Expandable Cage Research Articles

P133. Measuring the radiographic efficacy of indirect decompression following minimally invasive lumbar interbody fusion: a computed tomography (CT) analysis study

<h3>BACKGROUND CONTEXT</h3> The advancement of MIS techniques has led to increased reliance on indirect decompression techniques. The latest generation of MIS TLIF cages are typically expandable cages that restore disc height and achieve ligamentum flavum unbuckling with associated increased central canal area. While prior studies have measured the extent of indirect decompression associated with ALIF and LLIF, the degree of decompression achieved via MIS-TLIF has not been described. <h3>PURPOSE</h3> Assess the degree of indirect decompression following minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF). <h3>STUDY DESIGN/SETTING</h3> Single-center, multi-surgeon, retrospective review. <h3>PATIENT SAMPLE</h3> Patients undergoing MIS-TLIF without direct decompression between 3/2017 and 3/2021. Patients were included if they had a pre- and postoperative CT scan. <h3>OUTCOME MEASURES</h3> Pre- and postoperative CT scans were used to measure disc height, foraminal area (left and right) and central canal area at the operative level(s). The most recent postoperative patient reported outcome measures (PROMs) between 6 months and 2 years were used to compare against preoperative values. <h3>METHODS</h3> Postoperative CT was performed at 1-43 months based on surgeon-specific protocols. Both pre- and postoperative CT measurements were performed by two observers. PROMs were collected in a prospectively maintained database. Paired tests were used to compare changes in CT measurements and PROMs. Bivariate analysis was also done to assess correlations between the changes in CT measures and PROMs improvement. <h3>RESULTS</h3> A total of 40 patients (48 operative levels) were assessed; 16 (33.3%) of the subjects were female and 24 (50%) were male. The average age was 56.6 ± 15.9 years. The average length of follow-up was 17.9 ± 7.9 months for PROMs and 13.5 ± 9.3 months for postoperative CT imaging. There were 32 (80%) single-level and 8 (20%) two-level cases, with 23 (47.9%) operated at L4L5 and 25 (52.1%) at L5S1. Disc height, foraminal area, and central canal area all increased significantly (p < 0.001). Mean disc height increased 50%, from 4.2 to 6.3mm. Right sided foraminal area increased 23%, from 144 .5 to 177.8mm2, the left increased 21.4% from 142.8 to 173.4mm2, and the central canal increased 16.4% from 228.6 to 266 mm2. All PROMs except for SF12-MCS (p=0.439) showed a statistically significant improvement (p < 0.05). There was no correlation between each change in PROM and the increase in cross sectional canal area. <h3>CONCLUSIONS</h3> MIS-TLIF provides a significant degree of indirect decompression. Disc height, foraminal area and central canal area were all increased following insertion of the interbody cage via the MIS-TLIF technique. PROMs by 2 years demonstrated a statistically significant improvement. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

Does the application of expandable cages in TLIF provide improved clinical and radiological results compared to static cages? A meta-analysis.

PurposeThis study aimed to provide a direct meta-analysis of the evidence comparing outcomes between expandable cages and static cages in patients with transforaminal lumbar interbody fusion (TLIF).MethodsA search of relevant materials from databases was performed from inception to March 7, 2022. Clinical and radiological outcomes were included.ResultsTen studies (1,440 patients) were included. The anterior disc height and foraminal height for expandable cages were substantially higher than those for static cages at the final follow-up (P < 0.0001; P = 0.05). In comparison with static cages, although not statistically significant, expandable cages showed beneficial results, including an increase in posterior disc height and segmental lordosis. There were no statistically significant differences in segmental lordosis, lumbar lordosis, pelvic parameters, cage subsidence, or fusion rates (P > 0.05). Oswestry disability index scores for expandable cages were substantially lower than those for static cages at the final follow-up (P = 0.0007). Interestingly, although the preoperative visual analog scores for back and leg pain were significantly higher in the expandable group than in the static group (P < 0.0001; P = 0.008), there was no significant difference between the static and expandable groups during the final follow-up (P = 0.51; P = 0.85).ConclusionsExpandable cages are associated with improved functional outcomes and restored postoperative disc and foraminal heights in patients with TLIF. In addition, no statistically significant differences were observed in segmental lordosis, lumbar lordosis, pelvic parameters, cage subsidence, or fusion rate.

Static versus Expandable Interbody Fusion Devices: A Comparison of 1-Year Clinical and Radiographic Outcomes in Minimally Invasive Transforaminal Lumbar Interbody Fusion.

Retrospective cohort study. To compare the radiographic and clinical outcomes of static versus expandable interbody cages in transforaminal lumbar interbody fusion using minimally invasive surgery (MIS-TLIF). Expandable interbody cages may potentially improve radiographic and clinical outcomes following MIS-TLIF compared to static pages, but at a potentially higher cost and increased rates of subsidence. A retrospective chart review of 1- and 2-level MIS-TLIFs performed from 2014 to 2020 was reviewed. Radiographic measurements were obtained preoperatively, 6 weeks postoperatively, and at final follow-up. Patient-reported outcome measures (PROMs) including the Oswestry Disability Index, Visual Analog Scale (VAS) back, and VAS leg were evaluated. Multivariate linear regression analysis determined the effect of cage type on the change in PROMs, controlling for demographic characteristics. Alpha was set at 0.05. A total of 221 patients underwent MIS-TLIF including 136 static and 85 expandable cages. Expandable cages had significantly greater anterior (static: 11.41 mm vs. expandable: 13.11 mm, p <0.001) and posterior disk heights (static: 7.22 mm vs. expandable: 8.11 mm, p <0.001) at 1-year follow-up. Expandable cages offered similar improvements in segmental lordosis at 6 weeks (static: 1.69° vs. expandable: 2.81°, p =0.243), but segmental lordosis was better maintained with expandable cages leading to significant differences at 1-year follow-up (static: 0.86° vs. expandable: 2.45°, p =0.001). No significant differences were noted in total complication (static: 12.5% vs. expandable: 16.5%, p =0.191) or cage subsidence rates (static: 19.7% vs. expandable: 22.4%, p =0.502) groups at 1-year follow-up. Expandable devices provide greater improvements in radiographic measurements including anterior disk height, posterior disk height, and segmental lordosis, but this did not lead to significant improvements in PROMs, complication rates, subsidence rates, or subsidence distance.

Diaphragm sparing mini open thoracotomy with standalone expandable cage

Objective: An ideal surgical procedure to any vertebral fracture with cord compression produces maximum decompression, without producing additional deficits, achieve fixation by fusion of minimum number of motion segments and maintain the corrected kyphosis without any long-term deterioration. Although conventional posterior approach provides three column fixation, it invariably devitalizes the strong paraspinal muscles and posterior ligamentous complex of the involved vertebra and the adjacent segments necessary for maintaining erect posture. The lateral approach too, damages the strongest portion of the vertebra, the pedicle and sometimes the diaphragm has to be cut open and re-sutured. Conventional anterior approaches are mainly used either as a part of combined approach where in, there is extensive destruction of anterior longitudinal ligament and crus of the diaphragm and have the limitation that they cannot address the T11 and T12 fractures without cutting open the diaphragm. The anterior approach is not usually attempted as it is not a familiar approach to the neurosurgeon and literature reports increased morbidity. The main aim of this study is to encourage the reader to employ a new anterior approach toward thoracolumbar fracture management. Materials and Methods: The chief author has devised a novel, safe, mini open, diaphragm sparing approach to address all these issues, exploring a corridor between medial margin of psoas and left crus of the diaphragm which is sufficient enough for good decompression of the cord and that even a standalone broad foot plated expandable cage for stabilization is effective in correction of kyphosis without posterior supplementation or potential respiratory complications. Results: All 37 operated patients recovered well and their kyphotic angles were maintained on follow up. All patients improved neurologically without any respiratory complications potentially associated with thoracotomy. Conclusion: This prospective study proved that kyphotic corrections were better, no subsidence rates observed, and were maintained at 1 year follow-up with this novel approach.

Cervical vertebral body replacement using a modern in situ expandable and angulable corpectomy cage system: early clinical and radiological outcome

Purpose Vertebral body replacement (VBR) cages are commonly implanted to reconstruct the cervical vertebrae in cases of tumour, trauma, spondylodiscitis, and degeneration. Expandable cages have been widely used for this purpose; however, the lacking congruence at the implant-bone interface and consequent implant displacement were considered as a serious drawback of such systems. Aim of this study is to evaluate the early clinical and radiological outcome of a modern in situ not only expandable but also angulable cervical corpectomy cage system. Methods A total of 42 patients who underwent a single or multilevel cervical VBR procedure were included and retrospectively evaluated in this single-centre case series. The neurological status was assessed using American Spinal Injury Association (ASIA) score. Complications were categorized into surgical (including implant-associated) and general medical. Radiographic parameters included regional angulation, segmental height, and coronal alignment. Results Mean age was 59.5 ± 20.6 years. The recorded ASIA score improved postoperatively by 10 points (p 0.0001). Surgical including implant-associated complication rates were 19.05%. Radiographic evaluation showed a height gain of 11.2 mm (p < 0.0001), lordotic correction of 7° (p < 0.0001), and coronal alignment of 3° (p < 0.0001). At the last follow-up, loss of angulation correction of 1.9° (p 0.0002), subsidence of 1.92 mm (p 0.0006), and fusion rates of 68.42% were observed. Conclusions The use of an in situ angulable and expandable cage system in cervical VBR seems to offer better results compared to conventional static or expandable cages regarding segmental height gain, lordotic correction, and clinical improvement as well as low complication and revision rates. Significant height gain in multilevel surgeries is associated with higher rates of implant-associated complications.

Usefulness of the Round Endcap Expandable Cage Placed on the Vertebral Ring Apophysis in Anterior Spinal Reconstruction

Rectangular endcap expandable cages are common in anterior thoracolumbar spine restoration. However, the cage is often too large to place in small, elderly women. In this study, we evaluated a method to place a round endcap expandable cage on the vertebral ring apophysis in elderly women. From April 2017 to August 2020, five women (mean age 75.8 years) underwent anterior-posterior spinal fusion with a round endcap expandable cage on the vertebral ring apophysis at the thoracolumbar junction. The local kyphotic angle, coronal Cobb angle, and intervertebral height were evaluated pre-and postoperatively. Cage subsidence and bone union were evaluated. The mean local kyphotic angle, coronal Cobb angle, and intervertebral height before surgery were 35.2°, 10.0°, and 65.3 mm, respectively. Immediately postoperatively, 1 week and 3 weeks after surgery, the kyphotic angle was 13.4°, 16.6°, and 18.5°; coronal Cobb angle was 2.8°, 2.2°, and 4.3°; and intervertebral height was 76.2 mm, 71.8 mm, and 70.6 mm. Cage subsidence was not observed and the bone union was achieved in all cases. An expandable cage with a round endcap was placed in small, elderly women by inserting the cage over the strong apophysis of the vertebral body. This technique may be useful to reduce the risk of postoperative subsidence and correction loss.

Comparison of Navigated Expandable Vertebral Cage with Conventional Expandable Vertebral Cage for Minimally Invasive Lumbar/Thoracolumbar Corpectomy.

Background and Objectives: The thoracolumbar burst fracture is one of the most common spinal injuries. If the patient has severe symptoms, corpectomy is indicated. Currently, minimally invasive corpectomy with a navigated expandable vertebral cage is available thanks to spinal surgical technology. The aim of this study is to retrospectively compare clinical and radiographic outcomes of conventional and navigational minimally invasive corpectomy techniques. Materials and Methods: We retrospectively evaluated 21 patients who underwent thoracolumbar minimally invasive corpectomy between October 2016 and January 2021. Eleven patients had a navigated expandable cage (group N) and 10 patients had a conventional expandable cage (group C). Mean follow-up period was 31.9 months for group N and 34.7 months for group C, ranging from 12 to 42 months in both groups. Clinical and radiographic outcomes are assessed using values including visual analogue scale (VAS) for back pain and Oswestry disability index (ODI). This data was collected preoperatively and at 6, 12, and 24 months postoperatively. Results: Surgical time and intraoperative blood loss of both groups were not significantly different (234 min vs. 267 min, 656 mL vs. 786 mL). Changes in VAS and ODI were similar in both groups. However, lateral cage mal-position ratio in group N was lower than that of group C (relative risk 1.64, Odds ratio 4.5) and postoperative cage sinking was significantly lower in group N (p = 0.033). Conclusions: Clinical outcomes are not significantly different, but radiographic outcomes of lateral cage mal-position and postoperative cage sinking were significantly lower in the navigation group.

Do evoked potentials matter? Pre-pathologic signal change and clinical outcomes with expandable cages in lateral lumbar interbody fusion surgery

Minimally Invasive Lateral Lumbar Interbody Fusion (MIS LLIF) is a reliable technique for treatment of degenerative disk disease, foraminal stenosis and spinal deformity. The retroperitoneal transpsoas approach risks lumbar plexus injury that may result in anterior thigh pain, sensory loss and weakness. A prospective study of 64 consecutive patients undergoing MIS LLIF with expandable cages (23 standalone, 41 integrated with lateral plate) using multimodal electrophysiological monitoring was performed. We measured sequential retraction times, complications, patient reported outcome scores and electrophysiologic findings with a minimum 12-month follow-up. Incidence of evoked potential and electromyographic signal change was moderate, and rarely resulted in post-operative neurologic deficit. Evoked potential signal changes were frequently resolved by the un-breaking of the surgical table or repositioning of the retractor. Average retraction times were 24 (15–41) minutes for standalone cages and 30 (15–41) minutes for integrated cages. At follow-up, the vast majority (97%) of patients reported significant clinical improvement post-operatively with only 2 patients reporting postoperative neurologic symptoms and subsequent recovery at 12-months. The present study shows that evoked potentials combined with electromyography is a more sensitive measure of pre-pathologic lumbar plexopathy in LLIF compared to electromyography alone, especially at L3/4 and L4/5 levels. Based on our findings, there is limited clinical indication for routine neural monitoring at rostral lumbar levels. The routine inclusion of multimodal electrophysiological monitoring in lateral transpsoas surgery is recommended to minimise the risk of neural injury by enabling optimal patient and retractor positioning and continued surveillance throughout the procedure.

Cervical Spondyloptosis in a Patient With Os Odontoideum: A Case Report

A 30-year-old man presented to our clinic with progressive neck pain and dysphagia. He had been operated on for an atlantoaxial instability (os odontoideum) 7 years ago. Imaging studies revealed cervical spondyloptosis of C5-C6 and C7-T1; the neurologic examination was intact. It was decided to correct the deformity through a circumferential approach. Thus C5, C6, and C7 corpectomy, alongside anterior column reconstruction using titanium expandable cage, reinforced by posterior spinal instrumentation from occipital bone to T3 vertebra were resolved; his symptoms resolved completely following an uneventful surgery.

Radiological Evaluation of Combined Anteroposterior Fusion with Vertebral Body Replacement Using a Minimally Invasive Lateral Approach for Osteoporotic Vertebral Fractures: Verification of Optimal Surgical Procedure.

The combined anteroposterior fusion with vertebral body replacement (VBR) using a wide footplate expandable cage with a minimally invasive lateral approach has been widely used for pseudoarthrosis after osteoporotic vertebral fractures. The purpose of this study is to evaluate the radiological results of combined anteroposterior surgery using VBR and to recommend the optimal procedure. Thirty-eight elderly patients were included in this study. The mean preoperative local kyphosis angle was 29.3°, and the mean correction loss angle was 6.3°. Cage subsidence was observed in ten patients (26.3%), and UIV or LIV fracture in twelve patients (31.6%). Patients with cage subsidence were compared to those without cage subsidence to determine the causal factors. The mean number of fixed vertebrae was 5.4 vertebrae with cage subsidence and 7.4 vertebrae without cage subsidence. In addition, to precisely clarify the optimal number of fixed vertebrae, those patients with two above–two below fixation were compared to those with less than two above–two below fixation, which revealed that the correction loss angle was significantly less in two above–two below fixation (p = 0.016). Based on these results, we recommend at least two above–two below fixation with VBR to minimize the correction loss angle and prevent cage subsidence.

Anterior cervical corpectomy and fusion with stand-alone cages in patients with multilevel degenerative cervical spine disease is safe

BackgroundIn case of spinal cord compression behind the vertebral body, anterior cervical corpectomy and fusion (ACCF) proves to be a more feasible approach than cervical discectomy. The next step was the placement of an expandable titanium interbody in order to restore the vertebral height. The need for additional anterior plating with ACCF has been debatable and such technique has been evaluated by very few studies. The objective of the study is to evaluate radiographic and clinical outcomes in patients with multilevel degenerative cervical spine disease treated by stand-alone cages for anterior cervical corpectomy and fusion (ACCF).MethodsThirty-one patients (66.5 ± 9.75 years, range 53–85 years) were analyzed. Visual Analog Scale (VAS) and the 10-item Neck Disability Index (NDI) were assessed preoperatively and during follow-up on a regular basis after surgery and after one year at least. Assessment of radiographic fusion, subsidence, and lordosis measurement of Global cervical lordosis (GCL); fusion site lordosis (FSL); the anterior interbody space height (ant. DSH); the posterior interbody space height (post. DSH); the distance of the cage to the posterior wall of the vertebral body (CD) were done retrospectively. Mean clinical and radiographic follow-up was 20.0 ± 4.39 months.ResultsVAS-neck (p = 0.001) and VAS-arm (p < 0.001) improved from preoperatively to postoperatively. The NDI improved at the final follow-up (p < 0.001). Neither significant subsidence of the cages nor significant loss of lordotic correction were seen. All patients showed a radiographic union of the surgically addressed segments at the last follow up.ConclusionsApplication of a stand-alone expandable cage in the cervical spine after one or two-level ACCF without additional posterior fixation or anterior plating is a safe procedure that results in fusion. Neither significant subsidence of the cages nor significant loss of lordotic correction were seen.Trial registrationRetrospectively registered. According to the Decision of the ethics committee, Jena on 25th of July 2018, that this study doesn’t need any registration. https://www.laek-thueringen.de/aerzte/ethikkommission/registrierung/.

Expandable versus Static Transforaminal Lumbar Interbody Fusion Cages: 1-year Radiographic Parameters and Patient-Reported Outcomes

Expandable transforaminal lumbar interbody fusion (TLIF) cages capable of multidirectional in situ expansion have gained popularity as they increase axial surface area for fusion and may enhance lordotic correction through a traditional minimally invasive surgery (MIS) surgical corridor. We evaluated and compared the radiographic and clinical outcomes between a novel expandable versus static minimally invasive surgery TLIF cage for the treatment of degenerative disk disease. A single-center retrospective review of 120 consecutive adult patients undergoing 1- or 2-level MIS TLIF with an expandable (n= 60) or static cage was performed between 2015 and 2019. Preoperative and 1-year postoperative radiographic and clinical outcomes were assessed by upright flexion/extension radiographs and serial confidential surveys. One-hundred twenty patients (mean age 63.5 years, 60.0% female) undergoing 1- and 2-level MIS TLIF met inclusion criteria. A statistically significant reduction of spondylolisthesis, restoration of foraminal height as well as anterior and posterior disk height was achieved in both cohorts, however was greater in the expandable cage cohort (ECC) (all P < 0.05). Comparable rates of fusion, 93% and 91%, were observed in the ECC and static cage cohort. A significant reduction in Numeric Pain Rating Scale back and Oswestry Disability Index scores were observed in both cohorts but were more pronounced in the ECC (5.9 ± 2.4 to 2.2 ± 1.9 and 37.3 ± 16.2 to 17.1 ± 15.2) versus static cage cohort (6.2 ± 2.8 to 3.2 ± 2.5 and 41.8 ± 16.1 to 24.3 ± 17.5) (P < 0.05). One instance of cage migration requiring reoperation occurred in the ECC. Taken together, these radiographic and clinical findings suggest an expandable cage placed through an MIS corridor represents a safe, equitable, and efficacious alternative to a static TLIF in adults with degenerative lumbar pathology.

Poor Fusion Rates Following Cervical Corpectomy Reconstructed With an Expandable Cage: Minimum 2-Year Radiographic and Clinical Outcomes.

BACKGROUNDExpandable cages are often used to reconstruct cervical corpectomies but there are few long-term follow-up studies with large numbers.OBJECTIVETo analyze the clinical and radiographic results of cervical corpectomy reconstructed with expandable cages for degenerative stenosis.METHODSWe performed a retrospective analysis of 78 patients with degenerative cervical stenosis treated with a corpectomy reconstructed with an expandable cage. We evaluated the clinical and radiographic outcomes, as well as complications of the procedure at a minimum 2-yr follow-up.RESULTSThere was a decrease in the visual analog scale pain average from 75 mm to 8.5 mm (P = .02); a decrease in the Neck Disability Index average from 55% to 12% (P = .009); and improvement in the Japanese Orthopaedic Association average from 12 to 14 points (P = .01). There was a change in cervical lordosis (Cobb method) average from −9.3° to −15.1° (P = .002), without significant loss of lordosis (P = .63). The fusion rate, by criteria of the Cervical Spine Research Society (CSRS), was low: using dynamic X-rays – 50% (n = 39/78) and using computed tomography (CT) – 47.4% (n = 37/78). A total of 11 patients (14.1%) suffered complications.CONCLUSIONTo our knowledge, this is the largest series (78) with a minimum 2-yr follow-up in the literature and the first using the dynamic radiographic and CT criteria endorsed by the CSRS. Using these criteria, our fusion rates were much lower than all previous reports in the literature. Despite this, patient-reported outcomes were reasonable. There was a relatively low incidence of perioperative complications, most of which were likely not implant-specific and there was only 1 case of implant failure.

Vertebral metastasis of renal carcinoma at diagnosis. Mechanical and clinical evaluation. Surgical management

Renal cell carcinoma is among the 10 most common cancers. Metastatic disease of the spine is common and 50% of bone metastases are already present at the time of primary diagnosis. Bone metastases from renal cell carcinoma are difficult to manage, especially vertebral localization. A 48-year-old woman was diagnosed with renal cell carcinoma in the context of low back pain. The patient presented two skeleton metastases at diagnosis (T11 and 5th rib). The patient received neoadjuvant treatment with cabozantinib, followed by removal of the renal tumor. Radiotherapy was administered for the lumbar lesion. In spite of the radiotherapy treatment, increased low back pain limiting mobility and ambulation. MRI showed an occupation of the spinal canal, without neurological lesion. The SINS scale revealed a score of 14 (vertebral instability). The patient's prognosis was greater than 12 months according to the Tokuhashi score. Based on clinical and mechanical criteria, surgical treatment of the vertebral lesion was decided. T11 vertebrectomy was performed, the reconstruction was made with an expandable cage, and T8 a L2 posterior spinal arthrodesis. A partial resection of the fifth rib was performed in order to remove the whole macroscopic tumor. After 3 months, she was diagnosed with a local infection, treated by irrigation, debridement and antibiotherapy, with good evolution. At 1-year follow-up, she has no low back pain or functional limitation. Follow-up chest-abdomen-pelvis computed CT scan showed absence of disease progression, furthermore, the vertebral arthrodesis shows fusion signs. At the time of this report, there are no clinical or radiological data of infection.

Minimally Invasive L5 Corpectomy with Navigated Expandable Vertebral Cage: A Technical Note.

Background: Conventional L5 corpectomy requires a large incision and an extended period of intraoperative fluoroscopy. We describe herein a new L5 corpectomy technique. Methods: A 79-year-old woman was referred to our hospital for leg pain and lower back pain due to an L5 vertebral fracture. Her daily life had been affected by severe lower back pain and sciatica for more than 2 months. We initially performed simple decompression surgery, but this proved effective for only 10 months. Results: For revision surgery, the patient underwent minimally invasive L5 corpectomy with a navigated expandable cage without fluoroscopy. The second surgery took 215 min, and estimated blood loss was 750 mL. The revision surgery proved successful, and the patient could then walk using a cane. In terms of clinical outcomes, the Oswestry Disability Index improved from 66% to 24%, and the visual analog scale score for lower back pain improved from 84 to 31 mm at the 1-year follow-up. Conclusions: Minimally invasive L5 corpectomy with a navigated expandable vertebral cage is effective for reducing cage misplacement and surgical invasiveness. With this new technique, surgeons and operating room staff can avoid the risk of adverse events due to intraoperative radiation exposure.

Direct Lateral Corpectomy and Reconstruction Using an Expandable Cage Improves Local Kyphosis but Not Global Sagittal Alignment.

Recently, an expandable cage equipped with rectangular footplates has been used for anterior vertebral replacement in osteoporotic vertebral fracture (OVF). However, the postoperative changes in global alignment have not been elucidated. The purpose of this study was to evaluate local and global spinal alignment after anterior and posterior spinal fixation (APSF) using an expandable cage in elderly OVF patients. This retrospective multicenter review assessed 54 consecutive patients who underwent APSF for OVF. Clinical outcomes were compared between postoperative sagittal vertical axis (SVA) > 95 mm and ≤95 mm groups to investigate the impact of malalignment. SVA improved by only 18.7 mm (from 111.8 mm to 93.1 mm). VAS score of back pain at final follow-up was significantly higher in patients with SVA > 95 mm than SVA ≤ 95 mm (42.4 vs. 22.6, p = 0.007). Adjacent vertebral fracture after surgery was significantly more frequent in the SVA > 95 mm (37% vs. 11%, p = 0.038). Multiple logistic regression showed significantly increased OR for developing adjacent vertebral fracture (OR = 4.76, 95% CI 1.10–20.58). APSF using the newly developed cage improves local kyphotic angle but not SVA. The main cause for the spinal malalignment after surgery was postoperative development of adjacent vertebral fractures.

Minimally Invasive Transforaminal Lumbar Interbody Fusion Using Expandable Cages: Increased Risk of Late Postoperative Subsidence Without a Real Improvement of Perioperative Outcomes: A Clinical Monocentric Study

Minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) is one of several approaches to lumbar interbody fusion that has proven to be a safe and effective treatment for symptomatic lumbar degenerative disease The clinical outcomes of MIS-TLIF are generally favorable, but there is still controversy regarding its ability to restore sagittal alignment. For this reason, expandable transforaminal lumbar interbody fusion cages have been developed and designed to improve ability to restore disc height and segmental lordosis. The use of expandable cages in transforaminal lumbar interbody fusion has increased drastically; however, it is not clear how effective cage expansion is in regard to disc space lordosis, distraction, and long-term outcome. We reviewed a cohort of patients with symptomatic lumbar degenerative disc pathology who underwent MIS-TLIF at our institution. We compared clinical and radiographic outcomes of expandable versus nonexpandable cage use in MIS-TLIF focusing on mean changes in segmental lordosis, disc height, and postoperative complications. The results were compared with other studies reported in the international literature. Mean change in segmental lordosis was not significantly different between the 2 groups. A significantly higher rate of postoperative subsidence was demonstrated in the expandable cage group. This study established that expandable cage use in single-level transforaminal lumbar interbody fusion did not reduce the rate of postoperative complications, but rather significantly increased a patient's risk of postoperative subsidence. Expandable cages do not presently demonstrate improved clinical outcomes or improved sagittal alignment compared with static cages.

65. Subsidence after minimally invasive transforaminal lumbar interbody fusion with expandable cage: Rates and clinical impact

<h3>BACKGROUND CONTEXT</h3> Minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) is commonly used to treat lumbar spinal stenosis with degenerative disc disease. Expandable cage technology has been increasingly adopted and has demonstrated successful results, offering a larger footprint and intraoperative height adjustment, enabling more precise dialing in of sagittal alignment and disc height. While many advances have been made, endplate violation and postoperative cage subsidence can still be seen. <h3>PURPOSE</h3> To determine the rate and clinical implications of subsidence after expandable cage use in MI-TLIF. <h3>STUDY DESIGN/SETTING</h3> Retrospective cohort study. <h3>PATIENT SAMPLE</h3> Patients undergoing MI-TLIF for degenerative disc disease using articulating, expandable cages. <h3>OUTCOME MEASURES</h3> Patient-reported outcome measures (PROMs), including the Oswestry Disability Index (ODI), visual analog scale (VAS) for back/leg pain, Short Form-12 (SF-12), and PROMIS physical function (PF). <h3>METHODS</h3> Patients undergoing MI-TLIF for degenerative disc disease using articulating, expandable cages from 2017-2019 were retrospectively studied. AP and lateral radiographs were reviewed and evaluated for the presence or absence of subsidence intraoperatively and at follow-up times including 2 weeks, 6 weeks, 12 weeks, 6 months and 1 year postoperatively. Each of the four corners of the implant was evaluated, and subsidence was determined to have occurred if there was endplate violation ≥3mm at any corner. Patient-reported outcome measures, including the ODI, VAS for back/leg pain, SF-12 and PROMIS PF were recorded at the preoperative and follow-up time points. Fusion was assessed 1-year postoperatively via CT. <h3>RESULTS</h3> A total of 87 patients were included, with mean age 58.3 years (SD,13.4). Of 87 total patients, 13 (14.9%) demonstrated subsidence, with the majority (84.6%) of cases occurring within the first 12 weeks. Patients who had subsidence were older (67.2 vs 56.7 yrs; p=0.009), had lower bone quality (p=0.049), and were more likely to have 2-level surgery compared to those without (p=0.032). On multiple regression analysis, age was the only variable which retained significance when comparing the subsidence and no subsidence groups (p=0.04). There were significant differences in subsidence rate with greater implant height (p=0.013) and smaller width (p=0.026). With the exception of SF-12 PCS at 1-year postoperative, there were no significant differences in any patient-reported outcomes between the 2 groups. The overall fusion rate was 90.5% (57/63 levels) at 1-year postoperative, with no significant difference in fusion rate between the subsidence and no subsidence groups. <h3>CONCLUSIONS</h3> The rate of subsidence after MI-TLIF was 14.9%, with the majority of cases occurring within the first 12 weeks postoperatively. Patients who had subsidence were older with lower bone quality, had cages with greater height and smaller width, and were more likely to have 2-level surgery. With the exception of SF-12 PCS at 1 year, there were no significant differences in any of the PROMs between the groups. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

28. Does loss of spondylolisthesis reduction impact clinical and radiographic outcomes after minimally invasive transforaminal lumbar interbody fusion?

<h3>BACKGROUND CONTEXT</h3> Minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) is the workhorse minimally invasive treatment for patients with degenerative lumbar stenosis and spondylolisthesis refractory to nonoperative care. While the basic tenets of surgical treatment do not differ between minimally invasive and open techniques, surgeons performing MI-TLIF are more likely to attempt reduction of spondylolisthesis in order to optimize restoration of canal dimensions due to a greater reliance on indirect decompression, which has been shown to be effective. While intraoperative reduction is often successful, postoperative loss of reduction and slip recurrence can be seen. <h3>PURPOSE</h3> To determine the rate and clinical impact of slip recurrence after MI-TLIF with expandable cage technology. <h3>STUDY DESIGN/SETTING</h3> Retrospective cohort study. <h3>PATIENT SAMPLE</h3> Patients undergoing MI-TLIF for degenerative spondylolisthesis using an articulating, expandable cage <h3>OUTCOME MEASURES</h3> Patient-reported outcome measures (PROMs), including the Oswestry Disability Index (ODI), visual analog scale (VAS) for back/leg pain, Short Form-12 (SF-12) and PROMIS Physical Function (PF) <h3>METHODS</h3> Patients undergoing MI-TLIF for degenerative spondylolisthesis using articulating, expandable cages from 2017-2019 were retrospectively studied. Lateral radiographs were reviewed and evaluated for the presence or absence of spondylolisthesis preoperatively, intraoperatively, and at follow-up times including 2 weeks, 6 weeks, 12 weeks, 6 months and 1-year postoperatively. Spondylolisthesis was measured from the posterior inferior corner of the cephalad vertebra to the posterior superior corner of the caudal vertebral, with any measurement >1mm classified as spondylolisthesis, and Meyerding grade was noted. Intraoperative reduction was measured and loss of reduction was defined as >1mm increase in spondylolisthesis comparing follow-up imaging to intraoperative films. PROMs were recorded at the preoperative and follow-up time points. Fusion was assessed 1-year postoperatively via CT. <h3>RESULTS</h3> A total of 63 patients and 70 levels were included, with mean age 59.8 years (SD,13.8). Nineteen levels (27.1%) had complete reduction intraoperatively, 40 (57.1%) had partial reduction and 11 (15.7%) had no reduction. Of the 30 levels with loss of reduction (50.8%), 20 (66.7%) occurred by 2 weeks postoperatively and 28 (93.3%) occurred by 12 weeks postoperatively. At 6 months, there were significant differences between those who had loss of reduction and those who did not in VAS back pain (3.0 vs 0.9, p=0.017) and SF-12 PCS (41.5 vs 50.0, p=0.035), but no differences were found between the groups for any instruments at any other time points. The overall fusion rate was 89.5% (34/38) at 1 year postoperatively. There was no significant difference in fusion rate between the loss of reduction (16/18) and no loss of reduction (18/20) groups. Patients with loss of reduction had no difference in reoperation rate (1/28) compared to those without loss of reduction (2/24). <h3>CONCLUSIONS</h3> While a majority of patients demonstrated reduction intraoperatively, 51% had loss of reduction, most commonly in the acute postoperative period. There were few differences in PROMs between patients who had loss of reduction and those who did not, suggesting that radiographic loss of reduction after MI-TLIF in the setting of degenerative spondylolisthesis may not be clinically meaningful. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

P34. Cage placement is a predictor of postoperative subsidence in expandable and non-expandable cages

P34. Cage placement is a predictor of postoperative subsidence in expandable and non-expandable cages