ObjectiveTo compare the effectiveness of decompression and short fusion or long fusion for degenerative scoliosis (DS) with a Cobb angle of 20-40° combined with spinal stenosis.MethodsThe clinical data of 50 patients with DS who were treated with decompression combined with short fusion or long fusion between January 2015 and May 2017 were retrospectively analysed. Patients were divided into long fusion group (fixed segments>3, 23 cases) and short fusion group (fixed segments≤3, 27 cases). There was no significant difference in gender, age, disease duration, and preoperative visual analogue scale (VAS) score of leg pain, Oswestry disability index (ODI), thoracic kyphosis (TK), thoracolumbar kyphosis (TLK), pelvic incidence (PI), pelvic title (PT), and sacral slope (SS) between the two groups (P>0.05); however, the VAS score of low back pain, Cobb angle, and sagittal vertical axis (SVA) in long fusion group were significantly higher than those in short fusion group (P<0.05), and the lumbar lordosis (LL) was significantly lower than that in short fusion group (t=2.427, P=0.019). The operation time, intraoperative blood loss, fluoroscopy times, hospital stay, and complications were recorded and compared. The VAS scores of low back pain and leg pain and ODI score were used to evaluate the clinical outcomes before operation and at last follow-up. X-ray films of the whole spine in standard standing position were taken before operation, at 6 months after operation, and at last follow-up, and the spino-pelvic parameters were measured.ResultsThe operation time, intraoperative blood loss, and fluoroscopy times in the short fusion group were significantly less than those in the long fusion group (P<0.05); there was no significant difference in hospital stay between the two groups (t=0.933, P=0.355). The patients were followed up 12-46 months with an average of 22.3 months. At last follow-up, the VAS scores of low back pain and leg pain and ODI score significantly improved when compared with those before operation (P<0.05). Except for the improvement of VAS score of low back pain (t=8.332, P=0.000), the differences of the improvements of the other scores between the two groups were not significant (P>0.05). The Cobb angle, SVA, TLK, and PT significantly decreased, while SS and LL significantly increased in the long fusion group (P<0.05), while the Cobb angle and PT significantly decreased and SS significantly increased in the short fusion group at last follow-up (P<0.05). There was no significant difference in spino-pelvic parameters between the two groups at 6 months after operation and at last follow-up (P>0.05). The improvements of Cobb angle, SVA, LL, PT, and SS in the long fusion group were significantly higher than those in the short fusion group at last follow-up (P<0.05). There was no perioperative death in both groups. The incidence of complications in the long fusion group was 34.8% (8/23), which was significantly higher than that in the short fusion group [11.1% (3/27)] (χ2=4.056, P=0.034).ConclusionThe DS patients with the Cobb angle of 20-40°can achieve satisfactory clinical outcomes and improve the spino-pelvic parameters by choosing appropriate fixation levels. Short fusion has less surgical trauma and fewer complications, whereas long fusion has more advantages in enhancing spino-pelvic parameters and relieving low back pain.