Expandable cages increase the risk of intraoperative subsidence but do not improve perioperative outcomes in single level transforaminal lumbar interbody fusion

Expandable Cages for Lumbar Interbody Fusion: A Narrative Review

Lumbar fusion surgery for treating degenerative spinal diseases has undergone significant advancements in recent years. In addition to posterior instrumentation, anterior interbody fusion techniques have been developed along with various cages for interbody fusion. Recently, expandable cages capable of altering height, lordotic angle, and footprint within the disc space have garnered significant attention. In this manuscript, we review the current status, clinical outcomes, and future prospects of expandable cages for lumbar interbody fusion based on the existing literature. Expandable cages are suitable for minimally invasive spinal surgeries. Small-sized cages can be inserted and subsequently expanded to a larger size within the disc space. While expandable cages generally demonstrate superior clinical outcomes compared to static cages, some studies have suggested comparable or even poorer outcomes with expandable cages than static cages. Careful interpretation through additional long-term follow-ups is required to assess the utility of expandable cages. If these shortcomings are addressed and the advantages are further developed, expandable cages could become suitable surgical instruments for minimally invasive spinal surgeries.

Pressure Dynamics on Intervertebral Disc Cages in Transforaminal Lumbar Interbody Fusion: A Cadaver Study

OBJECTIVE

This study aimed to quantify the change in pressure on the cage during compression manipulation in lumbar interbody fusion. While the procedure involves applying compression between pedicle screws to press the cage against the endplate, the exact compression force remains elusive. We hypothesize that an intact facet joint might serve as a fulcrum, potentially reducing cage pressure.

METHODS

Pressure on the intervertebral disc cage was measured during compression manipulation in 4 donor cadavers undergoing lumbar interbody fusion. Unilateral facetectomy models with both normal and parallel compression and bilateral facetectomy models were included. A transforaminal lumbar interbody fusion cage with a built-in load cell measured the compression force.

RESULTS

Pressure data from 14 discs indicated a consistent precompression pressure average of 68.16 N. Following compression, pressures increased to 125.99 N and 140.84 N for normal and parallel compression postunilateral facetectomy, respectively, and to 154.58 N and 150.46 N for bilateral models. A strong linear correlation (correlation coefficient: 0.967, P < 0.0001) between precompression and postcompression pressures emphasized the necessity of sufficient precompression pressure for achieving desired postcompression outcomes. None of the data showed a decrease in compression force to the cage with the compression maneuver.

CONCLUSIONS

Both normal and parallel compression maneuvers effectively increased the pressure on the cage, irrespective of the facet joint resection status. Compression manipulation consistently enhanced compressive force on the cage. However, when baseline pressure is low, the manipulation might not yield significant increases in compression force. This underlines the essential role of meticulous precompression preparation in enhancing surgical outcomes.

A Comparison of 2 Cage Sizes in Biportal Endoscopic Transforaminal Lumbar Interbody Fusion

STUDY DESIGN

Retrospective study.

OBJECTIVE

This study compared the fusion and subsidence rate and clinical outcomes when using different-sized static PEEK cages in BE-TLIF.

SUMMARY OF BACKGROUND DATA

Biportal endoscopic techniques for transforaminal lumbar interbody fusion (BE-TLIF) have been shown to have similar clinical and fusion outcomes with faster clinical recovery in comparison to tubular surgery. Subsidence of the interbody, however, could be a complication.

METHODS

Patients who underwent 1 or 2 level BE-TLIF for degenerative and isthmic spondylolisthesis between January 2019 and January 2022 were included. A 32×10 mm cage (group A) and a 40×15 mm cage (group B) were compared. The visual analog scale (VAS) for back and leg symptoms, and Oswestry disability index (ODI) were collected. Plain radiographs and computed tomography assessed fusion and subsidence at a minimum of 12 months.

RESULTS

Of the 69 enrolled patients, 39 group A patients (51 levels) and 30 group B patients (32 levels) were compared. The operation time per level was 123 ± 15.8 and 138 ± 10.5 minutes per fusion level in groups A and B, respectively (P < 0.05). ODI improved from 64.8 ± 6.2 to 15.7 ± 7.1 in group A and from 65.3 ± 5.6 to 15.1 ± 6.3 in group B at the final follow-up (P < 0.05). VAS leg and back score improvement between the groups did not differ; however, the 3-month postoperative VAS back improvement was significantly higher in group B. The final fusion rate at the final follow-up did not significantly differ; however, the fusion ratio at 1 year was higher in group B (P < 0.05). Subsidence occurred in 5 cases (9.8%) in group A and none in group B (P < 0.05).

CONCLUSION

BE-TLIF using a larger cage can be performed safely with similar patient-reported outcome measures with a faster fusion rate with less subsidence risk.

LEVEL OF STUDY

III.

Modic Changes Increase the Cage Subsidence Rate in Spinal Interbody Fusion Surgery: A Systematic Review and Network Meta-Analysis

OBJECTIVE

To compare the effect of different Modic changes (MC) grades on the cage subsidence rate after spinal interbody fusion surgery.

METHODS

We comprehensively searched the PubMed, Embase, and Web of Science databases from inception to August 13, 2023, for relevant randomized controlled trials and prospective and retrospective cohort studies. Review Manager 5.3 and STATA13.0 were used to conduct this meta-analysis. The subsidence rate was assessed using relative risk and 95% confidence intervals.

RESULTS

Six studies with a total of 716 segments were allocated to four groups according to the type of MC. The subsidence rate in the non-Modic changes (NMC) was significantly lower than that in the MC. The subsidence rate in the NMC was significantly lower than that in the MC in the subgroup of cages with extra instrumentation. No significant difference was identified between the 2 groups in the oblique lumbar interbody fusion subgroup. The subsidence rate in the NMC was significantly lower than that in the MC in the transforaminal lumbar interbody fusion subgroup. The subsidence rate in the NMC was significantly lower than that in the MC1 and MC2. We found no significant difference between NMC and MC3, MC1 and MC2, MC1 and MC3, or MC2 and MC3.

CONCLUSIONS

MC may be associated with a higher cage subsidence rate. With the increase in MC grades, the incidence of subsidence decreased gradually, but it was always higher than that in the NMC. Oblique lumbar interbody fusion may be a better choice for the treatment of lumbar degenerative disease with MC.

A Lateral Expandable Cage with Independently Adjustable Anterior and Posterior Heights Can Improve the Pressure Distribution at the Cage-Endplate Interface: A Biomechanics Study

OBJECTIVE

To investigate how the expansion trajectory of a lateral expandable cage affects pressure distribution at the cage-endplate interface under well-controlled biomechanical loading conditions.

METHODS

Three unique vertical height expansion trajectories used by clinically relevant lateral expandable cages were evaluated: craniocaudal, fixed-arc, and independently adjustable anterior and posterior height expansion. Two biomechanical loading scenarios were performed. The first scenario used custom bone foam test blocks to assess resultant pressure distribution at varying test block lordotic angles and expansion heights. The second scenario simulated expansion using synthetic spine units and compared the pressure distribution following expansion.

RESULTS

For an expandable cage with craniocaudal expansion, the pressure distribution at the cage-endplate interface was found to depend heavily on the lordotic angle of the test block (P < 0.001), but not expansion height (P = 0.634). The greatest maximum pressure occurred at higher test block lordotic angles. For an expandable cage with fixed-arc expansion, the pressure distribution shifted anteriorly throughout expansion. In the simulated expansion trials, an expandable cage with adjustable anterior and posterior height expansion was found to improve the pressure distribution at the cage-endplate interface, reducing the maximum pressure measurements by 22% and 14% in the craniocaudal and fixed-arc expansion, respectively.

CONCLUSIONS

Of the cage designs evaluated in this study, an expandable cage with independently adjustable anterior and posterior heights lowered the maximum pressure measured at the cage-endplate interface and alleviated the potential of cage edge loading, both of which are important considerations that are fundamental for a successful fusion procedure and the mitigation of implant subsidence risk.

The Endoscopic Lumbar Interbody Fusion: A Narrative Review, and Future Perspective

Lumbar interbody fusion stands as a preferred surgical solution for degenerative lumbar spine diseases. The procedure primarily aims to establish lumbar segment stability, directly addressing patient symptoms associated with spinal complications. Traditional open surgery, though effective, is linked with notable morbidities and extended recovery time. To mitigate these concerns, minimally invasive surgery (MIS) has garnered significant popularity, presenting an appealing alternative with numerous benefits such as reduced soft tissue trauma, decreased blood loss, and expedited recovery. Among MIS procedures, full endoscopic spinal surgery, characterized by its minimal invasiveness, holds the potential to further minimize morbidities while enhancing surgical outcomes. Endoscopic lumbar interbody fusion, a novel procedure within this paradigm, has gained attention for offering advantages comparable to those of minimally invasive transforaminal lumbar interbody fusion. However, the safety, efficacy, and associated surgical techniques and instrument design of this method continue to be subjects of ongoing debate. This paper critically reviews current evidence on the safety, efficacy, and advantages of endoscopic lumbar spinal interbody fusion, examining whether it could indeed supersede existing mainstream techniques.

Transforaminal lumbar interbody fusion with an expandable interbody device: Two-year clinical and radiographic outcomes

Background

The use of interbody cages as an adjunct to lumbar spinal fusion remains an important technique to enhance segmental stability, promote solid arthrodesis, maintain neuroforaminal decompression, and preserve/improve segmental lordosis. Appropriate segmental lumbar lordosis and sagittal balance is well-known to be critical for long-term patient outcomes. This study sought to evaluate the radiographic and clinical results of TLIF in patients using an articulating, expandable cage. Primary endpoint was clinical and radiographic outcomes, including complications, at 12 and 24 months.

Methods

A total of 37 patients underwent open single-level or 2-level TLIF by a single surgeon using an expandable cage with concomitant bilateral pedicle screws and posterolateral arthrodesis. Clinical outcomes included ODI and VAS for back and legs. Radiographic outcomes included pelvic incidence and tilt, lumbar and segmental lordoses, and disc height at the operative level(s). All outcomes were collected at baseline, 2-weeks, 6-weeks, 3-months, 6-months, 12-months, and 24-months postop.

Results

A total of 28 patients were available for analysis. Nine patients failed to follow-up at 24 months. Mean ODI scores showed significant improvement, from pre-to-postoperative at 24 months (55%; p<.0001). VAS for back and legs was significantly lower at 24 months on average by 72 and 79%, respectively (p<.0001 for both). Both segmental and lumbar lordoses significantly improved by 5.3° and 4.2° (p<.0001 and p=.049), respectively. Average disc height improved by 49% or 6.1 mm (p<.001). No device-related complications nor instances of measured subsidence. One patient had a superficial infection, and another had an intraoperatively repaired incidental durotomy.

Conclusions

The use of an expandable cage contributed to improvement in both segmental and lumbar lordosis with no reported complications at 24-month follow-up. All clinical measures significantly improved as well. The expandable cage design represents an effective and safe option to increase cage size and allow significant segmental lordosis correction.

Comparison of surgical outcomes between lumbar interbody fusions using expandable and static cages: a systematic review and meta-analysis

BACKGROUND

The use of static cages for lumbar interbody fusion (LIF) can cause complications such as end plate violation, graft subsidence, and nerve injury. Therefore, expandable cages that allow for in-situ expansion have been developed to overcome these problems. However, it remains uncertain whether expandable cages have better surgical outcomes than static cages do.

PURPOSE

We aimed to determine the effectiveness of expandable cages by analyzing studies that compared the surgical outcomes between the use of expandable cages and static cages.

STUDY DESIGN

A systematic review and meta-analysis.

METHODS

The preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines were used to conduct this meta-analysis and systematic review. The primary outcomes of this study were anterior disc height, posterior disc height, segmental lordosis (SL), lumbar lordosis (LL), subsidence rate, numeric rating scale (NRS) scores for back and leg pain, and Oswestry Disability Index (ODI).

RESULTS

Thirteen studies with 1,700 patients were included in the meta-analysis. Compared with static cages for LIFs, expandable cages significantly increased the anterior disc height (standardized mean difference 0.478, 95% confidence interval [CI] 0.088-0.867, p=.0162) and segmental lordosis (sMD 0.307, 95% CI 0.159-0.454, p<.0001). There were no significant differences in the posterior disc height, lumbar lordosis, subsidence rate, back pain, leg pain, or ODI between the two groups.

CONCLUSION

Expandable cages show no clear clinical benefit over static cages.

Simultaneous Single-Position Lateral Lumbar Interbody Fusion Surgery and Unilateral Percutaneous Pedicle Screw Fixation for Spondylolisthesis

OBJECTIVE

To evaluate the clinical and radiological efficacy of a combine of lateral single screw-rod and unilateral percutaneous pedicle screw fixation (LSUP) for lateral lumbar interbody fusion (LLIF) in the treatment of spondylolisthesis.

METHODS

Sixty-two consecutive patients with lumbar spondylolisthesis who underwent minimally invasive (MIS)-TLIF with bilateral pedicle screw (BPS) or LLIF-LSUP were retrospectively studied. Segmental lordosis angle (SLA), lumbar lordosis angle (LLA), disc height (DH), slipping percentage, the cross-sectional areas (CSA) of the thecal sac, screw placement accuracy, fusion rate and foraminal height (FH) were used to evaluate radiographic changes postoperatively. Visual analogue scale (VAS) and Oswestry Disability Index (ODI) were used to evaluate the clinical efficacy.

RESULTS

Patients who underwent LLIF-LSUP showed shorter operating time, less length of hospital stay and lower blood loss than MIS-TLIF. No statistical difference was found between the 2 groups in screw placement accuracy, overall complications, VAS, and ODI. Compared with MIS-TLIF-BPS, LLIF-LSUP had a significant improvement in sagittal parameters including DH, FH, LLA, and SLA. The CSA of MIS-TLIF-BPS was significantly increased than that of LLIF-LSUP. The fusion rate of LLIF-LSUP was significantly higher than that of MIS-TLIF-BPS at the follow-up of 3 months postoperatively, but there was no statistical difference between the 2 groups at the follow-up of 6 months, 9 months, and 12 months.

CONCLUSION

The overall clinical outcomes and complications of LLIF-LSUP were comparable to that of MIS-TLIF-BPS in this series. Compared with MIS-TLIF-BPS, LLIF-LSUP for lumbar spondylolisthesis represents a significantly shorter operating time, hospital stay and lower blood loss, and demonstrates better radiological outcomes to maintain lumbar lordosis, and reveal an overwhelming superiority in the early fusion rate.

Development and validation of a risk prediction model for cage subsidence after instrumented posterior lumbar fusion based on machine learning: a retrospective observational cohort study

Background

Interbody cage subsidence is a common complication after instrumented posterior lumbar fusion surgery, several previous studies have shown that cage subsidence is related to multiple factors. But the current research has not combined these factors to predict the subsidence, there is a lack of an individualized and comprehensive evaluation of the risk of cage subsidence following the surgery. So we attempt to identify potential risk factors and develop a risk prediction model that can predict the possibility of subsidence by providing a Cage Subsidence Score (CSS) after surgery, and evaluate whether machine learning-related techniques can effectively predict the subsidence.

Methods

This study reviewed 59 patients who underwent posterior lumbar fusion in our hospital from 2014 to 2019. They were divided into a subsidence group and a non-subsidence group according to whether the interbody fusion cage subsidence occurred during follow-up. Data were collected on the patient, including age, sex, cage segment, number of fusion segments, preoperative space height, postoperative space height, preoperative L4 lordosis Angle, postoperative L4 lordosis Angle, preoperative L5 lordosis Angle, postoperative PT, postoperative SS, postoperative PI. The conventional statistical analysis method was used to find potential risk factors that can lead to subsidence, then the results were incorporated into stepwise regression and machine learning algorithms, respectively, to build a model that could predict the subsidence. Finally the diagnostic efficiency of prediction is verified.

Results

Univariate analysis showed significant differences in pre-/postoperative intervertebral disc height, postoperative L4 segment lordosis, postoperative PT, and postoperative SS between the subsidence group and the non-subsidence group (p < 0.05). The CSS was trained by stepwise regression: 2 points for postoperative disc height > 14.68 mm, 3 points for postoperative L4 segment lordosis angle >16.91°, and 4 points for postoperative PT > 22.69°. If the total score is larger than 0.5, it is the high-risk subsidence group, while less than 0.5 is low-risk. The score obtains the area under the curve (AUC) of 0.857 and 0.806 in the development and validation set, respectively. The AUC of the GBM model based on the machine learning algorithm to predict the risk in the training set is 0.971 and the validation set is 0.889. The AUC of the avNNet model reached 0.931 in the training set and 0.868 in the validation set, respectively.

Conclusion

The machine learning algorithm has advantages in some indicators, and we have preliminarily established a CSS that can predict the risk of postoperative subsidence after lumbar fusion and confirmed the important application prospect of machine learning in solving practical clinical problems.

Cage subsidence-A multifactorial matter!

STUDY DESIGN

Retrospective cohort study OBJECTIVE: Wider cages are associated with improved decompression and reduced subsidence, but variation in cage physical properties limits consistent outcome analysis after thoracolumbar interbody fusion. This study investigated cage subsidence and its relationship to lateral and posterior approaches with a focus on the hypothesis that the larger surface area of lateral cages results in lower subsidence rates.

METHODS

This study retrospectively reviewed 194 patients who underwent interbody fusion between 2016 and 2019 with a primary outcome of cage subsidence. Secondary outcomes were cage distribution (patients, approaches, expandability), cage dimensions, t‑scores, length of hospital stay, blood loss, surgical time, and pelvic incidence-lumbar lordosis (PI-LL) mismatch.

RESULTS

Medical records were reviewed for 194 patients receiving 387 cages at 379 disc levels. Subsidence was identified in 35.1% of lateral cages, 40.9% of posterior cages, and 36.3% of all cages. Lower surface area (p = 0.008) and cage expandability were associated with subsidence risk. Lower anteroposterior cage length proved to be a significant factor in the subsidence of posteriorly placed cages (p = 0.007). Osteopenic and osteoporotic patients experienced cage subsidence 36.8% of the time compared to 3.5% of patients with normal t‑scores (p = 0.001). Cage subsidence correlated with postoperative deterioration of the PI-LL mismatch (p = 0.03). Patients receiving fusion augmentation with bone morphogenic protein experienced higher fusion rates (p < 0.01).

CONCLUSION

Cage subsidence is a common complication that can significantly impact operative outcomes following thoracolumbar interbody fusion. Low t‑scores, smaller surface area, cage expandability, and lower cage length in posterior approaches contribute significantly to cage subsidence.

Minimally Invasive Transforaminal Lumbar Interbody Fusion with Expandable Cages

Background

Minimally invasive surgical transforaminal lumbar interbody fusion (MIS-TLIF) is an increasingly common procedure for the treatment of lumbar degenerative pathologies. The MIS-TLIF technique often results in less soft-tissue injury compared with the open TLIF technique, reducing postoperative pain and recovery time1-3. However, the narrow surgical aperture of this minimally invasive technique has increased the difficulty of interbody cage placement. Expandable cages were designed to improve ease of insertion, improve visualization around the cage on insertion, reduce neurological retraction and injury by passing the nerve root with the implant in a collapsed state, and enable better disc-height and lordosis restoration on expansion4.

Description

This procedure is performed with the patient under general anesthesia and in a prone position. The appropriate spinal level is identified with use of fluoroscopy, and bilateral paramidline approaches are made utilizing the Wiltse intermuscular approach. Pedicle screws are placed bilaterally. A pedicle-based retractor or tubular retractor is passed along the Wiltse plane, and bilateral inferior facetectomies are performed. A foraminotomy is performed, including a superior facetectomy on the side with compression of the exiting nerve root. A thorough discectomy with end-plate preparation is performed. The disc space is sized with use of trial components. The cage is then implanted with a pre-expansion height less than the trialed height and is expanded under fluoroscopy. After expansion, the cage is backfilled with allograft and local autograft. Finally, the rods are contoured and reduced bilaterally, followed by closure in a multilayered approach.

Alternatives

Nonoperative alternatives to the minimally invasive TLIF technique include physical therapy or epidural corticosteroid injections. When surgical intervention is indicated, there are several approaches that can be utilized during lumbar interbody fusion, including the posterior, direct lateral, anterior, or oblique approaches5.

Rationale

Expandable cages are designed to be inserted in a collapsed configuration and expanded once placed into the interbody space. This design offers numerous potential advantages over static alternatives. The low-profile, expandable cages require less impaction during placement, minimizing iatrogenic end-plate damage. Additionally, expandable cages require less thecal and nerve-root retraction and provide a larger surface footprint once expanded.

Expected Outcomes

The MIS-TLIF technique has been shown to significantly reduce back pain, leg pain, and disability, and to significantly increase function, with most improvements observed after 12 months postoperatively. Patients may experience a 51% and 39% reduction in visual analogue pain scores and Oswestry Disability Index scores, respectively6. The results for expandable cages compared with traditional static cages in TLIF surgery require further study.

Important Tips

The technique utilized during insertion and placement of interbody cages plays an important role in cage subsidence. To reduce the risk of cage subsidence, cages should be placed level with the end plate and in contact with the apophyseal ring anteriorly. Additionally, caution should be taken when expanding the cage to ensure that the cage is not overexpanded, which may also increase the risk of mechanical failure and intraoperative subsidence.It is critical to understand the flexibility of the disc space and the osseous quality of the patient in order to know how much expansion may be applied through the cage without subsidence.If bullet-type cages are utilized, the tip of the cage should cross midline of the vertebral body to avoid generating iatrogenic scoliosis.Spine bone density should be investigated preoperatively in at-risk patients in order to identify osteoporotic patients, who are at greater risk for subsidence and instrumentation failure.Although advances in device technology are welcomed, surgeons should maintain a strong focus on technique to reduce complications and improve clinical outcomes when utilizing expandable cages.

Acronyms & Abbreviations

TLIF = transforaminal lumbar interbody fusionMIS = minimally invasive surgeryALIF = anterior lumbar interbody fusionMRI = magnetic resonance imagingCT = computed tomographyPEEK = polyetheretherketoneAP = anterioposteriorEMG = electromyographyDVT = deep vein thrombosisPE = pulmonary embolusODI = Oswestry Disability IndexEXP = expandable.

Biomechanical and clinical studies on lumbar spine fusion surgery: a review

Low back pain is associated with degenerative disc diseases of the spine. Surgical treatment includes fusion and non-fusion types. The gold standard is fusion surgery, wherein the affected vertebral segment is fused. The common complication of fusion surgery is adjacent segment degeneration (ASD). The ASD often leads to revision surgery, calling for a further fusion of adjacent segments. The existing designs of nonfusion type implants are associated with clinical problems such as subsidence, difficulty in implantation, and the requirement of revision surgeries. Various surgical approaches have been adopted by the surgeons to insert the spinal implants into the affected segment. Over the years, extensive biomechanical investigations have been reported on various surgical approaches and prostheses to predict the outcomes of lumbar spine implantations. Computer models have been proven to be very effective in identifying the best prosthesis and surgical procedure. The objective of the study was to review the literature on biomechanical studies for the treatment of lumbar spinal degenerative diseases. A critical review of the clinical and biomechanical studies on fusion spine surgeries was undertaken. The important modeling parameters, challenges, and limitations of the current studies were identified, showing the future research directions.

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

STUDY DESIGN

Retrospective cohort study.

PURPOSE

To compare the radiographic and clinical outcomes of static versus expandable interbody cages in transforaminal lumbar interbody fusion using minimally invasive surgery (MIS-TLIF).

OVERVIEW OF LITERATURE

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Vertebral bone quality score independently predicts cage subsidence following transforaminal lumbar interbody fusion

BACKGROUND CONTEXT

Cage subsidence following transforaminal lumbar interbody fusion (TLIF) has been associated with poor bone quality. Current evidence suggests that the magnetic resonance imaging (MRI)-based vertebral bone quality (VBQ) score correlates with poor bone quality.

PURPOSE

To our knowledge, this is the first study to assess whether the VBQ score can predict the occurrence of postoperative cage subsidence after TLIF surgery.

DESIGN/SETTING

Retrospective single-center cohort.

PATIENT SAMPLE

Patients undergoing single-level TLIF for degenerative spine disease between February 2014 and October 2021.

OUTCOME MEASURES

Extent of subsidence.

METHODS

Demographic, procedure-related, and radiographic data were collected for study patients. VBQ scores were determined from preoperative T1-weighted MRI. Subsidence was defined as ≥2 mm of migration of the cage into the superior or inferior end plate or both. Univariate and multivariate logistic regression were used to determine the correlation between potential risk factors for subsidence and actual subsidence rates.

RESULTS

Subsidence was observed among 42 of the 74 study patients. The mean VBQ scores were 2.9±0.5 for patients with subsidence and 2.5±0.5 for patients without subsidence. The difference among groups was significant (p=.003). On multivariate logistic regression, a higher VBQ score was significantly associated with an increased risk of subsidence (OR=1.5, 95% CI=1.160-1.973, p=.004) and was the only significant independent predictor of subsidence after TLIF.

CONCLUSION

We found that a higher VBQ score was significantly associated with cage subsidence following TLIF. The MRI-VBQ score may be a valuable tool for assisting in identifying patients at risk of cage subsidence following TLIF.

An update of interbody cages for spine fusion surgeries: from shape design to materials

INTRODUCTION

Discectomy and interbody fusion are widely used in the treatment of intervertebral disc-related diseases. Among them, the interbody cage plays a significant role. However, the complications related to the interbody cage, such as nonunion or pseudoarthrosis, subsidence, loosening, and prolapse of the cage, cannot be ignored. By changing the design and material of the interbody fusion cage, a better fusion effect can be obtained, the incidence of appeal complications can be reduced, and the quality of life of patients after interbody fusion can be improved.

AREAS COVERED

This study reviewed the research progress of cage design and material and discussed the methods of cage design and material to promote intervertebral fusion.

EXPERT OPINION

Current treatment of cervical and lumbar degenerative disease requires interbody fusion to maintain decompression and to promote fusion and reduce the incidence of fusion failure through improvements in implant material, design, internal structure, and function. However, interbody fusion is not an optimal solution for treating vertebral instability.Abbreviations: ACDF, Anterior cervical discectomy and fusion; ALIF, anterior lumbar interbody fusion; Axi-aLIF, axial lumbar interbody fusion; BAK fusion cage, Bagby and Kuslich fusion cage; CADR, cervical artificial disc replacement; DBM, decalcified bone matrix; HA, hydroxyapatite; LLIF/XLIF, lateral or extreme lateral interbody fusion; MIS-TLIF, minimally invasive transforaminal lumbar interbody fusion; OLIF/ATP, oblique lumbar interbody fusion/anterior to psoas; PEEK, Poly-ether-ether-ketone; PLIF, posterior lumbar interbody fusion; ROI-C, Zero-profile Anchored Spacer; ROM, range of motion; SLM, selective melting forming; TLIF, transforaminal lumbar interbody fusion or.

Comparison of the efficacy of expandable interbody fusion cage (EXP-IFC) and non-expandable interbody fusion cage (NE-IFC) in MIS-TLIF for lumbar degenerative diseases: A systematic retrospective study on 62 patients

OBJECTIVES

To investigate the clinical and radiographic outcomes of EXP-IFC in single-level MIS-TLIF.

METHODS

This study included patients aged ≥18 years who received a single-level MIS-TLIF procedure with at least 1 year of follow-up. Outcome measures: clinical features, preoperative and neurological complications. Imaging analysis included disc height (DH) restoration, surgical and contralateral side foraminal height (FH), lumbar lordosis angle (LL), segmental lordosis (SL). Visual analog scale (VAS) score for low back pain (VAS-LBP) and leg pain (VAS-LP), Oswestry Disability Index (ODI) and Japanese Orthopaedic Association (JOA) score were used to evaluate clinical outcomes. Statistical analysis was performed using independent sample t-test and sample t-test. The significance was set to p < 0.05 in univariate analysis.

RESULTS

A total of 62 patients undergoing single level MIS-TLIFs between January 2017 and January 2019 were included, with 32 NE-IFC 46.9% female, mean age 54.86 ± 11.65, mean body mass index (BMI) 24.59 ± 3.63) and 30 EXP (40% female, mean age 58.32 ± 12.99, mean BMI 24.45 ± 2.76) with no significant differences in demographics. There were no significant differences between two groups in Operative time (OT), Estimated blood loss (EBL) and Length of stay (LOS). No significant differences were found in VAS-LBP, VAS-LP, JOA and ODI in post-operation and the last follow-up between the two groups. The imaging outcome demonstrated that the mean increase in DH was significantly greater for the patients with EXP-IFC than those with NE-IFC group at 1 year follow-up (8.92 ± 0.51 mm EXP-IFC vs. 7.96 ± 0.96 mm NE-IFC, p < 0.001). The mean change in FH of operative and contralateral sides were observed to be significantly higher for the patients with EXP-IFC at 1 year follow-up (operative side:17.67 ± 2.29 mm EXP-IFC vs. 16.01 ± 2.73 mm NE-IFC, p = 0.042; contralateral side:17.32 ± 2.26 mm EXP-IFC vs. 16.10 ± 2.32 mm NE-IFC, p < 0.001), but changes in LL and SL were not significantly different. At the last follow-up, we did not find any significant difference in the fusion rate between the two groups.

CONCLUSION

Our results indicated that there may be no significant difference in short-term clinical outcomes between EXP-IFC and NE-IFC, but the use of EXP-IFC in MIS-TLIF can provide a significant restoration of disc height, and neural foraminal height compared to NE-IFC.

Comparison of Long-Term Efficacy of MIS-TLIF Intraoperative Implants in Patients with Osteoporosis

Osteoporosis and degenerative spinal disease are still an unsolvable surgical problem. It is still difficult to solve the complications related to postoperative osteoporosis, such as cage subsidence, displacement, and retraction. Expandable interbody cage is a recent innovation and an increasingly popular alternative to standard static cage. However, the clinical efficacy of MIS-TLIF combined with expandable cage for the treatment of osteoporosis has limited reports. The purpose of this paper was to analyze the efficacy of MIS-TLIF with expandable cage in patients with degenerative lumbar disease with osteoporosis. Patients with osteoporosis who received single-level MIS-TLIF and were followed up for at least 1 year were included. The outcome measures are as follows: clinical features, perioperative period, and neurological complications. JOA score and VAS pain score were used to analyze the improvement of patients’ function. Imaging analysis included segmental lordosis (SL), lumbar lordosis (LL), intervertebral disc height (DH), and the ratio of cage height to preoperative DH (RCD). The final data analysis included 284 patients with osteoporosis. 178 patients used static cages, and 106 patients used expandable cages. There was no significant difference in baseline characteristics, surgical indexes, and JOA and VAS scores between the two groups. There was no difference in SL or LL between static group and expandable group. There was no significant difference in preoperative DH between the two groups. The RCD in the expansion group was significantly lower than that in the static group. The intraoperative and postoperative sedimentation rate in the static group was significantly higher than that in the expandable group. The use of expandable cages in MIS-TLIF has shown good results for the treatment of degenerative lumbar diseases with osteoporosis. Through appropriate surgical techniques, the expandable cage can reduce the risk of cage sinking.

[Comparative study on effectiveness of percutaneous endoscopic and Wiltse-approach transforaminal lumbar interbody fusion in the treatment of lumbar spondylolisthesis]

OBJECTIVE

To compare the effectiveness of percutaneous endoscopic transforaminal lumbar interbody fusion (PE-TLIF) and Wiltse-approach TLIF (W-TLIF) in the treatment of lumbar spondylolisthesis.

METHODS

The clinical data of 47 patients with lumbar spondylolisthesis who met the selection criteria between July 2018 and June 2019 were retrospectively analyzed, in which 21 patients were treated with PE-TLIF (PE-TLIF group) and 26 patients were treated with W-TLIF (W-TLIF group). There was no significant difference between the two groups in age, gender, disease duration, level of spondylolisthesis vertebrae, spondylolisthesis degree, spondylolisthesis type, and preoperative visual analogue scale (VAS) score of low back pain and leg pain, lumbar Japanese Orthopaedic Association (JOA) score, and the disc height (DH), segmental lordosis (SL), and Taillard index (TI) of the operated vertebrae ( P>0.05). The operation time, intraoperative blood loss, postoperative drainage, postoperative bedridden time, and complications were compared between the two groups. The VAS score and JOA score were used to evaluate the improvement of pain and function. At last follow-up, DH, SL, and TI of operated vertebrae were measured by X-ray films, and lumbar CT was performed to evaluate the interbody fusion.

RESULTS

Compared with W-TLIF group, the operation time in PE-TLIF group was significantly longer, but the intraoperative blood loss and postoperative drainage were significantly less, and the postoperative bedridden time was significantly shorter ( P<0.05). There were 2 cases of transient lower limb radiating pain in PE-TLIF group and 1 case of superficial incision infection in W-TLIF group. There was no significant difference in the incidence of complications (9.5% vs. 3.8%) between the two groups ( χ ²=0.037, P=0.848). The patients in both groups were followed up 12-24 months, with an average of 17.3 months in PE-TLIF group and 17.7 months in W-TLIF group. The VAS scores of low back pain and leg pain, and the JOA scores of the two groups significantly improved at each time point after operation when compared with those before operation ( P<0.05). Compared with W-TLIF group, the VAS scores of low back pain in PE-TLIF group significantly lower at 3 days and 3 months after operation ( P<0.05), and the JOA score of PE-TLIF group was significantly higher at 3 months after operation ( P<0.05), and there was no significant difference in each score at any other time point between the two groups ( P>0.05). At last follow-up, the DH, SL, and TI of operated vertebrae of the two groups significantly improved when compared with those before operation ( P<0.05), and there was no significant difference in the differences of each parameter between the two groups ( P>0.05). According to Suk's standard, the fusion rates of PE-TLIF group and W-TLIF group were 90.5% (19/21) and 92.3% (24/26), respectively, with no significant difference ( χ ²=0.000, P=1.000). At last follow-up, there was no case of Cage sunk into the adjacent vertebral body, or dislodgement of Cage anteriorly or posteriorly in both groups.

CONCLUSION

PE-TLIF and W-TLIF are both effective in the treatment of grade Ⅰ and Ⅱ lumbar spondylolisthesis. Although the operation time is prolonged, PE-TLIF has less intraoperative blood loss and postoperative drainage, shorter postoperative bedridden time, and can get more obvious short-term improvement of low back pain and function.

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

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.