excellent and good rate of 90.5%. According to Suk et al. standard, the results were excellent in 1 case, good in 19 cases, and poor in 1 case with an excellent and good rate of 95.2%. The muscle strength of the lower extremities had no improvement in 1 case of T11, 12 disc protrusion; pedicle screws fixation and decompression laminectomy were given after 6 months, but no improvement was achieved during follow-up. Protrusion recurred after 4 months in 1 case of L4, 5 disc protrusion, then was cured by laminectomy discectomy. The remaining patients achieved postoperative rel ief. Conclusion Endoscope combined with interbody fusion is a good combination to solve lumbar instabil ity. B-Twin expandable spinal spacer is a minimally invasive fusion choice of L4, 5 and L5, S1.