You are in: eMedicine Specialties > Radiology > MUSCULOSKELETAL Lumbar Spine, TraumaArticle Last Updated: Apr 12, 2007AUTHOR AND EDITOR INFORMATIONSection 1 of 12
  Author: Lennard A Nadalo, MD, Clinical Professor, Department of Radiology, University of Texas Southwestern Medical School; Consulting Staff, Envision Imaging of Allen and Radiological Consultants Association Lennard A Nadalo is a member of the following medical societies: American College of Radiology, American Society of Neuroradiology, American Society of Pediatric Neuroradiology, Radiological Society of North America, and Texas Radiological Society Coauthor(s): Travis Van Meter, MD, Medical Director of the Department of Radiology, Section of Interventional Radiology, Methodist Medical Center; James A Moody, MD, Chief, Neurosurgery Section, Department of Surgery, Methodist Medical Center Editors: Michael A Bruno, MD, Associate Professor, Departments of Radiology and Medicine, Pennsylvania State University College of Medicine; Director, Radiology Quality Management Services, Milton S Hershey Medical Center, Pennsylvania State University College of Medicine; Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand; Theodore E Keats, MD, Professor, Departments of Radiology and Orthopedics, University of Virginia School of Medicine; Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute; Felix S Chew, MD, EdM, MBA, Professor, Department of Radiology, Section Head of Musculoskeletal Radiology, Vice Chairman for Radiology Informatics, University of Washington Author and Editor Disclosure Synonyms and related keywords: Chance fracture, pathologic fracture, burst fracture, insufficiency fracture, spondylolysis deformity, spondylolisthesis, lumbar spine trauma, lumbar spine injury, lumbar spine fracture INTRODUCTIONSection 2 of 12
  BackgroundFracture of the lumbar spine can occur whenever forces applied to the lower spinal column exceed the strength and stability of the spinal column unit. Common injuries resulting in fractures of the lumbar spine include fall from a height; motor vehicle and motor vehicle and pedestrian accidents; and penetrating trauma, including gunshot wounds and stabbings. Unstable injuries to the pelvis often are associated with injury to the sacral plexus and the lower lumbar spine. The goal of the diagnostic radiologist is to identify lumbar spine fractures correctly, to identify and correlate neurologic injury to vertebral fractures, to advise the surgeon (who best defines the extent of injury to supporting structures), to gauge the risk to the spinal cord, and to judge the stability of postoperative fixation. This article highlights the typical patterns of injury and focuses on the imaging methods that are most useful in the clinical practice of trauma radiology. For excellent patient education resources, visit eMedicine's Back, Ribs, Neck, and Head Center. Also, see eMedicine's patient education article Vertebral Compression Fracture. PathophysiologyFractures of the lumbar spine occur any time the combined forces of compression, distraction, and rotation exceed the strength of the spinal column. The predominant force determines the nature of the fracture dislocation. An example of a predominately distractive injury is a Chance fracture of the spine. A Chance fracture usually is a lower thoracic spinal or upper lumbar fracture with posterior ligament rupture. It represents a variant of the flexion distraction injury pattern. Usually, a minor anterior vertebral compression occurs (see Images 13-14). In a Chance fracture, the anterior column fails in tension, whereas a flexion distraction fracture primarily involves compression of the anterior column and distraction of the middle and posterior columns. The distinction is principally the relative degree of posterior ligamentous injury versus anterior compression. Of patients with flexion distraction injuries, 50% have rupture of the interspinous ligament, ligamentum flavum, facet capsule, posterior annulus, and thoracodorsal fascia. A traumatic compression fracture in a young patient (after a motor vehicle accident) should be considered a possible Chance fracture. Most Chance fractures that involve the lumbar spine occur at the L1 vertebral level (see Image 15); however, a similar injury pattern may occur at the L2 (see Image 16). Fractures associated with flexion are more common in the upper lumbar levels and less common in the lower lumbar and sacral areas. The lower lumbar spine (L4-S1) is stabilized by the large paraspinal muscles and the limited range of motion of the L5-S1 interspace. However, at the L1-L3 levels, a fulcrum of increased motion results in the potential for a combination of acute hyperflexion and rotation (see Images 17-18). Because the spinal cord terminates at the T12-L1 level, lower thoracic and upper lumbar spinal injuries at this level most commonly cause bladder and bowel signs and decreased movement and sensation in the lower extremities. A vertical compression force (see Image 19) may result in compression of the endplates of the vertebral bodies, or it may result in significant deformity and spinal canal compromise (see Images 20-26). The injury pattern may be primarily posterior, resulting in spinal cord injury (see Image 27). Significant anterior vertebral body injury can occur without causing spinal cord injury (see Images 28-29). Distractive injuries more commonly occur in the upper lumbar spine resulting from fixation of the pelvis with violent pulling of the upper spine. Fixed neurologic injury is common if the distraction is significant (see Image 30). Axial rotation occurs in the upper lumbar region. If the rotational forces are sufficiently great, a combined fracture and rotational subluxation occurs (see Image 31). Injury to the conus medullaris results. Pathologic fractures due to metastatic or metabolic bone disease can occur with relatively minor trauma (see Images 31-32). Compression of the lateral nerve roots or the conus medullaris results in variable degrees of weakness and pain. FrequencyUnited StatesIn young adults, lumbar spine fractures are commonly associated with multisystemic blunt trauma. The rate of spinal fractures in a serious motor vehicle accident is 5-6%; the L1, L2, and T12 levels are most frequently injured. Injuries are most common in patients aged 30-39 years and least common in persons younger than 18 years. Compression fractures are the most typical injury in the lumbar spine. The area of the lumbar spine most often injured is the thoracolumbar junction. InternationalSpinal fractures in the lumbar spine occur in people in all nations as a result of accidents and industrial injuries. The incidence of such injuries is proportionate to the number of motorized vehicles. In the developing nations of Asia, spinal fractures frequently are associated with spinal tuberculosis as well. Trauma related to military action occurs on a regional basis, based on current international relations. Mortality/MorbidityIn most lumbar fractures, the primary morbidity in patients is pain. Spinal pain may be seen in patients with acute fractures and fractures associated with advanced age. Mortality associated with lumbar spine fractures is primarily the result of associated injuries to the spleen, liver, aorta, and pelvis. Delayed mortality may be associated with urinary infections if the injury resulted in a neurotropic dysfunction of bladder control. Morbidity related to lumbar spine trauma often includes lower extremity weakness or paralysis and chronic pain. Neurologic recovery is best for fractures with kyphosis of greater than 15° and minimal compromise of the spinal canal. Such injuries have been associated with a greater than 90% likelihood of neurologic recovery. Fractures with kyphosis of less than 15° and maximum canal compromise are associated with a less than 50% likelihood of neurologic recovery. Fractures with kyphosis of 15° or less and maximum canal compromise at the level of the ligamentum flavum are associated with variable neurologic recovery. The prognosis for neurologic recovery can be estimated on the basis of the initial radiographic findings. A kyphosis of greater than 15° with only minimal deformity of the posterior aspect of the lumbar vertebral body is associated with a good prognosis. Race
Sex
AgeTwo age distributions are noted in the occurrence of lumbar spine fractures.
AnatomyThe lumbar vertebral bodies have a vertical height that is less than their horizontal diameter. An intervertebral disk lies between each lumbar vertebral body. The disk consists of the outer annulus fibrosis and nucleus pulposus (see Image 1). Generally, 5 similar lumbar vertebral bodies are distinguished from the thoracic bodies by the absence of rib facets (see Image 2). The pedicles project from the upper portion of the vertebral body. The spinous process is primarily horizontal in orientation, while the posterior inferior border projects below the upper level of the spinous process below. The laminae of the lumbar region are thick and project below the pedicles. The transverse processes are long and thin with a slant that is both upward and backward. The articular facets are heavier than those of the thoracic or cervical spine. The superior facets face medially, while the inferior facets face laterally. The interarticular joints are in a parasagittal plane (see Image 3). When viewed in an oblique projection, the outline of the facets and the pars interarticularis appear like the neck of a Scottie dog (see Image 4). The movement of the lumbar spine is largely confined to flexion and extension with a minor degree of rotation. The region between the superior articular process and the lamina is the pars interarticularis. A spondylolysis occurs if ossification of the pars interarticularis fails to occur. The primary ligamentous support for the lumbar spine is the anterior longitudinal ligament, the posterior longitudinal ligament, the attachments of the annulus fibrosis, the facet joints, and the interosseous ligaments between the spinous processes (see Images 5-6). Clinical DetailsTraumatic compression fractures represent a primarily vertical load injury with anterior or lateral flexion causing failure of the anterior column. The middle column remains intact and may act as a hinge (see Image 6). These fractures are usually stable and rarely involve neurologic compromise. The Denis classification system includes 4 types of compression fractures:
A lumbar spine burst fracture results from hyperflexion, which produces wedge compression of one or more vertebral bodies. Because of the rigidity of the ribcage, most of these fractures occur at the L1 or L2 level. The lumbar spinal canal is relatively wide in relation to the lower spinal cord and the conus; thus, lower thoracic spinal cord injuries are commonly incomplete. Kyphosis greater than 30° requires internal stabilization to prevent further deformity (see Image 18). Dural laceration with impaled nerve roots can be anticipated at the time of surgery if a patient with neurologic damage has a burst fracture of a vertebral body combined with a laminar fracture at the same level. The principal treatment for unstable lumbar spine fractures is surgical fixation with spinal canal decompression as needed (see Images 34-37). The area of injury commonly includes the lower thoracic and upper lumbar spine (see Image 38). Instability is usually associated with kyphosis of 20° or more. The primary posterior approach is accomplished by means of the Harrington rod system. Adverse effects resulting from the locking of vertebral segments and incomplete reconstitution of the vertebral height have been reported. An alternative posterior approach involves pedicular fixation in which 2 segments are fused. The procedure results in both fracture reduction and fixation. The injured vertebra also is grafted through the pedicle. Clearance of bone fragments from within the spinal canal is an important goal for most surgical approaches to lumbar spine fractures. Patients with complete paraplegia can be expected to remain unchanged. Preferred ExaminationA general outline for the evaluation of acute multiple trauma involving the spine is shown in Image 7. At the least, standard anteroposterior (AP) and lateral radiographs should be obtained in all patients. Oblique views are useful if the AP and lateral views demonstrate scoliosis or a questionable defect of the posterior spinal elements. Flexion and extension views are helpful if subluxation is detected or if a chronic injury may be present. In all patients with compression fracture, the anterior height of the vertebral body is diminished, whereas the posterior height remains within normal limits. No subluxation of vertebral bodies is present. The anterior compression is less than 40% unless a burst fracture is present (see Images 8-9). After conventional radiography, CT is the primary means used to depict the posterior elements, which is necessary to exclude posterior instability and vertebral body deformity. CT scans are better in depicting the spinal canal and in estimating the degree of neural compromise. In a burst fracture, CT best demonstrates posterior spinal element involvement (see Image 10). Axial CT scans fail to demonstrate subtle horizontally oriented injuries of the vertebral bodies, pedicles, or laminae. Also, axial CT scans may not depict minimal vertebral body compression fractures. The use of frontal and sagittal reformation, together with thin primary imaging sections, can overcome most of these limitations (see Images 11-12). Many patients who present with lumbar spine injury have pulmonary, rib, or vascular injury. The expense and delay of obtaining routine CT scans of the lumbar spine are not justified. A review of the bone windows of thoracic and abdominal CT scans reveals most major deformities that are associated with Chance fracture, distraction injury, and burst vertebral fractures. More complex injuries can be studied later if necessary, but multisection CT studies can be reformatted to examine the lumbar spine in a lateral (sagittal) view. The use of MRI in spinal trauma should be linked to neurologic examination or unexplained severe spinal pain. MRIs of the lumbar spine provide information that is not available with CT scans. Early in an injury, T1-weighted spin-echo (SE) axial and sagittal images may demonstrate the high signal intensity related to acute hemorrhage, including the rare complicating epidural hemorrhage. Both T2-weighted fast spin-echo (FSE) and fluid-attenuated inversion recovery (FLAIR) images demonstrate the high signal intensity associated with edema of bone marrow fat. Gradient-echo T2-weighted images best outline the shape and structure of the vertebral body and the posterior spinal elements. These MRIs are superior to CT scans for the detection of a posttraumatic herniated disk, ligamentous edema, and spinal cord compression. Gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA) contrast enhancement should be used in patients with suspected metastatic disease and septic spondylosis, diskitis, or osteomyelitis (see Image 16). Gadolinium-based contrast agents (gadopentetate dimeglumine [Magnevist], gadobenate dimeglumine [MultiHance], gadodiamide [Omniscan], gadoversetamide [OptiMARK], gadoteridol [ProHance]) have recently been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). For more information, see the eMedicine topic Nephrogenic Fibrosing Dermopathy. The disease has occurred in patients with moderate to end-stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or MRA scans. As of late December 2006, the FDA had received reports of 90 such cases. Worldwide, over 200 cases have been reported, according to the FDA. NSF/NFD is a debilitating and sometimes fatal disease. Characteristics include red or dark patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow spots on the whites of the eyes; joint stiffness with trouble movingor straightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness. For more information, see the FDA Public Health Advisory or Medscape. Occult injury associated with lumbar vertebral body compression may be better assessed by using nuclear medicine bone scanning than with other techniques. Technetium-99m hydroxydimethylpyrimidine (HDP) is most commonly administered for this test. Chronic injuries demonstrate moderately increased activity, whereas acute fractures usually demonstrate a focally increased activity. Limitations of TechniquesRadiographs may not clearly demonstrate the posterior spine elements, and excluding a Chance fracture can be difficult. Also, although most compression fractures in older patients are benign, a significant number of spontaneous compression fractures are related to metastatic disease. Follow-up imaging with contrast-enhanced MRI is indicated in all patients in whom a mass is noted and in all patients in whom a primary malignancy is suspected. Axial CT scans may fail to depict subtle horizontally oriented injuries of the vertebral bodies, pedicles, or laminae. Axial CT scans also may miss minimal vertebral body compression fractures. The use of frontal and sagittal reformation, together with thin primary image sections, can overcome most of these limitations. The resolution of MRIs used in the detection of spinal fractures is limited. Although gradient-echo and T1-weighted SE images outline fractures better, minimally displaced fractures are difficult to see. Although nuclear medicine bone scans are sensitive to the processes that destroy or injure bone, a positive area of increased uptake on a bone scan is not specific for fracture. The fracture may not be detected for as long as 72 hours after an injury. The resolution of fracture outlines is poor with nuclear medicine studies. Large osteophytes and intervertebral disk narrowing with vertebral endplate sclerosis may appear as areas of increased activity on standard nuclear bone scans. CT scans of the lumbar region may help making the diagnosis if the results of a bone scan are positive. MRI is most effective in the identification of neoplasm and osteomyelitis. DIFFERENTIALSSection 3 of 12
Arachnoid Cyst Hemangioma, Bone Multiple Myeloma Osteomalacia and Renal Osteodystrophy Osteomyelitis, Chronic Osteoporosis, Involutional Septic Arthritis Spondylolisthesis Spondylolysis RADIOGRAPHSection 4 of 12
FindingsStandard radiographic views are AP, lateral, and oblique. AP radiographs are obtained with the patient supine. The patient's knees are flexed to reduce lumbar lordosis. The x-ray beam is directed toward the central abdomen over the umbilicus and the iliac crests. When a lateral lumbar radiograph is obtained, the patient lies on either side with his or her knees and hips flexed. The x-ray beam is directed toward the body of the L3 vertebral body. Radiographs in the oblique view are obtained with a 45° rotation, with the central beam directed toward the L3 vertebral body. In the AP view, the interpedicular distances are noted to increase from L1 to L5. On the lateral view, the vertebral body of L1 is often slightly anteriorly wedged without buckling of the anterior cortex or condensation of endplates. Soft tissue swelling may indicate a fracture even if the fracture is not directly visualized. Structures that are best seen on the oblique views include the transverse process and pedicle on the dependent side and the pars interarticularis. Among the more serious injuries to the lumbar spine, the burst fracture is usually easily detected by using standard radiographs of the lumbar spine. In the lateral view, criteria for instability include a greater than 50% loss of vertebral body height, a greater than 20° angulation of the thoracolumbar junction, neurologic injury, and a canal narrowing of greater than 30%. Early surgical repair is indicated for such an injury, because additional compression of the fracture and more severe neurologic injury can be expected if weight bearing is attempted without surgical fixation. The normal thoracolumbar spine junction has a 0° angle between the T12 and L1 levels. Another common injury pattern involves an avulsion injury to the transverse and/or spinous processes. Fractures of the lower lumbar transverse spinous processes associated with an unstable pelvic fracture may indicate injury to the sacral plexus. Fractures of transverse processes may be associated with visceral trauma as well. Oblique views of the lumbar spine are useful in the evaluation of spondylolysis of the pars interarticularis. The so-called Scottie dog configuration may demonstrate a defect in the "neck" of the dog-shaped configuration in patients with spondylolysis. In cases that involve chronic pain or potential instability after surgical stabilization, standing flexion-extension lateral radiographs are useful for detecting spondylolisthesis. Flexion-extension maneuvers are well within the normal range of motion of most patients after spinal fusion. After the initial healing period of 12-24 weeks, moderate flexion-extension movements are safe. Instability and subluxation indicate a primary failure of the fusion surgery. All initial attempts to evaluate weight bearing should be monitored and limited by pain or the onset of neurologic complaints. Degree of ConfidenceThe degree of confidence is directly related to the severity of the spinal deformity and inversely related to technical factors such as the size of the patient, patient movement, and the type of radiologic equipment available. False Positives/NegativesCommon false-positive signs of fracture in the lumbar region occur due to superimposed bowel gas and un-united secondary ossification centers. A limbus vertebra is a small accessory bone noted superior and anterior to the vertebral endplate not associated with acute trauma. Unilateral sacralization of L5 may suggest a fracture on AP and oblique radiographs. The best interobserver agreement can be obtained by measuring from the superior endplate of the vertebral body one level above the injured vertebral body to the inferior endplate of the vertebral body one level below. False-positive findings can result from previous (chronic) kyphosis due to osteoporosis or prior injury. Kyphosis after trauma is best compared by using prior lateral radiographs if they are available. A common variant is the combination of spondylolisthesis and spondylolisthesis. Because of a defect in the pars interarticularis, anterior-posterior movement occurs along the plane of 2 related vertebral endplates. This is most common at the L5-S1 levels. Although the resulting deformity is considered to be a developmental defect, it may be mistaken for an acute injury pattern. A false sign of spondylolysis may result from the wrong radiographic angulation. The oblique lateral view should be obtained by using a 15° cephalic angulation. Occasionally, a similar pattern is noted; this pattern is related to severe degenerative disease of the facet joints that results in instability and a moderate spondylolisthesis. CT SCANSection 5 of 12
FindingsThin-section axial CT scanning with a bone algorithm is the single most sensitive means by which to diagnose fractures of the lumbar spine. Routine helical CT scans of the lumbar spine are valuable because multisection CT scanners can generate high-resolution spinal images, even during a primary multisystemic evaluation for trauma. Good-quality CT images can be used to identify more lumbar spine injuries than conventional radiographic studies; however, the percentage of clinically important spinal fractures seen in the lumbar region on CT scans and not seen on radiographs is lower than that of similar studies of cervical spinal fractures. Most of the fractures missed on radiographs are spinous process fractures, transverse processes fractures, and fractures in large patients. With the introduction of multisection CT scanners, a careful evaluation of the lumbar spine is possible in all patients without performing a specific examination tailored to the lumbar area. In general, the appearance of fractures on CT scans demonstrates injuries similar to those on radiographs of the lumbar spine. As a result of its superior contrast definition and the absence of superimposed structures, CT imaging of the spine is highly effective and accurate in the diagnosis of fractures. The confidence level for the diagnosis of a lumbar spine fracture with 2-mm axial sections (possible with a multisection CT unit) is greater than 98% and has been reported to be 99%. Because axial CT is performed with patients in a neutral position, bony distraction of the fracture fragments and subluxations of the spinal articulations may not be as significant on CT images as on an acute trauma series of radiographs. The level of a burst fracture and the percentage of spinal canal stenosis have been correlated with an associated neurologic deficit. A significant correlation exists between neurologic deficit and the percentage of spinal canal stenosis. Injuries to the T12 and L1 spine pose a greater probability of neurologic deficit. This observation may be related to the smaller canal diameter in the thoracic-lumbar spinal junction. The severity of neurologic deficit cannot be predicted. Associated injuries, including acute lumbar disc herniations, are usually well depicted on CT scans of the lumbar spine. Paravertebral bleeding and the presence of foreign bodies are also easily detected by using CT. Degree of ConfidenceThe confidence level for the diagnosis of a lumbar spine fracture with 2-mm axial sections (which is possible with a multisection CT unit) is greater than 98% and reportedly 99%. Traumatic lumbar spine disk herniations are detected in 85-92% of cases. False Positives/NegativesBecause axial CT is performed with the patient in a neutral position, bony distraction of the fracture fragments and subluxations of the spinal articulations may not be as significant on CT images as on acute trauma series radiographs. False-positive results may occur in patients with a Schmorl node, which is a chronic internal herniation of the vertebral disk into the lumbar vertebral body endplate and failure of the fusion of the anterior vertebral endplate epiphysis. False-negative CT studies may occur in chronic stress injury and severe generalized osteoporotic endplate fractures. A posttraumatic disk herniation may be undetected in large patients and in patients who have undergone prior lumbar spine surgery. MRISection 6 of 12
FindingsSpinal MRI is a highly effective means for detecting and evaluating lumbar spine trauma. Images are obtained in multiple projections. With a 1.5-T MRI unit, both T1-weighted SE techniques (recovery time [TR], 600 ms; echo time [TE], 14 ms) and T2-weighted FSE (TR, 2000 or 3200; TE, 112) techniques are performed. Lumbar spine MRIs can demonstrate many vertebral fractures and most abnormalities of alignment. The patterns of injury are similar to those demonstrated on radiographs. MRI is superior to both radiography and CT in the detection of soft tissue injury to the ligaments, facet capsules, and the prevertebral spaces. MRI is unique in its ability to detect epidural bleeding and spinal cord injury. Injury to the lower thoracic cord is particularly critical because such injury may result in paralysis. However, MRI has fewer line pairs of resolution than does CT, which makes MRI a secondary method for fracture evaluation. Gradient-echo sagittal T2-weighted MRI of the spine demonstrates the compression fracture by showing the cortical bone as dark (black), whereas the T2-weighted quality shows cerebrospinal fluid and spinal cord edema as bright (white). Subacute hemorrhage in the spinal cord or in the epidural space may be seen as a susceptibility area of lost signal intensity. With a T2-weighted gradient-echo technique, the cortical break can be demonstrated in some fractures. MRI is superior to CT in the identification of the indirect signs of a fracture, such as paraspinal edema or hemorrhage, epidural bleeding, and sprains of the paraspinal and intraspinal ligaments. Paraspinal soft tissue injury and posttraumatic disk herniation are best depicted by using MRI. Spinal MRI may also be useful in predicting the development of Schmorl nodes and vertebral endplate compression fractures. The fraction of the vertebral body composed of fat increases with age. MR spectroscopy demonstrates an increased fat fraction in abnormally weak vertebral bone. MRI findings of bone weakness are more common in older patients with abnormally high fat fractions than in others. Degree of ConfidenceLumbar spine MRIs can demonstrate many vertebral fractures and most abnormalities of alignment. MRI is superior to CT in the identification of indirect signs of a fracture such as precervical edema or hemorrhage, epidural bleeding, and sprains of the paraspinal and intraspinal ligaments. Associated injuries to intracranial structures are evaluated better by using MRIs than by using CT images. False Positives/NegativesFalse-positive MRI results are often associated with movement artifacts of metal near the site of injury. Blood vessel canals may mimic bone injury. The use of upper cervical and intracranial magnetic resonance angiography may help in differentiating certain vascular variations. False-negative findings may result from motion on the part of the patient. Artifacts related to implanted metal may mask spinal fractures. In older patients or in patients with known neoplastic disease, a pathologic fracture should be considered. In these patients, MRI with Gd-DTPA enhancement demonstrates a spinal mass or osteomyelitis. MRI has a lower overall resolution than that of CT scanning. With T2-weighted gradient-echo sequences, the cortical break can be demonstrated in some fractures; however, even with adequate MRI technique, minimally displaced fracture lines may not be seen by using MRI. Patients who had undergone prior lumbar surgery should be examined after the intravenous injection of contrast agent to differentiate between an epidural scar and a recurrent herniated nucleus pulposus. ULTRASOUNDSection 7 of 12
FindingsThe use of paraspinal ultrasonography is usually limited to the localization of pleural effusions, which may occur after significant upper lumbar spine and chest wall injury. Paraspinal abscess may be localized prior to aspiration in selected patients. Because of the proximity of the kidneys and ureters to the lumbar spine, the sonographic findings may indicate perinephric hemorrhage or urinary obstruction. Degree of ConfidenceSonography should be used only in selected patients. The primary findings of soft tissue swelling and possible hemorrhage are not specific to lumbar trauma. False Positives/NegativesMasses, urinary leaks, and perispinal abscess may have sonographic findings similar to those of paraspinal hemorrhage. NUCLEAR MEDICINESection 8 of 12
FindingsNuclear medicine studies have a limited role in the acute phase of lumbar spine injury; however, in patients with a possible congenital anomaly, an acute fracture can be differentiated from failure of an epiphyseal endplate to fuse. After 24 hours, a bone scan obtained by using 99mTc HDP generally demonstrates increased uptake in the area of a fracture. A delay of as long as 72 hours may be necessary to identify some fractures. Later in the clinical course, persistent back pain may be caused by a nondisplaced facet injury or pedicle fracture, which is also associated with an area of increased uptake. After surgery or in open spinal fractures, diskitis and osteomyelitis can be identified as focal areas of increased activity by using 99mTc HDP or gallium-67 citrate. Indium 111–tagged white blood cells act as a more specific agent in the detection of abscess and osteomyelitis; however, the sensitivity of this method depends on the nature of the infectious organism. Degree of ConfidenceIn the absence of prior surgery, radionuclear bone imaging is fairly sensitive but not specific for spinal trauma. If bone scans are needed, SPECT imaging should be used in all patients with suspected spinal trauma. The presence of fixation plates, wires, and screws makes the assessment of postoperative spinal injury difficult. In all patients, the tomographic qualities of single-photon emission computed tomography (SPECT) improve both the accuracy and specificity. False Positives/NegativesMany false-positive findings can be expected in older adults. Osteomyelitis, diskitis, metastatic disease, degenerative spondylosis, rheumatoid arthritis, and ankylosing spondylitis may result in abnormal findings in the spine that are not directly related to acute trauma. In the young child, variations of spinal development may mimic acute injury. False-negative results may occur in the first hours after acute trauma. If possible, 72 hours should be allowed to pass prior to nuclear bone scanning of the lumbar spine is attempted. Also, false-negative results are fairly common with In-111 WBC scans, and an approach involving a combined bone-gallium scan is preferred. ANGIOGRAPHYSection 9 of 12
FindingsAngiography plays a limited but critical and indirect role in assessing lumbar spine injury. After a gunshot wound to the back, injuries to the aorta and the proximal great vessels are best evaluated by using angiography. Flank pain may be the result of bleeding or hydronephrosis. New higher-resolution CT angiography makes catheter angiography less essential. The evaluation of injury to the major vessels is routinely performed during the assessment of patients with multisystemic trauma. Degree of ConfidenceThe higher resolution of digital subtraction angiography results in excellent image quality. Rarely are other vascular images necessary. Angiography typically is reserved for possible interventional repair of arterial injuries and for patients in whom the diagnosis is uncertain. False Positives/NegativesStanding waves may mimic vascular injury with spasm. In the older adult, arteriosclerotic vascular disease may mimic spasm. Lumbar arteries may be in spasm at the time of an examination, preventing localization of a bleeding site. INTERVENTIONSection 10 of 12
Primary treatment Primary intervention in acute lumbar spine fractures is unusual. Occasionally, the placement of a lumbar spine drainage catheter improves the likelihood of primary closure of a dural tear in the lumbar area. Intraoperative radiography provides important information that may require consultation between the radiologist and the surgeon in the operating room. Drainage of a pleural effusion may be needed in patients with chest wall trauma. Thoracentesis is most easily performed by using ultrasonographic guidance. In selected pathologic fractures and in many osteoporotic fractures of the lumbar spine, relieving chronic pain is possible, as is prevention of further deformity of the lumbar vertebral body using injections of radiopaque bone cement (see Image 39). Vertebroplasty may be performed by using fluoroscopic or CT guidance. A large trocar needle is introduced into the anterior midportion of the affected vertebral body. The semisolid cement is injected by using imaging control to avoid spilling the cement into the epidural spaces. The cement fills many of the diseased areas within the vertebral body. The resulting cast supports the vertebral endplate, relieving pain in many patients (see Image 40). Surgical repair, including anterior decompression, posterior fusion with decompression, and the use of multisegmental hook systems, provides added spinal canal diameter and multiple points of distraction on the same spinal rod. After confirmed removal of the cause of compression, patients rarely lose further cord or cauda equina function after anterior decompression. Most patients who present with a motor deficit improve in motor strength by at least one class. Most patients with conus medullaris injury have neurogenic bowel and bladder recovery. Estrogen therapy Although estrogen has been proposed as a treatment agent to prevent compression fractures in women who are postmenopausal, an increased risk of chronic pain related to lumbar spine fractures has been associated with estrogen therapy. A significantly higher percentage of current estrogen users reported clinical back pain and back impairment at baseline and at the follow-up visit. This effect occurred despite a higher prevalence of vertebral fractures at the baseline visit in women who had never used estrogen. Treatment of burst injuries One of the primary clinical decisions that must be made early in the treatment of burst injuries of the upper lumbar spine is whether immediate surgical decompression of the spinal canal is indicated. An anterior surgical approach has been advocated because of limited access to retrodisplaced bone fragments with a posterior approach. An aggressive approach, including anterior decompression, is most important in patients with partial spinal cord injury patterns. Improvement is reported in patients in whom partial neurologic function is preserved after injury. All patients with complete paraplegia fail to show signs of recovery. The probability of recovery after a burst fracture in the lumbar spine can be predicted on the basis of the initial fracture pattern, which can often be determined by using acute trauma radiographs. However, the initial severity of paralysis is not closely correlated with initial fracture patterns or canal compromise, as demonstrated on CT scans. Medical/Legal Pitfalls
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