< PreviousAbstracts AnnualForum’19 40ANNUAL FORUM ’19 | LAS VEGAS, NEVADA | OCT. 31–NOV. 2, 2019 postop visit (VAS: 3 (0-9, SD 2.6), ODI: 37 (0-84, SD 22.8) and the final follow-up visit (VAS: 3 (0-8, SD 2.4), ODI: 30 (0-71, SD 21.7)) (p < .05). The mean preop radiographic parameters had a significant improvement in coronal Cobb angle (from 31.9 (10.4- 70) to 11.5(0-39.2), SVA (from 76.3 (9.6-201.8) to 45(0-146)), LL (from 38.5(8.3-75) to 49(23-88.2)) and PI/LL mismatch (from 18.6(0.5-60.4) to 9.8(0.1-28.9)) at the last postop (p<0.05). The rate of pseudoarthrosis, PJK, and other major complications was 5.2% (n=4), 5.2% (n=4) and 17.1% (n=13) respectively. Conclusions: Our study shows that strategic cMIS correction of spinal deformity can be safely performed in elderly patients, with a low rate of major complications and significant improvement in spinopelvic parameters and VAS and ODI scores at the last follow-up. This may suggest cMIS approach is an effective alternative to open surgery in elderly patients owning to a reduced operative footprint. Disclosures: N. Anand: B; Medtronics, Globus Medical, GYS Tech. C; Depuy Synthes, Stryker K2M. D; Medtronics, Globus Medical, Atlas Spine, Paradigm Spine, Theracell, GYS Tech, Bonovo. F; NuVasive, Medtronics, Globus. E. Nomoto: None. B. Khandehroo: None. S. Kahwaty: None. Paper #50: The Minimally Invasive Interbody Selection Algorithm for Spinal Deformity Praveen Mummaneni, MD 1 ; Christopher Shaffrey, MD 2 ; Robert Eastlack, MD 3 ; Juan Uribe, MD 4 ; Richard Fessler, MD 5 ; Leslie Robinson, MD 1 ; Joshua Rivera 1 ; Dean Chou, MD 1 ; Kai-Ming Fu, MD 6 ; Adam Kanter, MD 7 ; David Okonkwo, MD 7 ; Pierce Nunley, MD 8 ; Khoi Than, MD 2 University of California, San Francisco, San Francisco, CA 1 ; Duke University, Durham, NC 2 ; San Diego Spine Institute, San Diego, CA 3 ; Barrow Neurological Institute, Phoenix, AZ 4 ; Rush University Medical Center, Chicago, IL 5 ; Cornell University Medical Center, New York, NY 6 ; University of Pittsburgh Medical Center, Pittsburgh, PA 7 ; and Spine Institute of Louisiana, Shreveport, LA 8 Introduction: Multiple MIS interbody fusion options have been utilized as MIS deformity surgery has become more prevalent. However, at this time there is little guidance for approach selection for MIS deformity surgery. The minimally invasive interbody selection algorithm (MIISA) was created to provide a framework for rational decision making. Aims/Objectives: To develop an algorithm by experience MIS surgeons that can guide approach selection. Methods: A team of experienced spinal deformity surgeons developed the MIISA, incorporating the experience of a retrospective dataset from 223 MIS surgeries collected over a 5-year period. The algorithm leads to 1 of 4 interbody approach options (including ALIF, ACR, LLIF, and TLIF) that allow either indirect or direct decompression of the neural elements, possibly restore disc space and foraminal height, and may restore lordosis. The algorithm was developed by fellowship- trained spine surgeons experienced with spinal deformity surgery and validated with the retrospective MIS database. Results: Over a 5-year period, 11 surgeons completed 223 MIS deformity surgeries with 661 interbody devices. The database of these cases was reviewed and the type of interbody approach used at each level from L1-S1 was recorded. The surgeons were queried as to the reasons for their approach selection. The MIISA was then created with substantial agreement. The surgeons preferred lateral approaches for L1-L2 (95.6%), L2-L3 (88.0%), and L3-L4 (85.5%). They preferred lateral approaches at L4-L5 (70.7%), but this was muted by more use of TLIF and ALIF at that level. They preferred TLIF to ALIF at L5-S1 (63.4% vs. 36.6%). The increase in segmental lordosis at L2-L3 was significantly greater with LLIF than TLIF (4.6 vs. 1.4 degrees, p=0.029). The increase in segmental lordosis at L4-L5 was significantly greater with ALIF than LLIF or TLIF (9.2 vs. 5.3 vs. 0.8 degrees, p<0.001). The increase in segmental lordosis at L5- S1 was greater with ALIF than TLIF (5.3 vs. 1.9, p=0.011). Conclusions: The use of the MIISA provides consistent and straightforward guidance for surgeons who are considering an MIS approach for the treatment of patients with adult spinal deformity. The application of this algorithm could provide a platform for surgeons to achieve the desired goals of surgery. When these goals consist of maximizing lordosis, one should consider MIS LLIF at L2-L3 and ALIF at L4-L5, L5-S1; other interbody techniques are suitable if there is no need for increasing lordosis or disc height. Disclosures: P. Mummaneni: None. C. Shaffrey: None. R. Eastlack: None. J. Uribe: None. R. Fessler: None. L. Robinson: None. J. Rivera: None. D. Chou: None. K. Fu: None. A. Kanter: None. D. Okonkwo: None. P. Nunley: None. K. Than: B; Bioventus. CONCURRENT SESSION 8A: DEFORMITY & CERVICAL FREE PAPERSAbstracts AnnualForum’19 41ANNUAL FORUM ’19 | LAS VEGAS, NEVADA | OCT. 31–NOV. 2, 2019 Paper #51: A Prospective Analysis of Minimally Invasive Surgery for Adult Spinal Deformity: A Multicenter Study Gregory Mundis Jr., MD 1 ; Paul Park, MD2; Robert Eastlack, MD 1 ; Juan Uribe, MD 3 ; Stacie Tran 4 ; Kenyu Ito, MD 5 ; Pierce Nunley, MD 6 ; Michael Wang, MD 7 ; Richard Fessler, MD, PhD 8 ; Neel Anand, MD 9 ; Adam Kanter, MD 10 ; David Okonkwo, MD 10 ; and Christopher Shaffrey, MD 11 Scripps Clinic, San Diego, CA 1 ; University of Michigan, Ann Arbor, MI 2 ; Barrow Neurological Institute, Phoenix, AZ 3 ; San Diego Center for Spinal Disorders, San Diego, CA 4 ; Osaka City University, Osaka, Japan 5 ; Louisiana Spine Institute, Shreveport, LA 6 ; University of Miami, Miami, FL 7 ; Rush University Medical Center, Chicago, IL 8 ; Cedar Sinai, Los Angeles, CA 9 ; University of Pittsburgh Medical Center, Pittsburgh, PA 10 ; and Duke, Durham, NC 11 Introduction: Traditional surgery for adult spinal deformity (ASD) is effective but results in exposure- related morbidity. Minimally invasive spine surgery (MISS) can minimize this morbidity but high-level evidence for efficacy is lacking. This study presents the first prospective, multicenter investigation of MISS for ASD. Aims/Objectives: In patients with adult deformity, minimally invasive techniques result in significant radiographic and clinical improvement. Methods: Patients ≥18 years old with at least 1 of the following criteria were included: coronal curve (CC) ≥20°, SVA > 5cm, PT > 25°, thoracic kyphosis (TK) > 60. All patients had MIS surgery including interbody work: TLIF, LLIF, ALIF, ACR, and percutaneous posterior fixation. A total of 64 patients with a minimum of 1-year follow-up were included. Subgroup analysis of 28 with at least one Schwab ++ modifier was performed to evaluate those with more severe deformity (SD). Results: Mean age was 67.5 years. Mean levels instrumented was 4.3, estimated blood loss was (EBL) 366.5 mL, and length of stay (LOS) was 6.9 days. Significant (p<0.05) improvements in SVA (54 cm to 33.3 cm), PI-LL (13.6° to 6.3°), CC (22.9° to 15.5°) were observed. Significant (p<0.05) improvements in ODI (44.9 to 27.8), SRS (2.8 to 3.7), VAS back (7.1 to 2.8), and VAS leg (6 to 3.1) were noted. Complications occurred in 21 patients (32.8%): 13 (20.3%) were major, including 5 (7.8%) neurologic, with a 1-year reoperation rate of 15.6% (n=10). In SD patients (n=28), similar improvements in SVA (94.5 cm to 45.9 cm), PI-LL (25.6° to 9.5°), PT (26.9° to 22.7°), CC (20.4° to 12.8°), ODI (49.8 to 30.8), SRS-22 (2.8 to 3.5), VAS back (7.4 to 3.2), and VAS leg (5.8 to 3.7) were found (p<0.05). Mean age was 69.5 years and mean levels treated 5.1, EBL 464.6 mL, and LOS 7.8 days. Complications occurred in 14 (53.8%): 8 (28.6%) major, including 2 (7.1%) neurologic with 6 requiring a reoperation (21.4%) Conclusions: MIS for ASD resulted in meaningful symptomatic improvement. Complication rates are similar to historic norms with a fairly high reoperation rate at 1 year. Longer follow-up will be necessary to evaluate the durability of this approach in the treatment of adult deformity. Disclosures: G. Mundis Jr.: A; NuVasive. B; NuVasive, K2M. C; NuVasive, Depuy Synthes, Stryker K2M. F; Stryker K2M, NuVasive. P. Park: A; Pfizer, Vertex. B; Allosource, Globus, Medical Medtronic, NuVasive. F; Globus Medical. R. Eastlack: A; NuVasive. B; Aesculap, Baxter, Stryker K2M, NuVasive, SeaSpine, SI Bone, Titan. C; Radius. D; Alphatec, Carevature, Invuity, Nocimed, NuVasive, SeaSpine, Spine Innovations. F; Globus Medical, NuVasive, SeaSpine, SI Bone. J. Uribe: A; NuVasive. B; Misonix, NuVasive, SI Bone. C; NuVasive. D; NuVasive. F; NuVasive. S. Tran: None. K. Ito: None. P. Nunley: A; Styker K2M, Mesoblast, Organogenesis, Orthofix, Pfzier, Simplify, Spinal Kinetics, Spineology, Vertiflex, Zimmer Biomet. B; Camber Spine, Centinel Spine, Integrity Spine, Stryker K2M, Spineology, Vertiflex, Zimmer Biomet. C; Camber Spine, Stryker K2M, LDR Spine, Spineology. D; Amedica, Camber Spine, Paradigm Spine, Spineology. F; Camber Spine, Integrity Spine, LDR Spine. M. Wang: B; Depuy Synthes, Globus Medical, Stryker K2M, Spineology. C; CHLA, Depuy Synthes, Globus Medical. D; Innovative Surgical Devices. F; Depuy Synthes. R. Fessler: B; Depuy Synthes C; Benvenue. F; Depuy Synthes. N. Anand: B; Medtronic. C; Globus Medical, Medtronic. D; Atlas Spine, Globus Medical, GYS Tech, Medtronics, Paradigm Spine, Theracell. F; Globus Medical, Medtronic. A. Kanter: A; NuVasive. F; NuVasive, Zimmer Biomet. D. Okonkwo: B; NuVasive, Stryker K2M, Zimmer Biomet. F; Zimmer Biomet, NuVasive. C. Shaffrey: A; Depuy Synthes, Globus Medical, Medtronic, NuVasive. B; Medtronic, NuVasive, Zimmer Biomet. C; Medtronic, NuVasive. D; NuVasive. F; Medtronic, NuVasive, Zimmer Biomet. CONCURRENT SESSION 8A: DEFORMITY & CERVICAL FREE PAPERSAbstracts AnnualForum’19 42ANNUAL FORUM ’19 | LAS VEGAS, NEVADA | OCT. 31–NOV. 2, 2019 Paper #52: Treatment of Adult Scoliosis Fractional Curve with Minimally Invasive Surgery: Anterior Versus Posterior Approach? Robert Eastlack, MD 1 ; Dean Chou, MD 2 ; Juan Uribe, MD 3 ; Richard Fessler, MD 4 ; Khoi Than, MD 5 ; Stacie Tran 6 ; Paul Park, MD 7 ; Kai-Ming Fu, MD 8 ; Michael Wang, MD 9 ; Adam Kanter, MD 10 ; David Okonkwo, MD 10 ; Pierce Nunley, MD 11 ; Neel Anand, MD 12 ; Gregory Mundis, MD 1 ; Praveen Mummaneni, MD 2 ; and International Spine Study Group 13 Scripps Clinic, San Diego, CA 1 ; University of California, San Francisco, San Francisco, CA 2 ; Barrow Neurological Institute, Phoenix, AZ 3 ; Rush University Medical Center, Chicago, IL 4 ; Oregon Health & Science University, Portland, OR 5 ; San Diego Center for Spinal Disorders, San Diego, CA 6 ; University of Michigan, Ann Arbor, MI 7 ; Cornell University Medical Center, New York, NY 8 ; University of Miami, Miami, FL 9 ; University of Pittsburgh Medical Center, Pittsburgh, PA 10 ; Louisiana Spine Institute, Shreveport, LA 11 ; Cedar Sinai, Los Angeles, CA 12 ; and International Spine Study Group Foundation, Boulder, CO 13 Introduction: The fractional curve in adult scoliosis often causes radiculopathy and may be managed in varied manners with MIS deformity correction. There are inherent risks and benefits to anterior and posterior interbody reconstruction techniques, and the purpose of this study was to evaluate for differences in outcomes or complication rates by fractional curve treatment via MIS anterior vs. posterior IB fusion. Aims/Objectives: Anterior vs. posterior IB fusion when treating adult scoliosis fractional lumbosacral curves results in better outcomes and lower complication rates. Methods: Inclusion criteria were age ≥18 years, and 1 of the following: coronal cobb>20°, SVA>5cm, PT>20°, PI-LL >10°. Patients were treated with circumferential MIS (cMIS) surgery or hybrid MIS surgery and had 2-year minimum follow-up. Patient were divided into 2 groups: anterior or posterior interbody fusion at the lumbosacral junction (L4-S1). HRQOL measures included Oswestry Disability Index (ODI) and visual analog score (VAS). Results: A total of 112 patients who underwent MIS adult deformity surgery with minimum 2-year follow up were included. Of these, 74 patients underwent anterior and 38 patients underwent posterior interbody reconstruction at L4-S1 utilizing MIS technique. Preoperative spinopelvic parameters, radiographic parameters, and VAS were not different, but ODI was higher in the anterior group (53 vs 48, p=0.047). Complications and re-operation rates were not different between the 2 groups (p=0.089, p=0.597), but the posterior group had more infections (15.8% vs 2.7%, p=0.01). When subdivided for cMIS only surgery, 38 had anterior and 19 underwent posterior interbody fusions in the fractional curve. Pre- and postoperative VAS leg, ODI, and fractional curve magnitude were not different. In the anterior surgery cohorts, laminectomies at L4-S1 were performed in 22% of hybrid cases and in 8% of cMIS cases. Conclusions: Treatment of the fractional curve of adult scoliosis appears to be similarly effective in reducing VAS, ODI, and fractional curve magnitude regardless of anterior versus posterior approach. However, posterior interbody reconstruction was associated with higher infection rate than the anterior approach, regardless of application in cMIS or hybrid technique. Disclosures: R. Eastlack: A; NuVasive. B; Aesculap, Baxter, Stryker K2M, NuVasive, SeaSpine, SI Bone, Titan. C; Radius. D; Alphatec, Carevature, Invuity, Nocimed, NuVasive, SeaSpine, Spine Innovations. F; Globus Medical, NuVasive, SeaSpine, SI Bone. D. Chou: B; Globus Medical, Medtronic. F; Globus Medical. J. Uribe: A; NuVasive. B; Misonix, NuVasive, SI Bone. C; NuVasive. D; NuVasive. F; NuVasive. R. Fessler: B; Depuy Synthes. C; Benvenue. F; Depuy Synthes. K. Than: B; Bioventus. S. Tran: None. P. Park: A; Pfizer, Vertex. B; Allosource, Globus, Medical Medtronic, NuVasive. F; Globus Medical. K. Fu: B; SI Bone. M. Wang: B; Depuy Synthes, Globus Medical, Stryker K2M, Spineology. C; CHLA, Depuy Synthes, Globus Medical. D; Innovative Surgical Devices. F; Depuy Synthes. A. Kanter: A; NuVasive. F; NuVasive, Zimmer Biomet. D. Okonkwo: B; NuVasive, Stryker K2M, Zimmer Biomet. F; Zimmer Biomet, NuVasive. C. P. Nunley: A; Stryker K2M, Mesoblast, Organogenesis, Orthofix, Pfzier, Simplify, Spinal Kinetics, Spineology, Vertiflex, Zimmer Biomet. B; Camber Spine, Centinel Spine, Integrity Spine, Stryker K2M, Spineology, Vertiflex, Zimmer Biomet. C; Camber Spine, Stryker K2M, LDR, Spineology. D; Amedica, Camber Spine, Paradigm Spine, Spineology. F; Camber Spine, Integrity Spine, LDR Spine. N. Anand: B; Medtronic. C; Globus Medical, Medtronic. D; Atlas Spine, Globus, GYS Tech, Medtronics, Paradigm Spine, Theracell. F; Globus Medical, Medtronic. G. Mundis: A; NuVasive. B; NuVasive, Stryker K2M. C; Depuy Synthes, NuVasive, Stryker K2M. F; Stryker K2M, NuVasive. P. Mummaneni: A; NREF. B; Depuy Synthes, Globus Medical, Stryker K2M. C; AOSpine, SpineArt. D; Spinicity. F; Depuy Synthes. I. Study Group: A; Allosource, Depuy Synthes, Globus Medical, Stryker K2M, Medtronic, NuVasive, Orthofix. CONCURRENT SESSION 8A: DEFORMITY & CERVICAL FREE PAPERSAbstracts AnnualForum’19 43ANNUAL FORUM ’19 | LAS VEGAS, NEVADA | OCT. 31–NOV. 2, 2019 Paper #53: Does ACR Result in Greater Morbidity Than LLIF Alone When Treating Adult Spinal Deformity? Robert Eastlack, MD 1 ; Juan Uribe, MD 2 ; Richard Fessler, MD, PhD 3 ; Khoi Than, MD 4 ; Stacie Tran 5 ; Dean Chou, MD 6 ; Paul Park, MD 7 ; Kai-Ming Fu, MD 8 ; Michael Wang, MD 9 ; Adam Kanter, MD 10 ; David Okonkwo, MD 10 ; Pierce Nunley, MD 11 ; Neel Anand, MD 12 ; Praveen Mummaneni, MD 6 ; Gregory Mundis Jr., MD 1 ; and International Spine Study Group 13 Scripps Clinic, San Diego, CA 1 ; Barrow Neurological Institute, Phoenix, AZ 2 ; Rush University Medical Center, Chicago, IL 3 ; Oregon Health & Science University, Portland, OR 4 ; San Diego Center for Spinal Disorders, San Diego, CA 5 ; University of California, San Francisco, San Francisco, CA 6 ; University of Michigan, Ann Arbor, MI 7 ; Cornell University Medical Center, New York, NY 8 ; University of Miami, Miami, FL 9 ; University of Pittsburgh Medical Center, Pittsburgh, PA 10 ; Louisiana Spine Institute, Shreveport, LA 11 ; Cedar Sinai, Los Angeles, CA 12 ; and International Spine Study Group Foundation, Boulder, CO 13 Introduction: Anterior column realignment (ACR) can be utilized for correction of adult spinal deformity (ASD), but the additional benefit over lateral lumbar interbody fusion (LLIF) alone is unclear. Aims/Objectives: CR for correction of adult spinal deformity results in similar complication rates while achieving spinopelvic parameter goals when compared to LLIF. Methods: Inclusion criteria were age ≥18 years, and 1 of the following: coronal cobb>20°, SVA>5cm, PT>20°, PI-LL >10°. Patients were treated with circumferential MIS (cMIS) surgery or hybrid MIS surgery and had 1-year minimum follow-up. HRQOL (Oswestry Disability Index (ODI), visual analog score (VAS), SRS- 22) and spinopelvic parameters were captured. Results: A total of 127 patients met inclusion criteria: 101 underwent LLIF and 26 had ACR. Average age and BMI were 66.3 years and 67.8 kgm2, respectively (p=0.654 and p=0.957). The groups had similar rates of prior spine surgery (48.5% vs. 57.7%; p=0.403), cMIS (58.7% vs. 73.1%; p=0.222), posterior osteotomies (43.6% vs. 34.6%; p=0.409), levels instrumented (7.8 vs. 8; p=0.895), and interbody fusion levels (3.4 vs. 3.6; p=0.478). Preop (PT: 23.6/26.3; p=0.373, SVA: 77.6/54.6mm; p=0.151, PI-LL: 17.3/20; p=0.692) and postop spinopelvic parameters were similar between groups, except for postop SVA which was higher in the LLIF group (40 mm vs. 13 mm; p=0.028). One-year PI-LL (3.8 vs. 5.8; p=0.555), PT (20.6 vs. 22.9; p=0.536), and SVA were normalized in both groups. Preop and postop ODI, VAS, and SRS -22 scores were similar between groups. Complication rates between groups were similar as well (57.4% LLIF vs. 57.7% ACR; p=0.98), including neurologic (16.8% vs. 15.4%; p=0.859) and vascular (0% for both groups) injuries. Conclusions: Use of ACR via lateral approach for correction of adult spinal deformity results in no increase in neurologic, vascular, or other overall complications rates, when compared to using LLIF alone. Optimization of spinopelvic parameters was achieved regardless of the technique employed. Segmental radiographic changes were not specifically evaluated, but regional and global parameters were not differentially impacted when comparing ACR and LLIF impact. Disclosures: R. Eastlack: A; NuVasive. B; Aesculap, Baxter, Stryker K2M, NuVasive, SeaSpine, SI Bone, Titan. C; Radius. D; Alphatec, Carevature, Invuity, Nocimed, NuVasive, SeaSpine, Spine Innovations. F; Globus Medical, NuVasive, SeaSpine, SI Bone. J. Uribe: A; NuVasive. B; Misonix, NuVasive, SI Bone. C; NuVasive. D; NuVasive. F; NuVasive. K. Than: B; Bioventus. S. Tran: None. D. Chou: B; Globus Medical, Medtronic. F; Globus Medical. P. Park: A; Pfizer, Vertex. B; Allosource, Globus, Medical Medtronic, NuVasive. F; Globus Medical. K. Fu: B; SI Bone. M. Wang: B; Depuy Synthes, Globus Medical, Stryker K2M, Spineology. C; CHLA, Depuy Synthes, Globus Medical. F; Depuy Synthes. A. Kanter: A; NuVasive. F; NuVasive, Zimmer Biomet. D. Okonkwo: B; NuVasive, Stryker K2M, Zimmer Biomet. F; Zimmer Biomet, NuVasive. P. Nunley: A; Stryker K2M, Mesoblast, Organogenesis, Orthofix, Pfzier, Simplify, Spinal Kinetics, Spineology, Vertiflex, Zimmer Biomet. B; Camber Spine, Centinel Spine, Integrity Spine, Stryker K2M, Spineology, Vertiflex, Zimmer Biomet. C; Camber Spine, Stryker K2M, LDR, Spineology. D; Amedica, Camber Spine, Paradigm Spine, Spineology. F; Camber Spine, Integrity Spine, LDR Spine. N. Anand: B; Medtronic. C; Globus Medical, Medtronic. D; Atlas Spine, Globus, GYS Tech, Medtronics, Paradigm Spine, Theracell. F; Globus Medical, Medtronic. P. Mummaneni: A; NREF. B; Depuy Synthes, Globus Medical, Stryker K2M. C; AOSpine, SpineArt. D; Spinicity. F; Depuy Synthes. G. Mundis Jr.: A; NuVasive. B; NuVasive, Stryker K2M. C; Depuy Synthes, NuVasive, Stryker K2M. F; Stryker K2M, NuVasive. I. Study Group: A; Allosource, Depuy Synthes, Globus Medical, Stryker K2M, Medtronic, NuVasive, Orthofix. Paper #54: Coronal Balance in Degenerative Scoliosis Treated with Minimally Invasive Spinal Deformity Surgery: Are We Leaning in the Right Direction? Corey Walker, MD; Jakub Godzik, MD; Ifije Ifije Ohiorhenuan, MD, PhD; Clinton Morgan, MD; Jay Turner, MD,PHD; and Juan Uribe, MD Barrow Neurological Institute, Phoenix, AZ Introduction: Minimally invasive spine surgery (MIS) techniques have been demonstrated to improve back pain and radiculopathy in patients with degenerative scoliosis while concomitantly increasing lordosis and addressing sagittal plane deficits. However, it remains unclear how they affect coronal plane balance. CONCURRENT SESSION 8A: DEFORMITY & CERVICAL FREE PAPERSAbstracts AnnualForum’19 44ANNUAL FORUM ’19 | LAS VEGAS, NEVADA | OCT. 31–NOV. 2, 2019 Aims/Objectives: The goal of this study is to examine how MIS spine deformity surgery affects coronal balance. Methods: A single-institution retrospective radiographic evaluation of patients with degenerative scoliosis treated with MIS approaches was performed. Patients’ coronal balance was categorized pre-operatively and at 1 year post-operatively according to the Qui classification as A (coronally balanced), B (C7-central sacral vertical line distance (C7CSVL) >3cm towards the concavity of the major lumbar curve) or C (>3cm towards the convexity) (Bao et al., 2016). Pelvic obliquity, coronal cobb of the major curve, the fractional curve (L4 to S1) and proximal secondary curve were measured and compared as well. Results: 29 patients were treated with MIS approaches, 14 with dextroscoliosis, 15 with levoscoliosis, and median curve apex at the L2/L3 disc space. 13 patients (45%) were imbalanced pre-operatively, with 5 as B type and 8 as C type. All coronally balanced patients (A type) remained in balance post-operatively, except for one patient who worsened to C. 4 out of 5 B patients and 4 out of 8 C patients improved to A with surgical intervention. As a whole, C7SVL was not statistically different pre- and post-operatively (2.3 vs 1.9, p=0.31). However, significant improvements in the major curve (28.6° vs 15.6°, p<0.001), fractional curve (12.9° vs 7.7°, p<0.01) and secondary curve (16.3° vs 9.9°, p<0.01) were all seen. There was no change in the pelvic obliquity (p=0.84). 8 patients had worsening of their coronal balance with greater than 1.0 cm increase in their C7SVL. Compared to the patients that improved or stayed the same, these patients had similar proportional improvements in their primary curve cobb (38.4% vs 47%, p=0.29), similar proportions of patients receiving anterior lumbar interbody placement at L5/S1 (50% vs 57%, p=0.75), but significantly less improvement in their fractional curves (19.7% vs 39.0%, p=0.04). Conclusions: MIS deformity surgery in patients with adult degenerative scoliosis decreases coronal cobb angles and fractional curves, and is successful at treating coronal imbalance in the majority of patients. Patients with C type imbalance remain more difficult to treat. In patients who had worsened coronal balance with surgery, failure to improve the fractional curve was partially responsible. Disclosures: C. Walker: None. J. Godzik: None. I. Ifije Ohiorhenuan: None. C. Morgan: None. J. Turner: B; Nuvasive, SeaSpine. J. Uribe: B; Nuvasive, SI Bone, Misonix. F; Nuvasive. Paper #55: Radiographic and Surgical Outcome Analysis of Lenke 1a Adolescent Idiopathic Scoliosis Correction: Open Vs. Minimally Invasive Matthew Geck, MD; Devender Singh, PhD; Eeric Truumees, MD; and John Stokes, MD Seton Spine and Scoliosis Center, Austin, TX Introduction: Both open and minimally-invasive surgery (MIS) techniques are used to surgically address adolescent idiopathic scoliosis (AIS). MIS techniques are purported to preserve the midline spinal musculature and to decrease estimated blood loss (EBL) and hospital length of stay (LOS). Aims/Objectives: To compare the surgical outcomes and deformity corrections achieved in matched cohorts of AIS patients with similar Lenke type that had undergone either open or minimally-invasive surgery (MIS). Methods: From a single surgeon’s practice, 18 patients who underwent MIS correction were matched with 23 patients that had open surgical correction. All were idiopathic Lenke 1A. Age, surgery duration, EBL, LOS, preoperative (preop) and postoperative (postop) Cobb angles, Oswestry Disability Index (ODI), Visual Analogue Scale (VAS), and Scoliosis Research Society-22r (SRS-22r) were evaluated. Mann-Whitney U test was conducted for statistical significance ( α =0.05). Results: Mean patient age was 15 years in MIS and 17 years in open surgical groups. Mean preop Cobb angles for MIS and open were 53.1±4.6° and 57.7±5.8°, respectively. The main curve’s mean flexibility index was 53.1% and 55.2% for MIS and open, respectively. Mean surgical time for MIS and open were 324 minutes and 354 minutes, respectively (p=0.005). Mean EBL were 143±85.1 mL and 253±71.2 mL for MIS and open, respectively (p=0.003). Mean LOS for MIS was 3.4±0.6 days and 4.7±0.8 days for open (p=0.006). Mean corrections for MIS at postop 6 months, 1 and 2 years were 74.5±7.4%, 75.8±7.8%, and 76.5±7.4%, respectively. For open, these corrections were 75.8±5.3%, 77.1±7.6%, and 76.7±8.4%, respectively. The differences in correction did not reach statistical significance. Mean preop, 6 months, 1 and 2 years postop VAS scores for MIS and open were 2.5 and 3.7; 1.5 and 3.1 (p=0.03); 1.2 and 2.7 (p=0.034); 1.1 and 2.0, respectively. For MIS and open, mean preop, 6 months, 1 and 2-years postop ODI scores were 14.1 and 19.2; 9.7 and 15.7 (p=0.04); 7.3 and 13.2 (p=0.043); 4.6 and 9.7, respectively. Mean SRS-22r at 6 month, 1 and 2 years for MIS and open were 3.8 and 3.4; 4.3 and 4.1; and 4.6 and 4.2, respectively. CONCURRENT SESSION 8A: DEFORMITY & CERVICAL FREE PAPERSAbstracts AnnualForum’19 45ANNUAL FORUM ’19 | LAS VEGAS, NEVADA | OCT. 31–NOV. 2, 2019 Conclusions: In these specific curve types, our cohort data indicates that MIS technique for scoliosis correction is a viable option and can attain corrections equivalent to open surgery with lower EBL and shorter LOS. Additionally, patient reported outcomes over 2 years follow-up, as indicated by VAS, ODI and SRS-22r were comparatively better in the MIS over the open group. Disclosures: M. Geck: D; DiFusion. F; Genesys Spine. D. Singh: None. E. Truumees: A; Pfizer, Relievant Medsystems, Stryker K2M, Medtronic. B; North American Spine Society. D; Doctoral Research Group. F; Stryker K2M. J. Stokes: D; DiFusion, Summit Medventures. F; Genesys Spine. Paper #56: Minimally Invasive Surgical Technique for Treatment of Cervical Spondylolytic Myelopathy and Radiculopathy Reginald Knight 1 ; Frank Barber, PAC 1 ; ScottGrainger, BSRN 1 ; Melissa Scribani, PhD 2 ; and Nicole Krupa, MS 2 BassettSpine Care Institute, Cooperstown, NY 1 and BassettStatistical Center, Cooperstown, NY 2 Introduction: Surgical treatment of cervical radiculopathy and myelopathy include both anterior and posterior approaches. Traditional open posterior methods are associated with increased blood loss, infection rates, and may require fusion. Are expected outcomes significantly different between these two pathologic groups? Aims/Objectives: Report our experience using minimally invasive surgical technique (MIST) for treatment of cervical radiculopathy and myelopathy Methods: Data points were collected preop, and 1, 4, 10, and 24 months postop on 41 consecutive patients with complaint divided into unilateral radiculopathy (R-24) and myelopathy (M-17) treatment with posterior tubular decompression. Perioperative demographics and PRFO (VAS - Neck, VAS - Arm, and ODI-Neck) are reported. IRB protocols were followed and statistical analysis via student t-test. Myelopathy patients with fixed focal cervical kyphosis were excluded from the study. Results: A total of 41 patients were included in the study: 29 male, 12 female [M-13m, 4f: R-16m, 8f]; mean age 66 years [M-66, R-57, p=0.008]; LOS 0.5 days [M-0.5, R-0.4; range 0-3, NS], levels decompressed 1.6 [M-2.1, R-1.2, p=0.000], ORT 121 minutes [M-133, R-113, NS], EBL 33 mL [M-41, R-28, NS], and Fluoro time 26 sec [M-22, R-30, NS]. All patients discharged home. The myelopathy group had two readmissions and 1 revision surgery [persistent C5 radiculopathy]. Significant improvement were seen the total cohort in PHQ9 [pre=7.3, 24 mos=3.0], neck [pre=63, 24 mos=41] and arm pain [pre=60, 24 mos=36]. In the myelopathy group, significant improvement was seen in PHQ9 [pre=8.8, 24 mos=4.3]. In the radiculopathy group, significant improvement was seen in PHQ9 [pre=6.2, 24 mos=1.0], neck [pre=61, 24 mos=24] and arm pain [pre=61, 24 mos=31]. Neither group reported significant changes in neck disability index preop to 24 months. Conclusions: Posterior tubular decompression for the treatment of cervical myelopathy and or radiculopathy is accomplished safely in an outpatient environment as illustrated by documented perioperative demographics. While patient subcategories, myelopathy or radiculopathy, are distinctly different as noted by their PRFO and extent of surgical decompression required, meaningful changes in radiculopathy group were more dramatic—neck pain, arm pain, and anxiety index—compared with the myelopathy group. Disclosures: R. Knight: None. F. Barber: None. S. Grainger: None. M. Scribani: None. N. Krupa: None. Paper #57: Therapeutic Comparison of Endoscopic Spine Surgery Versus Anterior Cervical Decompression and Fusion for Cervical Spondylotic Myelopathy Xifeng Zhang, Dr. Chinese PLA General Hospital, Beijing, China Introduction: Controversy still exists among spine surgeons regarding the endoscopic spinal surgery to be used for the treatment of multilevel cervical spondylotic myelopathy (CSM). Aims/Objectives: Compare the clinical efficacy of endoscopic spinal surgery with anterior cervical decompression and fusion in the treatment of CSM. Methods: Data on a total of 46 CSM patients treated with endoscopic spine surgery or anterior cervical decompression and fusion were collected. The patients were divided into spinal endoscopy group and the anterior cervical decompression and fusion group (ACDF group), according to the operation methods. The operation time (ORT), mean blood loss, and length of hospitalization stay (LOS) of the 2 groups were recorded and compared. Japanese Orthopedic Association (JOA) score were recorded. The differences of JOA score at preoperative and postoperative time points were analyzed. CONCURRENT SESSION 8A: DEFORMITY & CERVICAL FREE PAPERSAbstracts AnnualForum’19 46ANNUAL FORUM ’19 | LAS VEGAS, NEVADA | OCT. 31–NOV. 2, 2019 Results: The mean ORT and LOS were significantly shorter in the spinal endoscopy group ( (70.23±10.91 minutes and 4.23±1.11 days) than that in the ACDF group ( (92.29 ±13.13 minutes, 8.21±1.50days) (p<0.05). The mean intraoperative blood loss was significantly less in the spinal endoscopy group (30.00±7.30 mL ) than that in the ACDF group ( (132.38 ±14.33 mL) (p<0.05). There were no significant differences in the JOA score before operation (9.76±0.97 vs 9.63±1.06), 3 months (13.47±0.71 vs 13.54±0.63) and 1 year (14.25±0.61 vs 14.40± 0.64) after operation between the spinal endoscopy group and the ACDF group (p>0.05). The JOA score 3 months and 1 year after operation were significantly higher than those before operation in both groups, and there was no significant difference in the JOA score 3 months and 1 year after operation (p>0.05). The improvement rate at 3 months (51.52±5.86% vs (53.16±4.54% ) and 1 year (62.00±7.82% vs 65.11±5.02%) after operation in the spinal endoscopy group was no significantly difference compared to those in the ACDF (p>0.05). The excellent rate of clinical efficacy evaluation was not significantly different between the spinal endoscopy group (81.8%) and the ACDF group (83.3%) (p>0.05). Conclusions: Spinal endoscopic surgery was significantly superior to anterior cervical decompression and fusion in reducing operation time, intraoperative blood loss, and length of hospitalization stay. Disclosures: X. Zhang: None. Paper #58: Can Multilevel Standalone Cervical Fusion Replace Multilevel Plating in Outpatient Setting Fabio Pencle and Kingsley Chin, MD LESS Institute, Hollywood, FL Introduction: Multilevel anterior cervical decompression and fusion (ACDF) methods can be subdivided into several different methods including ACDF using tricortical autograft and plate fixation (ACDF-AP), ACDF using stand-alone cage (ACDF-CA), and ACDF using cage and plate fixation (ACDF-CP). Aims/Objectives: The authors aim to demonstrate the use of standalone cages in multilevel ACDF. Methods: A retrospective review of prospectively collected data of 37 patients who had multilevel ACDF-CA compared to a historical cohort of 32 patient with multilevel ACDF-CP. Outcomes assessed where Visual Analog Scale (VAS) scores, Neck Disability Index (NDI), and fusion rate. Results: Of the 37 patients in Group 1 (ACDF-CA), 67% were female , mean age was 52.8+/- 8.9 years, and mean BMI 30.6+/- 7.1 kg/m2. Of the 32 patients in Group 2 (ACDF-CP), 78% were female, mean age was 55.7+/- 7.6 years, and mean BMI 32.1+/- 6.4 kg/m2. No statistical differences in gender, age, or BMI were found between groups (p=0.843, 0.691 and 0.947 respectively). There was no significance between preoperative VAS neck, arm, and NDI scores between Groups 1 and 2 (p=0.520, 0.83 and 0.43 respectively). Analysis of 1-year follow-up demonstrated that Group 1 mean preoperative VAS neck scores improved from 8.5+/-1.3 to 0.8+/-0.1 (p<0.001), preoperative VAS arm scores improved from 6.1+/-1.9 to 1.1+/- 0.7 (p<0.001), and preoperative mean NDI scores decreased from 33.6+/-3.7 to 11.6+/-1.3 (p<0.001). In Group 2, mean preoperative VAS neck scores improved from 8.8+/-1.0 to 1.5+/-0.3 at one-year follow-up (p=0.001), preoperative VAS arm scores improved from 6.7+/- 1.6 to 1.6+/-0.2, (p<0.001), and preoperative mean NDI reduced from 35.8+/-2.5 to 12.8+/-1.7 (p=0.001). One- hundred percent fusion was achieved in both groups, with Group 1 demonstrating a sentinel sign as early as 6 months Conclusions: This study demonstrated that multi-level standalone fusion is feasible in the outpatient setting and can replace a multi-level cage and plating in the cervical spine. Disclosures: F. Pencle: None. K. Chin: D; KICVentures. Paper #59: Does Improved Radiographic Alignment Truly Enhance Dynamic Functional Balance? Ram Haddas, PhD; Damon Mar, PhD; Isador Lieberman, MD Texas Back Institute, Plano, TX Introduction: Adult degenerative scoliosis (ADS) represents a significant healthcare burden with exceedingly high and increasing prevalence, particularly among the elderly. Radiographic alignment measures and patient-reported outcomes currently serve as the standard means to assess spinal alignment, deformity, and stability. Neurological examinations have served as qualitative measures for indicating muscle strength, motor deficits, and gait abnormalities. Three-Dimensional motion analysis is increasingly being used to identify and measure gait and balance instability. Recently, techniques have been established to quantify balance characteristics described by Dubousset as the “cone of economy” (CoE). The relationship between radiographic alignment parameters and CoE balance measures of ADS patients before and after realignment surgery is currently CONCURRENT SESSION 8A: DEFORMITY & CERVICAL FREE PAPERSAbstracts AnnualForum’19 47ANNUAL FORUM ’19 | LAS VEGAS, NEVADA | OCT. 31–NOV. 2, 2019 unknown. Aims/Objectives: To establish the relationship between radiographic alignment parameters and functional CoE measurements at one week before and at three months after realignment surgery in ADS patients Study Design: Prospective, concurrent-cohort study. Patient sample: 29 ADS patients treated with realignment surgery. Methods: Patients were evaluated at one week before realignment surgery and at their three-month follow-up examination. During each evaluation, patients completed self- reported outcomes (visual analog scales for pain, Oswestry Disability Index, SRS22r) and a functional balance test. Mean changes in dependent measures from before to after surgery were compared using paired t-tests. Pearson correlations were used to test for significant correlations between changes in radiographic and CoE measures. Results: Significant improvements were found for all patient- reported outcomes, in several radiographic measures, and in CoE measures. Improvements of scoliosis Cobb angle, coronal pelvic tilt, lumbar lordosis, and thoracic kyphosis showed significant correlations with CoE sway and total distance measures at both the center of mass and center of the head. Conclusions: Improved radiographic alignment measures significantly correlated with improved CoE balance measures among ADS patients treated with realignment surgery at their three-month follow-up. These findings indicate that functional balance evaluations when used in conjunction with radiographic measurements, may provide a more robust and improved patient-specific sensitivity for postoperative assessments. CoE balance may represent a new measure of added value for surgical intervention of ADS. Disclosures: R. Haddas: A; Medtronic Inc., SI-Bone Inc., Aspen Medical Products, Cervical Spine Research Society. D. Mar: None. I. Lieberman: None. Paper #60: The Effect of Duration of Symptoms on Clinical Outcomes Following Anterior Cervical Discectomy and Fusion James M. Parrish, MPH; Nathaniel W. Jenkins, MS; Thomas Brundage, BS; Nadia Hrynewycz, BS; Joon Yoo, BA; and Kern Singh, MD Rush University Medical Center, Chicago, IL Introduction: Anterior cervical discectomy and fusion (ACDF) has proven successful in treating degenerative cervical spine disease. However, there is no consensus on appropriate nonoperative treatment options. Further, there is a paucity of literature regarding the influence of preoperative symptom duration on patient-reported outcomes (PROs) following ACDF. Aims/Objectives: The purpose of this study is to examine whether the time spanning from symptom onset to operative treatment has an effect on postoperative clinical improvement in patients undergoing anterior cervical discectomy and fusion (ACDF). Methods: Patients who underwent primary, single-level ACDF were retrospectively reviewed and stratified according to preoperative symptom duration (<12 months and greater than or equal to 12 months). Demographic and perioperative characteristics were compared using Chi-squared analysis and linear regression. Differences in PRO scores, including Neck Disability Index (NDI), Visual Analogue Scale (VAS) neck pain, VAS arm pain, and 12-Item Short-Form Physical Component Score (SF-12 PCS), at each postoperative time point were compared using linear regression. Achievement of minimal clinically important difference (MCID) for PROs was compared using Chi-square analysis. Results: In total, 115 patients underwent primary, single-level ACDF and were included in the study. Of these, 77 had a DOS <12 months and 38 had a DOS greater than or equal to 12 months. When comparing PROs preoperatively, the shorter DOS cohort had significantly worse VAS arm pain. However, there was no preoperative difference in NDI, VAS neck pain, and SF-12 PCS. In the postoperative period, there were no significant differences in improvement of PROs through the 12-month time point. The shorter DOS cohort had a comparable number of patients achieving MCID for NDI, VAS neck pain, VAS leg pain, and SF-12 PCS. Conclusions: This investigation assessed the influence of preoperative DOS in patients undergoing a primary, single- level ACDF. Patients with DOS shorter than 12 months exhibited significantly worse VAS arm pain scores at the time of surgery. CONCURRENT SESSION 8A: DEFORMITY & CERVICAL FREE PAPERSAbstracts AnnualForum’19 48ANNUAL FORUM ’19 | LAS VEGAS, NEVADA | OCT. 31–NOV. 2, 2019 However, these patients demonstrated similar clinical outcomes postoperatively regardless of preoperative symptom duration. Our findings suggest that delayed surgical intervention may not necessarily lead to impaired functional recovery in patients with degenerative cervical disease. Disclosures: J. Yoo: None. N. Jenkins: None. J. Parrish: None. T. Brundage: None. N. Hrynewycz: None. K. Singh: A; Cervical Spine Research Society. B; Zimmer Biomet, Stryker K2M. D; Avaz Surgical, Vital 5, Minimally Invasive Spine Study Group. F; Zimmer Biomet, Stryker K2M, RTI Surgical, Lippincott Williams & Wilkins, Thieme, Jaypee Publishing, Slack Publishing. Paper #61: Outcomes and Predictors of Failure to Improve Following Unilateral Laminotomy with Bilateral Decompression Michael Schallmo, BS; Ziyad Knio, BS; Wesley Hsu, MD; Benjamin Corona, PhD; Justin Lackey, BS; Alejandro Marquez-Lara, MD; T. David Luo, MD; Suman Medda, MD; Bradley Wham, MD; Tadhg O'Gara, MD Wake Forest School of Medicine, Winston-Salem, NC Introduction: With the emergence of tubular retractor systems, less invasive techniques that minimize trauma to paraspinal musculoligamentous structures, such as unilateral laminotomy with bilateral decompression (ULBD), have become increasingly used for the management of recalcitrant lumbar spinal stenosis (LSS). However, there is a paucity in the evidence- based literature regarding trends in and predictors of clinical outcomes over time following ULBD. Aims/Objectives: The purpose of this study was to assess factors that may predict failure to improve at 12- and 24-months following ULBD for the management of LSS. Methods: A database of 255 consecutive microdecompression surgeries performed by a single surgeon between 2014- 2018 was queried. Inclusion criteria were patients at least 18 years of age with symptomatic LSS who failed non-operative management and subsequently underwent primary, single- level ULBD. Outcomes included visual analog scale (VAS) for back pain and leg pain, and Oswestry Disability Index (ODI), which were collected preoperatively and at 12- and 24-months postoperative. Patient characteristics, radiographic findings, operative factors, and intraoperative findings were assessed for associations with failure to improve. The threshold for clinically important improvement was defined as reaching or surpassing the previously established minimum clinically important difference for ODI (12.8) and not requiring revision. Results: A total of 68 patients were included. Preoperative values for back pain, leg pain, and ODI (7.32, 7.53, and 51.22, respectively) showed significant improvements upon follow- up at 12-months (2.89, 2.23, 22.40, respectively; p<0.001) and 24-months (2.80, 2.11, 20.32, respectively; p<0.001). A total of 50 patients (73.5%) demonstrated clinically important improvement after ULBD based on the defined criteria. Of the 18 patients who failed to improve, 12 required revision (6 fusions, 6 tubular decompressions). Independent predictors of failure to improve included female sex (adjusted odds ratio=5.06, 95% confidence interval [1.49-21.12]; p=0.014) and current smoker status (adjusted odds ratio=5.39, 95% confidence interval [1.39-23.97]; p=0.018). Conclusions: Patients in this study who underwent ULBD demonstrated clinically important improvement that was maintained over a 24-month follow-up period. Poorer outcomes were associated with female sex and current tobacco smoker status. Disclosures: M. Schallmo: None. Z. Knio: None. W. Hsu: None. B. Corona: None. J. Lackey: None. A. Marquez-Lara: None. T. Luo: None. S. Medda: None. B. Wham: None. T. O'Gara: None. CONCURRENT SESSION 8A: DEFORMITY & CERVICAL FREE PAPERSAbstracts AnnualForum’19 49ANNUAL FORUM ’19 | LAS VEGAS, NEVADA | OCT. 31–NOV. 2, 2019 CONCURRENT SESSION 8B: LATERAL, BIOLOGICS & HEALTHCARE ECONOMICS FREE PAPERS Paper #62: Lateral Access Window for ALIF at L5-S1: Anatomical Measurements to Aid Safety and Feasibility Brian Kwon, MD New England Baptist Hospital, Boston, MA Introduction: Lateral surgery has previously been limited to L4-5 and above. Anterior lumbar interbody fusion (ALIF) at L5-S1 is increasingly performed. When combined with lateral fixation, savings in operative time, cost, and patient-burden has been shown. Like any new technique, without proper guidance on which patients are anatomically amenable to lateral L5- S1 ALIF, early efforts can be marred by technical failures and complications. A new pelvic dimension defines a Lateral Access Window (LAW) and indicates whether lateral access to L5-S1 is feasible. The LAW-entry point (EP) is a straight line from the L5-S1 disc to the LAW and determines ease of access to L5- S1. Other factors that surgeons examine, such as major vessel position and pelvic geometry, were also considered. Aims/Objectives: Our goal was to describe the LAW and provide surgeons with radiographic measurements to aid the decision to pursue lateral ALIF at L5-S1 Methods: All patients underwent lateral ALIF at L5-S1 by a single spine and vascular surgeon team. Lateral lumbar radiographs were used to measure the LAW, which is a line from the anterior superior iliac spines to the top of the pubis. A line from the L5-S1 disc intersects the LAW line is the entry point (LAW-EP). This is expressed as a ratio; for example, 0.25 is the cranial 1/4th of the LAW. Axial MRI at L5-S1 was used to measure bifurcation distance, left common iliac vein (LCIV) distance from midline, and obliquity of the LCIV. Results: A total of 22 patients underwent L5-S1 lateral ALIF without complications. The LAW averaged 9.5 cm. The LAW- EP averaged 0.29 (i.e. the cranial 30% of the LAW). Pelvic incidence (PI) was highly correlated with the LAW-EP, r2=0.81 (p<0.0001). We divided our sample into 2 groups: LAW-EP <1/3 and LAW-EP >1/3. We found significant differences in PI (43 vs. 60 respectively; p,0.05), SS (30 vs. 40, p,0.05), and PT (14 vs. 20, p<0.05) between the groups. There were no differences between groups in bifurcation distance (3.0 vs. 3.5 cm, p=0.35), LCIV distance from midline, and obliquity of LCIV. Conclusions: LAW is a novel radiographic measurement that can aid surgeons’ decision making to pursue lateral L5-S1 ALIF. If LAW cannot be measured, high correlation with PI supports use of PI <50 as a reasonable cutoff. Bifurcation distance, LCIV position, and obliquity were found not to be significantly different. LAW-EP <0.33 and PI <50 can help the early experience, safety, and success of lateral ALIF at L5-S1. Disclosures: B. Kwon: B; NuVasive. C; NuVasive. Paper #63: Comparative Effectiveness of Adjustable Lordotic Expandable Versus Static Lateral Lumbar Interbody Fusion Devices: Two Year Clinical and Radiographic Outcomes Yan Michael Li, MD 1 ; Richard Frisch, MD; Zheng Huang, MD, PhD 2 ; James Towner, MD 1 ; Yan Icy Li, PhD 1 ; Jessica Riggleman, BS 3 ; and Charles Ledonio 3 University of Rochester Medical Center, Rochester, NY 1 ; Guanghua Hospital, Shanghai, China 2 ; and Globus Medical, Inc., Audubon, PA 3 Introduction: The use of large interbody spacers in minimally invasive lateral lumbar interbody fusion (MIS LLIF) commonly offers favorable clinical and radiographic results. Static interbody spacers may cause iatrogenic endplate damage and implant subsidence due to forceful impaction and excessive trialing. Expandable interbody spacers with adjustable lordosis offer in situ expansion that may optimize endplate contact and maximize and maintain sagittal correction until fusion occurs. Aims/Objectives: This study compares the clinical and radiographic outcomes between patients treated with static and expandable interbody spacers with adjustable lordosis using MIS LLIF. Methods: This is a multi-surgeon, retrospective, IRB-exempt chart review of consecutive patients who underwent MIS LLIF at 1-2 contiguous level(s) using either a polyetheretherketone (PEEK) static (27 patients) or a titanium expandable spacer with adjustable lordosis (24 patients). The mean differences of radiographic and clinical functional outcomes were collected and compared from preoperative up to 24-month postoperative follow-up. Statistical results were significant if p<0.05. Results: Mean improvement of Visual Analog Scale (VAS) back pain scores from preoperative to 6, 12, and 24 months was significantly higher in the expandable group compared to the static group (p<0.05). Mean improvement of Oswestry Disability Index (ODI) scores from preoperative to 3, 6, 12, and 24 months was significantly higher in the expandable group compared to the static group (p<0.05). The expandable group had a significantly greater mean improvement in segmental lordosis from preoperative to 6 weeks, 3, 6, and 12 months (p<0.05). For disc height, the mean improvement from preoperative to Next >