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(Radiology. 2000;216:309-316.)
© RSNA, 2000

Reflections

Musculoskeletal Radiology: Then and Now1

Frieda Feldman, MD

1 From the Department of Radiology, Columbia-Presbyterian Medical Center, 622 W 168th St, New York, NY 10032-3784. Received October 12, 1999; revision requested November 23; revision received December 23; accepted February 21, 2000. Address correspondence to the author.

ABSTRACT

Musculoskeletal radiologists, owing to recent advances in imaging technologies and techniques, are playing an increasingly important role in documenting, diagnosing, and treating an increasing variety of bone and soft-tissue lesions. However, improved visualization of anatomic aberrations—"seeing better"—must be paired with "knowing more," on the basis of complete familiarity with all aspects of the biology, physiology, pathophysiology, and static anatomy of the musculoskeletal system. Only with foreknowledge of the latter can the musculoskeletal radiologist fully maximize the benefits of the former.

Index terms: Bones, CT, 30.1211, 40.1211 • Bones, MR, 30.1214, 40.1214 • Bones, PET, 30.12163, 40.12163 • Bones, radiography, 30.11, 40.11 • Bones, US, 30.1298, 40.12984 • Radiology and radiologists, history • Reflections

"Musculoskeletal Radiology: Then and Now" is a challenging topic, with practitioners—particularly "then" and even "now"—endeavoring to bridge an ever-widening gap between current technologic plenty and previous comparative paucity. Three men and their machines were mainly responsible for our current state of affairs: In the decade between 1970 and 1980, Dr Hounsfield introduced computed tomography (CT), Dr Ter-Pogossian launched positron emission tomography (PET), and Dr Lauterbur presented his initial magnetic resonance (MR) images of fruit. All of these imaging methods eventually replaced our relatively limited armamentarium with a range of improved and enabling technologic choices.

Musculoskeletal radiologists of some 20 years ago knew that there were many ways to approach our particular clinical problems with the aid of several special techniques available in our usually smaller departments. We were all familiar with the diagnostic capabilities of nuclear medicine, ultrasonography (US), and interventional radiology, because we had all been their transient rotating champions during our training, and we remembered how and when to call on them to help identify or confirm one of sometimes several differential diagnoses.

Then along came CT and MR imaging, which changed the pace and promised panaceas. While initially used to image other organ systems, CT and MR imaging soon became requisite tools for investigating musculoskeletal disorders, not solely due to their "high tech" appeal but also to their superior definition of anatomy. Their initial focus on intra- and periarticular abnormalities broadened to provide heightened insights into marrow, muscle, and other soft tissues that, in the past, could not be as clearly or noninvasively achieved. MR images, displayed in any desired orientation and enhanced with selective parameters, ancillary software, and appropriate coils, offered superior spatial resolution and improved soft-tissue contrast.

Nevertheless, the challenge to and the optimum effectiveness of musculoskeletal radiologists, both then and now, remain unchanged. Recognition of anatomic abnormalities in specific settings is an important skill, but it remains equally—and often more—important to appreciate the place of abnormalities in a larger mosaic of which they may be a mere reflection: For example, large synovial popliteal cysts often result from chronic medial meniscal abnormalities, which, if corrected, will result in resolution of the cysts themselves. Not infrequently, therefore, identification and treatment of the causative agent makes its current manifestation disappear. In other words, the greater insight one brings to a problem, the more potentially definitive is its solution. This was true "then," but it is just as or even more important now, when increasingly varied vantage points reveal increasing numbers of previously unappreciated abnormalities earlier and in more detail.

Nevertheless, elegantly displayed "pathology on a silver platter" alone will not suffice. The musculoskeletal radiologist should be completely familiar with all aspects of the biology, physiology, and pathophysiology of an organ system, as well as its static anatomy, to make a maximum contribution.

Technology, no matter how fine, is rendered irrelevant and superfluous if a lack of in-depth knowledge and perspective limit our ability to guide and use it to the best advantage. In fact, some of our older technology remains unsurpassed from a practical, as well as a technical, standpoint. Radiography, in particular, with its superior spatial resolution for fine cortical and trabecular detail, often still serves as the first and only required imaging study. Radionuclide bone scanning, despite its comparatively lower spatial resolution, is still an important modality for evaluating the distribution of lesions (1). Nevertheless, examples abound of current musculoskeletal techniques that facilitate visualization of previously difficult-to-document abnormal anatomy. Many of the following examples from five broad, commonly encountered, but complex and often overlapping categories of disease (traumatic, metabolic, inflammatory, hematologic, neoplastic) carry an inherent lesson: that pathologic changes and diagnoses based solely on images—particularly on MR images—often lack specificity and defy compartmentalization.

Today, acute, nondisplaced, and posttraumatic, as well as insufficiency and stress, fractures can be immediately and definitively diagnosed with the aid of MR imaging (Fig 1). MR imaging is particularly advantageous and cost-effective in elderly emergency room patients with positive physical examination results, nonrevealing radiographs, and other false-negative studies (2). CT, with the heretofore unavailable capabilities of imaging in the transverse plane, multiplanar reconstruction, and excellent cortical and trabecular definition, now allows detection and characterization of the complex geometry of triplane fractures (Fig 2). Transverse images of articular surfaces, in particular, help in selecting surgical candidates, thereby preventing long-range arthritis (3).



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  		Figure 1a. (a) Negative right hip radiograph obtained in a 73-year-old symptomatic man several hours after acute trauma. (b) Normal 2-mm-thick conventional tomograms. (c) Coronal T1-weighted MR image (repetition time msec/echo time msec = 500/30) obtained the same day as a and b reveals an intertrochanteric fracture abutting both femoral neck cortices (arrows).

 


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  		Figure 1b. (a) Negative right hip radiograph obtained in a 73-year-old symptomatic man several hours after acute trauma. (b) Normal 2-mm-thick conventional tomograms. (c) Coronal T1-weighted MR image (repetition time msec/echo time msec = 500/30) obtained the same day as a and b reveals an intertrochanteric fracture abutting both femoral neck cortices (arrows).

 


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  		Figure 1c. (a) Negative right hip radiograph obtained in a 73-year-old symptomatic man several hours after acute trauma. (b) Normal 2-mm-thick conventional tomograms. (c) Coronal T1-weighted MR image (repetition time msec/echo time msec = 500/30) obtained the same day as a and b reveals an intertrochanteric fracture abutting both femoral neck cortices (arrows).

 


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  		Figure 2. Posttraumatic right ankle CT scans in a 15-year-old boy with tibial triplane fracture. Top: Coronal reconstructions reveal three component fracture planes through the epiphysis (e), physis (p), and metaphysis (m). Bottom: Transverse images reveal number, orientation, and degree of separation of weight-bearing plafond fragments.

 
MR imaging subsequently proved to be superior to CT in view of its ability to simultaneously delineate multiple soft-tissue and osseous insults and to provide information as to their acuteness or chronicity. The MR image of a man’s knee in Figure 3a reveals severe derangement of both bone and soft tissue after minor trauma. However, while MR imaging now enables us to render an exquisitely detailed report of the location and type of the existing disrupted anatomy, an underlying cause should be suspected in view of its extent after a stated minor injury. Supplementary radiographs (Fig 3b) were an indispensable contribution in terms of a more effective demonstration of the classic stigmata of hyperparathyroidism; namely, osteopenia, bone resorption, and subtle soft-tissue calcification not appreciated on MR images or by the admitting physician. Radiographs further influenced immediate orthopedic management, as well as subsequent physical rehabilitation. In another patient with a known related metabolic disease, CT scans, to better advantage than MR images, showed massive soft-tissue mineral deposition along with destructive humeral head amyloidomas associated with end-stage renal disease and dialysis (Fig 4).



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  		Figure 3a. Images of the right knee obtained after minor trauma in a man being treated with dialysis. (a) Sagittal T1-weighted spin-echo MR image (500/30) shows an avulsed quadriceps femoris tendon (arrowhead), fractured patella (straight white arrow), lax infrapatellar tendon (curved arrow), and abnormally decreased bone marrow signal intensity (black arrows). A torn patellar retinacula and anteromedial meniscus were also noted. (b) Lateral knee radiograph obtained prior to injury reveals osteopenia, coarsened trabeculae (black arrows), and subtle soft tissue calcification (white arrow). An anteroposterior view (not shown) revealed subperiosteal bone resorption indicative of hyperparathyroidism.

 


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  		Figure 3b. Images of the right knee obtained after minor trauma in a man being treated with dialysis. (a) Sagittal T1-weighted spin-echo MR image (500/30) shows an avulsed quadriceps femoris tendon (arrowhead), fractured patella (straight white arrow), lax infrapatellar tendon (curved arrow), and abnormally decreased bone marrow signal intensity (black arrows). A torn patellar retinacula and anteromedial meniscus were also noted. (b) Lateral knee radiograph obtained prior to injury reveals osteopenia, coarsened trabeculae (black arrows), and subtle soft tissue calcification (white arrow). An anteroposterior view (not shown) revealed subperiosteal bone resorption indicative of hyperparathyroidism.

 


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  		Figure 4. Transverse CT scan in a 46-year-old woman with end-stage renal disease being treated with dialysis confirms the extraarticular location of bilateral tumoral calcinosis (straight arrows) and lytic intraosseous right humeral head amyloidomas (curved arrow).

 
MR imaging also allows detection of previously underestimated, nonvisualized, and often unsuspected soft-tissue insults due to sickle cell disease (Fig 5). While a bone infarct was well documented in the past with bone scans, a muscle infarct with similar clinical symptoms was infrequently considered to be a simultaneous or even a sole offender (4). MR imaging is now the modality of choice for demonstrating muscle damage and for distinguishing its acute (Fig 5a) versus chronic stages (Fig 5b), with or without concomitant bone infarction. Nevertheless, muscle infarction with or without bone involvement is not specific for sickle cell disease. Each may exist alone or together in diverse diseases such as sarcoidosis and Gaucher disease. Muscle infarction alone may also occur after trauma, with diabetes, and in the setting of primary or metastatic soft-tissue tumors.



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  		Figure 5a. Spin-echo MR images of muscle infarction due to sickle cell disease in two patients. (a) Coronal T2-weighted image (2,000/100) in a 33-year-old woman with acutely painful thighs shows linear high signal intensity manifesting as intramuscular streaking (arrows) due to myositis with reactive edema. (b) Transverse T1-weighted image (533/30) of the thighs of a 41-year-old woman shows large, bilateral, curvilinear anterolateral signal voids (long arrows) in sites of prior muscle infarcts. Femora contained erythropoietic marrow (short arrow).

 


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  		Figure 5b. Spin-echo MR images of muscle infarction due to sickle cell disease in two patients. (a) Coronal T2-weighted image (2,000/100) in a 33-year-old woman with acutely painful thighs shows linear high signal intensity manifesting as intramuscular streaking (arrows) due to myositis with reactive edema. (b) Transverse T1-weighted image (533/30) of the thighs of a 41-year-old woman shows large, bilateral, curvilinear anterolateral signal voids (long arrows) in sites of prior muscle infarcts. Femora contained erythropoietic marrow (short arrow).

 
MR imaging has usurped the role of CT for the demonstration of marrow abnormalities. However, MR signal intensities are also nonspecific, even in the face of known disease. Recently introduced diffusion-weighted MR sequences may prove to be useful in this regard, with early results suggesting an ability to distinguish benign from malignant spinal lesions (5).

With the techniques in current clinical use, however, abnormal marrow signal intensities could reflect one or a combination of systemic or neoplastic origins. Osteomalacia per se, osteomalacia associated with hyperparathyroidism, anemia, erythropoietin injection, amyloidosis, leukemia, and myeloma may all show similar focal or widespread marrow changes. Most of the aforementioned metabolic aberrations were, in fact, present in the patients whose images are shown in Figures 6–8. However, the additional findings of avascular necrosis in the femoral head and insufficiency fractures in Figure 6a and 6b and the diffusely diminished marrow signal intensity in Figure 6c due to amyloidosis were all strongly suggestive of end-stage renal disease as the primary cause.



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  		Figure 6a. MR images in two patients with end-stage renal disease being treated with dialysis. (a) Coronal T1-weighted spin-echo image (600/10) in a 67-year-old man after renal transplantation shows bilateral patchy areas of diminished signal intensity in both femoral heads (black arrows), indicative of avascular necrosis. A larger left femoral neck signal void (white arrow) was due to a painful insufficiency fracture. (b) Sagittal T2-weighted fat-saturated fast spin-echo image (2,000/100 [effective]) obtained in the same patient as in a reveals increased signal intensity (arrow) in the femoral head and anteromedial neck. (c) Sagittal gadolinium-enhanced T1-weighted spin-echo image (600/11) of the lumbar spine in a 57-year-old man with chronic renal disease and secondary amyloidosis shows uniformly decreased marrow signal intensity. The large mass (arrows) anterior to and blending with the L4-5 disk represents a focal amyloid deposit. Increased signal intensity of the anterior, partially eroded, apposing end plates is due to reactive edema and inflammation associated with degenerative changes and crystal deposition disease. (Fig 6c courtesy of Gabriela Kaplan, MD, Cleveland, Ohio.)

 


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  		Figure 6b. MR images in two patients with end-stage renal disease being treated with dialysis. (a) Coronal T1-weighted spin-echo image (600/10) in a 67-year-old man after renal transplantation shows bilateral patchy areas of diminished signal intensity in both femoral heads (black arrows), indicative of avascular necrosis. A larger left femoral neck signal void (white arrow) was due to a painful insufficiency fracture. (b) Sagittal T2-weighted fat-saturated fast spin-echo image (2,000/100 [effective]) obtained in the same patient as in a reveals increased signal intensity (arrow) in the femoral head and anteromedial neck. (c) Sagittal gadolinium-enhanced T1-weighted spin-echo image (600/11) of the lumbar spine in a 57-year-old man with chronic renal disease and secondary amyloidosis shows uniformly decreased marrow signal intensity. The large mass (arrows) anterior to and blending with the L4-5 disk represents a focal amyloid deposit. Increased signal intensity of the anterior, partially eroded, apposing end plates is due to reactive edema and inflammation associated with degenerative changes and crystal deposition disease. (Fig 6c courtesy of Gabriela Kaplan, MD, Cleveland, Ohio.)

 


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  		Figure 6c. MR images in two patients with end-stage renal disease being treated with dialysis. (a) Coronal T1-weighted spin-echo image (600/10) in a 67-year-old man after renal transplantation shows bilateral patchy areas of diminished signal intensity in both femoral heads (black arrows), indicative of avascular necrosis. A larger left femoral neck signal void (white arrow) was due to a painful insufficiency fracture. (b) Sagittal T2-weighted fat-saturated fast spin-echo image (2,000/100 [effective]) obtained in the same patient as in a reveals increased signal intensity (arrow) in the femoral head and anteromedial neck. (c) Sagittal gadolinium-enhanced T1-weighted spin-echo image (600/11) of the lumbar spine in a 57-year-old man with chronic renal disease and secondary amyloidosis shows uniformly decreased marrow signal intensity. The large mass (arrows) anterior to and blending with the L4-5 disk represents a focal amyloid deposit. Increased signal intensity of the anterior, partially eroded, apposing end plates is due to reactive edema and inflammation associated with degenerative changes and crystal deposition disease. (Fig 6c courtesy of Gabriela Kaplan, MD, Cleveland, Ohio.)

 


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  		Figure 7a. Images in a 50-year-old woman with end-stage dialysis-treated renal disease and neck pain. (a) Sagittal T1-weighted spin-echo MR image (550/20) of the cervical spine shows normal marrow signal intensity with subluxation, irregularity, and disorganization of the C4 through C7 articulations and an anterior soft-tissue mass (arrows) impinging on the C4 to T1 cortices. (b) Sagittal T2-weighted fat-saturated fast spin-echo MR image (2,000/90 [effective]) shows increased signal intensity (arrows) in a prevertebral soft-tissue mass; this finding represented a conglomerate of apatite crystals. (c) Lateral radiograph of the cervical spine obtained 21 months after a shows that deformities remain unchanged from those seen on a radiograph (not shown) obtained prior to MR imaging.

 


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  		Figure 7b. Images in a 50-year-old woman with end-stage dialysis-treated renal disease and neck pain. (a) Sagittal T1-weighted spin-echo MR image (550/20) of the cervical spine shows normal marrow signal intensity with subluxation, irregularity, and disorganization of the C4 through C7 articulations and an anterior soft-tissue mass (arrows) impinging on the C4 to T1 cortices. (b) Sagittal T2-weighted fat-saturated fast spin-echo MR image (2,000/90 [effective]) shows increased signal intensity (arrows) in a prevertebral soft-tissue mass; this finding represented a conglomerate of apatite crystals. (c) Lateral radiograph of the cervical spine obtained 21 months after a shows that deformities remain unchanged from those seen on a radiograph (not shown) obtained prior to MR imaging.

 


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  		Figure 7c. Images in a 50-year-old woman with end-stage dialysis-treated renal disease and neck pain. (a) Sagittal T1-weighted spin-echo MR image (550/20) of the cervical spine shows normal marrow signal intensity with subluxation, irregularity, and disorganization of the C4 through C7 articulations and an anterior soft-tissue mass (arrows) impinging on the C4 to T1 cortices. (b) Sagittal T2-weighted fat-saturated fast spin-echo MR image (2,000/90 [effective]) shows increased signal intensity (arrows) in a prevertebral soft-tissue mass; this finding represented a conglomerate of apatite crystals. (c) Lateral radiograph of the cervical spine obtained 21 months after a shows that deformities remain unchanged from those seen on a radiograph (not shown) obtained prior to MR imaging.

 


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  		Figure 8. Oblique coronal T2-weighted fat-saturated fast spin-echo MR image (2,000/60) of the right shoulder of a 51-year-old woman with end-stage renal disease. A diagnosis of complete rotator cuff tear (white arrow), bursitis (black arrow), and synovitis was established. The unsuspected cause, dialysis-related arthropathy, was subsequently identified on radiographs (not shown).

 
The cervical spine (Fig 7) and shoulder (Fig 8) MR images in similarly affected patients being treated with dialysis further reflect the common presence of soft-tissue crystal deposition and the potential for error that the presence of such deposition plays in the interpretation of MR studies. Lacking a history of trauma to explain the spinal disorganization, surgery to evacuate an "abscess" diagnosed on MR images (Fig 7) instead revealed a conglomerate of apatite crystals. Multiple prior radiographs indicative of dialysis arthropathy were not consulted. Another MR imaging–based diagnosis of complete rotator cuff tear, bursitis, and synovitis was shown at surgery to be anatomically and physiologically accurate (Fig 8). However, synovial biopsy results implicated iron, hemosiderin, and crystal deposition as causative agents. Typical changes of renal osteodystrophy, hyperparathyroidism, and calcium pyrophosphate dihydrate crystal deposition were evident on radiographs in both patients in Figures 7 and 8. End-stage renal disease, along with other metabolic and rheumatoid-like diseases, are "great imitators" of primary traumatic, inflammatory, hematologic, and systemic abnormalities. Any or all of the aforementioned may be the cause of overlapping marrow signal intensity changes and may additionally mimic the sequelae of uncomplicated posttraumatic changes on MR images that are due to the inherent soft-tissue fragility of muscles, capsules, ligaments, and tendons.

These cases illustrate how new technology has helped hone diagnostic accuracy by superbly depicting local anatomic abnormalities. However, although discernment and data regarding the latter have been vastly expanded and improved because of CT and MR imaging, their impact can potentially be more clinically cogent if an associated underlying origin can be implicated. Many abnormalities documented with MR imaging, as illustrated, may be overlapping and cannot be accurately distinguished without complementary radiographs, which, unfortunately, are beginning to be regarded as "superfluous" by some practitioners. By enhancing our ability to render a "more than meets the eye" multifaceted diagnosis, radiographs, in conjunction with CT scans or MR images, can, in many instances, augment the clinical relevance of our contribution.

Newer techniques have also beneficially affected the care and outcome in patients with musculoskeletal abnormalities. While MR imaging cannot be used to specifically determine bone or soft-tissue tumor histologic features, it has been useful for defining, more accurately than radiography or CT, the extent of such tumors and their proximity to neighboring anatomic structures. MR angiography further enhances this capability by helping clarify a tumor’s relationship to vital vascular structures (Fig 9) by taking advantage of varying signal intensities of flowing blood, which in turn are dependent on flow dynamics and newer imaging sequences (6). Functional MR imaging to measure indices of blood flow and perfusion has also been successfully applied for the diagnosis of musculoskeletal neoplasms (7–11) and holds promise for further expansion.



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  		Figure 9. Oblique gadolinium-enhanced volumetric gradient-echo MR angiographic image (5.9/1.2, 45° flip angle) of the right leg of a 61-year-old man reveals narrowing and anterior displacement of the tibial peroneal trunk and posterior tibial and peroneal arteries due to encasement by a centrally necrotic (arrowhead) vascular spindle cell sarcoma. Note feeding vessels (arrow) arising from the posterior tibial and proximal peroneal arteries and invasion of neighboring muscles. (Image courtesy of Rola Saouaf, MD, Department of Radiology, Columbia-Presbyterian Medical Center, New York, NY.)

 
More recent developments, including MR spectroscopy and PET, offer new and previously unavailable insights into the chemistry and metabolism of tumors before and after treatment. While initially used for investigating central nervous system disease, MR spectroscopy and PET are now being applied in a variety of neoplastic and nonneoplastic conditions (12–14). The ability of PET to characterize the benign or malignant nature of osseous and soft-tissue neoplasms involving the musculoskeletal system (Fig 10) is a topic of ongoing investigation (12,15,16).



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  		Figure 10a. PET scans of sarcoma in the left thigh and a normal right thigh, obtained after intravenous injection of 2-[fluorine-18]fluoro-2-deoxy-D-glucose. (a) Coronal and (b) transverse views reveal a large soft-tissue mass in the left thigh, with peripherally increased tracer uptake (red) in viable tumor tissue and photopenia (blue) of a central necrotic zone. No abnormal concentration was present in the right thigh (arrow), legs, pelvis, abdomen, or chest.

 


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  		Figure 10b. PET scans of sarcoma in the left thigh and a normal right thigh, obtained after intravenous injection of 2-[fluorine-18]fluoro-2-deoxy-D-glucose. (a) Coronal and (b) transverse views reveal a large soft-tissue mass in the left thigh, with peripherally increased tracer uptake (red) in viable tumor tissue and photopenia (blue) of a central necrotic zone. No abnormal concentration was present in the right thigh (arrow), legs, pelvis, abdomen, or chest.

 
Delineation of joint cartilage abnormalities has been another relatively recent area of investigation. Radiographs, although still used for initial imaging of joint abnormalities, are insensitive to cartilage changes. MR imaging has replaced arthrography, CT arthrography, and US for depicting cartilage, with varying levels of success that depend on the degree of involvement and the joint studied (17,18). More recently, the development of high-field-strength magnets promises improved detail with the goal of defining, treating, and preventing cartilage damage (Wu E, oral communication, 1999) (Fig 11). The utility of high-field-strength magnets as pathophysiologic, noninvasive, three-dimensional MR microscopic aids may eventually obviate the acquisition of frozen-sections and conventional histologic staining techniques requiring tissue dessication (19,20) (Fig 12).



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  		Figure 11. Sagittal three-dimensional gradient-echo MR image (400/15) of the knee obtained at 4.2 T shows the normal laminar anatomy of posterior femoral hyaline cartilage, which is represented by three zones: hypointense superficial, hyperintense intermediate, and heterogeneous deep laminar. Markedly denuded anterior subchondral bone due to cartilage degeneration (arrow) is also visible.

 


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  		Figure 12. Three-dimensional spin-echo MR image (1,000/40, 0.7-mm section thickness) obtained at 4.2 T of a bovine bone reveals architectural elements with microscopic-type detail. (Image courtesy of Ed Wu, PhD, Hatch Nuclear Magnetic Resonance Center, Columbia-Presbyterian Medical Center, New York, NY.)

 
Kinematic CT with slip-ring technology is being used to document the influence of patellar tracking on chondromalacia and degenerative joint disease (21). CT data have also been used to design individualized hip prostheses by using computer-assisted design and computer-assisted manufacture in cases with complex anatomy or deformities (22). CT and MR imaging provide pseudo–three-dimensional or holographic true three-dimensional displays and free-standing models of vessels, muscles, and bones for preoperative viewing and planning. Data obtained from standard CT and MR images may soon be used to implement efforts toward virtual arthroscopy, as is already the case in the gastrointestinal tract and chest (23).

Digital radiography has improved the delineation of bone structure and the demonstration of the degree of mineralization, which, along with quantitative CT, dual-photon absorptiometry, and, most recently, high-field-strength MR imaging (Wu E, oral communication, 1999) provide musculoskeletal radiologists with a new role in preventive medicine, with bone densitometry aiding the diagnosis and treatment of osteoporosis (23,24). Computerized microtomography, or so-called noninvasive bone biopsy, which uses monoenergetic synchrotron radiation with 5-mm-thick iliac crest specimens to generate three-dimensional models of trabecular structure and osteoclastic resorption, promises to be useful for quantifying the degrees of osteoporosis and monitoring the effects of treatment. The results obtained with this modality have raised new questions about trabecular connectivity and plate thickness, which may be as important as mineral content in identifying high-risk patients (25).

US, although operator dependent, has attracted recent interest due to its increasingly detailed images of intramuscular and intratendinous structures (26) (Fig 13). Power Doppler US has been used in recent years to demonstrate hyperemia in the rotator cuff and biceps tendon (27) and may play an increasing role in documenting soft-tissue abnormalities around the shoulder, as well as other musculoskeletal sites. In experienced hands, power Doppler US is claimed to be at least as sensitive and specific as MR imaging, in certain instances. Its ability to help differentiate hypervascular or hyperemic structures from fluid may play an increasing role in distinguishing, for example, chronic tendonopathy from acute tendinitis and rotator cuff tears (Fig 14).



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  		Figure 13. Longitudinal US scan of normal forearm muscles obtained with a 7.5-MHz transducer and 32-dB dynamic range (Ellegra; Siemens Medical Systems, Erlangen, Germany) shows parallel hypoechoic muscle fasciculi bordered by echogenic perimysial septa. (Image courtesy of Nancy Budorick, MD, Department of Radiology, Columbia-Presbyterian Medical Center, New York, NY.)

 


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  		Figure 14. Longitudinally oriented power Doppler US scan of the supraspinatus tendon obtained with a high-frequency (9-MHz) linear transducer shows abnormal soft tissue within the subdeltoid (SD) bursa, which shows hyperemia suggestive of acute bursitis. (Image courtesy of Ronald S. Adler, MD, Hospital for Special Surgery, New York, NY.)

 
MR imaging performed with routine clinical parameters is only able to demonstrate coarse intramuscular structure and poorer detail within small tendons. Intravenous and intraarticular injections of a variety of contrast agents aim to improve definition and distinction of a variety of lesions, normal variants, and postoperative changes (10,11).

Currently, musculoskeletal radiologists are performing new interventional and therapeutic procedures. Redesigned US, CT, and open-configuration MR units have simplified both access to lesions and the performance of interventional and therapeutic procedures (28,29). Instruments and catheters monitored with real-time "sighted supervision" can be placed precisely into previously nonvisualized or inaccessible sites for biopsy, injection, and aspiration of numerous musculoskeletal abnormalities for tissue analysis and pain relief (30,31). CT-guided percutaneous radio-frequency coagulation of tumorlike lesions (eg, osteoid osteomas [32]), sclerosis by means of injection of bone cysts (Fig 15), and percutaneous osteoplasty with synthetic materials such as methyl methacrylate have afforded pain relief and improved compressive strength of lytic pelvic, limb, and spinal lesions (Fig 16) (Hoang DD, oral communication, 1999; 33). Radioactive synovectomy performed by musculoskeletal radiologists using phosphorous 32 chromic phosphate has helped prevent or retard joint destruction, improve motion, and decrease intraarticular bleeding (34,35). Resultant benefits include improved accuracy with reduced morbidity, mortality, and cost.



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  		Figure 15a. (a) Anteroposterior radiograph shows posttraumatic fracture (arrow) of a diametaphyseal unicameral bone cyst in left humerus of an 8-year-old boy. (b) Anteroposterior radiograph obtained 7 months after percutaneous injection of methylprednisolone acetate shows progressive healing of the large lytic lesion.

 


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  		Figure 15b. (a) Anteroposterior radiograph shows posttraumatic fracture (arrow) of a diametaphyseal unicameral bone cyst in left humerus of an 8-year-old boy. (b) Anteroposterior radiograph obtained 7 months after percutaneous injection of methylprednisolone acetate shows progressive healing of the large lytic lesion.

 


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  		Figure 16a. (a) Lateral radiograph of a painful pathologic T8 fracture (arrow) in a 59-year-old woman who had undergone chemotherapy and radiation therapy for non-Hodgkin lymphoma. (b) Lateral fluoroscopic view of percutaneous vertebroplasty with methyl methacrylate. Symptoms dramatically improved after injection, allowing cane-assisted ambulation. (Images courtesy of Hoang D. Duong, MD, Columbia-Presbyterian Interventional Radiology Center, New York, NY.)

 


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  		Figure 16b. (a) Lateral radiograph of a painful pathologic T8 fracture (arrow) in a 59-year-old woman who had undergone chemotherapy and radiation therapy for non-Hodgkin lymphoma. (b) Lateral fluoroscopic view of percutaneous vertebroplasty with methyl methacrylate. Symptoms dramatically improved after injection, allowing cane-assisted ambulation. (Images courtesy of Hoang D. Duong, MD, Columbia-Presbyterian Interventional Radiology Center, New York, NY.)

 
The aforementioned examples attest to the considerable ingenuity, time, and effort that have been justifiably committed to the creation of the new imaging modalities. Judging from past experience, however, new technology fast becomes obsolete, as does subspecialization based on particular machines or instruments (36,37). Diagnoses and treatment are not solely based on imaging. Physical examination results, history, laboratory findings, and appreciation of the natural histories and complications of musculoskeletal abnormalities continue to be vital in decisions regarding patient care.

Nevertheless, the musculoskeletal radiologist’s role has changed. It includes not only an understanding of complex physical principles to ensure the optimum performance of current technology, but also an ability to select from the myriad technologies available to achieve a desired goal: namely, informed use to produce informed analysis, which in turn is based on previously accumulated knowledge and experience (38,39). The musculoskeletal radiologist must be steeped in the anatomy, physiology, and pharmacology of the musculoskeletal system to optimally guide, counsel, and address the concerns of a variety of referring specialists, as well as the unique concerns of a variety of patients. By being so armed, the musculoskeletal radiologist can more advantageously contribute to the acute care and successful future outcomes of individual patients.

We should not be mere anatomic imagers. We should more often ask why, when, and what. Why and when did this happen? What was the underlying cause? Did the injury, if any, explain the anatomic result? Do the symptoms explain the visualized abnormality? Often we are satisfied with an accurate diagnosis made apparent by and based on the results of an undeniably superb technique, but it may, nevertheless, be a "superficial" one-dimensional diagnosis. More often than not, so-called older technology (radiography) can help suggest or supply reasons for well-visualized abnormalities.

Musculoskeletal radiology is flourishing. I always knew "then" that "bones are beautiful," but it is more easily apparent "now." Will the ever increasing number of newer modalities become indispensable? Will current demand for our special imaging capabilities continue? They will only insofar as we imbue those same images with insightful, informed, and clinically relevant interpretations that contribute to the enhancement of patient care and the quality of life.

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