Anterior Lumbar Interbody Fusion Research Articles

Efficacy of Stand-Alone Anterior Lumbar Interbody Fusion With PEEK Cages, BMP-2, and Allografts for Treating Discogenic Low Back Pain: Assessing Clinical and Radiographic Outcomes.

Chronic low back pain secondary to degenerative disc disease is a significant public health issue worldwide, contributing to substantial health care burdens and patient disability. Anterior lumbar interbody fusion (ALIF) has emerged as a promising surgical solution, offering benefits such as disc height restoration, reduced neural compression, and improved spinal alignment. This study evaluates the efficacy of stand-alone ALIF using polyetheretherketone (PEEK) cages, structural femoral head allografts, and recombinant human bone morphogenetic protein-2 (rhBMP-2) in treating discogenic low back pain caused by degenerative disc disease. This prospective case series study included 1335 patients who underwent stand-alone ALIF by a single surgeon. The surgical construct involved PEEK cages with structural femoral allograft dowels and rhBMP-2, supplemented by anterior fixation. Patient-reported outcome measures, including the visual analog scale for back and leg pain, the Oswestry Disability Index, the Roland-Morris Disability Questionnaire, and patient satisfaction, were monitored over 12 months. The overall fusion rate was 99.6%, with pseudoarthrosis occurring in 0.2% of patients. Lower fusion rates were observed in patients older than 65 years and those using the Brantigan cage. Significant improvements were seen in visual analog scale for back and leg pain, Oswestry Disability Index, and Roland-Morris Disability Questionnaire scores from baseline, with most scores exceeding the substantial clinical benefit thresholds. More than 85% of patients reported "Excellent" or "Good" outcomes. Stand-alone ALIF, augmented with rhBMP-2 and structural femoral head allografts, can enhance mechanical stability, fusion rates, and radiographic assessment. This integrated approach achieves successful spinal fusion and positive clinical outcomes for patients with refractory discogenic low back pain. Stand-alone ALIF with PEEK cages, structural femoral head allografts, and rhBMP-2 demonstrates high fusion rates and significant clinical improvements in patients with discogenic low back pain. This approach enhances spinal stability and promotes biological healing, making it a reliable and effective surgical option.

A magnetic resonance imaging-based morphometric analysis of bilateral L1-L5 oblique lumbar interbody fusion corridor: feasibility of safe surgical approach and influencing factors.

Retrospective cross-sectional study. To investigate the size and local anatomy of the right and the left-sided oblique corridors between L1-L5 levels and identify the potential impact of increasing age and sex on corridor size. The oblique lumbar interbody fusion (OLIF) was introduced by Silvestre and his colleagues as a solution to the approach-related complications associated with anterior lumbar interbody fusion and lateral lumbar interbody fusion. Limited data were available describing the local anatomy and morphology of this approach. Imaging data of 300 patients (150 males and 150 females) who underwent 1.5T magnetic resonance imaging (MRI) scans of the lumbar spine at Indian Spinal Injuries Centre, New Delhi, India between January 2023 and January 2024 were retrospectively reviewed. The cohort was stratified into six age groups (21-30, 31-40, 41-50, 51-60, 61-70, and >70 years) with 25 patients in each age group for both sexes. T2 weighted axial MRI images were analyzed from the L1-L5 level at the mid-disc level to calculate the corridor size. The local anatomical differences were recorded. At L1-L2, L2-L3, L3-L4, and L4-L5 levels, the mean corridor sizes in males were 17.48, 15.50, 13.41, and 9.32 mm on the left side, and 11.48, 7.12, 4.34, and 1.64 mm on the right side, respectively. The corresponding mean corridor sizes in females were 10.34, 12.94, 12.64, and 7.22 mm on the left side and 2.66, 3.52, 3.69, and 1.64 mm on the right side, respectively. For both sides, the corridor size was significantly affected by sex, increased with age, and decreased at the lower lumbar disc levels. A left-sided OLIF approach is more feasible for both sexes. The right-sided approach is less likely to be performed effectively.

Impact of Age on the Occurrence of Vascular Complications in Patients Undergoing Anterior Lumbar Approach Surgery.

Retrospective cohort study. To investigate the impact of age on the incidence of vascular complications in patients undergoing anterior lumbar approach surgery. Anterior approach lumbar spinal surgery may facilitate the use of intervertebral devices with larger endplate coverage and increased lordosis. Despite the advantages of this approach, risks related to vascular injury in older patients have been described in the literature. In total, 751 consecutive patients with degenerative spinal pathology who underwent stand-alone anterior lumbar interbody fusion (ALIF), ALIF combined with posterior fusion and/or instrumentation (360), total disc replacement, or hybrid procedures (ALIF and total disc replacement) were included. Data collected included general patient descriptive data, surgery details, intraoperative vascular injury, and postoperative vascular complications (deep vein thrombosis and/or pulmonary embolism). Rates of vascular complications were compared across age groups. In addition, the mean age of patients was compared between those with versus without vascular complications. Overall mean age was 50.4 years (range: 20-83 yr). The mean estimated blood loss was 91.3mL (range: 10-2800mL). A total of 15 patients, 2.0%, had vascular complications. There were 10 cases (1.3%) of intraoperative injury to iliac arteries or iliolumbar veins (mean blood loss was 721mL, and all were repaired intraoperatively). Postoperatively, 6 patients (0.8%) developed deep vein thrombosis and/or pulmonary embolism (one patient had both). With respect to age, there were no significant differences in rates of intraoperative, postoperative, or combined vascular complication rates across the age group ( P > 0.38). In addition, there were no statistically significant differences in the mean ages of patients with versus those without vascular complications ( P > 0.17). Overall incidence of vascular complications was 2.0%. No relationship between vascular complications and age was demonstrated. These data suggest that increased age may not necessarily be an absolute contraindication for anterior lumbar approach surgery. Level III.

Trans-Pars Interarticularis Approach for Lumbar Interbody Fusion: An Efficient, Straightforward, and Minimally Invasive Surgery for Lumbar Spondylolisthesis and Stenosis.

Lumbar interbody fusion is a commonly applied surgical treatment for spondylolisthesis. For this procedure, various minimally invasive (MIS) approaches have been developed, including posterior lumbar interbody fusion, transforaminal lumbar interbody fusion (TLIF), oblique lumbar interbody fusion, and anterior lumbar interbody fusion. In this study, we characterized the features of an MIS trans-pars interarticularis lumbar interbody fusion (TPLIF) and compared its surgical outcomes with those of MIS-TLIF. This study included 89 and 44 patients who had undergone MIS-TPLIF and MIS-TLIF, respectively, between September 2016 and December 2022. The following clinical outcomes were analyzed: operative time, blood loss, and hospitalization duration. The average operative time, blood loss, and hospitalization duration for the MIS-TPLIF and MIS-TLIF groups were, respectively, 98.28 and 191.15 minutes, 41.97 and 101.85 mL, and 5.8 and 6.9 days. The MIS-TPLIF approach for lumbar spondylolisthesis or other degenerative diseases involves the use of the commonly available and cost-effective instrument Taylor retractor, thus enabling posterior lumbar interbody fusion to be performed with minimal invasion. This approach also confers the benefits of a short learning curve and an intuitive approach. Our results suggest that although MIS-TPLIF is noninferior to MIS-TLIF, it is easier to learn and perform than MIS-TLIF.

Comparison of patient outcomes of anterior and posterior lumbar interbody fusions: A retrospective national database analysis

BackgroundLumbar interbody fusions are used to treat degenerative lumbar disease unresponsive to conservative treatment. This procedure may be divided into anterior lumbar interbody fusion (ALIF), and posterior lumbar interbody fusion (PLIF/TLIF). Despite their widespread use, comparative research on their outcomes remains limited. MethodsThe PearlDiver Database was utilized to identify patients undergoing single and multi-level ALIF and PLIF/TLIF between 2010 and 2022. We examined demographic data, comorbidities, and reoperation rates at 90 days, 1 year, and 2 years. Complications were assessed using multivariable regression to adjust for confounders. ResultsThe study included multi-level anterior interbody fusions (N = 569, mean age 59.8, 59 % female), multi-level posterior interbody fusions (N = 43,651, mean age 57.9, 60 % female), single-level anterior interbody fusions (N = 3,547, mean age 55.3, 61 % female) and single-level posterior interbody fusions (N = 25,792, mean age 56.9, 62 % female). Multi-level posterior interbody fusion patients had a lower prevalence of HTN (OR .77, P < .05), ischemic heart disease (OR .73, P < .05), CDK (OR .77, P < .05), postoperatively more DVTs (OR 1.44, P < .05), a lower incidence of respiratory failure (OR .57, P < .05), and a higher 90-day, 1-year, and 2-year all-cause reoperation rate (7.3 %) compared to multi-level anterior interbody fusion patients (3.7 %). Single-level posterior interbody fusion patients had more HTN (OR 1.1, P < .05), less ischemic heart disease (OR .89, P < .05), obesity (OR .92, P < .05), and postoperatively a higher incidence of DVT (OR 1.34, P < .05) but lower 90-day, 1-year, and 2-year all-cause reoperation rates. ConclusionsThis study confirms that posterior interbody fusions are more common than anterior procedures, though the latter is increasing. Reoperation rates are higher for multi-level posterior and single-level anterior fusions. Both anterior and posterior approaches show similar complication profiles, though specific risks, such as postoperative DVT, vary. These findings emphasize the need for ongoing research and consideration of individual patient factors when choosing an interbody fusion technique.

More is less: image enhancement technology reduces radiation exposure during anterior lumbar interbody fusion

BACKGROUND CONTEXTFluoroscopy and radiation exposure occur during anterior lumbar interbody fusion (ALIF). Image enhancement technology is available that can potentially reduce radiation exposure. PURPOSEThe purpose of this study is to evaluate radiation exposure and fluoroscopy times comparing standard fluoroscopy (FL) with a low dose image enhancement platform (LD). STUDY DESIGNRetrospective review of prospectively maintained database. PATIENT SAMPLEConsecutive patients undergoing ALIF with either standard fluoroscopy or low dose image enhancement technology. OUTCOME MEASURESRadiation dispersion and fluoroscopy times in ALIF patients with standard fluoroscopy and low dose image enhancement technology. METHODSA retrospective review of a prospective database on consecutive patients who have undergone ALIF, stratified into 2 groups: subjects with standard fluoroscopy (FL), and low dose fluoroscopy with image enhancement technology (LD). RESULTSA total of 487 ALIF patients were included (FL: 372 vs. LD: 115). LD patients were significantly older (66 vs. 60 years), with more deformity cases (28% vs. 12%), and less degenerative cases (71% vs. 87%), all p<.05; no differences in sex, BMI, or the number of levels operated on between groups. Fluoroscopy time (sec) was significantly higher in LD (51.4 vs. 45.5), with a statistically significant reduction in radiation (mGy) compared to FL (23.3 vs. 48.2), both p<.05. Furthermore, the results showed that radiation dispersion is increasingly reduced as fluoroscopy time increases in LD compared to FL (12%, 56%, and 65% reduction in radiation dispersion for fluoroscopy time <30 sec, between 30 to 60 sec, and >60 sec, respectively). CONCLUSIONSThe use of low dose fluoroscopy with image enhancement technology significantly reduces the cumulative dose of radiation during ALIF compared to standard dose fluoroscopy. Also, radiation dispersion increasingly decreases as fluoroscopy time increases using low dose image enhancement technology. Low dose image enhancement technology improves the safety profile of ALIF for patients and operating room staff.

Off-Label Bone Morphogenetic Protein 2 Use Results in Successful Posterolateral Lumbar Fusion in a Veteran Population.

Patients within the US Veterans Health Administration (VA) system have higher rates of comorbidities and chronic pain, increasing risks of complications/poor outcomes following spine surgery. Although the use of bone morphogenetic protein 2 (BMP-2) is established for anterior lumbar interbody fusion, its indications for off-label use in posterolateral fusion are unclear. The objective of this study was to evaluate safety and utility of BMP-2 in posterolateral fusion through a 15-year experience at the VA. Patients underwent posterolateral lumbosacral fusions with BMP-2 by a single VA surgeon from January 1, 2005, to January 1, 2020. The primary outcome was fusion assessed through postoperative radiographs. Secondary outcomes included adjacent segment disease (ASD) and postoperative pain clinic utilization. Sixty-eight patients underwent lumbosacral posterolateral fusion with BMP-2; 77.9% were discharged home and had no postoperative complications. All patients achieved bony fusion at a mean of 113.3 ± 59.9 days postoperatively. Five patients were diagnosed with cancer postoperatively, and eight patients required revision for ASD. No notable predictors of ASD exist. Preoperative opioid use predicted postoperative pain clinic utilization. Posterolateral lumbar fusion with BMP-2 in veterans yields high fusion rates and favorable complication profiles and should be considered in multimorbid hosts. Retrospective review of prospectively collected data.

Bone graft substitutes used in anterior lumbar interbody fusion: a contemporary systematic review of fusion rates and complications.

Anterior lumbar interbody fusion (ALIF) uses a broad-footprint interbody cage designed to maximize fusion rates for treating degenerative disc disease. Bone graft substitutes are being increasingly utilized during ALIF to replace or supplement autologous iliac crest bone grafts. This approach aims to optimize fusion efficacy while minimizing associated postoperative complications. The objective of this systematic review was to examine recent studies on fusion rates and postoperative complications associated with bone graft substitutes used in ALIF. We conducted a systematic review of the Cumulative Index to Nursing and Allied Health Literature (CINAHL), Embase, MEDLINE, and PubMed databases, to critically examine a decade of research (January 1, 2012, to July 6, 2023) on the effectiveness and safety of various bone graft substitutes in ALIF. This timeframe was chosen to build on a previous systematic review published in 2013. The PRISMA guidelines were used. In total, 27 articles met our stringent inclusion and exclusion criteria. A substantial portion of these studies (67%) focused on recombinant human bone morphogenetic protein-2 (rhBMP-2) and highlighted its efficacy for achieving high fusion rates. However, the literature presents a dichotomy regarding the association of rhBMP-2 with increased postoperative complications. Notably, the methodologies for evaluating spinal fusion varied across studies. Only one-third of studies employed computed tomography to assess interbody fusion at 12 months postoperatively, highlighting the urgent need to establish uniform fusion criteria to facilitate more accurate comparative analyses. Moreover, there was considerable variability in the criteria used for diagnosing and detecting postoperative complications, significantly influencing the reported incidence rates. This review underscores the need for continued research into bone graft substitutes, particularly focusing on assessment of long-term complications. Future research endeavors should concentrate on developing comprehensive clinical guidelines to aid in the selection of the most suitable bone graft substitutes for use in ALIF, thereby enhancing patient outcomes and surgical efficacy.

Anterior Lumbar Interbody Fusion as a Supplement to Posterior Instrumentation in Adult Spinal Deformity Patients: A Pilot Randomized Study With a Median of Eight Years of Follow-Up.

Aim We aim to assess the long-term revision rates in patients with adult spinal deformity (ASD) undergoing posterior instrumentation with or without supplemental anterior lumbar interbody fusion (ALIF) with a median of eight years of follow-up. Materials and methods Based on a previous pilot randomized controlled trial (RCT) from 2012, all previous participants were invited to a clinical and radiographicfollow-up. Full medical records from the total cohort were reviewed from the time of operation to the follow-up, and information on revision surgery due to mechanical failure was obtained and compared between the groups. Results Of the original 17 patients included in the RCT, 15 were available for follow-up and 10 attended the clinical and radiographic examination. A retrospective review was performed of the entire original cohort. The median age at follow-up was 67 (61-71) years, and the median follow-up time was 7.7 (5.1-8.8) years. Revision rates amongALIF patients were three out of seven (43%) and eight out of 10 (80%) amongnon-ALIF patients with pseudoarthrosis and rod breakage being the main cause. Time to failure was longer in ALIF patients with a median of 47 (28-53) months compared with non-ALIF patients with a median of 26 (9-31) months. Conclusion This study revealed a lower rate of revision surgery and a longer time to failure in patients undergoing ASD surgery with supplemental ALIF compared with posterior instrumentation alone. Further studies with a larger sample size are needed to make conclusions on the effect of a supplemental ALIF to posterior instrumentation on lowering the risk of mechanical failure in patients with adult spinal deformity.

Return to Work Following Anterior Lumbar Interbody Fusion with Percutaneous Posterior Pedicle Fixation: A Retrospective Analysis from Two Academic Centers in Germany.

Objective: Return to work after spinal surgery is a crucial factor in the recovery process. It can contribute not only to physical rehabilitation but also to psychological well-being. This study aims to evaluate the rate of return to work following elective lumbar spine surgery and identify predictors that predict failure of return to work. Methods: Adult patients who underwent anterior lumbar interbody fusion at two medical centers were retrospectively identified. A standardized telephone interview was conducted for the final analysis to assess the clinical outcomes of these patients. Results: Out of a total of 159 patients, 104 were of working age at the time of the elective surgery. Data were missing for 35 patients, who were thus excluded from the analysis. All patients had a minimum follow-up period of one year. After surgery, 75% of the patients returned to work within a median time of 3 months. Quality of life, back pain, leg pain, and ODI scores, as well as self-reported satisfaction, were significantly better in patients who returned to work (p < 0.05). Tobacco use and previous musculoskeletal surgery were significant predictive factors of failure to return to work. None of the patients who were unemployed prior to surgery returned to work. Conclusions: Our study reveals that 75% of patients returned to work within three months after surgery. The most significant predictor of failure to return to work is being unemployed before surgery. Additionally, preoperative education about postoperative behavior and physical activity could potentially increase the rate.

Comparative Biomechanical Analysis of Anterior Lumbar Interbody Fusion and Bilateral Expandable Transforaminal Lumbar Interbody Fusion Cages: A Finite Element Analysis Study.

Expandable transforaminal lumbar interbody fusion (TLIF) cages could offer an alternative to anterior lumbar interbody fusion (ALIF). Bilateral cage insertion enhances endplate coverage, potentially improving stability and fusion rates and maximizing segmental lordosis. This study aims to compare the biomechanical properties of bilateral expandable TLIF cages to ALIF cages using finite element modeling. We used a validated 3-dimensional finite element model of the lumbar spine. ALIF and TLIF cages were created based on available product data. Our focus was on analyzing spinal motion in the sagittal plane, evaluating forces transmitted through the vertebrae, and comparing an ALIF model with various TLIF cage models. The largest TLIF cage model exhibited a 407.9% increase in flexion motion and a 42.1% decrease in extension motion compared with the ALIF cage. The second largest TLIF cages resulted in more flexion motion and less extension motion compared with ALIF, while smaller cages were inferior to ALIF. ALIF cages were associated with increased adjacent segment motion compared with TLIF cages, primarily in extension. Endplate stress analysis revealed higher stress in the ALIF cage model with a more uniform stress distribution. ALIF cages excel in stabilizing L5 to S1 during flexion, while largest TLIF cages offer superior stability in extension. Large bilateral TLIF cages may provide biomechanical stability comparable to ALIF, especially in extension and could potentially reduce the risk of adjacent segment disease with lower adjacent segment motion.

Technique, Safety, and Accuracy Assessment of Percutaneous Pedicle Screw Placement Utilizing Computer-Assisted Navigation in Lateral Decubitus Single-Position Surgery.

Percutaneous pedicle screw (PPS) placement has become a pivotal technique in spinal surgery, increasing surgical efficiency and limiting the invasiveness of surgical procedures. The aim of this study was to analyze the accuracy of computer-assisted PPS placement with a standardized technique in the lateral decubitus position. A retrospective review of prospectively collected data was performed on 44 consecutive patients treated between 2021 and 2023 with lateral decubitus single-position surgery. PPS placement was assessed by computed tomography scans, and breaches were graded based on the magnitude and direction of the breach. Facet joint violations were assessed. Variables collected included patient demographics, indication, intraoperative complications, operative time, fluoroscopy time, estimated blood loss, and length of stay. Forty-four patients, with 220 PPSs were identified. About 79.5% of all patients underwent anterior lumbar interbody fusion only, 13.6% underwent lateral lumbar interbody fusion only, and 6.8% received a combination of both anterior lumbar interbody fusion and lateral lumbar interbody fusion. Eleven screw breaches (5%) were identified: 10 were Grade II breaches (<2 mm), and 1 was a Grade IV breach (>4 mm). All breaches were lateral. About 63.6% involved down-side screws indicating a trend toward the laterality of breaches for down-side pedicles. When analyzing breaches by level, 1.2% of screws at L5, 13% at L4, and 11.1% at L3 demonstrated Grade II breaches. No facet joint violations were noted. PPS placement utilizing computer-assisted navigation in lateral decubitus single-position surgery is both safe and accurate. An overall breach rate of 5% was found; considering a safe zone of 2 mm, only 1 screw (0.5%) demonstrated a relevant breach. PPS placement is both safe and accurate. Breaches are rare, and when breaches do occur, they are lateral.

Machine Learning for Individualized Risk Estimation in Anterior Lumbar Interbody Fusion

BACKGROUND AND OBJECTIVES: Although the anterior approach to the spine for anterior lumbar interbody fusion (ALIF) has been shown to be an effective procedure, there are different surgical risks compared with conventional posterior fusion. ALIF patients could potentially receive more personalized care plans that minimize the risk of negative outcomes by forecasting short-term postoperative results before the surgical procedure. The objective of this research was to evaluate the performance of machine learning (ML) algorithms in predicting short-term unfavorable postoperative outcomes after ALIF and to develop an easy-to-use and readily available instrument for this purpose. METHODS: Using the American College of Surgeons National Surgical Quality Improvement Program database, we identified ALIF patients and used 6 ML algorithms to build models predicting postoperative outcomes. These models were then incorporated into an open-access web application. RESULTS: The analysis included 8304 ALIF patients. The LightGBM models achieved area under the receiver operating characteristic scores of 0.735 for prolonged length of stay and 0.814 for nonhome discharges. The random forest models achieved area under the receiver operating characteristics of 0.707 for 30-day readmissions and 0.701 for major complications. These top-performing models were integrated into a web application for individualized patient predictions. CONCLUSION: ML techniques show promise in predicting postoperative outcomes for ALIF surgeries. As data in spinal surgery expand, these predictive models could significantly improve risk assessment and prognosis. We present an accessible predictive tool for ALIF surgeries to achieve the goals mentioned above.

Predictability in Achieving Target Intervertebral Lordosis Using Personalized Interbody Implants.

Lumbar lordosis distribution has become a pivotal factor in re-establishing the foundational alignment of the lumbar spine. This can directly influence overall sagittal alignment, leading to improved long-term outcomes for patients. Despite the wide availability of hyperlordotic stock cages intended to achieve optimal postoperative alignment, there is a lack of correlation between the lordotic shape of a cage and the resultant intervertebral alignment. Recently, personalized spine surgery has witnessed significant advancements, including 3D-printed personalized interbody implants, which are customized to the surgeon's treatment and alignment goals. This study evaluates the reliability of 3D-printed patient-specific interbody implants to achieve the planned postoperative intervertebral alignment. This is a retrospective study of 217 patients with spinal deformity or degenerative conditions. Patients were included if they received 3D-printed personalized interbody implants. The desired intervertebral lordosis (IVL) angle was prescribed into the device design for each personalized interbody (IVL goal). Standing postoperative radiographs were measured, and the IVL offset was calculated as IVL achieved minus IVL goal. In this patient population, 365 personalized interbodies were implanted, including 145 anterior lumbar interbody fusions (ALIFs), 99 lateral lumbar interbody fusions (LLIFs), and 121 transforaminal lumbar interbody fusions. Among the 365 treated levels, IVL offset was 1.1° ± 4.4° (mean ± SD). IVL was achieved within 5° of the plan in 299 levels (81.9%). IVL offset depended on the approach of the lumbar interbody fusion and was achieved within 5° for 85.9% of LLIF, 82.6% of transforaminal lumbar interbody fusions and 78.6% of ALIFs. Ten levels (2.7%) missed the planned IVL by >10°. ALIF and LLIF levels in which the plan was missed by more than 5° tended to be overcorrected. This study supports the use of 3D-printed personalized interbody implants to achieve planned sagittal intervertebral alignment. Personalized interbody implants can consistently achieve IVL goals and potentially impact foundational lumbar alignment.

One-Level versus Two-Level Anterior Lumbar Interbody Fusion (ALIF) from L4-S1: Comparison of Complications, Alignment, and Patient Outcomes.

Retrospective cohort study. Compare outcomes in patients undergoing one-level or two-level anterior lumbar interbody fusion (ALIF) at L4-S1. Although ALIF may deliver restoration of lumbar lordosis and improvement in clinical outcomes, it also carries risk of complications including major vascular injury. Whether one-level and two-level ALIF offers similar outcomes is not known. Adults who underwent one-level L4-L5 or L5-S1 ALIF and two-level L4-S1 ALIF at a single academic institution were identified. Patient demographics, procedural characteristics, improvement in spinopelvic alignment, and one-year postoperative patient-reported outcome measures (PROMs) and complications were compared. Multivariate regression analyses, accounting for age, gender, and Charlson Comorbidity Index (CCI), were also performed. In total, 158 ALIF patients (111 one-level and 47 two-level) were included, with mean age of 51.4 years, 57.0% female, mean CCI of 1.2, and mean follow-up of 27.0 months. Surgical time (147.3min vs. 124.6min, P=0.002) and hospital length of stay (3.5d vs. 2.9d, P=0.036) were higher for two-level ALIF. One-year postoperatively, two-level ALIF patients had more caudal apex of lordosis (P=0.016) and 4.1mm (P=0.002) and 2.0mm (P=0.019) higher L4-L5 anterior and posterior disc heights, respectively. PROMs were not statistically different across groups (P>0.05). Finally, two-level ALIF patients were 10.9 times more likely to have in-hospital complications (P=0.040), such as intraoperative vascular injury (11.1% vs. 1.5%, P=0.040) or postoperative ileus (7.4% vs. 0.0%, P=0.027), than one-level ALIF patients. In this investigation with greater than one-year follow-up, two-level ALIF in the L4-S1 spine had higher procedural time, length of stay, and approach-related complications than one-level ALIF. Although there were minor improvements in alignment with two-level ALIF, PROMs were comparable with improvements from baseline to last follow-up. These findings may help surgeons carefully weigh the risks and benefits of one- versus two-level ALIF when determining surgical plans for patients. IV.

Tomographic Assessment of Fusion Rate, Implant-Endplate Contact Area, Subsidence, and Alignment With Lumbar Personalized Interbody Implants at 1-Year Follow-Up.

Incongruity between irregularly shaped vertebral endplates and the uniform surfaces of stock interbody fusion cages has been identified as contributing to cage subsidence, pseudarthrosis, and unpredictable alignment. Advances in manufacturing techniques have driven the development of personalized interbody cages (PICs) that can match individual endplate morphology and provide the exact shape and size needed to fill the disc space and achieve the planned correction. This study used computed tomography (CT) imaging to evaluate the implant-endplate contact area, fusion, subsidence, and achievement of planned alignment correction in patients receiving PIC devices. This retrospective study included patients treated for adult spinal deformity at a single site and implanted with PIC devices at L4 to L5 or L5 to S1 for segmental stabilization and alignment correction, who received 1-year postoperative CT images as part of their standard of care. An evaluation using 3-dimensional thin-section scans was conducted. Implant-endplate contact and signs of fusion were assessed in each CT slice across both endplates. The degree of subsidence as well as measures of segmental and global lumbar alignment were also assessed. Fifteen patients were included in the study, with a mean age of 68.2 years. Follow-up ranged between 9 and 14 months. Twenty-six total lumbar levels were implanted; 20 with PIC devices via the anterior lumbar interbody fusion approach, 2 with stock cages via the anterior lumbar interbody fusion approach, and 4 with PIC devices via the transforaminal lumbar interbody fusion approach. CT analysis of PIC-implanted levels found an overall implant-endplate contact area ratio of 93.9%, a subsidence rate of 4.5%, a fusion rate of 100%, and satisfactory segmental and global lumbar correction compared with the preoperative plan. PIC implants can provide nearly complete contact with endplate surfaces regardless of the individual endplate morphology. Subsidence, fusion, and alignment assessments in this tomographic study illustrated results consistent with the benefits of a personalized interbody implant.

P275. Outcomes comparison between novel hydroxyapatite enhanced PEEK and titanium implants after anterior lumbar interbody fusion

P275. Outcomes comparison between novel hydroxyapatite enhanced PEEK and titanium implants after anterior lumbar interbody fusion

Sequential correction of sagittal vertical alignment and lumbar lordosis in adult flatback deformity

BackgroundFlatback deformity, or lumbar hypolordosis, can cause sagittal imbalance, causing back pain, fatigue, and functional limitation. Surgical correction through osteotomies and interbody fusion techniques can restore sagittal balance and relieve pain. This study investigated sagittal vertical alignment (SVA) and lumbar lordosis correction achieved through sequential procedures on human spine specimens. MethodsHuman T10-sacrum specimens were stratified into 2 groups: degenerative flatback specimens had smaller L1-S1 lordosis compared to the iatrogenic group (26.1°±15.0° vs. 47.8°±19.3°, p<.05). Specimens were mounted in the apparatus in simulated standing posture with a nominal sacral slope of 45 degrees and subjected to a 400N compressive follower preload. Sequential correction of degenerative lumbar flatback deformity involved: anterior lumbar interbody fusion (ALIF) at L5-S1, ALIF at L4-5, lateral lumbar interbody fusion (LLIF) at L2-3 and L3-4, and posterior column osteotomy (PCO) at L2-3 and L3-4. In iatrogenic specimens, flatback deformity was created by performing a posterior in-situ immobilization using pedicle screw instrumentation at L4-L5-S1 followed by distraction across the pedicle screws. We then performed LLIF at L2-3 and L3-4, followed by PCO at L2-3 and L3-4. ResultsStatistically significant incremental corrections were noted in SVAs and lordosis after L5-S1 ALIF, L4-5 ALIF, and PCO in degenerative flatback specimens. For the iatrogenic group, statistically significant worsening was noted in measures of standing alignment after L4-L5-S1 hypolordotic fusion. Subsequent LLIF at L2-3 and L3-4 did not significantly improve sagittal alignment. However, after PCO at L2-3 and L3-4, final alignment parameters were not significantly different than preoperative baseline values prior to hypolordotic fusion. ConclusionsALIF cages in the lower lumbar segments significantly improved sagittal alignment in degenerative flatback specimens. In the upper lumbar segments, LLIF cages alone were ineffective at enhancing lumbar lordosis. LLIF cages in conjunction with PCO improved alignment parameters in degenerative and iatrogenic flatback deformities.

Predicting Immediate Lordosis Restoration After Anterior Lumbar Interbody Fusion and the Effect of Posterior Column Osteotomies

Anterior lumbar interbody fusion (ALIF) can be combined with posterior column osteotomies (PCOs) to maximize lordotic correction. This study compares radiographic changes in regional and segmental lordosis in patients undergoing ALIF with and without PCOs. Patients >18 years old who underwent ALIF at 1 or 2 segments at a single institution (January 2014-July 2020) were included. Preoperative and postoperative radiographic parameters were determined, and a propensity-matched analysis was performed. Ninety-nine patients (53 [54%] men) underwent ALIF at 129 levels (mean [SD], 1.3 [0.46] levels; median [range] age, 61 [32-83] years). PCOs were performed in 13 (13%) patients at 19 (15%) segments. PCOs included 13 Schwab grade 1 and 6 grade 2 osteotomies. All measures, including lumbar lordosis, segmental lordosis, disc angle, and neural foramen height, increased significantly after surgery (p≤0.003). In the propensity-matched analysis, PCO was associated with greater increases in lumbar lordosis (14.9° vs. 8.2°, p=0.02), segmental lordosis (14.0° vs. 9.6°, p=0.03), and disc angle (15.0° vs. 10.2°, p=0.046). The change in disc angle more closely approximated the inherent lordosis of the cage when PCO was performed (94% vs. 62%, p=0.004). Performing PCOs and ALIFs significantly increased the radiographic correction of overall and segmental lordosis in the selected patient cohort. The disc angle achieved with ALIF without PCOs was approximately 60% of the cage lordosis. The addition of PCO allowed for greater segmental compression, enabling the disc angle to reach nearly 100% of the inherent interbody cage lordosis.

Can titanium surface technology reduce cost for biologics in anterior lumbar interbody fusion?

Advances in surface architecture and technology have made interbody fusion devices more bioactive, with the hope of facilitating the fusion process more successfully. The advent of these increasingly bioactive implants may reduce reliance on more expensive biologics that have previously been used to achieve high fusion rates. A retrospective review of prospectively collected data (August 2018-December 2019) was conducted of consecutively performed anterior lumbar interbody fusions in which an acid-etched, nanosurface-modulated, titanium interbody device packed only with corticocancellous allograft chips and local blood was used. Minimum follow-up was 1 year, and inclusion required available imaging and outcome metrics preoperatively and at 1 year. Fusion and subsidence were assessed via CT scans and/or dynamic radiographs. Health-related quality-of-life measures (Oswestry Disability Index [ODI], visual analog scale [VAS] back/leg) were collected pre- and postoperatively. In total, 55 patients met inclusion criteria (1 year of follow-up, available imaging, and outcome metrics). A total of 69 lumbar levels were treated in these 55 patients. The mean age was 67 ± 12.1 years, with 47% female patients. Roughly one-third (35%) had previous spine surgery, and approximately one-tenth (9.1%) had prior spinal fusion. A total of 20.6% were treated at multiple levels (mean levels per patient 1.2, minimum 1, maximum 3). The mean preoperative patient-reported outcomes were as follows: ODI 39.71 ± 18.15, VAS back 6.49 ± 2.19, and VAS leg 5.41 ± 2.71. One year after surgery, the mean improvements in patient-reported outcomes (vs preoperative scores) were as follows: ODI -22.9 ± 13.08 (p < 0.001), VAS back -3.75 ± 2.03 (p < 0.001), VAS leg -3.73 ± 2.32 (p < 0.001). All levels achieved fusion at 1 year postoperatively based on CT scans (65/69 levels) or dynamic radiographs (4/69 levels, change in score < 5% on flexion-extension radiographs). Four of the 65 levels were assigned to the grade 3 category according to a CT-based grading system, meaning cranial and caudal endplate bone apposition to the implant on both surfaces with no clear intervertebral bone connection through or around the implant. Sixty-one of 65 were found to have contiguous intervertebral bone bridging and thus were assigned to grade 1 (n = 54) or grade 2 (n = 7). Low-grade graft subsidence (Marchi grade 0 or I) occurred in 9 levels (13.0%) and high-grade subsidence (Marchi grade II or III) in 4 levels (5.8%). No patients required reoperation at the level of anterior lumbar interbody fusion and no radiographic or clinical evidence of pedicle screw loosening or failure was observed. The combination of advances in materials science and surface technology as demonstrated with a nanotechnology titanium cage resulted in the ability to obtain lumbar interbody fusion with allograft chips and local blood alone. Achieving high fusion rates with low-cost biologics/allograft provides for an attractive pathway toward reducing the cost of reconstructive spine care, and a potential incremental benefit for healthcare economics.