胸腰椎骨折的影像學(xué)

Imaging of Thoracic and Lumbar Spine Fractures,Fractures of the thoracic and lumbar spine are common in patients who have sustained high-energy spinal trauma, and are associated with injury to the spinal cord in up to 50% of cases .1Accurate early assessment is essential because delay in diagnosis may result in the development of neurologic complications. Clinical assessment of these patients is often challenging,and as a result,diagnostic imaging usually plays a central role in our management.,1. Diaz JJ et al.Practice management guidelines for the screening of thoracolumbar spine fracture.Trauma 63:709-718,2007,The purpose of this slides is to explore this role by answering the following 4 questions: (1) What are the imaging options? (2) Who should be imaged? (3) How should they be imaged? (4) What are the imaging findings for the most common types of thoracolumbar fractures?,1. What are the imaging options?,RadiographyRadiography is typically the first modality used to evaluate the thoracolumbar spine after trauma.In the thoracic spine, anterposterior (AP) and lateral views are usuelly supplemented with a swimmers lateral view (y)In the lumbar region, AP and lateral views are typically sufficient.,Arrowheads: left paratracheal stripeBlackarrow: interdediculate distanceWhitehead: C7 vertebra,Normal lumbar spine,Computed TomographyThe advent of computed tomography (CT) has revolutionized spine imaging.This technique allows for very rapid scanning and results in the acquisition of a continuous dataset that can be used to create extremely thin axial slices as well as exquisite reconstructed images in any plane.,An additional advantage of this technique is that data from CT scan of the chest, abdomen,and pelvis obtained to evaluate for visceral injury can be uesd to simultaneously generate reconstructed images of the spine without the need for rescanning the patient.,CT is clearly superior to radiographs for demonstrating fractures of the thoracolumbar spine with a sensitivity of 94%-100% compared with 33%-73% for radiographys. 2CT is also more accurate than MRI for detecting factures,2. Berry GE et al:Are plain radiographys of the spine neccessaryduring evaluation after blunt trayma?Accuracy of screening torso CT in thoracic/lumbar spine fracture diagnosis.JTrauma 59:1410-1413,2005,Analysis of images in all 3 standard planes is necessary.Additionally,images should be viewed using “bone” windows to detect osseous injuries as well as “soft tissue” windows to look for associated abnormalities such as a disc protrusion or epidural hematoma.,A : sagittal(midline) B : parasagittal C :coronal,Magnetic Resonance ImagingWhile CT is best for detecting fratures, MRI is superior for demonstrating soft tissue pathology such as intrinsin cord injury,ligament pathology,hematoma,or muscle tear. 3,3. Slucky AV:Using magnetic resonance imaging in spinal trauma:indications,techniques,and utility.J AM Acad orthop Surg 6:134-145,1998,T1-weighted sequences provide a good overall display of anatomy and are recognized by the low signal intensity of the cerebrospinal fluid on these images.T2-weighted imaging,which results in bright signal from fluid ,is best for detecting pathology because of the increased fluid content in areas bone or soft tissue injury,2. Who Should Be Imaged?,Delay in diagnosis of a thoracolumbar fracture may result in a higher incidence of neurologic complications. Thus highlighting the need for rapid and accurate assessement of these patients,and raising the important question of which patients with a history of spine trauma should undergo further investigation with diagnostic imaging?,Not all patients with with a history of spine trauma should be evaluated with diagnostic imaging .There are a numerous criteria that are useful for determining which patients should undergo further diagnostic imaging . 4,4. Hsu JM et al:thoracolumbar fracture in blunt trauma patients: guidelines for diagnosis and imaging.Injury 34:426-433,2003,These include A high energy mechanism(fall from10 ft (3m), ejection during a motor vehicleaccident, etc.)An altered level of consciousnessA major distrcting injuryA known fracture anywhere in the spine,3. How Should They Be Imaged?,Screening:Radiography or CT?Although screening the spine with CT is now recommended for patients who have a history of high-energy trauma,radiographys are probably adequate for those who have sustained a low-energy.If there is any suggestion of a fracture on radiographys,further evaluation with CT is indicated,because of the known limitations of radiographys,A comprehensive scan of the entire spine, chest, abdomen, pelvis can be obtained CT is now recommended as the screening modality of choice for blunt trauma patients who are at high risk for spinal injury.,MRIThe ability of MRI to directly display the cord,disc material,epidural hematoma,and ligaments makes it a powerful complementary modality to CT.Thus MRI should be reserverd for the patient who has a neurologic deficit ,ligamentous injury,and high suspicion of injury in radiography or CT studies.,Imaging Findings,Normal AnatomyRadiographysVertebral alignment should also be assessed on the AP view along with the interpediculate distance (the distance between the inner margins of the pedicles).,The distance between the pedicles normally decreases from the level of T1 through T6 and then increases gradually from T6 through L5. Paraspinal soft tissue “stripes” are also visible on the AP film of the thoracic spine with the stripe on the left normally wider than that on the right owing to the presence of the descending aorta in that region,CTOsseous anatomy should be evaluated using a “bone window” display that provides for optimal assessment of cortical and trabecular detail. sagittal images are most useful for assessing vertebral and facet alignment. Similarly, soft tissue structures should be evaluated using a dedicated “soft tissue” display. allowing for detection of epidural hematoma or a trauma-related disc protrusion,B: epidural hematoma that with relative high density,MRIvertebral elements are of predominantly high signal intensity on T1-weighted images. The spinal cord is of intermediate signal (similar to skeletal muscle) on all pulse sequences, whereas the surrounding cerebrospinal uid will appear dark on T1-weighted images and very bright on T2-weighted images,A normal intervertebral disc appears gray on a T1-weighted sequence, but shows differentiation between the high signal nucleus pulposis and lowsignal annulus brosis on T2 or STIR images.,Thoracolumbar FracturesGeneral CommentsThe type of injury that occurs with blunt trauma to the spine is related to the forces acting upon it at the moment of injury and may involve exion, extension, compression, distraction, rotation, or shear forces. In general, pure compressive or distractive forces tend to produce fractures, whereas rotatory and shear forces often result in dislocations.,Most injuries of the thoracic and lumbar spine occur near the thoracolumbar junction for a variety of reasons: (1) the ribcage provides additional stability for the rst 9 thoracic vertebrae (2)motion is greatest in this region of the thoracolumbar spine; (3) the facet joints transition from a predominantly coronal orientation in the upper thoracic spine to a more sagittal orientation in the lumbar spine, resulting in less resistance to exion in the lower thoracic and lumbar regions.,Thoracic spine injuries above the thoracolumbar junction are less common, but have a high incidence of associated neurologic injury. (2 reasons),Classication SystemsIn 1984, Denis proposed a 3-column classication system for thoracolumbar injuries.,Thoracolumbar fractures were also divided into “minor” and “major” groups. Minor fractures included those involving the spinous process, transverse process, and pars intra-articularis. Major fractures were broken into 4 categories: compression, burst, exion-distraction, and fracture dislocation.,Fracture Types1. Compression Fracture On MR images, in addition to anterior wedging, an acute compression fracture will indicate edema-like signal intensity within the marrow of the affected vertebral body. This is most conspicuous on a T2-weighted image. The absence of this type of signal within a compressed vertebra indicates an old, healed fracture.,A(T1):2 thoracic fracturesB(T2):pronounced edema relative to the more proximal fracture,As a result, MRI can be useful in differentiating acute from chronic injuries,2. Burst Fracture Involves the middle column (posterior vertebral cortex) in addition to the anterior and sometimes posterior columns as well,3. FlexionDistraction (Chance Fracture) This type of fracture was found to be associated the use of a lap seat belt.,4. FractureDislocation Fracturedislocation injuries are usually the result of compression and/or distraction forces combined with some degree of shear or rotation. These severe injuries are extremely unstable because they result in failure of all 3 columns, and are associated with the highest inci- dence of complete neurologic injury of any of the thoraco- lumbar injury patterns.