Biomechanics Of Cervical Spine Research Articles

Changes in canal diameter and cervical lordosis in patients who underwent en-bloc laminoplasty for the treatment of cervical spinal stenosis

Objective: Cervical spinal canal-expanding laminoplasty has been recognized as an alternative to cervical laminectomy, especially in multilevel cervical myelopathy due to spinal stenosis. This study aimed to determine the effects of En-block laminoplasty on cervical sagittal balance, cervical spine biomechanics and whether it is sufficient to preserve cervical canal diameter and lordosis and whether it causes additional lordosis or kyphosis in cases of cervical narrow spinal canal. Methods: Thirty-eight cervical narrow canal patients operated on between 2008 and 2020 were retrospectively evaluated and the results of 24 laminoplasty patients were evaluated. Spinal tomography results for the evaluation of canal diameter changes and X-ray results for cervical sagittal balance evaluation were compared with each other in the early postoperative period and 3 years later. For cervical lordosis assessment, Cobb and C2-C7sagital vertical axis measurements were performed using the PACS system. Results: Fifteen patients were male and 9 were female. The mean age was 65.55±11.56 years (min-max: 58-84) and the mean follow-up period was three years. Two patients had one level stenosis, 4 had two levels, 7 had three levels, and 11 had four or more levels. Radiculopathy was present in 17 patients (71.8%) and myelopathy in 7 patients (29.1%). There was no statistically significant difference in the frequency of myelopathy/radiculopathy between genders. When all distances were considered, no statistical difference was observed in the early postoperative period (median ten days) and late postoperative period (median 3 years) in terms of canal diameters. No measurement value could be obtained for any level diagnosed as restenosis or requiring reoperation. Loss of lordosis was measured in only one patient. Otherwise, lordosis was preserved in all cases at late conversion. Conclusions: The results of our study showed that en-block laminoplasty after the cervical narrow spinal canal was sufficient to maintain the cervical canal diameter in the long term with appropriate patient and surgical technique.

The effect of suboccipital muscle dysfunction on the biomechanics of the upper cervical spine: a study based on finite element analysis

ObjectiveMuscle dysfunction caused by repetitive work or strain in the neck region can interfere muscle responses. Muscle dysfunction can be an important factor in causing cervical spondylosis. However, there has been no research on how the biomechanical properties of the upper cervical spine change when the suboccipital muscle group experiences dysfunction. The objective of this study was to investigate the biomechanical evidence for cervical spondylosis by utilizing the finite element (FE) approach, thus and to provide guidance for clinicians performing acupoint therapy.MethodsBy varying the elastic modulus of the suboccipital muscle, the four FE models of C0-C3 motion segments were reconstructed under the conditions of normal muscle function and muscle dysfunction. For the two normal condition FE models, the elastic modulus for suboccipital muscles on both sides of the C0-C3 motion segments was equal and within the normal range In one muscle dysfunction FE model, the elastic modulus on both sides was equal and greater than 37 kPa, which represented muscle hypertonia; in the other, the elastic modulus of the left and right suboccipital muscles was different, indicating muscle imbalance. The biomechanical behavior of the lateral atlantoaxial joint (LAAJ), atlanto-odontoid joint (ADJ), and intervertebral disc (IVD) was analyzed by simulations, which were carried out under the six loadings of flexion, extension, left and right lateral bending, left and right axial rotation.ResultsUnder flexion, the maximum stress in LAAJ with muscle imbalance was higher than that with normal muscle and hypertonia, while the maximum stress in IVD in the hypertonic model was higher than that in the normal and imbalance models. The maximum stress in ADJ was the largest under extension among all loadings for all models. Muscle imbalance and hypertonia did not cause overstress and stress distribution abnormalities in ADJ.ConclusionMuscle dysfunction increases the stress in LAAJ and in IVD, but it does not affect ADJ.

Laminoplasty Versus Laminectomy and Posterior Fusion for Cervical Myelopathy: A Meta-analysis of Radiographic and Clinical Outcomes.

Meta-analysis. This meta-analysis investigates the outcomes of laminoplasty (LP) and laminectomy with fusion (LF) to guide effective patient selection for these two procedures. While LF traditionally offers the ability for excellent posterior decompression, it may alter cervical spine biomechanics and increase the risk of adjacent segment degeneration. LP aims to preserve the natural kinematics of the spine but has not been universally accepted, and may be associated with inadequate decompression, neck pain, and recurrent stenosis. PubMed, Cochrane, and Google Scholar (Pages 1-20) were searched up until March 2024. The outcomes studied were surgery-related outcomes (operating room (OR) time, estimated blood loss (EBL), and length of stay (LOS)), adverse events (overall complications, C5 palsy, and reoperations), radiographic outcomes (cervical lordosis (CL), cervical sagittal vertical axis (cSVA), and T1 slope angle (T1SA)), and patient-reported outcome measures (PROMs) (Neck Disability Index (NDI), Visual Analog Scale (VAS) for neck pain, and Japanese Orthopaedic Association (JOA)). Twenty-two studies were included in this meta-analysis, of which 19 were retrospective studies, two were prospective non-randomized studies, and one was a randomized controlled trial. A total of 2,128 patients were included, with 1,025 undergoing LP and 1,103 undergoing LF. LP patients experienced significantly shorter OR time (P=0.009), less EBL (P=0.02), a lower rate of overall complications (P<0.00001) and C5 palsy (P=0.003), a lower T1SA (P=0.02), and a lower NDI (P=0.0004). No significant difference was observed in the remaining outcomes. This meta-analysis demonstrates that for cervical myelopathy, LP has the benefits of shorter OR time, less EBL, and reduced incidence of C5 palsy as well as overall complication rate. Given these findings, LP remains an important surgical option with a favorable complication profile in patients with cervical myelopathy, although careful patient selection is still paramount in choosing the right procedure for individual patients.

Effects of acupuncture at myofascial trigger points combined with sling exercise therapy on clinical recovery and cervical spine biomechanics in patients with cervical spondylotic radiculopathy

Objective: This research aimed to ascertain the effects of acupuncture at myofascial trigger points (MTrPs) in combination with sling exercise therapy (SET) on the clinical recovery and cervical spine biomechanics in patients with cervical spondylotic radiculopathy (CRS). Methods: Eighty patients with CSR were divided into Group A and Group B. Group A was treated with acupuncture at MTrPs, and Group B was treated with acupuncture at MTrPs combined with SET. The cervical spine function, pain level, cervical spine biomechanics and the occurrence of complications were compared between the two groups before and after treatment. Results: After treatment, the Japanese Orthopaedic Association scores, Clinical Assessment Scale for Cervical Spondylosis scores, cervical forward flexion angle, posterior extension angle, left lateral flexion angle, right lateral flexion angle, left lateral rotation angle, and right lateral rotation angle of the Group B were raised, and the Neck Disability index, Visual Analogue Scale scores, and Neck Pain Questionnaire scores were reduced versus those of the Group A. The difference in complication rates between the two groups was not of statistical significance. Conclusion: Acupuncture at MTrPs combined with SET promotes functional recovery of the cervical spine, reduces pain, and improves cervical spine biomechanics in patients with CRS.

Estimation of Cervical Spinal Loading and Internal Motion at Adjacent Segments after C5–C6 Fusion Using a Musculoskeletal Multi-Body Dynamics Model during the Head Flexion–Extension Movement

Cervical spinal fusion is the standard of care for treating intractable spinal diseases. However, frequent adjacent segment disease (ASD) has recently drawn a great deal of attention among clinicians and researchers. At present, the etiology of ASD remains controversial. The investigation of cervical spine biomechanics after fusion may contribute to understanding the causes of ASD. In the present study, a cervical spinal musculoskeletal fusion model, with multi-body dynamics method, was established. Dynamic head flexion–extension movements were simulated for both a fusion subject and a normal subject. The cervical spinal loading pattern, load sharing ratios, and translations of instant centers of the rotation at adjacent segments were then predicted. The average intervertebral compressive forces, shear forces, and facet joint forces against the intervertebral angle were also obtained. By comparison, some obvious differences in cervical spinal loading patterns were found between the fusion subject and the normal subject. Fusion surgery would alter the postoperative biomechanical surrounding of the cervical spine, especially the adjacent segments. These changes might affect the intervertebral disc-bearing capacity, and even weaken the physiological structure. From a purely biomechanical perspective, the cervical spinal fusion model can contribute to comprehending the etiology of ASD after spinal fusion.

192 Effect of Helmet on Cervical Spine Biomechanics in Rear Impact Scenario (Whiplash)

INTRODUCTION: Rear impact (whiplash) is a common scenario has been studied previously by subjecting the head-neck complex under postero-anterior acceleration. There is a lack of studies investigating the effect of helmet on cervical spine biomechanics despite its common use in military and competitive automotive environments. METHODS: We developed a finite element model of the head-neck complex simulating the three spinal columns with layered intervetebral discs and ligaments. This was then validated against a cadaver (head to T1) model which was fixated to a sled on linear rails with a rear pendulum that simulated rear impact scenario. Standard-issue US Military Combat helmets in small, medium, large sizes were modeled and mounted on the finite element model. 1.8 m/s and 2.6 m/s velocity profiles were simulated and the range of motion at each functional spinal unit from C2-3 to C7-T1 was measured. RESULTS: Segmental motions were measured over 120 ms for all scenarios. 2.6 m/s vector resulted in peak acceleration of 3.5 g, and 1.8 m/s resulted in 2.5 g. Helmet use increased the range of motion at all segments from C2-3 to C7-T1. The greatest range of motion occurred at C5-6, followed by C6-7 and C7-T1. Greatest percentage increase in motion occurred at C2-3 followed by C5-6. Increasing helmet size resulted in increasing motion at all spinal segments. CONCLUSIONS: Helmet use, although protective for the cranium, significantly increases the motion at all spinal segments, especially C2-3 and C5-7, in a rear impact scenario (whiplash). Increasing helmet size results in greater motion change at all cervical spine segments. This is important to consider when designing the helmet and determining the need for additional head-mounted gear in both military and competitive automotive environments.

Comparative biomechanical analyses of lower cervical spine post anterior fusion versus intervertebral disc arthroplasty: A geometrically patient-specific poroelastic finite element investigation.

Background/ObjectiveThe optimal surgical technique for the treatment of cervical degenerative disc disease (CDDD) towards decreasing the risk of adjacent segment disease (ASD) remains elusive. This study aimed to comparatively investigate the biomechanics of the lower cervical spine following fusion (ACDF) and artificial disc arthroplasty (Bryan® and Prestige LP®) using a validated geometrically patient-specific poroelastic finite element modeling (FEM) approach.MethodsTen subject-specific pre-operative models were developed and validated based on a FEM approach. Poroelastic models were then constructed using post-operation images for three different treatment scenarios: ACDF; Prestige LP® and Bryan® artificial discs at the C5–C6 level. The biomechanical responses at both surgical and adjacent spinal levels were studied subject to static and cyclic loading.ResultsPostoperatively, greater range of motion (ROM), higher annulus fibrosus stress and strain values, and increased disc height and fluid loss at the adjacent levels were detected post ACDF, as compared with pre-op as well as artificial disc arthroplasty. The facet joint forces were larger for the Prestige LP® disc, particularly during extension. The lowest values in disc height and fluid exchange were observed in the Bryan® artificial disc arthroplasty models.ConclusionBiomechanical analyses revealed that ACDF poses the highest potential risk for adjacent disc degeneration. The artificial discs investigated here (Prestige LP® and Bryan®) not only preserved motion at the instrumented level, but also sustained the pre-op ROM and decreased the intradiscal pressure (IDP) and facet joint forces (FJFs) at adjacent levels, particularly during flexion/extension. The Bryan® artificial disc demonstrated the most efficacy in maintaining the natural poroelastic characteristics of adjacent discs.The translational potential of this articleThis study provided a technique for clinicians to use quantitative data towards subject-specific evaluation to comparatively evaluate the impact of ACDF and disc arthroplasty using two types of artificial discs on the biomechanics of the cervical spine. It confirms differences in the poroelastic characteristics of adjacent discs for different fixation techniques, and reveals the advantage of artificial discs with a flexible core for decreasing the risk of ASD.

Personalised gravitational loading of the cervical spine from biplanar X-rays for asymptomatic and clinical subjects in neutral standing position

BackgroundAs a leading cause of disability with a high societal and economic cost, it is crucial to better understand risk factors of neck pain and surgical complications. Getting subject-specific external loading is essential for quantifying muscle forces and joint loads but it requires exertion trials and load cells which are uncommon in clinical settings. MethodsThis paper presents a method to compute the gravitational loading at four levels of the cervical spine (C3C4, C4C5, C5C6, C6C7) in neutral standing position from biplanar radiographs exclusively. The resulting load was decomposed in local disc frames and its components were used to compare different populations: 118 asymptomatic subjects and 46 patients before and after surgery (anterior cervical discectomy and fusion or total disc replacement). Comparisons were performed at C6C7 and the upper level adjacent to surgery. FindingsSignificant changes in gravitational loading were observed with age in healthy subjects as well as in patients after surgery and have been associated with changes in posture. InterpretationThis approach quantifies the influence of postural changes on gravitational loading on the cervical spine. It represents a simple way to obtain necessary input for muscle force quantification models in clinical routine and to use them for patient evaluation. The study of the subsequent subject-specific spinal loading could help further the understanding of cervical spine biomechanics, degeneration mechanisms and complications following surgery.

Investigation into Cervical Spine Biomechanics Following Single, Multilevel and Hybrid Disc Replacement Surgery with Dynamic Cervical Implant and Fusion: A Finite Element Study.

Cervical fusion has been a standard procedure for treating abnormalities associated with the cervical spine. However, the reliability of anterior cervical discectomy and fusion (ACDF) has become arguable due to its adverse effects on the biomechanics of adjacent segments. One of the drawbacks associated with ACDF is adjacent segment degeneration (ASD), which has served as the base for the development of dynamic stabilization systems (DSS) and total disc replacement (TDR) devices for cervical spine. However, the hybrid surgical technique has also gained popularity recently, but its effect on the biomechanics of cervical spine is not well researched. Thus, the objective of this FE study was to draw a comparison among single-level, bi-level, and hybrid surgery with dynamic cervical implants (DCIs) with traditional fusion. Reductions in the range of motion (ROM) for all the implanted models were observed for all the motions except extension, compared to for the intact model. The maximum increase in the ROM of 42% was observed at segments C5–C6 in the hybrid DCI model. The maximum increase in the adjacent segment’s ROM of 8.7% was observed in the multilevel fusion model. The maximum von Mises stress in the implant was highest for the multilevel DCI model. Our study also showed that the shape of the DCI permitted flexion/extension relatively more compared to lateral bending and axial rotation.

Total disc replacement alters the biomechanics of cervical spine based on sagittal cervical alignment: A finite element study

IntroductionThe correlation between cervical alignment and clinical outcome of total disc replacement (TDR) surgery is arguable. We believe that this conflict exists because the parameters that influence the biomechanics of the cervical spine are not well understood, specifically the effect of TDR on different cervical alignments.Methods:A validated osseo-ligamentous model from C2-C7 was used in this study. The C2-C7 Cobb angle of the base model was modified to represent: lordotic (−10°), straight (0°), and kyphotic (+10°) cervical alignment. The TDR surgery was simulated at the C5-C6 segment. The range of motion (ROM), intradiscal pressure, annular stresses, and facet loads were computed for all the models.Results:The ROM results demonstrated kyphotic alignment after TDR surgery to be the most mobile when compared to intact base model (41% higher in flexion–extension, 51% higher in lateral bending, and 27% higher in axial rotation) followed by straight and lordotic alignment, respectively. The annular stresses for the kyphotic alignment when compared to intact base model were higher at the index level (33% higher in flexion–extension and 48% higher in lateral bending) compared to other alignments. The lordotic model demonstrated higher facet contact forces at the index level (75% higher in extension than kyphotic alignment, 51% higher in lateral bending than kyphotic alignment, and 78% higher in axial rotation than kyphotic alignment) when compared among the three alignment models.Conclusion:Preoperative cervical alignment should be an integral part of surgical planning for TDR surgery as different cervical alignments may significantly alter the postsurgical outcomes.

Prevalence of Cervical Spondylolisthesis in the Sagittal Plane Using Radiographic Imaging in a Pediatric Population: A Cross Sectional Analysis of Vertebral Subluxation.

Cervical Spondylolisthesis (CS) in children is under-studied. This cross-sectional study reports the CS prevalence in children. Subjects were selected from a private practice. Inclusion criteria: 0-17 years of age; documented demographics and health complaints; neutral lateral cervical (NLC) radiographs; and CS. Exclusion criteria: pseudosubluxation. 342 NLC radiographs were analyzed. 73 (21.3%) had CS greater than 2.0 mm. 42 (57.5%) had no musculoskeletal complaints. 8 (2.3%) had the presence of a CS greater than 3.5 mm. 5 (62.5%) had no musculoskeletal complaints. Pediatric populations endure various traumas. Pediatric cervical spine biomechanics has an increased risk of upper cervical spine injury. Regular spinal radiographic exams may help identify serious spinal conditions in their pre-symptomatic state. CS in pediatric populations is under-studied. CS is present in children and adolescents with and without symptoms.

Load-Sharing and Kinematics of the Human Cervical Spine Under Multi-Axial Transverse Shear Loading: Combined Experimental and Computational Investigation.

The cervical spine experiences shear forces during everyday activities and injurious events yet there is a paucity of biomechanical data characterizing the cervical spine under shear loading. This study aimed to (1) characterize load transmission paths and kinematics of the subaxial cervical spine under shear loading, and (2) assess a contemporary finite element cervical spine model using this data. Subaxial functional spinal units (FSUs) were subjected to anterior, posterior, and lateral shear forces (200 N) applied with and without superimposed axial compression preload (200 N) while monitoring spine kinematics. Load transmission paths were identified using strain gauges on the anterior vertebral body and lateral masses and a disc pressure sensor. Experimental conditions were simulated with cervical spine finite element model FSUs (GHBMC M50 version 5.0). The mean kinematics, vertebral strains, and disc pressures were compared to experimental results. The shear force-displacement response typically demonstrated a toe region followed by a linear response, with higher stiffness in anterior shear relative to lateral and posterior shear. Compressive axial preload decreased posterior and lateral shear stiffness and increased initial anterior shear stiffness. Load transmission patterns and kinematics suggest the facet joints play a key role in limiting anterior shear while the disc governs motion in posterior shear. The main cervical spine shear responses and trends are faithfully predicted by the GHBMC cervical spine model. These basic cervical spine biomechanics and the computational model can provide insight into mechanisms for facet dislocation in high severity impacts, and tissue distraction in low severity impacts.

Prevalence and Levels of Forward Head Posture among School Going Children

Introduction: Exposure of overloaded bag packs and early usage of digital gadgets amongst school going children alters the cervical spine posture. The present research work intends to study the prevalence of forward head posture in school going children. The study also elucidates the ranges to consider for mild, moderate and severe forward head posture prevalence. Methods: A total of 100 school students (50 males and 50 females) were recruited for cross-sectional study. Assessment of forward head posture was done using plumb line. The students were made to stand at a point marked 25 cm distance away from the plumb line. The researcher, from the side view, using a meter scale, measured the distance between the tragus of the ear and plumb line and record it. The weight of the school bag was measured using the weighing machine and the time for which gadgets were used was recorded as per the subject/parents feedback. Results: The mean values for age, height, weight and BMI are 13.67 ± 0.55 years, 158.56 ± 7.71 cms, 46.47 ± 10.50 kgs and 18.40 ± 3.48 kg /m2 respectively. The mean values for gadgets time use, distance plumb line and weight bag are 130.50 ± 67.07 min, 1.96 ± 1.19 cm and 4.32 ± 1.70 kgs respectively. About ~27% children having mild or no FHP (less than or equal to 1 cm), ~37% children having moderate FHP (ranging between 1.01 cm to 2.49 cm) and ~36% children found to have severe FHP (more than or equal to 2.5 cm). Conclusion: The study showed that the FHP is developing at early stage in the school going children and it has the potential of altering cervical spine biomechanics. Early screening is much essential aspect to prevent FHP. The ergonomic based awareness programs should be organized to sensitize children about the right posture and to indulge them in physical activity.

Cervical Spine Cord Injury Associated with Klippel-Feil Syndrome: A Case Report

Background: Klippel Feil syndrome (KFS) is a congenital malformation characterised by the presence of, at least, one fused cervical segment and results from faulty segmentation along the embryo’s developing axis during weeks 3 - 8 of gestation. The KFS increases the risk for spinal cord injury after minor trauma as a result of the disturbance of the biomechanics of the cervical spine. Persons with KFS often have associated congenital anomalies. Aim: The purpose of this study was to show the surgical management difficulties of this pathology in a low income country such as Senegal and to make a review of the literature. Case presentation: A 32-year-old man developed a tetraparesis secondary to a fall from his height while carrying a bag of rice on his head. Radiological explorations revealed fusedC2-C3 and C4-C5 vertebral bodies with a C3-C4 disc herniation associated to a spine contusion. The patient underwent surgical removal of the herniated disc via an anterior approach followed by interbody fusion and anterior plating. A complete recovery was noted at 4 months follow-up. Conclusion: Understanding of the cervical spine biomechanics of Klippel-Feil anomaly may allow an optimal management of patients. Patients with KFS should be warned of the increased risk of spinal cord injury after a low velocity trauma. Timing for surgery should be shortened.

A graphical guide for constructing a finite element model of the cervical spine with digital orthopedic software

Three-dimensional (3D) reconstruction and finite element analysis (FEA) have been extensively used to simulate cervical biomechanics. However, instructive articles providing full descriptions for operating Mimics software, Geomagic software, and FEA are rare in the literature. This omission has hindered research and development related to cervical spine biomechanics. Herein, we expound a detailed and easily understandable protocol for performing a digital biomechanics study which may facilitate a better understanding of the internal anatomy mechanics and the investigation of novel screw fixation techniques. We describe step-by-step instructions for use of Mimics and Geomagic software in FEA, along with a concise literature review. The key procedures of digital FEA stepwise instruction are presented, accompanied by a brief but complete report on the computed tomography (CT) imaging data for establishing the final finite element model. Previous publications regarding the commonly used software are also reviewed and discussed. Each piece of software performs a specific function for digital FEA establishment and each has its inherent shortcomings, making it is necessary to combine the software to leverage the advantages of each in order to best serve finite element research. For reasons of brevity, this study only provides an illustrative report on a small key part of finite element research in the cervical spine. These stepwise instructions can guide orthopedic researchers in conducting FEA studies in digital cervical biomechanics.

The Biomechanical Response of the Lower Cervical Spine Post Laminectomy: Geometrically-Parametric Patient-Specific Finite Element Analyses

This study aimed to investigate the biomechanical impact of laminectomy on cervical intersegmental motion and load sharing using a parametric patient-specific finite element (FE) model towards providing clinicians with a viable quantitative tool for informed decision-making and improved surgical planning. Ten subject-specific nonlinear osteo-ligamentous cervical spine (C3–C7) FE models were developed using X-ray image-based algorithms. The models were used to evaluate the effect of laminectomy on lower cervical spine biomechanics for two-level (C3–C4) and three-level (C3–C5) laminectomy procedures. The average cervical spine ranges of motion (ROM) for the pre-op models were 24.09 (± 8.65), 18.08 (± 7.48), 27.86 (± 6.82), and 33.18 (± 10.81) degrees, during flexion, extension, lateral bending, and axial rotation, respectively, in alignment with the literature. Post laminectomy increased the intersegmental ROM, disc stress, and intradiscal pressure at the upper cervical levels during sagittal plane motion and axial rotation, while the lower levels experienced the opposite trend, as compared with intact models. No significant changes were observed in facet joint forces after surgery. The current study used a parametric personalized FE modeling technique as a practical, clinically-applicable approach to predict cervical spine biomechanics post-surgical laminectomy. Altered biomechanical responses, both in terms of kinematics and kinetics, were observed, although more pronounced in models with fewer levels of laminectomy. Overall, a higher degree of motion compensation was observed at the higher levels of the cervical spine, regardless of the laminectomy level, which suggests increased spinal instability, potential risk of post-laminectomy kyphosis, and axial neck pain.

The Effect of Compression Applied Through Constrained Lateral Eccentricity on the Failure Mechanics and Flexibility of the Human Cervical Spine.

In contrast to sagittal plane spine biomechanics, little is known about the response of the cervical spine to axial compression with lateral eccentricity of the applied force. This study evaluated the effect of lateral eccentricity on the kinetics, kinematics, canal occlusion, injuries, and flexibility of the cervical spine in translationally constrained axial impacts. Eighteen functional spinal units were subjected to flexibility tests before and after an impact. Impact axial compression was applied at one of three lateral eccentricity levels based on percentage of vertebral body width (low = 5%, medium = 50%, high = 150%). Injuries were graded by dissection. Correlations between intrinsic specimen properties and injury scores were examined for each eccentricity group. Low lateral force eccentricity produced predominantly bone injuries, clinically recognized as compression injuries, while medium and high eccentricity produced mostly contralateral ligament and/or disc injuries, an asymmetric pattern typical of lateral loading. Mean compression force at injury decreased with increasing lateral eccentricity (low = 3098 N, medium = 2337 N, and high = 683 N). Mean ipsilateral bending moments at injury were higher at medium (28.3 N·m) and high (22.9 N·m) eccentricity compared to low eccentricity specimens (0.1 N·m), p < 0.05. Ipsilateral bony injury was related to vertebral body area (VBA) (r = -0.974, p = 0.001) and disc degeneration (r = 0.851, p = 0.032) at medium eccentricity. Facet degeneration was correlated with central bony injury at high eccentricity (r = 0.834, p = 0.036). These results deepen cervical spine biomechanics knowledge in circumstances with coronal plane loads.

Sex-Specific Intubation Biomechanics: Intubation Forces Are Greater in Male Than in Female Patients, Independent of Body Weight.

BackgroundStudies of head, neck, and cervical spine morphology and tissue material properties indicate that cervical spine biomechanics differ between adult males and females. These differences result in sex-specific cervical spine kinematics and injury patterns in response to standardized loading conditions. Because direct laryngoscopy and endotracheal intubation require the application of a load to the cervical spine, intubation biomechanics should be sex-specific. The aim of this study was to determine if intubation forces during direct laryngoscopy differ between male and female patients and, if so, is the difference independent of body weight.MethodsWe pooled original data from three previously published adult clinical intubation studies that used methodologically reliable intubation force measurements (measured total laryngoscope force applied to the tongue, and force values were insensitive to or accounted for other laryngoscope blade forces). All patients had undergone direct laryngoscopy and orotracheal intubation with a Macintosh 3 blade under general anesthesia. Patient data included sex, age, height, weight, and maximum intubation force. Least squares multivariable linear regression was performed between the dependent variable (maximum intubation force) and two independent variables (patient sex and patient weight). A third term was added for the interaction between patient sex and weight.ResultsAmong all patients (males n=42, females n=59), the median intubation force was 42.2 N (25th to 75th percentiles: 31.5 to 57.4 N). While controlling for patient body weight, intubation force differed between the sexes; P=0.011, with greater intubation force in male patients. While controlling for patient sex, there was a positive association between patient body weight and intubation force; P=0.009. In addition, there was a significant interaction between patient sex and weight; P=0.002, with intubation force in male patients having greater dependence on body weight. The difference in intubation force between male and female patients who had the same body weight exceeded 5 N when body weight exceeded 75 kg, and intubation force differences between male and female patients increased as patient body weight increased. Additional analyses using robust regression and using body mass index instead of weight provided comparable results.ConclusionIn adult patients, the biomechanics of direct laryngoscopy and intubation are sex-specific. Our findings support the need to control for patient sex and weight in future clinical and laboratory studies of the human cervical spine and head and neck biomechanics.

Reconstruction of the Three-dimensional Model of Cervical Vertebrae Segments Based on CT Image and 3D Printing

Reconstruct the three-dimensional model of cervical vertebrae segments based on CT image and print it with 3D techniques to provide the clinical diagnosis with clear and specific models of pathological changes and conduct simulated surgery to improve operation's effect. We imported the sequential geological data of human cervical vertebrae which is based on CT image into MIMICS software to achieve the segmentation picture of C4~C7 segments of cervical vertebrae. Then, after constructing the tentative 3D model, we put the data into GEOMAGIC Studio to get the digital model for 3D printing. By using the two reverse engineer software MIMICS and GEOMGIC Studio, we got the clear, accurate and specific 3D model of the C4~C7 segments of cervical vertebrae with complex and irregular anatomic structure. Thus, this will provide a powerful reference for the research on the case of lesion. The complete and clear 3D models of the cervical vertebrae we achieved could provide a new tool for research on the case of lesion and cervical spine bio-mechanics.

Operatywna analiza rozluźniania mięśni okolic sklepienia czaszki na biomechanikę szyjnego odcinka kręgosłupa

Operatywna analiza rozluźniania mięśni okolic sklepienia czaszki na biomechanikę szyjnego odcinka kręgosłupa