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The unique anatomy at L5-S1 presents different challenges and considerations to be made when compared to other areas in the lumbar spine. In this way, the oblique lumbar interbody fusion (OLIF) is more closely related to a supine anterior lumbar interbody fusion (ALIF) except that the former is performed in a lateral position down a smaller minimally invasive retroperitoneal corridor. This lateral positioning at L5-S1, however, provides an opportunity for single-position surgery simultaneously with posterior fixation, which is not afforded by other approaches.  We present here a case of a 57-yr-old male with a prior right-sided L5-S1 microdiscectomy who presents with worsening lumbar radiculopathy and foot drop. He subsequently underwent a minimally invasive L5-S1 OLIF with posterior instrumentation placed bilaterally while remaining in a single lateral position (Mazor X Stealth Edition, Medtronic, Dublin, Ireland). Both the anterior OLIF surgeon and posterior instrumentation surgeon were able to work simultaneously. There is currently a need for further high-quality operative videos showing the L5-S1 OLIF technique, and to our knowledge, this is the first video demonstrating a 2-surgeon near-simultaneous workflow approach using a spinal robotics platform at this level.  There is no identifying information in this video. A patient consent was obtained for the surgical procedure and for publishing of the material included in the video., (© Congress of Neurological Surgeons 2021.)

This surgical video demonstrates the technique of an oblique lumbar interbody fusion (OLIF) in the lumbar spine from L2 to L5 as well as an oblique approach to the L5-S1 level. It demonstrates the surgical approach, technical nuances of OLIF, and pearls of the surgery. The video discusses the importance of the release of the disc space to allow for height restoration and deformity correction, endplate preparation to enhance arthrodesis, and appropriate implant sizing. The concept of the approach is the minimally invasive blunt dissection through the abdominal wall musculature and mobilization of the retroperitoneal fat. Unlike the transpsoas approach, the surgery is performed anterior to the psoas, avoiding the lumbar plexus.1 For L5-S1, the approach is still performed in the lateral position but with an oblique approach. A vascular surgeon performs the L5-S1 approach, and the disc space is accessed through the iliac bifurcation.2 The discectomy and interbody fusion are performed similarly to a standard anterior lumbar interbody fusion (ALIF), but in a lateral position and at an oblique angle. The patient consented to this procedure and for filming a video of this case., (© Congress of Neurological Surgeons 2021.)

Backgroud: The purpose of this study was to compare clinical outcomes and complications of primary and revision surgery in patients with adult spinal deformity (ASD) accompanied by sagittal imbalance. Revision surgery has been associated with poor clinical outcomes and increased risk of complications. Previous studies comparing primary versus revision surgery included data for a wide variety of diseases and ages, but few investigated patients with ASD with sagittal imbalance undergoing anterior and posterior combined surgery., Methods: Retrospective cohort analysis of prospectively collected data. We identified 60 consecutive patients with ASD combined with sagittal imbalance who underwent primary or revision surgery; of these, 6 patients were excluded for lack of a minimal 2-year follow-up. Patients' surgical and radiological data, clinical outcomes, and complications were reviewed., Results: There were 30 patients in the primary group and 24 patients in the revision group. Patient characteristics, including the prevalence of sarcopenia, were similar between the two groups. Pedicle subtraction osteotomy was performed more frequently in the revision group although there was no statistically significant difference between groups. The primary group had more proximal junctional problems, whereas the revision group had more rod breakage ( p < 0.05). There were significant improvements in clinical outcomes in both groups when the preoperative and 2-year postoperative values were compared. The Oswestry disability index and visual analog scale score were similar in both groups 2 years postoperatively., Conclusions: Considering the greater pain and disability at the time of the revision procedure, revision patients benefited more from surgery at the 2-year follow-up than the primary surgery patients. Complication rates were similar between the groups except for proximal junctional problems and rod breakage. Therefore, revision surgery should not be avoided in the treatment of ASD patients with sagittal imbalance., Competing Interests: CONFLICT OF INTEREST: No potential conflict of interest relevant to this article was reported., (Copyright © 2021 by The Korean Orthopaedic Association.)

The use of robotic guidance for spinal instrumentation is promising for its ability to offer the advantages of precision, accuracy, and reproducibility. This has become even more important in the era of lateral interbody surgery because spinal robotics opens up the possibility of a straightforward workflow for single-position surgery in the lateral position. We present here a case of a 72-yr-old woman who presented with an L4-5 spondylolisthesis with axial back pain and radiculopathy. She subsequently underwent an L4-5 oblique lumbar interbody fusion with L4-5 bilateral posterior instrumentation in a single lateral position (Mazor X Stealth Edition, Medtronic Sofamor Danek, Medtronic Inc, Dublin, Ireland). Due to the oblique lateral approach and posterior robotic assistance, both surgeons were able to work simultaneously for increased efficiency. To our knowledge, this is the first video demonstrating a two-surgeon simultaneous robotic single-position surgery with oblique lumbar interbody fusion using a spinal robotic platform. There is no identifying information in this video. Patient consent was obtained for the surgical procedure and for publishing of the material included in the video., (© Congress of Neurological Surgeons 2021.)

Lumbar spinal fusion is one of the most common operations in spinal surgery. For its implementation, anterolateral (pre-psoas) approach (oblique lumbar interbody fusion, OLIF) is now increasingly used due to its high efficacy and safety. However, there is still little information on the clinical and radiological results of using this technique. The aim of the study was to analyze the safety and efficacy of OLIF in the treatment of lumbar spine disorders as presented in the literature., Materials and Methods: The systematic electronic search was performed using the Ovid Medline, PubMed, and eLIBRARY.RU electronic databases. The following search key words were used: Oblique Lumbar Interbody Fusion, OLIF, Anterior to Psoas Lumbar Interbody Fusion, and ATP., Results: For the final analysis, 17 sources were selected; with a total of 2900 patients. Total complication rate was 13.9% (403 cases). The incidence of severe persistent complications was less than 1%. Based on the data obtained, we compared the clinical and radiological results of OLIF with other lumbar fusion methods., Conclusion: OLIF is an effective, versatile, and minimally traumatic option for lumbar fusion with relatively few complications, which makes it superior to other retroperitoneal approaches. However, the OLIF technique is not completely free of complications associated with the ventral approach, and it cannot provide adequate decompression of the spinal canal in all cases. In addition, anterior approach surgery is still of limited use in cases of spinal deformities; adequate correction of deformity is achievable mainly in combination with posterior surgery., Competing Interests: Conflicts of interest. The authors declare no conflicts of interest.

Background: The number of oblique lumbar interbody fusion (OLIF) procedures has continued to rise over recent years. Adjacent segment degeneration (ASD) is a common complication following vertebral body fusion. Although the precise mechanism remains uncertain, ASD has gradually become more common in OLIF. Therefore, the present study analyzed the association between disc degeneration and OLIF to explore whether adjacent degeneration was promoted by OLIF in degenerative disc disease., Methods: A three-dimensional nonlinear finite element (FE) model of the L3-S1 lumbar spine was developed and validated. Three lumbar spine degeneration models with different degrees of degeneration (mild, moderate and severe) and a model of OLIF surgery were constructed at the L4-L5 level. When subjected to a follower compressive load (500 N), hybrid moment loading was applied to all models of the lumbar spine and the range of motion (ROM), intradiscal pressure (IDP), facet joint force (FJF), average mises stress in the annulus (AMSA), average tresca stress in the annulus (ATSA) and average endplate stress (AES) were measured., Results: Compared with the healthy lumbar spine model, the ROM, IDP, FJF, AMSA, ATSA and AES of the segments adjacent to the degenerated segment increased in each posture as the degree of disc degeneration increased. In different directions of motion, the ROM, IDP, FJF, AMSA, ATSA and AES in the OLIF model in the L3-L4 and L5-S1 segments were higher than those of the healthy model and each degenerated model. Compared with the healthy model, the largest relative increase in biomechanical parameters above (ROM, IDP, FJF, AMSA, ATSA or AES) was observed in the L3-L4 segment in the OLIF model, of 77.13%, 32.63%, 237.19%, 45.36%, 110.92% and 80.28%, respectively. In the L5-S1 segment the corresponding values were 68.88%, 36.12%, 147.24%, 46.00%, 45.88% and 51.29%, respectively., Conclusions: Both degenerated discs and OLIF surgery modified the pattern of motion and load distribution of adjacent segments (L3-L4 and L5-S1 segments). The increases in the biomechanical parameters of segments adjacent to the surgical segment in the OLIF model were more apparent than those of the degenerated models. In summary, OLIF risked accelerating the degeneration of segments adjacent to those of a surgical segment., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Objective: To summarize the research progress of ureteral injury in oblique lumbar interbody fusion (OLIF)., Methods: The literature about incidence, clinical manifestations, diagnosis, and treatment of ureteral injury complications in OLIF was reviewed., Results: OLIF surgery poses a risk of ureteral injury because its surgical approach is anatomically adjacent to the left ureter. Ureteral injuries in OLIF are often insidious and have no specific clinical manifestations. CT urography is a common diagnostic method. The treatment of ureteral injury depends on a variety of factors such as the time of diagnosis, the location and degree of injury, and the treatment methods range from endoscopic treatment to replacement reconstruction., Conclusion: Surgeons should pay attention not to damage the ureter and find the abnormality in time during OLIF. High vigilance of abnormalities is conducive to the early diagnosis of ureteral injury. Furthermore, it is important to be familiar with ureter anatomy and gentle operation to prevent ureteral injury.

Introduction: An anterior surgical approach for severe infectious spondylodiscitis in the lumbar region is optimal but not always atraumatic. The aim of this study was to evaluate the efficacy and safety of a minimal anterior-lateral retroperitoneal approach, also known as a surgical approach for oblique lumbar interbody fusion, for cases with severe infectious spondylodiscitis with osseous defects., Methods: Twenty-four consecutive patients who underwent anterior debridement and spinal fusion with an autologous strut bone graft for infectious spondylodiscitis with osseous defects were reviewed retrospectively. Eleven patients underwent the minimal retroperitoneal approach (Group M), and 13 underwent the conventional open approach (Group C). Peri- and postoperative clinical outcomes, that is, estimated blood loss (EBL), operative time (OT), creatine kinase (CK) level, visual analog scale (VAS), and rates of bone union and additional posterior instrumentation, were evaluated, and the differences between both groups were assessed statistically., Results: Mean EBL, serum CK on the 1 st postoperative day, and VAS on the 14 th postoperative day were 202.1 mL, 390.9 IU/L, and 9.5 mm in Group M and 648.3 mL, 925.5 IU/L, and 22.3 mm in Group C, respectively, with statistically significant differences between the groups. There were no statistically significant intergroup differences in OT and rates of bone union and additional posterior instrumentation., Conclusions: Anterior debridement and spinal fusion using the minimal retroperitoneal approach is a useful and safe surgical technique. Although a preponderance of the minimal approach regarding early bone union is not validated, this technique has the advantages of conventional open surgery, but reduces blood loss, muscle injury, and pain postoperatively., Competing Interests: Conflicts of Interest: The authors declare that there are no relevant conflicts of interest., (Copyright © 2021 by The Japanese Society for Spine Surgery and Related Research.)

Objective: Over the last few decades, many surgical techniques for lumbar interbody fusion have been reported. The anterior-to-psoas (ATP) approach is theoretically supposed to benefit from the advantages of both anterior and lateral approaches with similar complication rates, even in L5-S1. At this segment, the anterior lumbar interbody fusion (ALIF) requires retroperitoneal dissection and retraction of major vessels, whereas the iliac crest does not allow the lateral transpsoas approach. This study aimed to investigate clinical-radiological outcomes and complications of the ATP approach at the L5-S1 segment in a single cohort of patients., Methods: This is a prospective single-center study, conducted from 2016 to 2019. Consecutive patients who underwent ATP at the L5-S1 segment for degenerative disc disease or revision surgery after previous posterior procedures were considered for eligibility. Complete clinical-radiological documentation and a minimum follow-up of 12 months were set as inclusion criteria. Clinical patient-reported outcomes, such as the visual analog scale for low-back pain, Oswestry Disability Index, and 36-Item Short Form Health Survey (SF-36) scores, as well as spinopelvic parameters, were collected preoperatively, 6 weeks after surgery, and at the last follow-up visit. Intraoperative and perioperative complications were recorded. The fusion rate was evaluated on CT scans obtained at 12 months postoperatively., Results: Thirty-two patients met the inclusion criteria. The mean age at the time of surgery was 57.6 years (range 44-75 years). The mean follow-up was 33.1 months (range 13-48 months). The mean pre- and postoperative visual analog scale (7.9 ± 1.3 vs 2.4 ± 0.8, p < 0.05), Oswestry Disability Index (52.8 ± 14.4 vs 22.9 ± 6.0, p < 0.05), and SF-36 (37.3 ± 5.8 vs 69.8 ± 6.1, p < 0.05) scores significantly improved. The mean lumbar lordosis and L5-S1 segmental lordosis significantly increased after surgery. The mean pelvic incidence-lumbar lordosis mismatch and pelvic tilt significantly decreased. No intraoperative complications and a postoperative complication rate of 9.4% were recorded. The fusion rate was 96.9%. One patient needed a second posterior revision surgery for residual foraminal stenosis., Conclusions: In the present case series, ATP fusion for the L5-S1 segment has resulted in valuable clinical-radiological outcomes and a relatively low complication rate. Properly designed clinical and comparative trials are needed to further investigate the role of ATP for different L5-S1 conditions.

Objective: To assess the clinical effect of oblique lumbar interbody fusion (OLIF) combined with posterior surgery via Wiltse approach for adult degenerative scoliosis. Methods: The clinical data of 27 patients with adult degenerative scoliosis who received OLIF operation from April 2015 to June 2018 in Tongji Hospital were analyzed retrospectively. There were 17 males and 10 females with an average age of (54±11) years. All patients were treated with OLIF combined with pedicle screw fixation via Wiltse approach. Operation time, blood loss and surgery complications were all recorded. Clinical and radiographic evaluation were investigated at 1 week, 3 months of post operation and final follow-up. Visual analog scale (VAS) for low back pain and leg pain, Oswestry disability index (ODI) for low back pain were used to evaluate the clinical efficacy of surgery. Lumbar coronal cobb angle, lumbar lordosis (LL), pelvic tilt (PT), mismatch of PI and PT, sagittal vertical axis (SVA) were investigated with full spine standing X-ray. The data were compared with factor analysis of variance. Results: All patients were followed-up for 6-52 months ((30±5) months). The operation time was (235±33) min, the blood loss was (433±62) ml. VAS for low back pain and eg pain and the ODI were significantly improved from 6.8±1.4, 7.3±1.4 and 71%±11% preoperatively to 1.1±1.2, 1.0±0.9 and 17%±6% at the latest follow-up ( F= 115.302,139.855,291.198, all P< 0.05).Lumbar coronal Cobb angle of patients was reduced from 28°±8° preoperatively to 9°±4° at the latest follow-up ( F= 66.352, P< 0.05). The LL was significantly increased from 20°±11° preoperatively to 33°±7° ( F= 17.678, P< 0.05), and PT, PI-LL and SVA were significantly increased from 31°±6°,35°±12° and (90±29) mm preoperatively to 26°±5°, 21°±6° and (32±17) mm at the latest follow-up ( F= 6.211,23.809,53.372, all P< 0.05). There was no severe vascular andnerve injuries during and after operation. Conclusion: OLIF combined with posterior surgery via Wiltse approach is a safe and effective operation in the treatment of adult degenerative scoliosis with mild to moderate sagittal imbalance, it can correct the coronal and sagittal deformity, and achieve less surgery injury, less complications and good clinical results.

Objective: To compare the clinical and radiological effectiveness of oblique lumbar interbody fusion (OLIF) and posterior lumbar interbody fusion (PLIF) in the treatment of Cage dislodgement after lumbar surgery., Methods: The clinical data of 40 patients who underwent revision surgery due to Cage dislodgement after lumbar surgery betweem April 2013 and March 2017 were retrospectively analyzed. Among them, 18 patients underwent OLIF (OLIF group) and 22 patients underwent PLIF (PLIF group) for revision. There was no significant difference between the two groups in age, gender, body mass index, intervals between primary surgery and revision surgery, number of primary fused levels, disc spaces of Cage dislodgement, and visual analogue scale (VAS) scores of low back pain and leg pain, Oswestry disability index (ODI), the segmental lordosis (SL) and disc height (DH) of the disc space of Cage dislodgement, and the lumbar lordosis (LL) before revision ( P >0.05). The operation time, intraoperative blood loss, hospital stay, and complications of the two groups were recorded and compared. The VAS scores of low back pain and leg pain were evaluated at 3 days, 3, 6, and 12 months after operation, and the ODI scores were evaluated at 3, 6, and 12 months after operation. The SL and DH of the disc space of Cage dislodgement and LL were measured at 12 months after operation and compared with those before operation. CT examination was performed at 12 months after operation, and the fusion of the disc space implanted with new Cage was judged by Bridwell grading standard., Results: The intraoperative blood loss in the OLIF group was significantly less than that in the PLIF group ( t =-12.425, P =0.000); there was no significant difference between the two groups in the operation time and hospital stay ( P >0.05). Both groups were followed up 12-30 months, with an average of 18 months. In the OLIF group, 2 patients (11.1%) had thigh numbness and 1 patient (5.6%) had hip flexor weakness after operation; 2 patients (9.1%) in the PLIF group had intraoperative dural sac tear. The other patients' incisions healed by first intention without early postoperative complications. There was no significant difference in the incidence of complications between the two groups ( χ 2 =0.519, P =0.642). The VAS scores of low back pain and leg pain, and the ODI score of the two groups at each time point after operation were significantly improved when compared with those before operation ( P <0.05); there was no significant difference between the two groups at each time point after operation ( P >0.05). At 12 months after operation, SL, LL, and DH in the two groups were significantly increased when compared with preoperative ones ( P <0.05); SL and DH in the OLIF group were significantly improved when compared with those in the PLIF group ( P <0.05), and there was no significant difference in LL between the two groups ( P >0.05). CT examination at 12 months after operation showed that all the operated disc spaces achieved bony fusion. According to the Bridwell grading standard, 12 cases were grade Ⅰ and 6 cases were grade Ⅱ in the OLIF group, and 13 cases were grade Ⅰ and 9 cases were grade Ⅱ in the PLIF group; there was no significant difference between the two groups ( Z =-0.486, P =0.627). During follow-up, neither re-displacement or sinking of Cage, nor loosening or fracture of internal fixation occurred., Conclusion: OLIF and PLIF can achieve similar effectiveness in the treatment of Cage dislodgement after lumbar surgery. OLIF can further reduce intraoperative blood loss and restore the SL and DH of the disc space of Cage dislodgement better.

Aim: To compare the clinical and radiographic outcomes of percutaneous endoscopic-assisted lumbar interbody fusion (PELIF) versus oblique lumbar interbody fusion (OLIF) for the treatment of symptomatic low-grade lumbar spondylolisthesis. Material & methods: The clinical and radiographic records of 48 patients underwent single-level minimally invasive lumbar fusion with a PELIF (n = 16) or OLIF (n = 32) were reviewed. Results: The clinical and radiographic outcomes were similar in both groups. PELIF procedure exhibited superior capability of the enlargement of foraminal width, but inferior capability of the restoration of foraminal height than OLIF procedure. Conclusion: PELIF minimizes the iatrogenic damages and perioperative risks to a great extent, and seems to be a promising option for the treatment of symptomatic low-grade lumbar spondylolisthesis.

Objective: Obese patients have been shown to have longer operative times and more complications from surgery. However, for obese patients undergoing minimally invasive surgery, these differences may not be as significant. In the lateral position, it is thought that obesity is less of an issue because gravity pulls the visceral fat away from the spine; however, this observation is primarily anecdotal and based on expert opinion. The authors performed oblique lumbar interbody fusion (OLIF) and they report on the perioperative morbidity in obese and nonobese patients., Methods: The authors conducted a retrospective review of patients who underwent OLIF performed by 3 spine surgeons and 1 vascular surgeon at the University of California, San Francisco, from 2013 to 2018. Data collected included demographic variables; approach-related factors such as operative time, blood loss, and expected temporary approach-related sequelae; and overall complications. Patients were categorized according to their body mass index (BMI). Obesity was defined as a BMI ≥ 30 kg/m2, and severe obesity was defined as a BMI ≥ 35 kg/m2., Results: There were 238 patients (95 males and 143 females). There were no significant differences between the obese and nonobese groups in terms of sex, levels fused, or smoking status. For the entire cohort, there was no difference in operative time, blood loss, or complications when comparing obese and nonobese patients. However, a subset analysis of the 77 multilevel OLIFs that included L5-S1 demonstrated that the operative times for the nonobese group was 223.55 ± 57.93 minutes, whereas it was 273.75 ± 90.07 minutes for the obese group (p = 0.004). In this subset, the expected approach-related sequela rate was 13.2% for the nonobese group, whereas it was 33.3% for the obese group (p = 0.039). However, the two groups had similar blood loss (p = 0.476) and complication rates (p = 0.876)., Conclusions: Obesity and morbid obesity generally do not increase the operative time, blood loss, approach-related sequelae, or complications following OLIF. However, obese patients who undergo multilevel OLIF that includes the L5-S1 level do have longer operative times or a higher rate of expected approach-related sequelae. Obesity should not be considered a contraindication to multilevel OLIF, but patients should be informed of potentially increased morbidity if the L5-S1 level is to be included.

Objectives: To evaluate the effect of minimally invasive lateral lumbar interbody fusion (LLIF/OLIF) on the sagittal balance of adult degenerative scoliosis. Methods: From January 2014 to June 2017, a total of 23 patients with degenerative scoliosis underwent staged minimally invasive surgery in Shanghai Ruijin Hospital. All patients were implanted with LLIF or OLIF cage from the lateral approach first, and was followed by the posterior percutaneous pedicle screw fixation or pedicle screw fixation via Wiltse approach. If the sagittal deformity correction was not satisfactory after the first surgery, a posterior osteotomy can be performed during the second stage operation. A biplanar X-ray of the whole spine was taken with the EOS imaging system before and after surgery. The EOS software was used to measure and evaluate the patient's sagittal balance parameters including pelvic incidence (PI), pelvic tilt (PT), lumbar lordosis (LL), the sagittal vertical axis (SVA) and the coronal Cobb angle. The visual analogue scale (VAS) score for low back pain, the Oswestry Disability Index (ODI) score were evaluated before and after surgery. Paired t test or repeated measures ANOVA was used to compare the data before and after surgery. Results: There were 6 males and 17 females with a mean age of (72±4) years (62-79 years). Nine patients were treated with LLIF and 14 patients with OLIF. Sixteen cases were implanted with three cages, five with two cages and two with four cages. The mean follow-up period was 24.2 months (15-42 months). After the first operation, the Cobb angle of the patient was significantly improved (18°±7° vs 33°±8°, t= 13.2, P< 0.01). All the parameters for sagittal balance, including PI-LL (20°±8° vs 31°±8(o)), SVA ((5.3±2.0) cm vs (8.2±3.5) cm), PT (16°±6° vs 23°±4°) were all significantly improved as well ( t= 6.8, 4.5, 9.0, ALL P< 0.01). At the last follow-up, the VAS score of low back pain (3.4±1.1 vs 6.3±1.0) and ODI scores (27.3%±3.0% vs 47.1%±5.9%) were also significantly improved ( t= 11.3, 17.8, both P< 0.01). No major complications occurred in this group. Conclusions: Minimally invasive LLIF/OLIF can significantly improve the coronal and sagittal balance of adult degenerative scoliosis. Staged minimally invasive surgery can significantly alleviate pain and improve function in these patients.

Adult spinal deformity (ASD) is an increasing disease entity as the population ages. An emerging minimally invasive surgery (MIS) option for the treatment of ASD is the oblique lumbar interbody fusion (OLIF), which allows indirect foraminal decompression of stenosis as well as segmental deformity correction (DiGiorgio et al., 2017). The authors utilize computer-assisted navigation with OLIF to reduce radiation exposure and improve time efficiency. The authors present a video of navigated oblique lumbar interbody fusion at L3-5 followed by open posterior screw-rod fixation. The video can be found here: https://youtu.be/zKDT7PhMYf8., Competing Interests: Disclosures The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this publication., (© 2020, Chih-Chang Chang, Joshua Rivera, Brenton Pennicooke, Dean Chou, and Praveen V. Mummaneni.)

Aim: To compare the outcomes of minimally invasive surgery (MIS) for degenerative spondylolisthesis transforaminal lumbar interbody fusion (TLIF) and oblique lumbar interbody fusion (OLIF). Materials & methods: The clinical and surgical characteristics and outcomes of 38 patients with MIS-OLIF and 55 with MIS-TLIF were retrospectively evaluated. Results: Procedures and hospital stay were shorter and blood loss was less, with MIS-OLIF than with MIS-OLIF. The clinical and radiographic outcomes were similar. Postoperative changes in disk height and foraminal dimension were greater and patient satisfaction was better with MIS-OLIF than with MIS-TLIF. Conclusion: The clinical findings associated with the two procedures were similar; but patients preferred MIS-OLIF, which is less invasive, to MIS-TLIF. Clinical trial registration number: ChiCTR1800019443.

Objective: To summarize the guiding role of imaging evaluation of oblique lumbar interbody fusion (OLIF) in recent years., Methods: The reports of OLIF surgical imaging research at home and abroad in recent years were extensively reviewed and analyzed., Results: Preoperative imaging evaluation plays an important role in guiding the operation of OLIF, the placement of fusion Cage, the selection of indications, and the reduction of complications., Conclusion: Detailed preoperative imaging evaluation can correctly estimate the indications of OLIF, and avoid the nerve, blood vessel, and muscle injuries.

Study Design: Prospective, single-center study., Purpose: The current trend of operative treatment for adult spinal deformity (ASD) is combined anterior-posterior staged surgery. When anterior surgery was first performed, oblique lumbar interbody fusion (OLIF) was employed; this method became increasing popular. This study aimed to determine the lordosis correction that can be achieved using OLIF and assess whether we can preoperatively predict the lordosis correction angle achieved using OLIF., Overview of Literature: Many previous studies on OLIF have shown improved clinical and radiologic outcomes. With the increase in the popularity of OLIF, several surgeons have started using larger cages to attain greater lordosis correction. Moreover, some studies have reported complications of OLIF because of immoderate cage insertion. To our knowledge, this is the first prospective study that attempted to determine whether it is possible to predict the lordosis correction angle achieved with OLIF preoperatively, using fullextension lateral view (FELV)., Methods: Forty-six patients with ASD were enrolled. All the operations were performed by a single surgeon in two stages (first, anterior and second, posterior) with a 1-week interval. Radiological evaluation was performed by comparing the Cobb's angle of the segmental and regional lordosis obtained using preoperative and postoperative simple radiography (including the FELV) and magnetic resonance imaging (MRI)., Results: Regional lordosis (L1-S1) in the whole-spine standing lateral radiograph was -3.03°; however, in the supine lateral MRI, it was 20.92°. The regional lordosis of whole-spine standing lateral and supine lateral (MRI) was significantly different. In the FELV, regional lordosis was 25.72° and that in the postoperative supine lateral (MRI) was 25.02°; these values were not significantly different., Conclusions: Although OLIF offers many advantages, it alone plays a limited role in ASD treatment. Lordosis correction using OLIF as well as lordosis determined in the FELV was possible. Hence, our results suggest that FELV can help predict the lordosis correction angle preoperatively and thus aid the selection of the appropriate technique in the second staged operation.

Objectives: To describe perioperative complications occurring during oblique lumbar interbody fusion (OLIF) assisted by a retractor system for degenerative lumbar diseases., Patients and Methods: The perioperative complications in 113 cases series utilizing a minimally invasive approach were recorded and analyzed. One hundred thirteen patients who received OLIF for degenerative lumbar diseases between November 2014 and February 2017 at a single center were evaluated. The most frequent diagnosis was spondylolisthesis (59 cases, 52.2%), followed by lumbar instability (24 cases, 21.2%), adjacent segmental disease (12 cases, 10.6%), adult degenerative scoliosis (11 cases, 9.8%) and discogenic low back pain (7 cases, 6.2%). One hundred thirty-four levels were treated, 88.5% one-level, 4.4% two-level, and 7.1% three-level surgeries. The most fused level was L4-5 (94 levels, 70.2%), followed by L3-4 (31 levels, 23.1%), and L2-3 (9 levels, 6.7%)., Results: All perioperative complications only included adverse events related to the OLIF procedure. The most observed complications were donor-site pain (24 cases, 21.2%), followed by vertebral endplate fracture (15 cases, 13.3%), thigh numbness/pain (12 cases, 10.6%), psoas/quadriceps weakness (5 cases, 4.4%), sympathetic nerve injury (2 case, 1.8%), paralytic ileus (one case, 0.9%), segmental artery injury (one case, 0.9%), intervertebral infection (one, 0.9%), and contralateral femoral nerve palsy (one, 0.9%). All complications, including postoperative ipsilateral or contralateral thigh paresthesia, pain, and psoas/quadriceps weakness, were observed when operating at L4-L5. The incidence of complications excluding donor-site pain was 24.8% (28/113 cases). The patients with donor-site pain, thigh numbness/pain, psoas/quadriceps weakness, sympathetic nerve injury and paralytic ileus recovered within two months following surgery. The patient with intervertebral infection recovered at 3 months after surgery. One case of contralateral femoral nerve palsy recovered completely with no residual sensory or motor deficit at 6 months., Conclusions: OLIF performed using a retractor system is a validated option to treat a wide spectrum of degenerative lumbar diseases with few perioperative complications and a quick recovery. Judicious use of this technique at the L4/5 level is recommended. Close attention to detail during the procedure can minimize complications that may be associated with the learning curve., (Copyright © 2019. Published by Elsevier B.V.)

Study Design: Retrospective, single-center study., Purpose: We aimed to determine the perioperative complications of oblique lumbar interbody fusion (OLIF) as a first-stage procedure in combined anterior and posterior operation for adult spinal deformity (ASD) along with sagittal imbalance. Specifically, we aimed to identify the radiological and clinical types of perioperative surgical complications and the factors affecting these complications., Overview of Literature: OLIF has recently gained popularity, and there are several reports of good outcomes and only a few of complications with OLIF; however, a few studies have focused on the perioperative surgical complications of ASD along with sagittal imbalance., Methods: The perioperative period was a 1-week interval between the anterior and posterior procedures. All patients underwent simple radiography and magnetic resonance imaging preoperatively and postoperatively. Cage placement was evaluated for displacement (i.e., subsidence and migration) and vertebral body fracture. Clinical patient complaints were evaluated perioperatively. Student t-test was used for data analysis., Results: A total of 46 patients were included, totaling 138 fusion segments. A week after OLIF, 14 patients/33 segments (30.4%/23.9%) demonstrated endplate injury-associated cage placement change. Subsidence was the most common cage placement-related complication. As compared with patients without endplate injury, those with endplate injuries showed significantly larger correction angles and a higher proportion of them had larger height cages than the disk height in the full-extension lateral view. Although 32.6% of the patients experienced perioperative clinical complications, they were relatively minor and transient. The most common complication was severe postoperative pain (Visual Analog Scale score of >7), and hip flexor weakness spontaneously resolved within 1 week., Conclusions: OLIF yielded more than expected endplate injuries from treatment modalities for ASD along with sagittal imbalance. Therefore, surgeons should be cautious about endplate injury during OLIF procedures. It is difficult to accomplish lordosis correction via OLIF alone; therefore, surgeons should not attempt this impractical correction goal and insert an immoderate cage.

Introduction: Minimally invasive spine-oblique lumbar interbody fusion (MIS-OLIF) has emerged as a novel anterolateral, retroperitoneal, "pre-psoas" approach for lumbar interbody fusion for degenerative spinal instability, as well as for correction of deformity in patients without severe canal stenosis. In the last decade, the technique has gained popularity owing to several advantages like the minimal blood loss, minimal tissue dissection, preservation of posterior tension bands, better biomechanical strength, provision of mechanical stability to the lumbar spine, and a larger footprint of the implant, associated with it. It, thus, maximises load bearing on the cortical bone, and provides a better lordotic correction of the lumbar spine. The armamentarium is further boosted by the use of neuro-navigation and neuro-monitoring tools, thereby improving the surgical outcome., Material and Methods: The clinical indications of MIS-OLIF and various fixation methods [lateral lumbar fixation (LLF) and percutaneous posterior pedicle fixation (PPF)] are discussed. The summary of the 15 patients on whom the technique was utilized, are discussed. The patients' demographics, clinical history and neurological examination data, pre- operative Oswestry disability index (ODI) and visual analogue scale (VAS) score, intraoperative surgical details and postoperative follow up clinical as well as radiological data were assessed. Complications, readmissions, length of stay, estimated blood loss, surgical time and surgical outcome were also recorded., Results: 11 cases had grade 1 spondylolisthesis and 4 had grade 2 spondylolisthesis. One patient had both grade I and II spondylolisthesis at different levels. 13 patients had improvement in mechanical back pain and neurogenic claudication. Two patients had improvement in back pain but one-sided limb radiculopathy persisted, which was treated conservatively. The mean pre-operative ODI score was 35 ± 6.1, which improved to 14.6 ± 4.1 at follow-up (range of follow-up: 1 to 10 months; mean 5.7 ± 3.3 months]. The mean pre-operative VAS score was 7 ± 0.7, which improved to 3.3 ± 0.4 at follow-up., Conclusions: The MIS-OLIF technique at the L2-L5 levels has shown encouraging early surgical outcomes with a good fusion rate and rapid recovery. While utilizing the unfamiliar oblique trajectory, the use of navigation can guide the surgeon in real time and also help in reducing the radiation exposure., Competing Interests: There are no conflicts of interest

Background: To investigate changes of oblique corridor in patients with lumbar degenerative scoliosis and determine proper working angle with respect to the direction of vertebral axial rotation during the oblique lumbar interbody fusion procedure., Methods: The distance of oblique corridor and the rotational angle of the left or right apex group were measured on axial T2 magnetic resonance images and then compared with those of the propensity score-matched control group., Results: Fifty-five patients of the left apex group and 57 patients of the right apex group were compared with the equal number of patients of the propensity score-matched control group. The distance of oblique corridor in the left apex group was shorter than that in the control group at the levels of L1-2 and L2-3. In contrast, the distance of oblique corridor in the right apex group was longer than that of the control group at the level of L2-3. Patients of the left apex group showed the vertebral body rotating to the left side from L1-2 to L5-S1, whereas in the right apex group, the vertebral body rotated to the right side at the levels of L1-2, L2-3, and L3-4., Conclusions: In the left apex group, the oblique corridor was decreased from psoas overlap, and coupled axial rotation to the left side might increase the risk of contralateral nerve root injury during orthogonally working. Thus, surgeons should pay attention to the state of coupled vertebral axial rotation of lumbar degenerative scoliosis for the oblique lumbar interbody fusion procedure., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Objectives: The advent of minimally invasive, percutaneous techniques for the placement of pedicle screws has led to the evolution of a popular treatment paradigm: anterior or lateral interbody fusions followed by posterior percutaneous pedicle screw placement. We present the operative technique for anterior-to-psoas lateral interbody fusion (ATP-LIF) with simultaneous posterior lumbar percutaneous pedicle screw fixation using intraoperative CT-guided navigation., Patients and Methods: This technique capitalizes both on the more oblique approach used in the ATP-LIF procedure, as well as the anatomic clarity gleaned from intraoperative CT-guided navigation, to allow for simultaneous placement of pedicle screws in the lateral position without the need for guiding fluoroscopy., Results: The parallel execution of both procedures, in the lateral position, reduces operative time, consolidates a two-stage procedure into one stage, and eliminates the need for prone re-positioning. The use of intraoperative CT-guided navigation reduces the need for fluoroscopy and overall radiation exposure while allowing for pedicle screw placement and the-LIF procedure in truly simultaneous fashion. In this pilot study, a total of 14 pedicle screws were placed with two lateral breaches (14%)., Conclusion: Simultaneous Lateral Interbody and Pedicle Screws (SLIPS) represents a meaningful evolution of the newly reported single-position lateral interbody fusion with posterior percutaneous pedicle screw fixation., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Background Oblique lumbar interbody fusion is a commonly used surgical method of achieving lumbar interbody fusion. There have been some reports about complications of oblique lumbar interbody fusion at the L2–L3 level. However, to our knowledge, there have been no reports about ureter injury during oblique lumbar interbody fusion. We report a case of ureter injury during oblique lumbar interbody fusion to share our experience. Case Description A 78-year-old male patient presented with a history of lower back pain and neurogenic intermittent claudication. He was diagnosed with spinal stenosis at L2–L3, L4–L5 level and spondylolisthesis at L4–L5 level. Symptoms were not improved after several months of medical treatments. Then, oblique lumbar interbody fusion was performed at L2–L3, L4–L5 level. During the surgery, anesthesiologist noticed hematuria. A retrourethrogram was performed immediately by urologist, and ureter injury was found. Ureteroureterostomy and double-J catheter insertion were performed. The patient was discharged 2 weeks after surgery without urologic or neurologic complications. At 2 months after surgery, an intravenous pyelogram was performed, which showed an intact ureter. Conclusions Our study shows that a low threshold of suspicion of ureter injury and careful manipulation of retroperitoneal fat can be helpful to prevent ureter injury during oblique lumbar interbody fusion at the upper level. [ABSTRACT FROM AUTHOR]

Study Design: Retrospective clinical study., Objectives: The aim of this study was to compare intraoperative conditions and clinical results of patients undergoing pre-psoas oblique lateral interbody fusion (OLIF) using navigation or conventional fluoroscopy (C-ARM) techniques., Methods: Forty-two patients (22 patients by navigation and 20 by fluoroscopy) underwent the OLIF procedure at 2 medical centers, and records were reviewed. Clinical data was collected and compared between the 2 groups. Patients were followed-up with a range of 6 to 24 months., Results: There were no significant differences on demographic data between groups. The navigation group had zero radiation exposure (RE) to the surgeon and radiation time compared to the C-ARM group, with total RE of 44.59 ± 26.65 mGy and radiation time of 88.30 ± 58.28 seconds ( P < .05). The RE to the patient was significantly lower in the O-ARM group (9.38 mGy) compared to the C-ARM group (44.59 ± 26.65 mGy). Operating room time was slightly longer in the navigation group (2.49 ± 1.35 hours) compared to the C-ARM group (2.30 ± 1.17 hours; P > .05), although not statistically significant. No differences were found in estimated blood loss, length of hospitalization, surgery-related complications, and outcome scores with an average of 8-month follow-up., Conclusions: Compared with C-ARM techniques, using navigation can eliminate RE to surgeon and decrease RE to the patient, and it had no significant effect on operating time, estimated blood loss, length of hospitalization, or perioperative complications in the patients with OLIF procedure. This study shows that navigation is a safe alternative to fluoroscopy during the OLIF procedure in the treatment of degenerative lumbar conditions., Competing Interests: Declaration of Conflicting Interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Background: An approach to lateral lumbar interbody fusion (LLIF) utilizing an oblique corridor anterior to the psoas muscle was first described by Mayer in 1997 and subsequently by other authors. The only consistent structure of note in this corridor is the lumbar sympathetic trunk (LST), which at times must be mobilized in order to perform a discectomy and interbody fusion, thereby placing the LST at risk. This study was designed to describe the morphometric anatomy of the LST in relation to surgically relevant landmarks for the anterolateral approach to the lumbar spine at L3/L4 to L5/S1., Methods: Twenty-four embalmed cadavers (13 males, 11 females, age range, 50-89) were dissected to expose the LST. Bilateral measurements were recorded using a calliper under direct visualization, using the midsagittal plane of the lumbar spine as the reference landmark. The points were then marked with radio-opaque needles, and 14 cadavers were scanned with CT to validate the measurements., Results: Of 48 LSTs, there was minimal difference in the direction of its course between sides; 14/24 specimens had concordant directions. The majority (n=28) had a medial to lateral cephalocaudal course. If osteophytes were present at the L4/L5 level, the majority of LSTs (n=7, of 8) were displaced lateral to the osteophyte. At the L5/S1 level, half of the cases with osteophytes (n=3, of 6) stretched the LST over the top of the osteophyte. The LST was adherent to the L4/L5 disc space bilaterally in 93% of cases., Conclusions: With the development of lumbar fusion techniques which utilize an oblique corridor and the retraction of psoas muscle, LST has become an important neural structure to define, protect and mobilize. In our morphometric analysis of 24 specimens, the position has been identified and quantified, and this paper notes variations, particularly distortions caused by degenerative processes. In this study, the LST ran in a medial to lateral direction from L3 to S1, and osteophytes typically displace and adhere to the LST., Competing Interests: Conflicts of Interest: The authors have no conflicts of interest to declare.

OBJECTIVE Direct neural decompression cannot be achieved by performing lateral lumbar interbody fusion (LLIF). To overcome the indirect decompressive effect of LLIF, additional endoscopic discectomy with oblique lumbar interbody fusion (OLIF) has been attempted. The purpose of this study was to assess the clinical and radiological outcomes of patients who underwent OLIF with additional endoscopic discectomy. METHODS Spinal endoscopic discectomy-assisted OLIF was attempted to remove herniated disc material. Only patients with a follow-up time that exceeded 12 months were enrolled. Clinical parameters examined were the Oswestry Disability Index and visual analog scale scores of back and leg pain. Postoperative MRI was also performed. RESULTS Fourteen patients were enrolled. Central and foraminal disc herniations were evident in 8 and 6 patients, respectively. Concomitant central or foraminal herniated discs were removed completely after additional endoscopic discectomy, and disc removal was confirmed by postoperative MRI. Mean preoperative visual analog scale scores and Oswestry Disability Index scores improved postoperatively. CONCLUSIONS OLIF with additional endoscopic discectomy results in successful direct neural decompression without posterior decompressive procedures. Endoscopic assistance might overcome the limitations of LLIF.

Lumbar interbody fusion is an important technique for the treatment of degenerative disc disease and degenerative scoliosis. The oblique lumbar interbody fusion (OLIF) establishes a minimally invasive retroperitoneal exposure anterior to the psoas and lumbar plexus. In this video case presentation, the authors demonstrate the techniques of the OLIF at L5-S1 performed on a 69-year-old female with degenerative scoliosis as one component of an overall strategy for her deformity correction. The video can be found here: https://youtu.be/VMUYWKLAl0g .

OBJECT The purpose of this study was to analyze MR images of the lumbar spine and document: 1) the oblique corridor at each lumbar disc level between the psoas muscle and the great vessels, and 2) oblique access to the L5-S1 disc space. Access to the lumbar spine without disruption of the psoas muscle could translate into decreased frequency of postoperative neurological complications observed after a transpsoas approach. The authors investigated the retroperitoneal oblique corridor of L2-S1 as a means of surgical access to the intervertebral discs. This oblique approach avoids the psoas muscle and is a safe and potentially superior alternative to the lateral transpsoas approach used by many surgeons. METHODS One hundred thirty-three MRI studies performed between May 4, 2012, and February 27, 2013, were randomly selected from the authors' database. Thirty-three MR images were excluded due to technical issues or altered lumbar anatomy due to previous spine surgery. The oblique corridor was defined as the distance between the left lateral border of the aorta (or iliac artery) and the anterior medial border of the psoas. The L5-S1 oblique corridor was defined transversely from the midsagittal line of the inferior endplate of L-5 to the medial border of the left common iliac vessel (axial view) and vertically to the first vascular structure that crossed midline (sagittal view). RESULTS The oblique corridor measurements to the L2-5 discs have the following mean distances: L2-3 = 16.04 mm, L3-4 = 14.21 mm, and L4-5 = 10.28 mm. The L5-S1 corridor mean distance was 10 mm between midline and left common iliac vessel, and 10.13 mm from the first midline vessel to the inferior endplate of L-5. The bifurcation of the aorta and confluence of the vena cava were also analyzed in this study. The aortic bifurcation was found at the L-3 vertebral body in 2% of the MR images, at the L3-4 disc in 5%, at the L-4 vertebral body in 43%, at the L4-5 disc in 11%, and at the L-5 vertebral body in 9%. The confluence of the iliac veins was found at lower levels: 45% at the L-4 level, 19.39% at the L4-5 intervertebral disc, and 34% at the L-5 vertebral body. CONCLUSIONS An oblique corridor of access to the L2-5 discs was found in 90% of the MR images (99% access to L2-3, 100% access to L3-4, and 91% access to L4-5). Access to the L5-S1 disc was also established in 69% of the MR images analyzed. The lower the confluence of iliac veins, the less probable it was that access to the L5-S1 intervertebral disc space was observed. These findings support the use of lumbar MRI as a tool to predetermine the presence of an oblique corridor for access to the L2-S1 intervertebral disc spaces prior to lumbar spine surgery.