Upper thoracic myelopathy caused by delayed neck extensor weakness in myotonic dystrophy

Myotonic dystrophy is the most common autosomal dominant myopathy in adults. Our patient, a 41 year-old female suffering from myotonic muscular dystrophy, developed upper thoracic myelopathy due to hypertrophy of the ligamentum flavum and the posterior longitudinal ligament. She had a typical hatchet face and ptosis with "head hanging forward" appearance caused by neck weakness. Motor weakness, sensory changes and severe pain below T4 level, along with urinary incontinence began 3 months ago. Genetic and electrodiagnostic studies revealed myotonic dystrophy type 1. Magnetic resonance imaging of the spine showed loss of cervical lordosis and spinal cord compression due to hypertrophied ligamentum flavum and posterior longitudinal ligament at T1 to T3 level. We concluded that her upper thoracic myelopathy was likely related to the thickness of the ligamentum flavum and posterior longitudinal ligament due to repetitive mechanical stress on her neck caused by neck muscle weakness with myotonic dystrophy.     

Numerical investigation of the relative effect of disc bulging and ligamentum flavum hypertrophy on the mechanism of central cord syndrome

BackgroundThe pathogenesis of the central cord syndrome is still unclear. While there is a consensus on hyperextension as the main traumatic mechanism leading to this condition, there is yet to be consensus in studies regarding the pathological features of the spine (intervertebral disc bulging or ligamentum flavum hypertrophy) that could contribute to clinical manifestations.MethodsA comprehensive finite element model of the cervical spine segment and spinal cord was used to simulate high-speed hyperextension. Four stenotic cases were modelled to study the effect of ligamentum flavum hypertrophy and intervertebral disc bulging on the von Mises stress and strain.FindingsDuring hyperextension, the downward displacement of the ligamentum flavum and a reduction of the spinal canal diameter (up to 17%) led to a dynamic compression of the cord. Ligamentum flavum hypertrophy was associated with stress and strain (peak of 0.011 Mpa and 0.24, respectively) in the lateral corticospinal tracts, which is consistent with the histologic pattern of the central cord syndrome. Linear intervertebral disc bulging alone led to a higher stress in the anterior and posterior funiculi (peak 0.029 Mpa). Combined with hypertrophic ligamentum flavum, it further increased the stress and strain in the corticospinal tracts and in the posterior horn (peak of 0.023 Mpa and 0.35, respectively).InterpretationThe stenotic typology and geometry greatly influence stress and strain distribution resulting from hyperextension. Ligamentum flavum hypertrophy is a main feature leading to central cord syndrome.     

X线检查在黄韧带骨化症诊断中的价值

目的:探讨X线检查在诊断黄韧带骨化症中的作用.方法:对56例黄韧带骨化症的X线表现进行回顾性分析.结果:黄韧带骨化症X线特征为多节段受累,胸腰段多见,多为边疆性,多合并后纵韧带骨化,结论:X线检查对于防止漏,误诊和定位在诊断黄韧带骨化症中有其特殊的地位.     

严重慢性机械压迫性脊髓损伤的手术疗效分析

目的:评价严重慢性机械压迫性脊髓损伤的手术疗效。方法:回顾性分析手术治疗的28例严重慢性脊髓损伤患者的临床资料,根据术前及术后随访24月时JOA评分的变化进行疗效评价。结果:脊髓型颈椎病7例,颈椎后纵韧带钙化6例,寰枢椎脱位1例,胸椎黄韧带钙化7例,胸椎黄韧带钙化并后纵韧带钙化4例,胸腰椎创伤后后凸畸形3例;均根据损伤类型进行相应手术治疗;随访结果显示术后24月时患者的JOA评分较术前均增加(P0.05),疗效评价"差"2例,"一般"5例,"好"21例。结论:对于大部分严重慢性机械压迫性脊髓损伤患者手术治疗可取得良好疗效,手术方式是影响部分患者疗效的重要因素。     

A comprehensive finite element model of surgical treatment for cervical myelopathy

BackgroundCervical myelopathy is a common and debilitating chronic spinal cord dysfunction. Treatment includes anterior and/or posterior surgical intervention to decompress the spinal cord and stabilize the spine, but no consensus has been made as to the preferable surgical intervention. The objective of this study was to develop an finite element model of the healthy and myelopathic C2-T1 cervical spine and common anterior and posterior decompression techniques to determine how spinal cord stress and strain is altered in healthy and diseased states.MethodsA finite element model of the C2-T1 cervical spine, spinal cord, pia, dura, cerebral spinal fluid, and neural ligaments was developed and validated against in vivo human displacement data. To model cervical myelopathy, disc herniation and osteophytes were created at the C4-C6 levels. Three common surgical interventions were then incorporated at these levels.FindingsThe finite element model accurately predicted healthy and myelopathic spinal cord displacement compared to motions observed in vivo. Spinal cord strain increased during extension in the cervical myelopathy finite element model. All surgical techniques affected spinal cord stress and strain. Specifically, adjacent levels had increased stress and strain, especially in the anterior cervical discectomy and fusion case.InterpretationsThis model is the first biomechanically validated, finite element model of the healthy and myelopathic C2-T1 cervical spine and spinal cord which predicts spinal cord displacement, stress, and strain during physiologic motion. Our findings show surgical intervention can cause increased strain in the adjacent levels of the spinal cord which is particularly worse following anterior cervical discectomy and fusion.     

胸椎黄韧带骨化症的手术治疗

目的 :探讨胸椎黄韧带骨化症的手术治疗方法与技巧 ,以提高胸椎黄韧带骨化症的诊疗水平。方法 :胸椎黄韧带骨化症 2 1例 ,均行胸椎后路节段全椎板切除椎管扩大脊髓减压术。结果 :本组术后平均随访 1 5a ,优 16例 ( 76 2 %) ,良 5例 ( 2 3 8%)。疗效满意。结论 :早期诊断并尽早手术是治疗胸椎黄韧带骨化症的关键。     

长节段颈椎后纵韧带骨化症修复：后路椎板切除植骨内固定与前路椎体次全切除减压的比较

背景：后纵韧带骨化症前路手术是通过直接减压,取出压迫的骨赘、骨化的后纵韧带,前路间盘从而达到彻底减压,通过置入钢板、钛网,产生前路支撑作用,有利于恢复颈椎生理曲度。但对于范围超过3个节段的患者,实施前路无法彻底切除骨化物,且减压难以维持颈椎曲度和稳定性,实施后路手术更为合适。目的：对比分析后路椎板切除植骨内固定与前路椎体次全切除减压修复长节段颈椎后纵韧带骨化症的效果。方法：从秦皇岛市第三医院2011年9月至2013年9月收治的长节段颈椎后纵韧带骨化症患者中选择34例进行观察,分别给予前路椎体次全切除减压（对照组）和后路椎板切除植骨内固定（观察组）治疗。所有患者治疗前均常规进行颈椎X射线、CT及MR检查,治疗后7 d进行复查。检查椎管矢状径、颈椎曲度、椎管狭窄率、骨化物分型、骨化物范围（节段）脊髓压迫率。并对患者进行日本骨科学会（JOA）评分,并计算其神经功能改善情况。结果与结论：经影像学检查,两组患者的椎管矢状径和治疗前颈椎曲度等指标比较差异均无显著性意义（P均〉0.05）,但治疗后两组颈椎曲度和脊髓压迫率差异均有显著性意义（P均〈0.05）,观察组优于对照组。治疗前两组患者的JOA评分差异无显著性意义（P〉0.05）,但治疗后两组的JOA评分、平均改善率以及优良率差异均有显著性意义（P均〈0.05）,观察组优于对照组。在治疗后并发症发生率方面,两组差异无显著性意义（P〉0.05）。提示与前路椎体次全切除减压治疗相比,采用后路椎板切除植骨内固定修复长节段颈椎后纵韧带骨化症可以获得良好的效果。     

颈椎间盘并椎体后纵韧带部分切除治疗颈脊髓压迫症

目的探讨应用颈椎间盘、椎体及后纵韧带部分切除,植骨及带锁钢板内固定在治疗伴有后纵韧带压迫颈髓神经疾病中的应用. 方法单个椎间隙者13例手术采用前路间盘及相应部位后纵韧带部分切除,其余手术采用前路椎体大部分切除及相应部位后纵韧带部分切除,18例采用自体髂骨植骨融合,38例采用钛网笼内填充减压椎体之松质骨植骨,最后均予带锁钢板内固定. 结果术后复查MRI:见颈脊髓神经压迫去除满意.56例平均随访18个月,植骨全部于术后3～4个月骨性愈合.术后已恢复椎间隙高度没有发现再丢失现象,颈椎生理弧度恢复良好. 结论颈椎间盘及后纵韧带大部分切除术,颈椎及后纵韧带大部分切除术适用于部分伴有后纵韧带颈脊髓神经和神经根压迫症患者,有利于彻底解除神经压迫.     

12例急性脊髓刀扎伤的MRI表现

目的 研究急性脊髓刀扎伤的磁共振成像（MRI）特征。方法 对12例急性脊髓刀扎伤患者的MRI进行回顾性分析。结果 12例均可见入路信号,椎管外一椎管内的刀迹金属伪迹影;此外,亦可见脊髓内的刀迹金属伪迹影、脊髓损伤信号、水肿信号、脊髓出血信号、硬膜外、下血肿出血信号。硬膜下、外血肿的鉴别可通过硬膜在血肿与脊髓间的关系来鉴别;矢状T1、T2加权相可以清晰地显示黄韧带、后纵带及硬膜的损伤或断裂。结论 MRI可准确诊断脊髓刀扎伤的部位,髓内、髓外及韧带、硬膜的损伤,尤其是矢状T2W相可清晰、准确地显示刀扎入的路径。     

Thoracic myelopathy in Japan: epidemiological retrospective study in Miyagi Prefecture during 15 years

Thoracic myelopathy is defined as spinal cord compression in the thoracic region, leading to sensory and motor dysfunctions in the trunk and lower extremities, and can be caused by various degenerative processes of the spine. Thoracic myelopathy is rare, and there are many unsolved problems including its epidemiological and clinical features. We have established a registration system of spinal surgeries, which covered almost all surgeries in Miyagi Prefecture, and enrolled the data of 265 patients with thoracic myelopathy from 1988 to 2002. The annual rate of surgery gradually increased and averaged 0.9 per 100,000 inhabitants, which was less than 1/10 of that for cervical myelopathy. About 20 patients with thoracic myelopathy are operated on in Miyagi Prefecture each year. It frequently develops in middle-aged males. About half of the cases were caused by ossification of the ligamentum flavum, followed by ossification of the posterior longitudinal ligament, intervertebral disc herniation and posterior spur. Patients usually noticed numbness or pain in the legs and the preoperative duration was long, averaging 2 years. Its symptomatic similarities to lumbar disorders might cause difficulty in making a correct diagnosis. Since thoracic myelopathy can markedly restrict the activities of daily life, even general physicians should recognize this entity.     

增加前路cage融合对颈椎曲度、稳定性及轴性症状的影响

背景：对于严重的颈椎间盘突出、后纵韧带钙化、黄韧带增生,实施前后联合入路不仅可以达到彻底减压的目的,同时植入cage及前路钢板矫形固定可部分恢复椎体间隙及颈椎生理曲度。 目的：比较颈椎病颈后路单开门椎管扩大成形及增加前路cage融合内固定对治疗后患者颈椎曲度、稳定性及轴性症状发生的影响。 方法：回顾性分析颈椎病外科治疗50例患者的临床资料。其中行一期前后联合入路脊髓减压（前路 cage＋钢板融合固定）22例（前后路联合治疗组）;单纯行颈后路单开门椎管扩大成形（后路开窗铆钉固定）28例（单纯后路治疗组）。治疗后随访6-24个月,分别对两组治疗后神经功能恢复情况、轴性症状的发生率及颈椎曲度指数、病变节段椎间滑移度进行统计分析。 结果与结论：两组患者的神经功能恢复均获得较好的日本骨科学会（JOA）改善率,前后路联合治疗组患者轴性症状的发生率相对低,颈椎曲度指数较单纯后路治疗组患者有较为明显的改善,而单纯后路治疗组椎间滑移度相对较大。结果表明一期前后联合入路使用 cage、前路钢板、后路铆钉行脊髓减压可以有效维持颈椎的生理曲度从而维持矢状面的平衡,减少患者轴性症状的发生率,对维持治疗后颈椎长期的稳定性起到重要作用。     

双能CT成像在显示膝关节韧带中的价值

目的 初步探讨双能CT成像在显示膝关节韧带中的价值.方法 对 12 例志愿者行膝关节双能CT 扫描,并均行容积显示(VRT)和多平面重建(MPR)等二维及三维图像后处理,用以显示膝关节的韧带.由2名有经验的放射科医生对图像进行分析.结果 膝关节部分韧带(膑韧带、前、后交叉韧带和腓侧副韧带)亦可清晰的显示;而较薄的韧带(胫侧副韧带)、横行的韧带(如膑内、外侧支持带)和后方的韧带(如恫斜韧带)显示欠佳.结论 双能CT是一种能够多方位、立体、直观地显示膝关节韧带的新方法,对临床应用具有一定的价值.     

Finite element analysis of the cervical spine: a material property sensitivity study

OBJECTIVE: The study determined the effect of variations in the material properties of the cervical spinal components on the output of the finite element analysis (external and internal responses of the cervical spine) under physiologic load vectors. DESIGN: A three-dimensional (3D) anatomically accurate finite element model comprising of the C4-C5-C6 cervical spine unit including the three vertebrae, two interconnecting intervertebral discs, and the anterior and posterior ligament complex is used. BACKGROUND: The effect of material property variations of spinal components on the human lumbar spine biomechanics is extensively studied. However, a similar investigation of the cervical spine is lacking. METHODS: Parametric studies on the variations in the material properties of all the cervical spine components including the cortical shell, cancellous core, endplates, intervertebral disc, posterior elements and ligaments were conducted by exercising the 3D finite element model under flexion, extension, lateral bending and axial torsion loading modes. Low, basic and high material property cases for each of the six components under all the four physiologic loading modes were considered in the finite element analysis. A total of 432 results were evaluated to analyze the external angular rotation, and the internal stresses in the middle vertebral body, the superior and inferior endplates and the two intervertebral discs. RESULTS: Variations in the material properties of the different cervical spinal components produced dissimilar changes in the external and internal responses. Variations in the material properties of the cancellous core, cortical shell, endplates and posterior element structures representing the hard tissues did not affect the external angular motion, and the internal stresses of the inferior and superior intervertebral discs under all four loading modes. In contrast, variations in the material properties of the intervertebral disc and ligament structures representing the soft tissues significantly altered the angular motion, and the stresses in the inferior and superior intervertebral discs of the cervical spine. CONCLUSION: The material properties of the soft tissue structures have a preponderant effect on the external and internal responses of the cervical spine compared with the changes in the material properties of the hard tissue structures. RELEVANCE: Bone remodeling (e.g., osteophyte) secondary to degeneration of the human cervical joints may be explained by a change in the material property of the soft tissues, coupled with an increase in stress (due to these material property variations) in the spinal components. Consequently, to accurately predict the biomedical effects of cervical spine degeneration, it is critical to accurately determine the material property of these components.     

颈椎后纵韧带骨化症的手术治疗并发症探讨

目的探讨颈椎后纵韧带骨化症的三种手术方式的疗效以及并发症。方法选择确诊为颈椎后纵韧带骨化症并进行手术治疗的患者168例,随进分为A组(颈后路手术组)、B组(颈前路手术组)、C组(前后路联合手术组)进行临床研究。研究三组疗效以及并发症发生情况。结果 A组手术后颈椎神经功能评分及改善率显著高于B组和C组,差异有显著性(P0.05)。A组患者的总体并发症为15.0%,显著低于B组(18.3%)和C组(45.0%),差异有显著性(P0.05)。结论三种手术方式在治疗颈椎后纵韧带骨化症的过程中均不可避免出现一些并发症,但是其中以颈后路手术的临床疗效较好,并发症较少。     

Effects of surgical joint destabilization on load sharing between ligamentous structures in the thoracic spine: a finite element investigation

Background

In vitro investigations have demonstrated the importance of the ribcage in stabilizing the thoracic spine. Surgical alterations of the ribcage may change load-sharing patterns in the thoracic spine. Computer models are used in this study to explore the effect of surgical disruption of the rib–vertebrae connections on ligament load-sharing in the thoracic spine.

Methods

A finite element model of a T7–8 motion segment, including the T8 rib, was developed using CT-derived spinal anatomy for the Visible Woman. Both the intact motion segment and the motion segment with four successive stages of destabilization (discectomy and removal of right costovertebral joint, right costotransverse joint and left costovertebral joint) were analyzed for a 2000 Nmm moment in flexion/extension, lateral bending and axial rotation. Joint rotational moments were compared with existing in vitro data and a detailed investigation of the load sharing between the posterior ligaments carried out.

Findings

The simulated motion segment demonstrated acceptable agreement with in vitro data at all stages of destabilization. Under lateral bending and axial rotation, the costovertebral joints were of critical importance in resisting applied moments. In comparison to the intact joint, anterior destabilization increases the total moment contributed by the posterior ligaments.

Interpretation

Surgical removal of the costovertebral joints may lead to excessive rotational motion in a spinal joint, increasing the risk of overload and damage to the remaining ligaments. The findings of this study are particularly relevant for surgical procedures involving rib head resection, such as some techniques for scoliosis deformity correction.     

High-speed subfailure stretch of rabbit anterior cruciate ligament: changes in elastic, failure and viscoelastic characteristics

OBJECTIVE: To study alterations in the ligament mechanical characteristics due to a subfailure stretch delivered at high speed. DESIGN: An in vitro study of rabbit anterior cruciate ligaments. BACKGROUND: Although ligamentous sprains occur more frequently than the complete failures, only a few biomechanical studies have investigated the effects of such injuries. Purpose of the study was to document changes in elastic, failure and viscoelastic properties of a ligament that had been subjected to a high-speed subfailure stretch. METHODS: Thirteen paired fresh adult rabbit femur-anterior cruciate ligament-tibia preparations were used. One ligament of each pair (control) was subjected to two relaxation tests and then stretched until failure. The other ligament (experimental) was subjected sequentially to relaxation test, subfailure stretch (80% of the failure deformation of the control), relaxation test, and then stretched until failure. Load-deformation curve until failure was characterized by nine parameters, which included failure force, deformation and energy absorbed, and deformations measured at various load values, and stiffness. Relaxation curve was parameterized by five relaxation forces measured at 10, 30, 50, 130, and 180 s. RESULTS: Due to subfailure stretch, there were no changes in failure force and stiffness, while deformations increased, and energy absorbed and relaxation forces decreased. CONCLUSIONS: The 80% subfailure stretch delivered at high speed increased the deformations in load-deformation tests, and decreased the forces in relaxation tests. Relevance. Incomplete injuries of the ligaments are more prevalent than the complete injuries. The incomplete injury is a subfailure stretch delivered at high speed. The present study provides the results of simulating the incomplete injury using an in vitro ligament model.     

Finite element simulation on posterior tibial tendinopathy: Load transfer alteration and implications to the onset of pes planus

BackgroundPosterior tibial tendinopathy is a challenging foot condition resulting in pes planus, which is difficult to diagnose in the early stage. Prior to the deformity, abnormal internal load transfer and soft tissue attenuation are anticipated. The objective of this study was to investigate the internal load transfer and strain of the ligaments with posterior tibial tendinopathy, and the implications to pes planus and other deformities.MethodsA three-dimensional finite element model of the foot and ankle was reconstructed from magnetic resonance images of a 28-year-old normal female. Thirty bones, plantar fascia, ligaments and tendons were reconstructed. With the gait analysis data of the model subject, walking stance was simulated. The onset of posterior tibial tendinopathy was resembled by unloading the tibialis posterior and compared to the normal condition.FindingsThe load transfer of the joints at the proximal medial column was weaken by posterior tibial tendinopathy, which was compromised by the increase along the lateral column and the intercuneiforms during late stance. Besides, the plantar tarsometatarsal and cuboideonavicular ligaments were consistently over-stretched during stance. Particularly, the maximum tensile strain of the plantar tarsometatarsal ligament was about 3-fold higher than normal at initial push-off.InterpretationPosterior tibial tendinopathy altered load transfer of the medial column and unbalanced the load between the proximal and distal side of the medial longitudinal arch. Posterior tibial tendinopathy also stretched the midfoot plantar ligaments that jeopardized midfoot stability, and attenuated the transverse arch. All these factors potentially contributed to the progress of pes planus and other foot deformities.     

Biomechanical comparison of spinal cord compression types occurring in Degenerative Cervical Myelopathy

BackgroundDegenerative Cervical Myelopathy results from spine degenerations narrowing the spinal canal and inducing cord compressions. Prognosis is challenging. This study aimed at simulating typical spinal cord compressions observed in patients with a realistic model to better understand pathogenesis for later prediction of patients' evolution.MethodsA 30% reduction in cord cross-sectional area at C5-C6 was defined as myelopathy threshold based on Degenerative Cervical Myelopathy features from literature and MRI measurements in 20 patients. Four main compression types were extracted from MRIs and simulated with a comprehensive three-dimensional finite element spine model. Median diffuse, median focal and lateral types were modelled as disk herniation while circumferential type additionally involved ligamentum flavum hypertrophy. All stresses were quantified along inferior-superior axis, compression development and across atlas-defined spinal cord regions.FindingsAnterior gray and white matter globally received the highest stress while lateral pathways were the least affected. Median diffuse compression induced the highest stresses. Circumferential type focused stresses in posterior gray matter. Along inferior-superior axis, those two types showed a peak of constraints at compression site while median focal and lateral types showed lower values but extending further.InterpretationMedian diffuse type would be the most detrimental based on stress amplitude. Anterior regions would be the most at risk, except for circumferential type where posterior regions would be equally affected. In addition to applying constraints, ischemia could be a significant component explaining the early demyelination reported in lateral pathways. Moving towards patient-specific simulations, biomechanical models could become strong predictors for degenerative changes.     

Effect of the transverse ligament rupture on the biomechanics of the cervical spine under a compressive loading

Background

In order to diagnosis a transverse ligament rupture in the cervical spine, clinicians normally measure the atlas–dens interval by using CT scan images. However, the impact of this tear on the head and neck complex biomechanics is not widely studied. The transverse ligament plays a very important role in stabilizing the joint and its alteration may have a substantial effect on the whole head and neck complex.

Methods

A finite element model consisting of bony structures along with cartilage, intervertebral discs and all ligaments was developed based on CT and MRI images. The effect of head weights (compressive load) of 30 N to 57 N was investigated in the cases of intact and ruptured transverse ligament joints. The model was validated based on experimental studies investigating the response of the cervical spine under the extension–flexion moment.

Findings

The predictions indicate a significant alteration of the kinematics and load distribution at the facet joints of the cervical spine with a transverse ligament tear. The vertebrae flexion, the contact force at the facets joints and the atlas–dens interval increase with the rupture of the transverse ligament and are dependent to the head weight.

Interpretation

A transverse ligament tear increases the flexion angle of the head and the vertebrae as well as the atlas–dens interval. The atlas–dens interval reaches a critical value when the compressive loading exceeds 40 N. Supporting the head after an injury should be considered to avoid compression of the spinal cord and permanent neurologic damage.     

一期前后路联合手术治疗多节段颈椎间盘突出合并后纵韧带骨化症

背景:多节段颈椎间盘突出合并后纵韧带骨化症会对患者产生严重的脊髓损伤,手术治疗方案目前仍存在争议.采取一期前后路的手术方式治疗能否达到满意效果尚不清楚.目的:观察采取一期前后路联合手术治疗多节段颈椎间盘突出合并后纵韧带骨化症的临床疗效.方法:选择武汉同济医院骨科收治的颈椎多节段颈椎间盘突出合并后纵韧带骨化症患者17例,男11例,女6例,年龄42～74岁,平均51.5岁;均采用一期前后路联合手术治疗.术前X射线,CT或MRI检查提示颈椎被多个节段的颈椎间盘突出和骨化的后纵韧带压迫.术后定期复查X射线观察融合率和稳定性及并发症发生情况.结果与结论:术后伤口均一期愈合情况,全体病例术后随访6-36个月,平均24.5个月.JOA术后6个月评分为(12.88±2.47)分,较术前(6.41±1.28)分明显提高(P<0.05).JOA评分改善率为:优5例,良7例,可4例,优良率71%.全体病例植骨在三四个月后均获得融合,颈椎间隙高度及生理曲度恢复满意,未出现内固定断裂、松动及脱出等并发症.提示对于治疗多节段颈椎间盘突出合并后纵韧带骨化症,一期前后路联合手术能早期彻底地减压并重建脊柱的即刻稳定性,是安全有效的手术方式.