Anterior Cervical Plate System Research Articles

Development of a novel PLDLA/β-TCP composite-based biodegradable anterior cervical plate and screw system.

We investigated the effectiveness and safety of a new composite-based biodegradable anterior cervical plate/screw (ACPS) system for the anterior cervical discectomy and fusion (ACDF) fixation. A biocomposite in combination with 30 wt% β-tricalcium phosphate (β-TCP; a biodegradable ceramic having osteoconductive ability) and 70 wt% poly-l/d-lactide copolymer (PLDLA; a biodegradable polymer) was developed and used in the ACPS device, comprising one plate and four screws for fixation. Based on a literature review, a clinically required period of performance maintenance was set as 16 weeks, and to verify the performance for a period of 16 weeks or more, the test was conducted for 26 weeks. Following ISO 13781:2017 testing protocols, an in vitro degradation test was performed to verify the performance and evaluate the decomposition characteristics of the biodegradable ACPS system. Using an animal model as a preclinical investigation, the prepared ACPS device was implanted into five mongrel dogs weighing over 30 kg to evaluate the detachment prevention effect of the ACPS system on polyether ether ketone (PEEK) cage after ACDF. By week 26, the molecular weight was decreased by 45.35% for the plate and 52.56% for the screw; the bending strength of the plate was decreased by approximately 26.2% when compared with the initial stage. The torsional yield strength and pullout strength of the screw was increased by 52.31% and 5.3%, respectively by week 2 and then subsequently decreased until week 26. No detachment or dislocation of the inserted PEEK cage was observed for 26 weeks in vivo study. These findings recommend that the ACPS system might be a promising biodegradable tool for the fixation of interbody implants and supporting the fusion in an ACDF model. Furthermore, additional clinical trials are planned for the future.

Clinical Efficacy Analysis of the New PRUNUS Spine Plate System for Anterior Cervical Spine Surgery

Although the role of anterior cervical titanium plate system in stabilizing the spine sequence and promoting bone graft fusion has been widely recognized, more and more attention has been paid to the design of the plate itself and the complications caused by it. In order to solve the problems of poor stability of internal fixation, plate displacement and screw looseness, we designed the new PRUNUS spine plate system. Hence, the present study was conducted to describe observe and evaluate the clinical efficacy of a new type of three-leaf reinforced cervical anterior screw plate system (PRUNUS nailing system) developed for anterior cervical surgery. A retrospective analysis of 56 patients from June 2018 to October 2019 was used. Twenty-seven patients with cervical spine disease treated with new PRUNUS nail plate internal fixation were selected as the observation group, and 29 patients with cervical spine disease treated with conventional cervical anterior screw fixation were selected as the control group. Postoperative follow-up was performed. Cervical stability, internal fixation position and bone graft fusion were evaluated according to imaging data. The operative time, intraoperative blood loss, cervical Cobb angle, pain visual analogue scale (VAS), and Japanese orthopaedic association (JOA) were compared between the two groups. Spinal function scores and neurological improvement rates were used to evaluate the clinical efficacy of the new PRUNUS spine plate. The patients were followed up for 5-18months, with an average of 7.33months. The average operative time of the observation group was 98.4 ± 9.2 min, and the mean intraoperative blood loss was 65.3 ± 10.6ml, which were significant different from the control group's 109.7 ± 9.4 minutes (P < 0.05), 72.9 ± 15.6 ml (P < 0.05). Comparison between the two groups in postoperative and final follow-up of cervical Cobb angle, JOA score and improvement rate, VAS score and preoperative comparison showed no significant differences (P> 0.05). The new PRUNUS spine plate system can be applied to the anterior cervical spine surgery, and its clinical efficacy was similar to the traditional cervical anterior plate. But PRUNUS simplified the operation process, especially suitable for the surgical treatment of anterior cervical revision and osteoporosis patients.

Is the anterior cervical dynamic plate fixation better than the anterior static plate fixation: a retrospective review with over 5 years follow-up

BackgroundTo compare the clinical and radiologic outcomes after anterior cervical dynamic or static plate fixation for short segment cervical degenerative disc diseases (DDD) for more than 5 years.MethodsSixty-four patients who underwent anterior cervical one level discectomy or corpectomy with an anterior cervical plate system were followed for an average of 6.8 years for clinical and radiographic outcomes. Among the sixty-four patients, thirty-eight patients were fixed with a static plate (ORION and CSLP plate system) and the other twenty-six patients were fixed with a dynamic plate (ABC plate). Radiographic data were collected included the global sagittal alignment of the cervical spine (C2–C7), the local height and angle of the operated level pre-operatively, postoperatively and at last follow-up. A clinical assessment was performed at pre-operatively, three months postoperatively and final follow-up using the Japanese Orthopedic Association (JOA) /Visual Analogue Score(VAS)/ Neck Disablility Index(NDI) scoring system.ResultsThe mean follow-up time was 6.8 years. At final review, there were two cases of suspicious pseudarthrosis which were from ABC plate fixation group while the other cases all gained solid fusion. The height of fusion segment gained significantly improvement for both dynamic and static plate group post-operation, and all groups demonstrated a significant loss in height postoperatively. Generally, for the one level ACDF group, the height decrease was 0.5 mm for static plate and 1.6 mm for dynamic group which was significantly different(p < 0.05). And for one level ACCF group, this type of difference was not seen in which decreasing was 1.7 mm for static group and 1.8 mm for dynamic group. Segmental lordosis of the fusion segments was increased significantly both post-operation and final follow-up than before-operation for both one and two segments fusion. Global cervical lordosis from C2–C7 was increased in the early postoperative period in all groups, and at final follow-up the total lordosis was still getting better compared with early postoperative period, but this increase was not statistically significant. Clinical assessment of JOA/NDI showed that there was significantly improvement 3-month post-operation compared with pre-operation, and the score could get a slight further improvement at the final follow-up.ConclusionOur study demonstrated a statistically similar fusion rate between dynamic and static cervical plate fixation. However, the height gained with static plate fixation for single segment disease was maintained better than with dynamic plate fixation and there was no difference between JOA outcome scores between groups. Despite the reported improved biomechanics of dynamic plate fixation, further research needs to be done to show the clinical advantage of dynamic plate fixation.

Anterior cervical transpedicular screw fixation system in subaxial cervical spine: A finite element comparative study.

Multilevel cervical corpectomy has raised the concern among surgeons that reconstruction with the anterior cervical screw plate system (ACSPS) alone may fail eventually. As an alternative, the anterior cervical transpedicular screw (ACTPS) has been adopted in clinical practice. We used the finite element analysis to investigate whether ACTPS is a more reasonable choice, in comparison with ACSPS, after a 2-level corpectomy in the subaxial cervical spine. These 2 types of implantation models with the applied 75 N axial pressure and 1 N • m pure moment of the couple were evaluated. Compared with the intact model, the range of motion (ROM) at the operative segments (C4–C7) decreased by 97.5% in flexion-extension, 91.3% in axial rotation, and 99.3% in lateral bending in the ACTPS model, whereas it decreased by 95.1%, 73.4%, 96.9% in the ACSPS model respectively. The ROM at the adjacent segment (C3/4) in the ACTPS model decreased in all motions, while that of the ACSPS model increased in axial rotation and flexion-extension compared with the intact model. Compared to the ACSPS model, whose stress concentrated on the interface between the screws and the titanium plate, the stress of the ACTPS model was well-distributed. There was also a significant difference between the maximum stress value of the 2 models. ACTPS and ACSPS are biomechanically favorable. The stability in reducing ROM of ACTPS may be better and the risk of failure for internal fixator is relatively low compared with ACSPS fixation except for under lateral bending in reconstruction the stability of the subaxial cervical spine after 2-level corpectomy.

Device profile of the sapphire XTM anterior cervical plate system: overview of its safety and efficacy

ABSTRACT Introduction:The Sapphire X Anterior Cervical Plate System is a new medical device designed to provide stability after anterior discectomy and fusion procedures. It has unique benefits over many of the more established plates on the market. It is manufactured predominantly from titanium alloy and was first launched in late 2020. Areas covered:The structure and unique features of the Sapphire X are described. The indications for its use are discussed. The delivery system designed for the plate is reviewed in detail. Research outlining the shortcomings of current plate technologies and alternative technologies in this market space are reviewed. Expert Opinion:The evidence in this article demonstrates the risk of adjacent-level ossification development (ALOD) with current cervical plate designs. The industry is saturated with cervical plate technologies, yet there are very few plates small enough to avoid encroaching upon adjacent levels of disc space, particularly in the upper subaxial cervical segments and in patients with small vertebrae. This device review demonstrates the successful application of a cervical plate device that is small enough to avoid encroachment on the adjacent-level disc spaces while providing immediate stability after discectomy and fusion in the cervical spine.

Structure Design and Optimization of the C5-C6 Cervical Intervertebral Fusion Cage Using the Anterior Cervical Plate and Cage Fixation System.

BackgroundThe fifth and sixth cervical vertebra (C5–C6) is the most easily injured segment encountered in clinical practice. The anterior cervical plate and cage (ACPC) fixation system is always used to reconstruct the intervertebral height and maintain the segmental stability. The postoperative effect, such as subsidence, neck pain, and non-fusion, is greatly affected by the cervical cage structure design. This study determined reasonable structure size parameters that present optimized biomechanical properties related to the postoperative subsidence often accompanied with ACPC.Material/MethodsTwenty bionic cages with different structural sizes (distance between the center of the cage and groove, groove depth, and groove width) were designed and analyzed based on the regression optimization design and analysis method combined with FE analysis. Because a previous study showed that greater stresses on the endplate are associated with higher risk of subsidence, the optimization object was selected as the stresses on endplate to lower it.ResultsThe postoperative stresses on the endplate of all cages with bionic structure design were proved to be lower than with the original one. The optimal structure size was the distance between the center of the cage and groove=0 mm, groove depth=3 mm, and groove width=4 mm. Regression analysis found the cage with optimized bionic structural parameters resulted in a 22.58% reduction of endplate stress response compared with the original one.ConclusionsThe bionic cage with optimized structural sizes can reduce the subsidence risk, suggesting that the optimization method has great potential applications in the biomechanical engineering field.

Biomechanical comparison of the angle of inserted screws and the length of anterior cervical plate systems with allograft spacers

BackgroundComparative studies of the biomechanical effects of plates of varying lengths and different screw insertion angles on allograft spacers are lacking. MethodsFinite element model analysis of a previously validated, three-dimensional, intact cervical spinal segment model of C3–6 was conducted in the present study. On the C5–6 segment, anterior discectomy and fusion were performed using allograft spacers and different combinations of anterior plates and screws. The biomechanical characteristics of combinations of short, medium, and maximal length plates with screw insertion angles of 0°, 8°, 16°, and 32° were analyzed. FindingsIn flexion and extension, the risk of allograft spacer subsidence decreased as screw angles increased. Short plates with a screw insertion angle of 32° posed the lowest subsidence risk, similar to medium length plates with a screw insertion angle of 16°, in all motion conditions. The risk of bone yielding increased as plate length increased, but decreased as the screw insertion angle increased. InterpretationShort plates with a large screw insertion angle (32°) showed the highest mechanical stability and load sharing of allograft spacers and the lowest risk of screw loosening. Accordingly, we recommend the use of a short plate and large screw insertion angle for anterior cervical discectomy and fusion.

Regional bone mineral density differences measured by quantitative computed tomography in patients undergoing anterior cervical spine surgery

BACKGROUND CONTEXTClinically, the association between bone mineral density (BMD) and surgical instrumentation efficacy is well recognized. Although several studies have quantified the BMD of the human lumbar spine, comprehensive BMD data for the cervical spine is limited. The few available studies included young and healthy patient samples, which may not represent the typical cervical fusion patient. Currently no large scale study provides detailed BMD information of the cervical and first thoracic vertebrae in patients undergoing anterior cervical spine surgery. PURPOSEThe objective of this study was to determine possible trabecular BMD variations throughout the cervical spine and first thoracic vertebra in patients undergoing anterior cervical discectomy and fusion (ACDF) and to assess the correlation between BMDs of the spinal levels C1–T1. STUDY DESIGN/SETTINGThis is a retrospective case series. PATIENT SAMPLEPatients undergoing ACDF from 2015 to 2018 at a single, academic institution with available preoperative CT imaging were included in this study. OUTCOME MEASURESThe outcome measure was BMD measured by QCT. METHODSPatients that underwent ACDF from 2015 to 2018 at a single, academic institution were included in this study. Subjects with previous cervical instrumentation or missing/incomplete preoperative cervical spine CT imaging were excluded. Asynchronous quantitative computed tomography (QCT) measurements of the lateral masses of C1 and the C2-T1 vertebral bodies were performed. For this purpose, an elliptical region of interest that consisted exclusively of trabecular bone was selected. Any apparent sclerotic levels that might affect trabecular QCT measurements were excluded from the final analysis. Interobserver reliability of measurements was assessed by calculating the interclass correlation coefficients (ICC). Pairwise comparison of BMD was performed and correlations between the various cervical levels were evaluated. The statistical significance level was set at p<.05. RESULTSIn all, 194 patients (men, 62.9%) met inclusion criteria. The patient population was 91.2% Caucasian with a mean age of 55.9 years and mean BMI of 28.2 kg/m2. The ICC of cervical QCT measurements was excellent (ICC 0.92). The trabecular BMD was highest in the mid-cervical spine (C4) and decreased in the caudal direction (C1 average=253.3 mg/cm3, C2=276.6 mg/cm3, C3=272.2 mg/cm3, C4=283.5 mg/cm3, C5=265.1 mg/cm3, C6=235.3 mg/cm3, C7=216.8 mg/cm3, T1=184.4 mg/cm3). The BMD of C7 and T1 was significantly lower than those of all other levels. Nonetheless, significant correlations in BMD among all measured levels were observed, with a Pearson's correlation coefficient ranging from 0.507 to 0.885. CONCLUSIONSTo the authors’ knowledge this is the largest study assessing trabecular BMD of the entire cervical spine and first thoracic vertebra by QCT. The patient sample consisted of patients undergoing ACDF, which adds to the clinical relevance of the findings. Knowledge of BMD variation in the cervical spine might be useful to surgeons utilizing anterior cervical spine plate and screw systems. Due to the significant variation in cervical BMD, procedures involving instrumentation at lower density caudal levels might potentially benefit from a modification in instrumentation or surgical technique to achieve results similar to more cephalad levels.

Development and Clinical Application of a New Open-Powered Nail Anterior Cervical Plate System.

ObjectiveTo observe and evaluate the clinical curative effect of a new type of open‐powered cervical spine system developed for anterior cervical surgery.MethodsA retrospective analysis was performed in our hospital in 2015–2017 of 329 orthopaedic patients treated with cervical anterior decompression, cage or titanium mesh graft fusion, new open‐powered nail plate or traditional cervical anterior screw plate. A total of 154 (control group) and 175 (observation group) cases were fixed with conventional cervical‐ and new open‐powered nail plates, respectively. Postoperative follow‐up was performed. Cervical stability, internal fixation position, and bone graft fusion were evaluated by imaging. Operative time, intraoperative blood loss, cervical Cobb angle, pain visual analogue scale (VAS) score, and Japanese orthopaedic association (JOA) score were compared between the groups. JOA scoring (spinal cord function) and neurological function improvement rate (IR) were used to assess clinical efficacy.ResultsThe patients were followed up for 8–36 months with an average of 19.48 months. There was no significant difference in the operation time and intraoperative blood loss between the two groups (P > 0.05). In the control group, the Cobb angles of the cervical spine were 5.13° ± 1.28°, 10.46° ± 1.07°, and 9.72° ± 1.43° before and after the operation. The observation group was followed by the Cobb angle of the cervical spine before and after the operation. They were 4.96° ± 1.39°, 11.67° ± 0.93°, and 11.13° ± 1.19°, respectively; the JOA scores before the operation, 1 week after the operation, and at the last follow‐up were (8.07 ± 1.13) points and (13.57 ± 0.82) points, and (14.19 ± 0.96) points, respectively; the IR was 86.52% ± 9.33%. The preoperative, postoperative 1 week, and last follow‐up JOA scores in the observation group were (8.37 ± 1.29) points, (14.11 ± 0.93) points, and (14.95 ± 0.78) points respectively. The IR was 88.74% ± 8.16% in the scores; the VAS scores were (5.54 ± 0.89) points, (1.73 ± 0.71) points, and (1.48 ± 0.52) points in the preoperative, postoperative 1 week, and last follow‐up in the control group. The VAS scores were (5.81 ± 0.94) points, (1.82 ± 0.61) points, and (1.16 ± 0.49) points before, 1 week, and after the final follow‐up. The JOA score and IR, VAS score and preoperative comparison between the two groups were statistically significant (P < 0.05), but there was no statistically significant difference between the two groups (P > 0.05).ConclusionThe new open‐powered nail anterior cervical plate system can achieve the same clinical effect as the traditional anterior cervical plate fixation in anterior cervical surgery, but it can simplify the operation process, effectively make up for the shortcomings of the traditional anterior cervical plate operation, and obtain satisfactory clinical application effect, which is worthy of clinical promotion.

Cervical sagittal alignment as a predictor of adjacent-level ossification development.

PurposeTo explore the role of cervical sagittal alignment in the occurrence of adjacent-level ossification development (ALOD) in patients who underwent anterior cervical discectomy fusion with self-locking stand-alone polyetheretherketone cage, and the relationship between cervical sagittal alignment and clinical outcomes.BackgroundBecause of its advantages, anterior cervical plating systems have been used as the classic surgical method in the treatment of patients with cervical disc herniation. However, the proximity (<5 mm) of the plate to the adjacent disc space has proven to be a critical risk factor for ALOD. How cervical sagittal alignment influences the development of ALOD is unknown and its role in ALOD needs clarification.Patients and methodsOne hundred and eighteen adults who underwent anterior cervical discectomy fusion with self-locking stand-alone polyetheretherketone cage for cervical radiculopathy or myelopathy between December 2013 and December 2015 were retrospectively recruited. Of these, 15 patients developed ALOD and 103 patients did not, representing two groups for comparison. The cervical sagittal parameters were measured, including C2–C7 Cobb angle (Cobb), fused segment angle, cervical tilt (CT), T1 slope (T1S) and C2–C7 sagittal vertical axis. Clinical outcomes and efficacy were evaluated using a visual analog scale, Japanese Orthopedic Association (JOA) score and neck disability index (NDI) score before and after surgery.ResultsThere were no significant differences in patient demographics between the two groups. Cobb value (P<0.05), CT (P<0.05) and T1S (P<0.05) were significantly different between the two groups, while fused segment angle (P>0.05) and C2–C7 sagittal vertical axis (P>0.05) showed no difference. Compared with preoperative scores, improvement was seen in postoperative visual analog scale, JOA and NDI scores at each time point (P<0.05). However, the postoperative scores at 24 months in the NO-ALOD group indicated greater improvements compared with the ALOD group (P<0.05). There were significant correlations between Cobb and CT (r=0.607, P<0.05) and CT and T1S (r=0.681, P<0.05). Also, T1S was significantly correlated with clinical outcomes (JOA: r=0.689, P<0.05; NDI: r=−0.710, P<0.05).ConclusionMaintaining a lordotic cervical sagittal alignment was related to a lower risk of ALOD and improved clinical outcomes.

A comparison of a self-locking stand-alone cage and anterior cervical plate for ACDF: Minimum 3-year assessment of radiographic and clinical outcomes

ObjectivesThe self-locking stand-alone cage has been clinically applied in treating cervical degenerative disc disease (CDDD). However, no long-term clinical and radiographic studies have been performed so far. This retrospective study was designed to analyze and compare the efficacy and outcomes of anterior cervical discectomy and fusion (ACDF) using self-locking stand-alone cages and cages with the anterior cervical plating system. Patients and methodsA total of 98 consecutive patients were recruited in this study. Patients in the cage group were given stand-alone self-locking cages, and patients in the plate group were treated with cages and anterior plate fixation. The operative time, intraoperative blood loss and complications were recorded. Clinical outcomes were evaluated using the JOA scoring system, Neck Disability Index and Odom’s criteria. The cervical lordosis, subsidence and cervical fusion status were assessed by X-ray and computed tomography. ResultsThe mean follow-up period was 39.7 months in the cage group and 42.2 months in the plate group. The operative time, intraoperative blood loss, postoperative dysphagia, sore throat and adjacent segment degeneration in the cage group were significantly less than those in the plate group (p < 0.05). All the patients in both groups achieved complete interbody fusion. Postoperative JOA and NDI scores in both groups were obviously improved compared with the preoperative ones. The postoperative cervical lordosis was effectively restored in both groups. ConclusionsThe self-locking stand-alone cage for ACDF could effectively restore the cervical physiological curvature, cause few complications, and lead to satisfactory outcomes. Therefore, it could be used as an effective and reliable treatment for the CDDD.

Anterior cervical discectomy and fusion: review and update for radiologists.

The goals of this article are to describe the various types of interbody grafts and anterior cervical plating systems, techniques for optimizing evaluation of cervical spine metallic implants on CT and MR imaging, expected appearance and complications of ACDF on postoperative imaging and imaging assessment of fusion. Optimization for optimizing metal induced artifacts. Currently, ACDF is the most commonly performed surgical procedure for degenerative cervical spine disease. Interbody fusion is performed with bone grafts or interbody spacers, and may be supplemented with anterior cervical plating. Compressive pathologies at the vertebral body level may be addressed by simultaneous corpectomy. Postoperatively, imaging plays an integral role in routine screening of asymptomatic individuals, fusion assessment and evaluation of complications.

The Effect of the Anterior Cervical Plate System on Adjacent Segments: Fact or Fiction?

The Effect of the Anterior Cervical Plate System on Adjacent Segments: Fact or Fiction?

A Biomechanical Evaluation of a Versatile and Novel Anterior Cervical Fusion Device Possessing Modular and Integrated Fixation Capabilities

IntroductionA novel ACDF (anterior cervical discectomy and fusion) construct possessing integrated screw and modular plate fixation (MPF) capabilities has been introduced in an effort to provide versatility when selecting a stabilization mechanism. Construct features allow the surgeon to switch between zero-profile (2 screws), half-plate (3 screws), and full-plate (4 screws) system. Inherently, the device can be readily adapted to the patient's anatomical landscape, accommodating adjacent level fixation, as well as diminishing hardware prominences when necessary. Additionally, the MPF technology, which creates a singular rigid body about the index level, affords ideal plate orientation/alignment, eliminates potential for cage migration/subsidence, and ensures physiological compression of the cage/graft. However, the translated effects of such novel features on segmental stability have not yet been characterized in the literature. The objective of this study was to assess the segmental rigidity achieved by the novel ACDF device iterations as compared with traditional ACDF (cage and anterior cervical plate system) and supplementation with posterior cervical constructs with lateral mass screws (LMS). Material and MethodsEighteen human cervical spine specimens (C3-T1) were tested. Osseous integrity was confirmed via DEXA scans and radiographs. Specimens were divided into three groups (n = 6) such that the mean bone quality across each group was consistent. The C3 and T1 vertebral bodies were potted. Each spine was first tested in an intact state. An anterior discectomy (C5/C6) was then performed, followed by sequential iterative construct instrumentation and testing (see Results for sequence). The three group protocol was executed such that each respective group would receive only integrated zero-profile, integrated half-plate, or integrated full-plate fixation (Alta ACDF System – Zimmer-Biomet Spine); diminishing vertebral body compromise due to excessive screw removal/placement. For posterior supplemented constructs, lateral mass screws (Lineum – Zimmer-Biomet Spine) were placed bilaterally at the index level. A 2Nm moment was applied in flexion-extension (FE), lateral-bending (LB), and axial-rotation (AR) using a six degree-of-freedom Bionix® Spine Kinematics System (MTS, Systems, MN). Segmental range-of-motion (ROM) was tracked using Optotrak Certus (NDI, Inc, Canada) motion analysis software. Mean ROM relative to intact conditions (100%) was measured. ResultsROM (% Intact): FE/LB/AR. Integrated Zero Profile ACDF (n = 6): 69 / 48 / 76. Integrated Half-Plate ACDF (n = 6): 42/ 25 / 67. Integrated Full-Plate ACDF (n = 6): 32 / 29 / 40. Traditional ACDF (n = 18): 37 / 39 / 61. Traditional ACDF + LMS (n = 18): 12 / 11 / 22. Integrated Zero Profile ACDF + LMS (n = 6): 14 / 13 / 31. Integrated Half-Plate ACDF + LMS (n = 6): 18 / 10 / 31. Integrated Full-Plate ACDF + LMS (n = 6): 12 / 10 / 16. ConclusionThe full-plate and half-plate constructs both appeared advantageous in comparison to the traditional ACDF construct (MaxAn – Zimmer-Biomet Spine) when used without posterior supplementation, demonstrating an inherent benefit of the MPF technology. Motion reductions with zero-profile fixation were not as robust; however, it can be argued that clinically significant stability was still achieved. Lastly, supplemental fixation with LMS appeared to be a clear leveling factor across all constructs, facilitating significant motion reduction in all directions.

Three-dimensional finite-element study on anterior transpedicular screw fixation system of the subaxial cervical spine

To evaluate the biomechanical effects of the anterior cervical transpedicular-screw system (ACTPS), compared to the anterior cervical screw plate system (ACLP), in the subaxial cervical spine after 2-level corpectomy. A verified intact finite element subaxial cervical (C3-C7) model was established and analyzed by Mimics 10.0, Rapidform XOR3, Hypermesh 10.0, CATIA5V19, ANSYS 14.0 softwares based on the CT data (C1-T1) was collected from a 28 years old male volunteer. The axial force of 75 N and moment couple of 1N·m was loaded on the upper surface of C3, which made the model movement in flexion extension, lateral bending, rotating direction, respectively. Then, recorded the range of motion, and compared the results with the in vitro biomechanical experimental data to verify the effectiveness of the model. The ACTPS model and the ACLP model were analyzed using the finite element method. The range of motion at the operation segments (C4-C7), the range of motion at the adjacent segment (C3-C4) and stress distribution under flexion, extension, lateral bending, and axial rotation were calculated, and compared the range of motion with intact model. There were 85,832 elements and 23,612 nodes in the intact model of subaxial cervical spine (C3-C7) in this experiment,and the range of motion of intact model validated with the reported cadaveric experimental data. In ACTPS group the stress was been well-distributed, but the stress concentrated on the interface between screw and the titanium plate in ACLP group. There were obvious differences of the maximum stress value between the two groups. The range of motion of fixed segments in ACTPS group was smaller than ACLP group, however adjacent segment range of motion showed no significant difference. Compared with the intact group, the range of motion in flexion extension, lateral flexion, rotation direction was decreased respectively about 25°, 20° and 8°, the range of motion at adjacent segment (C3-C4) was correspondingly compensated about 0.3°, 3° and 0.1°. ACTPS is better than ACLP in terms of biomechanical properties. It offers rigid stability, and may be more suitable for reconstruction stability of 2-level and more than 2 levels corpectomy in the subaxial cervical spine. Meanwhile, the risk of fracture of ACTPS system is lower than that of the ACLP system.

Zero-profile integrated plate and spacer device reduces rate of adjacent-level ossification development and dysphagia compared to ACDF with plating and cage system

Retrospective case-control study. To compare the safety and efficacy of the Zero-profile (Zero-p) integrated plate and spacer device to that of an anterior cervical plate and cage in patients undergoing anterior cervical discectomy and fusion (ACDF). Anterior cervical plating system has provided good results, including higher fusion rate and improved alignment since its use. However, adjacent-level ossification development (ALOD) and dysphagia have been usually reported associating with plates. This was a retrospective control study. Sixty-two patients with cervical radiculopathy or myelopathy were treated with an anterior plate and cage or Zero-p implant between January 2011 and December 2011. The mean follow-up was 33.1months in the plate and cage group and 30.6months in Zero-p group. Patient demographics, operative details and complications were reviewed. The clinical outcomes were evaluated using the Japanese Orthopaedic Association (JOA) scores and JOA recovery rate before and after operations. Incidence of cephalad and caudal ALOD on the lateral radiographs was studied at preoperation, immediate postoperation and last follow-up. Incidence of dysphagia was also recorded after operation according to Bazaz-Yoo dysphagia index. Thirty-two patients received an anterior plate and cage and 30 received the Zero-p implant. There were no statistical differences in patient demographics, operative details between the two groups. The JOA scores significantly increased compared with preoperational measurements in both groups (p < 0.05), but the JOA recovery rate was similar (72.2% for plate and cage group and 77.0% for Zero-p group, p >0.05). ALOD occurred in 12 (18.8%) of the 64 cephalad and caudal adjacent segments in plate with cage group, and only 1 (1.6%) of 63 adjacent levels (including three noncontiguous cases) presented with ALOD in Zero-p group. The difference was significant (p < 0.01). The incidence of dysphagia in the Zero-p group was lower compared with that in the plate with cage group, and the symptom duration was much shorter (p < 0.01). Both groups had no adverse events associated with the implant or implant surgery. The Zero-profile implant is safe and efficacious after ACDF. It can reduce the rate of adjacent-level ossification development and dysphagia compared to anterior plate and cage.

Optimal screw orientation for the fixation of cervical degenerative disc disease using nonlinear C3-T2 multi-level spinal models and neuro-genetic algorithms.

Anterior cervical discectomy and fusion is a common surgical procedure performed to remove a degenerative or herniated disc in cervical spine. Unfortunately, clinical complications of anterior cervical plate (ACP) systems still occur, such as weak fixation stability and implant loosening. Previous researchers have attempted to ameliorate these complications by varying screw orientations, but the screw orientations are mainly determined according to the investigator's experiences. Thus, the aim of this study was to discover the optimal screw orientations of ACP systems to achieve acceptable fixation stability using finite element simulations and engineering algorithms. Three-dimensional finite element models of C3-T2 multi-level segments with an ACP system were first developed to analyze the fixation stability using ANSYS Workbench 14.5. Then, artificial neural networks were applied to create one objective function, and the optimal screw orientations of an ACP system were discovered by genetic algorithms. Finally, the numerical models and the optimization study were validated using biomechanical tests. The results showed that the optimal design of the ACP system had highest fixation stability compared with other ACP designs. The neuro-genetic algorithm has effectively reduced the time and effort required for discovering for the optimal screw orientations of an ACP system. The optimum screw orientation of the ACP system could be successfully discovered, and it revealed excellent fixation stability for the treatment of cervical degenerative disc disease. This study could directly provide the biomechanical rationale and surgical suggestion to orthopedic surgeons.

Malaligned dynamic anterior cervical plate: a biomechanical analysis of effectiveness.

Biomechanical evaluation. To evaluate the kinematic and load-sharing differences of dynamic anterior cervical plates when placed in-line at 0° and off-axis at 20°. The use of dynamic anterior cervical plating systems has recently gained popularity due to the theoretical benefit of improved load sharing with graft subsidence. Occasionally, due to anatomical restraints, the anterior cervical plate may be placed off-axis in the coronal plane. This may potentially decrease the dynamization capability of the plate, leading to less load sharing and potentially decreased fusion rates. The purpose of this study was to comprehensively evaluate the kinematic and load-sharing differences of a dynamic plate placed in-line versus off-axis in the coronal plane. Thirteen fresh-frozen human cadaveric cervical spines (C2-T1) were used. Nondestructive range-of-motion testing was performed with a pneumatically controlled spine simulator in flexion/extension, lateral bending, and axial rotation using the OptoTrak motion measurement system. A C5 corpectomy was performed, and a custom interbody spacer with an integrated load cell collected load-sharing data under axial compression at varying loads. A dynamic anterior cervical plate was placed in-line at 0° and then off-axis at 20°. Testing conditions ensued using a full-length spacer, followed by simulated subsidence by removing 10% of the height of the original spacer. There were no kinematic differences noted in the in-line model versus the off-axis model. After simulated subsidence, the small decreases in stiffness and increases in motion were similar whether the plate was placed in-line or off-axis in all 3 planes of motion. There were also no significant differences in the load-sharing characteristics of the in-line plate versus the off-axis plate in either the full-length model or the subsided interbody model. This study suggests that off-axis dynamic plate positioning does not significantly impact construct kinematics or graft load sharing. As such, we do not recommend removal or repositioning of an off-axis placed dynamic plate because the kinematic and load-sharing biomechanical properties are similar. N/A.

Biomechanical Comparison of Different Vertebral Plate Designs for Anterior Cervical Discectomy and Fusion Using Nonlinear C3-T2 Multi-Level Spinal Models

ABSTRACTAnterior cervical discectomy and fusion is a common surgical procedure to treat spinal cord or nerve root compression. However, the clinical complications of anterior cervical plate system still occur. Past researchers have tried to improve the clinical complications by changing the screw thread or the screw orientation. The conclusion on the screw thread is quite consistent. Unfortunately, the studies on the screw orientation reached inconsistent conclusions. In addition, the effects of the screw orientation which are determined before the surgery are mainly based on the surgeon's experiences without biomechanical evidences. Therefore, the purpose of this study was to investigate the clinical performances of anterior cervical plate for the anterior cervical discectomy and fusion. Three-dimensional nonlinear finite element model, which consisted of C3-T2 multi-level spine and anterior cervical plate system, was developed to investigate the fixation stability by using ANSYS Workbench 14.5. Six desi...

An Atypical Case of Melena Caused by Esophageal Perforation

Introduction: Anterior cervical spine surgery (ACSS) is a widely accepted surgical approach by both orthopedic and neurosurgeons for many common conditions like degenerative disk disease, spondylosis, trauma, vertebral body collapse secondary to metastatic disease, osteomyelitis, discitis, or disc herniation. One rare complication of ACCS is esophageal damage or perforation. We present a case of esophageal perforation years after ACCS that presented as melena. A 54-year-old female with past medical history significant for motor vehicle accident causing small bowel perforation requiring small bowel transplantation 1 year ago, ACCS at the C6-C7 level 1.5 years ago who was admitted with concerns of three days of black, tarry stools and found to be anemic with Hgb of 6.0. On admission, patient denied hematochezia, dysphagia, regurgitation, odynophagia, chest pain, shortness of breath, pleuritic pain, shoulder or arm pain. Patient underwent an EGD that showed erosions around a fixed, metal foreign body at 20cm from incisors determined to be cervical plate from her cervical hardware. No other site of bleeding was identified during endoscopy. Patient was evaluated immediately by ENT, plastic surgery, neurosurgery and orthopedic teams. After consultation, evaluation and discussion between all the surgical and primary teams, patient first underwent repair and reconstruction of the esophageal wall (pharyngoplasty and cricopharyngeal myotomy and flap reconstruction of the pharynx) followed by removal of anterior cervical plate, screws and DePuy Skyline system. Patient had a complicated postop course with multiple wound infections and required a 2 month hospitalization stay. The incidence of esophageal injuries after ACSS is noted to be between 0 and 3.4%, mostly with injury noted intraopeartively in 77% of cases, known as early injuries. Early injuries are usually iatrogenic. Delayed cases typically manifest years after surgery and are due to chronic compression, dislocation, or migration of the bone graft. As in our patient’s case, the typical area susceptible for esophageal perforation is at the level of C5-6, known as the Killian triangle. Late presentations of esophageal perforation may present as odynophagia, hoarseness, aspiration, wound infection, neck swelling after drinking water, unexplained tachycardia and blood in the nasogastric. We present an unusual presentation of melena caused by esophageal perforation. It is important to keep this rare complication in differential when managing a patient with history of ACCS as imaging to evaluate for pneumomediastinum should be obtained first if there is high clinical suspicion.