Cage Position Research Articles

Analysis of factors impacting inter-body fusion cage subsidence following an oblique lateral interbody fusion (OLIF) stand-alone procedure

Background Lumbar oblique lateral interbody fusion (OLIF stand-alone) procedures have become a common treatment for various spinal conditions, including spinal stenosis and spondylolisthesis. However, cage subsidence following OLIF stand-alone procedures is a significant concern that can compromise the surgical outcomes. Objective To investigate the occurrence of cage subsidence following OLIF procedures and identify the relevant factors influencing cage subsidence. Method A retrospective analysis was conducted on 86 patients who underwent elective OLIF stand-alone procedures at the Affiliated People's Hospital of Qingdao University between 2019 and 2023. Patients were categorized into two groups based on disc height (DH) subsidence: cage non-subsidence group (< 2 mm) and cage subsidence group (> 2 mm). General and imaging data were collected pre-surgery, post-surgery, and at six months follow-up. Single-factor analysis identified factors influencing cage subsidence, followed by multi-factor regression analysis on these variables to determine their impact. Results When the degree of DH subsidence in the last follow-up (M6) was evaluated, among the 86 patients (102 segments), 26 patients (25.49%) fulfilled the criteria for cage subsidence. Factors with clinical and statistical significance in the single-factor analysis were incorporated into the multi-factor analysis, and it was found that the mean CT value of the concerned segment, multifidus area, and severe multifidus atrophy were relevant risk factors for cage subsidence; the protective factors for cage subsidence were degree III zygapophyseal joint degeneration, posterior cage position, and end-plate inflammation sclerosis (P < 0.05). Conclusion Surgeons should be cautious in preoperatively identifying patients at risk of cage subsidence, particularly those with a low mean CT value of the concerned segment or severe multifidus atrophy. During surgery, selecting a cage of adequate length to span the epiphyseal ring and align with the original DH can help protect paravertebral muscles from iatrogenic injury and reduce the risk of cage subsidence.

The effects of cage on endplate collapse after stand-alone OLIF: based on finite element analysis and in vitro mechanics experiments.

Lumbar degenerative diseases are an important factor in disability worldwide, and they are also common among the elderly population. Stand-Alone Oblique Lumbar Interbody Fusion (Stand-Alone OLIF) is a novel surgical approach for treating lumbar degenerative diseases. However, long-term follow-up after surgery has revealed the risk of endplate collapse associated with Stand-Alone OLIF procedures. This study aimed to investigate the effect of the cage factor on endplate collapse after Stand-Alone OLIF. Finite element (FE) models and calf lumbar functional units were established separately and used to simulate Stand-Alone OLIF surgery. On the L5 endplate of the FE model and the calf lumbar functional unit, 12 cage positions from anterior to posterior, 16 cage inclination angles from 0° to 15°, and 4 cage heights were selected to simulate surgical models with different cage positions. Compression loads of 400N were applied to the upper surface of the superior vertebral body of the cage, and 10Nm torques in four directions were used to simulate four different physiological movements of the lumbar spine: flexion, extension, lateral curvature and torsion, in order to compare the range of motion of the surgical segment and the endplate stress. When the cage is placed closer to the anterior and posterior edges of the endplate and when the height of the cage exceeds 12mm, the intervertebral range of motion at the surgical segment is greater and the stress on the endplate is higher during various lumbar spine activities. When the cage is inclined at an angle within 15°, there are no significant differences in the corresponding endplate stress and the range of motion. For Stand-Alone OLIF surgery, inserting the cage in the central anterior-posterior position of the intervertebral space and selecting a cage with a height not exceeding 12mm can reduce the stress on the endplate after surgery, which is more conducive to the stability of the lumbar spine postoperatively and reduces the risk of postoperative endplate collapse. The inclination angle of the cage placement does not significantly affect postoperative endplate stress or lumbar stability.

Experimental study on the axial compressive performance of prefabricated steel reinforcement cage‐cast‐in‐situ concrete column with an innovative sleeve

AbstractBased on the ribbed rebar with direct rolling thread and hot‐forged double‐lock nut mechanical sleeve connection technology, a construction method for prefabricated reinforcement cage‐cast‐in‐situ concrete (PRC‐CISC) column using this connection is proposed. This method contributes to improving the construction efficiency and engineering quality of reinforced concrete columns. Four PRC‐CISC columns and four control specimens were designed with rebar strength, rebar ratio, and rebar connection method as analysis parameters. A comparative study was conducted on their failure modes, axial compression performance, and rebar connector (coupler) working mechanisms. The results show that compared to the control specimens, the crack morphology of PRC‐CISC columns has no significant difference. However, the apparent yielding position of the reinforcement cage may occur on the cross‐sections where the rebar is located on both sides of the sleeve. The partial carrying capacity of the specimens may increase or decrease (≤4.08%), and the maximum deviation of the displacement ductility coefficient is 0.14, indicating that its strength and deformation differences are relatively small. Furthermore, the study reveals the random migration behavior of the control section of PRC‐CISC columns. When the specimens fail, the strain of the sleeve is significantly smaller than the rebar strain in the control specimens, while the concrete strain shows no significant difference. This is because the increase in the effective area of the sleeve shares the vertical load it bears. Finally, based on the test results, sleeve constitutive relationship, and random migration behavior of the control section, the compressive load capacity range of the positive section of PRC‐CISC columns is proposed. This method can effectively estimate their actual carrying capacity and is consistent with the force characteristics.

Influence of a Lordotic Cage Profile on Global and Segmental Lordosis in the Context of Lumbar TLIF Surgeries: A Retrospective Radiological Analysis.

Background/Objectives: Cage implantation decompresses neural elements, stabilizes segments, and promotes fusion, with sagittal balance influenced by cage size, geometry, and position. This retrospective study compared the effects of lumbar interbody cages with 10° and 15° lordotic angles on global and segmental lordosis in patients undergoing transforaminal lumbar interbody fusion (TLIF). Methods: Data from 215 patients who underwent 259 TLIF procedures between 2018 and 2022 were analyzed. All the surgeries were performed by a single senior orthopedic spine surgeon, and cages were selected by the surgeon based on patients' clinical and anatomical factors. Radiographic assessments included measurements of global and segmental lordosis. Results: Patients who received 15° cages demonstrated significantly greater segmental lordosis compared to those who received 10° cages in both bisegmental and monosegmental procedures (p < 0.001). While the global lordosis in the 10°-cage group remained unchanged postoperatively (p = 0.687), bisegmental procedures showed a small but statistically significant increase (p = 0.035). Moreover, global lordosis did not significantly differ between the 10°- and 15°-cage groups. Conclusions: Cage geometry significantly influenced segmental lordosis, with 15° cages achieving overall more superior radiographic results compared to 10° cages. However, global lordosis was unaffected by cage angle, thereby highlighting the multifaceted nature of factors that influence overall spinal alignment. These findings provide valuable insights into lumbar spine surgery, thus emphasizing the need for comprehensive preoperative planning and consideration of individual patient characteristics.

The influence of lumbar vertebra and cage related factors on cage-endplate contact after lumbar interbody fusion: An in-vitro experimental study

Lumbar interbody fusion (LIF) using interbody cages is an established treatment for lumbar degenerative disc disease, but fusion results are known to be affected by risk factors such as bone mineral density (BMD), endplate geometry and cage position. At present, direct measurement of endplate-cage contact variables that affect LIF have not been fully identified. The aim of this study was to use cadaveric experiments to investigate the dependency between BMD, endplate geometry, cage parameters like type, orientation, position, and contact variables like stress and area. One vertebral body specimen from each of the five lumbar positions was harvested from five male donors. The lower half of each vertebra was potted and placed in a material testing machine (Instron 8874). A spinal cage was clamped to the machine then lowered to bring it into contact against the superior endplate. A lockable ball-joint was used to rotate the cage such that its inferior surface was congruent with the local endplate surface. A pressure sensor (Tekscan) was placed between the cage and endplate to record contact area and the peak and average contact pressures. Axial compression of 400 N was performed for five positions using a straight cage, and in one anterior position using a curved cage. The linear mixed model was utilised to perform data analyses for experimental results with statistical significance set at p < 0.05. The results indicated two trends toward significance for contact area, one for volumetric BMD (vBMD) of the vertebra (p = 0.081), and another for predicted contact area (p = 0.057). Peak contact pressure correlated significantly with vBMD (p = 0.041), and there was a trend between average contact pressure and lateral position of cage (p = 0.051). In addition, predicted contact area correlated significantly with cage orientation (p < 0.001). These results indicated that high vBMD of vertebra and a medially positioned cage led to higher contact pressures. Logically, low vBMD of vertebra and transverse cage orientation increased the contact area between the cage and endplate. In conclusion, the study identified significant influence of vBMD of vertebra, cage position and orientation on cage-endplate contact which may help to inform cage selection and design for LIF.

Self-Assembly Determines Sign of Seebeck Coefficient in Tunneling Junctions Comprising Monolayers and Bilayers of Fullerenes.

We measured the Seebeck coefficient for junctions comprising self-assembled monolayers and bilayers of the fullerene moiety PTEG-1 on Au using eutectic Ga-In in a controlled anhydrous atmosphere by varying the temperature gradient from -12 to 12 °C, observing a linear response in thermovoltage across the range. The sign of the coefficient was positive for monolayers of PTEG-1, (195 ± 8) μV K-1 and negative for bilayers of PTEG-1, (-209 ± 14) μV K-1, indicating a change from HOMO-mediated to LUMO-mediated charge-transport. Charge-transport is nonresonant tunneling for both monolayers and bilayers, but the former self-assembles with the fullerene cage at the chemisorbed interface while the latter includes a fullerene cage at the physisorbed interface, demonstrating that the physical position of the fullerene cage determines the energetic position of the frontier molecular orbitals of PTEG-1.

Biomechanical Effects of Titanium Alloy Based Single versus Dual Cage Fusion Devices

Degenerative disc disease is an increasing problematic complication following lumbar fusion surgeries. Posterior lumbar interbody fusion (PLIF) is a well-established surgical method for spine stability following intervertebral disc removal. The position and number of titanium cages in PLIF are remain contingent on individual surgeon experience. Thus, a systemic investigation of the efficacy of titanium single mega cage versus two cages in treating degenerative lumbar spinal diseases is imperative. A biomechanical study was aimed to compare the stability achieved in PLIF through interbody reconstruction using a single mega cage (32 mm) Vs. a dual cage (22 mm). Normal intact finite element model of L3–L4 was developed based on computed tomography images from a healthy 27-year-old male volunteer. The study tested the intact model (Model A) and its surgically operated counterparts using four PLIF implantation methods: single transverse cage (Model B), single transverse cage with bone graft (Model C), dual transverse cage (Model D), and dual transverse cage with bone graft (Model E). Combined loads simulating physiological motions—flexion, extension, axial rotation, and lateral bending —were applied across all loading directions. The assessment includes all model range of motion (ROM), micromotion between the cage and endplate, and stress on the cage and internal fixation system (screw and rod). The ROM between Models B, C, D and E were consistently reduced by over 71% compared to intact Model A under all motion scenarios. Model D exhibited the highest peak stress of 115 MPa on the cage during flexion, surpassing Model C and E (Flexion) by fourfold. Model E demonstrated the lowest cage stress (20 MPa) during extension, outperforming the other models. Notably, Model E exhibited minimal endplate stress (2 MPa), cage stress (21 MPa), micromotion (13 µm) during extension, and screw-rod stress (56 MPa) during flexion, making it superior to other implantation methods. In the context of PLIF, Model E showed enhanced biomechanical stability, reducing ROM, stress on the endplates, cage, screw-rod system and micromotion. Alternatively, Model C may be a viable alternative in standard PLIF, especially in cases with limited intervertebral space, providing efficient clinical outcomes with shorter operative times and reduced costs and ease of implantation. Also, this computational study provides valuable understandings into optimizing cage implantation strategies for improved outcomes during PLIF.

Cage Obliquity in Oblique Lumbar Interbody Fusion-How Common Is It and What Are the Effects on Fusion Rates, Subsidence, and Sagittal Alignment? A Computed Tomography-Based Analysis.

Oblique lumbar interbody fusion (OLIF) through a prepsoas approach was identified as an alternative to alleviate complications associated with direct lateral interbody fusion. Cage placement is known to influence cage subsidence and fusion rates due to suboptimal biomechanics. There are limited studies exploring cage obliquity as a potential factor influencing fusion outcomes. Hence, our objective was to assess the effects of cage obliquity and position on fusion rates, subsidence, and sagittal alignment in patients who underwent OLIF. Patients who underwent OLIF for levels L1 to L5 in our center, performed by a single surgeon and with a minimum of 12 months of follow-up, were included in the study. Cage obliquity and sagittal placement were measured, and their correlation with fusion, subsidence, and sagittal alignment correction was assessed. Fusion and subsidence were evaluated using the Bridwell Criteria and Marchi Criteria, respectively. Among the included patients (age, 67.5 ± 7.93 years; 16 men and 37 women), 97 fusion levels were studied. The mean cage obliquity was 4.2° ± 2.8°. Ninety-six levels (99.0%) were considered to have achieved fusion with a Bridwell score of 1 or 2. Eighty-one (83.5%), 14 (14.4%), and 2 (2.06%) operated levels had a Marchi score of 0, 1, and 2, respectively. A Marchi grade of 1 or higher was considered indicative of significant subsidence. There was good improvement in both the segmental lordosis angle (4.2° ± 5.7°; P < 0.0001) and disc height (4.5 ± 3.8 mm; P < 0.0001). Cage placement did not have any statistical correlation with fusion rates, subsidence, or sagittal alignment. Our results indicate that OLIF facilitates appropriate cage placement with only a minor degree of cage obliquity, typically less than 20°. This minor obliquity does not lead to lower fusion rates, increased subsidence, or sagittal malalignment. Despite subsidence being common, the majority of these cases resulted in complete fusion.

Oblique Lumbar Interbody Fusion Combined with Posterior Percutaneous Pedicle Screw Internal Fixation: Does Variability in Cage Position Influence Clinical Outcomes?

The study investigates how cage positions in oblique lumbar interbody fusion (OLIF) combined with posterior percutaneous pedicle screw internal fixation (PPSF) affect lumbar canal and foraminal decompression and postoperative outcomes, providing guidance for optimal placement and efficacy assessment. This investigation assesses radiologic outcomes and follow-up data in relation to cage position variability among 80 patients who underwent L4/5 single-segment OLIF+PPSF from 2018 to2022. In the study involving 80 participants, the combination of OLIF and PPSF significantly improved lower back and leg symptoms in patients, leading to positive clinical outcomes during follow-up. The intervertebral disk height increased from an average of 8.10±2.79mm before surgery to 11.75±2.14mm after surgery (P<0.001). Additionally, this surgical technique notably increased the FH (P<0.001) and expanded the DCSA from 68.81±53.89mmˆ2 before surgery to 102.91±60.46mmˆ2 after surgery (P<0.001). Linear results suggest that changes in the position of the cage do not affect spinal imaging parameters. There is no significant difference in the correction of spinal parameters or prognosis whether the cage is back, middle, ahead. In the OLIF+PPSF procedure, strict requirements for cage position are not necessary to achieve predetermined spinal biomechanical parameters. The practice of repeated fluoroscopy to adjust cage position postimplantation does not provide added clinical benefits to the patient.

Transforaminal lumbar interbody fusion subsidence: computed tomography analysis of incidence, associated risk factors, and impact on outcomes.

The aims of this study were to 1) define the incidence of transforaminal lumbar interbody fusion (TLIF) interbody subsidence; 2) determine the relative importance of preoperative and intraoperative patient- and instrumentation-specific risk factors predictive of postoperative subsidence using CT-based assessment; and 3) determine the impact of TLIF subsidence on postoperative complications and fusion rates. All adult patients who underwent one- or two-level TLIF for lumbar degenerative conditions at a multi-institutional academic center between 2017 and 2019 were retrospectively identified. Patients with traumatic injury, infection, malignancy, previous fusion at the index level, combined anterior-posterior procedures, surgery with greater than two TLIF levels, or incomplete follow-up were excluded. Interbody subsidence at the superior and inferior endplates of each TLIF level was directly measured on the endplate-facing surface of both coronal and sagittal CT scans obtained greater than 6 months postoperatively. Patients were grouped based on the maximum subsidence at each operative level classified as mild, moderate, or severe based on previously documented < 2-mm, 2- to 4-mm, and ≥ 4-mm thresholds, respectively. Univariate and regression analyses compared patient demographics, medical comorbidities, preoperative bone quality, surgical factors including interbody cage parameters, and fusion and complication rates across subsidence groups. A total of 67 patients with 85 unique fusion levels met the inclusion and exclusion criteria. Overall, 28% of levels exhibited moderate subsidence and 35% showed severe subsidence after TLIF with no significant difference in the superior and inferior endplate subsidence. Moderate (≥ 2-mm) and severe (≥ 4-mm) subsidence were significantly associated with decreases in cage surface area and Taillard index as well as interbody cages with polyetheretherketone (PEEK) material and sawtooth surface geometry. Severe subsidence was also significantly associated with taller preoperative disc spaces, decreased vertebral Hounsfield units (HU), the absence of bone morphogenetic protein (BMP) use, and smooth cage surfaces. Regression analysis revealed decreases in Taillard index, cage surface area, and HU, and the absence of BMP use predicted subsidence. Severe subsidence was found to be a predictor of pseudarthrosis but was not significantly associated with revision surgery. Patient-level risk factors for TLIF subsidence included decreased HU and increased preoperative disc height. Intraoperative risk factors for TLIF subsidence were decreased cage surface area, PEEK cage material, bullet cages, posterior cage positioning, smooth cage surfaces, and sawtooth surface designs. Severe subsidence predicted TLIF pseudarthrosis; however, the causality of this relationship remains unclear.

Magnetically Induced Thermal Effects on Tobacco Mosaic Virus-Based Nanocomposites for a Programmed Disassembly of Protein Cages.

Protein cages are promising tools for the controlled delivery of therapeutics and imaging agents when endowed with programmable disassembly strategies. Here, we produced hybrid nanocomposites made of tobacco mosaic virus (TMV) and magnetic iron oxide nanoparticles (IONPs), designed to disrupt the viral protein cages using magnetically induced release of heat. We studied the effects of this magnetic hyperthermia on the programmable viral protein capsid disassembly using (1) elongated nanocomposites of TMV coated heterogeneously with magnetic iron oxide nanoparticles (TMV@IONPs) and (2) spherical nanocomposites of polystyrene (PS) on which we deposited presynthesized IONPs and TMV via layer-by-layer self-assembly (PS@IONPs/TMV). Notably, we found that the extent of the disassembly of the protein cages is contingent upon the specific absorption rate (SAR) of the magnetic nanoparticles, that is, the heating efficiency, and the relative position of the protein cage within the nanocomposite concerning the heating sources. This implies that the spatial arrangement of components within the hybrid nanostructure has a significant impact on the disassembly process. Understanding and optimizing this relationship will contribute to the critical spatiotemporal control for targeted drug and gene delivery using protein cages.

Radiographic and surgery-related predictive factors for increased segmental lumbar lordosis following lumbar fusion surgery in patients with degenerative lumbar spondylolisthesis.

This study aimed to evaluate preoperative (pre-op) radiographic characteristics and specific surgical interventions in patients with degenerative lumbar spondylolisthesis (DLS) who underwent lumbar fusion surgery (LFS), with a focus on analyzing predictors of postoperative restoration of segmental lumbar lordosis (SLL). A retrospective review at a single center identified consecutive single-level DLS patients who underwent LFS between 2016 and 2022. Radiographic measures included disc angle (DA), SLL, lumbar lordosis (LL), anterior/posterior disc height (ADH/PDH), spondylolisthesis percentage (SP), intervertebral disc degeneration, and paraspinal muscle quality. Surgery-related measures included cage position, screw insertion depth, spondylolisthesis reduction rate, and disc height restoration rate. A change in SLL ≥ 4° indicated increased segmental lumbar lordosis (ISLL), and unincreased segmental lumbar lordosis (UISLL) < 4°. Propensity score matching was employed for a 1:1 match between ISLL and UISLL patients based on age, gender, body mass index, smoking status, and osteoporosis condition. A total of 192 patients with an average follow-up of 20.9months were enrolled. Compared to UISLL patients, ISLL patients had significantly lower pre-op DA (6.78° vs. 11.84°), SLL (10.73° vs. 18.24°), LL (42.59° vs. 45.75°), and ADH (10.09mm vs. 12.21mm) (all, P < 0.05). ISLL patients were predisposed to more severe intervertebral disc degeneration (P = 0.047) and higher SP (21.30% vs. 19.39%, P = 0.019). The cage was positioned more anteriorly in ISLL patients (67.00% vs. 60.08%, P = 0.000), with more extensive reduction of spondylolisthesis (- 73.70% vs. - 56.16%, P = 0.000) and higher restoration of ADH (33.34% vs. 8.11%, P = 0.000). Multivariate regression showed that lower pre-op SLL (OR 0.750, P = 0.000), more anterior cage position (OR 1.269, P = 0.000), and a greater spondylolisthesis reduction rate (OR 0.965, P = 0.000) significantly impacted SLL restoration. Pre-op SLL, cage position, and spondylolisthesis reduction rate were identified as significant predictors of SLL restoration after LFS for DLS. Surgeons are advised to meticulously select patients based on pre-op SLL and strive to position the cage more anteriorly while minimizing spondylolisthesis to maximize SLL restoration.

Mice Recognise Mice in Neighbouring Rearing Cages and Change Their Social Behaviour.

Mice are social animals that change their behaviour primarily in response to visual, olfactory, and auditory information from conspecifics. Rearing conditions such as cage size and colour are important factors influencing mouse behaviour. In recent years, transparent plastic cages have become standard breeding cages. The advantage of using a transparent cage is that the experimenter can observe the mouse from outside the cage without touching the cage. However, mice may recognise the environment outside the cage and change their behaviour. We speculated that mice housed in transparent cages might recognise mice in neighbouring cages. We used only male mice in this experiment. C57BL/6 mice were kept in transparent rearing cages with open lids, and the cage positions were maintained for 3 weeks. Subsequently, we examined how mice behaved toward cagemate mice, mice from neighbouring cages, and mice from distant cages. We compared the level of interest in mice using a social preference test. Similar to previous reports, subject mice showed a high degree of interest in unfamiliar mice from distant cages. By contrast, subject mice reacted to mice from neighbouring cages as familiar mice, similar to cagemate mice. This suggests that mice housed in transparent cages with open lids perceive the external environment and identify mice in neighbouring cages. Researchers should pay attention to the environment outside the mouse cage, especially for the social preference test.

The Effect of Interbody Cage Parameters on the Rate of Subsidence in Single-Level Anterior Cervical Discectomy and Fusion (ACDF): A Retrospective Analysis of 98 Patients.

Subsidence is arelatively common consequence after anterior cervical discectomy and fusion (ACDF) surgery. This study aimed to identify the effect of radiological and non-radiological risk factors on subsidence after a single-level ACDF surgery with cage and plate. This is a retrospective cohort study of patients who underwent ACDF for radiculopathy or myelopathy at an academic center, University of Kentucky Albert Chandler Hospital, Lexington, Kentucky, United States, between January 2010 and January 2020.Subsidence was defined as the sinking of the interbody cage into the vertebral body at either the superior end plate (SEP) or inferior end plate (IEP) at the ACDF level and was measured manually on lateral standing x-ray. The numerical amount of subsidence was measured in millimeters as the sum of subsidence in the SEP and IEP and was further categorized into subsidence2 and subsidence3 (i.e., presence of subsidence > 2 mm and subsidence > 3 mm, respectively). Multivariateregression analysis was used to assess the effect of variables such as age, gender, body mass index (BMI), tobacco use, follow-up length, cage type, anterior cage height, posterior cage height, anterior cage height ratio, posterior cage height ratio, cage position, cage-end plate interface and cervical alignment on outcomes such as subsidence, subsidence2, and subsidence3. A total of 98 patients were included, of which 46 (47.1%) were male. The mean age of the population was 47.6±8.4 years. Fifty-one patients (52%) experienced subsidence more than 3 mm. Anterior disc height ratio (ADHR) was calculated by dividing the anterior cage height by the anterior disc height (pmADH). The posterior disc height ratio (PDHR) was calculated by dividing the posterior cage height by the posterior disc height (pmPDH). There was no significant correlation between ADHR and PDHR with subsidence, (p=0.93 and 0.56, respectively). Gender, age, BMI, and smoking status did not affect subsidence either. Cage type significantly affected subsidence with a higher subsidence rate in VG2 cages compared to Bengal cages (p=0.05). This study showed that in patients undergoing single-level ACDF with cage and plate, cage size and in particular cage height (if adjusted for individual patients) did not affect subsidence. Other factors such as cage-endplate interface, cage depth in interbody space, and cervical alignment did not significantly affect subsidence either. This might be attributable to the use of an anterior plating system that conducts the force and reduces the stress on the graft-bone interface.

Comparison of Intraoperative Endplate Injury between Mini-Open Lateral Lumbar Interbody Fusion (LLIF) and Transforaminal Lumbar Interbody Fusion (TLIF) and Analysis of Risk Factors: A Retrospective Study

Objective The study aimed to compare the incidence of intraoperative endplate injury in patients who underwent Transforaminal interbody fusion (TLIF) and mini-open lumbar interbody fusion (LLIF) surgery. The independent risk factors related to endplate injury in LLIF procedure were analyzed. Methods A total of 199 patients who underwent LLIF (n = 106) or TLIF (n = 93) surgery from June 2019 to September 2021 were reviewed. The endplate injury was assessed by postoperative sagittal CT scan. A binary logistic analysis model were used to identify independent risk factors related to LLIF endplate injury based on univariate analysis. Results There was an obvious difference in the occurrence of intraoperative endplate injury between LLIF (42/106, 39.6%) and TLIF group (26/93, 28%), although it did not reach the significant level. L1 CT value (OR = 0.985, 95% CI = 0.972–0.998), cage position (OR = 3.881, 95% CI = 1.398–10.771) and height variance (OR = 1.263, 95% CI = 1.013–1.575) were independent risk factors for endplate injury in LLIF procedure. According to the cage settlement patterns, there 5 types of A to E. The severity of the facet joint degeneration was positively related to the occurrence of endplate injury. Conclusions The incidence of intraoperative endplate injury is higher in LLIF than in TLIF procedures. Low bone quantity, cage posterior position and larger height variance are risk factors to induce endplate injury in LLIF surgery. The facet joint degeneration may be related to severe endplate injuries and even fractures.

Should a Narrow Corridor Be a Contraindication for Performing Oblique Lateral Interbody Fusion Procedure or Not?

Retrospective study. We investigated the effect of corridor width on the postoperative outcomes of patients who underwent the OLIF procedure. Patients who underwent OLIF surgery, which included L4-5, between 2015 and 2021 were retrospectively studied. The patients were divided into three groups by the width of the corridor: not more than 10mm, between 10 and 20mm, and 20mm or more. We compared clinical and radiographic outcomes and complications between these groups. A total of 81 patients were included. There were no significant differences in VAS leg and back pain scores, ODI scores, or complications between each group. The radiographic findings, including cage position, anterior and posterior disc height, segmental Cobb angle, and foraminal height, also showed no significant differences between each group. The only radiographic finding that showed a significant difference between each group was the angle of the cage. We found significantly less degree of angle in the wider than 20mm group when compared to the other two groups. (P-value = .01). There was no recorded incidence of major vascular complications. The width of oblique corridor does not affect clinical outcomes, complications, or radiographic findings, including position of the cage, anterior and posterior disc height, segmental angle, and foraminal height after OLIF procedure, including L4-5 level. Thus, the OLIF procedure can be performed safely even in patients with limited oblique corridors, especially at L4-5.

The Influence of Cage Pocket Lubrication on the Simulation of Deep Groove Ball Bearing Cage Motion

Abstract A six degrees-of-freedom dynamic bearing model (DBM) was modified to include a novel cage pocket lubrication model. The motion of the cage was determined using the finite difference method to solve for the pressure generation and resultant forces inside of each cage pocket at each time-step of the dynamic model. The computational domain of the finite difference model was designed to reflect the specific cage pocket geometry of four common cage designs. Additionally, a bearing cage friction test rig was utilized to characterize the lubrication state inside of each cage. Experiments were performed that reveal the relationship between cage shape, ball speed, and relative ball—cage position. Specifically, information on the occurrence of kinematic starvation, the speed-dependent evacuation of oil from a cage pocket, was collected for use as an input condition to the dynamic bearing model. An inverse distance weighting scheme was utilized to predict starvation parameters for a general ball position inside of the cage pocket. Results from the dynamic simulation reveal new knowledge on the effect of cage geometry and lubrication on dynamic behavior. The inclusion of lubrication effects inside of the cage pocket reduces the median contact force between the balls and cage pocket and improves the stability of the predicted cage motion.

An ethogram of acute pain behaviors in cats based on expert consensus.

An improved understanding of behaviors reflecting acute pain in cats is a priority for feline welfare. The aim of this study was to create and validate a comprehensive ethogram of acute pain behaviors in cats that can discriminate painful versus non-painful individuals. An inventory of behaviors (ethogram) with their respective descriptors was created based on a literature review of PubMed, Web of Science and CAB Abstracts databases. The ethogram was divided into ten behavior categories that could be evaluated by duration and/or frequency: position in the cage, exploratory behaviors, activity, posture and body position, affective-emotional states, vocalization, playing (with an object), feeding, post-feeding and facial expressions/features. Thirty-six behaviors were analyzed independently by four veterinarians with postgraduate qualifications in feline medicine and/or behavior as (1) not relevant, (2) somewhat relevant, (3) quite relevant or (4) highly relevant and used for content (I-CVI) and face validity. Items with I-CVI scores > 0.67 were included. Twenty-four behaviors were included in the final ethogram. Thirteen items presented full agreement (i.e., I-CVI = 1): positioned in the back of the cage, no attention to surroundings, feigned sleep, grooming, attention to wound, crouched/hunched, abnormal gait, depressed, difficulty grasping food, head shaking, eye squinting, blepharospasm and lowered head position. Seven descriptors were reworded according to expert suggestions. The final ethogram provides a detailed description of acute pain behaviors in cats after content and face validity and can be applied to the characterization of different acute painful conditions in hospitalized cats.

Factors affecting successful immediate indirect decompression in oblique lateral interbody fusion in lumbar spinal stenosis patients

BackgroundOblique lumbar interbody fusion (OLIF) offers indirect decompression of stenotic lesions of the spinal canal and foramen through immediate disc height restoration. Only a few studies have reported the effect of cage position and associated intraoperatively modifiable factors for successful immediate indirect decompression following OLIF surgery. This study aimed to investigate the intraoperatively modifiable factors for successful radiological outcomes of OLIF. MethodsThis study included 46 patients with 80 surgical levels who underwent OLIF without direct posterior decompression. Preoperative and postoperative radiological parameters were evaluated and intraoperatively modifiable radiologic parameters for successful immediate radiologic decompression on magnetic resonance image (MRI) were determined. Radiologic parameters were preoperative and postoperative radiological parameters including anterior disc height (ADH), posterior disc height (PDH) lumbar lordotic angle (LLA), segmental lordotic angle (SLA), foraminal height (FH), cage position, cross-sectional area (CSA) of the thecal sac, cross-sectional foraminal area (CSF), facet distance (FD) ResultsAll radiologic outcomes significantly improved. Comparing preoperative and postoperative values, mean CSA increased from 99.63±40.21 mm2 to 125.02±45.90 mm2 (p<.0001), and mean left CSF increased from 44.54±12.90 mm2 to 69.91±10.80 mm2 (p<.0001). FD also increased from 1.40±0.44 to 1.92±0.71 mm (p<.0001). FH increased from 16.31±3.3 to 18.84±3.47 mm (p<.0001). ADH and PDH also significantly increased (p<.0001). Immediate postoperative CSF and FH improvement rate (%) were significantly correlated with posterior disc height restoration rate (%) (p=.0443, and p=.0234, respectively). In addition, the patients with a cage positioned in the middle of the vertebral body experienced a greater FH improvement rate (%) compared to the patients with a cage positioned anteriorly. Finally, Visual analogue scale (VAS) for leg pain was improved immediately. ConclusionsOLIF provided satisfactory immediate indirect decompression in central and foraminal spinal stenosis. Moreover, intraoperative surgical technique for successful radiologic CSF and FH improvement included restoration of the PDH and placement of the cage in the middle.

Radiographic and Patient-Reported Outcomes in Anteriorly Placed Transforaminal Lumbar Interbody Fusion Cage Versus Anterior Lumbar Interbody Fusion With Posterior Instrumentation.

Retrospective cohort study. To compare outcomes in anteriorly placed transforaminal lumbar interbody fusions (TLIFs) and anterior lumbar interbody fusions (ALIFs). TLIF and ALIF are surgical techniques that have become more prevalent in recent years. Although studies have compared the two, none have considered TLIFs with anteriorly placed cages, which may serve as a better comparison to ALIFs. Patients undergoing TLIF or ALIF with posterior instrumentation from 2010 to 2020 at a tertiary care institution were retrospectively identified. TLIF cage position was assessed and those with anterior placement were included. Electronic medical records were reviewed to identify patient characteristics and patient-reported outcomes. Radiographic outcomes included posterior disc height (DH), lumbar lordosis (LL), sacral slope, pelvic incidence, and pelvic tilt. Statistical analysis was performed to compare the two groups. Of the 351 patients, 108 had ALIF with posterior instrumentation and 207 had a TLIF. Preoperatively, patients undergoing TLIF had less LL (53.7° vs . 60.6°, P < 0.001), sacral slope (38.3° vs . 43.7°, P < 0.001), and pelvic incidence (60.1° vs . 66.1°, P < 0.001), all of which remained significant at 1-year and long-term follow-up ( P < 0.001). The TLIF group had less ∆DH (1.51° vs . 5.43°, P < 0.001), ∆LL (1.8° vs . 2.97°, P = 0.038), and ∆segmental lordosis (0.18° vs . 4.40°, P < 0.001) at 1 year postoperatively. At 2 to 3 years, ∆DH ( P < 0.001) and ∆segmental lordosis ( P = 0.001) remained significant, but ∆LL ( P = 0.695) did not. Patients in the TLIF group had higher Visual Analog Scale-Back scores 1 year postoperatively (3.68 vs . 2.16, P = 0.008) and experienced less improvement in Oswestry Disability Index (-17.1 vs . -28.6, P = 0.012) and Visual Analog Scale-Back (-2.67 vs . -4.50, P = 0.008) compared with patients undergoing ALIF. Our findings suggest that ALIF with posterior instrumentation performed superiorly in radiographic outcomes and patient-reported outcomes compared with anteriorly placed TLIFs. Anteriorly placed TLIF cages may not achieve the same results as those of ALIF cages.