Abstract
BACKGROUND: The appearances of spiral computer tomograph (CT) and three-dimensional image processing are of very importance for fully evaluating preoperative pathological changes, which represent various cervical spondylotic myelopathy (CSM) in clinic, and choosing proper clinical therapeutic occasion and methods.

OBJECTIVE: To analyze the effects of imageological image and technical advantages of three-dimensional spiral CT on the preoperative evaluation and surgical plan of CSM.

DESIGN: Retrospective analysis, controlled observation.

SETTING: Nanjing First Hospital Affiliated to Nanjing Medical University.

PARTICIPANTS: Altogether 268 patients with CSM admitted to Nanjing First Hospital from January 2002 to January 2005 were involved in this experiment. The involved patients were randomly assigned into preoperative evaluation group (n =146) and control group (n =122). The baseline materials of two groups were comparable.

METHODS: Preoperative evaluation group: ① CT scan and three-dimensional reconstruction: Helical scanning was conducted at transverse plane with TOSHIBA-HiSpeed/I screw machine. After scanning, reconstruction was performed finally, three-dimensional reconstruction was conducted on computer workstation （Radwork5.1）. Correlative data were measured and analyzed with image analysis software (ADW3.1). ② Design of three-dimensional CT-assisted operation plan: Cervical vertebral osseous anatomic landmark and the anatomic relationship of its adjacent structure were revealed stereoscopically. Individual orthopaedic location marker could be provided. Preoperative routine CT examination was performed in the control group with conventional operation method.

MAIN OUTCOME MEASURES: ① The hyperostosis of vertebral body, hamular process joint and small articular process were observed. ②The degree and type of intervertebral disc protrusion were observed. ③The changes of hyperostosis before and behind the vertebral canal. Spinal decompression was observed by CT virtual endoscopy (CT-VE).

RESULTS: All the 268 patients participated in the result analysis. ① In the preoperative evaluation group, 129 patients were found with intervertebral disc protrusion, 109 patients with vertebral posterior marginal hyperostosis, 61 patients with hypertrophic ligamentum flavum and corrugation, 27 patients with posterior longitudinal ligament calcification, 31 patients with hyperostosis at small articular process, 29 patients with vertebral plate thickening and 18 patients with vertebral olisthy. The visible anatomical structures were in accord with clinical manifestations and imageological structures. Death, laryngeal nerve injury, bone graft displacement, infection and other complications were not found in all the patients. In the postoperative 6th month, X-ray image showed that all the patients had good bone graft fusion, and no titanic plate or bolt loosening or fragmentation was found. The excellent and good rate evaluated by Odom was 95.9%. ② In the control group, postoperative X-ray image and CT showed that vertebral canal decompression of 24 patients was not fully, and the positions of titanic plate or bolt of 17 patients were not satisfying. The excellent and good rate evaluated by Odom (84.4%) in the control group was lower than that in the preoperative evaluation group (P < 0.05).

CONCLUSION: Preoperative observation of cervical vertebral individual three-dimensional CT is helpful to exactly and generally evaluate cervical spondylotic myelopathy and assistantly make operative plan, whick makes intraoperative manipulation more exactive, safer and easier to be controlled.

INTRODUCTION

Cervical spondylotic myelopathy (CSM) is spinal dysfunction of different extents induced by cataplasia of cervical vertebrae structure-caused compression to spinal cord and/or vessels which dominate spinal cord. Its pathogenesis is very complicated and its clinical manifestations are various. It is of very significance to fully evaluate preoperative pathological changes for choosing clinical therapeutic occasions and methods. The appearances of spiral computer tomograph (CT) and computer three-dimensional image processing have provided a set of bran-new methods for the evaluation of cervical syndrome (CS). In this study, we investigated the preoperative guide value of CT in treating CSM.

SUBJECTS AND METHODS

Subjects
Totally 268 patients with CSM admitted to Department of Orthopaedics, First Hospital Affiliated to Nanjing Medical University from January 2002 to January 2005 were involved in this study.
Body examination showed the lower cervical cord compression in all the patients. Spinal cord tumor, cervical spine fracture, tubercle and other pathological changes were excluded. All the patients agreed to receive grouping operation treatment. Altogether 146 patients, 84 males and 62 females, aged 56.4 years ranging from 34 to 72 years, were randomly chosen as preoperative evaluation group. They had the disease course of 5.4 years ranging from 6 months to 12 years.
According to grading of CSM function [1], 25, 38 and 83 patients were found with degree 2, 3 and 4 limb disability, respectively. Preoperatively, routine X-ray image was photographed and three-dimensional CT examination was performed. MRI examination was performed in 66 patients. The other 122 patients, 77 males and 45 females, aged 58.3 years on average, with disease course of mean 5.6 years, were involved in the control group. Preoperatively, X-ray image was photographed and routine CT examination was performed. MRI examination was performed in 87 patients. There was no significant difference in baseline material between two groups (P > 0.05).

Methods
CT scan and three-dimensional reconstruction methods
Patients were asked to be in supine position. The long-axis of body was in parallel with machine tool. The angle between base of mandible and anterior median line was regulated at 120°. Helical scanning was conducted at transverse plane with TOSHIBA-HiSpeed/I screw machine. Scanning range was from the superior part of T1 to C1. The canal angle was set as 0 degree, layer thinness as 3 mm, electric current as 220 mA, voltage as 120 kV and Pitch as 1. After scanning, reconstruction was performed based on the standard of 1-mm spacing and 12 to 15 FOV, finally, three-dimensional reconstruction was conducted on computer workstation （Radwork5.1）. The lower limit value of bone reconstruction was 300 Hu and the upper limit was unrestricted. Correlative data were measured and analyzed with image analysis software (ADW3.1). CT spinal canal myelography was performed in 28 patients. Omnipaque of 20 mL was injected into spinal canal, and CT examination was performed 6 hours after the patients were asked to lie.
Three-dimensional reconstruction: It was performed in sequence of volume reconstruction, maximum intensity projection, contour reconstruction and so on.

Observation content and methods
Hyperostosis of cervical vertebra: Cervical vertebral three-dimensional image was rotated for observing the hyperostosis of vertebral body, hamular process joint and small articular process. Protrusion of intervertebral disc: The degree and type of intervertebral disk protrusion were observed from the cervical vertebral cutting image at transverse plane and sagittal plane. Display in spinal canal: Vertebral plate was removed by computer cutting technique for observing the changes of hyperostosis before and behind the vertebral canal. Spinal decompression was observed by CT virtual endoscopy (CT-VE).

Three-dimensional CT used for the evaluation of CS
General three-dimensional manifestations of CS: ①Vertebral hyperostosis was found in 68 patients (46.6%).② Hyperostosis of hamular process joint: hyperostosis was found in 270 of 430 humular process (62.8%). ③ Hyperostosis of small articular process: Hyperostosis was found in 29 of 180 small articular processes (16.1%). ④ Physiological curvature changes of cervical vertebrae was found in 64 patients (43.8%).
The three-dimensional CT manifestations of CSM involved posterior cervical vertebral hyperostosis (109, 74.7%), posterior longitudinal ligament calcification (27, 18.5%), intervertebral disc protrusion (129, 88.3%), vertebral plate thickening (29, 19.9%), hyperostosis of small articular process (31, 21.2%), hypertrophic ligamentum flavum (61, 41.8%), vertebral olisthy (18, 12.3%) and so on.

Design of three-dimensional CT-assisted operation plan
Computer cutting technique: ①Surgical removal of coronal plane of vertebral plate: anterior and posterior spinal canal hyperotosis was observed, osteophyte range was measured and operative pathway and decompression range were determined. ②Cutting at sagittal plane: It could display sagittal spinal cord and the degree of decompression of anterior and posterior dura mater capsule, determine whether osteophyte, intervertebral disc or ligament hypertrophy calcification cause decompression or not, measure the minimal spinal cord and spinal canal sagittal diameter as well as Pavlov ratio, and finally evaluate the stenosis degree of spinal canal. ③Three-dimensional reconstruction of axial plane: transverse foramen, intervertebral pore, vertebral canal, section of arachnoid cavity, profile of nerve root canal as well as the length and angle of pedicle of vertebral arch were displayed. The safe range of anterior vertebral resection and the safe angle and entering point of posterior pedicle of vertebral arch bolt and side block bolt were set down.

Contour reconstruction
The diameter of pedicle of vertebral arch and the running of nerve root were displayed and the diameter of bolt was determined.

Therapeutic methods
In the preoperative evaluation group, individual operation scheme was designed according to cervical vertebral three-dimensional model showed by CT. Posterior approach was conducted in 39 patients, single open-door laminoplasty in 11 patients, surgical removal of vertebra in 28 patients, surgical removal of vertebra in 28 patients, double open-door laminoplasty in 9 patients, unilateral multiple articular process resection in 5 patients. In the 82 patients, 21 patients subjected to uncovertebral joint resection for nerve canal decompression, 16 subjected to Café fusion and so on. Combined anterior and posterior approach and decompression for bone fusion by internal fixation was conducted in 25 patients. Jaw bone and cervical vertebrae were fixed for 6 to 12 weeks with gesso. In the 122 patients of control group, anterior approach was conducted in 94 patients by total resection of anterior cervical vertebral body followed by decompression, PCB or Orion steel plate fixation. Posterior approach was conducted in 28 patients, single open-door laminoplasty in 6 patients, surgical removal of vertebral plate in 22 patients.

RESULTS

Quantitative analysis of the participants
Altogether 268 patients participated in the result analysis.

Therapeutic results of preoperative evaluation group
The three-dimensional CT imaging of 146 patients could well explain clinical manifestations. The visible anatomical structures in the operation were in accord with clinical manifestations and imageological findings. In the postoperative 6th month, X-ray image showed that bone graft of all the patients fused well without the titanium plate or bolt loosening or fragmentation. In the Odom clinical therapeutic effect evaluation, 104 patients were excellent, 36 good, so the excellent and good rate was 95.9%.

Therapeutic results of control group
Among 122 patients, postoperative X-ray image and CT showed that 24 patients subjected to insufficient vertebral canal decompression, 17 patients did not satisfy the position of titanium plate or bolt. In the Odom clinical therapeutic effect evaluation, 71 patients were excellent, 32 good and 19 fair, so the excellent and good rate was 84.4%, which was significantly lower than that of preoperative evaluation group (P < 0.05).

Adverse events and side effect
No death was found in all the patients and no laryngeal nerve injury; bone graft shift, infection and other complications were found, either.

DISCUSSION

Previously, it was not thought that CT could display spinal decompression and degeneration. Canal visualization can isochronously show osseous and membrane vertebral canal, directly reflect dura mater capsule, cervical cord compression as well as degeneration and necrosis and other pathological changes of cervical cord. Among 28 patients who underwent CT canal visualization, 19 subjected to MRI examination. High signal of T1WI was found in 7 patients and the corresponding CT also presented high-density shadow. Its mechanism may be due to the penetration of constrast medium into cervical cord-caused degeneration, necrosis and cystic change.
CT-VE can be used to dynamically and directly observe spinal decompression and display the non-smoothness of vertebral canal wall, stenosis and adhesion of arachnoid cavity, intervertebral disc rotrusion and the symptom of osteophyte decompressing cervical cord. The three-dimensional CT imageological manifestations of patients in this study can well explain clinical manifestations, so it is showed that three-dimensional CT can give exact and general evaluation on CSM.
Clinical studies found that the therapeutic effect of operation and disease course of CSM were closely related with the damage degree of spinal cord. The longer the disease course is, the severer the damage of spinal cord and the poorer the therapeutic effect [2-6]. Operation treatment as early as possible is one important factors for obtaining the best therapeutic effect in treating CSM. Therefore, it is very important to make individual diagnosis and operation scheme. Among the patients whose clinical and imageological manifestations are very complicated, exact preoperative evaluation of disease condition for preparing optimized individual operation scheme is more important and difficult than operation itself [7-9], which is also the study hotspot of spinal surgery at present.
Preoperative observation of cervical vertebral individual three-dimensional CT image model can know the variation of important osseous anatomical marker. Observation of pathological changes from multiple planes can know the spatial adjacent relationship of pathological changes for determining operative approach. Determining the angle and direction of screw-entering in the pedicle of vertebral arch and lateral mass, and labeling the point of screw entering and decompression range can quantize the operation, thus, the manipulation of operation is easier to control exactly and safely.
The visible anatomical structures in this study are in accord with clinical manifestations and imageological findings. No death was found in all the patients and no laryngeal nerve injury; bone graft shift, infection and other complications were found, either. In the postoperative 6th month, X-ray image showed that bone graft of all the patients fused well without the titanium plate or bolt loosening or fragmentation and the therapeutic effect is superior to that in the control group. It demonstrates that three-dimensional CT is very important in assisting cervical vertebral operation plan. In addition, following operation for treating CS, spiral CT three-dimensional reconstruction can know whether or not the diseased region of CS is fully decompressed, and it can be used as the standard to evaluate bone graft fusion, bone block loosening and defluvium, spinal column stabilization.

REFERENCES

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三维CT影像学图像及技术优势对脊髓型颈椎病术前评估及辅助制定手术计划的价值

侯明夫，徐 杰，王钢锐，蒋纯志
南京医科大学附属南京第一医院骨科，江苏省南京市 210006
侯明夫，男，1957年生，山东省文登市人，汉族，1983年解放军第二军医大学毕业，副主任医师，主要从事脊柱外科研究。
摘要
背景：螺旋CT和计算机三维图像技术的出现对评估脊髓型颈椎病术前病理改变，以及选择合适的治疗时机和方法均有重要意义。
目的：分析三维CT影像学图像及技术优势在脊髓型颈椎病术前评估及辅助手术计划制定中的作用。
设计：回顾性分析，对照观察。
单位：南京医科大学附属南京第一医院。
对象：南京第一医院2002－01/2005－01收治268例脊髓型颈椎病患者，分为术前评估组146例和对照组122例，两组基线资料有可比性。
方法：术前评估组：①CT扫描及三维重建：采用TOSHIBA-HiSpeed/I螺旋机，进行横断位螺旋扫描，扫描后进行标准重建，最后在计算机工作站（Radwork5.1）进行三维重建，相关数据可运用图像分析软件（ADW3.1）进行测量分析。②三维CT辅助手术计划的设计： 立体多角度地展现颈椎骨性解剖标志及其相邻结构的解剖关系，提供手术个体化骨性定位标志。对照组：术前常规CT检查，传统的手术方法。
主要观察指标：①观察椎体、钩突关节和小关节突骨质增生。②观察椎间盘突出的程度及类型。③观察椎管前后的骨质增生等改变，通过CT仿真椎管镜观察脊髓受压情况。
结果： 268例进入结果分析。①术前评估组发现椎间盘突出129例、椎体后部缘骨质增生109例、黄韧带肥厚褶起皱61例、后纵韧带钙化27例、小关节突骨质增生31例、椎板增厚29例、椎体滑 脱18例；术中所能见到的解剖结构同临床表现与影像发现均相符合；所有患者术中无死亡,无喉返神经损伤、移植骨块移位、感染等并发症。术后6个月复查X射线片示全部病例植骨融合良好,无钛板或螺钉松动或断裂现象。Odom临床疗效评定优良率95.9%。②对照组术后X射线片和CT示24例椎管减压不充分，17例钛板或螺钉位置不满意；Odom临床疗效评定优良率84.4%,低于术前评估组(P < 0.05)。
结论：术前进行颈椎个性化三维CT检查能对脊髓型颈椎病作出准确、全面的评估，并能辅助制定手术计划，使术中操作更精确安全。
关键词：颈椎病；三维CT；手术
中图分类号:R319.1 文献标识码:A 文章编号:1673-8225(2007)13-02578-03
侯明夫，徐杰，王钢锐，蒋纯志．三维CT影像学图像及技术优势对脊髓型颈椎病术前评估及辅助制定手术计划的价值[J].中国组织工程研究与临床康复，2007，11(13):2578-2580
[www.zglckf.com/zglckf/ejournal/upfiles/07-13/13k-2578(ps).pdf]
(Edited by Xiang Z/Song LP/Wang L)