Static Interbody Research Articles

Short-Term Clinical and Radiographic Evaluation of Patients Treated With Expandable and Static Interbody Spacers Following Lumbar Lateral Interbody Fusion

ObjectiveThe goal of this study was to evaluate, using computed tomography (CT) and magnetic resonance imaging (MRI), patients who underwent oblique lateral interbody fusion (OLIF) using either expandable or static interbody spacers. MethodsThirty-five patients with degenerative disc disease were surgically treated with one-level OLIF and were followed up for more than six months. The Static group consisted of 22 patients, and 13 patients were in the Expandable group. Intraoperative findings included operative time (min), blood loss (ml), and cage size.Low back pain, leg pain, and leg numbness were measured using the Japanese Orthopedic Association score, visual analogue score, and the Roland–Morris Disability Questionnaire. Radiological evaluation using CT and MRI allowed measurement of cage subsidence, cross-sectional area (CSA) of the dural sac, disc height, segmental lordosis, foraminal height, and foraminal CSA preoperatively and six months postoperatively. ResultsThe Expandable group had significantly larger cage height and lordosis than the Static group (p < 0.05). The Expandable group also had greater dural sac area expansion and enlargement of the intervertebral foramen, as well as better correction of vertebral body slip (p < 0.05). Cage subsidence was significantly lower in the Expandable group (p < 0.05). JOA score and VAS for leg numbness were significantly better in the Expandable group (p < 0.05). ConclusionsCompared with static spacers, expandable spacers significantly enlarged the dural sac area, corrected vertebral body slippage, expanded the intervertebral foramen, and achieved good indirect decompression while reducing cage subsidence, resulting in improvement in clinical symptoms.

33. Comparison of the biomechanics of lumbar spine instrumented with standalone interbody fixation constructs vs interbody with supplemental fixation: a finite element investigation

<h3>BACKGROUND CONTEXT</h3> Low fusion rates and cage subsidence have been reported as the main drawbacks of lumbar fixation with static interbody cages. Although several clinical and biomechanical studies have evaluated the efficacy of 360 interbody fixation constructs (anterior cage plus posterior fixation), no study has reported the biomechanical comparison between such constructs and more novel techniques which use standalone fixation implants. A cadaver validated computational model of lumbar spine was used to compare the biomechanics of spine instrumented with 360 fixations vs standalone cage and screw and cage with lateral plate systems. <h3>PURPOSE</h3> To compare the mechanical stability of different interbody fixation techniques in lumbar spinal segments with standalone interbody vs static cage with posterior fixation or lateral plate system. <h3>STUDY DESIGN/SETTING</h3> Finite element modeling. <h3>OUTCOME MEASURES</h3> Range of motion across instrument segments and load sharing on vertebral endplate. <h3>METHODS</h3> An experimentally validated finite element (FE) model of L1-pelvic segment was used to simulate ALIF and LIF lumbar fixation techniques including: ALIF cage at L5-S1 plus posterior screw-rod fixation (360 construct) vs ALIF standalone (screw through the cage). LIF cage at L4-L5 vs LIF cage with integrated two-hole lateral plate system. 4WEB Medical's Truss ALIF (27mm x 25mm), Lateral Truss (22mm X 5mm) cages and 2-hole integrated plate systems were used for simulation of the surgical procedure. For 360 constructs, a generic posterior rod and screw system was used. All models were subjected to a 400N compressive pre-load followed by an 8Nm moment to simulation flexion-extension, left and right bending and axial rotation motions. The segmental kinematics and the load sharing at the inferior endplate were compared among cases. <h3>RESULTS</h3> The segmental motion in standalone ALIF construct was 1.1°(Flex-Ext), 0.9° (LB) and 0.4° vs 0.8°, 0.8° and 0.6° in 360 ALIF in the same planes of motion. When comparing lateral cases, the motions were 1.2° (Flex-Ext), 1.4° (LB) and 0.5° (AR) in lateral cage with plate vs 0.9°, 1.0° and 0.8° in the 360 lateral construct for the same loads. The peak stresses in extension for the LIF stand-alone cage were somewhat higher than the posterior instrumented cases, but not significant. When comparing the mechanical stress on the inferior endplate of the index segment, the standalone ALIF had almost 20% higher peak stress compared to the 360 ALIF. In the lateral construct, the cage-plate segment experienced 15% lower stresses on the endplate compared to the 360 lateral construct. <h3>CONCLUSIONS</h3> Our data suggest that standalone ALIF cage with screw through the cage is able to provide kinematic stability in the fixation construct comparable to the cage plus posterior fixation, although the 360 construct is able to provide slightly more stability in the sagittal plane. Also, the standalone cage results in higher stresses applied to the endplate compared the cage in 360 constructs. The lateral cage with integrated plate had superior stability in axial rotation compared to the 360 lateral construct. The loads on the endplate were also slightly lower compared to the 360-fixation case. Standalone ALIF and LIF with lateral plate are biomechanically effecient alternatives to 360-fixation constructs at least under the controlled conditions analyzed in the present study. Clinical data are required to support the findings and define the further role and application of standalone cages. <h3>FDA DEVICE/DRUG STATUS</h3> 4WEB ALIF Truss System (Approved for this indication), 4WEB Lateral Plate System (Approved for this indication), 4WEB Lateral Truss System (Approved for this indication)

Radiographic and Patient-Reported Outcomes of Lordotic Versus Non-lordotic Static Interbody Devices in Minimally Invasive Transforaminal Lumbar Interbody Fusion: A Longitudinal Comparative Cohort Study.

IntroductionMinimally invasive transforaminal lumbar interbody fusion (MI-TLIF) is increasingly used to treat lumbar degenerative pathology. Its effect on sagittal parameters remains controversial. Static and expandable lordotic interbody devices (cages) were developed to improve segmental and overall lumbar lordosis. This study aimed to compare the radiographic and patient-reported outcomes (PROs) between static lordotic and non-lordotic titanium cages in patients undergoing 1-2 level MI-TLIF for degenerative conditions. MethodsWe reviewed consecutive eligible patients who underwent 1-2 level MI-TLIF (7/2017-11/2019) at a single institution by multiple surgeons. Standing X-rays and PROs were collected at preoperative, 1-month, and 6-month postoperative intervals. Using univariate analyses, we compared the two cohorts regarding confounders, radiographic parameters, and proportions of patients reaching minimal clinically important difference (MCID) for PROs.ResultsOne-hundred-twenty-five patients were reviewed. Forty-seven had lordotic and seventy-eight non-lordotic cages. The lordotic cohort was significantly younger than the non-lordotic (55.9 years vs. 60.7 years, p= 0.042). The baseline radiographic parameters were not significantly different between cohorts. At the preoperative-6-month interval, the lordotic cohort had significant improvement in lumbar lordosis versus non-lordotic cohort (2.95° ± 7.2° vs. -0.3° ± 7.1°, p=0.024). Both cohorts showed improvement in segmental lordosis, anterior and posterior interspace height, and low subsidence grade with no significant difference between cohorts at all intervals. Overall, 69.1-83.8% of patients achieved MCID in all PROs with no significant difference between cohorts.ConclusionsThe use of a static lordotic titanium cage in 1-2 level MI-TLIF did not result in significantly different radiographic improvements or PROs compared with a non-lordotic cage.

Outcomes of Transforaminal Lumbar Interbody Fusion Using Unilateral Versus Bilateral Interbody Cages.

ObjectiveTo assess the impact of bilateral versus unilateral interbody cages on outcomes for minimally invasive transforaminal lumbar interbody fusion (MIS TLIF) procedures. MethodsA retrospective review for primary, elective, single-level MIS TLIF procedures with bilateral posterior instrumentation from 2008–2020 was performed. Patients were grouped according to unilateral or bilateral interbody cage use. Procedures performed without static interbody cages or indicated for trauma, infection, malignancy were excluded. Patient-reported outcomes (PROs) included visual analogue scale (VAS), Oswestry Disability Index, 12-item Short Form health survey physical composite score (SF-12 PCS), PatientReported Outcome Measurement Information System physical function (PROMIS-PF). PROs were collected preoperatively and postoperatively. Change in PROs (Δ) was calculated and compared between groups. Achievement of minimum clinically important difference (MCID) was calculated using established values from the literature. Achievement rates were compared between groups using logistic regression. ResultsThe study included 151 patients, with 111 unilateral and 40 bilateral cage placements. Charlson Comorbidity Index, diabetes, and insurance status differed between groups (p < 0.050). Prevalence of degenerative and isthmic spondylolisthesis (both p ≤ 0.002), operative level (p = 0.003), and postoperative length of stay (p = 0.022) significantly differed between groups. The unilateral group had lower 1-year arthrodesis rates (p = 0.035). Preoperative VAS leg (p = 0.017) and SF-12 PCS (p = 0.045) were worse for the unilateral group. ΔPROMIS-PF was greater for the bilateral group at 2 years (p = 0.001). Majority of patients achieved an overall MCID for all PROs, except VAS leg (bilateral group). ConclusionWhile preoperative status and postoperative arthrodesis rates differed, patients achieved an MCID at similar rates regardless of use of unilateral or bilateral cages.

Laterally Placed Expandable Interbody Spacers With and Without Adjustable Lordosis Improve Radiographic and Clinical Outcomes: A Two-Year Follow-Up Study.

IntroductionInterbody spacers are necessary for achieving disc height restoration when surgical intervention is used for the treatment of severe degenerative disc disease. Minimally invasive lateral lumbar interbody fusion (MIS LLIF) is a popular surgical approach that historically uses large static interbody spacers through a lateral approach. However, static spacers have been associated with iatrogenic distraction and excessive impaction forces, which may increase the risk of subsidence and loss of lordosis, compromising stability. Expandable interbody spacers with or without adjustable lordosis may help address these concerns by maximizing segmental lordosis and aiding in sagittal balance correction. This study describes the clinical and radiographic outcomes of patients treated with expandable interbody spacers with or without adjustable lordosis, for MIS LLIF.Materials and methodsThis is retrospective, single-surgeon Institutional Review Board-exempt chart review was of 103 consecutive patients who had undergone MIS LLIF at one to two contiguous level(s) utilizing expandable interbody spacers with or without adjustable lordosis (66/103 patients had adjustable lordosis spacers). Collection of clinical and radiographic functional outcomes occurred at preoperative and postoperative time points through 24 months.ResultsOne-hundred and three consecutive patients were evaluated-average age, 58.2 ± 12.1 years; 42.1% (45/107) were female. There were 78.6% (81/103) one-level cases and 21.4% (22/103) two-level cases for a total of 125 levels; 44.8% (56/125) were performed at L4-5 and 34.4% (43/125) at L3-4. The average estimated blood loss was 24.6 ± 12.3cc. Mean operative time was 61.0 ± 19.1 min, and mean fluoroscopic time was 28.2 ± 14.6 sec. Visual Analog Scale (VAS) back and leg pain scores decreased significantly by an average of 7.1 ± 1.0 points at 24 months (p<0.001). Oswestry Disability Index (ODI) scores significantly decreased by a mean of 67.4 ± 8.9 points at 24 months (p<0.001). Lumbar lordosis significantly improved by a mean of 3.1 ± 8.8° at 24 months (p=0.001). Anterior, middle, and posterior disc height significantly increased at 24 months by averages of 4.7 ± 3.1, 4.0 ± 3.0, and 2.1 ± 2.2mm, respectively (p<0.001). Neuroforaminal height had significantly increased at 24 months by a mean of 3.0 ± 3.6mm (p<0.001). Segmental lordosis significantly improved by 3.7 ± 2.9° at 24 months (p<0.001). There were 51 patients with abnormal preoperative Pelvic Incidence-Lumbar Lordosis (PI-LL) measurements that significantly improved by 9.1 ± 4.9° (p<0.001) and 52 patients with normal preoperative PI-LL measurements that improved by 0.2 ± 4.6° (p=0.748) at 24 months. One-hundred percent fusion occurred at all levels, and no findings of radiolucency were observed. One case of subsidence (1/125, 0.8%) was reported at 24 months. No implanted-related complications were reported, with 0% pseudoarthrosis and no secondary surgery required at the operative levels.ConclusionIndirect decompression and sagittal correction were achieved and maintained through a 24-month follow-up. Functional clinical outcomes significantly improved based on decreased VAS pain and ODI scores at 24 months. This study resulted in positive clinical and radiographic outcomes for patients who underwent MIS LLIF with expandable interbody spacers with or without adjustable lordosis.

Minimally invasive transforaminal lumbar interbody fusion with expandable articulating interbody spacers significantly improves radiographic outcomes compared to static interbody spacers.

The goal of minimally invasive transforaminal lumbar interbody fusion (MI TLIF) is to restore and maintain disc height and lordosis until arthrodesis occurs, while minimizing muscle disruption and improving recovery time. The purpose of this study was to compare the radiographic outcomes in patients treated with an articulating expandable spacer in MI TLIF to more traditional static spacers. This was a multi-site, multi-surgeon, Institutional Review Board-exempt, retrospective clinical study from a prospectively collected database. It included 48 patients with a diagnosis of degenerative disc disease (DDD) at one level from L2 to S1 with or without Grade 1 spondylolisthesis who underwent MI TLIF using either an articulating expandable or static interbody spacer. Twenty-seven patients were in the banana-shaped articulating expandable interbody spacer (ALTERA®, Globus Medical, Inc., Audubon, PA, USA) group, while 21 patients were in the static interbody spacer group. Both groups had supplemental posterior pedicle screw and rod fixation. Radiographic records were assessed for disc height, neuroforaminal height, and lordosis at baseline, 3 and 6 months, and final follow-up. The articulating expandable spacer group displayed significantly greater improvement in anterior disc height from baseline compared to the static spacer group at 6 weeks, 3 and 6 months, and final follow-up by averages of 2.6 mm (79%), 2.8 mm (92%), 3.4 mm (105%), and 3.8 mm (139%), respectively (P<0.05). Mean increases in posterior disc height were significantly greater in the expandable group compared to the static group by 1.2 mm (65%) and 1.7 mm (104%) at 6 months and final follow-up, respectively (P<0.05). Articulating expandable spacers produced significantly greater average improvement by 4.0 mm in neuroforaminal height from baseline to final follow-up compared to static spacers (P<0.05). Increases in intervertebral angle from baseline were significantly greater in the expandable group than in the static group at 3 and 6 months, and final follow-up by averages of 2.5°, 2.8°, and 3.1°, respectively (P<0.05). The articulating expandable spacer group resulted in significantly greater improvements in lumbar lordosis from baseline to 3 and 6 months than the static spacer group by 4.4° and 4.0°, respectively (P<0.05). MI TLIF with articulating expandable interbody spacers provides significant restoration and maintenance of disc height, neuroforaminal height, and lordosis compared to static spacers in this comparative cohort. Long-term clinical outcomes are needed to correlate with these radiographic improvements.

PEEK Versus Titanium Static Interbody Cages: A Comparison of 1-Year Clinical and Radiographic Outcomes for 1-Level TLIFs.

This was a retrospective cohort study. This study evaluates the patient-reported Health Related Quality of Life outcomes and radiographic parameters of patients who underwent a single level transforaminal lumbar interbody fusion with either a polyetheretherketone (PEEK) or titanium interbody cage. Spinal stenosis with instability is a common diagnosis that is often treated with interbody fusion, in particular transforaminal lumbar interbody fusion. Titanium and PEEK interbody cage properties have been extensively studied to understand their effect on fusion rates and subsidence. A retrospective cohort study was conducted from a single, high volume, academic hospital. Health Related Quality of Life outcomes were obtained from Outcomes Based Electronic Research Database and electronic medical record chart review. Subsidence was defined as a loss of 2 mm or more in the anterior or posterior disk height. Spinopelvic alignment parameters measured were sacral slope, pelvic tilt, pelvic incidence, lumbar lordosis, segmental lordosis, and pelvic incidence-lumbar lordosis mismatch. Fusion rates were assessed by the Brantigan-Steffee criteria. The study included a total of 137 patients (108 PEEK, 29 titanium). Overall, no significant changes were noted between the 2 groups at 3 month or 1-year follow-up. Perioperatively, patients did report improvement in all outcome parameters within the PEEK and titanium groups. No significant difference was noted in subsidence rate between the 2 groups. Segmental lordosis significantly increased within the PEEK (+4.8 degrees; P<0.001) and titanium (+4.6 degrees; P=0.003) cage groups, however no difference was noted between groups. No significant difference was noted in fusion between the PEEK and titanium cage cohorts (92.6% vs. 86.2%; P=0.36). Overall, while PEEK and titanium cages exhibit unique biomaterial properties, our study shows that there were no significant differences with respect to patient-reported outcomes or radiographic outcomes between the 2 groups at the 1-year follow-up time point. Level III.

Expandable Technology Improves Clinical and Radiographic Outcomes of Minimally Invasive Lateral Lumbar Interbody Fusion for Degenerative Disc Disease.

Static interbody spacers are standard of care for minimally invasive lateral lumbar interbody fusion (MIS LLIF). However, placement of large static interbody spacers typically requires multiple trialing, endplate preparation, and forceful impaction. A lateral expandable interbody spacer with adjustable lordosis can be inserted at a reduced height, to optimize the endplate-to-endplate fit. This study describes radiographic and clinical outcomes in patients treated using lateral titanium expandable interbody spacers with adjustable lordosis using MIS LLIF. This is a single-surgeon, retrospective, institutional review board-exempt chart review of 24 consecutive patients who underwent MIS LLIF at 1-2 contiguous level(s) using expandable spacers with adjustable lordosis. Radiographic and clinical functional outcomes were collected and compared at preoperative and postoperative time points up to 24 months. Parametric and nonparametric tests were used when appropriate. Statistical results were significant if P < .05. Twenty-four consecutive patients were evaluated with an average age of 57.8 ± 12.6 years; 45.8% were female. Visual analog scale for back pain improved by 7.3 ± 1.0 points, whereas Oswestry Disability Index scores improved by a mean of 67.5 ± 11.3 points at 24 months (P < .001). Lumbar lordosis improved by a mean of 6.3 ± 10.1° at 24 months (P < .001). There were 29 spinal levels, with 41.4% at L4-5 and 34.5% at L3-4. Anterior, middle, and posterior disc height significantly increased at 24 months by means of 4.5 ± 2.9 mm, 4.0 ± 2.8 mm, and 2.6 ± 1.9 mm, respectively (P < .001). Neuroforaminal height significantly improved by 3.3 ± 3.9 mm at 24 months (P < .001). Segmental lordosis improved by 3.6 ± 3.0° at 24 months. This study showed significant positive clinical and radiographic outcomes for patients who underwent MIS LLIF using expandable interbody spacers with adjustable lordosis. Correction of sagittal alignment was achieved and maintained up to 2-year follow-up. The use of expandable spacers with adjustable lordosis was shown to be safe and effective in this cohort. 3.

Current Concepts of Contemporary Expandable Lumbar Interbody Fusion Cage Designs, Part 1: An Editorial on Their Biomechanical Characteristics.

Bidirectional expandable designs for lumbar interbody fusion cages are the latest iteration of expandable spacers employed to address some of the common problems inherent to static interbody fusion cages. To describe the rationales for contemporary bidirectional, multimaterial expandable lumbar interbody fusion cage designs to achieve in situ expansion for maximum anterior column support while decreasing insertion size during minimal-access surgeries. The authors summarize the current concepts behind expandable spinal fusion open architecture cage designs focusing on advanced minimally invasive spinal surgery techniques, such as endoscopy. A cage capable of bidirectional expansion in both height and width to address constrained surgical access problems was of particular interest to the authors while they analyzed the relationship between implant material stiffness and geometric design regarding the risk of subsidence and reduced graft loading. Biomechanical advantages of new bidirectional, multimaterial expandable interbody fusion cages allow insertion through minimal surgical access and combine the advantages of proven device configurations and advanced material selection. The final construct stiffness is sufficient to provide immediate anterior column support while accommodating reduced sizes required for minimally invasive surgery applications. 7.

Expandable Interbody Fusion Cages: An Editorial on the Surgeon's Perspective on Recent Technological Advances and Their Biomechanical Implications.

Expandable cages have gone through several iterations since they first appeared on the market in the early 2000s. Their development was prompted by some common problems associated with static interbody cages, including migration, expulsion, dural or neural traction injury, and pseudarthrosis. To summarize current technological advances from earlier expandable lumbar interbody fusion devices to implants with vertical and medial-to-lateral expansion mechanisms. The authors review the currently available expandable cage designs, the incremental technological advances, and how these devices impact minimally invasive surgery interbody procedures and clinical outcomes. The strategic concepts intended to improve the minimally invasive application of expandable interbody fusion implants are reviewed from a surgeon's perspective in a clinical context to discuss how their use may improve patient outcomes. The geometrical configuration, effective stiffness of composite multi-material cage designs may impact the bone-implant contact area with the endplates. Hybridization strategies of expandable cage technology with modern minimally invasive and endoscopic spinal surgery techniques are presented by outlining their advantages and disadvantages. 1 CLINICAL RELEVANCE: Systematic review.

Comparative Effectiveness of Laterally Placed Expandable versus Static Interbody Spacers: A 1-Year Follow-Up Radiographic and Clinical Outcomes Study.

Study DesignRetrospective chart review.PurposeThis study compared the clinical and radiographic outcomes of patients treated with expandable and static interbody spacers following minimally invasive lateral lumbar interbody fusion (MIS-LLIF) with 12-month follow-up.Overview of LiteratureA common surgical option for the treatment of degenerative disk disease (DDD) is MIS-LLIF using static or expandable spacers to restore disk height (DH), neuroforaminal height (NH), and segmental lordosis. Static spacers may require excessive trialing and aggressive impaction, potentially leading to endplate disruption and subsidence. Expandable spacers allow for in situ expansion to help address complications associated with static spacers.MethodsThis is an Institutional Review Board-exempt review of 69 patients (static, n=32; expandable, n=37) diagnosed with DDD who underwent MIS-LLIF at 1–2 contiguous level(s) using static or expandable spacers. Radiographic and clinical outcomes were collected and compared at pre- and postoperative time points up to 12 months.ResultsThe expandable group had a significantly higher mean change in Visual Analog Scale (VAS) scores at 6 weeks, 6 months, and 12 months vs. static (∆VAS at 12 months: expandable, 6.7±1.3; static, 5.1±2.6). Mean improvement of Oswestry Disability Index (ODI) scores at 3, 6, and 12 months were significantly better for the expandable group vs. static (∆ODI at 12 months: expandable, 63.2±13.2; static, 29.8±23.4). Mean DH and NH significantly increased at final follow-up for both groups, with no significant difference in DH improvement between groups. The expandable mean NH improvement at 6 weeks and 6 months was significantly greater vs. static. Segmental lordosis significantly improved in the expandable group at all time intervals vs static. Subsidence rate at 12 months was significantly lower in the expandable group (1/46, 2.2%) vs. static (12/37, 32.4%).ConclusionsExpandable spacers resulted in a significantly lower subsidence rate, improve segmental lordosis, and VAS and ODI outcomes at 12 months vs. static.

Comparative Effectiveness of Adjustable Lordotic Expandable versus Static Lateral Lumbar Interbody Fusion Devices: One Year Clinical and Radiographic Outcomes

Aims:This study aims to understand the clinical and radiographic outcomes between patients treated with static and expandable interbody spacers with adjustable lordosis for minimally invasive (MIS) lateral lumbar interbody fusion (LLIF).Background:The use of large interbody spacers in MIS LLIF offers favorable clinical and radiographic results. Static interbody spacers may cause iatrogenic endplate damage and implant subsidence due to forceful impaction and excessive trialing. Expandable interbody spacers with adjustable lordosis offerin situexpansion that may optimize endplate contact and maximize and maintain sagittal alignment correction until fusion occurs.Objective:The objective of this study is to compare the clinical and radiographic outcomes between patients treated with static and expandable interbody spacers with adjustable lordosis for MIS LLIF.Methods:This is a multi-surgeon, retrospective, Institutional Review Board-exempt chart review of consecutive patients who underwent MIS LLIF at 1-2 contiguous level(s) using either a polyetheretherketone (PEEK) static (32 patients) or a titanium expandable spacer with adjustable lordosis (57 patients). The mean differences of radiographic and clinical functional outcomes were collected and compared from preoperative up to 12-month postoperative follow-up. Statistical results were significant if P&lt;0.05.Results:The mean improvement of VAS back pain scores from preoperative to 6 and 12 months was significantly higher in the expandable group compared to the static group (P&lt;0.05). Mean improvement of Oswestry Disability Index (ODI) scores from preoperative to 3, 6, and 12 months were significantly higher in the expandable group compared to the static group (P&lt;0.001). The expandable group had a significantly greater mean improvement in segmental lordosis from preoperative to 6 weeks, 3, 6, and 12 months (P&lt;0.001). For disc height, the mean improvement from preoperative to 6 weeks and 3 months was more significant in the expandable group compared to the static group (P&lt;0.05). In the expandable group, the mean improvement from preoperative to 6 weeks, 3, and 6 months was significantly greater compared to the static group for neuroforaminal height (P&lt;0.001). Subsidence was 0% in the expandable group and 32.4% (12/37) in the static group.Conclusion:This study showed significant positive clinical and radiographic outcomes for patients who underwent MIS LLIF using titanium expandable interbody spacers with adjustable lordosis based on significant changes in VAS back pain scores, ODI scores, and radiographic parameters at 12-month follow-up. There was a 0% subsidence rate in the expandable group, compared to a 32% subsidence rate in the static group.

Comparative Effectiveness of Expandable Versus Static Interbody Spacers via MIS LLIF: A 2-Year Radiographic and Clinical Outcomes Study

Study Design:Retrospective cohort study.Objective:The purpose of this study is to compare the radiographic and clinical outcomes of expandable interbody spacers to static interbody spacers.Methods:This is a retrospective, institutional review board–exempt chart review of 62 consecutive patients diagnosed with degenerative disc disease who underwent minimally invasive spine surgery lateral lumbar interbody fusion (MIS LLIF) using static or expandable spacers. There were 27 patients treated with static spacers, and 35 with expandable spacers. Radiographic and clinical functional outcomes were collected. Statistical results were significant if P < .05.Results:Mean improvement in visual analogue scale back and leg pain scores was significantly greater in the expandable group compared to the static group at 6 and 24 months by 42.3% and 63.8%, respectively (P < .05). Average improvement in Oswestry Disability Index scores was significantly greater in the expandable group than the static group at 3, 6, 12, and 24 months by 28%, 44%, 59%, 53%, and 89%, respectively (P < .05). For disc height, the mean improvement from baseline to 24 months was greater in the static group compared to the expandable group (P < .05). Implant subsidence was significantly greater in the static group (16.1%, 5/31 levels) compared with the expandable group (6.7%, 3/45 levels; P < .05).Conclusions:This study showed positive clinical and radiographic outcomes for patients who underwent MIS LLIF with expandable spacers compared to those with static spacers. Sagittal correction and pain relief was achieved and maintained through 24-month follow-up. The expandable group had a lower subsidence rate than the static group.

Expandable spacers provide better functional outcomes than static spacers in minimally invasive transforaminal lumbar interbody fusion.

Transforaminal lumbar interbody fusion is an effective and frequently performed surgical treatment of chronic lower back pain. Expandable interbody spacers are designed to create greater disc height through in situ expansion. It remains unclear whether the benefits of expandable technology will translate into clinical benefits. The current study compares expandable to static interbody spacers. This is a retrospective study of 99 patients (48 static and 51 expandable) at a single site. Radiographs were collected preoperatively and at 3 months postoperatively. Standard of care at this site requires radiographs to be taken past 3 months only if patients are suffering from a severe recurrence of symptoms. Patient reported outcomes, Oswestry disability index (ODI) and visual analog scale (VAS), were collected preoperatively, at 1 and 3 months postoperatively. Patients were contacted by the surgeon and patient reported outcomes were collected at a final time point. Average final follow-up for was 67.1±16.3 months and for expandable patients it was 43.0±4.2 months. At 3 months postoperatively and at final follow-up, patients treated with expandable interbody spacers had significantly lower average ODI scores than patients with static interbody spacers. Both groups reported significant reductions in VAS scores through all follow-up. At 4 years postoperative 8 static group patients and 3 expandable group patients returned for recurrence of symptoms. Expandable interbody spacers in this study were found to be comparable to static interbody spacers, with improvements in VAS and ODI scores.

P14. Comparative effectiveness of expandable versus static lateral lumbar interbody fusion devices: two-year clinical and radiographic outcomes

BACKGROUND CONTEXT Minimally invasive (MIS) lateral lumbar interbody fusion (LLIF) procedures using large interbody static spacers may require excessive trialing and forceful impaction, leading to iatrogenic endplate disruption, excessive neural retraction and implant subsidence. The in situ expansion capability offered by expandable interbody spacers facilitates insertion to help reduce endplate damage and optimize endplate contact. PURPOSE This study reported radiographic and clinical outcomes of static and expandable interbody spacers following MIS LLIF, and device-related complications including implant subsidence. STUDY DESIGN/SETTING Prospective clinical study. PATIENT SAMPLE This study included 48 patients with degenerative disc disease who underwent MIS LLIF at 1-2 contiguous level(s) using a polyether-ether-ketone static or titanium expandable intervertebral spacer. Twenty-one patients were treated with static spacers, and 27 with expandable spacers. OUTCOME MEASURES Operative time, blood loss, length of hospital stay, visual analog scale (VAS) pain scores, Oswestry disability index (ODI), RAND 36-item survey, disc height, subsidence rates. METHODS Clinical and radiographic outcomes were analyzed at 12 and 24 months postoperatively. RESULTS Mean patient age was 66.6±9.7 years, 72.9% of patients were female. No significant differences were observed between static and expandable groups in operative time (64.0±39.2min, 73.7±39.7min), estimated blood loss (35.6±29.2cc, 40.0±30.8cc), or length of hospital stay (2.0±1.3days, 2.4±1.3days), respectively (p CONCLUSIONS In this cohort, clinical use of expandable interbody spacers resulted in better outcomes through 24-month follow-up compared to static interbody spacers, with expandable group showing significant improvements in pain and disability than the static group at 24 months. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

P16. A retrospective review of transforaminal lumbar interbody fusion patients treated with expandable and static spacers

BACKGROUND CONTEXT Interbody spacers for transforaminal lumbar interbody fusion (TLIF) offer favorable clinical results. Expandable devices allow in situ expansion to optimize fit and mitigate iatrogenic endplate damage occurring during trialing/impaction seen in static devices. PURPOSE To compare patient outcomes of treatment with a static or an expandable TLIF interbody spacer STUDY DESIGN/SETTING Retrospective chart review PATIENT SAMPLE A total of 99 patients undergoing TLIF using one of two interbody spacers, 48 patients received a static peek interbody spacer and 51 received an expandable titanium interbody spacer. OUTCOME MEASURES Blood loss, length of postoperative hospital stay, operative time, Oswestry Disability Index (ODI), Visual Analog Scale (VAS), complication rates. METHODS A retrospective chart review from a single site was performed and surgical data, ODI, and VAS scores were collected. Radiographs were collected/measured when available. Comparisons between groups were performed using independent samples t-tests. Complications were compared using Fisher's exact test. RESULTS Patients treated with expandable spacers had significantly (p 24 months, compared to 12 of 48 (25%) static patients. CONCLUSIONS Patients treated with expandable interbody fusion spacers used in a transforaminal approach demonstrated significantly less blood loss, shorter stays, lower ODI scores, and significantly fewer complications at final follow-up than static spacer patients. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

Static Versus Expandable Devices Provide Similar Clinical Outcomes Following Minimally Invasive Transforaminal Lumbar Interbody Fusion.

Few studies have analyzed differences in radiographic parameters and patient-reported outcomes (PROs) between expandable and static interbody devices in patients undergoing minimally invasive transforaminal lumbar interbody fusion (MIS TLIF). To evaluate differences in radiographic parameters and PROs following MIS TLIF between static and expandable interbody devices. Patients undergoing primary, single-level MIS TLIF between 2014 and 2017 were retrospectively identified. Radiographic measurements including lumbar lordosis (LL), segmental lordosis (SL), disc height (DH), and foraminal height (FH) were performed on lateral radiographs before and after MIS TLIF with a static or expandable articulating interbody device. Radiographic outcomes and PROs were compared using paired and unpaired Student's t test. Thirty patients received expandable interbody devices and 30 patients received static interbody devices. The expandable device cohort exhibited significantly greater improvement in DH and FH at final follow-up compared with those receiving a static device. Both device cohorts experienced significant improvements in PROs at 6 months post-operatively. MIS TLIF with an expandable interbody device led to a greater increase of DH and FH than with a static interbody device. Patients undergoing MIS TLIF can expect similar improvements in PROs whether receiving a static or an expandable interbody device. Further studies are required to better understand improvements in clinical outcomes afforded by expandable interbody devices.

Wednesday, September 26, 2018 7:35 AM–9:00 AM ePosters

BACKGROUND CONTEXT Sagittal alignment is becoming an increasingly important consideration in minimally invasive spine surgery. Single level minimally invasive transforaminal lumbar interbody fusion (MIS TLIF) can have immediate impact on segmental and regional sagittal parameters. PURPOSE The purpose of this study was to compare immediate restoration of segmental (SL) and regional lordosis (RL) after single level MIS TLIF using an expandable or static interbody cage. STUDY DESIGN/SETTING All patients underwent single level MIS TLIF using tubular retractor and bilateral pedicle screw fixation with interbody cage. Measurements of preoperative RL and SL were made and compared with post operative values. Patients were divided into 3 groups based on their preoperative SL: low lordosis ( 25°). Mann Whitney u test was used to determine statistical significance of results PATIENT SAMPLE Patients who underwent single level MIS TLIF. OUTCOME MEASURES Segmental and regional lordosis after single level MIS TLIF using an expandable or static interbody cage METHODS A retrospective review of prospectively collected data on patient undergoing single level MIS TLIF using expandable or static interbody cages was performed. All patients underwent single level MIS TLIF using tubular retractor and bilateral pedicle screw fixation with interbody cage. Measurements of preoperative RL and SL were made and compared with post operative values. Patients were divided into 3 groups based on their preoperative SL: low lordosis ( 25°). Mann Whitney u test was used to determine statistical significance of results. RESULTS A total of 114 patients were included with 57 patients in the expandable cohort and 53 in the static cohort. The expandable cohort had an average age of 64 (37–86) and 34 females. The static cohort had an average age of 58 (24–80) and 27 females. In the expandable cage cohort, patients who had low lordosis preoperatively had a statistically significant increase in postoperative SL (p CONCLUSIONS This study compares the immediate impact of MIS TLIF using expandable or static cages on segmental lordosis of the lumbar spine. Our findings suggest that while cage type does not impact postoperative lordosis, a patient's preoperative lordosis can. Specifically, those patients with low lordosis preoperatively (>15°) have the highest likelihood of achieving statistically significant improvement in segmental lordosis while those with moderate (15–25°) or high (>25°) lordosis preoperatively may experience no change or even a loss of lordosis postoperatively.

Wednesday, September 26, 2018 1:00 PM – 2:00 PM What's New in MIS: 36. Static versus expandable interbody devices in minimally invasive transforaminal lumbar interbody fusion: comparison of radiographic and functional outcomes

BACKGROUND CONTEXT Minimally invasive transforaminal lumbar interbody fusion (MIS TLIF) has been demonstrated to be effective in the surgical treatment of lumbar degenerative pathologies. Advances in instrumentation, such as the development of expandable interbody devices, have been made in order to improve surgical outcomes and patient satisfaction. Previous studies have investigated surgical outcomes of different interbody devices. However, few have analyzed differences in radiographic and patient reported outcomes (PROs) between expandable and static interbody devices. PURPOSE The purpose of this study is to evaluate differences in radiographic parameters and PROs following single-level MIS TLIF between static and expandable interbody devices. STUDY DESIGN/SETTING Retrospective analysis of a prospectively managed surgical database. PATIENT SAMPLE Sixty patients who underwent a primary, single level MIS TLIF between 2014 and 2017 that had completed at least six months of postoperative follow-up. OUTCOME MEASURES Improvements in lumbar lordosis (LL), segmental lordosis (SL), disc height (DH), and foraminal height (FH), and improvements in ODI, VAS back pain, and VAS leg pain. METHODS Patients who underwent primary, single-level MIS TLIF between 2014 and 2017 were retrospectively identified. Only patients that had completed at least six months of postoperative follow-up were included. Radiographic measurements including LL, SL, DH and FH were performed on lateral radiographs before and after MIS TLIF with a static or expandable articulating interbody device. Patient characteristics were compared using chi-squared analysis and independent t test for categorical and continuous variables, respectively. Radiographic outcomes and PROs were compared using paired and unpaired Student's t test. RESULTS Sixty patients undergoing MIS TLIF were included in this analysis. Thirty patients received expandable interbody devices and 30 patients received static interbody devices. There were no differences in demographics or perioperative characteristics between cohorts. Both static and expandable device cohorts demonstrated significant increases in DH, FH, and LL (p CONCLUSIONS Undergoing MIS TLIF with an expandable interbody device led to a greater increase of DH than with a static interbody device. Patients reported significant improvements in PROs following MIS TLIF in both expandable and static interbody device cohorts. However, no differences in improvement were demonstrated between surgical cohorts. Although use of expandable interbody device led to greater increases in DH, this may not correlate with superior patient outcomes. As such, patients undergoing MIS TLIF can expect similar improvements in PROs, whether receiving a static or expandable interbody device. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.