Lumbar Interbody Fusion Cage Research Articles

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.

P136. PEEK versus titanium cages in transforaminal lumbar interbody fusion: A 2-year follow-up study with clinical and radiological outcomes

<h3>BACKGROUND CONTEXT</h3> Transforaminal lumbar interbody fusion (TLIF) has evolved as a treatment option for addressing various lumbar degenerative disorders and is now an established, widely performed technique owing to high fusion rates. However, successful fusion is limited by the properties inherent to the interbody devices utilized. Despite widespread application, concern over the use of polyetheretherketone (PEEK) cages have been raised due to their intrinsic hydrophobicity and a lack of osteoconductivity. In contrast, superior rates of fusion and clinical outcomes have been reported in patient cohorts treated with titanium (Ti) cages, considering metal's bioactivity in the role of spinal fusion. Furthermore, it has been hypothesized that the increased stiffness of Ti cages may result in a higher risk of subsidence. Current studies examining the utility of metal versus PEEK cages exist but describe small sample sizes with relatively short follow-up; thus, further investigation is warranted. To justify the utilization of Ti over PEEK cages in TLIF and to confirm prior hypotheses, we must compare the revision rate, graft subsidence rate, prevalence of fusion and functional outcomes of patients treated with both cage types. <h3>PURPOSE</h3> To compare 2-year clinical and radiological outcomes of PEEK versus Ti cages in TLIF. <h3>STUDY DESIGN/SETTING</h3> Retrospective Cohort Study. <h3>PATIENT SAMPLE</h3> A total of 320 consecutive patients from 2013-2018 with a minimum follow-up of 2 years. There were 137 that underwent TLIF with a Ti cage and 183 underwent TLIF with a PEEK cage. <h3>OUTCOME MEASURES</h3> (1) Revision rate and average time to revision. (2) Graft subsidence and fusion rates. (3) Functional outcome scores including Oswestry Disability Index (ODI), Visual Analog Scale for leg (VAS-l) and back (VAS-b) pain. <h3>METHODS</h3> A retrospective review was performed to identify all patients between 2013-2018 who underwent open or minimally invasive (MI) TLIF and received either a Ti or PEEK cage with a minimum follow-up of 2 years. Demographic data was recorded and compared between both cohorts. Revision rates, time to revision, graft subsidence and fusion rates in each group were also compared. Graft subsidence was defined as cage migration into one vertebral endplate >3mm on plain radiographic measurement. Bony fusion was defined as the absence of a radiolucent gap between the cages and endplates and the presence of trabeculation and bony bridging between cages and adjacent endplates. Functional outcomes were assessed with ODI, VAS-l and VAS-b measurements at follow-up visits. All intraoperative complications were reviewed. Standard binomial and categorical comparative analyses were performed. <h3>RESULTS</h3> A total of 320 consecutive patients were included, 137 (42 open, 95 MI) in the Ti cohort and 183 (53 open, 130 MI) in the PEEK cohort. Mean follow-up of the PEEK and Ti cohorts were 44.2 and 40.8 months, respectively. Complication rates were 2.7% and 3.7% for the PEEK and Ti cohort, respectively (p= 0.04). The most common complication was durotomy. The overall revision rates were 10.4% for the PEEK cohort and 2.9% for the Ti cohort (p= 0.01). Mean time to revision was 375.4 and 346.6 days for the Ti and PEEK groups, respectively (p=0.48). The graft subsidence rate for the PEEK cohort at 3, 6, 12 and 24 months postoperatively was 2.7%, 5.5%, 7.7% and 9.8%, respectively. Subsidence in the Ti group was more favorable overall, showing 2.9%, 5.1%, 6.6% and 8.0% subsidence at the same time points. Successful spinal fusion at 24 months was 94.9% and 92.9% in the Ti and PEEK groups, respectively (p=0.5). There were 112 males and 71 females in the PEEK cohort compared to 77 males and 60 females in the Ti cohort (p= 0.4). Both groups experienced significant improvements in their functional outcome scores (ODI, VAS-leg, VAS- back) compared to their preoperative values. There were no statistically significant differences in complication rate, revision rate, graft subsidence, or spinal fusion rates between minimally invasive and open techniques within groups. <h3>CONCLUSIONS</h3> The Ti cohort in this study demonstrated a higher rate of fusion, lower rates of revision and subsidence, and similar improvements in functional outcome scores as the PEEK cohort at the 2-year timepoint. Further studies should consist of randomized controlled trials with blinded assessments to definitively conclude the advantages of Ti cages for TLIF. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

Transforaminal lumbar interbody fusion using a novel minimally invasive expandable interbody cage: patient-reported outcomes and radiographic parameters.

The goal of this study was to evaluate the clinical and radiographic outcomes of a novel multidirectional in situ expandable minimally invasive surgery (MIS) transforaminal lumbar interbody fusion (TLIF) cage. A retrospective analysis of 69 consecutive patients undergoing a 1- or 2-level MIS TLIF using an expandable cage was performed over a 2-year period. Standard MIS techniques with pedicle screw fixation were used in all cases. Upright lateral dynamic flexion/extension radiographs were reviewed prior to and at 1 year after surgery. Clinical metrics included numeric rating scale for back and leg pain, Oswestry Disability Index, and the SF-12 and VR-12 physical and mental health surveys. Radiographic parameters included anterior and posterior disc height, neuroforaminal height, spondylolisthesis, segmental lordosis, lumbar lordosis, and fusion rate. A total of 69 patients representing 75 operative levels met study inclusion criteria. The mean patient age at surgery was 63.4 ± 1.2 years, with a female predominance of 51%. The average radiographic and clinical follow-ups were 372 and 368 days, respectively. A total of 63 patients (91%) underwent 1-level surgery and 6 patients (9%) underwent 2-level surgery. Significant reductions of numeric rating scale scores for back and leg pain were observed-from 6.1 ± 0.7 to 2.5 ± 0.3 (p < 0.0001) and 4.9 ± 0.6 to 1.9 ± 0.2 (p < 0.0001), respectively. A similar reduction in Oswestry Disability Index from 38.0 ± 4.6 to 20.0 ± 2.3 (p < 0.0001) was noted. Likewise, SF-12 and VR-12 scores all showed statistically significant improvement from baseline (p < 0.001). The mean anterior and posterior disc heights improved from 8.7 ± 1.0 mm to 13.4 ± 1.5 mm (p = 0.0001) and 6.5 ± 0.8 mm to 9.6 ± 1.1 mm (p = 0.0001), respectively. Neuroforaminal height improved from 17.6 ± 2.0 mm to 21.9 ± 2.5 mm (p = 0.0001). When present, spondylolisthesis was, on average, reduced from 4.3 ± 0.5 mm to 1.9 ± 0.2 mm (p = 0.0001). Lumbar lordosis improved from 47.8° ± 5.5° to 58.5° ± 6.8° (p = 0.2687), and no significant change in segmental lordosis was observed. The overall rate of radiographic fusion was 93.3% at 1 year. No perioperative complications requiring operative revision were encountered. In this series of MIS TLIFs, use of this novel interbody cage was shown to be safe and effective. Significant improvements in pain and disability were observed. Effective and durable restoration of disc height and neuroforaminal height and reduction of spondylolisthesis were obtained, with concurrent gains in lumbar lordosis. Taken together, this device offers excellent clinical and radiographic outcomes via an MIS approach.

Delayed asymptomatic retroperitoneal dislodgement into the pouch of Douglas of a TLIF cage: A case report and review of the literature

Background: Intraoperative anteropulsion of a transforaminal lumbar interbody fusion (TLIF) cage is infrequent but may have disastrous complications. Here, we present an 80-year-old female whose L5-S1 TLIF cage extruded anteriorly and later migrated into the pouch of Douglas (i.e. an anterior peritoneal reflection between the uterus and the rectum) posing potential significant risks/complications, particularly of a major vessel injury. Notably, this 80-year-old patient with degenerative lumbosacral scoliosis should have only undergone a lumbar decompression alone.Case Description: An 80-year-old female underwent a two-level L4-L5 and L5-S1 TLIF to address lumbosacral canal stenosis with degenerative scoliosis. During the L5-S1 TLIF, intraoperative fluoroscopy showed the anterior displacement of the cage ventral to the sacrum. As she remained hemodynamically stable, the cage was left in place. The postoperative CT scan confirmed that the cage was located in the retroperitoneum but did not jeopardize the major vascular structures. Three months later, however, the cage migrated inferiorly into the pouch of Douglas. Although asymptomatic, general surgery and gynecology advised laparoscopic removal of the cage to avoid the potential for a major vessel/bowel perforation. However, the patient refused further surgery, and 3 years later remained asymptomatic.Conclusion: Anterior cage migration following TLIF has been rarely reported. In this case, an L5-S1 TLIF cage extruded anteriorly in an 80-year-old severely osteoporotic female and migrated 3 months later into the pouch of Douglas, posing the risk of a major vessel/bowel injury. Although surgical removal was recommended, the patient refused further surgery but remained asymptomatic 3 years later. Notably, the authors, in retrospect, recognized that choosing to perform a 2-level TLIF in an 80-year-old female reflected poor judgment.

Anterior Bridging Bone in a Newly Designed Cage for Lumbar Interbody Fusion: Radiographic and Finite Element Analysis

To evaluate the distribution of multiple anterior bridging bone (ABB) patterns using a newly designed interbody cage with 4 anterior holes that enable communication between the inside and outside of the cage and to estimate its mechanical effect by finite element analysis (FEA). Patients underwent single-level lumbar interbody fusion using ABB cages. Two raters evaluated the distribution patterns of ABB on computed tomography scans 1 year after surgery. We defined the term H-fusion as the presence of complete anterior extracage and intracage bone bridging, with ≥1 ABBs between them. We performed finite element analysis to investigate the effect of ABB on maximal stiffness. The study enrolled 98 patients. ABB was most frequently observed in the medial hole of the cages (73.7%). The mean number of ABBs was 3.65, and H-fusion was observed at 135 levels (34%). Postoperative improvement in the Oswestry Disability Index was significantly higher in patients who achieved interbody fusion and H-fusion than in patients who did not. As ABB was added, the increment in the relative maximal stiffness was most affected under flexion and extension forces. We observed an average of 3.65 complete ABBs. Finite element analysis demonstrated that ABB could increase the stability in fused segments, especially under flexion and extension stress. Our results suggest that the ABB cage, which allows communicating cross-bridging between inside and outside of the cage, may facilitate a more stable fusion process than a conventionally designed cage.

Preliminary Results of Expandable Transforaminal Lumbar Interbody Fusion Cages

Background: Compared with static cages, expandable cages for Transforaminal Lumbar Interbody Fusion (TLIF), are thought to require less posterior bony removal and nerve root retraction. They may allow the creation of a greater lordotic angle and lordosis restoration. Objective: This study investigated whether TLIF using an expandable lordotic interbody cage facilitates an improvement in both segmental lordosis and the restoration of intradiscal height. Methods: A total of 32 patients with 40 operated segments underwent TLIF surgery for lumbar degenerative disc disease and were consecutively included in this prospective observational study. Of those patients, 25 received monosegmental treatment, six were treated bisegmentally, and one was treated trisegmentally. All patients were assessed clinically and radiographically preoperatively, as well as one week, six months, and two years postoperatively. Results: Two patients required revision for screw loosening and pseudarthrosis. In four patients, the endplate was violated intraoperatively due to cage placement. Postoperatively, cage subsidence was observed in four patients. Significant improvement in the mean degree of spondylolisthesis was noted at the two-year mark. Mean segmental lordosis improved postoperatively. A significant increase in mean disc height of the treated segment was also found. Overall, with the exception of pain, no significant clinical or radiographic changes were reported between the first postoperative week and the two-year year follow-up mark. The mean pain, functional, and quality of life outcomes improved significantly from the preoperative to postoperative period, with no deterioration between six months and two years. Conclusion: This study demonstrates that favorable outcomes can be achieved by using an expandable titanium cage in TLIF procedures.

The Results of Using a Transforaminal Lumbar Interbody Fusion Cage at the Upper Lumbar Level.

AimThe aim of this study is to apply surgical treatments to upper lumbar disc hernias in order to provide lumbar stability and lumbar lordosis using a transforaminal lumbar interbody fusion (TLIF) cage and to preserve the success rate of surgical results by protecting neural structures without excessive subject tension.Material and methodsBetween 2012 and 2017, 32 patients who had undergone an operation for upper lumbar disc herniation and who had received a transforaminal lumbar interbody fusion cage using a posterior technique were evaluated retrospectively.ResultsThe radiological and clinical findings, surgical methods, and results of the patients were evaluated. In our study, 25 (78.1%) of the patients with upper lumbar disc hernias who were evaluated retrospectively were female and seven (21.9%) were male. Their average age was 55.43 years. The average follow-up was 21.75 months. The most common complaints were lower back pain, leg pain, and claudication. In the findings from neurological examinations, a positive result on the femoral stretching test occurred in 30 (93.7%) patients. In the degenerative spinal structure of patients at the L1-2 and L2-3 levels, a transforaminal lumbar interbody fusion was performed via a wide laminectomy with posterior stabilization due to a wide-bottomed disc hernia and stenosis. Only one of the patients with a neurological deficit still had a motor deficit after surgery.ConclusionWhile planning a surgery for upper lumbar disc hernias, the anatomical features of this region and the patients' radiological and neurological findings should be carefully evaluated. If TLIF is performed during upper lumbar region surgery, it may be preferable to perform it using a posterior technique.

Modified far lateral endoscopic transforaminal lumbar interbody fusion using a biportal endoscopic approach: technical report and preliminary results.

Endoscopic transforaminal lumbar interbody fusion (TLIF) has the disadvantage of the small cage size and by consequence risk for cage subsidence. We succeeded to insert a large oblique lumbar interbody fusion (OLIF) cage during biportal endoscopic TLIF. Unilateral total facetectomy was performed to expose the exiting and traversing nerve roots. The distance between the exiting and traversing nerve roots was measured before OLIF cage insertion. We inserted an OLIF cage instead of a TLIF cage. We successfully performed modified far lateral biportal endoscopic TLIF using large OLIF cages. Modified far lateral biportal endoscopic TLIF is usually suitable for the L4-5 and L5-S1 levels.

Titanium (Ti) cages may be superior to polyetheretherketone (PEEK) cages in lumbar interbody fusion: a systematic review and meta-analysis of clinical and radiological outcomes of spinal interbody fusions using Ti versus PEEK cages.

Interbody cages are commonly used to augment interbody fusion. Commonly used materials include titanium (Ti) and polyetheretherketone (PEEK), with their inherent differences. The aim of this study is to perform a systematic review and meta-analysis to compare between the various clinical and radiological outcomes of Ti and PEEK interbody spinal cages. A systematic review and meta-analysiscomparing clinical and radiological outcomes between Ti and PEEK interbody cages in patients undergoing spinal fusion was performed. PubMed, Scopus, Web of Science, Embase, and Cochrane Central Register of Controlled Trials database were searched. All studies that compared the clinical and radiological outcomes of patients who underwent Ti and PEEK cages were included. Subgroup analyses was performed to differentiate between patients who had cervical and lumbar interbody fusion. A total of 11 articles were identified, with a total of 743 patients. Spinal fusion rates at final follow-up did not differ between Ti and PEEK cages (OR 1.50, 95% CI 0.57-3.94, P = 0.41), although in patients undergoing lumbar fusion, Ti cages demonstrated superior fusion (OR 2.12, 95% CI 1.05-4.28, P = 0.04). In patients with non-infective etiologies, Ti cages had a higher rate of cage subsidence (RR 2.17, 95% CI 1.13-4.16, P = 0.02).Both types of cages had similar operating time, postoperative hematoma formation, neuropathic pain, segmental angle correction and postoperative clinical outcome improvement. In non-infective lumbar spine conditions, Ti cage may be the superior option due to the higher fusion rate. III.

Transforaminal Endoscopic Surgical Treatment for Posterior Migration of Polyetheretherketone Transforaminal Lumbar Interbody Fusion Cage: Case Series

This study aims to report the clinical outcome of treating lumbar radiculopathy in the setting of retropulsed polyetheretherketone (PEEK) transforaminal lumbar interbody fusion (TLIF) cages with transforaminal endoscopic spine surgery. A retrospective study of 8 patients with lumbar radiculopathy in the setting of a retropulsed PEEK TLIF cage were included from January 2014 to January 2019. The inclusion criteria were 1) lumbar radiculopathy in the setting of a retropulsed PEEK TLIF cage causing nerve compression and 2) follow-up at least 1 year. Patients were asked to complete the following questionnaires for outcome evaluation: visual analog scales (VAS) for leg pain and the Oswestry Disability Index (ODI). Eight patients underwent transforaminal endoscopic surgery for treatment of radiculopathy in the setting of a retropulsed PEEK TLIF cage in the 5-year period evaluated. One year after surgery, the VAS and ODI scores showed a significant decrease: average preoperative VAS and ODI scores were 6.9 ± 1.2 and 50.5 ± 10.9, and 1-year postoperative VAS and ODI scores were 2.3 ± 1.3 and 17.3 ± 5.1. Transforaminal endoscopic spine surgery for the treatment of a retropulsed PEEK TLIF cage is a safe and effective approach with low morbidity and acceptable complication rates for patients with radiculopathy secondary to a retropulsed PEEK TLIF cage. Compared with a more invasive approach to removing or drilling the PEEK TLIF cage, endoscopic spine surgery could achieve a similar improvement in the patient-reported outcomes with possibly fewer complications.

Peek versus titanium cages in transforaminal lumbar interbody fusion: A 2-year follow-up study with clinical and radiological outcomes

Peek versus titanium cages in transforaminal lumbar interbody fusion: A 2-year follow-up study with clinical and radiological outcomes

Comparative Study of Various Cages in Posterior Lumbar Interbody Fusion of the Lower Lumbar Spine

Comparative Study of Various Cages in Posterior Lumbar Interbody Fusion of the Lower Lumbar Spine

DESIGN STRATEGY OF THREE-DIMENSIONAL PRINTED CAGES TO REDUCE IMPACT-INDUCED DEBRIS ALONG THE LOAD-TRANSFERRING PATH

Peri-implant debris certainly lead to osteolysis, necrosis, pseudotumor formation, tissue granulation, fibrous capsule contractions, and even implant failure. For the three-dimensional (3D) printed cage, impaction during cage insertion is one of the most potential sources of fracture debris. A finite-element study was carried out to reduce the impact-induced debris of the 3D-printed cage. This study focused on the design strategy of solid and cellular structures along the load-transferring path. Using the finite-element method, the cellular structure of the transforaminal lumbar interbody fusion (TLIF) cage was systematically modified in the following four variations: a noncellular cage (NC), a fully cellular (FC) cage, a solid cage with a cellular structure in the middle concave (MC) zone, and a strengthened cage (SC) in the MC zone. Three comparison indices were considered: the stresses at the cage-instrument interfaces, in the MC zone, and along the specific load-transferring path. The NC and FC were the least and most highly stressed variations at the cage-instrument interfaces and in the MC zone, respectively. Along the entirely load-transferring path, the FC was still the most highly stressed variation. It showed a higher risk of stress fracture for the FC cage. For the MC and SC, the MC zone was consistently more stressed than the directly impacted zone. The further strengthened design of the SC had a lower peak stress (approximately 29.2%) in the MC zone compared with the MC. Prior to 3D printing, the load-transferring path from the cage-instrument interfaces to the cage-tissue interfaces should be determined. The cage-instrument interfaces should be printed as a solid structure to avoid impact-induced fracture. The other stress-concentrated zones should be cautiously designed to optimize the coexistence strategy of the solid and cellular structures.

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.

Endoscopic Transforaminal Lumbar Interbody Fusion With a Single Oblique PEEK Cage and Posterior Supplemental Fixation.

To demonstrate the feasibility of an endoscopically assisted minimally invasive surgery transforaminal lumbar interbody fusion (MIS-TLIF) and to study clinical outcomes with the use of a static oblique bullet-shaped cannulated poly-ether-ether-ketone (PEEK) lumbar interbody fusion cage in conjunction with platelet enriched plasma infused allograft cancellous chips and posterior supplemental fixation. In this retrospective study of 43 patients who underwent endoscopically assisted MIS-TLIF for spondylolisthesis (53.5%) and stenosis (46.3%), the Oswestry Disability Index, the visual analog scale (VAS) for back and leg pain, and the modified Macnab criteria were used as primary clinical outcome measures. Clinical outcomes were cross-tabulated against fusion grade using the Bridwell classification of interbody fusion. The majority of patients (90.7%) had excellent (8/43; 18.6%) and good (31/43; 72.1%) Macnab outcomes. There were significant VAS back score reductions from an average preoperative values of 8.9070 to a postoperative VAS score of 3.8605, and a score of 2.7674 at final follow-up (P < .0001). The reductions in the VAS leg scores were also significant from preoperative score of 5.58 to a postoperative value of 2.16, and a final follow-up score of 1.67 (P < .0001); the Oswestry Disability Index score went from a preoperative value of 54.4 to 23.3 postoperatively and 18.5 at the final follow-up (P < .0001). The vast majority of patients (92.9%) with Bridwell grade I fusion had excellent and good Macnab outcomes (P = .027). The authors recommend the use of an endoscope as an adjunct to MIS-TLIF, a minimally invasive spinal surgery technique in which many surgeons may be well versed and have a great deal of experience. Clinical outcomes with the endoscopic interbody fusion procedure with a static PEEK cage in conjunction with platelet-enriched bone allograft were favorable. 3. Feasibility study.

Current Concepts of Contemporary Expandable Lumbar Interbody Fusion Cage Designs, Part 2: Feasibility Assessment of an Endplate Conforming Bidirectional Expandable Interbody Cage.

Expandable cages that allow for bidirectional expansion, in both height and width, may offer benefits over traditional expandable cages or static cages. Effective stiffness must also be considered, as implants with exceedingly high stiffness may increase subsidence risk and reduce graft loading. A retrospective case series of 7 patients were assessed with computed tomography (CT) scan at the final 1-year follow-up to evaluate the interbody fusion and configuration of the expandable cage related to the endplates within the intervertebral space. CT scans were reformatted using cage's tantalum markers as fiducials for single-plane orientation for each intervertebral cage. Device height and width at maximum in situ expansion was measured at its anterior and posterior aspects to evaluate implant deformation. The new bone volume within each cage was measured from the same CT scan data sets and by the Bridwell classification of interbody fusion. The average difference between medial and lateral height measurements was 1.82 mm (±1.08) at the device's anterior aspect and 1.41 mm (±0.98) at the posterior aspect. The average difference between medial and lateral heights was 18.55% (±9.34) anteriorly and 15.49% (±9.24) posteriorly. There was a successful fusion in all 7 patients, as evidenced by measurable bone volume in the center of each interbody cage with an average of 586.42 mm3 (±237.06). The authors demonstrated the feasibility of successfully using bidirectionally expandable multimaterial cages to achieve interbody fusion. These composite open-architecture cages were found to conform to each patient's endplate configuration. The authors' observations support the concept of material selection impacting the effective construct stiffness. The design investigated by the authors provided sufficient anterior column support and successful fusion in all patients. 4.

PLIF surgery with titanium-coated PEEK or uncoated PEEK cages: a prospective randomised clinical and radiological study.

This study aimed to compare clinical results and fusion rates of uncoated polyetheretherketone (PEEK) cages with titanium-coated PEEK cages in posterior lumbar interbody fusion (PLIF) surgery. A prospective randomised study including 60 patients with one- or two-segment lumbar degenerative diseases. Patients received either titanium-coated PEEK cages (group A) or uncoated PEEK cages (group B). Fusion rates were evaluated on plain X-rays and CT scans after 6 and 12months. Clinical follow-up (visual analogue scale, VAS; Oswestry Disability Index score, ODI; EQ-5D) was performed for 24months. Fifty-five patients (92%) (36 female, 19 male) had a complete follow-up. There were no statistically significant differences in demographic, peri- or intraoperative data between groups A and B. ODI, VAS and EQ-5D improved significantly (p < 0.001) after surgery without statistically significant differences between the two groups. Overall, 65 operated segments could be evaluated for fusion (group A: 29 segments, group B: 36 segments, p = 0.6). Osseous integration of the cage surface improved significantly (p < 0.001) in both groups between 6 and 12months after surgery. At 12-month follow-up, neither radiolucency nor signs of instability or dislocation were noted. Fusion was present in CT scans as follows: (a) bone growth through cage pores (A: 100%, B: 100%); (b) bone growth outside the cages (A: 48%, B: 61%; p = 0.3). PEEK and titanium-coated PEEK cages for PLIF produce equally favourable clinical and radiological results up to 24months post-surgery. The fusion rate was not different.

腰椎後方進入椎体間固定術（TLIF）におけるケージ外の間隙への植骨が骨癒合に有用である

腰椎後方進入椎体間固定術（TLIF）におけるケージ外の間隙への植骨が骨癒合に有用である

Biomechanical Evaluation of two different types of Interbody Cages in Posterior Lumbar Interbody Fusion

Biomechanical Evaluation of two different types of Interbody Cages in Posterior Lumbar Interbody Fusion

Lumbar interbody fusion: recent advances in surgical techniques and bone healing strategies.

Lumbar interbody fusion (LIF) is a treatment option for low back pain secondary to lumbar instability and/or deformity. This review highlights recent studies of surgical techniques and bone healing strategies for LIF. Relevant articles were identified by searching the PubMed database from January 1948 to April 2020, with a focus on the last 5years, using the following keywords: LIF approach, LIF cage, stem cells for LIF, biomaterials for LIF, and osteobiologics for LIF. LIF procedures were traditionally performed through either a posterior approach (PLIF), or an anterior approach. Later, the transforaminal LIF approach gained popularity over the PLIF as it entailed less nerve retraction. To minimize paraspinal muscle dissections, alternative approaches including lateral LIF, oblique LIF, and minimally invasive approaches have been developed and utilized. These modifications have improved the surgical outcomes of LIF. However, the most recent rates of non-union after LIF procedures still ranged from 7 to 20% with an even higher incidence in patients with osteoporosis. This review summarizes the advantages and disadvantages of each surgical approach and current efforts to enhance LIF by improving fusion cage material properties and developing novel osteobiologic products that contain nanomaterials for controlled release of effective osteogenic proteins and mesenchymal stem cells. There have been significant advances in surgical technologies for LIF over the past decades. Post-operative non-union remains a major challenge, which could be addressed by development of more effective surgical techniques, fusion cages, and bone healing products through joint efforts from spine surgeons, bone biologists, and material engineers.