Interbody Placement Research Articles

Three-column osteotomy in long constructs has lower rates of proximal junctional kyphosis and better restoration of lumbar lordosis than anterior column realignment.

Three-column osteotomies (TCOs) and minimally invasive techniques such as anterior column realignment (ACR) are powerful tools used to restore lumbar lordosis and sagittal alignment. We aimed to appraise the differences in construct and global spinal stability between TCOs and ACRs in long constructs. We identified consecutive patients who underwent a long construct lumbar or thoracolumbar fusion between January 2016 and November 2021. "Long construct" was any construct where the uppermost instrumented vertebra (UIV) was L2 or higher and the lowermost instrumented vertebra (LIV) was in the sacrum or ileum. We identified 69 patients; 14 (20.3%) developed PJK throughout follow-up (mean 838days). Female patients were less likely to suffer PJK (p = 0.009). TCO was more associated with open (versus minimally invasive) screw/rod placement, greater number of levels, higher UIV, greater rate of instrumentation to the ilium, and posterior (versus anterior) L5-S1 interbody placement versus the ACR cohort (p < 0.001, p < 0.001, p < 0.001, p < 0.001, p = 0.005, respectively). Patients who developed PJK were more likely to have undergone ACR (12 (32.4%) versus 2 (6.3%, p = 0.007)). The TCO cohort had better improvement of lumbar lordosis despite similar preoperative measurements (ACR: 16.8 ± 3.78°, TCO: 23.0 ± 5.02°, p = 0.046). Pelvic incidence-lumbar lordosis mismatch had greater improvement after TCO (ACR: 14.8 ± 4.02°, TCO: 21.5 ± 5.10°, p = 0.042). By multivariate analysis, ACR increased odds of PJK by 6.1-times (95% confidence interval: 1.20-31.2, p = 0.29). In patients with long constructs who undergo ACR or TCO, we experienced a 20% rate of PJK. TCO decreased PJK 6.1-times compared to ACR. TCO demonstrated greater improvement of some spinopelvic parameters.

Transforaminal lumbar interbody fusion with placement of steerable banana cage: A single-center retrospective analysis of radiographic parameters of success

IntroductionThe transforaminal lumbar interbody fusion (TLIF) is among the most utilized methods for the surgical treatment of lumbar degenerative disc disease. The TLIF has advanced significantly with several iterative changes since its inception in the early 1980s, with the advent of several generations of interbody types, shapes, and materials. Steerable curvilinear interbodies are among the most recent innovations in this space and may offer biomechanical advantages, namely in preservation of lumbar and segmental lordosis. While radiographic parameters have been investigated for other cage shapes and lumbar interbody fusion techniques, no study has investigated postoperative radiographic outcomes specific to TLIFs done with curvilinear interbodies. MethodsThis study is a retrospective review of TLIFs performed with curvilinear interbodies between 2019 and 2022 at a single institution. Upright radiographs were obtained preoperatively and at several timepoints postoperatively. Radiographic variables including interspace height and segmental lordosis were collected. Results26 surgeries with 32 curvilinear interbodies were performed across 3 years. There was significant increase in segmental lordosis at the L4-L5 (p = 0.0183) and L5-S1 levels (p = 0.004) as well as interspace height postoperatively at levels L3-L4 (p = 0.011) and L4-L5 (p = 0.002). Pain as measured with the numeric rating scale significantly improved in the overall cohort postoperatively (p<0.001). ConclusionsTLIF with curvilinear interbody placement increases segmental lordosis and interspace height at the L4-L5 and L5-S1 levels, and increased interspace height at the L3-L4 and L4-L5 levels. Further investigation into additional radiographic parameters is warranted and expanded cohort size would benefit deeper analysis of other spinal levels. Implications for practiceAs an increasing number of cage designs and materials are brought to market, studies such as this allow for better understanding of cage specific outcomes allowing for better informed device selection.

P138. Maintenance of alignment following adult spinal deformity surgery: a comparative analysis of the impact of utilization of supplemental rods relative to interbody placement

P138. Maintenance of alignment following adult spinal deformity surgery: a comparative analysis of the impact of utilization of supplemental rods relative to interbody placement

Comparing Posterior Lumbar Decompression and Fusion and Transforaminal Lumbar Interbody Fusion in Lumbar Degenerative Spondylolisthesis as Assessed by the CARDS Classification System

ObjectiveIn a retrospective cohort study, we compared the outcomes among clinical and radiographic degenerative spondylolisthesis (CARDS) subtypes for patients undergoing posterior lumbar decompression and fusion (PLDF) or transforaminal lumbar interbody fusion (TLIF) and evaluated the CARDS system as a tool to guide clinical decisions regarding the treatment of degenerative spondylolisthesis (DS). MethodsPatients undergoing PLDF or TLIF for DS from 2010 to 2020 were identified. The patients were grouped by the preoperative CARDS classification. Multivariate analysis was used to determine the effects of the treatment approach on the 1-year patient-reported outcome measures (PROMs) and 90-day surgical outcomes. ResultsA total of 1056 patients were included: 148 patients with type A DS, 323 with type B, 525 with type C, and 60 with type D. Patients with CARDS types A and C who underwent PLDF experienced a longer length of stay and were less likely to be discharged home. No differences were found in the incidence of revisions, complications, or readmissions between the surgical approaches. Patients with CARDS type A undergoing PLDF were less likely to achieve a minimal clinically important difference for back pain (36.8% vs. 76.7%; P = 0.013). No other significant differences were found in the PROMs among the CARDS subtypes. TLIF independently predicted for better leg pain improvement using the visual analog scale at 1 year of follow-up (β = −2.92; P = 0.017) for patients with CARDS type A. Multivariable analysis demonstrated no significant differences in PROMs by surgical approach among the other CARDS subtypes. ConclusionsPatients with disc space collapse and endplate apposition (CARDS type A) appear to benefit from TLIF. However, patients with lumbar spondylolisthesis without disc space collapse or kyphotic angulation (CARDS types B and C) showed no benefit from additional interbody placement.

489 Complications Associated With Single Position Prone Lateral Lumbar Interbody Fusion: A Systematic Review and Meta-Analysis

INTRODUCTION: Lateral lumbar interbody fusion (LLIF) is a workhorse surgical approach for lumbar arthrodesis. There is now emerging interest in performing single position surgery in which both LLIF and pedicle screw fixation are performed in the prone position. To date, most studies of prone LLIF are of poor quality and without long-term follow up; and as such, the complication profile related to this novel approach is not well known. METHODS: A systematic review of the literature and a meta-analysis were conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. All studies reporting prone LLIF were assessed for inclusion. Studies not reporting complication rates were excluded. RESULTS: A total of 10 studies met inclusion criteria and were included in the analysis. Overall, 286 patients were treated with prone LLIF across these studies with an average of 1.3 (0.2) levels per patient. There were 18 reported intra-operative complications including cage subsidence (3.8%), rupture of the anterior longitudinal ligament (ALL) (2.3%), cage repositioning (2.1%), aborted prone interbody placement (0.82%), and durotomy (0.6%). There were no reported major vascular or peritoneal injuries. A total of 68 post-operative complications occurred. These included thigh/groin sensory symptoms (13.3%), hip flexor weakness (17.8%), wound infection (1.9%), psoas hematoma (1.3%), motor neural injury (1.2%), and revision surgery (3.8%). CONCLUSIONS: Single position LLIF in the prone position appears to be a safe surgical approach with a low complication profile. Longer term follow up and prospective studies are needed in order to better characterize long-term complication rates related to this approach.

Maintenance of alignment following adult spinal deformity surgery: A comparative analysis of the impact of utilization of supplemental rods relative to interbody placement

Maintenance of alignment following adult spinal deformity surgery: A comparative analysis of the impact of utilization of supplemental rods relative to interbody placement

P23. Inline axial forces associated with implantation of ALIF interbody devices with integrated supplemental fixation

<h3>BACKGROUND CONTEXT</h3> Anterior lumbar interbody fusion (ALIF) allows for an optimal sized interboy device while providing correction for lumbar lordosis, restoration of disc height and indirect decompression. Spinal interbody devices with integrated fixation through blades, screws or other supplemental anchoring components mitigate the need for supplemental instrumentation, thus reducing OR time and preserving the stability of the functional spinal unit. Unfortunately, interbody devices have failed at the bone implant interface resulting in complications including implant migration and expulsion. Gaining a better understanding of the biomechanics associated with interbody placement may help to prevent these complications in the future. The aim of present study is to determine the magnitude and effect of axial forces during the deployment of an interbody device with supplemental integrated fixation. <h3>PURPOSE</h3> To understand the axial loading imparted to the functional spinal unit during lumbar interbody fusion surgery. <h3>STUDY DESIGN/SETTING</h3> Biomechanical axial load mesaurement in cadaveric functional spinal units during lumbar disc preparation and spinal interbody device implant procedures. <h3>METHODS</h3> Cadaveric functional spinal units, levels L2-L3, L3-L4, L4-L5, and L5-S1, were decorticated to the osteoligamentous structures. Posterior elements were removed to allow for MicroCT imaging of each specimen at a voxel size of 27 micron before and after instrumentation. A custom test fixture was used to apply 50N compressive force to stabilize the specimen and also record inline axial forces associated with the deployment of anchor plates during instrumentation procedures. A Chatillon DFS II force gauge was used to record axial forces during implantation of ENZA 1.0 and ENZA 2.0 interbody devices. Axial forces resulting from implant trialing, device insertion and anchor deployment were recorded. MicroCT scans were repeated to allow for quantification of damage to bony structures as a result of implantation procedures. <h3>RESULTS</h3> L2-L3 and L3-L4 force outputs are similar for both insertion, 218.82 N, 219.89 N, and deployment forces, 34.58 N, 44.88 N respectively. Insertion forces throughout all spinal levels were larger than both deployment and removal forces. Insertion forces were larger in the proximal levels, 218.82 N, 219.89 N, when compared to the distal levels, 178.96 N, 113.76 N. However, deployment force was larger in the distal levels, 99.03 N, 77.76 N, when compared to proximal 34.58 N, 44.88 N. <h3>CONCLUSIONS</h3> As evidence mounts for the cost-effectiveness of standalone cages with integrated supplemental fixation, it is imperative that design requirements of these devices continue to improve. Previous studies have shown that the vertebral endplate is susceptible to fracture under compressive loading, with the weakest area of the vertebrae being the center region. In 2001, Hasegawa et al showed a cylindrical-shaped implant caused endplate fracture between 510N and 1335N and that implant size is inversely related to the force required to cause fracture. Endplate fracture is difficult to detect with standard imaging modalities and leaves the patient vulnerable to implant subsidence and reduces segmental stability as a result of changes in load transfer. Furthermore, endplate failure may be a contributor to low back pain, further reducing the chance of a successful outcome. Our study showed interbody devices with integrated fixation plates could safely be inserted and deployed in the disc space without causing endplate fracture. The implant-endplate interface should be investigated in greater detail to allow for design of standalone interbody devices which do not cause unintended distraction or worse, damage to the vertebrae. <h3>FDA DEVICE/DRUG STATUS</h3> ENZA Lumbar Interbody Fusion Device (Approved for this indication).

P107. Maintenance of alignment following adult spinal deformity surgery: a comparative analysis of the impact of utilization of supplemental rods relative to interbody placement

BACKGROUND CONTEXT Correction and maintenance of lordosis can be considered one of the most important aspects of achieving ideal surgical outcomes in ASD. Lumbar interbody fusions have been shown to be a beneficial tool in restoring lordosis, while supplemental rod constructs have been shown to increase durability and strength of the construct. However, there is a paucity of literature on whether multiple lumbar interbody fusions or supplemental rod constructs achieve superior maintenance of lordosis and/or superior surgical outcomes. PURPOSE To investigate the outcomes and effect on maintenance of correction between multiple lumbar interbody fusions and supplemental rod constructs. STUDY DESIGN/SETTING Retrospective cohort study of a prospective adult thoracolumbar deformity database. PATIENT SAMPLE A total of 381 ASD Patients. OUTCOME MEASURES Radiographic alignment, complications. METHODS Operative ASD patients (scoliosis >20º, SVA>5cm, PT>25º, or TK>60º) with fusion UIV at or above L1 and fusion to pelvis with available baseline (BL) and 2-year (2Y) radiographic and HRQL data were included. Patients were divided into 2 groups, 1) those who had a supplemental rod construct (SUP) crossing at least 4 levels of the lumbar spine with no lumbar interbody fusion (LIBF), and 2) greater than or equal to 4 LIBF with no SUP. High loss of lumbar lordosis (HL) was defined as 1STD above the mean change in lordosis from post-op to 2Y. RESULTS Out of 381 ASD patients who met inclusion criteria, 53 were analyzed: 24 with LIBF, and 29 with SUPs. At BL patients with a SUP had a greater SVA (9.3cm vs 7cm), p.05). No differences in age, gender, BMI, CCI, frailty or BL HRQLs. ANCOVA adjusting for BL deformity, 3CO, and revision status found SUP patients had a lower operative time (341min vs 663min, p.05. LIBF patients had a comparable degree of LL correction (18 vs 22) and greater HL (19% vs 4%). LIBF patients had higher rates of implant failure (42% vs 14%), rod breakage (21% vs 4%), rod dislocation (13% vs 0%) and overall mechanical complications (71% vs 35%, all p<.05). Rates of PJF trended higher (25% vs 10%). At 2Y, SUP patients had comparable HRQLs and trended higher for 6W GAP Proportionality (35% vs 21%). CONCLUSIONS The use of supplemental rods relative to the performance of multiple lumbar interbodies appear to better maintain alignment and substantially lower rates of rod breakage, implant failure, and overall mechanical complications by 2 years and beyond. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs. Correction and maintenance of lordosis can be considered one of the most important aspects of achieving ideal surgical outcomes in ASD. Lumbar interbody fusions have been shown to be a beneficial tool in restoring lordosis, while supplemental rod constructs have been shown to increase durability and strength of the construct. However, there is a paucity of literature on whether multiple lumbar interbody fusions or supplemental rod constructs achieve superior maintenance of lordosis and/or superior surgical outcomes. To investigate the outcomes and effect on maintenance of correction between multiple lumbar interbody fusions and supplemental rod constructs. Retrospective cohort study of a prospective adult thoracolumbar deformity database. A total of 381 ASD Patients. Radiographic alignment, complications. Operative ASD patients (scoliosis >20º, SVA>5cm, PT>25º, or TK>60º) with fusion UIV at or above L1 and fusion to pelvis with available baseline (BL) and 2-year (2Y) radiographic and HRQL data were included. Patients were divided into 2 groups, 1) those who had a supplemental rod construct (SUP) crossing at least 4 levels of the lumbar spine with no lumbar interbody fusion (LIBF), and 2) greater than or equal to 4 LIBF with no SUP. High loss of lumbar lordosis (HL) was defined as 1STD above the mean change in lordosis from post-op to 2Y. Out of 381 ASD patients who met inclusion criteria, 53 were analyzed: 24 with LIBF, and 29 with SUPs. At BL patients with a SUP had a greater SVA (9.3cm vs 7cm), p.05). No differences in age, gender, BMI, CCI, frailty or BL HRQLs. ANCOVA adjusting for BL deformity, 3CO, and revision status found SUP patients had a lower operative time (341min vs 663min, p.05. LIBF patients had a comparable degree of LL correction (18 vs 22) and greater HL (19% vs 4%). LIBF patients had higher rates of implant failure (42% vs 14%), rod breakage (21% vs 4%), rod dislocation (13% vs 0%) and overall mechanical complications (71% vs 35%, all p<.05). Rates of PJF trended higher (25% vs 10%). At 2Y, SUP patients had comparable HRQLs and trended higher for 6W GAP Proportionality (35% vs 21%). The use of supplemental rods relative to the performance of multiple lumbar interbodies appear to better maintain alignment and substantially lower rates of rod breakage, implant failure, and overall mechanical complications by 2 years and beyond.

Transfacet Oblique Lateral Lumbar Interbody Fusion: Technical Description and Early Results.

IntroductionThe oblique lateral lumbar interbody fusion (OLLIF) is a relatively new method of lumbar interbody fusion (LIF) that utilizes a trans-Kambin approach to the disc space. The OLLIF can be performed from T12-S1 in the majority of cases but is occasionally obstructed at the L5-S1 level by osteophytes, an overgrown facet joint and/or prominent sacral ala. Transfacet OLLIF (TF-OLLIF) is a novel method for LIF in which the disc space is accessed by drilling through hypertrophic facets with an OLLIF approach. We provide a proof-of-concept report on the TF-OLLIF surgical technique and report the clinical and perioperative outcomes for the first 29 patients who underwent this procedure.MethodsThis is a retrospective single surgeon cohort study of 29 patients with lumbar spinal stenosis (LSS) who underwent TF-OLLIF procedures between 8/2018 and 1/2021. The primary outcome was a change in the Oswestry Disability Index (ODI) one year after surgery. Secondary outcomes were surgery time, blood loss, hospital stay, and complications. The TF-OLLIF was performed using the approach and instrumentation of OLLIF. When osseous hypertrophy is reached during the approach, an 8 mm drill is used to drill through the obstructing bone with continuous neuromonitoring. Discectomy and interbody placement are performed with subsequent posterior pedicle screw fixation.ResultsODI improved from 49% pre-op to 31% at one-year follow-up. Estimated blood loss ranged from 97.6±93.3 ml for one level TF-OLLIF to 146.2±60.3 ml for a 3+ level TF-OLLIF. Operative time ranged from 57.4±19.5 minutes for a one-level TF-OLLIF to 102.9±27.8 minutes for a 3+ level TF-OLLIF. The average length of hospital stay (LOS) was 0.4±0.8 days for one-level TF-OLLIF and 1.6±1.9 days for 3+ level TF-OLLIF. Complications included five cases of nerve root irritation immediately postoperatively, with three of these patients still reporting mild L5 distribution numbness at the last follow-up, which was not clinically limiting.ConclusionThe first 29 cases of TF-OLLIF demonstrated that it is a safe method of interbody fusion that yields good clinical results. This is an important development for practitioners of OLLIF as it enables interbody placement with OLLIF instruments and approach even for challenging L5-S1 levels without compromising surgical outcomes.

Safe dissection and complication avoidance for L1-2 interbody placement via a lateral access approach.

The lateral access approach for L1–2 interbody placement or other levels at or near the thoracolumbar junction may be difficult without proper knowledge and visualization of anatomy. Specifically, understanding where the fibers of the diaphragm travel and avoiding injury to the diaphragm are paramount.The video can be found here: https://stream.cadmore.media/r10.3171/2022.3.FOCVID2221

316 Optimizing Safety in Robotic Lumbar Instrumented Fusions: A Risk Factor Analysis of Robotic Failures

INTRODUCTION: There may be early complications with robot-guided lumbar fusions (RGLF). This study determines risk factors for robot-related complications and suggests optimal OR workflow. METHODS: Single-institution retrospective review of 525 RGLFs. Univariate analysis (independent samples t-tests, chi-squared analysis) assessed demographics, Hounsfield units (HU), procedural characteristics, and OR workflow as risk factors for robot registration failures and pedicle screw malpositioning. Multivariate logistic regression of significant factors was conducted. Subanalysis of Anterior Lumbar Interbody Fusion (ALIF) with RGLF was conducted. Receiver operating characteristic (ROC) curve determined thresholds for independent risk factors. RESULTS: All RGLF: Lower L1-HU and L5-S1 inclusion were significant risk factors for registration failure on univariate analysis. Placing pedicle screws directly after CT acquisition (PS after CT) and before interbody placement showed fewer registration failures. On multivariate analysis, L1-HU (Odds Ratio (OR): 1.012; p = 0.006), L5-S1 inclusion (OR: 2.795; p = 0.033) were independent risk factors. PS after CT improved registration (OR: 0.145; p = 0.004). Age and female gender were risk factors for pedicle screw malpositioning on univariate analysis. PS after CT showed fewer pedicle screw malpositions on univariate and multivariate (OR: 0.146; p = 0.006) analysis. ALIF with RGLF: PS after CT had fewer registration failures. Low L1-HU units was a risk for registration failure on univariate and multivariate (OR: 1.022; p = 0.001) analysis. ROC analysis of L1-HU showed a 145.85 cutoff. Age and hyperlordotic interbody use were risk factors for pedicle screw malposition on univariate analysis. CONCLUSION: Early robot-related complications may be avoided by recognizing risks. PS after CT, before interbody placement may avoid complications including pedicle screw malpositioning. Poor bone quality can lead to registration failures.

452 Lateral Interbody Fusion Using a 3D Navigation-guided, Prone, Single Position Approach: A Case Series

INTRODUCTION: Interbody fusion via the lateral approach provides certain biomechanical advantages over the posterior approach, including the larger allowable implant size and more anterior implant position. However, current methods for lateral interbody placement require either a two-staged procedure or a lateral single position with limited access to the posterior spine. We present our case series of the first 10 patients who underwent novel single position prone lateral approach, which provides simultaneous full access to the anterior and posterior lumbar spine. METHODS: We combined prospective collection of operative and surgical outcome data with retrospective analysis for patients with prone lateral lumbar interbody fusion (Pro-LLIF). Propensity score matching was used to identify 10 control patients who had undergone comparable levels of oblique lateral interbody fusion (OLIF) for comparison. RESULTS: Single position prone lateral approach allows both lateral lumbar interbody placement and direct posterior decompression and pedicle screws placement in one position. 3D navigation is utilized to plan lateral spine trajectory and interbody cage placement. Tubular retractors are used for quick and safe access to the retroperitoneal space. Under direct vision, direct psoas muscle dissection is performed and additional retractor pins are placed to minimize risks to the lumbar plexus. Our cohort comprised eight female and two male patients with average BMI of 28.5 and average age of 66.5 years. Average total operative time for Pro-LLIF was 4.5 hours compared to 4.33 hours for OLIF (p &gt; 0.5). Mean estimated blood loss was 240 mL and 262.5 mL for Pro-LLIF and OLIF, respectively (p &gt; 0.5). Pro-LLIF patients did not experience significantly different lengths of stay or discharge rates to rehabilitative facilities. CONCLUSION: Single position prone lateral approach provides safe and simultaneous access to lateral interbody cage placement and direct posterior neural decompression and segmental fixation. Efficiency will improve with increased experience with this promising technique.

39. Optimizing safety in robotic lumbar instrumented fusions: a risk factor analysis of robotic failures

39. Optimizing safety in robotic lumbar instrumented fusions: a risk factor analysis of robotic failures

Narrative review of intraoperative image guidance for transforaminal lumbar interbody fusion.

Recent advancements in imaging technology have changed the landscape of transforaminal lumbar interbody fusion (TLIF) with the objective of improving safety and efficacy for the patient and surgical team. Spine surgery, and specifically TLIFs, involve challenging anatomy and command precise surgical accuracy, creating an essential role for intraoperative imaging, navigation, and robotics. Traditionally, surgeons have relied upon fluoroscopy for pedicle screw and interbody placement. More recently, intraoperative 3-dimensional navigation (ION) has risen in popularity in TLIF surgery. This technology utilizes intra-operative advanced imaging, such as computed tomography (CT) and 3D-fluroscopy, to accurately track instruments and implants in relation to the patient’s anatomy. ION has demonstrated improved accuracy of pedicle screw placement, decreased operating room times, and lower radiation exposure to the surgeon and staff. However, conventional fluoroscopy, 3D fluoroscopy, intraoperative CT, image-guided navigation, and robot-assisted surgery all have a role in TLIF surgery. Numerous studies have been published regarding the benefits and pitfalls of these intraoperative tools in spine surgery, but there is a relative lack of research regarding some of the newer technologies surrounding TLIF. As future studies are published, and technology continues to evolve, surgeons must stay abreast of novel techniques to maximize patient safety and outcomes. Over the coming decade, we can expect intraoperative navigation and robotics to play a more significant role in spine surgery.

Prone Transpsoas Approach for Adjacent Segment Disease and Flatback Deformity: Technical Note and Case Report

The prone transpsoas approach is a relatively new technique to correct segmental kyphosis and global sagittal imbalance in a minimally invasive fashion. Here, we provide a detailed case report using the prone transpsoas approach to address adjacent segment disease and flatback deformity. This technique allows considerable restoration of segmental lordosis with lateral interbody placement and posterior decompression and fusion using a single position approach. Our experience with the surgical technique and the advantages and challenges unique to this approach are discussed.

Safety Profile, Surgical Technique, and Early Clinical Results for Simultaneous Lateral Lumbar Interbody Fusion and Anterior Lumbar Interbody Fusion in a Lateral Position.

Description of surgical technique and retrospective review. To describe a novel surgical technique for multilevel lumbar fusion and describe early clinical results. Patients with multilevel lumbar spinal stenosis and adult degenerative scoliosis often require multilevel interbody placement to achieve indirect decompression and lordosis. We describe a case series of patients treated with simultaneous lateral lumbar interbody fusion (LLIF) and anterior lumbar interbody fusion (ALIF) at L5-S1. We retrospectively reviewed a consecutive series of patients treated for multilevel lumbar spinal stenosis with simultaneous ALIF and LLIF with at least 3-month follow-up. All patients received supplemental percutaneous bilateral pedicle screw placement as well. We measured on preoperative radiographs their lumbar lordosis, pelvic incidence, and L5-S1 lordosis. Intraoperative factors such as operative time, estimated blood loss, fluids provided, number of levels fused, and whether a trainee was present during the procedure were all recorded. There were 15 patients included within our case series (69.5, 4 F). There were no reported intraoperative vascular or neurological complications in 15 cases. The operative time for the cases ranged from 2.7 to 8.4 hours (average=5.2±1.9 h). The average lordosis gained at L5-S1 was 8.6±3.0 degrees and the average lumbar lordosis gained was 14.7±6.4 degrees. The average PI-LL mismatch went from 22.4±13.3 degrees preoperative to 7.8±10.2 degrees postoperative. One patient had a postoperative complication of a sacral fracture requiring placement of a pelvic screw for a L2-pelvis fusion. There were 8 patients with 4+ levels of fusion. For this cohort of patients, the average lumbar lordosis gained was 16.0±7.5 degrees and the average PI-LL mismatch went from 24.7±16.3 degrees preoperative to 8.8±12.9 degrees postoperative. For the patients with 4+ levels of fusion, the average operative time was 5.9±1.8 hours. We have described our early positive results with simultaneous LLIF/ALIF surgery for treatment of lumbar degenerative conditions.

Awake, Endoscopic Revision Surgery for Lumbar Pseudarthrosis After Transforaminal Lumbar Interbody Fusion: Technical Notes

We sought to evaluate the feasibility for awake, endoscopic treatment of lumbar pseudarthrosis after a transforaminal lumbar interbody fusion (TLIF). A 71-year-old male with severe cardiac disease, determined to be high risk for general anesthesia, presented with mechanical back pain and a L3-4 pseudarthrosis and L3 pedicle screw loosening after a L3-5 TLIF. An awake, transforaminal endoscopic redo diskectomy and TLIF procedure were performed by removing residual disk material adjacent to the previous "PEEK" (polyetheretherketone) interbody spacer and placing allograft, bone morphogenetic protein, and an expandable titanium interbody device adjacent to the PEEK cage. At 1-year follow-up, preoperative visual analog scale for back pain and Oswestry disability index improved from 7 and 38% to 1 and 2%. The 1-year follow-up radiograph showed stable interbody placement and no further screw loosening. A minimally invasive, awake procedure is presented for the treatment of pseudarthrosis after TLIF.

Endplate Deformation Due to Open and Strutted Intervertebral Devices.

There is an absence of work on vertebral endplate response to peripheral loading following disc removal and interbody placement. Endplate deflection into the interbody space may impart beneficial strain on the developing fusion mass, influencing bone formation and remodeling. The aim of this study was to verify endplate deformation due to peripheral loading using a custom transducer and to investigate whether endplate motion is inhibited by implant design. A total of 14 porcine (L4, L5) vertebrae were assigned to open or strutted implant designs. A custom transducer was placed on the endplate while 500 N was applied to the implant at 1 Hz for 500 cycles. Endplate motion was acquired for each time point and averaged among specimens of the same design. The rates and magnitudes of endplate deformation were compared between implant designs using unpaired t tests. Peripheral loading of both implant designs resulted in endplate deflection into the interbody space. The open implant design demonstrated an increased rate and magnitude of endplate deformation when compared with strutted implants. Interbody cage design directly influences the dynamic motion of the vertebral endplate during cyclic loading. A larger, faster deflection of the endplate could increase the strain rate, duration, and magnitude on the developing interbody fusion mass. These parameters of dynamic strain have been correlated with increased bone formation and remodeling. Unimpeded endplate deformation in an open cage design could impart a strain pattern on the developing fusion mass that increases bone formation and remodeling, ultimately leading to a faster and stronger fusion.

Initial Single-Institution Experience With a Novel Robotic-Navigation System for Thoracolumbar Pedicle Screw and Pelvic Screw Placement With 643 Screws.

Robotic-guided navigation systems for pedicle screw placement has gained recent interest to ensure accuracy and safety and diminish radiation exposure. There have been no published studies using a new combined robotics and navigation system (Globus ExcelsiusGPS system). The purpose of this study was to demonstrate safety with this system. This is a case series of consecutive patients at a single institution from February 1, 2018, to August 31, 2018. All patients who had planned placement of thoracic and lumbar pedicle screws using the combined robotics-navigation system were included. Chart review was performed for operative details. A subgroup analysis was performed on patients with postoperative computed tomography (CT) scans to assess screw placement accuracy using the Gertzbein and Robbins system. Acceptable pedicle screw position was defined as grade A or B. One hundred six patients were included, with 636 pedicle screws, 6 iliac screws, and 1 S2AI screw. Five cases were aborted for technical issues. In the remaining 101 patients, 88 patients had screws placed using preoperative CT planning and 13 patients using intraoperative fluoroscopy planning. All screws except for 5 pedicle screws in 2 patients were placed successfully using the robot (99%). These 5 pedicle screws were placed by converting to a fluoro-guided technique without robotic assistance. Eighty-six patients had screws placed using a percutaneous technique, and 15 patients had screws placed using an open technique. Ninety-eight patients underwent interbody placement: 28 anterior lumbar interbody fusions (ALIFs), 12 lateral lumbar interbody fusions (LLIFs), and 58 transforaminal lumbar interbody fusions (TLIFs). All ALIFs and LLIFs were performed prior to placement of the screws. Four LIF patients had screws placed in the lateral position. No patients had screw-related complications intraoperatively or postoperatively, and no patients returned to the operating room for screw revision. Thirteen patients underwent postoperative CT for various reasons. Of the 66 pedicle screws that were examined with postoperative CT, all screws (100%) had acceptable position. This study demonstrates that the combined robotics and navigation system is a novel technology that can be utilized to place pedicle screws and pelvic screws safely and has the potential to reduce screw-related complications. 4 (case series).

Analysis of single-position for revision surgery using lateral interbody fusion and pedicle screw fixation: feasibility and perioperative results.

To analyze perioperative and radiographic outcomes following revision surgery using lateral lumbar interbody fusion (LLIF) performed entirely in the lateral position. Traditionally, patients undergoing interbody fusion in the lateral decubitus position are placed prone for pedicle screw fixation. However prone positioning carries known risks and may increase surgical time due to the need to re-drape and reposition. Little is published regarding revision surgery in a single position. Sixteen patients over the age of 18 with degenerative lumbar pathology who underwent a revision of previous lumbar fusion using interbody fusion via lateral access and revision of posterior instrumentation from a single surgeon met inclusion criteria. Patients who underwent combined procedures requiring repositioning or had inadequate preoperative imaging were excluded. Patients remained in the lateral decubitus position for the entirety of the procedure including interbody placement, revision of prior instrumentation, and pedicle screw fixation. Demographics, surgical details, and perioperative outcomes were reported. The mean operative time was 211 minutes for all cases, 161 minutes for single-level procedures and 296 minutes for two-level procedures. Mean estimated blood loss was 206 cc. The mean patient age was 66, 70% of which were male. The mean body mass index (BMI) was 27.4 and Charleson Comorbidity Index (CCI) was 3. All cases were performed on the lumbar spine (T12/L1-L4/L5), with the majority of procedures performed at the L2/3 level (44%). The mean pelvic incidence (PI) was 60 degrees (range, 41-71 degrees) with mean preoperative PI/lumbar lordosis (LL) mismatch of 23.9 degrees. Mean postoperative PI/LL mismatch was 12 degrees. Revision surgery in the lateral position is feasible with complication rates comparable to published literature. The need to reposition is eliminated and single position surgery reduces operative time.