Cervical Motion Segment Research Articles

Mechanical consequences to the annulus fibrosus following rapid internal pressurization and endplate fracture under restrained-expansion conditions

Intervertebral disc herniation is not a common injury in the adolescent population, but the correlation between trauma and herniation warrants concern. Previous research demonstrated the capacity for rapid internal pressurization to reduce the mechanical integrity of the intervertebral disc's annulus fibrosus, even in the absence of fracture. The purpose of this study was to modify previous internal pressurization procedures towards a more transferable injury model, then investigate the capacity for these procedures to damage the mechanical integrity of the annulus fibrosus. Porcine cervical motion segments with intact facet joints were confined between a vice and force plate under 300 N of static compression, then a single, manual, rapid internal pressurization was delivered. Posterolateral annulus samples were extracted and situated in a 180° peel test configuration, exposing the interlamellar matrix of samples to separations of 0.5 mm/s, until complete separation of the sample occurred. Multilayer tensile testing was performed on superficial and mid-span samples of annulus by applying uniaxial tension of 1 %/s to 50 % strain. Compared to unpressurized controls, rapid pressurization causing fracture resulted in reduced lamellar adhesion and increased toe-region stress and strain properties in the annulus. Morphological assessment reported similar fracture patterns between endplate fractures achieved in the present experiment and endplate fractures documented in human patients. Mechanical plus morphological results suggest that rapid internal pressurization resulting in endplate fracture may represent a potent mechanism for subsequent damage to the intervertebral disc.

The Effects of Cervical Orthoses on Head and Intervertebral Range of Motion.

Prospective Cohort. Quantify and compare the effectiveness of cervical orthoses in restricting intervertebral kinematics during multiplanar motions. Previous studies evaluating the efficacy of cervical orthoses measured global head motion and did not evaluate individual cervical motion segment mobility. Prior studies focused only on the flexion/extension motion. Twenty adults without neck pain participated. Vertebral motion from the occiput through T1 was imaged using dynamic biplane radiography. Intervertebral motion was measured using an automated registration process with validated accuracy better than 1 degree. Participants performed independent trials of maximal flexion/extension, axial rotation, and lateral bending in a randomized order of unbraced, soft collar (foam), hard collar (Aspen), and cervical thoracic orthosis (CTO) (Aspen) conditions. Repeated-measures ANOVA was used to identify differences in the range of motion (ROM) among brace conditions for each motion. Compared with no collar, the soft collar reduced flexion/extension ROM from occiput/C1 through C4/C5, and reduced axial rotation ROM at C1/C2 and from C3/C4 through C5/C6. The soft collar did not reduce motion at any motion segment during lateral bending. Compared with the soft collar, the hard collar reduced intervertebral motion at every motion segment during all motions, except for occiput/C1 during axial rotation and C1/C2 during lateral bending. The CTO reduced motion compared with the hard collar only at C6/C7 during flexion/extension and lateral bending. The soft collar was ineffective as a restraint to intervertebral motion during lateral bending, but it did reduce intervertebral motion during flexion/extension and axial rotation. The hard collar reduced intervertebral motion compared with the soft collar across all motion directions. The CTO provided a minimal reduction in intervertebral motion compared with the hard collar. The utility in using a CTO rather than a hard collar is questionable, given the cost and little or no additional motion restriction.

Changes in intervertebral sagittal alignment of the cervical spine from supine to upright.

Cervical sagittal alignment is a critical component of successful surgical outcomes. Unrecognized differences in intervertebral alignment between supine and upright positions may affect clinical outcomes; however, these differences have not been quantified. Sixty-four patients scheduled to undergo one or two-level cervical arthrodesis for symptomatic pathology from C4-C5 to C6-C7, and forty-seven controls were recruited. Upright sagittal alignment was obtained through biplane radiographic imaging and measured using a validated process with accuracy better than 1° in rotation. Supine alignment was obtained from computed tomography scans. Coordinate systems used to measure supine and upright alignment were identical. Distances between adjacent bony endplates were measured to calculate disc height in each position. For both patients and controls, the C1-C2, C2-C3, and C3-C4 motion segments were in more lordosis when upright as compared with supine (all p < 0.001). However, the C4-C5, C5-C6, and C6-C7 motion segments were in less lordosis when upright as compared with supine (all p ≤ 0.004). There was an interaction between group and position at the C1-C2 (p = 0.002) and C2-C3 (p = 0.001) motion segments, with the controls demonstrating a greater increase in lordosis at both motion segments when moving from supine to upright. The results indicate that cervical motion segment alignment changes between supine and upright positioning, those changes differ among motion segments, and cervical pathology affects the magnitude of these changes. Clinical Significance: Surgeons should be mindful of the differences in alignment between supine and upright imaging and the implications they may have on clinical outcomes.

Clinical observation on correction of abnormal cervical sagittal parameters by cervical pulling method guided by cervical motion segment extension

To observe the radiological change and curative effect of cervical spondylosis treated with cervical vertebra pulling therapy in young people. A total of 65 patients(shedding in 5 patients and final inclusion in 60 patients) with cervical spondylosis who were treated from January 2018 to September 2019 were randomly divided into treatment group and control group according to the digital table method. There were 30 patients in treatment group, including 14 males and 18 females, aged from 20 to 44 years old with an average of(29.83±6.99) years, who were treated with cervical vertebra pulling therapy(once a week, 4 times in total). The control group consisted of 30 cases, 12 males and 18 females, aged from 18 to 43 years old with an average of (31.77±5.93) years, who received sitting traction therapy(once a week, 4 times in total). The changes of C2-C7 Cobb angle, arc-chord distance and T1 slope (T1S) in two groups were observed before treatment and 1 month after treatment, for intra-group and inter-group comparison;and the changes of numerical rating scale(NRS) in two groups were observed before treatment and 1, 3 months after treatment, for intra-group and inter-group comparison. Sixty patients were followed up for (3.2±0.3) months. There were no significant differences in NRS, C2-C7 Cobb angle, arc-chord distance and T1S between two groups before treatment (P>0.05). One month after treatment, the NRS, C2-C7 Cobb angle, arc-chord distance and T1S were(1.67±0.76) scores, (16.55±6.01)°, (10.95±4.04)mm, (18.95±4.19)° in treatment group and(1.40±0.86) scores, (10.23±5.94) °, (6.11±4.17) mm, (13.34±4.25)° in control group respectively. C2-C7 Cobb angle, arc-chord distance and T1S in treatment group were better than those in control group (P<0.05); there was no significant difference in NRS between two groups (P>0.05). Compared with before treatment, there were statistically significant differences in C2-C7 Cobb angle, arc-chord distance and T1S in treatment group(P<0.05), but no statistically significant differences in control group(P>0.05). Three months after operation, NRS of treatment group was (1.60±0.62) scores and that of control group was (4.17±0.70) scores. The treatment group was better than the control group(P<0.05). The scores of treatment group after treatment were lower than those before treatment(P<0.05), and there was no significant difference in control group before and after treatment(P>0.05). Cervical vertebra pulling method and cervical vertebra sitting traction can relieve the pain symptoms of patients with cervical spondylosis, but the effect of cervical vertebra pulling method is more durable;cervical vertebra pulling method can correct abnormal cervical sagittal parameters.

P17. Biomechanical effects of changes in cervical alignment following single-level ACDF using 3D motion capture

<h3>BACKGROUND CONTEXT</h3> Alignment of the cervical spine likely has significant effects on the clinical longevity of the subaxial motion segments. The biomechanical effects of changes in alignment on the cervical spine remain to be understood. Single-level ACDF is a commonly performed procedure and cervical alignment may influence motion transfer to adjacent and noncontiguous subaxial motion segments. <h3>PURPOSE</h3> The purpose of this study is to better understand the role of alignment on unfused cervical motion segments, the present study was designed to evaluate the biomechanical effects on the subaxial cervical spine (C2 to T1) of 1) changes in T1 tilt 2) single-level ACDF and 3) combined effects of ACDF and changes in T1 tilt. <h3>STUDY DESIGN/SETTING</h3> Cadaveric study. <h3>PATIENT SAMPLE</h3> Six cadaveric cervical spines (C2-T1). <h3>OUTCOME MEASURES</h3> Biomechanical metrics. <h3>METHODS</h3> Six cadaveric cervical spines (C2-T1) were screened fluoroscopically and placed with retro-reflective markers. Computed tomography (CT) scans with sagittal/coronal reformats were performed and degeneration was graded. Specimens were tested to 30° flexion and 30° extension in the intact state and following single-level ACDF(C5-C6). Motions of each vertebral body were tracked using a 3D-motion capture system and input into an inverse kinematics model to correlate the 3D reconstruction and motion capture data. A customized testing apparatus was developed to alter the T1 slope in human cervical cadaveric spines to neutral, +15°, and -15°. Generalized estimating equation modeling was used to analyze the main effects as well as the interaction effects of fusion, while we also controlled for the clustered nature of the data. Parameter estimates of the model are reported as mean change in range of motion and standard error, with statistical significance defined as p-value = .05. SAS software was used for all statistical analyses. <h3>RESULTS</h3> In the intact specimen, increase in T1 tilt (0° to +15°) did not result in increased ROM at any motion segment (C2-3, C3-4, C4-C5, C5-6, C6-C7, C7-T1: p=NS). In the intact specimen, decrease in T1 tilt (0° to -15°) resulted in significantly increased ROM at C2-C3 (p < .0001), C3-C4 (p < .0001), C5-C6 (p < .01), C6-C7 (p <.005) and C7-T1 (p < .02), but not at C4-C5 (p=NS). The effects of ACDF on the unfused segments at various cervical alignments was: neutral T1 tilt, ACDF did not result in significantly increased ROM at any level (C2-3, C3-C4, C4-C5, C6-C7, C7-T1: p=NS). At increased T1 Tilt (+15°), motion was significantly increased at C2-C3 (p <.05); however, not at any other segment (p=NS). At decreased T1 tilt (-15°), there was a trend toward increased motion at C7-T1 (p=.06) and no significant increase in motion at any other level (p=NS). The GEE model did not show significant cumulative effects for the interaction of tilt and fusion on range of motion (p=NS). <h3>CONCLUSIONS</h3> Changes in cervical alignment have a biomechanical influence on the observed patterns of motion in both the intact state and following ACDF. In the unfused specimen, increased T1 tilt resulted in no significant hypermobility whereas decreased T1 tilt resulted in significantly increased hypermobility at five motion segments. Following ACDF, hypermobility was transferred to non-contiguous segments, cranially when T1 tilt was increased and trended caudally when T1 tilt was decreased. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

СПОСОБ ДИАГНОСТИКИ НЕСТАБИЛЬНОСТИ ПОЗВОНОЧНО-ДВИГАТЕЛЬНОГО СЕГМЕНТА ПРИ ОСТЕОХОНДРОЗЕ ШЕЙНОГО ОТДЕЛА ПОЗВОНОЧНИКА

Introduction. Instability — dislocation of the vertebrae, one of the forms of the motor segment dysfunction, causes pain and subsequent neurological disorders. There is a direct relationship between the data of the instability indicator and the clinical picture: the higher it is, the more pronounced the clinical manifestations of vertebral displacementare. And vice versa, conversely, its zero value (there is a functional block) coincides with rare exacerbations of the pain syndrome and a relatively satisfactory condition of the patient. Various types of vertebrae dislocation are much more common than is determined by functional radiography of the spine. As a rule, cervical dislocations are diagnosed already at a later date, when conservative measures are difficult and ineffective, and high-tech surgical treatment is requiring with certain material costs. Aim. To study the effectiveness of the developed method of functional radiography with weights for diagnosing instability of the spinal motion segment in the cervical spine. Materials and methods. 50 patients were under observation, the average age was 50.6 ± 2.19 years. All patients were admitted to the neurosurgical department of the clinic of the Irkutsk Scientific Center for Surgery and Traumatology with a diagnosis of adult osteochondrosis of spine (ICD M 42.1). Results. A comparative analysis of the study results of the effectiveness of X-ray methods for diagnosing instability of the spinal motion segment in the cervical spine revealed that the method of weight-bearing spondylography, where the percentage of verification was 68 %, was the most sensitive one. We have developed a formula for determining instability in the spinal motion segment: z = a + b · x – c · l, where z — indicator of instability of determined spinal motion segments; x — patient’s age; l — length of the cervical spine — the distance from the condyle of the lower jaw to the upper contour of the spinous process of the first thoracic vertebra — ThI, a, b, c — coefficients of linear dependence, obtained by the method of least squares by experimental-calculation (software-computing complex Table Curve 3D v4.0.01). The cervical dislocation was measured when the patient's neck was bent 45° forward (flexion) and 15° backward (extention). The obtained data were grouped according to the sex of the patients, and displacement of the vertebrae. This relationship shows that the maximum normal strain of the intervertebral discs is manifested at a neck flexion of 45°, extension of 15°, and with a load of 500 g, mounted on the patient’s head. A correlation between the length of the cervical spine and the age of patients was established, the correlation coefficient was rix = 0.58. The correlation dependence of the index of the cervical vertebrae instability and the age of patients was checked, the correlation coefficient was rix = 0,58. Correlation coefficients show a fairly high correlation between the length of the cervical spine and age of patients, the index of instability of the cervical vertebrae and age of patients, the index of instability of the cervical vertebrae and length of the neck of patients. The values of the coefficients used in the proposed formula are a = 11.13; b = 0.11; c = 0.45 were obtained by the least squares method experimentally and calculated based on a mathematical analysis of the results of studies of 50 patients. Conclusion. The method of functional weight-bearing spondylography makes it possible to reliably detect instability of the spinal motion segment, while the percentage of verification was 68%. The proposed formula of mathematical calculation helps to clarify the index of instability of the cervical spinal motion segment and can be used in practical work.

A Novel Technique of Endoscopic Anterior Transcorporeal Approach with Channel Repair for Adjacent Segment Disease After Anterior Cervical Discectomy and Fusion

To first report the application of percutaneous full-endoscopic anterior transcorporeal cervical discectomy (PEATCD) with channel repair for a patient with adjacent segment disease (ASD) after anterior cervical discectomy and fusion. PEATCD with channel repair was performed for a patient with ASD at the cranial level adjacent to previous fusion at the C5-C6 level. The pre- and postoperative clinical symptoms were evaluated with Japanese Orthopedic Association and visual analog scale (VAS). The radiological examinations included magnetic resonance imaging, computed tomography, and plain radiographs, which were used to evaluate the cervical alignment, stability, intraoperative decompression, and bony channel. The procedure was successfully completed within 70 minutes. The drainage tube was unnecessary. No surgery-related complications were recorded. The postoperative neck pain immediately improved to VAS 3 from preoperative VAS 6. The Japanese Orthopedic Association scores also took a turn for the better gradually from preoperative 10 to final 16 (improvement rate 85.7%). The muscle power recovered completely, and the Hoffman sign turned to negative during follow-up periods. Magnetic resonance imaging 1 week postoperatively showed a total removal of the herniation. The bony channel was almost disappeared on computed tomography images 3 months postoperatively. During postoperative periods, no relapse, channel collapse, bone plug migration, or instability was observed. As a novel and supplemental procedure for ASD after anterior cervical discectomy and fusion, PEATCD combines the advantages of transcorporeal approach and endoscopy together, which decreases iatrogenic damage to disc, preserves the cervical motion segment, and reduces surgical trauma. As the limitations of 1 case show, the effectiveness and reliability of PEATCD for patients with ASD should be verified in further studies.

Association of Spinal Manipulative Therapy With Changes in Cervical Motion Segment Interactions in Patients With Neck Pain: An Observational Study With Matched Asymptomatic Controls

ObjectiveThe objectives of this study were to determine (1) if maximal intervertebral range of motion (IV-RoMmax) and laxity interactions exist in the cervical spine during flexion, (2) if there are differences in IV-RoMmax or laxity parameters between baseline and follow-up in both patients with neck pain and asymptomatic controls, and (3) if there is an effect on IV-RoMmax/laxity relationships in patients with neck pain after spinal manipulative therapy. MethodsTwenty-nine patients with subacute or chronic neck pain and 33 asymptomatic controls were imaged during flexion and extension, pre and post a course of cervical chiropractic manipulation (patient group only), using a standardized quantitative fluoroscopy acquisition protocol. ResultsSignificant correlations between IV-RoMs were found in both neck pain and neck pain–free populations at baseline and follow-up. Positive relationships were found between C2-C3 and C3-C4 and C4-C5 and C5-C6 IV-RoM in both populations. A negative correlation was found in the patient group at baseline between C1-C2 and C5-C6, but not at follow-up. Significant relationships were also found for segmental laxity, with a negative correlation found at C1-C2 and C5-C6 in the patient group only and at baseline only. ConclusionDistinct relationships were found between both intraregional IV-RoM and laxity, many of which were present in both groups at baseline and follow-up, suggestive of normal kinematic behaviors. Changes in correlations unique to the patient group may be indicative of a change in regional kinematics resulting from the manipulation intervention. Spinal manipulative therapy may have a therapeutic effect by influencing cervical kinematics at the regional level.

Association of Chiropractic Colleges Research Agenda Conference 2021 Abstracts of Proceedings.

Association of Chiropractic Colleges Research Agenda Conference 2021 Abstracts of Proceedings.

Imaging Features of Cervical Spinal Motion Segment Lesions before and after Surgery: A Case Report

Spinal injuries remain a serious modern health problem that leads to a high level of disability and prehospital mortality. This clinical case of cervical fracture-dislocation demonstrates the diagnostic signs and the surgical approach.

Fate of Ossification of Posterior Longitudinal Ligament Following Anterior Cervical Fusion: Progression of Cervical Ossification of Posterior Longitudinal Ligament After Vertebral Body Sliding Osteotomy or Laminoplasty

In the treatment of ossification of posterior longitudinal ligament (OPLL)-induced cervical myelopathy, laminoplasty (LMP) is the most widely used surgical procedure. However, the progression of ossification masses is a well-known complication of LMP. This study aimed to investigate whether the novel anterior cervical decompression technique (vertebral body sliding osteotomy; VBSO) based on anterior column fusion suppresses the progression of OPLL compared with motion-preserving posterior decompression surgery (LMP). All 77 consecutive patients (VBSO group, n= 33; LMP group, n= 44) who underwent VBSO or LMP for cervical OPLL at our institute between January 2012 and November 2017 were included. A total of 62 and 86 cervical motion segments in the VBSO and LMP groups were investigated, respectively. The OPLL thickness was measured twice (immediate postoperative and final follow-up), and the change of OPLL thickness was compared between the 2 groups. The increase in OPLL thickness in the VBSO group (-0.18 ± 0.24 mm) was significantly smaller than that in the LMP group (1.0 ± 0.9 mm, P < 0.001). Interestingly, in some patients, suppressed OPLL progression and decreased OPLL thickness were observed. The solid fusion of the anterior column by VBSO is associated with the lower incidence of OPLL growth and potential for growth arrest.

The Value of Functional Multislice Computed Tomography in the Diagnosis of Instability of the Cervical Spinal Motion Segments

Objective. Instability of the vertebral motion segments is a very urgent problem of medicine, since it has very serious consequences. Today, search for optimal diagnostic methods continues. The authors propose a new diagnostic technique - functional multislice computed tomography (fMSCT). The objective of the study was to investigate the efficiency of the technique versus radiography. Material and methods . The new technique was used to examine 35 patients with a referral diagnosis of cervical spinal instability, who had previously undergone cervical spine radiography in the frontal and lateral projections. Results. Instability of the spinal motion joints in its clinical manifestations is similar to the hypermobility of the cervical spine. According to the results of fMSCT, the occurrence of signs of instability and hypermobility was assessed. When performing fMSCT, compression of the spinal canal was detected in 48.6% of patients, compression of the spinal roots was revealed in 85.7%. Violation of the integrity of the anterior and posterior support complexes was registered in 11.4% and 97.1% of patients, respectively. Conclusion . The developed fMSCT technique allows to accurately assess both the statics and dynamics of the spine and, unlike radiography, to diagnose ventral and dorsal vertebral displacements. The technique is recommended for widespread use in clinical practice.

Influence of loading in cervical spine motion segment and stress distribution

The aim of this study is to create a three-dimensional model of a cervical spine motion segment and to confirm it by inspecting the model with similar FE method. Initially a model was created by extracting CT scan images and the mesh was generated. FEM models of the lower cervical spine are derived from a CT scan with dissimilar elements and then quality of these models is evaluated with the help of mesh element-related metrics. Different material properties were assigned for each part of the model and then the analysis was carried out. Finite element analysis is used to find the effect of variations in morphology of spine, intervertebral disc height, slope of facet joint, process height of articular facet joint and segment size was parameterized. Ligament forces and vertebral rotation variations was also done as part of the FE study. The individual components of spine are subjected to different types of loading situations and the stresses developed on them need to studied. Some of the most important morphological variations found in the anatomy were disc segmental size & stress developed in the superior and inferior endplates and also the stress developed in the disc were analysed. The results obtained were collated with some external references and after validation of the model; the model could be used for extended similar studies.

Mechanical properties of cervical motion segments

Mechanical properties of cervical motion segments

Examining endplate fatigue failure during cyclic compression loading with variable and consistent peak magnitudes using a force weighting adjustment approach: an in vitro study

Repetitive movement is common in many occupational contexts. Therefore, cumulative load is a widely recognised risk factor for lowback injury. This study quantified the effect of force weighting factors on cumulative load estimates and injury prediction during cyclic loading. Forty-eight porcine cervical spine motion segments were assigned to experimental groups that differed by average peak compression magnitude (30%, 50% and 70% of predicted tolerance) and amplitude variation (consistent, variable). Cyclic loading was performed at a frequency of 0.5 Hz until fatigue failure occurred. Weighting factors were determined and applied instantaneously. Inclusion of weighting factors resulted in statistically similar cumulative load estimates at injury between variable and consistent loading (p > .071). Further, survivorship was generally greater when the peak compression magnitude was consistent compared to variable. These results emphasise the importance of weighting factors as an equalisation tool for the evaluation of cumulative low back loading exposures in occupational contexts. Practitioner summary: Weighting factors can equalise the risk of injury based on compression magnitude. When weighted, the cumulative compression was similar between consistent and variable cyclic loading protocols, despite being significantly different when unweighted and having similar injury rates. Therefore, assessing representative occupational exposures without evaluating task performance variability may underestimate injury risk. Abbreviations: FSU: functional spinal unit; UCT: ultimate compression tolerance

Percutaneous full-endoscopic anterior transcorporeal cervical discectomy and channel repair: a technique note report

BackgroundCompared to anterior cervical discectomy and fusion (ACDF), cervical motion segment and disc was retained through anterior transcorporeal herniotomy (ATH). But surgical field and manipulation in traditional ATH was restricted by the narrow channel. Percutaneous full-endoscopic transdiscal cervical discectomy is a minimally invasive and functional spine surgery. However, significant loss of intervertebral disc height was inevitable. This study was done to illustrate the feasibility, safety, and efficacy and present our surgical experience of percutaneous full-endoscopic anterior transcorporeal cervical discectomy (PEATCD) and channel repair (CR) for the treatment of cervical disc herniation (CDH).MethodsFour patients with CDH were chosen to undergo PEATCD and CR with a follow-up care for at least 22 months. The visual analogue score (VAS), Japanese Orthopedic Association (JOA), and modified Macnab criteria were recorded during the postoperative periods. CT images were obtained to observe the healing of the channel at 1 week and 3 months after the operation.ResultsThe average operating time was 83.75 min. Drainage tubes were unnecessary. No procedure-related complications occurred. The postoperative VAS and JOA scores were improved compared to those of the preoperative assessment. The clinical efficacy was excellent in 3 patients and good in 1 patient at final follow up stage according to the modified Macnab criteria. The hernia was removed completely in all patients according to postoperative MRI. Migration of the repair implementation and collapse of the drilled vertebrae were not observed during the postoperative periods. The bony channel was nearly absent on CT images obtained at 3 months postoperative.ConclusionThis is the first time that the anterior transcorporeal cervical discectomy and CR have been performed simultaneously under endoscopy. Less damage to disc and the retained cervical motion segment were achieved through this method. This is a feasible, safe, and minimally invasive procedure.Trial registrationNumbers: ChiCTR1800016383. Registered 29 may 2018. Retrospectively registered. Trial registry: Chinese Clinical Trial Registry.

Stiffness Matters

In vitro biomechanical testing of human cadaveric cervical and goat cervical motion segments. The aim of this study was to measure the effects of plate stiffness on load-sharing, instantaneous axis of rotation (IAR), and posterior element loading after anterior cervical discectomy and fusion (ACDF). ACDF is intended to create an environment, which facilitates sufficient stability and biomechanical conditions to promote bone formation. The relationship between cervical plate stiffness, load-sharing, and the IAR is complex. The ideal cervical plate is sufficiently stiff to limit interbody motion but is compliant enough to facilitate load-sharing rather than stress-shielding. Anterior cervical plates of distinct bending stiffnesses were applied to human and goat cervical motion segments following ACDF. A validated custom force-sensing interbody implant was placed in the disc space to measure load-sharing in the spine. Interbody loads, posterior element strain, and the IAR were measured during flexion/extension for each plate. Load-sharing in the interbody space, posterior element strain, and the location of the IAR were all significantly affected by plate stiffness. More compliant plates resulted in more load sharing, less posterior element strain, and a more dorsally located IAR relative to stiffer plates. A more compliant plate fosters more consistent load-sharing through the entire range of flexion/extension, which may promote faster bone formation and better fusion. A more compliant plate causes less posterior element strain, which may reduce facet joint loads and in turn reduce facet joint arthrosis. An ideal plate may be one that is stiff enough to minimize interbody motion and yet compliant enough to allow consistent load-sharing and minimal increase in posterior element strain. N/A.

The Feasibility of Optimal Surgical Result Prediction according to the Centre of Rotation Shift after Multilevel Cervical Total Disc Replacement

Objective: This study investigates the relation between shifted locations of centre of rotation (COR) at each cervical level and subsequent surgical outcomes after multilevel cervical total disc replacement (MCTDR) and identifies radiological parameter that corresponded to change of COR after MCTDR. Methods: The study included a consecutive series of 24 patients who were treated with MCTDR following diagnosis of multilevel cervical disc herniation or stenosis. Numeric rating scale (NRS), range of motion (ROM) at both C2-7 segment and TDR implanted levels, and the location of COR at TDR implanted level were evaluated at pre- and post-MCTDR. These parameters were compared between patients who experienced successful and unsuccessful pain relief.Results: The inherent CORs relatively at ventro-cranial coordinates have demonstrated significant migrations to dorso-caudal locations at each cervical levels, more prominent shifts for the successful group, after MCTDR switch. The unsuccessful group showed markedly reduced C2-7 ROM and reduced angular improvement at C2-7 as well as MCTDR level after surgery in comparison with the successful group. Postoperative C2-7 ROM was related to postoperative COR along the X-axis.Conclusions: The crucial determinants for clinical success after MCTDR, other than mere preservation of the ROM both at C2-7 and TDR implanted levels, was the restoration of COR from ventro-cranial location at degenerated cervical motion segment close to normal coordinates by posterior and inferior shifts after MCTDR. The position of COR along the X-axis after MCTDR was an important factor to determine maintenance of C2-7 RO.

Wednesday, September 26, 2018 7:35 AM–9:00 AM ePosters: P14. Variations among human spine segments and their relationships to in vitro kinematics: a retrospective analysis of experimental data including 581 cervical motion segments from 147 donor spines

BACKGROUND CONTEXT Kinematic data from in vitro flexibility tests involving cadaveric spines are often used to validate finite element models of human spine segments. However, data describing relationships between motion segment features (ie, dimensions of vertebrae and discs, subject height) and kinematics are lacking. PURPOSE To retrospectively investigate the relationships between cadaveric cervical spinal motion segments and their biomechanical characteristics, including coupled motion. STUDY DESIGN/SETTING Standard nondestructive in-vitro flexibility tests were performed on intact cervical spine segments (Occ-C3 and C3-T1). Relationships between donor spine features and in vitro kinematic parameters were studied using Pearson correlation and multiple regression analyses. PATIENT SAMPLE A total of 581 cadaveric cervical motion segments from 147 donor spines [86M/61 F, range: 20-69years, mean age 53.5+10.6years, BMD 0.558+0.101 g/cm2, mean height 173.4+12.0 cm]. OUTCOME MEASURES Spinal flexibility of intact motion segments were assessed using intervertebral mean range of motion (ROM) during flexion–extension (FE), lateral bending (LB, average right and left), and axial rotation (AR, average right and left). Coupled motion (CM), that is LB during AR (LB/AR) and AR during LB (AR/LB) were also assessed. METHODS General spine tissue donor information (age, gender, height, and weight at time of death) was obtained from medical histories provided by tissue banks. Bone mineral densities (BMD) were obtained from DEXA scans. Dimensions of vertebrae and discs were measured using ImageJ. Kinematic data were retrieved from studies involving intact testing of the fresh cervical spine segments (Occiput-T1), with all tests performed in the same lab using the same protocol. Loads of 1.5 Nm were applied while optoelectronically measuring intervertebral rotations in three planes (FE, LB and AR) at all spinal levels. Relationships between donor information (vertebrae and disc dimensions, subject height, weight, gender), bone quality (BMD) and kinematic data (ROM, CF LB/AR and CF AR/LB) were studied using Pearson correlation and multiple regression analyses (p RESULTS Overall values for ROM for intact motion segments were within typical values as reported in the literature. There were significant negative correlations between BMD and ROM, starting at C4–C5 and continuing caudally (R .4). Multiple linear regression analysis showed that ROM of cervical motion segments can be predicted using relationships between subject cervical level, gender, age, weight and/or BMD [FL-EX: R=0.321, P CONCLUSIONS Significant relationships exist between cervical spine segments’ dimensions, BMD and biomechanical properties (ROM and CM) at mid- and lower cervical levels. These relationships are of value during the validation process of finite element models involving human cervical spine segments, especially in studies focusing on motion preservation.

Thursday, September 27, 2018 3:35 PM–5:05 PM Section on Motion Technology Abstract Presentations: 135. Influence of preoperative segmental range of motion on postoperative motion after cervical disc arthroplasty using fixed-core, mobile-core and restrained compressible-core prostheses

Thursday, September 27, 2018 3:35 PM–5:05 PM Section on Motion Technology Abstract Presentations: 135. Influence of preoperative segmental range of motion on postoperative motion after cervical disc arthroplasty using fixed-core, mobile-core and restrained compressible-core prostheses