Lumbar Spine Specimens Research Articles

Intervertebral disc creep behaviour through viscoelastic models: an in-vitro study

The intervertebral disc (IVD) is a complex biological structure that ensures the spine strength, stability, mobility, and flexibility. This is achieved due to its biphasic nature which is attained by its solid phase (annulus fibrosus) and fluid phases (nucleus pulposus). Hence, the IVD biomechanical response to long-term loads, which is critical as it affects hydration, and nutrients-water transport influencing disc height reduction, has been further explored and mathematically modelled in this paper. An in-vitro study was performed on seven human lumbar spine specimens (L4-5), to assess if the classical rheological models and Nutting's power law can model in a simple way the intermediate characteristics between solid and fluid of the IVD. Creep tests were conducted by applying a static compression load of 500 N for 15 min. A correlation analysis was done (Pearson, p < 0.05) between the model parameters and the maximum value of Disc Height Reduction, followed by a linear regression analysis. In summary, the long-term IVD mechanical behavior was modeled in a simple way, emphasizing that yet there is no mathematical certainty about this mechanical behavior. Hence, a future aim might be to develop intervertebral disc prostheses capable of replicating only the disc mechanical response, without necessarily considering the microscopic-level biological drivers. Therefore, a future goal is to fully understand and model the disc's mechanical response toward the design of new disc prostheses that would consider only the macroscopic aspect, without considering the biological aspects.

Indirect Puncture Using a Novel Arc Puncture-Guided Device in Percutaneous Transforaminal Puncture on Goat Lumbar Spine Specimens

To investigate the implication of indirect puncture using a novel arc puncture-guided device in percutaneous transforaminal puncture in improving the puncture accuracy, reducing fluoroscopy times, puncture times and operation time. We have designed a novel arc puncture-guided device which consists of a 90°arc block and a 30°arc block. Punctures were performed on 8 fresh goat lumbar spine specimens. A senior doctor performed indirect punctures on the left side of L2/L3, L3/L4 and L4/L5 level side using the novel device (group A)，and on the right side of L2/L3, L3/L4 and L4/L5 level with conventional method (group B). We recorded the fluoroscopy times, puncture times and operation time. In group A, the first puncture could successfully reach the target after 1-3 punctures, and the one-time success rate of the second needle puncture is 91.67%. The total fluoroscopy times were 14.88±0.99 in group A and 16.08±2.22 in group B (p=0.027). The puncture times were 3.00±0.66 in group A and 6.04±2.13 in group B (P < 0.01). The operation time(s) was 273.75±30.19 in group A and 361.25±69.57 in group B (P < 0.01). There were significant differences in fluoroscopy times，puncture times and operation time between the two groups(P < 0.05). The indirect puncture using the novel arc puncture-guided device in percutaneous transforaminal puncture can significantly improve the puncture accuracy, reduce fluoroscopy times, puncture times and operation time. Indirect puncture using the novel device in percutaneous transforaminal endoscopic discectomy (PTED) is a potential and practical puncture method.

Biomechanical investigation of the hybrid lumbar fixation technique with traditional and cortical bone trajectories in transforaminal lumbar interbody fusion: finite element analysis

ObjectiveTo compare the biomechanical performance of the hybrid lumbar fixation technique with the traditional and cortical bone trajectory techniques using the finite element method.MethodsFour adult wet lumbar spine specimens were provided by the Department of Anatomy and Research of Xinjiang Medical University, and four L1–S1 lumbar spine with transforaminal lumbar interbody fusion (TLIF) models at L4–L5 segment and four different fixation techniques were established: bilateral traditional trajectory screw fixation (TT–TT), bilateral cortical bone trajectory screw fixation (CBT–CBT), hybrid CBT–TT (CBT screws at L4 and TT screws at L5) and TT–CBT (TT screws at L4 and CBT screws at L5). The range of motion (ROM) of the L4–L5 segment, von Mises stress of cage, internal fixation, and rod were compared in flexion, extension, left and right bending, and left and right rotation.ResultsCompared with the TT–TT group, the TT–CBT group exhibited lower ROM of L4–L5 segment, especially in left-sided bending; the CBT–TT group had the lowest ROM of L4–L5 segment in flexion and extension among the four fixation methods. Compared with the CBT–CBT group, the peak cage stress in the TT–CBT group was reduced by 9.9%, 18.1%, 21.5%, 23.3%, and 26.1% in flexion, left bending, right bending, left rotation, and right rotation conditions, respectively, but not statistically significant (P > 0.05). The peak stress of the internal fixation system in the TT–CBT group was significantly lower than the other three fixation methods in all five conditions except for extension, with a statistically significant difference between the CBT–TT and TT–CBT groups in the left rotation condition (P = 0.017). In addition, compared with the CBT–CBT group, the peak stress of the rod in the CBT–TT group decreased by 34.8%, 32.1%, 28.2%, 29.3%, and 43.0% under the six working conditions of flexion, extension, left bending, left rotation, and right rotation, respectively, but not statistically significant (P > 0.05).ConclusionsCompared with the TT–TT and CBT–CBT fixation methods in TLIF, the hybrid lumbar fixation CBT–TT and TT–CBT techniques increase the biomechanical stability of the internal fixation structure of the lumbar fusion segment to a certain extent and provide a corresponding theoretical basis for further development in the clinic.

Dark-field X-ray imaging for the assessment of osteoporosis in human lumbar spine specimens.

Background: Dark-field imaging is a novel imaging modality that allows for the assessment of material interfaces by exploiting the wave character of x-ray. While it has been extensively studied in chest imaging, only little is known about the modality for imaging other tissues. Therefore, the purpose of this study was to evaluate whether a clinical X-ray dark-field scanner prototype allows for the assessment of osteoporosis. Materials and methods: In this prospective study we examined human cadaveric lumbar spine specimens (vertebral segments L2 to L4). We used a clinical prototype for dark-field radiography that yields both attenuation and dark-field images. All specimens were scanned in lateral orientation in vertical and horizontal position. All specimens were additionally imaged with CT as reference. Bone mineral density (BMD) values were derived from asynchronously calibrated quantitative CT measurements. Correlations between attenuation signal, dark-field signal and BMD were assessed using Spearman's rank correlation coefficients. The capability of the dark-field signal for the detection of osteoporosis/osteopenia was evaluated with receiver operating characteristics (ROC) curve analysis. Results: A total of 58 vertebrae from 20 human cadaveric spine specimens (mean age, 73years ±13 [standard deviation]; 11 women) were studied. The dark-field signal was positively correlated with the BMD, both in vertical (r = 0.56, p < .001) and horizontal position (r = 0.43, p < .001). Also, the dark-field signal ratio was positively correlated with BMD (r = 0.30, p = .02). No correlation was found between the signal ratio of attenuation signal and BMD (r = 0.14, p = .29). For the differentiation between specimens with and without osteoporosis/osteopenia, the area under the ROC curve (AUC) was 0.80 for the dark-field signal in vertical position. Conclusion: Dark-field imaging allows for the differentiation between spine specimens with and without osteoporosis/osteopenia and may therefore be a potential biomarker for bone stability.

Interspinous-Interbody Fusion via a Strictly Lateral Surgical Approach: A Biomechanical Stabilization Comparison to Constructs Requiring Both Lateral and Posterior Approaches.

Objective Lumbar fusion performed through lateral approaches is becoming more common. The interbody devices are generally supported by supplemental posterior fixation implanted through a posterior approach, potentially requiring a second incision and intraoperative repositioning of the patient. A minimally invasive lateral interspinous fixation device may eliminate the need for intraoperative repositioning and avoid disruption of the supraspinous ligament. The objective of this in vitrobiomechanical study was to investigate segmental multidirectional stability and maintenance of foraminal distraction of a lateral interspinous fixation device compared to commonly used pedicle screw and facet screw posterior fixation constructs when combined with lumbar interbody cages. Methods Six human cadaver lumbar spine specimens were subjected to nondestructive quasistatic loading in the following states: (1) intact; (2) interspinous fixation device alone and (3) with lateral interbody cage; (4) lateral lumbar interbody cage with bilateral pedicle screws; (5) lateral lumbar interbody cage with unilateral pedicle screws; and (6) lateral lumbar interbody cage with facet screws. Multidirectional pure bending in 1.5 Nm increments to 7.5 Nm, and 7.5 Nm flexion-extension bending with a 700 N compressive follower load were performed separately with optoelectronic segmental motion measurement. Relative angular motions of L2-L3, L3-L4, and L4-L5 functional spinal units were evaluated, and the mean instantaneous axis of rotation in the sagittal plane was calculated for the index level.Foraminal height was assessed during combined flexion-extension and compression loading for each test construct. Results All implant configurations significantly restricted flexion-extension motion compared with intact (p < 0.05). No significant differences were found in flexion-extension when comparing the different posterior implants combined with lateral lumbar interbody cages. All posterior fixation devices provided comparable neuroforaminal distraction and maintained distraction during flexion and extension. Conclusions When combinedwith lateral lumbar interbody cages, the minimally invasive lateral interspinous fixation device effectively stabilized the spine and maintained neuroforaminal distraction comparable to pedicle screw constructs or facet screws. These results suggest the lateral interspinous fixation device may provide a favorable alternative to other posterior systems that require patient repositioning during surgery and involve a greater disruption of native tissues.

Exploring the Possibility of Measuring Vertebrae Bone Structure Metrics Using MDCT Images: An Unpaired Image-to-Image Translation Method

Bone structure metrics are vital for the evaluation of vertebral bone strength. However, the gold standard for measuring bone structure metrics, micro-Computed Tomography (micro-CT), cannot be used in vivo, which hinders the early diagnosis of fragility fractures. This paper used an unpaired image-to-image translation method to capture the mapping between clinical multidetector computed tomography (MDCT) and micro-CT images and then generated micro-CT-like images to measure bone structure metrics. MDCT and micro-CT images were scanned from 75 human lumbar spine specimens and formed training and testing sets. The generator in the model focused on learning both the structure and detailed pattern of bone trabeculae and generating micro-CT-like images, and the discriminator determined whether the generated images were micro-CT images or not. Based on similarity metrics (i.e., SSIM and FID) and bone structure metrics (i.e., bone volume fraction, trabecular separation and trabecular thickness), a set of comparisons were performed. The results show that the proposed method can perform better in terms of both similarity metrics and bone structure metrics and the improvement is statistically significant. In particular, we compared the proposed method with the paired image-to-image method and analyzed the pros and cons of the method used.

Biomechanical evaluation of the hybrid pedicle screw—cortical bone trajectory technique in transforaminal lumbar interbody fusion to adjacent segment degeneration—finite element analysis

BackgroundTransforaminal lumbar interbody fusion is an effective surgical treatment of intervertebral disk herniation. However, its clinical efficacy for adjacent segment disk degeneration (ASDD) after hybrid bilateral pedicle screw - bilateral cortical screw (pedicle screw at L4 and cortical bone trajectory screw at L5) and hybrid bilateral cortical screw - bilateral pedicle screw (bilateral cortical screw at L4 and bilateral pedicle screw at L5) remains undiscovered. Therefore, the aim of this study is to evaluate the effect of the hybrid bilateral pedicle screw - bilateral cortical screw and hybrid bilateral cortical screw - bilateral pedicle screw on the adjacent segment via a 3-dimensional (3D) finite element (FE) analysis.MethodsFour human cadaveric lumbar spine specimens were provided by the anatomy teaching and research department of Xinjiang Medical University. Four finite element models of L1-S1 lumbar spine segment were generated. For each of these, four lumbar transforaminal lumbar interbody fusion models at L4-L5 segment with the following instruments were created: hybrid bilateral pedicle screw - bilateral cortical screw, bilateral cortical screw - bilateral cortical screw (bilateral cortical screw at both L4 and L5 segments), bilateral pedicle screw - bilateral pedicle screw (bilateral pedicle screw at both L4 and L5 segments), and hybrid bilateral cortical screw - bilateral pedicle screw. A 400-N compressive load with 7.5 Nm moments was applied for the simulation of flexion, extension, lateral bending, and rotation. The range of motion of L3-L4 and L5-S1 segments and von Mises stress of the intervertebral disc at the adjacent segment were compared.ResultsHybrid bilateral pedicle screw - bilateral cortical screw has the lowest range of motion at L3-L4 segment in flexion, extension, and lateral bending, and the highest disc stress in all motions, while the range of motion at L5-S1 segment and disc stress was lower than bilateral pedicle screw - bilateral pedicle screw in flexion, extension, and lateral bending, and higher than bilateral cortical screw - bilateral cortical screw in all motions. The range of motion of hybrid bilateral cortical screw - bilateral pedicle screw at L3-L4 segment was lower than bilateral pedicle screw - bilateral pedicle screw and higher than bilateral cortical screw - bilateral cortical screw in flexion, extension, and lateral bending, and the range of motion at L5-S1 segment was higher than bilateral pedicle screw - bilateral pedicle screw in flexion, lateral bending, and axial rotation. The disc stress at L3-L4 segment was lowest and more dispersed in all motions, and the disc stress at L5-S1 segment was higher than bilateral pedicle screw - bilateral pedicle screw in lateral bending and axial rotation, but more dispersed.ConclusionHybrid bilateral cortical screw - bilateral pedicle screw decreases the impact on adjacent segments after spinal fusion, reduces the iatrogenic injury to the paravertebral tissues, and provides throughout decompression of the lateral recess.

In vitro coupled motions of the whole human thoracic and lumbar spine with rib cage.

In vitro biomechanical study investigating the coupled motions of the whole normative human thoracic spine (TS) and lumbar spine (LS) with rib cage. To quantify the region-specific coupled motion patterns and magnitudes of the TS, thoracolumbar junction (TLJ), and LS simultaneously. Studying spinal coupled motions is important in understanding the development of complex spinal deformities and providing data for validating computational models. However, coupled motion patterns reported in vitro are controversial, and no quantitative data on region-specific coupled motions of the whole human TS and LS are available. Pure, unconstrained bending moments of 8 Nm were applied to seven fresh-frozen human cadaveric TS and LS specimens (mean age: 70.3 ± 11.3 years) with rib cages to elicit flexion-extension (FE), lateral bending (LB), and axial rotation (AR). During each primary motion, region-specific rotational range of motion (ROM) data were captured. No statistically significant, consistent coupled motion patterns were observed during primary FE. During primary LB, there was significant (p < 0.05) ipsilateral AR in the TS and a general pattern of contralateral coupled AR in the TLJ and LS. There was also a tendency for the TS to extend and the LS to flex. During primary AR, significant coupled LB was ipsilateral in the TS and contralateral in both the TLJ and LS. Significant coupled flexion in the LS was also observed. Coupled LB and AR ROMs were not significantly different between the TS and LS or from one another. The findings support evidence of consistent coupled motion patterns of the TS and LS during LB and AR. These novel data may serve as reference for computational model validations and future in vitro studies investigating spinal deformities and implants.

Evaluation of the resection efficiency and safety of an enhanced power plasma generator using cadaveric intervertebral discs.

Plasma energy has been used to provide minimally invasive interventional treatment for spinal problems. However, this procedure has been used for limited indications mainly because of its small resection range. To overcome this problem, we designed the enhanced power plasma device. This device seeks to maximize the resection area by modifying the electrode arrangement and enhancing the maximum electric power. The purpose of this study is to assess the efficiency and safety of this newly designed plasma generator, a device for percutaneous disc decompression. We performed an intradiscal procedure on 7 fresh human cadaver lumbar spine specimens using the enhanced power plasma under C-arm fluoroscopic guidance at various voltages. As a result, the volume of the removed area was proportional to the applied magnitude of the electric power level. In particular, under the high-power level condition after 500s treatment, nearly the entire nucleus pulposus was eliminated. The generated plasma density also tends to grow along with the given electric power. The highest level of temperature rise did not exceed the level that would lead to degeneration in the collagen tissue of the intervertebral disc. Histopathologic examination also demonstrated that there was no thermal damage to the surrounding neural tissues. In conclusion, we speculate that the concepts of this newly designed enhanced plasma generator could be applied to remove huge disc materials without thermal or structural damage to the adjacent target tissues in future spine clinics.

Feasibility and improvement of a three-dimensional printed navigation template for modified cortical bone trajectory screw placement in the lumbar spine.

Compared with traditional pedicle screw trajectory, cortical bone trajectory (CBT) increases the contact surface between the screw and cortical bone where the screw is surrounded by dense cortical bone, which does not deform remarkably due to degeneration. We aimed to provide detailed information about the improvement of three-dimensional (3D)-printed navigation templates for modified CBT screw placement in the lumbar spine and evaluate the safety and accuracy thereof. Four human cadaveric lumbar spine specimens were selected. After CT scanning data were reconstructed to 3D models, either the left or right side of each specimen was randomly selected to establish a 3D-navigation template, mutually complemented with the surface anatomical structure of the lateral margin of the lumbar isthmus, vertebral plate, and spinous process. The corresponding 3D centrum was printed according to the CT scanning data, and a navigation template of supporting design was made according to modified cortical bone technique. The same template was used to insert CBT screws into 3D printed and cadaveric specimens. After the screws were inserted, the screw path of the 3D printed specimens was directly observed, and that of the anatomical specimens was scanned by CT, to determine the position and direction of the screws to analyze the success rate of screw placement. Twenty cortical bone screws were placed in each of the 3D printed and anatomical specimens, with excellent rates of screw placement of 100% and 95%, respectively. We report the easy, safe, accurate, and reliable use of a 3D-printed navigation template to carry out screw placement by modified cortical bone technique in the lumbar spine.

Retrodural space of Okada in the posterior ligamentous complex region: clinical and anatomical findings relevant to lumbar interlaminar epidural injection

BackgroundThe retrodural space of Okada is a potential space posterior to the ligamentum flavum that allows communication with the bilateral facet joints. However, the actual anatomy of this space has...

Predicting Pedicle Screw Pullout and Fatigue Performance: Comparing Lateral Dual-Energy X-Ray Absorptiometry, Anterior to Posterior Dual-Energy X-Ray Absorptiometry, and Computed Tomography Hounsfield Units.

As the prevalence and associated health care costs of osteoporosis continue to rise in our aging population, there is a growing need to continue to identify methods to predict spine construct integrity accurately and cost-effectively. Dual-energy x-ray absorptiometry (DEXA) in both anterior to posterior (AP) and lateral planes, as well as computed tomography (CT) Hounsfield units (HU), have all been investigated as potential preoperative predictive tools. The purpose of this study is to determine which of the 3 bone density analysis modalities has the highest potential for predicting pedicle screw biomechanics. Lumbar spine specimens (L2, L3, and L4) from 6 fresh frozen cadavers were used for testing. AP-DEXA, lateral-DEXA, and CT images were obtained. Biomechanical testing of pedicle screws in each vertebrae was then performed including pullout strength and fatigue testing. Statistical analysis was performed. Pullout strength was best predicted by CT HU, followed by AP-DEXA, then lateral-DEXA (R 2 = 0.78, 0.70, and 0.40, respectively). Fatigue testing showed a significant correlation of relative rotation between HU value and AP-DEXA bone mineral density (R 2 = 0.54 and R 2 = 0.72, respectively), and there was a significant correlation between relative translation and HU value (R 2 = 0.43). There was a poor correlation between relative rotation and lateral-DEXA (R 2 = 0.13) as well as a poor correlation between relative translation and both AP- and lateral-DEXA (R 2 = 0.35 and R 2 = 0.02). CT is the only modality with a statistically significant correlation to all biomechanical parameters measured (pullout strength, relative angular rotation, and relative translation). AP-DEXA also predicts the biomechanical measures of screw pullout and relative angular rotation and is superior to lateral-DEXA. CT may provide an incremental benefit in assessing fatigue strength, but this should be weighed against the disadvantages of cost and radiation. The results of this study can help to inform clinicians on different bone density analyses and their implications on pedicle screw failure.

7. Does Cutibacterium acnes (C. acnes, formerly Propionibacterium acnes) play a role in degenerative disc disease?

<h3>BACKGROUND CONTEXT</h3> Degenerative disc disease (DDD) is a major burden to society, leading to disability and loss in productivity. In 2005, an estimated $86 billion was spent in the United States for management of neck and back problems. Recent evidence suggests that Cutibacterium acnes (C. acnes), an anaerobic bacterium, may latently reside in intervertebral discs (IVDs) and contribute to DDD. <h3>PURPOSE</h3> To determine the presence of C. acnes in IVD specimens and to correlate this with Pfirrmann grading on MRI. <h3>STUDY DESIGN/SETTING</h3> The intervertebral discs of 63 DDD patients and 5 control patients were collected prospectively. <h3>PATIENT SAMPLE</h3> Sixty-eight patients presenting to a single academic center for spine surgery were enrolled. <h3>OUTCOME MEASURES</h3> Pfirrmann grading, presence of C. acnes based on taxonomic identification. <h3>METHODS</h3> We collected human IVD specimens from surgical patients undergoing discectomy and interbody fusion from a single institution from 8/2019 to 9/2020. Disc degeneration was graded according to the 5-level Pfirrmann grading system on MRI imaging taken prior to surgery. IVD specimens from trauma patients (Pfirrmann grades I-II) were included in the control group, and IVD specimens were included in the degenerative group with Pfirrmann grades III-V. IVD specimens were processed for DNA extraction, and 16S rRNA libraries were constructed and analyzed for taxonomic data. <h3>RESULTS</h3> There were 63 patients included within the DDD group and 5 patients within the control group. Within the degenerative group, IVD specimens were taken from patients who had undergone spine surgery within the lumbar spine (n = 42; 66.7%), cervical spine (n = 19; 30.2%), and thoracic spine (n = 2; 3.2%). The average age of the DDD group was 54.3 ±13.9 years old, 57.1% (36/63) were male, and 85.7% (54/63) were Caucasian. A total of 31.7% (20/63) of DDD specimens were identified with the presence of C. acnes. There were 28.6% (12/42) of lumbar spine IVD specimens, 42.1% (8/19) of cervical spine IVD specimens, 0% (0/2) of thoracic spine IVD specimens that were identified with C. acnes. There was no difference in the presence of C. acnes when comparing the cervical, thoracic, and lumbar spine specimens (p = 0.36). When stratifying the DDD specimens by MRI Pfirmann grading, there were 31.3% (5/16) of specimens with a Pfirmann grade of 3, 31.3% (10/32) of specimens with a Pfirrmann grade of 4, and 33.3% (5/15) of specimens with a Pfirrmann grade of 5 that were identified with C. acnes. There was no difference in the presence of C. acnes when comparing the DDD specimens based on Pfirrmann grading (p = 0.99). There were 5 IVD specimens included within the control group with an average age of 39.8 ±20.5 years old, and 80% (4/5) were Caucasian males. The control group included IVD specimens taken from two lumbar and three cervical spine surgerie. Four of five (80%) of the specimens had a Pfirrmann grade of 2 on MRI, and 1/5 (20%) had a Pfirrmann grade of 1. No control specimens were identified with the presence of C. acnes. <h3>CONCLUSIONS</h3> Of the DDD specimines, 31.7% (20/63) were identified with the presence of C. acnes, while none of the specimens of the control group were identified with this bacterium. These results suggest that indolent C. acnes infection may be one of the factors contributing to degenerative disc disease. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

Upregulated of ANXA3, SORL1, and Neutrophils May Be Key Factors in the Progressionof Ankylosing Spondylitis.

IntroductionThe specific pathogenesis of ankylosing spondylitis (AS) remains unclear, and our study aimed to investigate the possible pathogenesis of AS.Materials and MethodsTwo datasets were downloaded from the GEO database to perform differentially expressed gene analysis, GO enrichment analysis, KEGG pathway analysis, DO enrichment analysis, GSEA analysis of differentially expressed genes, and construction of diagnostic genes using SVM and WGCNA along with Hypoxia-related genes. Also, drug sensitivity analysis was performed on diagnostic genes. To identify the differentially expressed immune genes in the AS and control groups, we analyzed the composition of immune cells between them. Then, we examined differentially expressed genes in three AS interspinous ligament specimens and three Degenerative lumbar spine specimens using high-throughput sequencing while the immune cells were examined using the neutrophil count data from routine blood tests of 1770 HLA-B27-positive samples and 7939 HLA-B27-negative samples. To assess the relationship between ANXA3 and SORL1 and disease activity, we took the neutrophil counts of the first 50 patients with above-average BASDAI scores and the last 50 patients with below-average BASDAI scores for statistical analysis. We used immunohistochemistry to verify the expression of ANXA3 and SORL1 in AS and in controls.ResultsANXA3 and SORL1 were identified as new diagnostic genes for AS. These two genes showed a significant differential expression between AS and controls, along with showing a significant positive correlation with the neutrophil count. The results of high-throughput sequencing verified that these two gene deletions were indeed differentially expressed in AS versus controls. Data from a total of 9707 routine blood tests showed that the neutrophil count was significantly higher in AS patients than in controls (p < 0.001). Patients with AS with a high BASDAI score had a much higher neutrophil count than those with a low score, and the difference was statistically significant (p < 0.001). The results of immunohistochemistry showed that the expression of ANXA3 and SORL1 in AS was significantly higher than that in the control group.ConclusionUpregulated of ANXA3, SORL1, and neutrophils may be a key factor in the progression of Ankylosing spondylitis.

Primary stability of the Activ L® intervertebral disc prosthesis in cadaver bone and comparison of the keel and spike anchoring concept

BackgroundHigh primary stability is the key prerequisite for safe osseointegration of cementless intervertebral disc prostheses. The aim of our study was to determine the primary stability of intervertebral disc prostheses with two different anchoring concepts – keel and spike anchoring.MethodsTen ActivL intervertebral disc prostheses (5 x keel anchoring, 5 x spike anchoring) implanted in human cadaver lumbar spine specimens were tested in a spine movement simulator. Axial load flexion, extension, left and right bending and axial rotation motions were applied on the lumbar spine specimens through a defined three-dimensional movement program following ISO 2631 and ISO/CD 18192-1.3 standards. Tri-dimensional micromotions of the implants were measured for both anchor types and compared using Student’s T-test for significance after calculating 95 % confidence intervals.ResultsIn the transverse axis, the keel anchoring concept showed statistically significant (p < 0.05) lower mean values of micromotions compared to the spike anchoring concept. The highest micromotion values for both types were observed in the longitudinal axis. In no case the threshold of 200 micrometers was exceeded.ConclusionsBoth fixation systems fulfill the required criteria of primary stability. Independent of the selected anchorage type an immediate postoperative active mobilization doesn’t compromise the stability of the prostheses.

The Human Lumbar Spine During High-Rate Under Seat Loading: A Combined Metric Injury Criteria.

Modern changes in warfare have shown an increased incidence of lumbar spine injuries caused by underbody blast events. The susceptibility of the lumbar spine during these scenarios could be exacerbated by coupled moments that act with the rapid compressive force depending on the occupant's seated posture. In this study, a combined loading lumbar spine vertebral body fracture injury criteria (Lic) across a range of postures was established from 75 tests performed on instrumented cadaveric lumbar spine specimens. The spines were predominantly exposed to axial compressive forces from an upward vertical thrust with 64 of the tests resulting in at least one vertebral body fracture and 11 in no vertebral body injury. The proposed Lic utilizes a recommended metric (κ), based on prismatic beam failure theory, resulting from the combination of the T12-L1 resultant sagittal force and the decorrelated bending moment with optimized critical values of Fr,crit = 5824N and My,crit = 1155Nm. The 50% risk of lumbar spine injury corresponded to a combined metric of 1, with the risk decreasing with the combined metric value. At 50% injury risk the Normalized Confidence Interval Size improved from 0.24 of a force-based injury reference curve to 0.17 for the combined loading metric.

Measurement of strain in the rod for lumbar pedicle screw fixation: An experimental and finite element study

Spinal fusion with pedicle-screw-rod is being used widely for treating spinal deformities diseases. Several biomechanical studies on screw rod based implant failure through screw pullout, bending, screw breakage have been performed. But few studies are available regarding the effect of strain for breakage of rod. So, the purpose of the present study is to observe strain at the rod connected with the pedicle screw for different loading condition. The strain in stainless steel (SS) connecting rods for pedicle screw fixation were measured using strain gauge. In order to investigate the bio-mechanical response of lumbar spine with reference to strain in the rod, a simple experimental setup was developed using a specimen of L1-S spine segment. SS rods were used for pedicle screw implant on prototyped lumbar Spine. Prior to testing with pedicle screw, the lumbar spine specimen was also compared with FE results. The strain measured using strain gauges at L3-L4 level on SS rod were within a range of 85 to 310 microstrain under 6, 8, 10 Nm flexion and extension, and for L4-L5 level, these values were within a range of 95 to 440 microstrain. It was found that FE result was higher than the strain gauge result and the error varied between 10.5% to 33% with average error of 22.8%. However similar stain behavior was observed by the FE analysis. The proposed method, as well as the qualitative data, might be helpful for the researchers to understand biomechanical behavior of pedicle-screw implanted spine.

Anatomy and Imaging Studies on Cortical Bone Screw Freehand Placement Applying Anatomical Targeting Technology.

ObjectivesA series of constant anatomical structures were used as guide targets for screw placement to improve the accuracy of cortical screw placement and reduce surgical injury and fluoroscopy radiation. The most commonly used angles and distances between the cortical bone screw insertion point and the lateral margins of the isthmus were selected as the contents of the questionnaire.MethodsA total of 40 physicians were selected to determine the specific values for each angle and distance. Screw placements were performed on four dry and six wet lumbar spine specimens according to the proposed anatomical target guidance technique. A total of 100 cortical bone trajectories were evaluated using X‐ray and CT scanning of the specimens to verify the practicability, accuracy, and safety of the anatomical target guidance technique in screw placement.ResultsThe average deviation rates for angle and distance determination were 105.5% and 14.33%, respectively, indicating a significant difference between the estimated and actual values from other angles (P < 0.05). Based on visual inspection, probe penetration, X‐ray, and CT examination of 100 cortical bone trajectories, the excellent rate of 40 trajectories on four dry specimens was 95%, while that of 60 trajectories on six wet specimens was 88.7%.ConclusionUse of lumbar constant anatomical structures as targeting guidance could assist cortical bone screw placement and reduce surgical damage.

ICR in human cadaveric specimens: An essential parameter to consider in a new lumbar disc prosthesis design

Study designBiomechanical study in cadaveric specimens.BackgroundThe commercially available lumbar disc prostheses do not reproduce the intact disc's Instantaneous centre of Rotation (ICR), thus inducing an overload on adjacent anatomical structures, promoting secondary degeneration.AimTo examine biomechanical testing of cadaveric lumbar spine specimens in order to evaluate and define the ICR of intact lumbar discs.Material and MethodsTwelve cold preserved fresh human cadaveric lumbosacral spine specimens were subjected to computerized tomography (CT), magnetic resonance imaging (MRI) and biomechanical testing. Kinematic studies were performed to analyse range of movements in order to determine ICR.ResultsFlexoextension and lateral bending tests showed a positive linear correlation between the angle rotated and the displacement of the ICR in different axes.DiscussionICR has not been taken into account in any of the available literature regarding lumbar disc prosthesis. Considering our results, neither the actual ball-and-socket nor the withdrawn elastomeric nucleus models fit the biomechanics of the lumbar spine, which could at least in part explain the failure rates of the implants in terms of postoperative failed back syndrome (low back pain). It is reasonable to consider then that an implant should also adapt the equations of the movement of the intact ICR of the joint to the post-surgical ICR.ConclusionsThis is the first cadaveric study on the ICR of the human lumbar spine. We have shown that it is feasible to calculate and consider this parameter in order to design future prosthesis with improved clinical and biomechanical characteristics.

Individualized artificial titanium alloy spinal lamina with 3D printing technology

Background: Laminectomy and decompression is a common procedure for treating spine diseases. However, due to the lack of a posterior, bony braced structure, the dural sac and nerve roots can adhere to the surrounding tissues, and scar formation can occur in muscle and soft tissues. This can cause new compression post surgery, and failure of the operation. Objective: This study aimed to produce an individualized titanium alloy spine lamina using 3D printing technology, and to evaluate its effectiveness by implantation in human cadaveric spines. Methods: Six adult lumbar cadaver specimens were used, and computed tomography (CT) was used to obtain DICOM medical digital image standard data. The lumbar vertebrae structure was reconstructed by three-dimensional (3D) modeling software, and then simulated lumbar laminectomy was performed. Based on the characteristics of the original lamina, an artificial spine lamina was designed, including suture holes at the posterior ligament attachment point and a locking screw hole for fixation. A titanium alloy spine lamina was fabricated by 3D printing, and a guide plate to assist artificial lamina implantation was designed. Using the guide plated, L4 lumbar vertebrae segment laminectomy was performed on the 6 lumbar spine specimens, titanium alloy spine lamina were implanted and fixed with cortical bone trajectory screws. After implantation, CT was performed to record the length of the screw, the trajectory of the screw in the pedicle, and changes of bony spinal canal volume and anteroposterior diameter of the spinal canal. Results: The morphology of artificial spine lamina matched that of the original lamina. The artificial lamina was easy to implant, and matched the original lamina. The laminas were fixed by 12 cortical screws (diameter, 4.5 mm; median length, 34.67 ± 1.97 mm). CT scan indicated that all screws passed through the pedicle cortex by &lt; 2 mm (2 screws penetrated the inner wall). The bony canal volume of the L4 vertebral pedicle was 311.23 ± 38.17 mm2 before operation and 356.17 ± 43.11 mm2 after operation, and there was statistical difference (P &lt; 0.001). The anteroposterior diameter of spinal canal was 17.82 ± 2.03 mm before surgery and 20.67 ± 2.38 mm after surgery, and they were statistically different (P &lt; 0.001). Conclusion: An individualized artificial titanium alloy spine lamina designed and produced with 3D printing technology can be used to reconstruct the structure of the posterior spine complex after lumbar laminectomy. The artificial lamina can increase the volume of the spinal canal and provide a posterior ligament reconstruction attachment point.