[Minimally invasive surgery for the severe degenerative lumbar scoliosis: two stage protocol].

Objective To investigate the surgical outcome of minimally invasive surgery(MIS) for severe degenerative lumbar scoliosis(DLS) and put forward a two-stage MIS surgical strategy. Methods Prospective study of MISDEF Ⅲ DLS patients from June 2016 to August 2017 in the Second Affiliated Hospital of Zhejiang University was carried out, excluding the patients whose apex vertebrae of scoliosis was above L1/2 level or whose facet joint got spontaneous fusion. Fifty-three patients were included in this study for staging evaluation and MIS surgical treatment. Information was recorded, including gender, age, body mass index, follow-up period, pelvic incidence (PI), blood loss, operation time, visual analogue pain score (VAS), Oswestry disability index (ODI), complications in the perioperative period and follow-up period, and also the radiographic parameters such as scoliosis Cobb angle, the mismatch between pelvic incidence and lumbar lordosis (PI-LL), sagittalvertical axis (SVA), coronal balance (CB) before and after each stage of surgery or latest follow-up. The paired-samples t test was used to analyze the effectiveness of staging surgery. Results Fifty-three patients (18 males and 35 females) were included in this study. All patients had completed clinical and the follow-up records, with an average follow-up period of 11.52 months (6-20 months). A total of 168 segments fusions were performed with CLIF, 113 segments were performed with anterior column realignment (ACR), the average correct angle was 15.6°±6.3°(7°-28°) in sagittal plane each level. After the stage Ⅰ surgery, lumbar scoliosis cobb had been corrected for 55.35%, after the stage Ⅱ surgery, rate of correction was 75.6%. PI-LL had been matched (-32.8°±14.9° to -2.5°±9.4°), SVA was changed from 5.7 cm to 0.6 cm, the stage Ⅰ rate of correction was 80.3 and stage Ⅱ was 88.8%, pelvic tilt (PT), lumbar lordosis (LL) and CB had been restored; 13 (24.5%) patients were performed paraspinal approach transforaminal decompression. The posterior minimally invasive fixation indexes: 11(20.8%) patients were performed paraspinal approach transforaminal multi-segment transforaminal osteotomy (TFO) and internal fixation; 36(67.92%) cases were performed paraspinal approach transforaminal multi-segment fixation; 6(11.33%) patients were treated with percutaneous pedicle screw fixation. The average fixed segments was 7.4±1.4 in each patient. The blood loss of stage Ⅰ and stage Ⅱ operation was (157±71) ml, (343±224)ml, respectively. The operation time was (214±60) min, (190±54)min respectively in the two stage operations. The low back pain and leg pain VAS score and ODI improved after the stage Ⅰ and Ⅱ surgery (t=17.948, 10.099, 14.619, all P<0.001). Conclusions MIS for the severe degenerative lumbar scoliosis can achieve good clinical outcome and deformity correction. The two-stage protocol has the advantages of less complications and is well-tolerated. Key words: Degenerative lumbar scoliosis; Minimally invasive surgery; Staged operation