< PreviousAbstracts AnnualForum’19 20ANNUAL FORUM ’19 | LAS VEGAS, NEVADA | OCT. 31–NOV. 2, 2019 Conclusions: In this investigation, we compared the clinical recovery of patients with varying comorbidities undergoing MIS TLIF using the PROMIS PF questionnaire. Interestingly, regardless of the number of comorbidities, as measured by CCI, patients reported similar preoperative PROMIS PF scores and had similar improvements in function throughout the 1-year follow-up. This study established that PROMIS PF is an effective tool to evaluate recovery of patients with differing comorbidities following MIS TLIF. Disclosures: J. Yoo: None. N. Jenkins: None. J. Parrish: None. N. Hrynewycz: None. T. Brundage: None. K. Singh: A; Cervical Spine Research Society. B; Zimmer Biomet, Stryker K2M, DePuy Synthes. D; Minimally Invasive Spine Study Group, Avaz Surgical, Vital 5. F; Zimmer Biomet, Stryker K2M, RTI Surgical, LippincottWilliams & Wilkins, Jaypee Publishing, Thieme, Slack Publishing. Paper #19: Does Minimally Invasive Anterior- Posterior Lateral Position Surgery Deteriorate Clinical Outcome and Spinal Alignment for Lumbar Spondylolisthesis Versus MIS TLIF? Yoshihisa Kotani, MD, PhD 1 ; Tachi Hiroyuki, MD 2 ; Yumejiro Nakamura, MD 2 ; and Takanori Saito, MD 3 Kansai Medical University Medical Center, Osaka, Japan 1 ; Hokkaido University Graduate School of Medicine, Sapporo, Japan 2 ; and Kansai Medical University Hospital, Osaka, Japan 3 Introduction: The lateral interbody fusion has been recently popularized for surgical treatment of lumbar spondylolisthesis. To shorten the operation time, we have been performed 1-stage lateral position surgery using oblique lumbar interbody fusion (OLIF) and percutaneous cortical bone trajectory (CBT) screw fixation over 150 cases. Aims/Objectives: In this study, we compared the clinical outcome and spinal alignment between AP lateral position surgery and MIS TLIF in the single-level fusion for lumbar spondylolisthesis. Methods: A total of 142 patients underwent either OLIF (92 cases) or MIS TLIF (50 cases) for L3 or L4 degenerative spondylolisthesis. The average age was 71 year (range, 23- 88). The AP lateral position surgery was performed with OLIF and percutaneous CBT fixation using O-arm. MIS TLIF was performed by midline 35 mm incision with interbody cage and modified CBT screws. The operation time, estimated blood loss, serum CRP and CPK, JOABPEQ effective rate (%), VAS, fusion rate, radiologic segmental alignment, and complications were evaluated. Results: Average follow-up period was 31- and 57-months (range, 13-74) in OLIF and MIS TLIF, respectively. The average operation time and estimated blood loss were 108 minutes and 51 mL in OLIF, and 104 minutes and 69 mL in MIS TLIF. Serum CRP at POD 1 and 3 and CPK at POD 1 and 6 were significantly higher in OLIF than those in MIS TLIF. The JOABPEQ effective rate and LBP VAS at follow-up were statistically equivalent between the 2 groups except higher effectiveness of psychogenic domain in OLIF (p<0.01). Fusion rate was 97% and 96% in OLIF and MIS TLIF, respectively. The symptomatic adjacent degeneration was identified in 7% and 10% in OLIF and MIS TLIF groups, respectively, requiring 3 and 4 subsequent fusion surgeries, respectively. The disc height at 6-months postop and follow-up was higher in OLIF than MIS TLIF (11.9 vs 8.5 mm; p<0.01). Conclusions: The clinical and radiologic effectiveness of 1-stage lateral position surgery for lumbar spondylolisthesis has been recently questioned. The lateral position surgery successfully shortened the operation time and blood loss to that of MIS TLIF level; however, serum CRP and CPK level indicated more invasive than MIS TLIF. The LBP and QOL parameters at follow- up demonstrated the equivalent results with better radiologic disc height increase in OLIF group. In conclusion, AP minimally invasive lateral position surgery for lumbar degenerative spondylolisthesis did not deteriorate the clinical outcome and radiologic spinal alignment compared to MIS TLIF over 2-year follow-up period in average. Disclosures: Y. Kotani: None. T. Hiroyuki: None. Y. Nakamura: None. T. Saito: None. Paper #20: Single Position Anterior-Posterior Lumbar Fusion Improves Perioperative Outcomes and Reduces Complications Compared to Traditional Anterior-Posterior Lumbar Fusion Aaron Buckland, MD, FRACS 1 ; Jordan Manning, BA 1 ; Carlos Leon, BE 1 ; Dennis Vasquez-Montes, MS 1 ; Leon Eisen, MD 1 ; Mark Medley, MD 2 ; Kimberly Ashayeri, MD 1 ; Nicholas O'Malley, BS 1 ; Themistocles Protopsaltis, MD 1 ; and J. Alex Thomas, MD 2 NYU Langone Health, New York, NY 1 and Atlantic Neurosurgical & Spine Specialists, Wilmington, NC 2 Introduction: Anterior lumbar onterbody fusion (ALIF) and lateral lumbar interbody fusion (LLIF) with percutaneous posterior fixation are two techniques used to address degenerative lumbar pathologies. Traditionally, these anterior- posterior (AP) surgeries involve repositioning the patient from CONCURRENT SESSION 2B: DEGENERATIVE & POSTERIOR FREE PAPERS Abstracts AnnualForum’19 21ANNUAL FORUM ’19 | LAS VEGAS, NEVADA | OCT. 31–NOV. 2, 2019 the supine or lateral decubitus position to prone for posterior fixation. To reduce operative time (OpTime) and subsequent complications of prolonged anesthesia, single position anterior- posterior lumbar fusion surgery (SPLS) is a novel minimally invasive alternative performed entirely from the lateral decubitus position. Aims/Objectives: Assess the perioperative safety and efficacy of SPLS. Methods: A retrospective clinical and radiological review of patients undergoing SPLS compared with traditional AP lumbar fusion, including patient repositioning (Flip). Patients undergoing primary ALIF and/or LLIF surgery with bilateral percutaneous pedicle screw fixation between L2-S1 were included over a 4-year period at 2 institutions. Patients were classified as either Flip or SPLS. Outcome measures included levels fused, percentage of cases including L5-S1 fusion, fluoroscopy radiation dosage, OpTime, estimated blood loss (EBL), length of stay (LOS), and intra- and post-operative complications. Radiographic analysis included lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT), and segmental lumbar lordosis. Demographic, procedural, perioperative, and radiographic measures were compared using independent samples t-tests and chi-squared analyses as appropriate with significance set at p<0.05. Results: A total of 390 patients undergoing AP surgery were included, of which 237 underwent SPLS and 153 were in the Flip group. Age, gender, BMI, CCI, were similar between groups. Levels fused (1.47 SPLS vs 1.52±0.8 Flip, p=0.468) and percent cases including L5-S1 (31% SPLS, 35% Flip, p=0.405) were similar between cohorts. SPLS significantly reduced OpTime compared to Flip (99 min vs 306 min, p<0.001) in addition to EBL (94 mL vs 313 mL, p<0.001), LOS (1.69 days vs 4.12 days, p<0.001), and fluoroscopy radiation dosage (30 mGy vs 88 mGy, p<0.001). Additionally, intraoperative and postoperative complications were similar between SPLS and Flip cohorts with the exception of postoperative ileus, which was significantly lower in the SPLS group (0% vs 5%, p<0.001). There was no difference in wound, vascular injury, neurological complications, or VTE. No difference was found in 90-day return to OR. Finally, preoperative and first erect postoperative radiographic analysis demonstrated no statistical difference between SPS and Flip groups. Conclusions: Single-position SPLS is a novel approach to performing circumferential fusion. The technique improves operative efficiency in addition to reducing blood loss, length of stay, and ileus in this large cohort study, while maintaining safety. Disclosures: A. Buckland: B; NuVasive, EOS Imaging, Stryker K2M. J. Manning: None. C. Leon: None. D. Vasquez-Montes: None. L. Eisen: B; NuVasive. M. Medley: B; NuVasive, Globus Medical, Medtronic. K. Ashayeri: None. N. O'Malley: None. T. Protopsaltis: A; Cervical Spine Research Society. B; Globus Medical, Innovasis, Stryker K2M, Medicrea, NuVasive. D; Torus Medical. J. Thomas: B; NuVasive. Paper #21: Clinical Results of Percutaneous Endoscopic Transforaminal Lumbar Interbody Fusion: A New Modified Technique for Treating Degenerative Lumbar Spondylolisthesis Ken Nagahama 1 ; Eihiro Murota 1 ; and Katsuhisa Yamada 2 Wajokai Sapporo, Hokkaido, Japan 1 and Hokkaido University Hospital, Hokkaido, Japan 2 Introduction: Minimally invasive TLIF (MI-TLIF) is less invasive, involves less blood loss, and has a shorter recovery time compared with open TLIF. However, in addition to MIS TLIF, partial laminectomy, facetectomy, and ligament flavum dissection, an open incision of the musculature are required to reach the vertebrae. If the vertebrae are approached posterolaterally via Kambin’s Triangle, invasive procedures can be avoided. If this path can be sufficiently expanded to allow for the passage of an interbody cage of the size used in open TLIF, it may be possible to apply LIF while completely preserving the joint facet. Aims/Objectives: We developed a surgical device comprising an oval dilator, oval sleeve, and a J-shaped nerve retractor. This device is capable of securing a percutaneous path large enough to safely insert an interbody cage. We also conceived a new technique, percutaneous endoscopic TLIF (PETLIF). We describe here the early clinical results of this new technique. Methods: Twenty-five patients requiring interbody fusion for degenerative spondylolisthesis of the L4 vertebra were enrolled in this study. The procedure involved percutaneous posterior pedicle screw placement to correct spondylolisthesis. After the exterior of the L5 vertebra superior articular protrusion was shaved with a percutaneous endoscopic drill in order to expand the safe zone, the oval sleeve was inserted through Kambin’s Triangle and was rotated to expand the disk height and create a path towards the vertebral disk. The interbody cage was inserted against the J-shaped nerve retractor, with the exiting nerve root retracted. Indirect decompression of spinal canal stenosis was expected because the vertebral body spondylolisthesis had been corrected, and the interbody distance was expanded. Thus, no direct decompression was performed posterolaterally. CONCURRENT SESSION 2B: DEGENERATIVE & POSTERIOR FREE PAPERS Abstracts AnnualForum’19 22ANNUAL FORUM ’19 | LAS VEGAS, NEVADA | OCT. 31–NOV. 2, 2019 Results: The mean follow-up period, surgery time, and blood loss were 22.7 months, 125.4 minutes, and 64.8 mL, respectively. The Japanese Orthopedic Association score improved from 13.3 to 28.0. The Roland-Morris Disability Questionnaire score improved from 10.3 to 3.3. All items were evaluated both preoperatively and 1-year postoperatively. Bone fusion was observed 1-year postoperatively in 22 out of 25 patients. Conclusions: These results demonstrate the feasibility and efficacy of PETLIF for treating degenerative lumbar spondylolisthesis. This minimally invasive procedure is useful and has wide applicability. To obtain safe and favorable results, necessary surgical techniques must be mastered, and surgical equipment, including that for neural monitoring, is required. Disclosures: K. Nagahama: None. E. Murota: None. K. Yamada: None. Paper #22: A New Groove-Entry Technique for Inserting Thoracic Percutaneous Pedicle Screws Ken Ishii, MD 1 ; Norihiro Isogai, MD 1 ; Yoshiyuki Takahashi, MD 2 ; Kodai Yoshida, MD 2 ; Yutaka Sasao, MD 1 ; Makoto Nishiyama, MD 1 ; and Haruki Funao, MD 1 International University of Health and Welfare, Tokyo, Japan 1 and International University of Health and Welfare Mita Hospital, Tokyo, Japan 2 Introduction: Minimally invasive spine stabilization (MISt) using posterior instrumentation has many advantages over conventional open procedures. Percutaneous pedicle screw (PPS) insertion techniques are widely used in MISt procedures. PPS placement in the thoracic spine is technically challenging, because the entry point is tricky, located at the sloping bony cortex of the transverse process, and the PPS must be inserted through the narrow thoracic pedicle. Aims/Objectives: To propose a novel groove-entry technique for thoracic PPS insertion. Methods: The entry point is craniolateral to the pedicle and to the cranial side of the base of the transverse process, where a groove configuration is formed by 3 bony elements: The cranial side of the base of the transverse process , the rib neck, and the dorsolateral side of the pedicle. This groove can be identified easily and securely with a Jamshidi needle (Becton, Dickinson and Company). Because the entry point is on the cranial side of the pedicle, the thoracic PPS is inserted in the craniocaudal direction. To evaluate the accuracy and safety of thoracic PPS placement using the groove-entry technique, we retrospectively reviewed data for 19 patients who underwent MISt procedures. We assessed PPS placement accuracy using postoperative CT images and outcome-based classifications modified from a previously reported system. PPS placement was graded as Type I if the screw was placed well, within either the pedicle medullary canal or the pedicle-rib unit; as Type II if placement was acceptable, with medial perforation or anterior cortex perforation of < 2 mm; and as Type III if placement was unacceptable, with a screw-thread breach with > 2 mm of medial or anterior cortex perforation. Results: We evaluated 123 thoracic PPSs placed in 19 patients who underwent MISt to treat metastatic tumor, degenerative adult scoliosis, vertebral fracture, or infection. Postoperative CT images showed Type I placement for 110 screws, Type II for 12 screws, and Type III for 1 screw. A review of fluoroscopic images showed that no Jamshidi needles, guide wires, or taps penetrated the lateral aspect of the pedicle or the anterior aspect of the vertebra. There were no intraoperative or postoperative complications potentially related to PPS placement. Conclusions: The present study demonstrates that groove- entry thoracic PPS placement under fluoroscopic guidance is both safe and reliable, with a low misplacement rate and an extremely low rate of complications compared with the high rates previously reported for thoracic PPS insertion techniques. Disclosures: K. Ishii: None. N. Isogai: None. Y. Takahashi: None. K. Yoshida: None. Y. Sasao: None. M. Nishiyama: None. H. Funao: None. Paper #23: The Use of Bone Morphogenetic Protein in the Intervertebral Disk Space in Minimally Invasive Transforaminal Lumbar Interbody Fusion: 10-year Experience in 688 Patients Jacob Archer 1 and Jean-Pierre Mobasser 2 Indiana University School of Medicine, Indianapolis, IN 1 and Goodman Campbell Brain and Spine, Indianapolis, IN 2 Introduction: Minimally invasive transforaminal lumbar interbody fusion (MIS TLIF) has been utilized as a technique for decreasing patients' immediate postoperative pain, decreasing blood loss, and shortened hospital stays. Effectiveness and complications of human bone morphogenetic protein-2 (hBMP2) use in the disk space is limited because of its off-label status. Aims/Objectives: The objective of this study was to characterize 1 surgeon's experience over a 10-year period using rhBMP2 in CONCURRENT SESSION 2B: DEGENERATIVE & POSTERIOR FREE PAPERS Abstracts AnnualForum’19 23ANNUAL FORUM ’19 | LAS VEGAS, NEVADA | OCT. 31–NOV. 2, 2019 the disk space for MIS TLIF . Methods: Retrospective analysis of consecutive MIS TLIFs performed by senior author between 2004 and 2014; rhBMP2 was used in the disk space in all cases. Patients were stratified based on the dose of rhBMP-2 utilized. Patients had 9- to 12-month computerized tomography scan to evaluate for bony fusion and continued follow-up for 18 months. Results: A total of 688 patients underwent MIS-TLIF. A medium kit of rhBMP-2 was utilized in 97 patients, and small kit was used in 591 patients. Fusion rate was 97.9%, with no difference between the 2 groups—96/97 patients fusing in the medium kit group and 577/591 patients fusing in the small kit group. Five patients were taken back to the operating room for symptomatic pseudoarthrosis, 4 patients were reoperated on for bony hyperostosis, and 10 patients had radiographic pseudoarthroses that did not require reoperation. A statistically significant difference in the rate of foraminal hyperostosis was found when using a medium sized kit of rhBMP2 compared with a small kit (4/97 vs. 0/591, p=0.0004). Conclusions: Utilization of rhBMP2 in an MIS TLIF leads to high fusion rate (97.9%), with an acceptable complication profile. The development of foraminal hyperostosis is a rare complication that only affected 0.6% of patients, and seems to be a dose-related complication, as this complication was eliminated when a lower dose of rhBMP2 was utilized. Disclosures: J. Archer: None. J. Mobasser: B; Medtronic. F; Medtronic, Innomed. Paper #24: Multi-Level Stenosis and Deformity of Spine: When Is a Only Microsurgical Approach Indicated? Dmitry Dzukaev; Anton Borzenkov; Vladimir Guly; and Mikhail Safronov City Clinical Hospital 67, Moscow, Russia Introduction: Among a large range of patients with multilevel stenosis and deformity of spine not everyone needs complicated operation with multilevel instrumentation. Aims/Objectives: The aim of the study was to work out an algorithm of preoperative examination of patients with spine deformity and multilevel canal stenosis, which gave an ability to pick up the patients with indications for microsurgical approach. Methods: During the period between 2014 and 2017, our research collected information on 152 patients with multilevel lumbar stenosis and spine deformity. Of the 152 patients, 58 underwent a minimally invasive approach without instrumentation and were selected according to the following criteria: satisfactory quality of life, but acute deterioration 2-3 months to 1-week before entrance to the our spinal center, and 1 or 2 nerve roots compression according to the clinical examination. These measurements were approved clinically and radiologically. Patients’ selection for microsurgery was performed with the preoperative examination and MRI assessment algorithm. The research was provided by MR tomography 1,5 T. The protocol included diagonal slices (slice’s thickness 1-3 mm), which had been conducted through each stenosis level. After MRI data had been received, the detail assessment of nerve root condition (its route, diameter, edema signs) and the degree of compressive factors influence was performed. Also multi-spiral CT and functional radiographs data confirmed stable character of deformity. In all the patients, nerve root microsurgery decompression by minimally invasive approach was performed. In each case instrumentation wasn’t used. Results: The usage of the preoperative examination and MRI assessment algorithm allowed us to select 58 patients with multilevel stenosis that were appropriate for microsurgery out of 152 patients with expressed degenerative spine lesion. All the patients in the microsurgery group were pain free immediately after the surgery, and the effect persisted during the observation period, which was between 1 and 3,5 years. Conclusions: Correct interpretation of present clinical data, disease development, as well as the usage of the preoperative examination and MRI assessment algorithm allows to emphasize irritated nerve root, causing reduced quality of life for patients with multilevel stenosis. The establishment of the precise lesion localization gives an opportunity for microsurgery, therefore, reducing the need for aggressive operation, decreasing X-ray dose, reducing instrumentation expense, and lessening postoperative rehabilitation period. Disclosures: D. Dzukaev: None. A. Borzenkov: None. V. Guly: None. M. Safronov: None. CONCURRENT SESSION 2B: DEGENERATIVE & POSTERIOR FREE PAPERS Abstracts AnnualForum’19 24ANNUAL FORUM ’19 | LAS VEGAS, NEVADA | OCT. 31–NOV. 2, 2019 Paper #25: Preliminary 24-month Outcomes of a Prospective Investigation of a Novel Mesh Interbody Spacer in Single-level Fusions John Chi, MD, MPH 1 ; Yi Lu, MD, PhD 1 ; Kevin Huang, MD 1 ; Stephane Lavoie, MD 2 ; Martin Krag, MD 3 ; Pierce Nunley, MD 4 ; and Mohamad Bydon, MD 5 Brigham and Women's Hospital, Boston, MA 1 ; Florida Orthopaedic Associates, Orange City, FL 2 ; University of Vermont Medical Center, South Burlington, VT 3 ; Spine Institute of Louisiana, Shreveport, LA 4 ; and Mayo Clinic, Rochester, MN 5 Introduction: A prospective multicenter investigational device exempt trial is underway with the purpose of establishing the short- and long-term safety and effectiveness of a novel conformable mesh interbody fusion device in subjects undergoing single-level fusion for degenerative disc disease unresponsive to conservative care. When placed in the disc space through a small portal and filled with bone graft in situ, this device reduces risk of trauma to surrounding structures while creating a large footprint that intimately contours to the patient’s own anatomy. Aims/Objectives: This early analysis impartially evaluates results of long-term patient outcomes for follow-up compliance, consistency of findings, and trending in a regulated clinical investigation. Methods: One-hundred two subjects were enrolled in the performance-goal trial across 10 geographically distributed sites. High compliance is observed with only a 2.9% attrition rate; 99 subjects remain available for follow-up at 24-months. Presently, 82 of the 99 subjects are evaluated at 2-years. Mean age at time of consent is 57 years, gender distribution is balanced, and mean BMI is 30.6. Physical evaluations/ imaging are performed serially through 24-months. Validated assessment tools include 100 mmVAS for pain, Oswestry Disability Index (ODI) for function, and computerized tomography scan for fusion. Independent committees for event adjudication and fusion assessment mitigate potential bias and add objectivity to oversight. Results: Analysis reveals significant reductions in low back pain (LBP)/leg pain and substantial improvements in back function occur early and are maintained through 2-years. Mean LBP change from baseline at 6-weeks (-45.0) continued to improve through 24-months (-51.7). Similar trends are observed for leg pain reductions over time. Mean ODI change from baseline at 6-weeks of -17.1 was almost doubled by 24-months (-32.5). At 2-years, 90% of subjects rated their procedure as excellent/ good. Fusion rates at 12-months are high (97%, 95/98). No device-related serious adverse events have occurred. Conclusions: Exceptional compliance coupled with highly positive outcomes for pain, function, fusion, and device safety are demonstrated in this population. Substantial clinical improvements occur by 6-weeks post-op and are maintained or improved over time. It is expected this trending will be observed for the remaining subjects through 24-months. The successful outcomes observed in this trial support use of this novel device in an interbody fusion indication. Final analysis is both anticipated and forthcoming. Disclosures: J. Chi: B; Stryker K2M. Y. Lu: A; Stepping Strong Foundation, Spineology. B; Depuy Synthes. C; Paradigm Spine. D; AxioMed. K. Huang: None. S. Lavoie: A; Spineology. B; Spineology, Consultant. F; Spineology. M. Krag: None. P. Nunley: B; Stryker K2M, Zimmer Biomet, Spineology, Vertiflex, Camber Spine, Integrity Spine, Centinel Spine, Amedica, Paradigm Spine. M. Bydon: None. Paper #26: Single-Level Controlled Comparison of OLIF51 and PPS in Lateral Position Versus MIS TLIF for Lumbosacral Degenerative Disorders: Clinical and Radiologic Study Yoshihisa Kotani, MD, PhD 1 ; Hiroyuki Tachi, MD 2 ; Yumejiro Nakamura, MD 2 ; and Takanori Saito, MD 3 Kansai Medical University Medical Center, Moriguchi, Osaka, Japan 1 ; Hokkaido University Graduate School of Medicine, Sapporo, Japan 2 ; and Kansai Medical University Hospital, Hirakata, Osaka, Japan 3 Introduction: Several advantages of lumbosacral ALIF have been reported in terms of superior stability, broad bone graft area, and indirect neural decompression. We have performed OLIF51 through retroperitoneal approach and simultaneous PPS in lateral position for lumbosacral disorders. Aims/Objectives: This study aimed to compare the clinical and radiologic results between OLIF51 and MIS TLIF under single- level controlled study design. Methods: A total of 71 patients underwent either OLIF51 (33 cases) or MIS TLIF (38 cases). The average age was 64 years (range, 27-88). The applied disorders were L5 isthmic and degenerative spondylolisthesis, foraminal stenosis, pseudarthrosis, adjacent segment degeneration, etc. Using 35 mm oblique incision, OLIF51 was performed through retroperitoneal approach under the visualization of left common iliac vein with enhanced O-arm 3D navigation. The simultaneous posterior percutaneous fixation was performed with modified CBT in same lateral position. MIS TLIF was performed with midline 40 mm incision and modified CBT screws. The operation CONCURRENT SESSION 2B: DEGENERATIVE & POSTERIOR FREE PAPERS Abstracts AnnualForum’19 25ANNUAL FORUM ’19 | LAS VEGAS, NEVADA | OCT. 31–NOV. 2, 2019 time, estimated blood loss, JOABPEQ effectiveness (%), VAS, fusion rate, radiologic segmental alignment, and complications were evaluated. Results: Average follow-up period was 25- and 31-months (range, 12-45) in OLIF51 and MIS TLIF, respectively. The average operation time was 165 minutes and 163 minutes, respectively. The estimated blood loss was 62 mL and 68 mL, respectively. The JOABPEQ effective rate in OLIF51 demonstrated statistically higher value in LB function (44% vs 17%, p<0.05). The LBP VAS improved significantly in both groups (p<0.05). The fusion rate was 97% and 92% in OLIF51 and MIS TLIF groups, respectively. The segmental lordosis was significantly higher in OLIF51 (17 vs 11 deg, p<0.01), however, disc height was equivalent between groups. There were no vascular or neural complications in either groups. Conclusions: Although MIS TLIF has been reported as an excellent surgical procedure, there have been limitations in terms of fusion rate in severe osteoporosis and residual low back pain. In this study, the operation time and estimated blood loss were almost equivalent in both groups; however, low back function parameter demonstrated the significant superiority in OLIF51 over MIS TLIF. The fusion rate and segmental lordosis creation were also better in OLIF51. Even in the short-segment lumbosacral fusion, OLIF51 serves as a safe and viable surgical procedure with use of lateral position surgery, minimizing the pseudarthrosis and residual low back pain. Disclosures: Y. Kotani: None. H. Tachi: None. Y. Nakamura: None. T. Saito: None. Paper #27: Patients Receiving Nonsurgical Management for Sacroiliitis Diagnosed with Intra-Articular Injection Report Positive Outcomes at Long-term Follow-up Timothy Westbrooks, BS; Weston Bell, BS; Richard Smith, PhD; and Raymond Gardocki, MD University of Tennessee Health Science Center, Memphis, TN Introduction: Sacroiliitis is a common cause of chronic low back pain. Diagnosis is difficult due to the lack of specific symptoms or radiographic findings and is usually accomplished through various clinical maneuvers. Utilization of a diagnostic injection into the SI joint has been adopted as a practice in order to further solidify the diagnosis of sacroiliitis; however, to date it is undetermined whether or not these injections predict positive responses to future directed therapy. Our study, a retrospective review with telephone survey, provides evidence that relief with intra-articular injection more definitively confirms a diagnosis of sacroiliitis and predicts positive outcomes with non-surgical management. Aims/Objectives: To determine if relief with intra-articular injection can confirm a diagnosis of sacroiliitis and predict positive outcomes with non-surgical management. Methods: This is a retrospective review with telephone follow-up of 256 patients. Type of treatment, satisfaction with treatment, complications of treatment, current VAS, current pain level (better, worse, same), willingness to have treatment again if necessary, underlying inflammatory conditions, number of births, and surgical history of lumbar fusion or hip replacement were determined from the phone survey. Patients were grouped according to how they felt after initial diagnostic injection (Improved , Not Improved [NI], or No Injection [NO]). Grouping was based on a 5-point Likert scale. Results: When patients were grouped (I, NI, NO), significantly more patients in group I, 94/128 (73%; p= 0.001) described themselves as better at final follow-up compared to only 19/70 patients (27%) in group NI. Of the 58 patients in the NO group, 41 (71%) described themselves as better at final follow up. Mean VAS score at final follow-up was significantly higher in the NI group (6.0 ± 3.0) compared to the I group (3.9 ± 2.8) and the NO group (3.1 ± 3.1). Significantly more patients in the I group said they would go through their treatments again (75%) compared to the NI group (29%). There were no significant differences between the groups in terms of other demographic data, inflammatory conditions, or past surgical history. Only 3 patients in the study were treated with SI joint fusion, 2 in the I group and 1 in the NI group. Conclusions: Sacroiliitis patients who respond positively to intra-articular injection of the SI joint are likely to benefit from nonsurgical management. Sacroiliac joint fusion should be postponed until conservative management fails due to risks associated with surgery. Disclosures: T. Westbrooks: None. W. Bell: None. R. Smith: None. R. Gardocki: None. CONCURRENT SESSION 2B: DEGENERATIVE & POSTERIOR FREE PAPERS Abstracts AnnualForum’19 26ANNUAL FORUM ’19 | LAS VEGAS, NEVADA | OCT. 31–NOV. 2, 2019 Paper #28: Comparison of Clinical and Radiological Results Using Uniportal Versus Biportal Endoscopic Discectomy for Single- Level Lumbar Disc Herniation Dong Geun Lee, MD The Leon Wiltse Memorial Hospital, Suwon, Republic of Korea Introduction: Recently indroduced biportal endoscopic discectomy is similar to open microdiscectomy. The technique combines the advantages of standard open surgery and endoscopic spinal surgery. The biportal technique is increasingly used to overcome technical difficulties and a restricted field of vision of conventional uniportal technique. Aims/Objectives: The aim of this study was to compare the clinical and radiological results and expiscate advantages and disadvantages of each procedures treated by uniportal (percutaneous endoscopic interlaminar discectomy) and biportal method. Methods: This study included 140 patients who underwent either uniportal endoscopic discectomy (n=78) or biportal endoscopic discectomy (n=62) for single-level lumbar disc herniation between June 2017 and June 2018. The clinical comparison was performed using Visual Analog Scale (VAS), Oswestry Disability Index (ODI), recurrence rate, and complications. Operation time and hospital day was also compared. Radiologically, the comparison of degree of disc degeneration at operation level and adjacent segmental degeneration was carried out at 1-year follow-up by CT. Additionally, radiological risk factor of recurrence was evaluated. Results: The average operation time was significantly shorter in the uniportal group (68.7±3.0 min) when compared to the biportal group (91.7±3.7min). There is no significant difference of ODI in preoperative, postoperative, and between uniportal group and biportal group. However, postoperative VAS of the first day was significantly less in the uniportal group than biportal group (p=0.006). Recurrence rate was 5.1% (4 patients) (in uniportal group and 1.6% (1 patient) in biportal group. Complications included transient leg dysthesia in 4 patients and dura tear in 1 patient in the uniportal group, and postoperative hematoma in 2 patients and iatrogenic isthmic fracture in 1 patient in biportal group. No major complication occurred. There is no significant difference of degree of disc degeneration at operation level and ASD. Conclusions: Both uniportal and biportal discectomy are effective, safe, and minimally invasive for lumbar disc herniation. The uniportal approach causes less postoperative pain, less operative time, but has limited indication. The biportal approach, which raise nearly full discectomy, has broad indication, less recurrence, and more decompression is a more reasonable procedure and is more advantageous for restricted case than biportal endoscopy in treatment of lumbar disc herniation Disclosures: D. Lee: None. Paper #29: Does Degenerative Spondylolisthesis Require Instrumented Fusion? Unilateral Laminotomy for Bilateral Decompression Versus Posterior Decompression with Fusion at 5-Year Follow-up Calvin Kuo, MD; Maqdooda Merchant, MA, MSc; Mayur Kardile, MD; Alem Yacob, MD, MSc; Kamran Majid, MD, MBA; and Ravi Bains, MD Kaiser Permanente, Oakland, CA Introduction: Controversy exists regarding whether fusion should be used to augment decompression surgery in patients with symptomatic lumbar spinal stenosis with low-grade degenerative spondylolisthesis. For years, the standard has been fusion with laminectomy in order to prevent postoperative instability. However, instability and reoperations may be reduced or prevented using structure sparing decompression techniques without the need for fusion. Aims/Objectives: To compare reoperation rates within a 5-year follow-up period of unilateral laminotomy for bilateral decompression (ULBD) versus posterior lumbar decompression with instrumented fusion (Fusion) for patients with degenerative spondylolisthesis with spinal stenosis in a multicenter database. Methods: We identified 164 patients with degenerative spondylolisthesis and lumbar stenosis who underwent ULBD from 2007 to 2011 in a large integrated healthcare system. These patients were propensity score matched on age, gender, race, smoking status and Charlson Comorbidity Index (CCI) with patients who underwent Fusion (n=437). The primary outcome was 5-year reoperation rate. Secondary outcome measures included postoperative complication rates, blood loss during surgery, and length of stay. CONCURRENT SESSION 2B: DEGENERATIVE & POSTERIOR FREE PAPERS Abstracts AnnualForum’19 27ANNUAL FORUM ’19 | LAS VEGAS, NEVADA | OCT. 31–NOV. 2, 2019 Results: The reoperation rate at 5-year follow-up was significantly lower at 10.4% for ULBD compared to 17.2% for Fusion (p=0.0454). Patients that underwent ULBD had significantly less mean estimated blood loss compared to Fusion (82 mL vs. 445 mL, p<0.0001) and significantly shorter mean length of stay (2.3 days vs 4.6 days, p<0.0001). ULBD reoperations were more frequent at the index surgical level; Fusion reoperations were more common at an adjacent level. The 2 types of operations had similar postoperative complication rates, and both groups tended to have fusion reoperations. Conclusions: For patients with stable degenerative spondylolisthesis and lumbar stenosis, ULBD is a viable, durable option compared to Fusion with a lower reoperation rate within a 5-year follow-up period, as well as decreased blood loss and length of stay. Further prospective studies are required to determine the optimal clinical scenario for ULBD in the setting of degenerative spondylolisthesis. Disclosures: C. Kuo: None. M. Merchant: None. M. Kardile: None. A. Yacob: None. K. Majid: None. R. Bains: None. Paper #30: Clinical Efficacy and Safety of Trans-Sacral Epiduroscopic Laser Decompression Compared to Percutaneous Epidural Neuroplasty Bong Ju Moon, Dr 1 ; Hyuk Hur, Dr 2 ; Gwang Jun Lee, Dr 1 ; Seul Gi Lee, Dr 1 ; and Jung-Kil Lee, Dr 1 Chonnam National University Hospital, Gwangju, Republic of Koreaf 1 and Naju General Hospital, Gwangju, Republic of Korea 2 Introduction: Percutaneous epidural neuroplasty (PEN) is an effective and safe procedure for herniated lumbar disc (HLD). Although PEN has an advantage of adhesiolysis, this procedure cannot decompress the protruded disc. Recently, trans-sacral epiduroscopic laser decompression (SELD) for HLD has been introduced as a promising alternative methodology. Aims/Objectives: This study evaluated the clinical efficacy and safety of SELD compared to PEN, as well as the change in protruded disc volume after SELD through pre- and postoperative magnetic resonance imaging (MRI), in patients with HLD. Methods: Thirty consecutive patients underwent SELD (SELD group), and 45 patients underwent PEN (PEN group). The Visual Analog Scale (VAS) for leg pain; Oswestry Disability Index (ODI); 12-Item Short-Form Health Survey (SF-12); preoperative and postoperative 4-, 12-, and 24-week Macnab criteria; and preoperative and 24-week postoperative lumbar spinal MRIs after SELD were obtained. Results: There was no significant difference in age, sex, duration of symptoms, and the distributions of disc level between the 2 groups (all p>0.05). Between the SELD and PEN groups, preoperative VAS, ODI, and SF-12 scores had no significant differences. However, the VAS, ODI, and SF-12 scores improved significantly after the procedures by postoperative week 24 in each group (all p<0.05). Furthermore, improvements of VAS, ODI, SF-12, and success rate of Macnab criteria in the SELD group were better than those in the PEN group (all p< 0.05). The protruded disc volume after SELD decreased significantly (p= 0.034). Conclusions: All clinical and functional outcomes of patients undergoing SELD and PEN for HLD improved following the procedures. Notably, SELD was superior to PEN regarding the degree of improvement in clinical and functional outcomes. Therefore, we suggest that SELD can be used as an effective alternative to PEN to provide improved clinical and functional outcomes in patients with HLD. Disclosures: B. Moon: None. H. Hur: None. G. Lee: None. S. Lee: None. J. Lee: None. CONCURRENT SESSION 2B: DEGENERATIVE & POSTERIOR FREE PAPERS Abstracts AnnualForum’19 28ANNUAL FORUM ’19 | LAS VEGAS, NEVADA | OCT. 31–NOV. 2, 2019 Paper #31: An Intraoperative Radiographic Assessment Method for Evaluating Indirect Decompression in Oblique Lumbar Interbody Fusion Min-Gi Lee; Guang-Xun Lin; Sagar Sharma; Akaworn Mahatthanatrakul; and Jin-Sung Kim Seoul St. Mary’s Hospital, The Catholic University of Korea, Seoul, Republic of Korea Introduction: Lateral lumbar interbody fusion has gained wide acceptance due to its indirect decompression with promising clinical results. Oblique lumbar interbody fusion (OLIF) is similar to lateral lumbar interbody technique in terms of retroperitoneal approach. Surgeons can preserve posterior column structures and correct coronal and sagittal imbalance along with indirect decompression by ligamentotaxis effect of the OLIF cage Aims/Objectives: OLIF has gained wide acceptance as a technique of indirect decompression of neural elements. However, using radiological method to assess the adequacy of indirect decompression intraoperatively has not been reported yet. Thus, the objective of this study is to introduce an intraoperative radiographic assessment method that could be used to evaluate the feasibility of OLIF with indirect decompression. Methods: We retrospectively reviewed patients who underwent OLIF between October 2013 and April 2017. Clinical and radiographic parameters were evaluated preoperatively at 12 months after surgery. Clinical outcomes included back and leg pain evaluated by visual analog scale (VAS) and Oswestry Disability Index (ODI). Intraoperative radiographic parameters of height ratio [(HR) = disc height / intervertebral body height)] and cage location were evaluated on intraoperative fluoroscopic images. Disc height (DH), foraminal height (FH), cross-sectional area of spinal canal (CSAC), and cross-sectional area of foramen (CSAF) were also measured. Results: A total of 47 patients (16 males and 31 females; mean age: 66.0 ± 9.3 years) involving 62 levels were enrolled in this study. These patients reported an improvement of 61.7% in VAS back, 68.1% in VAS leg, and 46% in ODI (all p<0.01). Radiographic parameters including HR, DH, FH, CSAC, and CSAF were also significantly increased by 32.6%, 48.2%, 21.4%, 44.0%, and 40.1% (left side CSAF) or 45.4% (right side CSAF), respectively (p<0.05). The median value for the improvement of HR was 30.4% (interquartile range: 19.6% to 50.3%). Slightly higher improvements of HR, DH, FH, CSAC, and CSAF (both sides) were noted when cage was located at middle rather than anterior (p>0.05). Conclusions: Significant improvements in radiographic and clinical parameters can be obtained after indirect decompression in OLIF. Intraoperative height ratio can be used as a reference indicator for OLIF with indirect decompression. Disclosures: M. Lee: None. G. Lin: None. S. Sharma: None. A. Mahatthanatrakul: None. J. Kim: None. Paper #32: Early Radiological & Clinical Outcomes of Minimally Invasive Oblique Lumbar Interbody Fusion in Degenerative Lumbar Spine Disorders in Indian Population. Sharvil Gajjar, MS Orthopedics and Amit Jhala, MS Orthopedic Chirayu Spine and Orthopedic Hospital, Ahmedabad, India Introduction: Oblique lumbar interbody fusion (OLIF) is a novel approach that utilizes a bare area in between the psoas muscles and the great vessels known as the oblique corridor. OLIF works on the principle of indirect decompression of the spinal canal by distraction. OLIF helps in better fusion by increasing the cross sectional area of arthrodesis and increasing the disc height. The objective of this study is to determine the radiological and clinical results of OLIF technique in degenerative lumbar spine disorders. Aims/Objectives: Retrospective assessment of early radiological and clinical outcomes of minimally Invasive OLIF (MIS OLIF) in degenerative lumbar spine disorders. Methods: OLIF was carried out in 48 segments in 36 patients having degenerative lumbar spine disorders from May 2016 to September 2017. Patients with infection, trauma, lumbar disc prolapse, and lysthesis > Grade 3 were excluded. Of these, 43 segments had posterior and 5 segments had anterior fixation. Auto graft was used in 21 patients (30 segments) and artificial bone graft in 15 patients (18 segments). Indirect decompression by distraction was achieved in all. Neuromonitoring was not used. Clinical assessment was done using modified Macnab criteria. Radiological assessment was done on X-rays (LS spine) and MRI. Percentage improvement in foraminal height, disc height, segmental lordosis, spinal canal area, and reduction in lysthesis were measured. Statistical assessment was done using paired ‘t’ test. Results: Single segment fusion was done in 25 patients, 2 segment fusion in 10, and 3 segment fusion in 1 patient. CONCURRENT SESSION 2C: YOUNG SURGEONS’ FREE PAPERSAbstracts AnnualForum’19 29ANNUAL FORUM ’19 | LAS VEGAS, NEVADA | OCT. 31–NOV. 2, 2019 Clinically, 26 patients (72.2%) had excellent outcomes, 9 (25%) had good, and 1 (2.77%) had fair outcomes. None required direct decompression. Per-op complication rate was 13.9% and postoperative complication rate was 30.6%; most complications were reversible. Radiologically, foraminal height improved by 26.4%, disc height by 102.3%, segmental lordosis 3.37o, and lysthesis reduction was 7%. The 39 segments studied on MRI had improvement in spinal canal area of 45.4%. Conclusions: OLIF is an effective means of indirect decompression with early excellent to good results clinically and statistically significant improvement in radiological parameters. Disclosures: S. Gajjar: None. A. Jhala: None. Paper #33: Delayed Neurologic Deficit in Post OLIF Surgery Patient: Easy to Miss Findings on Images Seon Ho Park, MD and Bong Ju Moon, MD Chonnam National University Hospital, Gwang Ju, Republic of Korea Introduction: Oblique lumbar interbody fusion (OLIF) surgery is a recently introduced minimally invasive lateral interbody fusion surgery for degenerative lumbar disease with faster recovery, reduced operative (OP) time, lower complication rates, and shorter hospital stay compared to posterior procedures. Aims/Objectives: The purpose of this study is to introduce a few findings that will predict the failure of indirect decompression in patients undergoing OLIF. Methods: We retrospectively reviewed 43 Korean patients who underwent OLIF. In most cases, the surgeries were successful, but some patients experienced postoperative neurologic deficit. Posterior decompression was effective in revision cases. Results: The shape of foramen, vertebral body, and bony spur were relative to need for direct decompression. But, these findings were easy to miss on preoperative MRI. Conclusions: The current report described a rare but possible case of neurologic deficit following OLIF surgery. The current report also highlights that proper planning for foraminal stenosis and sufficiently wide posterior decompression. Disclosures: S. Park: None. B. Moon: None. Paper #34: Utility of Intraoperative Motor-Evoked Potential During L4-5 Direct Transpsoas Lateral Interbody Fusion to Avoid Nerve Injury Nima Alan; Gregory Adams, BS; Nitin Agarwal, MD; Alp Ozpinar, MD; Jeffery Balzer, PhD; Vincent Miele, MD; and Adam S Kanter, MD University of Pittsburgh Medical Center, Pittsburgh, PA Introduction: Nerve injury is reported as high as 23% in direct transpsoas lateral lumbar interbody fusion (LLIF), particularly at L4-5. Aims/Objectives: We aimed to evaluate the utility of transcranial motor evoked potential (MEP) to detect and avoid nerve injury during LLIF at L4-5 level. Methods: This is a prospective, observational, cohort study of patients undergoing L4-5 LLIF conducted by 2 spine surgeons at an academic hospital. The study began in January 2018 and is currently ongoing. Spontaneous and triggered electromyography (EMG) and somatosensory evoked potentials (SSEP) were routinely recorded. In addition MEPs from quadriceps and anterior tibialis muscle groups were also recorded bilaterally. Transcranial MEP were recorded every 5 minutes from the time of incision. A decrease in amplitude of 50% or more from baseline was considered a positive result, and the surgeon was alerted. Patient’s neurological exam and health-related quality of life (HRQOL) measures were collected preoperatively, immediately postoperatively, and at the time of follow-up at 6 weeks, 3 months, 6 months and 1 year. Results: Thirty-two patients were considered, 2 patients were excluded due to history of seizure and technical difficulties of obtaining reliable signals. Of the 30 patients included, 15 underwent LLIF only. Of these, L4-5 level was the only treated level in 11 patients. Outcome data demonstrated gradual improvement of all measured HRQOL at 1 year including ODI (40 to 34), visual analogue score (VAS) back pain (7.6 to 4.0) and leg pain (4.5 to 2.0). Transient quadriceps weakness occurred in 73% of patients but resolved by 6 weeks. Fifteen patients (50%) had a significant decrease in MEP amplitude without changes in spontaneous or triggered EMG and SSEP. Six patients had sustained decrease at the time of closure and 2 patients had persistent weakness in dorsiflexion at time of last follow-up at 6 weeks (3/5 strength) and 1-year (1/5 strength). In 1 patient, the surgery was aborted at the time of introduction of retractor due to 69% reduction in MEP and inability to mitigate the changes. None of the patients with a negative MEP developed persistent weakness postoperatively resulting in sensitivity of 100%. CONCURRENT SESSION 2C: YOUNG SURGEONS’ FREE PAPERSNext >