Cervical Spine Flexion Research Articles

The Diagnostic Utility of Cervical Spine Proprioception for Adolescent Concussion.

Cervical spine proprioception may be impaired after concussion. Our objective was to determine the diagnostic utility of cervical spine proprioception for adolescent concussion. Cross-sectional. Research laboratory. Adolescents ≤18 days of concussion and uninjured controls. N/A. Head repositioning accuracy (HRA) testing, a measure of cervical spine proprioception. The HRA test involved patients relocating their head back to a neutral starting position with eyes closed after maximal cervical spine flexion, extension, and right and left rotations. The overall HRA error score was the mean error (distance from the starting point to self-reported return to neutral) across 12 trials: 3 trials in each direction. We used t-tests to compare group means and logistic regression (outcome = group, predictor = HRA, covariates) to calculate odds ratios. We used a receiver operator characteristic curve to evaluate area under the curve (AUC) and calculate the optimal HRA cutpoint to distinguish concussion from controls. We enrolled and tested 46 participants with concussion (age = 15.8 ± 1.3 years, 59% female, mean = 11.3 ± 3.3 days postconcussion) and 83 uninjured controls (age = 16.1 ± 1.4 years, 88% female). The concussion group had significantly worse HRA than controls (4.3 ± 1.6 vs 2.9 ± 0.7 degrees, P < 0.001, Cohen d = 1.19). The univariable HRA model AUC was 0.81 (95% CI = 0.73, 0.90). After adjusting for age, sex, and concussion history, the multivariable model AUC improved to 0.85 (95% CI = 0.77, 0.92). The model correctly classified 80% of participants as concussion/control at a 3.5-degree cutpoint. Adolescents with concussion demonstrated worse cervical spine proprioception than uninjured controls. Head repositioning accuracy may offer diagnostic utility for subacute concussion.

Cervical spine positioning patterns amongst hand surgeons: A critical analysis of surgical posture

AimThis study aims to assess the cervical spine positioning of consultant and trainee hand surgeons during standardised hand surgeries, focusing on the prevalence of sustained end-range postures, particularly cervical spine flexion. BackgroundSurgeons often perform procedures that require maintenance of sustained postures for prolonged periods of time. Hand surgeons may be at increased risk of sustained end of range postures, particularly cervical spine flexion. This can lead to strain on the musculoskeletal structures of the neck. Recent evidence suggests a higher incidence of neck dysfunction in hand surgeons, leading to an associated morbidity. MethodsWe examined hand surgeons of all experience levels during 40 common hand surgery procedures. We used real-time dynamic goniometric measurements of neck flexion using the “UPRIGHT GO 2” device and accompanying smartphone app. Neck flexion exceeding 40° was used as the threshold for defining an acceptable neck position. ResultsAnalysis included 20 total subjects at various levels of medical training (SHO n ​= ​6, Registrar n ​= ​9, Consultant n ​= ​5) performing surgeries under different conditions. Maladaptive neck positions were prevalent, with junior surgeons exhibiting such postures for 71 ​% of procedure time compared to 60 ​% for consultants. This underscores the potential contribution of sustained end-range postures to cervical spine dysfunction in hand surgeons, highlighting an early intervention opportunity. Notably, participants reported varied experiences with neck pain and expressed unanimous interest in integrating biofeedback posture devices into surgical training, with a single consultant expressing reservations.

Efficacy of Dynamic Magnetic Resonance Imaging in the Diagnosis of Degenerative Cervical Myelopathy: Systematic Review Protocol.

Cervical degenerative myelopathy (CDM) is a cervical spine condition resulting in clinical manifestations of spinal cord compression related to the chronic, non-traumatic, and progressive narrowing of the cervical spinal canal. Conventional magnetic resonance imaging (MRI) is the gold standard test to diagnose and assess the severity of CDM. However, the patient is in a neutral and static position during the MRI scan, which may devalue the dynamic factors of CDM, underestimating the risk of spinal cord injury related to cervical spine flexion and extension movements. Dynamic MRI is a promising technique to change this scenario. Therefore, the present review aims to answer the following question: "Is dynamic MRI of the cervical spine more accurate in diagnosing CDM than conventional MRI?". We will search for studies in the MEDLINE (via PubMed), Embase, Scopus, Web of Science, LILACS, and SciELO databases. The search strategy will contain a combination of terms related to cervical myelopathy and magnetic resonance imaging . Two independent reviewers will select studies, extract data, and assess the risk of bias. The synthesis of results will be descriptive, considering the main findings of the studies about the outcomes of interest.

Autumn abstracts

Aims To analyse the C-spine position of consultant and trainee hand surgeons during standardised hand surgeries. Surgeons often perform procedures that require maintenance of sustained postures for prolonged periods of time. Hand surgeons may be at increased risk of sustained end of range postures, particularly cervical spine flexion. This can lead to strain on the musculoskeletal structures of the neck. Recent evidence suggests a higher incidence of neck dysfunction in hand surgeons, leading to an associated morbidity. We aimed to quantify the nature of cervical spine positioning among hand surgeons. Methods We examined 20 hand surgeons of all experience levels during a standardised carpal tunnel decompression procedure. We used real-time dynamic goniometric measurements of neck flexion using the ‘UPRIGHT GO 2’ device and accompanying smartphone app. Neck flexion &gt;40% was used as a cut-off point for an acceptable neck position. Results Hand surgeons of all levels adopt maladaptive positions during hand surgery. Junior surgeons tended to adopt similar maladaptive positions (71% of the procedure time) versus 60% for consultant surgeons. This may contribute to C-spine dysfunction in hand surgeons and presents an opportunity to intervene at an early career stage to attenuate what could become irreversible dysfunction.

Effect of a new type of head and neck fixation and traction device in the surgical treatment of patients with irreducible atlantoaxial dislocation

BackgroundIn order to improve the clinical medical technology, enhance the clinical effect and improve the disease detection rate, the clinical incidence rate of atlantoaxial dislocation and vertebral body malformation that are difficult to summarize is increasing year by year.MethodsA total of 80 patients with atlantoaxial dislocation deformity treated in our hospital from January 2017 to May 2021 are selected for this study. According to the number table method, 80 patients are randomly divided into the auxiliary group and the traditional group, with 40 cases in each group. The traditional group is treated with posterior atlantoaxial pedicle screw system internal fixation and intervertebral fusion, and the auxiliary implementation and application of a new head and neck fixation and traction device through nasal cannula and oral release decompression fixation for posterior fusion. The patients in the two groups are compared changes and differences in efficacy, spinal cord function index, pain score, surgery, and quality of life.ResultsCompared with the traditional group, the total clinical effective rate, cervical spine extension and flexion range of motion, physical function, physical function, psychological function, and social function in the auxiliary group are significantly improved. The operation time, intraoperative blood loss, and VAS score are significantly reduced (P < 0.05).ConclusionThe new head and neck fixation traction device can improve the surgical efficacy and quality of life of patients with irreversible atlantoaxial dislocation, enhance spinal cord function, reduce pain symptoms and surgical risks, and is worthy of clinical application.

Biomechanical effects of a halo orthotic on a pediatric anthropomorphic test device in a simulated frontal motor vehicle collision

Objective: Cervical spine injuries in children under 10 frequently involve the craniocervical junction. In patients too small for conventional spinal instrumentation, treatment may involve placement of a halo orthotic, and these patients will frequently be discharged home in a halo orthotic. To date, little research has been done on the biomechanics of motor vehicle collisions involving young children in halo orthotics. To better understand possible safety concerns, we applied a halo orthotic to an appropriately sized anthropomorphic test device (ATD, or crash test dummy) on an acceleration sled to simulate a frontal motor vehicle collision. Methods: For the tests, a Hybrid III 3-year-old ATD was instrumented with head and chest accelerometers, head angular rate sensors, a six-axis upper neck load cell, and a chest linear potentiometer. Four tests were conducted on an acceleration sled, and kinematics were recorded with high speed video. Testing variables included 1) with or without a halo orthotic and 2) with a standard booster seat or a commercially available harness vest. Results: The halo orthotic reduced flexion and extension but was associated with increased rotation, especially in the condition of a halo orthotic with a standard booster seat. Increased cervical distraction was noted with the halo orthotic, and this was especially increased in the condition of a halo orthotic with the harness vest. Conclusions: The biomechanics of a child involved in a motor vehicular collision may be dramatically altered with a halo orthotic, as modeled by an acceleration sled test. While cervical spine flexion and extension are reduced with the halo orthotic, rotation appears to increase. Immobilization from a halo orthotic also appears to increase cervical distraction, especially when used in conjunction with a harness vest. Further testing is needed to determine the safest restraints for this small, but at-risk, population.

Two-stage orthodontic treatment outcomes of children with dentoalveolar class II malocclusion

Background. During the rehabilitation of children with distal occlusion, it is not always possible to achieve the desired outcomes. In this context, the factors influencing the outcomes of treatment for class II malocclusions in children at different stages of occlusion development.&#x0D; Aim. To study two-stage orthodontic treatment outcomes in children with dentoalveolar class II malocclusion by the clinical case.&#x0D; Material and methods. We analyzed the physical examination results of the patient within the treatment from 6 to 17 years. Facial proportion symmetry, aesthetic, type of face, plaster dental models were determined by using the photographs. Orthopantomography was used to analyze the condition of temporary and permanent teeth, jaw bone tissue and to assess functional disorders. Orthodontic treatment in a mixed dentition period was carried out using removable devices, including those improved by the authors. In the permanent dentition, orthodontic brackets with power elements were used.&#x0D; Results. Untimely contacting the doctor, an insufficient level of motivation to implement recommendations for improving posture and dental care contributed to an increase in treatment duration. Keeping excessive cervical spine flexion and head tilted back, the bad habit of placing (pressure) the hand on the chin, and the rejection of a myo-gymnastic exercise (physical therapy) interfered with the synchronous (normal) development of the jaws. Premature loss of a temporary molar on one side led to dentoalveolar asymmetry and disruption of occlusal contacts. Additional orthodontic appliances were used to correct these deformities. Over-retained deciduous teeth led to the delayed eruption of permanent teeth and, presumably, to the curvature of their roots. Violation of the tooths root shape and asymmetry in permanent teeth crown size prevented the full correction of their position using highly effective modern non-removable orthodontic equipment. The anomalous position of the rudiment of the third molar, the refusal for timely tooth extraction further led to the increasing complexity of the surgical technique.&#x0D; Conclusion. The timing and effectiveness of orthodontic treatment of a patient with dentoalveolar class II malocclusion were influenced by a poor body posture, extraction of a primary molar, the delayed eruption and crown size asymmetry of permanent teeth, the presence of bad habits and minimal cooperation of the patient with the orthodontist.

Analysis of remaining motion using one innovative upper airway opening cervical collar and two traditional cervical collars

The aim of this study was to compare the remaining motion of an immobilized cervical spine using an innovative cervical collar as well as two traditional cervical collars. The study was performed on eight fresh human cadavers. The cervical spine was immobilized with one innovative (Lubo Airway Collar) and two traditional cervical collars (Stifneck and Perfit ACE). The flexion and lateral bending of the cervical spine were measured using a wireless motion tracker (Xsens). With the Weinman Lubo Airway Collar attached, the mean remaining flexion was 20.0 ± 9.0°. The mean remaining flexion was lowest with the Laerdal Stifneck (13.1 ± 6.6°) or Ambu Perfit ACE (10.8 ± 5.8°) applied. Compared to that of the innovative Weinmann Lubo Airway Collar, the remaining cervical spine flexion was significantly decreased with the Ambu Perfit ACE. There was no significant difference in lateral bending between the three examined collars. The most effective immobilization of the cervical spine was achieved when traditional cervical collars were implemented. However, all tested cervical collars showed remaining motion of the cervical spine. Thus, alternative immobilization techniques should be considered.

A BIOMECHANICAL STUDY OF THE EFFECTS OF FLEXION ANGLE ON THE INDUCTION MECHANISM OF CERVICAL SPONDYLOSIS

Lesions in facet joints such as bone hyperplasia and degenerative changes in the intervertebral discs, can compress nerve roots and the spinal cord, leading to cervical spondylosis (CS). Lesions in these parts of the spine are commonly related to abnormal loads caused by bad posture of the cervical spine. This study aimed to understand the potential mechanical effects of load amplitude on cervical spine motion to provide a theoretical basis for the biomechanical causes of CS, and to provide a reference for preventing of the condition. In this study, a finite element model of the normal human cervical spine (C1-C7) was established and validated using an infrared motion capture system to analyze the effects of flexion angle on the stresses experienced by intervertebral discs, the anterior edge of the vertebral body, the pedicle, uncinate and facet joints. Our analysis indicated that the intervertebral disc load increased by at least 70% during the 20∘ to 45∘ flexion of the neck with 121% load increase in the vertebrae. In the intervertebral discs, the stress was largest at C4-C5, and the stress was moderate at C5-C6. These results are consistent with clinical CS prone site research. According to Wolff’s law, when bones are placed under large stresses, hyperplasia can result to allow adaptation to large loads. Increased cervical spine flexion angles caused the proliferation of bone in the above-mentioned parts of the spine and can accelerate accelerating the appearance of CS.

Analysis of factors related to granting sickness benefits to industry workers on leave due to Work-related Musculoskeletal Disorders (WMSD)

Background: Sickness absence represents a serious problem for industry and Social Security, since many of these workers become beneficiaries by the National Social Security Institute. The relationship between the factors that lead to dismissal and granting benefits to workers in the industry has yet to be studied. Objective: To determine the relationship between social and occupational factors to granting sickness benefits to industrial workers affected by Work-related Musculoskeletal Disorders. Methods: This is a retrospective cross-sectional with quantitative approach study involving industrial workers. The data contained in the evaluation form of workers who were admitted between 2016 and 2020 in a Reference Centers in Occupational Health were used. The data were descriptively evaluated and a logistic regression model was used to estimate the factors which are related to the type of assistance granted to the workers. Results: 108 medical records of industry workers were evaluated and 56.5% received the accident-related sickness assistance benefit (B-91). Most are workers from industry with light demand (95.4%), who perform repetitive work (93.5%), intense work pace (83.3%), with the shoulder being the region most frequently affected (85.2%). The factors that were significantly related to grating accidental-related sickness benefit: time in the current occupation (OR = 1.01), work involving cervical spine flexion (OR = 4.68), participation in the rehabilitation program (OR = 31.27) and referral to specialist consultations (OR = 3.10). Conclusion: The creation of institutional programs in the industry and the implementation of public health and social security policies are necessary to manage these factors.

Application of a Halo Fixator for the Treatment of Pediatric Spinal Deformity.

In spine surgery, the halo fixator was initially utilized to stabilize cervical fusions in patients with poliomyelitis. More recently, the indications for halo fixation have evolved to include stabilization and definitive treatment for upper cervical spine injuries (Jefferson fractures, atlanto-occipital dissociations, odontoid fractures, etc.), treatment of atlantoaxial rotatory subluxation, stabilization of long cervical fusions, and preoperative traction. In the realm of pediatric spinal deformity, halo fixation has proved to be a valuable resource for severe or neglected spinal deformities. In this video article, we demonstrate the application of a halo fixator in a pediatric patient with severe scoliosis. The procedure includes appropriate pin placement in the safe zones of the skull performed under either general anesthesia or local anesthesia. Pins are secured to a halo frame that is sized to be 2 cm larger than the circumference of the skull and are tightened according to age-specific torque guidelines. Alternative treatments vary from cervical spine immobilization to definitive surgical treatment in the spine, or even spinal osteotomies, depending on the underlying spinal pathology. The halo fixator works by limiting motion of the cervical spine in flexion, extension, and axial rotation. The halo is also able to control and correct translational injuries of the cervical spine. In the setting of spinal deformity, the halo fixator can also be utilized to overcome the effects of gravity and lengthen the spine. For spinal deformities, the halo fixator can be expected to lengthen the spine and increase deformity flexibility prior to definitive surgical treatment in the spine or growth-friendly spinal instrumentation. Correct identification of safe zones for pin placement is vital to correct pin placement.For pediatric patients, it is important to obtain fixation with a minimum of 6 to 8 pins.Pins should be tightened with use of a torque-limiting wrench, up to no more than 1 in/lb (55.9 mm/kg) per year of age, up to a maximum of 8 in/lb (447.9 mm/kg).Applied traction should be a maximum of 50% of the body weight of the patient.Neurovascular examination is vital following application of weight.

Measuring Cervical Range of Motion with Gyroscope/Accelerometer Eyeglasses (JINS MEME) in Persons with and without Neck Pain

Context: Neck pain is common in the general population. Active cervical spine range of motion (ACROM) is often measured in the diagnosis, evaluation, and treatment of neck pain. However, commonly used measurement tools have been deemed inaccurate or impractical. The Cervical Range of Motion (CROM) Instrument, which uses inclinometers and a magnetic reference, has demonstrated high reproducibility and validity in the measurement of ACROM, however, its practicable use is suboptimal due to its large dimensions. The JINS MEME eyeglass is a lightweight and compact wearable device that contains gyroscope and accelerometer electrodes capable of detecting body motion offering an alternative means of measuring ACROM. Aims: The primary aim of this study is to validate ACROM measurements using the JINS MEME eyeglasses in comparison to the CROM Instrument. The secondary aim is to investigate the variable range of motion patterns between individuals with neck pain (NP group) versus asymptomatic individuals (AS group). Settings and Design: This was a cross-sectional, clinical measurement, and reliability study. Subjects and Methods: Seven neck pain and 14 asymptomatic individuals underwent ACROM measurements with the JINS MEME and CROM Instrument concurrently. Statistical Analysis Used: Intraclass correlation coefficient was used to determine inter- and intra-rater reliability of the JINS MEME and CROM Instrument. Mann–Whitney's U-test was used to assess differences between the two groups (NP group vs. AS group) in ACROM. Results: Using the JINS MEME eyeglasses, we observed excellent intra- and inter-rater reliability for nearly all ACROM directions (cervical spine flexion, extension, and lateral bending) except for rotation which was considered poor. ACROM was decreased in all directions for neck pain patients when measured by both devices. Conclusions: The JINS MEME eyeglasses showed excellent intra- and inter-rater reliability for all ACROM movements except for cervical rotation. Comparing the AS group and NP group, the ACROM of the NP group was significantly decreased compared to that of the AS group in all cervical spine directions, similar to findings in previous studies. With the exception of the measurement of cervical rotation, the JINS MEME eyeglasses demonstrated similar accuracy to the CROM Instrument in the assessment of ACROM in both the NP and AS groups.

The diagnostic quandary of magnetic resonance imaging-negative Hirayama disease: a case report

BackgroundMagnetic resonance imaging (MRI) features are typical findings in Hirayama disease (HD) and are useful diagnostic entities but may not be present in all patients.Case presentationWe present the case of a 22-year-old Nepalese man who presented with insidious onset of weakness of his right upper limb of more than 5 years duration. His weakness was progressive for the first 3 years, and then remained static. On examination, weakness of the interossei, thenar, hypothenar, flexor, and extensor muscles were present in his right upper limb, power was normal in his left upper and bilateral lower limbs. Minipolymyoclonus was present in both upper limbs, less prominent on the left side. Electrophysiological findings showed motor axonal neuropathy in his right upper limb, neurogenic discharges and fibrillations, and fasciculations in both upper limbs. Contrast magnetic resonance imaging (MRI) of his cervical spine in flexion was normal. Our patient was diagnosed with HD based on clinical and electrophysiological findings. Our patient was advised to use a cervical collar and regular physiotherapy and was found to have subjective benefit.ConclusionA normal cervical MRI does not rule out HD and the diagnosis can also be made based on clinical and electrophysiological studies. Progressive distal upper limb weakness or tremor in young patients should be evaluated for HD, because early diagnosis and intervention might halt the progression.

1223 Central sleep apnea and Chiari 1 malformation in a pediatric patient with Klippel-Feil sequence

Abstract Introduction Klippel- Feil Sequence (KFS) is a rare congenital condition that classically presents with a triad of congenital cervical spine fusion, reduced cervical spine flexion and low posterior hairline. KFS has been associated with several comorbidities including congenital heart defects, hearing loss, renal dysfunction, Chiari malformation and sleep disordered breathing (SDB). The co-occurrence of SDB and chiari malformation type 1 (CM1) has been reported in multiple individuals. However, the pathological basis of the connection between CM1 and SDB in the setting of KFS is not clearly understood. Report of Case Here we present a pediatric case report of a patient with KFS, SDB, drooling and dysphagia. The drooling and dysphagia prompted an MRI that revealed CM1. Baseline polysomnogram (PSG) showed mild central sleep apnea with apnea-hypopnea index (AHI) 6.06 comprised of central apnea index 4.81 and obstructive apnea index 1.28. Posterior fossa decompression of this patient, following neurology recommendations, resolved majority of the symptoms, namely the drooling, nocturnal cough, dysphagia and sleep disturbances. However unexpectedly repeat polysomnogram eight weeks after posterior fossa decompression revealed worsening central sleep apnea despite the patient being clinically asymptomatic. Conclusion Taken together this case highlights the point that while it is critical to recognize the association of SDB in the setting of KFS, decompression alone may not be sufficient to completely alleviate SDB and/or certain neurological symptoms such as nocturnal coughing. Our observations are consistent with the hypothesis that SDB in a setting of KFS is multifactorial and pathophysiology is not clearly understood.

Cervical spine joint loading with neck flexion

Cervical spine flexion is a common posture for those using computers, tablets, and smartphones; the latter being dubbed ‘text-neck’ in recent years. Coincidentally, flexion has been flagged as a significant mechanical risk factor for the development of chronic neck pain. Unfortunately, few modelling endeavours have attempted to quantify the intervertebral joint loads throughout the cervical spine in flexion, while still accounting for muscular activation. Eight healthy male subjects undertook five trials beginning in a neutral posture, flexed to 45 degrees, and returned to a neutral posture. 3 D head-trunk angles and surface electromyography from 10 neck muscles (5 bilaterally) were used as inputs into an inverse dynamic cervical spine model based on a 50th percentile male to compute the compression and anteroposterior (AP) shear forces for this flexion task. In general, compression increases cranially to caudally throughout the cervical spine, but levels off at the C5-C6 level. Conversely, in a neutral posture, there is a constant 18 N of anterior shear at each joint level. Compression increased twofold throughout the cervical spine with flexion, whereas anterior shear increased fourfold in the upper cervical spine and dramatically decreased caudally. The dramatic change in joint kinetics provides some mechanical evidence for the role of posture and interplay with muscle activity in the development of chronic neck pain. Results from this study can reinforce the need for appropriate workstation and monitor configurations and support the increased loading hypothesised to occur in ‘text neck’ postures. Practitioner summary: The purpose of this investigation was to quantify the compression and shear forces in the neck in 45 degrees of flexion compared to neutral. Flexion increased compression throughout the cervical spine 1.6-fold compared to a neutral posture. In the upper cervical spine, AP-shear increased four-fold compared to neutral. Abbreviation: AP: anteroposterior

PROXIMAL BRACHIAL MONOMELIC AMYOTROPHY OR HIRAYAMA DISEASE: NO LONGER AN ALIAS? (case report)

Background. Brachial Monomelic Amyotrophy (BMMA) has been called as Hirayama disease (HD) when it is characterized by unilateral distal upper limb weakness and atrophy that shows progression for a limited period and is associated with typical features on MRI of cervical spine in flexion.&#x0D; Objective was to explore the differences when BMMA affects the proximal upper limb muscles with the help of case report.&#x0D; Methods. A case report of BMMA in an adult Indian male is represented.&#x0D; Results. A 30-year-old man presented to us with a history of weakness in the proximal aspect of his left upper limb that began four years ago. The weakness was progressive up until 6 months prior to his presentation since when the weakness had neither worsened nor improved. Cervical spine contrast enhanced MRI revealed mild loss of cervical lordosis, but no features of HD like localized cord atrophy, loss of attachment of dura from subjacent lamina on neutral position axial T2WI MRI, nor any presence of posterior epidural crescentic enhancing mass on flexion contrast sagittal T1WI MRI. The patient was managed with supportive therapy and has been under regular follow up ever since. His clinical status has been stable.&#x0D; Conclusions. We support the suggestion to consider proximal Brachial Monomelic Amyotrophy to be a separate entity and to be distinguished from Hirayama disease that should be reserved for patients with distal upper limb involvement with cervical MRI findings on flexion studies.

Experimental analysis of the lower cervical spine in flexion with a focus on facet tracking

Cervical traumas are among the most common events leading to serious spinal cord injuries. While models are often used to better understand injury mechanisms, experimental data for their validation remain sparse, particularly regarding articular facets. The aim of this study was to assess the behavior of cervical FSUs under quasi-static flexion with a specific focus on facet tracking. 9 cadaveric cervical FSUs were imaged and loaded under a 10 Nm flexion moment, exerted incrementally, while biplanar X-rays were acquired at each load increment. The relative vertebral and facet rotations and displacements were assessed using radio-opaque markers implanted in each vertebra and CT-based reconstructions registered on the radiographs. The only failures obtained were due to specimen preparation, indicating a failure moment of cervical FSUs greater than 10 Nm in quasistatic flexion. Facet motions displayed a consistent anterior sliding and a variable pattern regarding their normal displacement. The present study offers insight on the behavior of cervical FSUs under quasi-static flexion beyond physiological thresholds with accurate facet tracking. The data provided should prove useful to further understand injury mechanisms and validate models.

Establishment and Finite Element Analysis of a Three-dimensional Dynamic Model of Upper Cervical Spine Instability.

ObjectivesTo establish a dynamic three‐dimensional (3D) model of upper cervical spine instability and to analyze its biomechanical characteristics.MethodsA 3D geometrical model was established after CT scanning of the upper cervical spine specimen. The ligament of the specimen was fatigued to establish the upper cervical spine‐instability model. A 100‐N preloaded stress was applied to the upper surface of the occipital bone, and then a 1.5‐Nm moment was applied in the occipital‐sagittal direction to simulate upper cervical spine flexion and extension. Subsequently, the 3D dynamic model was established based on trajectory data that were measured using a motion‐capture system. The stress on the main ligament and the relative motion angle of the joint were analyzed.ResultsThe shape of the model grid was regular and the total number of its units was 627 000. After finite‐element analysis was conducted, results of the ligament stress and relative movement angle were obtained. After the upper cervical spine instability, the pressure of the alar ligament during the upper cervical spine extension was increased from 2.85 to 8.12 MPa. The pressure of the flavum ligament was increased during the upper‐cervical spine flexion, from 0.90 to 1.21 MPa. The pressure of the odontoid ligament was reduced during the upper cervical spine flexion and extension, from 10.46 to 6.67 MPa and 25.66 to 16.35 MPa, respectively. The pressure of the anterior longitudinal ligament and cruciate ligament was increased to a certain degree during upper cervical spine flexion and extension. The pressure of the anterior longitudinal ligament was increased during flexion and extension, from 7.70 to 10.10 MPa and 10.45 to 13.75 MPa, respectively. The pressure of the cruciate ligament was increased during flexion and extension, from 2.29 to 4.34 MPa and 2.32 to 4.40 MPa, respectively. In addition, after upper cervical spine instability, the articular‐surface relative‐movement angle of the atlanto‐occipital joint and atlanto‐axial joint had also changed. During upper cervical spine flexion, the angle of the atlanto‐occipital joint was increased from 3.49° to 5.51°, and the angle of the atlanto‐axial joint was increased from 8.84° to 13.70°. During upper cervical spine extension, the angle of the atlanto‐occipital joint was increased from 11.16° to 12.96°, and the angle of the atlanto‐axial joint was increased from 14.20° to 17.20°. Therefore, the movement angle of the atlanto‐axial joint was most obvious after induction of instability.ConclusionThe 3D dynamic finite‐element model of the upper cervical spine can be used to analyze and summarize the relationship between the change of ligament stress and the degree of instability in cervical instability. Frequent or prolonged flexion activities are more likely to lead to instability of the upper cervical spine.

Clinical Relevance of Cervical Kinematic Quality Parameters in Planar Movement.

Comprehending cervical spinal motion underlies the understanding of the mechanisms of cervical disorders. We aimed to better define the clinical relevance of cervical spine kinematics, focusing on quality parameters describing cervical spine planar motion. The most common study focuses were kinematic quality parameters after cervical arthroplasty and in normal subjects, patients with cervical degeneration, and patients with cervical deformities. Kinematic quality parameters are important for cervical degeneration prevention, being detected sooner than differences on imaging examinations and being significantly related to the degree of cervical degeneration. Kinematic quality parameters are effective for evaluating the changes of cervical motion pattern after cervical fusion and non‐fusion, assessing operative and adjacent segments in the early stages, and predicting adjacent segment degeneration. However, owing to current research limitations, and controversy about the changes of kinematic quality parameters after different surgical procedures, current assessments are limited to cervical spine flexion and extension. Different osteotomy methods of cervical deformity have different effects on cervical motion patterns and quality parameters. Choosing the most effective surgical method remains a challenge and kinematic quality parameters in cervical deformity are important future research topics. This review highlights the instantaneous center of rotation, the center of rotation, and the instantaneous axis of rotation as being important kinematic quality parameters of cervical spinal motion. These can be used to detect abnormal cervical mobility, to diagnose cervical degeneration, to design disc protheses, and to evaluate surgical effects earlier than other methods. Owing to limitations of research methods there is variation in the way parameters are defined by various researchers. No uniform standard exists for defining degenerative motion quality parameters in normal asymptomatic, degenerative, and postoperative patients. Therefore, further study is required. New study techniques and defining kinematic quality parameters in normal subjects will clarify the definitions of these parameters, enhancing their future clinical usefulness.

Clinical analysis of pedicle screw fixation in the treatment of type II odontoid fracture with bone grafting and non-bone grafting

Objective To explore the clinical efficacy of bone grafting in the treatment of type Ⅱ odontoid fracture with pedicle screw fixation. Methods Of 14 cases with type Ⅱ odontoid fractures, 8 patients in group A received pedicle screw, lamina autologous bone grafts, 6 cases of group B received simple posterior pedicle screw fixation.The operative time, the amount of surgical bleeding and the postoperative cervical spine flexion and rotation were observed at 3 months postoperatively, and the patients were followed up for 5-45 months. Results All patients were followed up for 5-45 months, with an average of 26.5 months.The operation time was (1.83±0.5)h in the bone graft group, and (1.58±0.9)h in the non-bone graft group, the difference was statistically significant (t=2.842, P>0.05). The blood loss of the bone graft group was (150±16)mL, which of the non-bone graft group was (120±14)mL, the difference between the two groups was statistically significant (t=3.57, P>0.05). After 3 months, the flexion of the cervical spine of the bone graft group was (31.2±4.6)°, which in the non-grafted group was (32.3±5.7)°, the difference was statistically significant (t=0.675, P<0.05). The rotation of the bone graft group was (40.6±4.5)°, which in the non-graft group was (41.3±3.5)°, the difference was statistically significant (t=0.278, P<0.05). Both two groups had no vertebral artery and spinal cord injury, wound healing.During the follow-up period, the two groups of patients had a good reduction of cervical spine, no internal fixation lossening, fracture, fracture healing well, group A bone graft fusion. Conclusion For this type of fracture, simple atlantoaxial pedicle screw fixation compared with autologous iliac bone graft fusion treatment, can save the operation time, reduce the amount of bleeding. Key words: Fracture, bone; Pedicle screw; Cervical vertebrae