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Introduction: Anterior cervical decompression and fusion (ACDF) is the standard surgical procedure for cervical radiculopathy and myelopathy, although ACDF includes risks of adjacent segment disease (ASD) and subsequent revision procedures. Various interbody cage, plate, and screw options can be utilized. Stand-alone devices were designed to overcome undesired complications of hardware prominence and associated dysphagia, soft tissue violation, and adjacent level encroachment. Implants include biomechanical structural support (cage) composed of various materials (polyetheretherketone (PEEK)/titanium) and integral fixation (screws/blades). The purpose was to compare intraoperative, short- and long-term outcomes of revision ACDF using a stand-alone implant (ACDF-ZP group) versus traditional interbody PEEK cage, titanium plate, and screw instrumentation (ACDF-CP group)., Methods: This was a retrospective, cohort study reviewing charts of patients who underwent revision ACDF. The primary outcome measure was the incidence of postoperative dysphagia. Secondary outcomes included intraoperative, short-term, and long-term outcomes and complications., Results: Sixty-one patients were included (ACDF-ZP group = 50; ACDF-CP group = 11). In-hospital incidence of dysphagia was significantly less in the ACDF-CP group (P = 0.041). Thrity-one (62.0%) of the ACDF-ZP group reported dysphagia postoperatively, half resolved by 6 weeks, and two persisted for more than 6 months. Five (45.5%) of the ACDF-CP group reported dysphagia with most resolving within 6 weeks. There were no statistically significant differences between groups in short- or long-term complications, dysphonia, or reoperation rates. No statistical significance was seen in blood loss, operative time, hospital stay, local and global alignment, or cage subsidence., Conclusion: Rates of dysphagia were comparable between groups at short and long-term follow-up, despite a greater incidence of postoperative dysphagia in the ACDF-ZP group. All complications and occurrences of cage subsidence were observed in the ACDF-ZP group, which may be attributed to the larger sample size. Given these findings, zero-profile stand-alone implants and traditional interbody PEEK cage, titanium plate, and screw instrumentation appear to be both safe and effective options for revision ACDF., Competing Interests: The authors have declared financial relationships, which are detailed in the next section., (Copyright © 2023, Alhammoud et al.)

Functionally graded porous (FGP) interbody cage might offer a trade-off between porosity-based reduction of stiffness and mechanical properties. Using finite element models of intact and implanted lumbar functional spinal unit (FSU), the study investigated the quantitative deviations in load transfer and adaptive changes in bone density distributions around FGP interbody cages. The cage had three graded porosities: FGP-A, -B, and -C corresponded to a maximum porosity levels of 48%, 65% and 78%, respectively. Efficacy of the FGP cages were evaluated by comparing the numerically predicted results of solid-Ti and uniformly porous 78% porosity (P78) cage. Variations in stiffness and interface condition affected the strain distribution and bone remodelling around the cages. Peak strains of 0.5-1% were observed in less number of peri-prosthetic bone elements for the FGP cages as compared to the solid-Ti cage. Strains and bone apposition were considerably higher for the bonded implant-bone interface condition than the debonded case. For the FGP-C with bonded interface condition, bone apposition of 11-20% was predicted in the L4 and L5 regions of interest (ROIs); whereas the debonded model exhibited 6-10% increase in bone density. The deviations in bone density change between FGP-C and P78 model were 3-8% for L4 and L5 ROIs. FGP resulted in a reduced average micromotion (∼70-106 μm) as compared to solid-Ti (116 μm), for all physiologic movements. Compared to solid-Ti and uniformly porous cages, the FGP cage seems to be a viable alternative considering the conflicting nature of strength and porosity., Competing Interests: Declaration of competing interest The authors hereby declare that there are no potential conflicts of interest with respect to the research or publication of the article., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Study Design: This study was a retrospective observational study. Purpose: The purpose of the study was to determine the radiological and clinical outcome of using locally sourced autologous bone graft in the surgical management of single-level lumbar lytic spondylolisthesis. Background: Many spinal surgeons supplement pedicle screw fixation of lumbar spondylolisthesis with cages. In developing countries, the high cost of interbody cages has precluded their use, with surgeons resorting to filling the interbody space with different types of bone graft instead. This study reports on the clinical and radiological outcome of posterior lumbar interbody fusions for low-grade lytic spondylolisthesis using locally sourced autologous bone graft. Material and Methods: Posterior interbody fusion was performed in 22 consecutive patients over 18-month period, using (BRAND) pedicle screw system and locally sourced bone graft, i.e., bone removed during neural decompression. There were no postoperative restrictions, and all patients underwent clinical outcome measurements using Oswestry Disability Index (ODI), visual analogue pain score (VAS) at a minimum follow-up of 12 months, and computed tomography (CT) assessment of fusion with intraobserver validation by radiology consultant blinded, at 6 and12 months. Nearly 50% of the population were smokers. Results: There was significant clinical improvement in ODI, VAS back pain, and VAS leg pain (P < 0.001). By contrast, the radiologic fusion rate measured by CT at 12 months was less satisfactory at 64%. There was no difference in clinical outcome between the fused group and nonfused population. Conclusions: These results indicate that the use of locally sourced bone graft in single-level lumbar lytic low-grade spondylolisthesis. Interbody fusion provides good clinical outcomes. The use of an interbody cage may not be clinically necessary. Our radiologic outcome, however, shows inferior fusion rates compared with published data. Future research will focus on long-term outcomes [ABSTRACT FROM AUTHOR]

Inappropriate lordotic angle of lumbar fusion cage could be associated with cage damage or subsidence. The biomechanical influence of cage lordotic angle on lumbar spine has not been fully investigated. Four surgical finite element models were constructed by inserting cages with various lordotic angles at L3-L4 disc space. The four motion modes were simulated. The range of motion (ROM) decreased with increased lordotic angle of cage in flexion, extension, and rotation, whereas it was not substantially changed in bending. The maximum stress in cage decreased with increased lordotic angle of cage in all motion modes. The maximum stress in endplate at surgical level increased with increased lordotic angle of cage in flexion and rotation, whereas it was not substantially changed in extension and bending. The facet joint force (FJF) was much smaller than that for the intact conditions in extension, bending, and rotation, while it was not substantially changed in flexion. In conclusion, the ROM, stresses in the cage and endplate at surgical level are sensitive to the lordotic angle of cage. The increased cage lordotic angle may provide better stability and reduce the risk of cage damage, whereas it may increase the risk of subsidence in flexion and rotation. [ABSTRACT FROM AUTHOR]

Study DesignRetrospective case series.PurposeTo present radiographic outcomes following anterior lumbar interbody fusion (ALIF) utilizing a modular interbody device.Overview of LiteratureThough multiple anterior lumbar interbody techniques have proven successful in promoting bony fusion, postoperative subsidence remains a frequently reported phenomenon.MethodsForty-three consecutive patients underwent ALIF with (n=30) or without (n=11) supplemental instrumentation. Two patients underwent ALIF to treat failed posterior instrumented fusion. The primary outcome measure was presence of fusion as assessed by computed tomography. Secondary outcome measures were lordosis, intervertebral lordotic angle (ILA), disc height, subsidence, Bridwell fusion grade, technical complications and pain score. Interobserver reliability of radiographic outcome measures was calculated.ResultsForty-three patients underwent ALIF of 73 motion segments. ILA and disc height increased over baseline, and this persisted through final follow-up (p4 mm occurred in 12% of patients. There were eight surgical complications (19%): one major (reoperation for nonunion/progressive subsidence) and seven minor (five subsidence, two malposition).ConclusionsThe use of a modular interbody device for ALIF resulted in a high rate of radiographic fusion and a low rate of subsidence. The large endplate and modular design of the device may contribute to a low rate of subsidence as well as maintenance of ILA and lordosis. Previously reported quantitative radiographic outcome measures were found to be more reliable than qualitative or categorical measures.

Background: Spinal fusion surgery has become one of the most common spinal procedures during the recent years. Searching for an optimum structural stability of the vertebral interspace, surgical implants which can be inserted via a posterior lumbar interbody fusion (PLIF) approach have been enhanced recently.Objective: Evaluation of safety and efficacy of a novel PLIF polyetheretherketone (PEEK) interbody cage (TWIST) with an impactionless insertion technique.Methods: Surgical outcome in 15 patients treated with the new system were observed preoperatively, one and three years after surgery using the Oswestry Disability Index (ODI), a Visual Analogue Scale (VAS) for pain and radiological outcome analysis of fusion success.Results: Fifteen patients (7 female, 8 male) were included in the test series. After three years ODI and VAS were significantly improved. The pain intensity was reduced by more than 75% after one year and after 3 years, pain intensity was about 60% below the initial situation. The Oswestry values (ODI) improved significantly in all patients after 3 years. The fusion evaluation showed a fusion success in 87% of the patients.Conclusion: The clinical and radiological results of this first series give a positive standing and important information on the efficacy and safety over 3 years. The follow-up checks with imaging techniques showed that the fusions were very successful and functional outcome as well as pain reduction were increased. [ABSTRACT FROM AUTHOR]

This study identifies the rate of pseudarthrosis following surgical debridement for deep lumbar spine surgical site infection and identify associated risk factors. Patients who underwent index lumbar fusion surgery from 2013 to 2014 were included if they met the following criteria: 1) age >18 years, 2) had debridement of deep lumbar SSI, and had 3) lumbar spine AP, lateral and flexion/extension X-rays and computed tomography (CT) at 12 months or greater postoperatively. Criteria for fusion included 1) solid posterolateral, facet, or disk space bridging bone, 2) no translational or angular motion on flexion/extension X-rays, and 3) intact posterior hardware without evidence of screw lucency or breakage. Twenty-five patients (age 63.2 ± 12.6 years, 10 male) involving 58 spinal levels met inclusion criteria. They underwent fusion at a mean of 2.32 [range 1–4] spinal levels. Sixteen (64.0%) patients received interbody grafts at a total of 34 (58.6%) spinal levels. All underwent surgical debridement with removal of all non-incorporated posterior bone graft and devascularized tissue. At one-year postoperatively, (56%) patients and 30 (52%) spinal levels demonstrated radiographic evidence of successful fusion. Interbody cage during initial fusion was significantly associated with successful arthrodesis at follow-up ( p = 0.017). There is a high rate of pseudoarthrosis in 44% of patients (48% of levels) undergoing lumbar fusion surgery complicated by SSI requiring debridement. Use of interbody cage during initial fusion was significantly associated with higher rate of arthrodesis. [ABSTRACT FROM AUTHOR]

Introduction: Anterior cervical discectomy and fusion (ACDF) has been considered as the gold standard surgical treatment for cervical degenerative pathologies. Some surgeons tend to use larger-sized interbody cages during ACDF to restore the index intervertebral disc height, hence, this study evaluated the effect of larger-sized interbody cages on the cervical spine with ACDF under both static and cyclic loading. Method: Twenty pre-operative personalized poro-hyperelastic finite element (FE) models were developed. ACDF post-operative models were then constructed and four clinical scenarios (i.e., 1) No-distraction; 2) 1 mm distraction; 3) 2 mm distraction; and 4) 3 mm distraction) were predicted for each patient. The biomechanical responses at adjacent spinal levels were studied subject to static and cyclic loading. Non-parametric Friedman statistical comparative tests were performed and the p values less than 0.05 were reflected as significant. Results: The calculated intersegmental range of motion (ROM) and intradiscal pressure (IDP) from 20 pre-operative FE models were within the overall ranges compared to the available data from literature. Under static loading, greater ROM, IDP, facet joint force (FJF) values were detected post ACDF, as compared with pre-op. Over-distraction induced significantly higher IDP and FJF in both upper and lower adjacent levels in extension. Higher annulus fibrosus stress and strain values, and increased disc height and fluid loss at the adjacent levels were observed in ACDF group which significantly increased for over-distraction groups. Discussion: it was concluded that using larger-sized interbody cages (the height of ≥2 mm of the index disc height) can result in remarkable variations in biomechanical responses of adjacent levels, which may indicate as risk factor for adjacent segment disease. The results of this comprehensive FE investigation using personalized modeling technique highlight the importance of selecting the appropriate height of interbody cage in ACDF surgery., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Cheng, Chiu, Chen, Niu and Nikkhoo.)

Objective: To analyze the clinical and radiographic results following the use of integrated intervertebral implant in patients with cervical spine degenerative disease. Background: Though excellent results have been reported following anterior cervical discectomy and fusion using iliac crest autograft/allograft with plating, the morbidity associated with autograft harvest and small chances of complications with plating always exists. Recently, there has been development of a cervical stand-alone cage with integrated fixation for cervical fusion and stabilization with a possible low morbidity and optimal clinical outcome. Materials and Methods: A retrospective study of 16 patients who underwent anterior cervical discectomy and fusion using the integrated intervertebral device was performed. Intra-operative parameters, clinical features [Neck Disability Index (NDI), visual analog scale (VAS) score for neck/arm pain], and presence or absence of dysphagia was recorded. Radiographs were evaluated for assessment of implant failure and fusion. Results: Mean age of patients was 54 years (range: 38-84 years) with male: female ratio of 1:3. Follow-up ranged from 6 to 12 months (mean: 10 months). In the early postoperative period, 2 of the 15 patients (13%) patients had mild dysphagia that resolved during follow-up with no patient having complaints of dysphagia at 3-month follow-up. One of the patients with diffuse idiopathic skeletal hyperostosis (DISH) and severe preoperative dysphagia had significant improvement in swallowing function at 3-month follow-up that was stable at 1-year follow-up. There was no evidence of implant failure, with fusion occurring in 95% (19/20) of operated levels. Analysis of follow-up VAS and NDI scores showed significant reduction in VAS score for neck pain (P < 0.019), radicular arm pain (P < 0.003), and NDI score (P < 0.007) in 77, 92, and 77% of patients, respectively, at a mean follow-up of 10 months (6-12 months). Conclusions: Our preliminary results with the use of this cervical stand-alone anterior fusion device with integrated screw fixation show its efficacy in anterior cervical decompression and fusion with stabilization with optimal clinical and radiographic outcome. Lower chances of dysphagia with no device-related complications are appealing, which needs to be verified in larger studies.

There are several complications associated with lumbar interbody fusion surgery however, pseudarthrosis (non-union) presents a multifaceted challenge in the postoperative management of the patient. Rates of pseudarthrosis range from 3 to 20 % in patients with healthy bone and 20 to 30 % in patients with osteoporosis. The current methods in post-operative follow-up - radiographs and CT, have high false positive rates and poor agreement between them. The aim of this study was to develop and test a proof-of-concept load-sensing interbody cage that may be used to monitor fusion progression. Piezoresistive pressure sensors were calibrated and embedded within a polyether ether ketone (PEEK) interbody cage. Silicone and poly (methyl methacrylate) (PMMA) were inserted in the graft regions to simulate early and solid fusion. The load-sensing cage was subjected to distributed and eccentric compressive loads up to 900 N between synthetic lumbar vertebral bodies. Under maximum load, the anterior sensors recorded a 56–58 % reduction in pressure in the full fusion state compared to early fusion. Lateral regions measured a 36–37 % stress reduction while the central location reduced by 45 %. The two graft states were distinguishable by sensor-recorded pressure at lower loads. The sensors more effectively detected left and right eccentric loads compared to anterior and posterior. Further, the load-sensing cage was able to detect changes in endplate stiffness. The proof-of-concept 'smart' cage could detect differences in fusion state, endplate stiffness, and loading conditions in this in vitro experimental setup. [ABSTRACT FROM AUTHOR]

Introduction: Cage impactions (CI) of Oblique Lumbar Interbody Fusion (OLIF) appear to be a frequent mechanical complication with a potential functional impact., Objectives: To determine the rate of CI occurrence, their risk factors and clinical implications in the case of combined single-level arthrodesis., Method: A retrospective analysis of prospectively collected data was performed. All our patients with degenerative spondylolisthesis initially underwent OLIF combined with pedicle screw fixation (PSF). Intraoperative control with an image intensifier and a standard radiograph in the immediate postoperative period made it possible to assess the occurrence of CI, depending on the position of the implant. Secondary subsidence was sought on the standing radiological examination using EOS biplanar radiography during follow-up. The pelvic parameters were analyzed, as well as the occurrence of bone fusion. The clinical evaluation was made at≥1 year, by the Oswestry Disability Index (ODI), the walking distance (WD) and the Visual Analogue Scale (VAS)., Results: In all, 130 patients out of the 131 included were analyzed. A CI occurred in 25.3% (n=33) of cases and of these, 94% (n=32) occurred intraoperatively. Postmenopausal women had more CI with an odds ratio (OR) of 5.8 (P=0.034). The "CI" group had a 9.5% lower ODI score than the "non-CI" group (P=0.0040), but both provided excellent ODI gains of 30.8±16 and 32.9±15.5% (P<0.0001). An "anterior" position of the implant allowed a greater gain in lumbar lordosis (P<0.001) but was associated with greater CI occurrence (P<0.001), with an OR of 6.75 (P=0.0018)., Conclusion: The occurrence of intraoperative cage impaction is a frequent event when performing OLIF. Postmenopausal women have an approximately 6 times greater risk of impaction than men, and patients with an "anterior" implant placement have a 7 times greater risk than with central placement. The negative impact of cage impactions on the clinical score (ODI) was significant after one year of follow-up., Level of Evidence: IV, non-comparative cohort study., (Copyright © 2022. Published by Elsevier Masson SAS.)

Background: Pain and disability due to age-related spinal disorders are increasing due to a more active population placing greater demands on their musculoskeletal system. For patients requiring surgery, spinal fusion is typically indicated. Interbody fusion cages improve fusion rates and restore lordosis, disc height, and foraminal height. Static cages are offered in multiple conformations to account for anatomic variability; however, they have issues related to implant subsidence and loss of lordosis. Expandable cages were developed to address these drawbacks., Methods: Patients treated with either static or expandable transforaminal lumbar interbody fusion devices (ProLift ® Expandable Spacer System) for the treatment of spondylolisthesis, degenerative disc disease, spinal stenosis, disc herniation, or degenerative scoliosis at L4-L5 or L5-S1 were chosen from retrospective data. Outcomes included radiographic and spinopelvic changes, patient-reported outcomes, and incidence of non-union and revision surgery., Results: One hundred patients were included (Static: 50; Expandable: 50). Demographics between groups were similar, with some differences in comorbidities and spinal disease diagnosis. Radiographically, changes in disc height, foraminal height, and lordosis were significantly improved in the Expandable group up to 2 years (P<0.001). Improvements in patient reported outcomes were more favorable in the Expandable group., Conclusions: In patients who underwent transforaminal lumbar spinal fusion via minimally invasive surgery, the Expandable device group demonstrated significantly improved radiographic and patient reported outcomes compared to a static cage over 2 years., Competing Interests: Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jss.amegroups.com/article/view/10.21037/jss-22-55/coif). DWK receives royalties, consulting fees, or other support from the following entities: Medicrea, Precision Spine, NVision Spine, Surgalign, SeaSpine, Spinal Elements, Orthofix/Stryker, Arthrex Spine, and CoreLink; DWK also has patents planned, issued, or pending for Modular Pedicle Screw Design System, SI joint implant design, and 3D printed PEEK interbody implants. EIW, LCS, and CV have received payment for independent medical writing and data analysis from Life Spine. The other author has no conflicts of interest to declare., (2023 Journal of Spine Surgery. All rights reserved.)

Finite element analysis (FEA) is a widely used tool in a variety of industries and research endeavors. With its application to spine biomechanics, FEA has contributed to a better understanding of the spine, its components, and its behavior in physiological and pathological conditions, as well as assisting in the design and application of spinal instrumentation, particularly spinal interbody cages (ICs). IC is a highly effective instrumentation for achieving spinal fusion that has been used to treat a variety of spinal disorders, including degenerative disc disease, trauma, tumor reconstruction, and scoliosis. The application of FEA lets new designs be thoroughly "tested" before a cage is even manufactured, allowing bio-mechanical responses and spinal fusion processes that cannot easily be experimented upon in vivo to be examined and "diagnosis" to be performed, which is an important addition to clinical and in vitro experimental studies. This paper reviews the recent progress of FEA in spinal ICs over the last six years. It demonstrates how modeling can aid in evaluating the biomechanical response of cage materials, cage design, and fixation devices, understanding bone formation mechanisms, comparing the benefits of various fusion techniques, and investigating the impact of pathological structures. It also summarizes the various limitations brought about by modeling simplification and looks forward to the significant advancement of spine FEA research as computing efficiency and software capabilities increase. In conclusion, in such a fast-paced field, the FEA is critical for spinal IC studies. It helps in quantitatively and visually demonstrating the cage characteristics after implanting, lowering surgeons' learning costs for new cage products, and probably assisting them in determining the best IC for patients., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Wang and Wu.)

Since the late 1980s, spinal interbody cages ( ICs) have been used to aid bone fusion in a variety of spinal disorders. Utilized to restore intervertebral height, enable bone graft containment for arthrodesis, and restore anterior column biomechanical stability, ICs have since evolved to become a highly successful means of achieving fusion, being associated with less postoperative pain, shorter hospital stay, fewer complications and higher rates of fusion when than bone graft only spinal fusion. IC design and materials have changed considerably over the past two decades. The threaded titanium-alloy cylindrical screw cages, typically filled with autologous bone graft, of the mid-1990s achieved greater fusion rates than bone grafts and non-threaded cages. Threaded screw cages, however, were soon found to be less stable in extension and flexion; additionally, they had a high incidence of cage subsidence. As of the early 2000s, non-threaded box-shaped titanium or polyether ether ketone IC designs have become increasingly more common. This modern design continues to achieve greater cage stability in flexion, axial rotation and bending. However, cage stability and subsidence, bone fusion rates and surgical complications still require optimization. Thus, this review provides an update of recent research findings relevant to ICs over the past 3 years, highlighting trends in optimization of cage design, materials, alternatives to bone grafts, and coatings that may enhance fusion. [ABSTRACT FROM AUTHOR]

Objective Anterior cervical discectomy and fusion is the most commonly employed surgical technique for treating cervical spondylosis. Although autologous bone grafts are considered the gold standard in achieving fusion, associated short- and long-term morbidities have led to a search for alternative materials. These have included carbon-fiber, titanium alloy (Ti) and ceramic and polyetheretherketone ( PEEK) based implants. Recent attempts to optimize cage implants through using composite designs have combined Ti and PEEK. However, there are few published reports on the clinical and radiological outcomes of commercially available composite cages. Our study aimed to provide and evaluate initial outcomes of a composite Ti/ PEEK cage. Methods In this prospective single senior surgeon cohort study, 31 consecutive patients underwent a modified Smith-Robinson technique under general anesthesia and relevant data were collected. The study patients were aged between 18 and 75 years and underwent surgery from November 2013 to May 2014. Indications for surgery included traumatic and degenerative cervical disease that was unsuitable for or unresponsive to conservative management. All cages were between 5 and 8 mm and packed with super critical fluid sterilized allograft and bone marrow aspirate before insertion. Patients were followed-up for a minimum of 12 months. Fusion was assessed using fine cut CT and anteroposterior and lateral radiographs. Clinical outcomes were measured using a Visual Analogue Scale, Neck Oswestry Disability Index and Patient's Satisfaction Index. Results Six of the original cohort were unavailable for adequate follow-up. The remaining 25 patients (17 men, 8 women; 33 operative levels) were observed for a mean of 14.6 months (range, 12-16 months). All operation levels were between C4 and C7. Single-level operations were performed in 19 patients and additional plating in 14 patients. A fusion rate of 96% was achieved. Patients in both plated and non-plated groups experienced statistically significant improvements; good to excellent outcomes being seen in 92% of patients. There was one complication, namely recurrent laryngeal nerve palsy, which had partially resolved at 6 months follow-up. Conclusion The present study shows that enhancement of PEEK cages with Ti endplates is a safe and effective treatment with the potential for early osseointegration and early radiological evidence of fusion. [ABSTRACT FROM AUTHOR]

Background: Selecting an interbody cage with appropriate height is one of the key steps in lumbar interbody fusion, and has an important impact on clinical efficacy. How to choose the appropriate height of the cage becomes one of the core problems of lumbar interbody fusion for spine surgeons. However, studies about objective selection criteria on interbody cage height was rare.Methods: One hundred fifty-seven patients with single segment lumbar degenerative diseases treated by TLIF surgery from January 2011 to July 2013 were retrospectively analyzed. Parameters analyzed included: gender, age, body height, clinical diagnosis, pathological segment location and the intervertebral height of pathological segment, pathological segment activity, the intervertebral height of the adjacent segments. And further to analyze the correlation between these parameters and interbody cage height. By measuring the intervertebral height of pathological segment and normal segment to calculate the regression equation of interbody cage height.Results: The average interbody cage height of male patients (12.38 ± 1.43) mm was significantly higher than female (11.62 ± 1.45) mm (p < 0.001). The L4-5 segment interbody cage height (12.11 ± 1.38) mm was significantly greater than the L5-S1 (11.25 ± 1.32) mm (p = 0.04). Body height, the intervertebral height of pathological segment, and the middle intervertebral heigh of upper adjacent segment were highly positively correlated to the interbody cage height. The range of interbody cage height used in transforaminal lumbar interbody fusion for Chinese patients with lumbar degenerative diseases was: L3-4 (11.28 ± 3.29) mm ~ (12.76 ± 2.40) mm, L4-5 (11.62 ± 2.89) mm ~ (13.18 ± 1.91) mm, L5-S1 (10.52 ± 2.22) mm ~ (11.90 ± 2.80) mm. The regression equation of interbody cage height was: interbody cage height = 11.123-0.563 * (gender) + 0.149 * (the middle intervertebral height of pathological segment).Conclusions: The selection of interbody cage height was influenced by sex, body height, pathological segment location, the intervertebral height of pathological segment and other factors. The interbody cage height for the lower lumbar spine mostly selected 11,12,13 mm, L3-4, L4-5 segment highly selective in general should not be less than 10 mm, and L5-S1 segments height was relatively small, usually not more than 13 mm. The interbody cage height might be selected based on the regression equation of interbody cage height. But, the regression equation maybe need to be verified in a prospective study. [ABSTRACT FROM AUTHOR]

Lumbar fusion often remains the last treatment option for various acute and chronic spinal conditions, including infectious and degenerative diseases. Placement of a cage in the intervertebral space has become a routine clinical treatment for spinal fusion surgery to provide sufficient biomechanical stability, which is required to achieve bony ingrowth of the implant. Routinely used cages for clinical application are made of titanium (Ti) or polyetheretherketone (PEEK). Ti has been used since the 1980s; however, its shortcomings, such as impaired radiographical opacity and higher elastic modulus compared to bone, have led to the development of PEEK cages, which are associated with reduced stress shielding as well as no radiographical artefacts. Since PEEK is bioinert, its osteointegration capacity is limited, which in turn enhances fibrotic tissue formation and peri-implant infections. To address shortcomings of both of these biomaterials, interdisciplinary teams have developed biodegradable cages. Rooted in promising preclinical large animal studies, a hollow cylindrical cage (Hydrosorb™) made of 70:30 poly- l -lactide-co-d, l -lactide acid (PLDLLA) was clinically studied. However, reduced bony integration and unfavourable long-term clinical outcomes prohibited its routine clinical application. More recently, scaffold-guided bone regeneration (SGBR) with application of highly porous biodegradable constructs is emerging. Advancements in additive manufacturing technology now allow the cage designs that match requirements, such as stiffness of surrounding tissues, while providing long-term biomechanical stability. A favourable clinical outcome has been observed in the treatment of various bone defects, particularly for 3D-printed composite scaffolds made of medical-grade polycaprolactone (mPCL) in combination with a ceramic filler material. Therefore, advanced cage design made of mPCL and ceramic may also carry initial high spinal forces up to the time of bony fusion and subsequently resorb without clinical side effects. Furthermore, surface modification of implants is an effective approach to simultaneously reduce microbial infection and improve tissue integration. We present a design concept for a scaffold surface which result in osteoconductive and antimicrobial properties that have the potential to achieve higher rates of fusion and less clinical complications. In this review, we explore the preclinical and clinical studies which used bioresorbable cages. Furthermore, we critically discuss the need for a cutting-edge research program that includes comprehensive preclinical in vitro and in vivo studies to enable successful translation from bench to bedside. We develop such a conceptual framework by examining the state-of-the-art literature and posing the questions that will guide this field in the coming years. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract Background Laboratory spinal biomechanical tests using human cadaveric or animal spines have limitations in terms of disease transmission, high sample variability, decay and fatigue during extended testing protocols. Therefore, a synthetic biomimetic spine model may be an acceptable substitute. The goal of current study is to evaluate the properties of a synthetic biomimetic spine model; also to assess the mechanical performance of lateral plating following lateral interbody fusion. Methods Three L3/4 synthetic spinal motion segments were examined using a validated pure moment testing system. Moments (±7.5 Nm) were applied in flexion‐extension (FE), lateral bending (LB) and axial rotation (AR) at 1Hz for total 10000 cycles in MTS Bionix. An additional test was performed 12 hours after 10000 cycles. A ±10 Nm cycle was also performed to allow provide comparison to the literature. For implantation evaluation, each model was tested in the 4 following conditions: 1) intact, 2) lateral cage alone, 3) lateral cage and plate 4) anterior cage and plate. Results were analysed using ANOVA with post‐hoc Tukey’s HSD test. Results Range of motion (ROM) exhibited logarithmic growth with cycle number (increases of 16%, 37.5% and 24.3% in AR, FE and LB respectively). No signification difference (p > 0.1) was detected between 4 cycles, 10000 cycles and 12 hour rest stages. All measured parameters were comparable to that of reported cadaveric values. The ROM for a lateral cage and plate construct was not significantly different to the anterior lumbar interbody construct for FE (p = 1.00), LB (p = 0.995) and AR (p = 0.837). Conclusions Based on anatomical and biomechanical similarities, the synthetic spine tested here provides a reasonable model to represent the human lumbar spine. Repeated testing did not dramatically alter biomechanics which may allow non‐destructive testing between many different procedures and devices without the worry of carry over effects. Small intra‐specimen variability and lack of biohazard makes this an attractive alternative for in vitro spine biomechanical testing. It also proved an acceptable surrogate for biomechanical testing, confirming that a lateral lumbar interbody cage and plate construct reduces ROM to a similar degree as anterior lumbar interbody cage and plate constructs.

Background: Anterior lumbar interbody fusion (ALIF) has been performed for many years. Often, posterior supplemental fixation has been used to provide additional stability to the operated segment. Interbody implants have evolved to incorporate unique designs, polyetheretherketone, integrated screws, and surface texture. With these changes, the need for supplemental posterior fixation has been debated. The purpose of this study was to evaluate the clinical outcome of stand-alone ALIF., Methods: A surgery log was reviewed to identify the consecutive series of 58 patients undergoing ALIF using a STALIF stand-alone cage from March 2011 (first case) to December 2018 (minimum 24 months postoperative) with a mean follow-up of 30.6 months. All patients were treated for symptomatic degenerative conditions. Charts were reviewed to collect general patient information, operative data, and patient-reported outcomes, including the Oswestry Disability Index (ODI), visual analog scales (VAS) separately assessing back pain and leg pain, and re-operations. For patients who were not seen recently in clinic for follow-up, current outcome data were collected through mailings., Results: The mean operative blood loss was 52.1 mL. There was a statistically significant improvement in mean ODI scores from 41.7 preoperatively to 21.0 at follow-up ( P < 0.01). There was also significant improvement ( P < 0.01) in VAS back pain (6.0-2.5) and leg pain (4.1-1.3). Subsequent surgery was performed on 9 patients. Reasons for re-operation were pseudoarthrosis ( n = 3), progressive cage subsidence ( n = 1), foraminal stenosis at the index level ( n = 1), metal allergy reaction ( n = 2), adjacent segment degeneration ( n = 1), and ongoing pain ( n = 1). There were no cases of device failure, vertebral body fracture, or screws backing out of the implant., Discussion: Stand-alone ALIF was associated with statistically significant improvements in ODI scores, back pain, and leg pain. The re-operation rate for clear pseudoarthrosis or cage subsidence was 6.8%. These results support that stand-alone ALIF produces good outcomes in patients treated for symptomatic disc degeneration while avoiding the use of posterior fixation and its complication risk and cost., Clinical Relevance: The results of this study support that stand-alone ALIF is a viable procedure for the treatment of symptomatic disc degeneration unresponsive in patients who have failed nonoperative care and who do not have specific indications for supplemental posterior instrumentation., Competing Interests: Conflicts and Disclosures: Richard Guyer reports consulting fees from Centinel, Aesculap, NuVasive, and Orthofix, and stock or stock options for Alphatec and Stryker Spine. Jack Zigler reports consulting fees from Centinel Spine, Aesculap Spine, NuVasive, and Orthofix; leadership or fiduciary role for AO Spine Technical Committee; and stock options in VBIC. Scott Blumenthal reports royalties or licenses from Aesculap; consulting fees from Orthofix, Aesculap, NeospineCen, Bayless Medical, DeGen, Centinel, and Zimmer; payment or honoraria from Bayless Medical, NuVasive, and Aesculap; stock or stock options from Centinel Spine and Fziomed; and other financial or nonfinancial interests in Aesculap and Fziomed (Scientific Advisory Board) and Aesculap (Device or biologic distribution group—physician-owned distribution). Jessica Shellock reports consulting fees and payment or honoraria from Centinel Spine for educational activities. Donna Ohnmeiss reports no disclosures., (This manuscript is generously published free of charge by ISASS, the International Society for the Advancement of Spine Surgery. Copyright © 2023 ISASS. To see more or order reprints or permissions, see http://ijssurgery.com.)

Introduction: The plate fixation for anterior cervical discectomy and fusion (ACDF) has become increasingly widespread for facilitating early mobilization and improving fusion rate. However, apart from multilevel operations, there is still some controversy over its use for single-level ACDF. This retrospective study has compared the reoperation rates after single-level ACDFs performed at our institution between the procedures with and without plate fixation., Methods: This retrospective study included a total of 131 patients with???1-year of follow-up after a single-level ACDF, consisting of 100 patients without plating (conventional ACDF) and 31 patients with plate fixation (plated ACDF)., Results: Eleven patients (8.4% of all patients):four conventional ACDFs (4% of the conventional ACDFs) and seven plated ACDFs (22.6% of the plated ACDFs), had reoperation surgeries. The incidence of reoperation was significantly higher in the plated ACDFs than in the conventional ACDFs (P=0.0037). The log-rank test revealed a significant difference (P=0.00003) in 5-year reoperation-free survival rates between the conventional (96.9%) and the plated groups (68.3%)., Conclusion: Anterior cervical plating may have a negative impact on the adjacent segment integrity, resulting in an increased reoperation rate after a single-level ACDF at relatively shorter postoperative time points. J. Med. Invest. 70 : 334-342, August, 2023.

Objective: The objective of this study was to evaluate patient and surgical factors that predict increased overall lumbar lordosis (LL) and segmental lordosis correction following a minimally invasive lateral lumbar interbody fusion (LLIF) procedure., Methods: A retrospective review was conducted of all patients who underwent one- or two-level LLIF. Preoperative, initial postoperative, and 6-month postoperative measurements of LL, segmental lordosis, anterior disc height, and posterior disc height were collected from standing lateral radiographs for each patient. Cage placement was measured utilizing the center point ratio (CPR) on immediate postoperative radiographs. Spearman correlations were used to assess associations between cage lordosis and radiographic parameters. Multivariate linear regression was performed to assess independent predictors of outcomes., Results: A total of 106 levels in 78 unique patients were included. Most procedures involved fusion of one level (n = 50, 64.1%), most commonly L3-4 (46.2%). Despite no differences in baseline segmental lordosis, patients with anteriorly or centrally placed cages experienced the greatest segmental lordosis correction immediately (mean anterior 4.81° and central 4.46° vs posterior 2.47°, p = 0.0315) and at 6 months postoperatively, and patients with anteriorly placed cages had greater overall lordosis correction postoperatively (mean 6.30°, p = 0.0338). At the 6-month follow-up, patients with anteriorly placed cages experienced the greatest increase in anterior disc height (mean anterior 6.24 mm vs posterior 3.69 mm, p = 0.0122). Cages placed more posteriorly increased the change in posterior disc height postoperatively (mean posterior 4.91 mm vs anterior 1.80 mm, p = 0.0001) and at 6 months (mean posterior 4.18 mm vs anterior 2.06 mm, p = 0.0255). There were no correlations between cage lordotic angle and outcomes. On multivariate regression, anterior cage placement predicted greater 6-month improvement in segmental lordosis, while posterior placement predicted greater 6-month improvement in posterior disc height. Percutaneous screw placement, cage lordotic angle, and cage height did not independently predict any radiographic outcomes., Conclusions: LLIF procedures reliably improve LL and increase intervertebral disc space. Anterior cage placement improves the lordosis angle greater than posterior placement, which better corrects sagittal alignment, but there is still a significant improvement in lordosis even with a posteriorly placed cage. Posterior cage placement provides greater restoration in posterior disc space height, maximizing indirect decompression, but even the anteriorly placed cages provided indirect decompression. Cage parameters including cage height, lordosis angle, and material do not impact radiographic improvement.

Purpose: To evaluate a radiological and clinical difference between the curvilinear type cages compared to the straight type cages for the restoration of lumbopelvic sagittal alignment and its maintenance after transforaminal lumbar interbody fusion (TLIF) procedure.Methods: 68 patients who underwent single-level TLIF using either the straight type or curvilinear type cage were retrospectively reviewed. Assessment of the lumbopelvic parameters and the height of disc space was performed before surgery as well as 2 days, 6 and 12 months after surgery. Clinical outcome was assessed using VAS and ODI.Results: The curvilinear type cages were positioned more anteriorly than the straight type. Restoration of the segmental lordosis (SL) in the curvilinear group was significantly greater than the straight group and at 12 months of follow-up, the straight group showed greater decrease in the disc height than the curvilinear group. The straight group failed to show improvement of lumbar lordosis (LL), while the curvilinear group showed significant restoration of LL and could maintain it to the 6 months of follow-up. In both groups, pelvic tilt was significantly decreased and it lasted to 6 months in the straight group; whereas in the curvilinear group, it was maintained to the last follow-up of 12 months. There were no significant differences between the two groups in mean VAS and ODI score over the follow-up period.Conclusions: This study demonstrates that the curvilinear type cage is superior to the straight type cage in improving the SL and maintaining both the restored lumbopelvic parameters and elevated disc height. These results could be attributable to the anterior position of the curvilinear cage which permits easy restoration of segmental lordosis and less sinking of cages. [ABSTRACT FROM AUTHOR]

Background context Transforaminal lumbar interbody fusion (TLIF) is increasingly popular for the surgical treatment of degenerative lumbar disease. The optimal construct for segmental stability remains unknown. Purpose To compare the stability of fusion constructs using standard (C) and crescent-shaped (CC) polyetheretherketone TLIF cages with unilateral (UPS) or bilateral (BPS) posterior instrumentation. Study design Five TLIF fusion constructs were compared using finite element (FE) analysis. Methods A previously validated L3–L5 FE model was modified to simulate decompression and fusion at L4–L5. This model was used to analyze the biomechanics of various unilateral and bilateral TLIF constructs. The inferior surface of the L5 vertebra remained immobilized throughout the load simulation, and a bending moment of 10 Nm was applied on the L3 vertebra to recreate flexion, extension, lateral bending, and axial rotation. Various biomechanical parameters were evaluated for intact and implanted models in all loading planes. Results All reconstructive conditions displayed decreased motion at L4–L5. Bilateral posterior fixation conferred greater stability when compared with unilateral fixation in left lateral bending. More than 50% of intact motion remained in the left lateral bending with unilateral posterior fixation compared with less than 10% when bilateral pedicle screw fixation was used. Posterior implant stresses for unilateral fixation were six times greater in flexion and up to four times greater in left lateral bending compared with bilateral fixation. No effects on segmental stability or posterior implant stresses were found. An obliquely-placed, single standard cage generated the lowest cage-end plate stress. Conclusions Transforaminal lumbar interbody fusion augmentation with bilateral posterior fixation increases fusion construct stability and decreases posterior instrumentation stress. The shape or number of interbody implants does not appear to impact the segmental stability when bilateral pedicle screws are used. Increased posterior instrumentation stresses were observed in all loading modes with unilateral pedicle screw/rod fixation, which may theoretically accelerate implant loosening or increase the risk of construct failure. [ABSTRACT FROM AUTHOR]

Study design: A retrospective review Purpose: This study was designed to compare postoperative changes in neural foramen between transforaminal lumbar interbody fusion (TLIF) and posterior lumbar interbody fusion (PLIF). Methods: A retrospective analysis of 67 patients was compared to the change of neural foraminal morphometry of the two techniques. 33 patients (40 levels) had TLIF and 34 patients (39 levels) had PLIF. The two groups had similar demographic profiles. Radiological parameters including anterior and posterior disc height, foraminal height (FH), and segmental Cobb angle (SCA) were measured by sagittally reconstructed computed tomography images before and after surgery. Cage position was designated as contralateral, middle, and ipsilateral in the TLIF group. Surgical results were assessed by Odom criteria, visual analog scale (VAS), and Oswestry disability index (ODI) scores. Results: The TLIF and PLIF group showed no bilateral difference in FH. The TLIF group had increased contralateral SCA compared to the ipsilateral side postoperatively. FH differed according to cage position in the TLIF group. When a cage was inserted deeply into the contralateral side, contralateral FH increased significantly. However, when a cage was inserted into the ipsilateral side, contralateral FH decreased significantly. Back pain was significantly lower in the TLIF group at 1 and 6 months than in the PLIF group. However, ODI and Odom scale scores were not different between the groups. Conclusions: TLIF may induce uneven changes in foraminal morphometry. Cage position may be the major determinant of this result. [ABSTRACT FROM AUTHOR]