Relationship between Cervical Curvature and Spinal Drift Distance after Laminectomy with Screw Fixation and Its Effect on Clinical Outcome / 中国康复理论与实践

Objective:To observe the relationship between cervical curvature and spinal drift distance after laminectomy with lateral mass screw fixation, and its effect on clinical outcome. Methods:From January, 2017 to October, 2018, a total of 117 patients with cervical spondylotic myelopathy (CSM) underwent laminectomy with lateral mass screw fixation, and 90 of them completed the follow-up. According to the patients' cervical curvature (CC), they were divided into three groups: those CC between 0° to 5° were in Group A (n = 28), 5° to 16.5° in Group B (n = 36) and CC > 16.5° in Group C (n = 26). The spinal drift distance, nerve recovery, axial symptoms and C5 palsy were recorded and analyzed. Results:There were significant differences in CC and spinal drift distance (F > 152.119,P < 0.001), and no significant difference was found in laminectomy width and incidence of C5 palsy (P > 0.05) among three groups. The Japanese Orthopaedic Association (JOA) score significantly increased in all the groups post operation and at the last follow-up (t > 8.869,P < 0.001), and no significant difference was found among there groups at the same time (P > 0.05), as well as the incidence of C5 palsy (F = 0.472,P = 0.625). There was significant difference in the score of Visual Analogue Scale of axial symptoms among three groups (F > 34.800,P < 0.001), which was lower in groups B and C than in group A (t > 5.845,P< 0.001), and no significant differene was found between group B and group C. Conclusion:On the basis of the same laminectomy width, the greater the CC was, the more favorable the spinal drift went backwards. The loss of CC was related to the occurrence of axial symptoms, but was not correlated with the neurological recovery and C5 palsy.

Relationship between different cervical curvature and spinal cord posterior movement after laminectomy with lateral mass screw fixation and its influence on the operative effect / 中国综合临床

Objective@#To investigate the relationship between cervical curvature (CC) and spinal drift distance after laminectomy with lateral mass screw fixation and the influence on the operative effect.@*Methods@#From October 2016 to December 2017, a total of 85 patients with cervical spondylotic myelopathy (CSM) underwent laminectomy with lateral mass screw fixation in handan central hospital, and 78 patients were followed up completely.After the operation, according to the Harrison method, they were divided into 2 groups(Group A (43 cases, 0°≤CC≤16.5°); Group B (35 cases, CC>16.5°)). The spinal drift distance, nerve recovery, axial symptoms and C5 palsy in the groups were recorded and analyzed.@*Results@#The CC was 8.5°±3.8° in group A and 19.6°±3.0° in group B (t=14.071, P=0.000). The laminectomy width in group A was (22.1±1.7) mm, in group B was (21.8±1.5) mm, the difference between the two groups was not statistically significant (P>0.05). The distance of spinal cord backward movement was (1.7±0.4) mm in group A and (3.2±0.7) mm in group B. There was significant difference between the two groups (t=11.879, P<0.001). At the end of one year, the improvement rates of nerve function in the two groups were (63.3±13.1)% and (65.1±13.9)% respectively, there was no significant difference between the two groups (t=0.587, P=0.559). The VAS score of group A was (5.2±1.3) at one week and (3.5±0.6) at one month after operation, and that of group B was (3.8±0.8) and (2.4±0.4) respectively.There were statistically significant differences between groups at different time points (t=5.567, P<0.001; t=9.289, P<0.001). The incidence of C5 paralysis was 7.0% (3/43) in group A and 11.4% (4/35) in group B. There was no significant difference between the two groups (P>0.05).@*Conclusion@#The greater the curvature of cervical spine is, the more fully the spinal cord moves backward.The loss of curvature of cervical spine is related to the occurrence of axial symptoms.The curvature of cervical spine is not related to the recovery of nerve function and the occurrence of C5 nerve paralysis.

An Osteological Study Of Arcuate Foramen In Atlas And Its Clinical Significance

Background: Atlas, first cervical vertebra bears sulcus over posterior arch for third part of vertebral artery.Sometimes an osseous bridge converts the sulcus into a foramen called as Arcuate foramen. It is commonlycalled as Kimmerle’s anomaly, also known as Ponticulus Posticus. It is the product of the complete or incompleteossification of the posterior atlanto-occipital membrane over the vertebral artery groove resulting in the formationof a foramen (Arcuate foramen) containing the vertebral artery and the posterior branch of the C-1 spinal nerve.This variation has been associated with vertebro-basilar insufficiency symptoms, various types of headaches,and acute hearing loss. The knowledge of this variant prevents complications during lateral mass screw fixation,posterior laminectomy and endovascular surgery.Aims: The aim of the present study was to analyze the percentage of incidence of arcuate foramen and to identifyits clinical significance.Materials and Methods: Hundred dried human atlas bones were used to study the presence of arcuate foramen inthe department of Anatomy at ESIC Medical College and PGIMSR, Rajajinagar, Bangalore.Results: We came across the presence of arcuate foramen in two out of hundred bones. In both the atlas bones,osseous bridge extending from posterior aspect of superior articular facet to the posterior arch of atlas on theleft side, forming arcuate foramen, posterior to foramen transversarium was observed.Conclusion: Arcuate foramen commonly called as Kimmerle’s anomaly where in a groove for vertebral artery isconverted into a foramen by ossification of the ligament. Awareness of osseous bridging is essential in performingcranio-cervical junction surgeries. It also serves as an anthropological data and also identifying the impact ofcomplete arcuate foramen on the signs and symptoms of vertebra-basilar insufficiency.

Análisis morfométrico del atlas por tomografía computada para la colocación de tornillos trans-masas laterales / Morphometric analysis of the atlas by computed tomography for the placement of lateral transmass screws

Objetivos: Realizar un análisis morfométrico del atlas por tomografía computada, determinando los valores promedio, medianos, y de variabilidad de dicha vértebra para la correcta colocación de tornillos trans-masas laterales. Introducción: Existe una significativa variabilidad interpersonal en los aspectos morfológicos del atlas, y dada su proximidad a estructuras neurovasculares (arteria vertebral, médula cervical, raíz de C2), hacen mandatario un exhaustivo planeamiento prequirúrgico para la elección de la técnica de artrodesis, tipo de tornillos a utilizar, y su trayectoria. Material y métodos: Se realizó un estudio de diseño de tipo exploratorio, descriptivo, observacional, retrospectivo, transversal. Se revisaron 99 tomografías computadas de la columna cervical. Se midieron parámetros morfométicos y angulaciones desde un "punto de entrada" en la masa lateral de C1, que fueron llamados A, B, C, D, E, F, G y H. Las mediciones de los parámetros a estudiar fueron realizadas con el programa RadiAnt DICOM Viewer (64-bit) y posteriormente volcadas a una ficha de registro de datos. Discusión: La distribución según género fue de 34 varones y 65 mujeres. Se encontró una diferencia estadísticamente significativa no solo en lo referente al género (masculino vs femenino; parámetros A, B, C, D, F, G, H p-valor < 0,05) de los parámetros medidos, sino también según lateralidad (derecha vs izquierda; parámetros C, E, F, G p-valor < 0,05). La investigación propone además la generación de una base de datos con información morfométrica del atlas. Conclusión: Existe una diferencia estadísticamente significativa en las propiedades morfológicas del atlas, tanto en lo relativo al género (masculino vs femenino), como en la lateralidad (derecha vs izquierda). Es por ello que el presente estudio enfatiza en la importancia de la realización prequirúrgica de una tomografía computada de la columna cervical superior para garantizar una efectiva y segura instrumentación a éste nivel, según el largo, ancho y trayectoria de los tornillos a utilizar.

Objectives: To morphometrically analyze the atlas, using computed tomography, thereby defining mean, median and variability values of C1 for the correct placement of lateral mass screws. Introduction: Significant interpersonal variability exists among the various morphological characteristics of the atlas. Given the structure's close relationship to neurovascular structures like the vertebral arteries, cervical spinal cord, and cervical roots, exhaustive pre-surgical planning becomes mandatory. Such planning assists in the choice of arthrodesis technique, and the dimensions and trajectory of screws. Material and Methods: A retrospective, observational study was performed, for which the computed tomography (CT) scans of 99 cervical spines were reviewed. Morpho-metric parameters and angulations were measured from an "entry point" in the lateral mass at C1; these parameters were alphabetically labeled from A through H. The RadiAnt DICOM Viewer (64-bit) program was used to measure all parameters of interest, the values of which then were entered into a data collection file.Discussion: By gender, there were 34 men and 65 women. A statistically-significant difference was found between the two genders for all parameters except parameter E (all p-values < 0,05), and between the two sides (right vs. left) for parameters C, E, F, and G. Our results argue for the creation of a general database containing morphometric information on the atlas. Conclusion: Statistically-significant differences exist between men and women, and from right to left, among the morphometrical features of the atlas. This underscores the need for careful preoperative surgical planning, including the use of CT scanning to estimate optimum screw lengths and trajectories.

The research progress of posterior atlantoaxial internal fixation techniques / 医学研究生学报

Atlantoaxial instability or dislocation is a common upper cervical disease which can lead to serious outcomes including sensory and motor deficit or even sudden death. Therefore, active surgical intervention is often recommended. The most popular surgical procedure for atlantoaxial instability is posterior bone graft and internal fixation. Posterior stabilization techniques mainly include wiring techniques, interlaminar clamp fixation, C1-C2 transarticular screw fixation (Magerl technique), screw-plate systems, and screw-rod systems. Each technique has its advantage and shortcoming. The screw-rod systems, along with various modifications, has become the most popular internal fixation technique for posterior atlantoaxial stabilization in clinic. This article reviews the evolution, characteristics and new advancement of some prevail posterior atlantoaxial fixation techniques in purpose of giving a reference for surgeons to have a better understanding of posterior fixation techniques and make a reasonable choice in clinical practice.

Open-door laminoplasty with lateral mass screw fusion in the treatment of multisegmental cervical spondylotic myelopathy with segmental instability / 中华老年医学杂志

Objective To investigate the effectiveness of open-door laminoplasty with lateral mass screw fusion in the treatment of multisegmental cervical spondylotic myelopathy (CSM)with segmental instability.Methods Forty-one patients with multisegmental cervical spondylotic myelopathy combined with instability underwent open-door laminoplasty with lateral mass screw fusion.The JOA(Japanese Orthopaedic Association)scoring system and Neck Disability Index(NDI) were applied to evaluate neurological function and axial neck/shoulder pain before and after surgery,respectively.In addition,the Ishihara method was used to measure the cervical curvature index(CCI),and spinal cord expansion was calculated with MRI.Results After 43 months of postoperative follow-up,there were significant differences in JOA scores[(7.12±0.91) vs.(14.73± 1.12),t =35.28,P＜0.001],areas of the dural sac at the level of maximum stenosis in MRI[(0.22±0.05)]cm2 vs.(0.62±0.09)cm2,t=14.15,P＜0.001],and NDI scores[(24.46±6.61) vs.(12.90±3.46),t=15.59,P ＜ 0.001],compared with those before treatment.However,there were no significant differences in pre-and post-operation CCI[(10.36±1.69) vs.(10.87±2.05),t=1.11,P＞0.05].Conclusions Open-door laminoplasty with lateral mass screw fusion can improve neurological function and maintain the normal cervical curvature.Therefore,it is effective in the treatment of multisegmental cervical spondylotic myelopathy with segmental instability.

Pedicle exposure technique for atlas screw fixation:a radiological research / 中国骨伤

<p><b>OBJECTIVE</b>To investigate the meaning of pedicle exposure technique for screw fixation on atlas with the vertebral groove height less than 4 mm by using reconstructive computed tomography.</p><p><b>METHODS</b>From April 2015 to June 2015, 84 pedicles of 51 patients with groove heights less than 4 mm were studied by digital reconstruction respectively. Parameters of atlas pedicle screw fixation were measured.</p><p><b>RESULTS</b>Among the 51 cases, the vertebral groove height was (3.28±0.51) mm. Lateral mass heights, lateral mass widths and the transition area heights between lateral mass and posterior arch were fit for 3.5 mm screw implanting. Ideal pedicle screw trajectory lengths from 0° to 15° (0°, 5°, 10°, 15°) were (27.36±1.81), (27.01±1.68), (27.07±1.75), (27.48±1.72) mm, exposed trajectory lengths from 0° to 15°(0°, 5°, 10°, 15°) were(23.44±1.79), (23.87±1.84), (24.58±1.89), (25.56±2.01) mm, trajectory length of lateral mass was (20.78±2.05) mm. The mean CT values on 5 sections through pedicle trajectory and lateral mass trajectory were (701.89±141.48) HU and (599.11±137.33) HU, respectively. There were no significant differences between ideal pedicle trajectory lengths from 0° to 15°(>0.05). Exposed trajectory lengths was significantly increased accompanying with medial angles increasing (<0.05), and was longer than trajectory lengths of lateral mass (<0.05). CT value of pedicle screws was higher than CT value of lateral mass screws significantly (<0.01).</p><p><b>CONCLUSIONS</b>Screws can be implanted in atlas with vertebral groove height less than 4 mm by using pedicle exposure technique. Few trajectory lengths will be sacrificed with favorable pull out strength due to adequate bone mass purchased.</p>

Assessment of C1 lateral mass screw trajectory and position by plain radiographs / 局解手术学杂志

Objective The aim of this study was to provide methods for predicting ideal trajectory and position of C1 lateral mass screw (C1 LMS)from plain radiographs.Methods A total of 40 consecutive subjects (with 79 screws)who had undergone C1 LMS placement were enrolled.To evaluate the C1 LMS position,the positions of screw head and tips on anteroposterior radiographs,screw length,and height on lateral radiograph were graded as 0°,Ⅰ°,and Ⅱ°,respectively.On the postoperative computed tomography images,the lateral mass (LM) perforation,screw-thread engagement percent(%),bicortical fixation,extruded screw length,and violation of adjacent joints were analyzed. Results Screws with tip located medial to LM(tip 0)showed LMperforation in all cases.Polyaxial head located within the LM(head 0)or crossing the lateral margin of the LM(head Ⅰ)showed no LMperforation.Screw-thread engagement percent was the highest with head Ⅰ-tip Ⅰ (medial half of LM)position (97.6%),followed by head 0-tip Ⅰ (90.5%)and head Ⅰ-tip Ⅱ (lateral half of LM)(86.4%). Screws longer than the posterior half of C1 anterior arch (AA)showed bicortical fixation in all cases with mean extruded screw length of 1.9 mm.Adjacent joint was not violated in 98%,with the screw height below half of C1 AA.Conclusion On an anteroposterior radiograph, a C1 LMS with the screw head located on the lateral margin of the LMand with the screw tip in the medial half of the LMresulted in the safest and longest trajectory.On lateral radiograph,a screw tip that is placed within the anterior-inferior quadrant of the C1 AA results in safe bicorti-cal fixation without injury to the adjacent structures.These plain radiographic findings may be helpful bothpostoperatively and intraoperatively for assessing the trajectory and length of the screw.

Atlas lateral mass screws combined with posterior Epistropheus pedicle screws for treatment of atlantoaxial joint instability / 局解手术学杂志

Objective To discuss the clinical effect and the notes of atlas lateral mass screws combined with posterior epistropheus ped-icle screws for the treatment of atlantoaxial joint instability. Methods In our hospital from January 2006 to January 2011,48 cases of atlan-toaxial joint instability accepted operation of the atlas lateral mass screws combined with epistropheus pedicle screws were analyzed. Results All patients with follow-up time 12~24 months,an average of 17 months,were achieved primary healing and atlanto-axial intervertebral osse-ous healing. Besides postoperative neck pillow area pain improved and nerve function get a degree of recovery,there was no inner fixed damage cases. Complications of operation include venous plexus hemorrhage was in 2 cases,cervical occipital pain and numbness increase in 3 cases,cere-brospinal fluid leak in 2 cases,vertebral artery extrusion occlusion after cerebral ischemic symptoms in 1 case. Conclusion Combination of atlas lateral mass screws and posterior epistropheus pedicle screws technique is one of the effective means of treatment of atlantoaxial joint instabili-ty and can obtain satisfactory clinical effect. Standard operation performance is the key to reduce or even eliminate surgical complications.

Comparison of Outcomes after Atlantoaxial Fusion with Transarticular Screws and Screw-Rod Constructs

OBJECTIVE: The purpose of this study was to compare the radiological and neurological outcomes between two atlantoaxial fusion method for atlantoaxial stabilization; C1 lateral mass-C2 pedicle screws (screw-rod constructs, SRC) versus C1-2 transarticular screws (TAS). METHODS: Forty-one patients in whom atlantoaxial instability was treated with atlantoaxial fixation by SRC group (27 patients, from March 2005 to May 2011) or TAS group (14 patients, from May 2000 to December 2005) were retrospectively reviewed. Numeric rating scale (NRS) for pain assessment, Oswestry disability index (ODI), and Frankel grade were also checked for neurological outcome. In radiologic outcome assessment, proper screw position and fusion rate were checked. Perioperative parameters such as blood loss during operation, operation time, and radiation exposure time were also reviewed. RESULTS: The improvement of NRS and ODI were not different between both groups significantly. Good to excellent response in Frankel grade is shown similarly in both groups. Proper screw position and fusion rate were also observed similarly between two groups. Total bleeding amount during operation is lesser in SRC group than TAS group, but not significantly (p=0.06). Operation time and X-ray exposure time were shorter in SRC group than in TAS group (all p<0.001). CONCLUSION: Both TAS and SRC could be selected as safe and effective treatment options for C1-2 instability. But the perioperative result, which is technical demanding and X-ray exposure might be expected better in SRC group compared to TAS group.

Combined Open Door Laminoplasty with Unilateral Screw Fixation for Unstable Multi-Level Cervical Stenosis : A Preliminary Report

OBJECTIVE: The authors reviewed their experiences of combined surgery (open door laminoplasty with unilateral screw fixation) for unstable multi-level cervical stenosis, to clarify the situation regarding the surgical approach most appropriate for the treatment of diffuse unstable multi-level cervical stenosis. METHODS: From January 2011 to January 2012, combined surgery was performed for unstable multi-level cervical stenosis by one surgeon at our institution. The subjects of this study were 6 men of mean age 53.7 years (range, 48-71) with a mean follow-up of 9.3 (range, 3-14) months. All imaging studies showed severe multi-level cervical stenosis with spinal cord signal change, and instability or kyphotic deformity. A retrospective review of clinical, radiological, and surgical data was conducted. RESULTS: Average laminoplasty level was 4.8 and the average screw fixation level was 5.0. Japanese Orthopedic Association score improved from an average of 5.2 to 11.2 points. According to Nurick's grades and Odom's criteria, symptom improvement was statistically significant. On the other hand, Cobb's angle changes were not significant. Average operation time was 5.86 hours with an average blood loss of 460 mL. No significant surgical complication was encountered. CONCLUSION: Despite the small cohort and the short follow-up duration, the present study demonstrates that laminoplasty with unilateral screw fixation is a safe and effective treatment for unstable multi-level cervical stenosis.

Anatomic Consideration of the C1 Laminar Arch for Lateral Mass Screw Fixation via C1 Lateral Lamina : A Landmark between the Lateral and Posterior Lamina of the C1

OBJECTIVE: To clarify the landmark for deciding the entry point for C1 lateral mass screws via the posterior arch by using 3-dimensional (3D) computed images. METHODS: Resnick insisted that the C1 posterior arch could be divided into pure posterior and lateral lamina (C1 pedicle). Authors studied where this transition point (TP) is located between the posterior lamina and the C1 pedicle and how it can be recognized. The 3D computed images of 86 cadaver C1s (M : F=45 : 41) were used in this study. RESULTS: The superior ridge of the C1 posterior arch had 2 types of orientation. One was in the vertical direction in the C1 posterior lamina and the other was in the horizontal direction in the C1 pedicle. The TP was located at the border between the 2 areas, the same site as the posterior end of the groove of the vertebral artery. On posterior-anterior projection, the posterior arch was sharpened abruptly at TP. We were unable to identify the TP in 6.4% of specimens due to complete or partial osseous bridges. A total of 93.8% of the TP were located between the most enlarged point of the spinal canal and the medial wall of the vertebral artery. CONCLUSION: The anatomic entry zone of C1 lateral laminar screws was clarified and identified based on the TP by using preoperative 3D computed images.

Two kinds of decompression and implant internal fixation for the treatment of cervical spinal stenosis:C5 nerve root palsy and stability / 中国组织工程研究

BACKGROUND:Some scholars suggest that the nerve root palsy after cervical spinal stenosis treated with decompression and implant internal fixation is related with the cervical stability and cervical lordosis, but there is controversial. OBJECTIVE:To explore the C 5 nerve root palsy and stability after cervical spinal stenosis treated with posterior laminectomy lateral mass fixation and single-door decompression laminoplasty. METHODS:Twenty-nine cervical spinal stenosis patients were selected and treated with posterior decompression and implant internal fixation. Posterior laminectomy lateral mass fixation for the treatment of cervical spinal stenosis:C3-6 lateral mass and C7 pedicel screw internal fixation was performed and caused rough surface on the facet joint;the unstable segment was confirmed according to the preoperative anteraposterior plain film and dynamic radiographs combined with MRI and CT images, and then the corresponding segments were treated with lateral mass internal fixation, single-door decompression laminoplasty and laminoplasty. RESULTS AND CONCLUSION:Al the 29 cervical spinal stenosis patients were fol owed-up for 8 months to 2.3 years. Among them, 14 cases were treated with posterior laminectomy lateral mass fixation, two cases had nerve root palsy in the early stage after implantation, three cases had incomplete paralysis after long-term symptom recurrence and treated with second surgery of scar remove and decompression;15 cases were treated with single-door decompression laminoplasty, and one case had C 5 never root palsy and shoulder abduction dysfunctionafter treatment, no preoperative symptom recurrence. The nerve root palsy wil restored in 6 weeks for shortest and 9 months for longest. As the limitation of the case number, it is not clear whether there were significant differences in the correlation between C 5 nerve root palsy and segmental stability, cervical lordosis, spinal decompression degree and the range for spinal cord shift, as wel as the nerve root palsy degree and the cervical spinal stenosis recurrence caused by forward scar between two treatment methods, so accumulation observation of the cases and clinical experience are needed.

Clinical Outcome of Modified Cervical Lateral Mass Screw Fixation Technique

OBJECTIVE: The purpose of this study was 1) to analyze clinically-executed cervical lateral mass screw fixation by the Kim's technique as suggested in the previous morphometric and cadaveric study and 2) to examine various complications and bicortical purchase that are important for b-one fusion. METHODS: A retrospective study was done on the charts, operative records, radiographs, and clinical follow up of thirty-nine patients. One hundred and seventy-eight lateral mass screws were analyzed. The spinal nerve injury, violation of the facet joint, vertebral artery injury, and the bicortical purchases were examined at each lateral mass. RESULTS: All thirty-nine patients received instrumentations with poly axial screws and rod systems, in which one hundred and seventy-eight screws in total. No vertebral artery injury or nerve root injury were observed. Sixteen facet joint violations were observed (9.0%). Bicortical purchases were achieved on one hundred and fifty-six (87.6%). Bone fusion was achieved in all patients. CONCLUSION: The advantages of the Kim's technique are that it is performed by using given anatomical structures and that the complication rate is as low as those of other known techniques. The Kim's technique can be performed easily and safely without fluoroscopic assistance for the treatment of many cervical diseases.

A Computed Tomography-Based Anatomic Comparison of Three Different Types of C7 Posterior Fixation Techniques : Pedicle, Intralaminar, and Lateral Mass Screws

OBJECTIVE: The intralaminar screw (ILS) fixation technique offers an alternative to pedicle screw (PS) and lateral mass screw (LMS) fixation in the C7 spine. Although cadaveric studies have described the anatomy of the pedicles, laminae, and lateral masses at C7, 3-dimensional computed tomography (CT) imaging is the modality of choice for pre-surgical planning. In this study, the goal was to determine the anatomical parameter and optimal screw trajectory for ILS placement at C7, and to compare this information to PS and LMS placement in the C7 spine as determined by CT evaluation. METHODS: A total of 120 patients (60 men and 60 women) with an average age of 51.7+/-13.6 years were selected by retrospective review of a trauma registry database over a 2-year period. Patients were included in the study if they were older than 15 years of age, had standardized axial bone-window CT imaging at C7, and had no evidence of spinal trauma. For each lamina and pedicle, width (outer cortical and inner cancellous), maximal screw length, and optimal screw trajectory were measured, and the maximal screw length of the lateral mass were measured using m-view 5.4 software. Statistical analysis was performed using Student's t-test. RESULTS: At C7, the maximal PS length was significantly greater than the ILS and LMS length (PS, 33.9+/-3.1 mm; ILS, 30.8+/-3.1 mm; LMS, 10.6+/-1.3; p<0.01). When the outer cortical and inner cancellous width was compared between the pedicle and lamina, the mean pedicle outer cortical width at C7 was wider than the lamina by an average of 0.6 mm (pedicle, 6.8+/-1.2 mm; lamina, 6.2+/-1.2 mm; p<0.01). At C7, 95.8% of the laminae measured accepted a 4.0-mm screw with a 1.0 mm of clearance, compared with 99.2% of pedicle. Of the laminae measured, 99.2% accepted a 3.5-mm screw with a 1.0 mm clearance, compared with 100% of the pedicle. When the outer cortical and inner cancellous height was compared between pedicle and lamina, the mean lamina outer cortical height at C7 was wider than the pedicle by an average of 9.9 mm (lamina, 18.6+/-2.0 mm; pedicle, 8.7+/-1.3 mm; p<0.01). The ideal screw trajectory at C7 was also measured (47.8+/-4.8degrees for ILS and 35.1+/-8.1degrees for PS). CONCLUSION: Although pedicle screw fixation is the most ideal instrumentation method for C7 fixation with respect to length and cortical diameter, anatomical aspect of C7 lamina is affordable to place screw. Therefore, the C7 intralaminar screw could be an alternative fixation technique with few anatomic limitations in the cases when C7 pedicle screw fixation is not favorable. However, anatomical variations in the length and width must be considered when placing an intralaminar or pedicle screw at C7.

Comparative Analysis of Three Different Cervical Lateral Mass Screw Fixation Techniques by Complications and Bicortical Purchase : Cadaveric Study

OBJECTIVE: The purpose of this study is to compare the incidence of possible complications of cervical lateral screw fixation and the achievements of bicortical purchase using the Roy-Camille, Magerl and the modified methods. METHODS: Six fresh-frozen cervical spine segments were harvested. The Roy-Camille technique was applied to C3 and C4, and the Magerl technique was applied to C5, C6, and C7 of one side of each cadaver. The modified technique was applied to the other side of each cadaver. The nerve root injury, violation of the facet joint, vertebral artery injury, and the bicortication were examined at each screwing level. RESULTS: No vertebral artery injury was observed in any of the three methods. One nerve root injury was observed in each cervical spine segment using the Roy-Camille method (8.3%), the Magerl method (5.6%), and the modified method (3.3%). Facet joint injuries were observed in two cervical spinal segments using the Roy-Camille method (16.7%) and three with the Magerl method (16.7%), while five facet joint violations occurred when using the modified method (16.7%). Bicortical purchases were achieved on ten cervical spinal segments with the Roy-Camille method (83.3%) and Magerl method (55.6%), while twenty bicortical purchases were achieved in the modified method (66.7%). CONCLUSION: The advantages of the modified method are that it is performed by using given anatomical structures and that the complication rate is as low as those of other known methods. This modified method can be performed easily and safely without fluoroscopic assistance for the treatment of many cervical diseases.

The Surgical Treatment of the Cervical Myelopathy with Laminectomy and Posterior Fusion by using Lateral Mass Screw Fixation / 대한정형외과학회잡지

PURPOSE: This prospective study was designed to investigate the outcomes of laminectomy and fusion with using lateral mass screw (LMS) fixation for the treatment of cervical myeolpathy. MATERIALS AND METHODS: We studied a series of 26 consecutive patients with cervical myelopathy and who were planned to undergo laminectomy and fusion with using LMS fixation. MRI was done to investigate the high signal intensity lesion (HSIL) in the cord on the T2 weighted sagittal images. The JOA score, the grip and release test, the finger escape sign, and Hoffman's sign were checked. We analyzed the clinical outcomes depending on the high signal intensity lesion in the cord, the preoperative kyphosis, and the preoperative instability. RESULTS: The indications for lateral mass screw fixation was kyphotic deformity, segmental instability or ossification of the ligament flavum (OLF). Patients with HSIL on the T2-weighted sagittal MRI was found in 17 patients. The JOA score, the grip and release test, and the finger escape sign were significantly improved after the operation and at the 2 year follow up. The patients with HSIL on the T2-weighted sagittal MRI or segmental instability had a significantly lower preoperative JOA score and a poor postoperative recovery as assessed by the JOA score. CONCLUSION: Laminectomy and fusion using lateral mass screw fixation for the surgical treatment of cervical myelopathy, which is associated with kyphotic deformity, instability or OLF, is considered a safe and effective treatment option to prevent postoperative kyphosis.

Troublesome Occipital Neuralgia Developed by C1-C2 Harms Construct

Recently, Harms and Melcher modified Goel's approach, the C1 lateral mass and C2 pedicle screw fixation, and the new technique is currently in favor among neurosurgeons. Comparing to the advantages of Harms construct, the disadvantages were not extensively investigated. We experienced a patient with severe occipital pain developed after the C1 lateral mass screw placement for the traumatic atlantoaxial instability. We reviewed literatures about Harms construct with focus on the occipital neuralgia as a postoperative complication and suggest here technical tips to avoid the troublesome pain.

Comparative Analysis of Cervical Lateral Mass Screw Insertion among Three Techniques in the Korean Population by Quantitative Measurements with Reformatted 2D CT Scan Images : Clinical Research

OBJECTIVE: Our purpose of this study is to compare insertion angles and screw lengths from Roy-Camille, Magerl, and our designed method for cervical lateral mass screw fixation in the Korean population by quantitative measurement of reformatted two dimensional (2D) computed tomography (CT) images. METHODS: We selected thirty Korean patients who were evaluated with thin section CT scans and reconstruction program to obtain reformatted 2D-CT images of the transversal plane passing the cranio-caudal angle using three different techniques. We measured the minimum angle to avoid vertebral artery (VA) injury, the ideal angle and depth for bicortical screwing of cervical lateral mass. Morphometric measurements of the lateral masses from C3-C7 were also taken. RESULTS: In all three techniques, the mean safety angles from the VA were less than 8 degrees and the necessary depth of the screw was about 14 mm for safety to the VA and for the bicortical purchase. In our designed technique, the mean beta angles of each level from C3 to C7 were 29.0, 29.8, 29.5, 26.3, and 23.9 degrees, respectively. CONCLUSION: Results of this study and data from the literature indicate that differences may exist between the Korean and Western people in the length and angle for ideal lateral mass screw fixation. In addition, our technique needs further cadaveric and clinical study for safety and efficacy for being performed as alternative method for cervical lateral mass fixation.

Prevalence and Morphologic Features of Ponticulus Posticus in Koreans: Analysis of 312 Radiographs and 225 Three-dimensional CT Scans

STUDY DESIGN: A retrospective review of three-dimensional CT scan images and radiographs. PURPOSE: To investigate the prevalence and morphologic features of ponticulus posticus in Koreans. OVERVIEW OF LITERATURE: There has been little reported on the prevalence or morphologic characteristics of ponticulus posticus in Asians, predisposing them to vertebral artery injury during screw placement in the lateral mass of the atlas. METHODS: The presence and types of ponticulus posticus were investigated on 225 consecutive cervical three-dimensional CT scans and 312 consecutive digital lateral cephalometric head radiographs. RESULTS: Various spectra of ponticulus posticus were found in 26% of the CT scans and 14% of the radiographs. CONCLUSIONS: Ponticulus posticus is a relatively common anomaly in Koreans. Therefore, the presence of this anomaly should be carefully examined for on radiographs before lateral mass screw placement. If ponticulus posticus is suspected or confirmed on radiographs, three-dimensional CT scanning should be considered before placement of lateral mass screws into the posterior arch, especially given its wide variation of size and shape.