Introduction: Minimally invasive (MIS) approaches to the thoracolumbar spine have recently been gaining popularity given their ability to reduce blood loss, operative time, and hospital stay1,3. Although these techniques have been successfully applied to the adult degenerative deformity patient, they have some limitations when addressing severe degenerative scoliosis3. Despite these shortcomings, the MIS lateral interbody fusion (LIF) offers several advantages1,2. Here we report our early experience with a hybrid approach utilizing MIS-LIF with open Smith-Peterson osteotomies (SPO) and posterior instrumentation to address adult degenerative deformity.

Methods: We reviewed the medical records of all patients who underwent a combined MIS-LIF and open multilevel SPO/facetectomies and fusion spanning T10 to pelvis from January 2015 to June 2016. All patients underwent MIS-LIF across the apex of their curve. SPOs were performed at all levels that underwent interbody fusion. Included patients had at least one of the following: SVA>6cm, LL-PI mismatch>30, or PT>25. 7 patients were identified. 3 patients had preoperative and post-operative scoliosis films. Average pre-operative and post-operative spinopelvic parameters were measured.

Results: Average postoperative measurements was pelvic incidence (PI) 49.5±3.2°, pelvic tilt (PT) 18.3±5°, Lumbar lordosis (LL) 34.3±13°, C7 sagittal vertical axis (SVA) 30±33.9mm and coronal cob angle (CCA) 2.5±0.6°. Comparing pre- and postoperative scoliosis films showed an average reduction (CI=0.95) in PI by 18.3±12°, PT by 15.7±15°, and CCA by 16±11°. On the other hand, Lumbar lordosis showed an average improvement by 44.3±17°. Pre- and postoperative difference in C7-SVA measured 2±27 mm. Average follow up was 12±8 months. Complications included one patient with ureteral injury.

Conclusions: MIS-LIF combined with open posterior SPOs and instrumentation is a powerful tool for addressing adult degenerative deformity. Risks of combined approaches must be weighed against potential benefits including improved sagittal and coronal balance and improved fusion rates.

Patient Care: performing multilevel SPO and facetectomies and combining it with DLIF and long segment posterior fusion allows the surgeon to achieve good alignment results in adult patients with severe degenerative scoliosis

Learning Objectives: combining MIS lateral interbody fusion with posterior Smith-Peterson osteotomies (SPO) and posterior instrumentation will allow better improvement spinal alignment when compared to standard MIS interbody fusion combined with MIS posterior fusion

References: References 1. Deukmedjian AR, Ahmadian A, Bach K, Zouzias A, Uribe JS: Minimally invasive lateral approach for adult degenerative scoliosis: lessons learned. Neurosurgical Focus 35, 2013 2. Mummaneni PV, Shaffrey CI, Lenke LG, Park P, Wang MY, La Marca F, et al: The minimally invasive spinal deformity surgery algorithm: a reproducible rational framework for decision making in minimally invasive spinal deformity surgery. Neurosurgical Focus 36, 2014 3. Strom RG, Bae J, Mizutani J, Valone F, 3rd, Ames CP, Deviren V: Lateral interbody fusion combined with open posterior surgery for adult spinal deformity. J Neurosurg Spine:1-9, 2016