ObjectiveTo evaluate the effectiveness of modified "eggshell" osteotomy for the treatment of thoracolumbar kyphoscoliosis. MethodBetween April 2009 and June 2014, 19 patients with spinal deformity underwent modified "eggshell" osteotomy consisting of preserving posterior bony structures initially and enlarging surgical field for cancellous bone removal. There were 14 males and 5 females with an average age of 37.8 years (range, 18-76 years) and with a median disease duration of 7 years (range, 1-40 years). The disease causes included ankylosing spondylitis in 13 cases, spinal tuberculosis in 3 cases, and chronic vertebral compression fracture in 3 cases. Eleven patients showed single kyphosis and 8 patients had kyphoscoliosis. Preoperative Cobb angle of kyphosis was (64.2±30.1) °, while Cobb angle of scoliosis was (19.9±12.8) °. Apical vertebraes were T10 in 1 case, L1 in 3 cases, L2 in 7 cases, T10, 11 in 2 cases, T12, L1 in 4 cases, T12-L2 in 1 case, and T10-L1 in 1 case. Preoperative visual analogue scale (VAS) and Japanese Orthopaedic Association (JOA) score were 6.1±1.9 and 15.2±5.6, respectively. According to Frankel criteria for spinal cord function, 16 cases were rated as grade E and 3 cases as grade D before operation. Cobb angle, VAS, and JOA scors were used to assess relief of symptom. ResultsThe operation time was 215-610 minutes (mean, 343 minutes); intraoperative blood loss ranged from 900 to 3000 mL (mean, 1573 mL). All incisions healed primarily. Delayed onset ischemia-reperfusion injury of spinal cord occurred in 1 case at 6 days after operation, and symptoms alleviated after conservative treatments. All 19 cases were followed up 14-76 months (mean, 46 months). No loosening or breakage of internal fixation was observed during follow-up. Cobb angle of kyphosis, Cobb angle of scoliosis, VAS and JOA scores at 1 week after operation and last follow-up were significantly improved when compared with preoperative ones (P<0.05) . VAS and JOA scores at last follow-up were significantly improved when compared with scores at 1 week after operation (P<0.05) , but no significant difference was found in Cobb angle of both kyphosis and scoliosis between at 1 week after operation and at last follow-up (P>0.05) . At 1 week after operation, the correction rate for kyphosis was 34.1%-93.4% (mean, 62.2%), and the correction rate for scoliosis was 42.4%-100% (mean, 68.9%). At 48 months after operation, 3 patients with preoperative impaired spinal cord function achieved full recovery. ConclusionsModified "eggshell" osteotomy owns the advantages of shorter operation time and less intraoperative blood loss, thus it is able to correct thoracolumbar kyphoscoliosis safely and effectively.