radiology for practitioners imaging of musculoskeletal...

RADIOLOGY FOR PRACTITIONERSIMAGING OF MUSCULOSKELETAL DISEASEShttp://www.lebanesemedicaljournal.org/articles/57-1/doc3.pdf

Nabil J. KHOURY1, George Y. EL KHOURY2

INTRODUCTION

In the recent years, advances in imaging have revolution-ized the medical practice. Since the late 1980’s MR imag-ing has become the modality of choice for the assessmentof musculoskeletal disorders. However, with the advance-ment of CT technology through development of multi-detector scanners, CT scan is again gaining grounds in theevaluation of musculoskeletal diseases.

Besides, ultrasound has been slowly but surely gainingstrength as a very useful tool in musculoskeletal imagingin particular for tendon and ligament disorders and toguide interventions. Note however, that radiographsshould be always performed as the primary investigationand remain a cornerstone in imaging.

In the following article we will be addressing somespecific topics that are frequently encountered in the dailyclinical practice outlining the use of different imagingm o d a l i t i e s .

RADIOLOGICALAPPROACH FOR IMAGINGOF PRIMARY BONE TUMORS

In the appropriate clinical setting, patients with primarybone tumors can present with a constellation of symptomsand signs related to the tumor or they can be totallyasymptomatic and the tumor discovered incidentally onimaging studies. Those with symptoms typically complain

of pain, altered function, and a palpable mass or a patho-logic fracture [1]. In clinical practice, a significant numberof malignant bone tumors initially go undiagnosedbecause of low index of suspicion. The problem of underdetection and delayed diagnosis was discussed by Grimerand Sneath [2] and they reported that 22% of malignantbone tumors are initially missed. Of these cases, 58%were inoperable or required amputation, whereas only15% of patients in whom diagnosis was made at the initialpresentation required amputation. Early diagnosis andprompt referral would undoubtedly improve prognosis[ 2 ] .

Reaching a reasonable differential diagnosis or a spe-cific diagnosis is often a complex process which requiresclose cooperation between the orthopaedic oncologist,radiologist and pathologist. When a clinician is confront-ed with a solitary bone lesion, there is a wide variety oflesions that should be considered, but most importantly,nonneoplastic processes should be ruled out first. Lesionsto be considered should include malignant and benigntumors, exuberant callus, stress fracture, infection andsolitary metastasis. Based on the initial differential diag-nosis or specific diagnosis, patient management can takeone of three pathways, depending on how aggressive thelesion appears to be [3]:

1. Lesions that are thought to be benign, stable orregressing in size can be ignored. Examples of such lesionsinclude vertebral hemangioma, bone island (Figures 1a,1b) and non-ossifying fibroma.

2. Lesions that are benign, but can be locally destruc-tive or have a malignant potential should be followed-upwith periodic imaging. Such lesions include enchondroma

Khoury NJ, El Khoury GY. Imaging of muskuloskeletal diseases. J Med Liban 2009 ; 57 (1) : 26-46.

Departments of1Clinical Radiology, American University of Beirut Medical Center, Lebanon;

2Radiology and Orthopaedic Surgery,

University of Iowa Hospitals and Clinics, Iowa City, USA. Corresponding author: Nabil J. Khoury, MD. American University of Beirut Medical Center. Bliss Street. Beirut. Lebanon.e-mail: [email protected]

a b

FI G U R E 1

Incidental finding of a bone islandin the proximal humerus

of a 35-year-old man.

Radiograph (a)and axial CT scan (b)

showing typical sclerotic lesionwith spiculated contour (a r r o w s) .

N. J. KHOURY, G. Y. EL K H O U RY – Imaging of Muskuloskeletal Diseases Lebanese Medical Journal 2009 • Volume 57 (1) 2 7

(Figures 2a, 2b, 2c), fibrous dysplasia and aneurysmalbone cyst.

3. Lesions suspected of being malignant that requirestaging for local spread and distant metastasis. Primarybone sarcomas fall under this group (Figure 3) [3].

Imaging Ap p ro a c hAsystematic approach is required for formulating a shortd i fferential diagnosis or suggesting a specific diagnosis.The approach starts with ruling out normal variants andbenign processes which mimic neoplasm. This is followedby carefully going over a checklist to evaluate solitarybone lesions when a neoplasm is considered. This check-list includes the patient’s age, the location of the lesion,rate of growth or how aggressive the lesion is, tumormatrix, and finally, the type and characteristics of theperiosteal reaction formed around the lesion [3-4].

The significance of knowing the patient’s age hasbeen well emphasized in the literature. The majority of

FI G U R E 31 2 - y e a r-old boy with Ewing’s sarcoma.

Apermeative lesion with sclerotic and lytic components is seeninvolving the proximal tibia. The tumor borders are ill-defined

(wide zone of transition). There is sunburst (a r r o w s) and onion skin(a r r o w h e a d) appearance of the periosteum denoting aggressive lesion.

FIGURE 2Middle-aged man with mid left thigh paina. Radiograph shows a rather

well-defined lytic lesion inthe mid femoral shaft ( arrows).

b. Axial CT scan reveals soft tissuelesion occupying the femoral bonemarrow with tiny centralcalcifications (arrows) compatiblewith cartilaginous lesion. Thediagnosis is that of an enchondroma.However, this lesion is to befollowed-up because of potentialmalignant transformation.

c. Coronal STIR image of both thighs.The tumor is lobulated and of significant increased signalintensity, a finding seen incartilaginous masses. Minimalendosteal scalloping andsurrounding bone marrow edema(arrow) is seen. a

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28 Lebanese Medical Journal 2009 • Volume 57 (1) N. J. KHOURY, G. Y. EL K H O U RY– Imaging of Muskuloskeletal Di s e a s e s

primary bone tumors occur between the second and fourthdecades of life. A lytic bone lesion occurring in a patientabove the age of 50 years should raise the possibility ofmetastasis (Figure 4a) or multiple myeloma (Figure 4b)whereas a lytic lesion in a child raises the possibility ofLangerhans cell histiocytosis [1, 3] (Figure 5).

The anatomic location of the bone lesion providessignificant clues to what the diagnosis might be. It isimportant to determine whether the lesion is epiphyseal,

metaphyseal or diaphyseal. Does it originate from themedullary space, cortex or from the surface of the bone?The most frequent sites for metastasis and multiplemyeloma are the spine, pelvis and ribs i.e. the axial skele-ton. Primary bone tumors such as Ewing’s sarcoma orchondrosarcoma often occur in the pelvis. Chondroblas-tomas are classically located in the unfused epiphysis orapophysis but may present later (Figure 6). Osteoblas-toma has a predilection for occurring in the posterior

a. Lytic breast metastases in the mid humerus of a 55-year-old woman. The lesion(arrows) has ill-defined contours.

b. Multiple myeloma in an elderly male. Multiple punched-out lytic lesions arenoted in the skull.

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FI G U R E 5 . 3 . 5 - y e a r-old boy with left hip limping. There are well-defined lytic lesions (a r r o w s) involving the leftfemoral neck and left iliac bone. In this age-group the findingsare most probably those of Langerhans cell histiocytosis, a diagnosis that was confirmed by iliac bone biopsy.

FIGURE 6. Chondroblastoma in an 18-year-old man. A well-defined lytic lesion involving the epiphysis is present(arrows) with sclerotic contour and minimal internal calcifications.

FIGURE 4


elements of the vertebra (Figure 7). A lytic lesion in the subchondral bone of the knee epiphysis is most likely agiant cell tumor (Figure 8). Lesions of the sternum arealmost always malignant, typically representing metastasiswhereas the vast majority of patellar lesions are benign [3].

Rate of growth of the lesion also known as biologicactivity determines whether the lesion is benign or malig-nant. This can be determined accurately by assessing them a rgin of the lesion. The margin of the lesion is a reflec-tion of the relative aggressiveness of the neoplastic process. A well-defined lesion with or without a scleroticm a rgin (Figure 9) has a narrow zone of transition (be-tween the lesion and the healthy native bone) and isunlikely to be aggressive [5-6].

A lesion with ill-defined margins has a wide zone oftransition and most likely is an aggressive tumor. Lessaggressive lesions are described radiographically as having a geographic pattern of bone destruction whereashighly aggressive lesions often have moth-eaten or

FIGURE 7Osteoblastoma in a 40-year-old man.A large destructive lesion is noted involving the left posteriorelements of an upper thoracic vertebral body with impingement on the spinal canal.

FIGURE 8Giant cell tumor in a 28-year-old man involving the proximalmetaphysis and epiphysis. The lesion is lytic and ratherwell defined (arrows).

FIGURE 9Awell defined lytic lesion with narrow zone of transitionin a 9-year-old girl. The lesion is expansile and involvesthe distal one-third of the radius. Its wall is not calcified.Biopsy proved the presence of non-ossifying fibroma.


permeative patterns of bone destruction [5-6] (Figure 3,Figures 10a, 10b).

One of the most important features that help in catego-rizing a bone lesion is the tumor matrix [7]. The matrix isthe acellular substance produced by the mesenchymalcells in the tumor. Absence of a radiographically discern-

able tumor matrix significantly limits our ability to comeup with a specific diagnosis. Different matrices are pro-duced by different tumors but only the chondroid andosteoid matrices become calcified and, therefore, are ra-diographically identifiable. On radiographs, the chondroidmatrix reveals white dots, rings, c-shaped and popcorn likecalcifications (Figure 11, see also Figure 2b). Such matrixis seen in cartilage forming tumors such as enchondroma,chondroblastoma and chondrosarcoma. Osteoid matrix hasa confluent, cloud like appearance. It is seen in lesionssuch as osteoblastoma, osteosarcoma (Figure 12), myositisossificans and fracture callus [7].

Another defining feature of solitary bone lesions is thetype of periosteal reaction associated with the lesion. T h ecurrent thinking pertaining to the periosteal reactions isshaped by the classic work of Edeiken and his co-workers[8]. Periosteal reactions can be divided into two types:solid or uninterrupted (Figure 13) and interrupted (Figures3 and 14). There are subtypes under these two types. Asolid periosteal reaction is almost always associated with

FIGURE 10. Same patient as in Figure 3.Coronal T1-weighted (a) and sagittal STIR (b) MR images.The tumor is of low signal intensity on T1W and of highand low signal on STIR images. The bone and soft tissueextent is well identified. Cortical destruction is seenon the sagittal images, anteriorly.

a b

FIGURE 11. Chondrosarcoma of the left pubic bonein a 60-year-old man. The lesion (arrows) is lytic and containsrings and dots calcifications.

FIGURE 12. 16-year-old girl with tibial osteosarcoma.The lesion is typically sclerotic denoting osteoid matrix.

FIGURE 13. Solid benign periosteal reaction (arrow) due toa stress fracture of the third metatarsal bone.


a benign lesion. An interrupted periosteal reaction signi-fies an aggressive lesion, and with few exceptions, such asa fulminant infection or a fast-growing aneurysmal bonecyst, it is almost always associated with a malignantt u m o r. Interrupted periosteal reactions are fairly complexand three subtypes have been described. These are thelamellated (or onion skin), sunburst (or spiculated) andamorphous. The lamellated periosteal reaction often pro-

duces a Codman’s triangle (Figure 14). The Codman’s triangle typically occurs where the tumor mass breaks out through the newly formed periosteal layers. T h eC o d m a n ’s triangle is not specific for malignant tumorsalthough most commonly seen in such conditions. It canalso occur with osteomyelitis and fast growing aneurys-mal bone cysts. The sunburst and amorphous periostealreactions are always associated with malignant lesionssuch as Ewing’s sarcomas (Figure 3) [8].

Some radiographic signs are diagnostic of certaintumors and can be very useful in arriving at an accuratediagnosis [3].

Ivory vertebra: This description is applied when theentire vertebra, especially the vertebral body appearsdensely sclerotic on radiography or CTscan. This appear-ance is highly suggestive of blastic metastasis such as inprostate carcinoma (Figure 15).

Corduroy pattern: Denotes the presence of a thickstriated trabecular pattern in the lesion. It is highly sug-gestive of a hemangioma (Figures 16a, 16b).

FIGURE 14

Lamellated periostealreaction (a r r o w s) with Codman’s triangle(a r r o w h e a d) in a 14-year-old girl with osteosarcoma.There is large destructivelesion of the distal femurwith large soft tissue component containingamorphous calcificationsand bone fragments.

FIGURE 15. Metastatic breast cancer. Coronal reconstructedCT scan of the spine showing an ivory vertebra (arrowhead).Blastic metastases are also noted in the rest of the spine.

FI G U R E 1 6 . N i n e - y e a r-old boy with right iliac bone hemangioma.Radiographs (a) and CT scan (b) show thick striation of the bone trabeculae.

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b


The Rind sign: This indicates the presence of a thickcortical margin around the lesion (Figure 17). It denotes a benign, inactive or stable lesion and is often seen inassociation with small arrested foci of fibrous dysplasiatypically located in the femoral neck.

Ground-glass appearance: Is a radiographic metaphorthat describes expansile lesions that are neither lucent norsclerotic, but rather ground glass in density. This appear-ance should raise the possibility of fibrous dysplasia(Figure 17).

The fallen fragment sign: This sign indicates the pres-ence of a pathologic fracture in a simple cyst, typically inthe humerus (Figure 18). To demonstrate this sign, the

radiographic examination should be taken in the uprightposition to allow the fractured fragment to fall down andsettle at the dependent portion of the cyst.

Fluid-fluid levels: These can be detected on MRI andsometimes on a CTexamination. The sign is diagnostic ofaneurysmal bone cyst or telangiectatic osteosarcoma(Figures 19a, 19b) [9].

Once the presumptive diagnosis of a malignant bonetumor is made, local staging should be performed before

FIGURE 17. Fibrous dysplasia involving the left femoral neckand intertrochanteric region. Typical lytic lesion with groundglass appearance and thick peripheral rind is present.

FIGURE 18

Simple bone cystcomplicatedby a fracturewith a fallenbone fragment(arrow).

Figure 19a. Large destructive lesion of the distal femur in a 22-year-old male with

soft tissue component containing bone fragments.b. Axial T2-weighted MR image reveals multiple cystic spaces with fluid-fluid

level (arrow). Biopsy revealed telangiectatic osteosarcoma.a

b


proceeding to a biopsy. All patients with malignant bonetumors should also be studied for distant metastasis, usinga chest CT scan to rule out the presence of pulmonarym e t a s t a s i s .

RADIOLOGICALAPPROACH FOR IMAGINGSOFT TISSUE TUMORS

There are four types of soft-tissue masses that patients canpresent with and they include: malignant soft-tissuetumors, benign soft-tissue tumors, inflammatory lesions,and posttraumatic masses such as myositis ossificansand false aneurysms. Patients with soft-tissue tumorsusually present with painless palpable mass. The pres-ence of a painful mass usually suggests an inflammatoryprocess. Physicians invariably request a radiographicexamination which rarely yields diagnostic information.The next step is usually an MRI which often helps inarriving at a differential diagnosis and occasionally aspecific diagnosis [10-11].

The most common malignant soft tissue tumors aresarcomas and they include malignant fibrous histiocy-toma (MFH), liposarcoma, fibrosarcoma and synovialsarcoma. Among these the MFH is the most common,accounting for about 24% of all soft-tissue sarcomas.Soft-tissue sarcomas are relatively rare, representingabout 1% of all malignant tumors, but they are still abouttwo to three times more common than malignant bonetumors [10-11].

Benign soft-tissue tumors are far more common thansoft-tissue sarcomas. Lipoma, desmoid tumor (aggres-sive fibromatosis), hemangioma and nerve-sheath tumorare the most common benign tumors [12-13].

Soft-tissue tumors are typically solitary, however,some can present as multiple lesions. Lipoma, aggres-sive fibromatosis, neurofibroma and hemangioma can bemultiple.

Certain lesions show a predilection for a specificanatomic location. This is true of epithelioid sarcomawhere more than 40% of epithelioid sarcomas occur inthe hand and wrist [11]. The majority of clear cell sarco-mas occur in close relationship to tendons and ligaments.

Imaging of Soft-Tissue TumorsRadiographs can sometimes reveal a homogeneous lowdensity tumor consistent with fat-containing lesion suchas lipoma. Calcifications and ossifications can also bedetected radiographically. Calcifications are seen inabout one-third of synovial sarcomas (Figure 20).Rounded calcifications or calcified phleboliths are oftenvisible in hemangiomas (Figure 21).

Because of its improved soft-tissue contrast and multi-planar imaging capabilities MRI is currently considered

FIGURE 20. Synovial sarcoma near the knee joint with calcifications detected on CTscan (arrow).

FI G U R E 2 1 . Newborn with large thigh hemangioma. Small rounded calcifications were noted compatible with phleboliths.


the imaging modality of choice for studying soft tissuemasses. One drawback of MRI is its limited ability in pro-viding tissue characterization for the majority of soft-tissue tumors and also its inability to differentiate benignfrom malignant lesions [14]. Soft-tissue tumors should be imaged in at least two orthogonal planes using T1

and T2-weighted sequences. T1-weighted fat-suppressedsequences without and with IV gadolinium administra-tion are also helpful in differentiating solid from cysticmasses or tumor necrosis. Arriving at a specific diagnosisbased on MRI signal characteristics alone can be diff i c u l t .It is also often impossible to tell if a lesion is benign ormalignant. Malignant lesions, however, are typically larg e(> 5 cm), deep and have inhomogeneous signal intensityon MRI [10, 12-13].

There are a small number of soft tissue tumors, mainlybenign tumors, which have characteristic or diagnosticMRI findings and they will be discussed below [10, 12]:

Lipoma: This is by far the most common benign mes-enchymal neoplasm; it is the most commonly encoun-tered soft-tissue tumor on MRI. Lipomas can attain alarge size. On MRI, they have signal characteristicsidentical with subcutaneous fat where they exhibit highsignal intensity on both T1- and T2-weighted images(Figures 22a, 22b). When a lipoma is within a muscle orbetween fascial planes, the diagnosis is almost alwayscorrectly made. With multidetector CT (MDCT) and itsmultiplanar and 3D capabilities, this modality can easilydetect lipomas and delineate their extent. A well differ-entiated liposarcoma can present with MRI and CTfind-ings resembling a lipoma, however, it has heterogenoussignals on MRI and thick septations between its fattylobules.

Liposarcoma: This is the second most common soft-tissue sarcoma accounting for 16-18% of all malignantsoft-tissue tumors [11]. The lesion occurs most com-monly in the extremities, particularly the thigh. The CTand MRI appearance of liposarcoma correlates with theamount of fat in the lesion. Well differentiated liposar-comas contain more fat than less differentiated liposar-comas [11] (Figures 23a, 23b).

Aggressive fibromatosis: This lesion is characterizedby the proliferation of fibrous tissue which can havelocally aggressive behavior [12]. Aggressive fibromato-sis has a tendency to recur after resection. In the limbs,the lesion can be single or multiple. The signal charac-teristics on MRI depend on its content of collagenous

FI G U R E 2 2

Subcutaneous lipomainvolving the shoulderregion posteriorly.Axial T1-weighted (a)and coronal T2-weighted(b) images showinga lesion that has highsignal intensity similar tothe subcutaneous fat.Few thin septationsare noted within it.

FIGURE 23. Low grade liposarcoma involving the posterior thigh.Sagittal T1-weighted image (a) shows a predominantly high signal intensity lesion with areas of low signal (arrow)and few septations. On STIR image (b), the lesion shows lowsignal intensity regions denoting suppressed fat. Howeverthere are several non-fatty areas of high signal (arrows) dueto cellular elements and fluid.

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N. J. KHOURY, G. Y. EL K H O U RY– Imaging of Muskuloskeletal Diseases Lebanese Medical Journal 2009 • Volume 57 (1) 3 5

material. Lesions consisting primarily of acellular colla-gen have low signal intensity on T1- and T2-weightedimages i.e. fibrous material (Figures 24a, 24b). Lesionsrich in cellular elements show low signal intensity on T1-weighted images and bright signals on T2-weightedimages.

Soft tissue hemangiomas: These are common soft tissue tumors representing 7% of all benign tumors. T h e ycan be subcutaneous, intramuscular or intrasynovial.L a rge-vessel (cavernous) hemangiomas have characteris-tic imaging appearance on MRI. On T1-weighted images,the lesion contains areas of increased signal intensitywhich represent fat (Figure 25a). Hemangiomas typicallyshow marked enhancement after gadolinium administra-tion (Figure 25b). On T2-weighted images, the lesionshows high signal intensity (Figure 25c) with sometimes

serpentine or lobular vessels containing central low signalintensity dots which represent high velocity flow voids[ 11-12].

Nerve sheath tumors : Two histologic types are iden-tified in the extremities and these are: benign schwan-noma and neurofibroma. It is often difficult to differen-tiate these two tumors by MRI, but some clinical andimaging signs can be helpful. A schwannoma ofteninvolves the flexor surfaces of the extremities and itgrows eccentrically from the nerve. Neurofibroma canbe solitary or multiple, especially in patients with type 1neurofibromatosis. It typically grows from the center ofthe nerve causing fusiform expansion of the nerve.Neurofibromas grow slowly, but when rapid growth isobserved, malignant degeneration should be considered.On MRI, peripheral nerve sheath tumors show signals

FI G U R E 2 4 . 2 2 - y e a r-old woman with recurrent soft tissue fibromatosis in the left thigh. Coronal T1-weighted image (a) shows the lesionto be isointense to muscles with sheath-like areas of low signal (a r r o w). Coronal T2-weighted image (b) shows the lesion to be ofintermediate to high signal with similar sheath-like areas of low signal intensity corresponding to the most fibrous elements.

FIGURE 25. Soft tissue hemangiomaof the right thigh in a 14-year-old male.

Sagittal T1-weighted image (a) shows an isointensesoft tissue lesion with area of high signal contentcompatible with fat. Following IV gadolinium administration, sagittal T1W image (b) shows intense heterogenous enhancement of the lesion. Axial T2Wimage (c) : the lesion is of high signal with septations.

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that are isointense to skeletal muscle on T1-weightedimages and hyperintense on fluid-sensitive sequences(T2W, STIR images) (Figures 26a, 26b, 26c, 26d, 26e)After gadolinium injection, these tumors show variabledegrees of enhancement [10-12].

Elastofibroma dorsi: This is a slow-growing pseudo-tumor of the soft tissues which typically occurs on theposterolateral aspect of the chest wall in the subscapularregion. On T1- and T2-weighted images, this lesion isnearly isointense with muscle (Figures 27a, 27b).Because of the typical location and MRI signal charac-teristics, a specific diagnosis is almost always made anda biopsy should be avoided.

WHOLE BODY MR IMAGING (WBMRI)

MR imaging has been proven since its early use in the late1 9 8 0 ’s to be very sensitive in detecting bone marrow infil-tration and bone involvement by various disease processesto much better extent than radiographs. The use of W B M R Ias a screening tool for bone marrow infiltration has beenadvocated back in 1997, in particular with the use of turbosequences. WBMRI has indeed proven its efficacy in theassessment of bone metastasis (Figure 28) [15] and multiplemyeloma (Figure 29a, 29b) [16-17]. The sequences usedvary to some degree and include mainly coronal fast short-tau inversion-recovery (STIR), and/or T1-weighted imagesof the head and neck, chest, upper limbs, abdomen, pelvis

FIGURE 26Nerve sheath tumors

a-b. Schwannoma in a 30-year-old womaninvolving the thumbregion.Sagittal T1-weighted (a)and T2-weighted (b) MRimages showinga lobulated soft tissuemass with intermediatesignal on T1W and predominantly highsignal on T2W.

c-d. Ankle neurofibromain a 56-year-old man.Coronal T 1W image (c)shows the lesionto be superficial and isointense to

muscles. Coronal T1W image following IV g a d o l i n i u madministration reveals heterogenous enhancement of thetumor. On sagittal STIR image (e) the tumor is of increasedsignal.

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and thighs. Additional sagittal STIR and/or T1-weighted ofthe spine [17] and axial T1-weighted images of the skull aresometimes performed. Depending on the protocol used, totalscan time ranges from 40 minutes to 1 hr 30 minutes whenmore than coronal views are used. WBMRI is also useful inthe assessment of response to chemotherapy where IVg a d o-linium is sometimes used. The degree of enhancement wasshown to reflect the response to therapy whereby decreasedenhancement is compatible with good response [18].

WHOLE BODY CT SCAN (WBCT)

The advent of multidetector CTscan (MDCT) has result-ed in the increased use of CT scan in the assessmentof musculoskeletal diseases because of the capabili-ties of acquiring very thin cuts, and secondary 2D and3D reconstructed images. CT interpretation using soft tissue or intermediate windows (in addition to thebone window setting) is very useful in detecting

FI G U R E 2 7Bilateral elastofibroma dorsiin a 59-year-old lady.Coronal T1W (a) and sagittal T2W (b) MRimages reveal bilateral softtissue lesions, underneaththe posterolateral musculatureof the chest wall, larger onthe right and isointenseto muscles. The findings arep a t h o g n o m o n i c .

Figure 28. Middle-aged woman with breast cancer and mid back pain. Bone scan was normal (a).WBMRI (b) revealed high signalwithin a mid thoracic vertebral body (arrow). This appeared on CT scan (c) to represent a destructive tumor.

FIGURE 29

Elderly man known to have multiple myeloma

WBMRI using coronal STIR technique shows areas of either diffuse or focalhigh signal involving the thoracic vertebrae (a . arrow & arrowheads) .D i ffuse bilateral femoral and right iliac bone (a r r o w) involvement is also seen (b) .

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intramedullary lesions not causing cortical erosions(Figure 30a).

In the era of total body scanning, WBCT has been recommended in the workup of newly diagnosedpatients with multiple myeloma [19-21], being moresensitive than radiographs. Other authors advocatedhowever the use of Positron Emission Tomography(PET) in combination with CT scan (PET/CT) as the initial workup as well as for follow-up of patients withmultiple myeloma (MM) [17].

A recent research by Horger et al. [22] showedencouraging results for the evaluation of the course ofmedullary lesions of MM at follow-up CT, includingthe assessment of lesion density and size. CT scan is also better than MRI for the assessment of fracturer i s k .

Besides, unpublished data shows a possible promis-ing role of WBCT in detecting bone metastasis. Theadvantage of CT scan is that it assesses at the same timethe chest, abdomen and pelvis for metastatic workup(Figures 30b, 30c).

Published data shows however the important use ofthe integrated PET/CT which has a very high positivepredictive value for bone metastatis and lymphomareaching 98% [23]. PET/CT and MRI have also equalsensitivity in detecting metastasis. In addition, WBCT isvery effective in assessment of polytraumatic patientsfor detection of fractures, injuries to the organs withinthe chest, abdomen and pelvis in addition to evaluatingthe patency of the vascular tree.

SHOULDER PAIN AND ROTATOR CUFF DISEASE

Shoulder pain is a very common clinical presentation and is commonly due to rotator cuff disease (RC). Radio-graphic images are frequently normal in acute settings[24]. However, in cases with chronic symptoms abnormalfindings can be encountered and these include soft tissue

FIGURE 30a. Coronal reconstructed CTscan of the abdomen and pelvis using

intermediate window setting shows previously unsuspected bonemarrow metastases within the proximal shaft of the left femur(a r r o w) in a patient with breast cancer.

b. Coronal reconstructed CTscan of the abdomen and pelvis using bonewindow setting showing the degree of extent of mixed blastic and lytic metastatic bone disease in another patient with breast cancer.

c. Same CT technique as in Fig. b in a young boy with leukemia.The extent of leukemic bone involvement can be well assessed,seen as lytic lesions throughout the spine and pelvic bones. The patient was put in braces.

FIGURE 31. Rotator cuff calcifications (arrow) seen on an APshoulder radiograph.

a b c


calcification over greater tuberosity (Figure 31), acromio-clavicular joint osteoarthritis causing impingement rotatorc u ff tear and superior displacement of the humeral head.

Since its advent, MRI has been proven to be highlyaccurate in detecting RC injuries. It provides informationabout tear dimensions, thickness (partial versus full thick-ness; complete versus incomplete) and tendon retraction.

In addition it helps in assessment of muscle atrophyinformation about coracohumeral arch and cause ofimpingement such as thick coracoacromial ligament andacromioclavicular joint osteoarthritis [25]. This helps indetermining the treatment selection and prognosis [25].

Several sequences may be used. A tear (Figure 32) isseen as very high signal intensity focus within the tendonsubstance which is normally of low signal intensity onall sequences [25]. Muscle atrophy is seen as loss ofmuscle volume and fatty replacement being of high sig-nal on T1-weighted images.

More recently ultrasound (US) has been more fre-quently used in assessment of rotator cuff tendons and

has proven to be a powerful and accurate method fordetection of rotator cuff tear [24, 26]. Ultrasound needsstate-of-the-art machine and operator expertise. On US,tendons appear as homogeneous hyperechoic bands. A tear is seen as hypoechoic area within the substance ofthe tendon (Figure 33a), discontinuity or tendon thin-ning. Ultrasound also assesses the presence of calcifica-tion (Figure 33b), fluid in the subdeltoid subacromialbursa or shoulder joint, muscle atrophy. Tendon degen-eration is seen as inhomogeneity of tendon substance(Figure 33a). Use of dynamic imaging of the shouldercan reveal impingement on the supraspinatous tendonand abnormal humeral head translation.

Moreover, US-guided treatment of RC calcificationshas been advocated percutaneously using fine needle.The technique consists of doing lavage and aspiration ofthe calcification after injecting Lidocaine near the calci-fication; then fragmentation and aspiration of the calcifi-cations is done. The yield of this technique is quite effec-tive in some series [27] (Figures 34a, 34b).

FIGURE 32. Sagittal STIR image in a young man with acuteshoulder pain. There is a large full thickness tear at theinsertion site of the supraspinatous tendon. The tendongap is filled with fluid (arrow).

FIGURE 33. Shoulder ultrasound.a. The supraspinatous tendon is enlarged and heterogenous

(arrows) with several hypoechoic areas compatible withdegeneration and tearing. The middle arrow points toa full thickness tear.

b. Different patient. Supraspinatous tendon calcificationis present (arrow).

FIGURE 34. Ultrasound guided aspiration of rotator cuffcalcifications.a. The needle (a r r o w h e a d s) has its tip abutting the calcification

(a r r o w) .b. Aspirated white calcific material can be identified

within the syringe.

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HIP FRACTURE

Hip fracture is a common traumatic disorder in particu-lar related to motor vehicle accident. However, it hasparticular detection challenges in elderly patients wherethe radiographic changes may be subtle because ofosteopenia (Figure 35a), or because the fractures may benon-displaced or incomplete fractures (Figure 36a). Inaddition, a traumatic event is not frequently elicited.Delay in detection of the fracture has a secondary highmorbidity. Accurate and early detection of the fracturehas been made easy by MRI (Figure 35b) which has ahigher sensitivity then the plain radiographs [28-30].MRI shows bone marrow edema appearing as low signal

on T1W images and high signal on T2W and short-tauinversion recovery (STIR) images. A fracture line is oflow signal on all sequences. Besides, MRI shows otherunsuspected bone and soft tissue injury including pelvicbone fracture or contusions, surrounding muscle contu-sions and muscle and tendon tears [30].

With the advent of multidetector CT (MDCT) with 2Dand 3D reconstructed images, CT scan is showing in-creased detection accuracy when compared to radiogra-phy and to analyzing axial scans alone (Figures 36b, 36c,36d) [31]. But so far no comparative studies between MRIand CT scan were performed. CT can also assess detailsabout fractures pertinent to surgical approach as well asassociated acetabular fractures.

FIGURE 3585-year-old lady with sudden severeright hip pain while walkinga . Radiographs did not reveal definite

fracture except for minimal sclerosisat the level of the right femoralneck (a r r o w) .

b. MRI was then performed. CoronalSTIR images revealed a low signalintensity line (a r r o w h e a d) correspondingto the sclerotic area on the radiographand compatible with old insuff i c i e n c yfracture. There was however a highintensity fracture line (arrow) lateral to it with surrounding bone marrowedema denoting acute fracture not seen on the radiograph. Soft tissue edema seen as high signal was also noted around the right hip.

FI G U R E 3 6 . 6 8 - y e a r-old man with right hip trauma.a. Radiographs show suspicious linear fracture near the lesser trochanter (arrow). CT scan was then performed.b-c. Coronal 2D reconstructed images show an anterior intertrochanteric fracture (arrow in b) extending posteriorly to reach

the greater trochanter (arrow in c).d. Coronal 3D reconstructed image nicely demonstrates the fracture (arrows).

a

a

c

b

d

b

OSTEOPOROSIS, SPINAL FRACTURESAND INTERVENTIONAL PROCEDURES

Primary osteoporosis is defined as skeletal disorder char-acterized by compromise of bone strength with diagnosticcriteria of bone fragility based on measurement of bonemineral density (BMD) and/or presence of fracture. Fourcategories are present depending on the severity of abnor-mal BMD [32]. Osteoporosis is a major public concern andis the main cause of vertebral fracture (85%). For example,in the United States 30 million women and 14 million menare affected. The importance of this disease results fromsignificant increased risk of fracture, the decrease in thequality of life, chronic back pain and limitation of dailyactivities [33]. In addition, the presence of vertebral frac-ture is a sign of increased risk of other fractures in theskeleton (spine, hip). Vertebral fractures are frequentlyundetected by clinicians and under diagnosed by radiolo-gists, rendering the importance of recognizing these frac-tures on imaging. An important note is that unsuspectedosteoporotic fracture may be detected by other imagingstudies performed for other reasons (for example lateralchest X-rays) and hence should be mentioned.

Diagnosis of OsteoporosisThere are several methods to measure bone densitometry.The most commonly used techniques are dual energy X-ray absorptiometry (DEXA) and quantitative comput-erized tomography (QCT) [32]. DEXA utilizes an X-raysource that emits 2 photon beams of different energy andmeasures the differential absorption of energy from thesebeams by tissues. QCT has an advantage to selectivelymeasure the trabecular and cortical parts of the vertebralb o d y. But it is less used because of high radiation, limitedavailability and higher precision error.

Radiographic Diagnosis of FracturesWhen dealing with osteoporotic fracture radiologistsshould not make diagnosis only on the basis of qualita-

tive impressions. They are however encouraged to use asemi-quantitative approach described by Lenchik et al.[33] as seen on the lateral view. In this approach a mildfracture (grade 1) has a 20-25% loss of height; moderatefracture (grade 2) 26–40% loss of height (Figure 37),and severe fracture (grade 3) more than 40% loss ofheight.

Other Imaging TechniquesAlthough well centered plain radiographs are sufficientfor the diagnosis of fracture, multidetector CT (MDCT)with sagittal reconstruction and MRI are very sensitivefor the diagnosis.

MRI on the other hand is an important tool to differ-entiate benign from pathologic vertebral fracture, espe-cially in elderly patients with osteoporosis. Signs ofbenign fracture include mainly normal bone marrow sig-nal (Figure 38a), hypointense fracture line parallel toend-plate with or without bone marrow edema (Figures38a, 38b, 38c), fluid or air within the fractured vertebra,and absence of paravertebral soft tissue mass (Figure38d) [34-35].

FI G U R E 3 7 . O s t e o p o r o t i cfracture. Semi-quantitativemethod of measurement.Lateral radiograph. There is fracture of a midthoracic vertebral body(a r r o w). Measuring theheight between the blackdots of the involved vertebra and the one lowerto it, gives an estimate ofthe loss of height whichis here around 38%(i.e. moderate). There isalso decreased bone densityin keeping with somedegree of osteoporosis.

FI G U R E 3 8 . Benign vertebral fracturesa. Elderly patient with subacute back pain. Sagittal T1-weighted MR image of the thoracic spine.

There are fractures of several vertebral bodies with preserved bone marrow signal compatiblewith benign fractures. Ahypointense line (a r r o w) is noted parallel to the upper endplate of a midthoracic body compatible with fracture typically seen in benign conditions.

b-c. 82-year-old man known to have chronic anemia presenting with acute back pain. SagittalT1-weighted (b) and T2-weighted (c) MR images of the spine showing diffused low intensityon T1-weighted images due to red marrow reconversion. In addition, one vertebral body(arrow) shows a low signal intensity line seen on both sequences similar to that described inFig. a. It is surrounded by bone marrow edema due to acute benign fracture.

d. Sagittal T2-weighted MR image in an elderly patient with vertebral fracture. Fluid (a r r o w h e a d s)is seen within the vertebral body typical for benign fracture.

a b c d


Causes of Back Pain other than OsteoporosisBack pain is the second most common clinical complaintencountered by primary care physicians [36]. There is avery wide spectrum of diseases causing back pain includ-ing degenerative, traumatic, infection/inflammation, neo-plasm both benign and malignant, and conditions relatedto growth disturbances in pediatric population. However,it is beyond the scope of this article to discuss all theseentities. In the radiological evaluation of back pain, initialimaging should always include plain radiographs whichgive an overall assessment in particular for degenerativechange and alignment. MR imaging however has anestablished crucial role in the assessment of diseases caus-ing back pain including degenerative disc disease, tumors,spondylodiscitis, early spondyloarthropathy, tumor extentin particular within the spinal canal and bone marrowinfiltrative processes such as metastasis (Figure 39) andmultiple myeloma (Figure 40). In fact, MRI is the bestimaging modality to assess myeloma. In some instances itwas also proven to be more sensitive than bone scan forthe detection of bone metastasis [37-38].

Intravenous gadolinium is not routinely used for theassessment of back pain. However indications for its useinclude infectious diseases, postoperative spine, in theassessment of response to therapy in multiple myeloma,focal spine tumors and in limited cases of diffuse bonemarrow changes in order to differentiate normal red mar-row from tumor infiltration.

CT scan is helpful in some conditions such as deter-mination of fracture risk in myeloma, extent of spinal

fracture, spondylolysis and in the diagnosis and assess-ment of some tumors such as osteoid osteoma (see alsosection on WBCT).

Vertebroplasty and KyphoplastyDuring the last decade, two new therapeutic procedureswere introduced for the treatment of vertebral osteo-porotic fracture: percutaneous vertebroplasty and kypho-plasty [39]. These techniques have good short-termresults regarding pain relief, functional status, correctingkyphosis and to prevent further rapid collapse. So farhowever, no data is available with regards to long-termresults. Besides osteoporotic fracture, these interven-tions are also used to treat osteolytic metastasis and mul-tiple myeloma causing vertebral collapse.

Te c h n i c a l l y, vertebroplasty (Figures 41a, 41b) con-

FIGURE 39Metastatic lung cancer to the spine.

Sagittal STIR imageshows complete replacement of the bonemarrow of L5 vertebralbody by increased signalintensity with loss ofheight, and retropulsionof the posterior cortex intothe spinal canal (arrow).

F i g u re 40. Elderly patient withmultiple myeloma and spineinvolvement. Sagittal T1Wimage show diffuse punctuatelow signal intensity foci withinthe vertebral bodies ofthe thoracic and lumbar spine.

FIGURE 41. Vertebroplasty of osteoporotic fractures.a. Transpedicular needles are seen at the L1 and L2 collapsed vertebral bodies.b. Post cement injection. There is a slight increase in the height of the treated vertebral bodies.

a b


sists of placing a needle under fluoroscopic control with-in the vertebral body through a transpedicular or postero-lateral approach. Then cement consisting of polymethyl-metacrylate polymer (PMMA) is injected until resistanceis felt by the operator or the cement reaches the posteriorvertebral wall. This results in filling and expansion of thevertebral body. The overall complications are limited andinclude mainly cement leak. Neurological complicationsare rare. The kyphosplasty technique is an evolution ofthe vertebroplasty. It employs balloon catheters inflatedwith contrast agent to restore the morphology of the col-lapsed vertebral body reducing the kyphosis. Then stabi-lization with bone cement injection is done after removalof the balloon (Figures 42a, 42b, 42c).

With both techniques, more than one vertebral levelcan be injected with cement at the same session.

IMAGING OF THE DIABETIC FOOT

Diabetic foot is a broad term used to describe a variety ofclinical problems affecting patients with diabetes mellitus.These problems are the result of vascular insuff i c i e n c y,peripheral neuropathy and foot infections. Vascular disor-ders of the feet typically involve large and medium ves-sels causing atherosclerosis and microangiopathy of theskin and muscles.

Diabetic neuropathy of the foot, also known as Char-

c o t ’s foot or neuropathic joints, can involve the foref o o tproducing metatarsophalangeal and interphalangeal jointdeformities, but is seen more commonly in the midfoot( L i s f r a n c ’s joint) (Figure 43a) and hindfoot (subtalar andankle joints). Fracture-dislocations of the Lisfranc’s jointalong with flattening of the longitudinal arch of the foot arethe most common features of neuropathic arthropathy inthe diabetic foot (Figure 43b). Severe deformity of theankle following a neuropathic fracture is another commonradiographic finding in patients with a diabetic foot.

Probably the most difficult problem in terms of diag-nosis and treatment is that of infections involving the softtissues and the bones in the diabetic foot. Generalized andlocalized factors contribute to foot infections in patientswith diabetes mellitus, including poor blood supply,abnormal sensation, and minor trauma. Soft tissue infec-tions most often start in the toes. Cellulitis and abscessformation are commonly the result of skin infections. Inthe feet of diabetic patients, osteomyelitis is typically achronic infection contiguous with a skin ulcer. Ulcersmost commonly occur on skin areas with high pressure.In the bone, infection starts at the cortex and most patientswith this form of osteomyelitis lack generalized symp-toms. Abscess formation and sinus tracks are common inthe soft tissues of the foot. Diagnosing osteomyelitis in thediabetic foot with imaging techniques has always been achallenge [40]. Radiography and MRI have become the

FIGURE 42. Kyphoplasty of a mild but painful benign fracture of D12 vertebral body.a. Bilateral transpedicular needles with balloons inflation. b. Injected cement after removal of the balloons.

c. The end-result with cement within the confines of the body.

FIGURE 43.Charcot joints of the midfootin two diabetic patients. a . Sagittal T1WMR image

showing significant subchondralbone marrow changes involvingthe first tarso-metatarsal joint(a r r o w) with preservation of thesurrounding soft tissues.

b . Foot radiograph in advancedLisfranc fracture-dislocationinvolving the 2n d to 5t h t a r s o -metatarsal joints.

a

a b

b c


modalities of choice in this regard. Radiography is stillused as the initial examination where findings of osteo-penia and bony erosions are highly suggestive of osteo-myelitis (Figure 44a), but the sensitivity of radiography inthe early stages of osteomyelitis is low and its ability indetecting soft tissue and marrow abnormalities is limited[40-42].

The usefulness of MRI for diagnosing osteomyelitisin patients with diabetic feet has been shown by severalreports, however, the MR findings of osteomyelitis canbe simulated by other pathologic processes affecting thediabetic foot. These include neuropathic osteoarthro-pathy and abnormal biomechanical stresses resultingfrom foot deformity. This makes the interpretation ofsignal abnormalities in the marrow difficult and oftenequivocal. Another confounding factor relates to the fact that many diabetic patients referred for imaging of their feet for osteomyelitis have underlying neuro-pathic bone changes which can resemble osteomyelitison MRI [41].

To improve specificity of MRI some authors haveclassified the MR findings in osteomyelitis of the diabet-ic foot into two groups: 1) primary MR criteria, and 2) secondary criteria. The primary MR criteria includedecreased marrow signal intensity on T1-weighted images(Figure 44b), increased marrow signals on T2- w e i g h t e dimages, and marrow enhancement after intravenous injec-tion of gadolinium. Craig et al. [43] have stressed thatsuch abnormal signals in the marrow should be intenseand confluent in order to make the diagnosis of osteo-myelitis with confidence. Other authors have shown thatfaintly dark signals or reticular non-confluent dark signalson T1-weighted images often do not represent osteo-myelitis [42].

The importance of the secondary criteria lies inimproving the specificity of the primary findings. T h e s e

have been recently highlighted by some investigators [40-41]. They include: an adjacent soft tissue fluid collec-tion, i.e. an abscess (Figure 44c), a sinus tract (Figure44d), subcutaneous fat edema, cutaneous ulcer and corti-cal interruption.

The MR findings in Charcot’s arthropathy of the footshould be distinguished from those of infection and theyinclude: preservation of normal subcutaneous fat, absenceof soft tissue fluid collections, presence of subchondralcysts and intraarticular loose bodies (Figure 43a).

MUSCULOSKELETAL ULTRASOUND

With the technical advances, ultrasound has been play-ing an important role in the assessment of various mus-culoskeletal (MSK) diseases. When compared to MRI,the advantages of ultrasound (US) include: lower cost,better availability, better acceptance by patients, and nocontraindication to its use. In addition, it has real timecapability, so it can be used as a dynamic study [44].

It is evident from the literature that US is a cost-effec-tive tool for focal problem solving issues and in guidinginterventions. Although US cannot replace MRI in manyindications (e.g. bone marrow disease, bone tumors) itshould be the first line imaging modality for other indi-cations such as rotator cuff diseases. The main indica-tions for US include tendon disease mainly at the levelof the shoulder and ankle (Figures 33a, 33b; Figure 45)[45-46], ligament injuries (e.g. ankle) [47], joint effu-sions (e.g. knee, hips, ankle), superficial foreign bodies[48], assessment of small joints for inflammatory arthro-pathy [49]. Ultrasound may be used also as an adjunct toMRI in the assessment of muscle injury and superficialMSK masses (e.g. Morton neuroma) (Figure 46).

It is important to know that to obtain best results withultrasound, there is a need for state-of-the-art equipment

FIGURE 44Diabetic foot infections

a - b . Osteomyelitis and septic arthritisinvolving the first metatarso-phalangealjoint (a r r o w). Radiograph (a) revealssignificant destruction of the joint.Sagittal T1WMR image (b) showingsignificant abnormal bone marrow signalat the level of the metatarsal head andbase of the proximal phalanx with bonedestruction. There is significantoverlying soft tissue edema.

c . D i fferent patient with 1s t m e t a t a r s o -phalangeal infection. There is an adjacentsoft tissue abscess (a r r o w) seen onthis axial T1-fat saturation MR imagefollowing IV gadolinium administration.Presence of fluid collection with thickrim enhancement is diagnostic of abscess.

d. Another patient with similar infection.Sagittal STIR image shows edema involving the 1s t metatarsal head (M) and base of the proximal phalanx (P). Asmall sinus tract(a r r o w) extends from the level of the joint to the skin of the plantar aspect of the foot. Joint effusion is also present (a r r o w h e a d).

a b

c d

N. J. KHOURY, G. Y. EL K H O U RY– Imaging of Muskuloskeletal Diseases Lebanese Medical Journal 2009 • Volume 57 (1) 4 5

and optimal examinations should be performed by expe-rienced operators.

Besides, ultrasound can be used as guidance for inter-ventions such as injections in tendon sheath, subdeltoidsubaccromial bursa, joint or cyst aspiration, biopsy ofsuperficial lesions and treatment of rotator cuff calcifi-cations (Figure 34a).

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