Study on swelling, compression property and degradation stability of PVA composite hydrogels for artificial nucleus pulposus.

Artificial nucleus pulposus (ANP) replacement as an alternative to the treatment of cervical spondylosis aims to relieve pain and restore the normal cervical motion. In this study, the PVA/PVP and PVA/Pectin composite hydrogels (CH)s with different concentrations were prepared by the freezing-thawing process, and their performances were tested. The effect of different concentrations on both kinds of PVA CHs were evaluated and analysed. The results demonstrated that both kinds of CHs had good swelling property (¿190%), compressive stress-strain characteristic response and stable performance, and they were not easy to degrade (¡9%). The elastic modulus of the PVA/PVP CH was close to that of nucleus pulposus prosthesis, and the weight loss ratio of the PVA/PVP CH was lower than that of PVA/Pectin CH under load condition. Further, the experimental results showed that the PVA/PVP CH with 15 wt% solute and 1 wt% PVP content had the best comprehensive performance, which may provide significant advantages for use in future clinical application in replacing nucleus pulposus.

Artificial Intelligence in Spinal Imaging: Current Status and Future Directions.

Spinal maladies are among the most common causes of pain and disability worldwide. Imaging represents an important diagnostic procedure in spinal care. Imaging investigations can provide information and insights that are not visible through ordinary visual inspection. Multiscale in vivo interrogation has the potential to improve the assessment and monitoring of pathologies thanks to the convergence of imaging, artificial intelligence (AI), and radiomic techniques. AI is revolutionizing computer vision, autonomous driving, natural language processing, and speech recognition. These revolutionary technologies are already impacting radiology, diagnostics, and other fields, where automated solutions can increase precision and reproducibility. In the first section of this narrative review, we provide a brief explanation of the many approaches currently being developed, with a particular emphasis on those employed in spinal imaging studies. The previously documented uses of AI for challenges involving spinal imaging, including imaging appropriateness and protocoling, image acquisition and reconstruction, image presentation, image interpretation, and quantitative image analysis, are then detailed. Finally, the future applications of AI to imaging of the spine are discussed. AI has the potential to significantly affect every step in spinal imaging. AI can make images of the spine more useful to patients and doctors by improving image quality, imaging efficiency, and diagnostic accuracy.

Study on the process of intervertebral disc disease by the theory of continuum damage mechanics.

BACKGROUND: Recently, more and more people suffer from low back pain triggered by lumbar degenerative disc disease. The mechanical factor is one of the most significant causes of disc degeneration. This study aims to explore the biomechanical responses of the intervertebral disc, and investigate the process of disc injury by the theory of continuum damage mechanics. METHODS: A finite element model of the L4-L5 lumbar spine was developed and validated. The model not only considered changes in permeability coefficient with strain, but also included physiological factors such as osmotic pressure. Three loading conditions were simulated: (A) static loads, (B) vibration loads, (C) injury process. FINDINGS: The simulation results revealed that the facet joints shared massive stresses of the intervertebral discs, and prevented excessive lumbar spine movement. However, their asymmetrical position may have led to degeneration. The von Mises stress and pore pressure of annulus fibrosus showed significantly different trends under static loads and vibration loads. The von Mises stress of nucleus pulposus was not sensitive to vibration loads, but its pore pressure was conspicuously influenced by vibration loads. The injury first appeared at the posterior centre, and then, it gradually expanded along the edge of the intervertebral disc. With an increase in the loading steps, the damage rate of the intervertebral disc increased logarithmically. INTERPRETATION: The variation in the biomechanical performance of the intervertebral disc could be attributed to the periodic movement of internal fluids. This study might be helpful for understanding the mechanism of intervertebral disc degeneration.

The Chinese version of the family accommodation scale for obsessive-compulsive disorder self-rated: reliability, validity, factor structure, and mediating effect.

Background: Family accommodation (FA) in obsessive compulsive disorder (OCD) is a common phenomenon. Based on the cost of training interviewers and the time required to administer the scale, the Family Accommodation Scale for Obsessive-Compulsive Disorder Interviewer-Rated (FAS-IR) has been restricted to specific settings. A self-rated version of the family accommodation scale may solve these problems. The aim of this study was to examine the reliability, validity and factor structure of the Family Accommodation Scale Self-rated version (FAS-SR), and the relationship among FA, symptom severity and functional impairment. Methods: In total, 171 patients with OCD and 145 paired relatives participated in this study. The Sheehan Disability Scale (SDS), Obsessive-Compulsive Inventory Revised (OCI-R), Zung Self-Rating Depression Scale (Zung-SDS), 12-item Family Assessment Devices (FAD-12), Clinical Global Impression of Severity Scale (CGI-S), Global Assessment of Functioning (GAF), and Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) were used as tools for patients. The FAS-SR, FAS-IR, FAD-12, and the patients' symptom severity of Y-BOCS compulsion were used as tools for relatives. The psychometric properties of the FAS-SR were evaluated using Cronbach's alpha coefficient, test-retest reliability and validity. Mediation analysis was used to determine the relationship among FA, symptom severity and functional impairment. Results: A total of 97.9% of relatives of OCD patients reported at least one kind of FA behavior, and 56.6% of participants engaged in FA every day in the past week. The FAS-SR includes a three-factor structure: (1) providing reassurance and participation; (2) facilitation; and (3) modification. The scale's Cronbach's alpha and test-retest coefficients were 0.875 and 0.970, respectively. The total FAS-SR score was significantly positively associated with the Y-BOCS, FAD-12, CGI-S, FAS-IR, and SDS scores, and negatively associated with the total GAF score. FA partially mediated the relationship between symptom severity and functional impairment. Conclusion: The FAS-SR was proven to have satisfactory psychometric properties, and can play an important role in the evaluation and early intervention of OCD. This result indicates the importance of assessing symptom severity in conjunction with FA when evaluating OCD patients' functional impairment.

Biomechanical Evaluation of Transforaminal Lumbar Interbody Fusion with Coflex-F and Pedicle Screw Fixation: Finite Element Analysis of Static and Vibration Conditions.

OBJECTIVE: To investigate the biomechanics of transforaminal lumbar interbody fusion (TLIF) with interspinous process device (IPD) or pedicle screw fixation under both static and vibration conditions by the finite element (FE) method. METHOD: A validated FE model of the L1-5 lumbar spine was used in this study. This FE model derived from computed tomography images of a healthy female adult volunteer of appropriate age. Then the model was modified to simulate L3-4 TLIF. Four conditions were compared: (i) intact; (ii) TLIF combined with bilateral pedicle screw fixation (BPSF); (iii) TLIF combined with U-shaped IPD Coflex-F (CF); and (iv) TLIF combined with unilateral pedicle screw fixation (UPSF). The intact and surgical FE models were analyzed under static and vibration loading conditions respectively. For static loading conditions, four motion modes (flexion, extension, lateral bending, and axial rotation) were simulated. For vibration loading conditions, the dynamic responses of lumbar spine under sinusoidal vertical load were simulated. RESULT: Under static loading conditions, compared with intact case, BPSF decreased range of motion (ROM) by 92%, 95%, 89% and 92% in flexion, extension, lateral bending and axial rotation, respectively. While CF decreased ROM by 87%, 90%, 69% and 80%, and UPSF decreased ROM by 84%, 89%, 66% and 82%, respectively. Compared with CF, UPSF increased the endplate stress by 5%-8% in flexion, 7%-10% in extension, 2%-4% in lateral bending, and decreased the endplate stress by 16%-19% in axial rotation. Compared with CF, UPSF increased the cage stress by 9% in flexion, 10% in extension, and decreased the cage stress by 3% in lateral bending, and 13% in axial rotation. BPSF decreased the stress responses of endplates and cage compared with CF and UPSF. Compared BPSF, CF decreased the facet joint force (FJF) by 6%-13%, and UPSF decreased the FJF by 4%-12%. During vibration loading conditions, compared with BPSF, CF reduced maximum values of the FJF by 16%-32%, and vibration amplitudes by 22%-35%, while UPSF reduced maximum values by 20%-40%, and vibration amplitudes by 31%-45%. CONCLUSION: Compared with other surgical models, BPSF increased the stability of lumbar spine, and also showed advantages in cage stress and endplate stress. CF showed advantages in IDP and FJF especially during vertical vibration, which may lead to lower risk of adjacent segment degeneration. CF may be an effective alternative to pedicle screw fixation in TLIF procedures.

Investigation of Whole and Glandular Saliva as a Biomarker for Alzheimer's Disease Diagnosis.

Salivary Aß40, Aß42, t-tau, and p-tau 181 are commonly employed in Alzheimer's disease (AD) investigations. However, the collection method of these biomarkers can affect their levels. To assess the impact of saliva collection methods on biomarkers in this study, 15 healthy people were employed in the morning with six saliva collection methods. The chosen methods were then applied in 30 AD patients and 30 non-AD controls. The levels of salivary biomarkers were calculated by a specific enzyme-linked immunosorbent assay. The receiver operating characteristic was utilized to assess salivary biomarkers in AD patients. The results demonstrated that the highest levels of salivary Aß40, Aß42, t-tau, and p-tau were in different saliva collection methods. The correlations between different saliva biomarkers in the same collection method were different. Salivary Aß40, Aß42, t-tau, and p-tau had no significant association. Salivary Aß42 was higher in AD than in non-AD controls. However, p-tau/t-tau and Aß42/Aß40 had some relevance. The area under the curve for four biomarkers combined in AD diagnosis was 92.11%. An alternate saliva collection method (e.g., USS in Aß40, UPS in Aß42, t-tau, SSS in p-tau 181) was demonstrated in this study. Moreover, combining numerous biomarkers improves AD diagnosis.

Incremental Element Deletion-Based Finite Element Analysis of the Effects of Impact Speeds, Fall Postures, and Cortical Thicknesses on Femur Fracture.

The proximal femur's numerical simulation could give an effective method for predicting the risk of femoral fracture. However, the majority of existing numerical simulations is static, which does not correctly capture the dynamic properties of bone fractures. On the basis of femoral fracture analysis, a dynamic simulation using incremental element deletion (IED)-based finite element analysis (FEA) was developed and compared to XFEM in this study. Mechanical tests were also used to assess it. Different impact speeds, fall postures, and cortical thicknesses were also studied for their implications on fracture types and mechanical responses. The time it took for the crack to shatter was shorter when the speed was higher, and the crack line slid down significantly. The fracture load fell by 27.37% when the angle was altered from 15° to 135°, indicating that falling forward was less likely to cause proximal femoral fracture than falling backward. Furthermore, the model with scant cortical bone was susceptible to fracture. This study established a theoretical foundation and mechanism for forecasting the risk of proximal femoral fracture in the elderly.

Correlations of Salivary and Blood Glucose Levels among Six Saliva Collection Methods.

BACKGROUND: Saliva has been studied as a better indicator of disorders and diseases than blood. Specifically, the salivary glucose level is considered to be an indicator of diabetes mellitus (DM). However, saliva collection methods can affect the salivary glucose level, thereby affecting the correlation between salivary glucose and blood glucose. Therefore, this study aims to identify an ideal saliva collection method and to use this method to determine the population and individual correlations between salivary glucose and blood glucose levels in DM patients and healthy controls. Finally, an analysis of the stability of the individual correlations is conducted. METHODS: This study included 40 age-matched DM patients and 40 healthy controls. In the fasting state, saliva was collected using six saliva collection methods, venous blood was collected simultaneously from each study participant, and both samples were analyzed at the same time using glucose oxidase peroxidase. A total of 20 DM patients and 20 healthy controls were arbitrarily selected from the above participants for one week of daily testing. The correlations between salivary glucose and blood glucose before and after breakfast were analyzed. Finally, 10 DM patients and 10 healthy controls were arbitrarily selected for one month of daily testing to analyze the stability of individual correlations. RESULTS: Salivary glucose levels were higher in DM patients than healthy controls for the six saliva collection methods. Compared with unstimulated saliva, stimulated saliva had decreased glucose level and increased salivary flow. In addition, unstimulated parotid salivary glucose was most correlated with blood glucose level (R2 = 0.9153), and the ROC curve area was 0.9316, which could accurately distinguish DM patients. Finally, it was found that the correlations between salivary glucose and blood glucose in different DM patients were quite different. The average correlation before breakfast was 0.83, and the average correlation after breakfast was 0.77. The coefficient of variation of the correlation coefficient before breakfast within 1 month was less than 5%. CONCLUSION: Unstimulated parotid salivary glucose level is the highest and is most correlated with blood glucose level, which can be accurately used to distinguish DM patients. Meanwhile, the correlation between salivary glucose and blood glucose was found to be relatively high and stable before breakfast. In general, the unstimulated parotid salivary glucose before breakfast presents an ideal saliva collecting method with which to replace blood-glucose use to detect DM, which provides a reference for the prediction of DM.

Sleep disorders and related factors among frontline medical staff supporting Wuhan during the COVID-19 outbreak.

Sleep problems among frontline medical staff during the COVID-19 epidemic require attention. A total of 249 frontline medical staff who were recruited to support Wuhan completed this cross-sectional study. A web-based questionnaire about insomnia, depression, anxiety, and fatigue was used to assess mental health status. The prevalence of sleep disorders among frontline medical staff was 50.6%. More time spent in Wuhan and a history of insomnia, depression, anxiety, and fatigue were associated with a higher risk of insomnia. People who stayed in Wuhan for a long time with a history of insomnia, depression, anxiety, and fatigue symptoms might be at high risk of insomnia.

Biomechanical analysis of lumbar fusion with proximal interspinous process device implantation.

Lumbar spinal fusion may cause adjacent segment degeneration (ASD) in the long term. Recently, inserting an interspinous process device (IPD) proximal to the fusion has been proposed to prevent ASD. The aim of this study was to investigate the biomechanics of lumbar fusion with proximal IPD implantation (LFPI) under both static loads and whole body vibration (WBV). A previously validated finite element (FE) model of the L1-5 lumbar spine was modified to simulate L4-5 fusion. Three different IPDs (Coflex-F, Wallis and DIAM) were inserted at the L3-4 segment of the fusion model to construct the LFPI models. The intact and surgical FE models were analyzed under static loads and WBV, respectively. Under static loading conditions, LFPI decreased range of motion (ROM) and intradiscal pressure (IDP) at the transition segment L3-4 compared with the fusion case. At the segment (L2-3) adjacent to the transition level, LFPI induced higher motion and IDP than rigid fusion. Under WBV, vibration amplitudes of the L3-4 IDP and L4-5 facet joint force (FJF) decreased by more than 54.3% after surgery. The LFPI model with the DIAM system offered the most comparable biomechanics to the intact model under static loads, and decreased the dynamic responses of the L4-5 FJF under WBV. The LFPI model with the Wallis and Coflex-F systems could stabilize the transition segment, and decrease dynamic responses of the L3-4 IDP. The DIAM system may be more suitable in LFPI.

Sleep disorders and related factors among frontline medical staff supporting Wuhan during the COVID-19 outbreak.

Sleep problems among frontline medical staff during the COVID-19 epidemic require attention. A total of 249 frontline medical staff who were recruited to support Wuhan completed this cross-sectional study. A web-based questionnaire about insomnia, depression, anxiety, and fatigue was used to assess mental health status. The prevalence of sleep disorders among frontline medical staff was 50.6%. More time spent in Wuhan and a history of insomnia, depression, anxiety, and fatigue were associated with a higher risk of insomnia. People who stayed in Wuhan for a long time with a history of insomnia, depression, anxiety, and fatigue symptoms might be at high risk of insomnia.

Biomechanical evaluation of anterior lumbar interbody fusion with various fixation options: Finite element analysis of static and vibration conditions.

BACKGROUND: Anterior lumbar interbody fusion combined with supplementary fixation has been widely used to treat lumbar diseases. However, few studies have investigated the influence of fixation options on facet joint force and cage subsidence. The aim of this study was to explore the biomechanical performance of anterior lumbar interbody fusion with various fixation options under both static and vertical vibration loading conditions. METHODS: A previously validated finite element model of the intact L1-5 lumbar spine was employed to compare five conditions: (1) Intact; (2) Fusion alone; (3) Fusion combined with anterior lumbar plate; (4) Fusion combined with Coflex-F fixation; (5) Fusion combined with bilateral pedicle screw fixation. The models were analyzed under static and vertical vibration loading conditions respectively. FINDINGS: Bilateral pedicle screws provided highest stability at surgical level. Applying supplementary fixation diminished the dynamic responses of lumbar spine. Compared with anterior lumbar plate and Coflex-F device, bilateral pedicle screws decreased the stress responses of the endplates and cage under both static and vibration conditions, while increased the facet joint force at adjacent levels. As for comparison between Coflex-F device and anterior lumbar plate, results showed a similarity in biomechanical performance under static loading, and a slightly higher dynamic response of the latter under vertical vibration. INTERPRETATION: The biomechanical performance of lumbar spine was significantly influenced by the variation of fixations under both static and vibration conditions. Bilateral pedicle screws showed advantages in stabilizing surgical segment and relieving cage subsidence, but may increase the facet joint force at adjacent levels.

Translation and Cross-Cultural Adaptation of the Family Accommodation Scale for Obsessive-Compulsive Disorder Into Chinese.

Family accommodation is a phenomenon that has been associated with worse treatment outcome of patients with obsessive-compulsive disorder (OCD) and greater severity of symptoms and levels of functional impairment. Yet, there are no Chinese scales to assess family accommodation in OCD among family members. The present study aimed to illustrate the steps of translation and cross-cultural adaptation of the Chinese versions of the Family Accommodation Scale (FAS). After obtaining authorization of the developers, the Chinese versions of the FAS were translated and adapted from the English versions based on a standard protocol, following six steps: forward translation, pilot administration, language adjustment and cultural adaptation, back-translation, review and minor edit, and final approval of the developer. Thirty-five pairs of patients and corresponding relatives with different education levels were administered the FAS in the pretest stage. This study found that the semantic, idiomatic, and conceptual equivalence were obtained between the Chinese versions and original English scales, and the Chinese versions of FAS were well translated and culturally adapted. We also found that the Chinese versions of the FAS can be easily understood by people of different socioeconomic statuses.

Psychometric properties of the Chinese version of the family accommodation scale for obsessive-compulsive disorder interviewer-rated.

BACKGROUND: Family accommodation (FA) in obsessive-compulsive disorder (OCD) means that the relatives of patients are involved in, help or facilitate patients' ritual behaviors and avoidance, which is a frequent occurrence and underresearched phenomenon in China. Recent studies have suggested that FA is adversely associated with treatment response, contradictory to the goal of cognitive behavior therapy, a contributor to the maintenance of symptoms and increased symptom severity, and associated with low levels of family and social functioning. There is increasing interest and focus on establishing a family-based intervention for OCD treatment based on the inclusion of relatives by decreasing FA. The present study explored the psychometric properties of the Chinese version of the Family Accommodation Scale for OCD Interviewer-Rated (FAS-IR). METHOD: A total of 109 patients with OCD and 91 primary relatives were assessed in corresponding patient and family measures, and the FAS-IR was administered to relatives by trained interviewers. RESULTS: More than 90% of the relatives accommodated patients' symptoms with at least one kind of FA behavior over the previous week, and the incidence of extreme or everyday routines was as high as 59.3%. Exploratory factor analysis demonstrated two-factor structure for the whole scale, including (1) modification and facilitation, and (2) participation. Cronbach's alpha was 0.798 for the whole scale, and the interrater and test-retest reliability coefficients were 0.835 (95%CI: 0.603-0.937) and 0.882 (95%CI: 0.685-0.959), respectively. Convergent validity was supported in exploring FA and was associated with symptom severity, level of functional impairment and family functioning related to OCD. The FA was not significantly correlated with depressive symptoms rated by the patients, as evidence of acceptable divergent validity. There was no significant difference in FA total score based on patient gender, patient age, or relationship with patients. CONCLUSIONS: The Chinese version of the FAS-IR demonstrated excellent psychometric properties for assessing the degree of FA, suggesting that it is a useful and valuable instrument in clinical and research settings.

[A review on the current state of ball-on-socket type artificial lumbar disc prosthesis].

Total lumbar disc replacement is an alternative to interbody fusion for the effective treatment of symptomatic degenerative disc disease. This paper reviewed the history of ball-on-socket type artificial lumbar disc (ALD) prosthesis, which is a typical ALD prosthesis and summarized the ALD prosthesis research progress, according to different materials such as metal-on-metal, metal-on-polymer, and polymer-on-polymer prosthesis. The structural design factors of ball-on-socket type ALD prosthesis were analyzed and its prospect of development was also presented. The purpose of this paper is to provide a theoretical reference for the design of the ball-on-socket ALD prosthesis by reviewing the current state of ball-on-socket type ALD prosthesis.

Biomechanical Analysis of Different Lumbar Interspinous Process Devices: A Finite Element Study.

BACKGROUND: Recently, interspinous stabilization with the interspinous process device (IPD) has become an alternative to treat lumbar spinal stenosis. The biomechanical influence of different design features of IPDs on intradiscal pressure (IDP) and facet joint force (FJF) has not been fully understood. The aim of this study was to investigate the biomechanical performance of different IPDs using finite element (FE) method. METHODS: A FE model of the L1-5 segments was developed and validated. Four surgical FE models were constructed by inserting different implants at the L3-4 segment (Coflex-F, DIAM, Wallis, and pedicle screw system). The 4 motion modes were simulated. RESULTS: The IPDs decreased range of motion (ROM) at the surgical level substantially in flexion and extension, but little influence was found in lateral bending and torsion. Compared with the DIAM and Wallis devices, the Coflex-F device showed advantages in stabilizing the surgical level, especially in flexion and extension, while it increased FJF at adjacent levels by 26%-27% in extension. Among the 3 IPDs, the DIAM device exhibited the most comparable ROM, IDP, and FJF at adjacent levels compared with the intact lumbar spine. The influence of the Wallis device was between that of the Coflex-F and DIAM devices. CONCLUSIONS: Compared with rigid fixation, the IPDs demonstrated less compensation at adjacent levels in terms of ROM, IDP, and FJF, which may lower the incidence of adjacent segment degeneration in the long term.

Highly Effective Bone Fusion Induced by the Interbody Cage Made of Calcium Silicate/Polyetheretherketone in a Goat Model.

Interbody fusion surgery is often used to settle matters such as degenerative disc disease or disc herniation in clinical orthopedics. Considering the deficiencies of the current treatment methods, we developed an interbody fusion cage made of calcium silicate (CS)/polyetheretherketone (PEEK) and hoped that the bioactive cage could exhibit great fusion ability and maintain stable mechanical function. In the goat model of cervical interbody fusion, the CS/PEEK cage showed stronger interbody fusion at 12 and 26 weeks compared with pure PEEK cage based on the X-ray analysis. The micro-CT scanning and analysis indicated that the CS/PEEK cage induced more new bone ingrowth than the PEEK cage and led to nearly complete interbody fusion at 26 weeks. Moreover, the CS/PEEK group showed excellent mechanical stability and stiffness as evaluated by the spine kinematic assay at the time points. The histological assessment showed the rapid osseointegration and mineralized bone formation around the CS/PEEK cage. This study confirmed that the bioactive CS/PEEK cage is capable of inducing highly effective bone fusion and has high potential to be used in the clinics of spine surgery.

Biomechanical evaluation of four surgical scenarios of lumbar fusion with hyperlordotic interbody cage: A finite element study.

BACKGROUND: Lumbar spinal fusion in the interbody space is augmented with interbody fusion cages to provide structural support while arthrodesis occurs. Subsidence is a serious complication of interbody fusion. However, the biomechanical influence of anterior longitudinal ligament (ALL) and pedicle screws on subsidence has not been fully understood. OBJECTIVE: To investigate biomechanical effects of the hyperlordotic cages in different surgical conditions using finite element analysis. METHODS: Four surgical finite element (FE) models were constructed by inserting 15 degree lordosis cage at the L3-L4 disc space. The four surgical conditions were ALL intact (M1), ALL resected (M2), ALL intact and bilateral pedicle screws (M3), and ALL resected and bilateral pedicle screws (M4). Follow loads were applied at the L2 vertebral body while the inferior surface of L5 was fixed. FEA was implemented to simulate the four motion modes and biomechanical properties of four fusion scenarios with hyperlordotic interbody cage were compared. RESULTS: The range of motion (ROM) and facet joint force (FJF) at L3-L4 decreased significantly after fusion during all the motion modes. The cage stress and endplate stress at L3-L4 increased significantly after fusion during all the motion modes. The cage stress and endplate stress at L3-L4 for M3 and M4 were smaller than that for M1 and M2 during all the motion modes. The FJF at L3-L4 for M3 and M4 were smaller than that for M1 and M2 during extension, bending, and rotation. CONCLUSIONS: ALL has little effect on the biomechanics after lumbar fusion with hyperlordotic interbody cage. The bilateral pedicle screws significantly decreased the stress in cage, stress in endplate at L3-L4, and lowered facet contact force except for flexion mode. The implication is that the supplemental bilateral pedicle screws are recommended whether or not the ALL is resected.

[Research progress on mechanical performance evaluation of artificial intervertebral disc].

The mechanical properties of artificial intervertebral disc (AID) are related to long-term reliability of prosthesis. There are three testing methods involved in the mechanical performance evaluation of AID based on different tools: the testing method using mechanical simulator, in vitro specimen testing method and finite element analysis method. In this study, the testing standard, testing equipment and materials of AID were firstly introduced. Then, the present status of AID static mechanical properties test (static axial compression, static axial compression-shear), dynamic mechanical properties test (dynamic axial compression, dynamic axial compression-shear), creep and stress relaxation test, device pushout test, core pushout test, subsidence test, etc. were focused on. The experimental techniques using in vitro specimen testing method and testing results of available artificial discs were summarized. The experimental methods and research status of finite element analysis were also summarized. Finally, the research trends of AID mechanical performance evaluation were forecasted. The simulator, load, dynamic cycle, motion mode, specimen and test standard would be important research fields in the future.

Comparison of Multilevel Cervical Disc Replacement and Multilevel Anterior Discectomy and Fusion: A Systematic Review of Biomechanical and Clinical Evidence.

OBJECTIVE: The aim of this study was to comprehensively compare the clinical and biomechanical efficiency of anterior cervical discectomy and fusion (ACDF) with anterior cervical disc replacement (ACDR) for treatment of multilevel cervical disc disease using a meta-analysis and systematical review. METHODS: A literature search was performed using PubMed, MEDLINE, EMBASE, and the Cochrane Library for articles published between January 1960 and December 2017. Both clinical and biomechanical parameters were analyzed. Statistical tests were conducted by Revman 5.3. Nineteen studies including 10 clinical studies and 9 biomechanical studies were filtered out. RESULTS: The pooled results for clinical efficiency showed that no significant difference was observed in blood loss (P = 0.09; mean difference [MD], 7.38; confidence interval [CI], -1.16 to 15.91), hospital stay (P = 0.33; MD, -0.25; CI, -0.76 to 0.26), Japanese Orthopaedic Association scores (P = 0.63; MD, -0.11; CI, -0.57 to 0.34), visual analog scale (P = 0.08; MD, -0.50; CI, -1.06 to 0.05), and Neck Disability Index (P = 0.33; MD, -0.55; CI, -1.65 to 0.56) between the 2 groups. Compared with ACDF, ACDR did show increased surgical time (P = 0.03; MD, 31.42; CI, 2.71-60.14). On the other hand, ACDR showed increased index range of motion (ROM) (P < 0.00001; MD, 13.83; CI, 9.28-18.39), lower rates of adjacent segment disease (ASD) (P = 0.001; odds ratio [OR], 0.27; CI, 0.13-0.59), complications (P = 0.006; OR, 0.62; CI, 0.45-0.87), and rate of subsequent surgery (P < 0.00001; OR, 0.25; CI, 0.14-0.44). As for biomechanical performance, ACDR maintained index ROM and avoided compensation in adjacent ROM and tissue pressure. CONCLUSIONS: Multilevel ACDR may be an effective and safe alternative to ACDF in terms of clinical and biomechanical performance. However, further multicenter and prospective studies should be conducted to obtain a stronger and more reliable conclusion.