No doubt it is history’s most famous radiograph, and bones (and a wedding ring) are the subject. Wilhelm R?ntgen published the image of his wife’s hand to demonstrate the utility of the form of energy he had discovered; not knowing its nature, he called it “X” rays. For decades, those X-rays and the plain films produced from them were the principal means of examining the musculoskeletal system. Today, many more options are available; this article examines a few of them.
The Standard: MRI
The utility of MRI for depicting muscles was apparent from the earliest days of the modality. Today, aided by the availability of open scanners, including those that permit a patient to stand or sit, and its multiplanar and three-dimensional capabilities, MRI is the standard imaging study for a large variety of musculoskeletal conditions. Injection of gadolinium agents into the joint (MR arthrography) aids in the diagnosis and monitoring of joint disorders.1 Also important is kinematic MRI, which arose from the recognition that it often is necessary to place a joint in a particular position or under load to find out what is wrong with it. Thus, the joint is manipulated through its range of motion, with or without a load, while being kept in the proper imaging plane. This manipulation is provided by a positioning device, which may contain a surface coil. Cin? displays of the images increase their utility.
New ways of using MRI in orthopedics appear almost monthly. The modality may be more sensitive than scintigraphy in identifying vertebral metastases of cancer,2 and it permits earlier diagnosis of rheumatoid arthritis.3,4 MRI also has been used to assess the utility of a new operation for repair of lumbar disk herniation5 and to monitor the progress of brace correction of scoliosis.6 Annual MRI scans will be central to the government-industry Osteoarthritis Initiative. Some researchers are exploring the potential of virtual MR arthroscopy.7
Like MRI, nuclear medicine is an important element of musculoskeletal imaging practice.
A quarter of a million hip replacements, and even more knee replacements, are done every year in the United States. These patients may live for decades after the surgery, so it is to be expected that many patients will present with pain some months postoperatively. Has the hardware loosened? Is the area infected? Is there heterotopic ossification? Is there some biomechanical instability?
Nuclear medicine studies are often called on to answer these questions, both because of the information they provide about tissue physiology and because the presence of orthopedic hardware interferes with CT and, of course, MRI.
The present application of scintigraphy was described by Lawrence E. Holder, MD, Professor Emeritus of Radiology and Nuclear Medicine at the University of Maryland, Baltimore, and coauthor of a new textbook on nuclear imaging of the bone.8
“For scintigraphy or, increasingly, SPECT, a technetium-labeled diphosphonate tracer is administered; these compounds localize in areas of increased blood flow or higher rates of metabolism and are detected with ultrahigh-resolution gamma cameras or SPECT. The latter has an advantage in that you obtain tomographic images, which allow you to view the region of interest from various perspectives or eliminate structures that interfere with your examination.”
Holder also uses scintigraphy or SPECT in examining patients for bony metastases or arthritic processes and in some cases of multiple trauma.
“It is not practical to do MRI or CT under these circumstances,” he pointed out, “because you would have to scan the entire body and look for subtle changes.”
Positron emission tomography (PET) has a growing role in examining the bones.
Abass Alavi, MD, professor of radiology and chief of the Division of Nuclear Medicine, Hospital of the University of Pennsylvania, Philadelphia, believes that PET with fluorine 18-labeled deoxyglucose (FDG) will be important in identifying bone infection. In a study he and his colleagues reported at the Society of Nuclear Imaging (SNM) meeting in Toronto in June, the positive and negative predictive values and accuracy of FDG PET in chronic osteomyelitis were 88%, 95%, and 93%, respectively.9 For patients with infected prostheses, the corresponding values were 91%, 97%, and 92%. Another group of investigators found the sensitivity and specificity of FDG PET in implant-associated infections to be 100% and 93%, respectively,10 and a multicenter German trial found a sensitivity of 100% and a specificity of 50% in patients with osteomyelitis.11
A standard criticism of almost every new imaging technique is that it is too costly. However, FDG PET may be less expensive than thought at first glance.
“For conventional scintigraphy for infection, you take a sample of the patient’s blood, isolate the leukocytes, label them with technetium or indium, return them to the patient, and wait 24 hours to see where they go. This is a time commitment of 6 to 7 hours for the radiology team,” Alavi points out. “Alter-
natively, you can administer radiolabeled antibodies to tag the leukocytes in vivo, which represents a cost of $700 to $1,000 per dose. With FDG PET, the tracer costs $200 or less, and the study is completed within 2 hours of the patient’s admission. In our institution, the cost of FDG PET is half that of scintigraphy for possible bone infection.”
A direct comparison of FDG PET and scintigraphy was reported by Frederic de Winter, MD, of Ghent University in Belgium at the SNM meeting last year. In this retrospective study, FDG PET was 100% sensitive and 92% specific in identifying infection of the central skeleton and 100% sensitive and 90% specific in peripheral skeletal infection. The corresponding figures for scintigraphy were 33% and 91% in the central skeleton and 86% and 90% in the peripheral skeleton.
Holder sees some clinician resistance to making full use of nuclear medicine studies.
“Everyone finds it easier to look at the images you get with CT and MRI. It is less easy to appreciate the physiologic events that are being depicted with nuclear imaging. Nuclear medicine has always required a champion who will educate the clinicians about what the studies can do.”
Ultrasonography Finds a Place
A Money-Saving Tip: Forego It
The least expensive imaging study is the one that is not done. Many studies ordered for two common musculoskeletal conditions probably are unnecessary.
Reporting in the British Medical Journal in February, researchers from Notting-
Nor are plain radiographs the only overused study in such patients, according to a paper presented at last year’s RSNA and since published.2 Scottish researchers enrolled patients who had been referred to a neurosurgeon or orthopedic surgeon. In 145 patients, there was a question about the need for CT or MRI, and these patients were randomized to receive or not receive that study. Although the specialists were considerably more confident about the correctness of the diagnosis if imaging was performed, they were no more likely to change the diagnosis or treatment plan for these patients than for those who did not have imaging. Fiona J. Gilbert, FRCR, professor of radiology at the University of Aberdeen, who presented the paper in Chicago, pointed out that previous studies of the impact of imaging in low back pain did not include a control group and therefore “may have overestimated the contribution of imaging to clinical decision-making.”
Another paper at the RSNA examined the effect of allowing only specialists in a 100,000-patient managed care practice to order MRI or CT of the knee or shoulder in patients with joint pain.3 There was a 26% decline in the use of MRI and a 23% decline in the use of CT, yet primary care physicians, deprived of these imaging studies, were no more likely than before to refer patients to a specialist. Andrew Litt, MD, of New York University School of Medicine, the author of the paper, suspects that primary care providers order imaging studies because they “just want to do something up front,” not because the results will affect their decision to refer.
1. Kendrick D, Fielding K, Bentley E, Kerslake R, Miller P, Pringle M.? Radiography of the lumbar spine in primary care patients with low back pain: randomised controlled trial. Br Med J. 2001;322:400-405.
Ultrasonography was long thought to have little to offer in orthopedics, but with the introduction of high-resolution equipment, there has been a dramatic change in the thinking about this portable inexpensive modality that does not involve ionizing radiation. Trauma, preoperative evaluation, and longitudinal studies are particular foci of investigation.
Andreas M. Herneth, MD, and his coworkers of the University of Vienna in Austria showed that high-resolution ultrasonography is more sensitive than conventional radiography in the diagnosis of scaphoid fractures after wrist trauma.12 Mariann V. Hammar, MD, and her associates at University Hospital in Uppsala, Sweden, showed that dynamic ultrasonography is useful preoperatively in anterior shoulder instability.13 Takafumi Hayashi, MD, and his colleagues of the Faculty of Dentistry at Niigata University in Japan reported that ultrasonography has a sensitivity of 83%, a specificity of 96%, and an accuracy of 92% in identifying disk displacement in children with asymptomatic temporomandibular joint dysfunction. Those investigators called sonography “ideal” for assessing the TMJ longitudinally.14
A presentation at the Annual Meeting of the American Institute of Ultrasound in Medicine in Orlando, Fla, in June demonstrated the superiority of 3-D ultrasonography for examinations of the shoulder. Nandkumar Rawool, MD, a research associate with the Division of Ultrasound at Thomas Jefferson University in Philadelphia, noted that the 3-D data sets enable rotation of the anatomy or deletion of structures that interfere with an examination. Rawool also sees a role for 3-D ultrasonography in the ankle, especially as it costs $300 to $400, whereas an MRI scan is $1,200. The principal hindrances to wider use of the modality are the limited availability of the high-resolution equipment and the steep learning curve.
Quantitative ultrasonography (QUS) is being explored for the detection and monitoring of osteoporosis. The portable equipment measures attenuation of the ultrasound beam and the speed of sound transmission in ready accessible bones, providing information immediately about bone density. Studies from Germany15 and Denmark16 demonstrated that QUS also is more sensitive than conventional radiography to diagnose early rheumatoid arthritis. The Danish team used QUS and Doppler and spectral ultrasonography to characterize the vascularity and patterns of flow in the synovium. Noting that ultrasonography is safe, reliable, and inexpensive, these researchers suggest that the equipment may soon be common in rheumatology departments.
CT for the ED
The principal role of musculoskeletal CT has been for trauma, although some commentators argue that CT is too expensive for routine emergency department use. CT clearly identifies more injuries than conventional radiography; the critical question is whether these discoveries change patient management.
CM Bach and associates of the University of Innsbruck in Austria argue that CT is seldom necessary in evaluating cervical spinal trauma.17 Although CT was more sensitive than either conventional tomography or plain films alone, a combination of tomography and plain radiography was as accurate as CT except in patients with fractures of the dens.
However, three other studies have endorsed CT as efficient and cost-effective in trauma. Tracy Matheson, MD, of The University of Texas Southwestern Medical Center in Dallas reported at last year’s meeting of the American Roentgen Ray Society that spiral CT imaging can improve the survival of patients who have suffered blunt chest trauma. Almost three-fourths of the patients proved to have injuries not suspected from other imaging studies. Another team, from Emory University, Atlanta, said that two CT scans, one for bone and blood vessels and one for soft tissue, should provide all the information needed to select medical and surgical treatment for chest or pelvic blunt trauma. They used a multislice CT scanner with 2.5-mm and 5-mm collimation and applied reconstruction, postprocessing, and various filters to obtain more information from the data in the days following the patients’ admission. Provided these capabilities are available, the 90-second imaging sequence can save money. William Small, MD, assistant professor of radiology, pointed out that no other imaging was necessary in these patients. Further savings can be achieved if the images help the orthopedic surgeons. “You might be cutting down on length of stay and making the patient’s time in the hospital more productive,” he pointed out.
The third pro-CT study came from the Department of Surgery at Allegheny General Hospital in Pittsburgh,18 which examined 169 blunt trauma patients. Injuries not found on the chest film were detected in 66% of those with chest symptoms and an abnormal chest film and 39% of those with no symptoms and a negative chest film but severe trauma. There was a significant change in the management of 20% of the patients in the first group and 5% of those in the second. Although some of these injuries might have appeared on later chest films, the authors argued it is better to identify and treat them within the “golden hour” after hospital admission.
What the Clinician Wants
Orthopedic imaging has gone far beyond the plain radiograph that was the first study done in radiology. What modality should be used in a particular situation? To answer this question, the musculoskeletal imager must understand exactly what the clinician wants to know. Therefore, the radiologist must be conversant with the physiology, pathophysiology, and function as well as the anatomy. As Frieda Feldman, MD, of Columbia-Presbyterian Medical Center in New York, recently wrote, “‘seeing better’ must be paired with ‘knowing more.'”19
Sugimoto H, Takeda A, Hyodoh K. Early-stage rheumatoid arthritis: prospective study of the effectiveness of MR imaging for diagnosis. Radiology. 2001;216:569-575.
Judith Gunn Bronson, MS, is a contributing writer for Decisions in Axis Imaging News.
- Petersilge CA. MR arthrography for evaluation of the acetabular labrum. Skeletal Radiol. 2001;30:423?430.
- Taoka T, Mayr NA, Lee HJ, et al. Factors influencing visualization of vertebral metastases on MR imaging versus bone scintigraphy. AJR. 2001;176:1525?1530.
- Sugimoto H, Takeda A, Hyodoh K. Early-stage rheumatoid arthritis: prospective study of the effectiveness of MR imaging for diagnosis. Radiology. 2001;216:569?575.
- Lindegaard H, Valle J, H?rslev-Petersen K, Junker P, ?stergaard M. Low field dedicated magnetic resonance imaging in untreated rheumatoid arthritis of recent onset. Ann Rheum Dis. 2001;60:770?776.
- Muramatsu K, Hachiya Y, Morita C. Postoperative magnetic resonance imaging of lumbar disc herniation: comparison of microendoscopic discectomy and Love?s method. Spine. 2001;26:1599?1605.
- Schmitz A, Kandyba J, Koenig R, Jaeger UE, Gieseke J, Schmitt O. A new method of MR total spine imaging for showing the brace effect of scoliosis. J Orthop Sci. 2001;6:316?319.
- Weishaupt D, Wildermuth S, Schmid M, Hilfiker PR, Jodler J, Debatin JF. Virtual MR arthroscopy: new insights into joint morphology. J Magn Reson Imaging. 1999;9:757?760.
- Holder LE, Fogelman I, Collier D. An Atlas of Planar and SPECT Bone Imaging, 2nd ed. London: Martin Dunitz; 2000.
- Moussavian B, Zhuang HM, Ponzo F, Christians MA, Alavi A. FDG-PET for the diagnosis of infections [abstract 161]. Proceedings of the Society of Nuclear Medicine 2001. Reston, Va: SNJ; 2001.
- Stumpe KD, Schiesser M, Kossmann T, Schulthess GK Von. Infection detection with FDG-PET in patients with metallic implants [abstract 162]. Proceedings of the Society of Nuclear Medicine 2001. Reston, Va: SNJ; 2001.
- Kaelicke T, Risse JH, Schmitz A, et al. FDG-PET in diagnosis and follow-up of bone infections [abstract 163]. Proceedings of the Society of Nuclear Medicine 2001. Reston, Va: SNJ; 2001.
- Herneth AM, Siegmeth A, Bader TR. Scaphoid fractures: evaluation with high-spatial-resolution US?initial results. Radiology. 2001;220:231?235.
- Hammar MV, Wintzell GB, ?str?m KGO, Larsson S, Elvin A. Role of US in the preoperative evaluation of patients with anterior shoulder instability. Radiology. 2001;219:29?34.
- Hayashi T, Ito J, Koyama JI, Yamada K. The accuracy of sonography for evaluation of internal derangement of the temporomandibular joint in asymptomatic elementary school children: comparison with MR and CT. Am J Neuroradiol. 2001;22:728?734.
- R?ben P, Barkmann R, Ullrich S, Gause A, Heller M, Gl?er C-C. Assessment of phalangeal bone loss in patients with rheumatoid arthritis by quantitative ultrasound. Ann Rheum Dis. 2001;60:670?677.
- Qvistgaard E, R?gind H, Torp-Pedersen S, Terslev L, Danneskiold-Sams?e B, Bliddal H. Quantitative ultrasonography in rheumatoid arthritis: evaluation of inflammation by Doppler technique. Ann Rheum Dis. 2001;60:690?693.
- Bach CM, Steingruber IE, Peer S, Peer-K?hberger R, Jaschke W, Ogon M. Radiographic evaluation of cervical spine trauma: plain radiography and conventional tomography versus computed tomography. Arch Orthop Trauma Surg. 2001;121: 385?387.
- Omert L, Yeaney WW, Protetch J. Efficacy of thoracic computerized tomography in blunt chest trauma. Am Surg. 2001;67:660?664.
- Feldman F. Musculoskeletal radiology: then and now. Radiology. 2001;216:309?316.