风湿性疾病的肌肉骨骼超声四

Chapter 4 Sonographic and power Doppler semeiotics in musculoskeletal disorders 111 4.1 Cartilage Sonography has great potential for the non-invasive study of hyaline cartilage, as it can depict micro- scopic lesions to be demonstrated with a high spa- tial resolution. The main limit to the sonographic study of articular cartilage is the relatively limited dimensions of acoustic windows available for the visualization of the cartilage surfaces. The most frequent errors in the study of cartilage, especial- ly at knee level, are linked to incorrect examina- tion. The most frequent artifacts come out in supra- patellar panoramic views, as the cartilage profile of the femoral trochlea is not perpendicular to the direction of the US beam. An apparent loss in sharpness of the chondro-synovial margin of the cartilage and an apparent reduction or increase of the cartilage thickness are the main artifacts caused by incorrect technique [2]. Ultrasonography provides rapid and reliable, albeit incomplete, information about the charac- teristics of articular cartilage, without radiation risk or patient discomfort [3-5]. A wide range of cartilaginous changes can be detected in patients with osteoarthritis and chron- ic arthritis. These include: loss of sharpness of the superficial margin, loss of transparency of the car- tilaginous layer, cartilage thinning and subchon- dral bone profile irregularities. Osteoarthritis Cartilage involvement in osteoarthritis ranges from subtle findings to extensive, easily detectable abnormalities [6-8]. Loss of clarity of the cartilage and loss of sharpness of the synovial space-carti- lage interface are clearly evident features even in the absence of other US signs of cartilage damage. The integrity of the synovial space-cartilage inter- face is the main distinguishing feature of healthy subjects, when compared to patients with osteoarthritis (Fig. 4.1). Loss of cartilage trans- parency could reflect pathological changes such as fibrillation of cartilage and cleft formation. Blurred and/or irregular margins together with marked cartilage thinning are the most common US findings in advanced osteoarthritis (Fig. 4.2 a, b). Although standard criteria for assessing US changes in osteoarthritic condylar cartilage are not yet widely accepted, McCune et al. [7] have reported four main abnormalities in patients with knee osteoarthritis that can be regarded as US hall- marks of the disease at different stages. These include loss of cartilage transparency, reduced sharpness of the superficial cartilage margin, increased intensity of the deep cartilage margin and cartilage thinning [8-12]. 112 Musculoskeletal Sonography Osteoarthritis.Transverse (a) and longitudinal (b) supra-patellar US scans of the knee.Marked diffuse thinning (arrowheads) of the cartilage layer of the lateral femoral condyle (f). p = upper pole of the patella Fig. 4.2 a, b a b Osteoarthritis.Transverse (a,b) and longitudinal (c,d) supra-patellar US scans of the knee.a,c Normal cartilage features.b,d Loss of sharp- ness of the superficial margin and circumscribed thinning (arrows) of the cartilage layer of the medial femoral condyle (f) Fig. 4.1 a-d c d a b Sonographic and power Doppler semeiotics in MSKD 113Chapter 4 Rheumatoid arthritis US has much to offer in the study of rheumatoid arthritis in spite of the relative lack of scientific reports on the subject. The main drawbacks to research in this field include the current limited availability of very high resolution probes togeth- er with the lack of standardized US criteria for car- tilage involvement. In rheumatoid patients, US can visualize pre- erosive changes, particularly at the level of the metacarpophalangeal joint, together with loss of the cartilage layer and irregularities of the sub- chondral bone (Figs. 4.4, 4.5) [3, 12]. Osteoarthritis.Transverse view of the femoral trochlea in a patient with patello-femoral involvement shows inhomogeneous echo- genicity and non-uniform thin- ning of the articular cartilage,with conspicuously uneven profile of the osteo-chondral interface Fig. 4.3 Rheumatoid arthritis. Longitudi- nal dorsal scan of a metacar- pophalangeal joint shows prolif- erative synovitis with early erosive changes.Complete loss of the car- tilage layer of the metacarpal head with initial subchondral involve- ment (arrowhead).m = metacarpal head; p = proximal phalanx; t = extensor tendon Fig. 4.5 Rheumatoid arthritis. Longitudinal dorsal scan of a metacar- pophalangeal joint.Severe cartilage damage involving all the cartilage layer of the metacarpal head. Power Doppler tech- nique shows active pannus invading the subchondral bone. m = metacarpal head; p = proximal phalanx Fig. 4.4 114 Musculoskeletal Sonography Gout In patients with long-standing untreated gout, monosodium urate crystal deposition on the sur- face of the articular cartilage results in hypere- choic enhancement of the superficial margin, which can range from the homogeneous thicken- ing of the synovial space-cartilage interface, to areas of focal deposition (Fig. 4.6 a, b). Due to the deposition of monosodium urate crystals, reflectivity of the superficial margin is no longer dependant upon the angle of insonation, and a panoramic visualization of the full synovial space-cartilage interface can be eas- ily ascertained, and the amount of crystal depo- sition estimated. The adherence of monosodium urate crystals to the superficial margin of the articular cartilage can be confirmed by dynamic assessment using active and passive movement of the joint. Chronic gout.Transverse (a) and longitudinal (b) supra-patellar views of the knee demonstrate diffuse urate crystal deposition (arrowheads) on the cartilage surface of the lateral femoral condyle (f). p = upper pole of the patella Fig. 4.6 a, b a b Pyrophosphate arthropathy.Transverse para-patellar view of the knee depicts minimal aggregates of pyrophosphate crys- tals within the femoral cartilage. f = medial femoral condyle; p = patella Fig. 4.7 Pyrophosphate arthropathy In patients with pyrophosphate arthropathy, crys- tals are detectable within the substance of the hya- line cartilage (Fig. 4.7) [11-13]. The sparkling reflec- tivity of pyrophosphate crystals allows for clear depiction of even minimal aggregates within car- tilage. Crystal deposition can be focal or diffuse – leading to the development of a ‘double contour’, which is created by the permeability of the crystal layer, allowing US to penetrate and depict the bone profile beneath. This is typically seen in the articular cartilage of the femoral condyles and should not be confused with meniscal calcification [9].One striking feature of this deposition pattern is the apparent geometric loca- tion of the crystal layer within the middle portion of Sonographic and power Doppler semeiotics in MSKD 115Chapter 4 the articular cartilage,which may help to understand why cartilage is damaged in pyrophosphate arthropa- thy, leading to secondary degenerative changes. Calcific deposits in pyrophosphate arthropathy appear as hyperechoic rounded or amorphous shaped areas and their location within the fibrocar- tilage can be confirmed by dynamic assessment of the joint during real-time scanning.These aggregates can be identified in the menisci of the knee and in the triangular ligament of the wrist. There is close correlation between the appearance of these crystal deposits on X-ray and US (Figs. 4.8 a, b, 4.9 a, b). Pyrophosphate arthropathy. a Longitudinal US scan of the ulnar aspect of the wrist. b X-ray. Calcification of the triangular liga- ment of the carpus (arrowheads) is evident. t = extensor carpi ulnaris tendon; u = ulna; tr = triquetrum Fig. 4.8 a, b a b 116 Musculoskeletal Sonography 4.2 Synovial cavity Ultrasound is a highly sensitive technique for the detection of even minimal fluid collections and it still represents a particularly useful diagnostic tool to quantify fluid and to monitor its evolution. This latest application is considerably helpful in rheumatological therapy because it constitutes a valid method of evaluation of efficacy. The con- siderable sensitivity of the identification of syn- ovial fluid collection, the highly detailed anatom- ical depiction and the real time visualization of tissues make US the ideal imaging technique for interventional guided procedures, such as arthro- centesis. Thanks to US, the aspiration of synovial fluid is even possible even when the joint collec- tion is minimal. Pathologic conditions that can be assessed with- in the synovial cavity with US include hydrarthro- sis, pneumohydrarthrosis, pyarthrosis, hemarthro- sis, lipohemarthrosis, bursitis, tenosynovitis and synovial thickening. US may occasionally detect the presence of syn- ovial ganglia, joint mice and synovial calcification. Intracavitary synovial fluid collection A collection of fluid within the synovial cavity caus- es the swelling of the involved joint. In hydrarthrosis, US shows fluid collection with- in the cavity, which has an anechoic appearance with dorsal acoustic enhancement (Fig. 4.10 a, b). The amount of fluid within the joint is directly proportional to the severity of the synovial inflam- mation and to the capability of the capsular wall to expand. In some cases the anechoic appearance of the fluid collection can be inhomogeneous because of the presence of dot-like echoes scattered within the collection itself [14-16]. This more com- plicated appearance of the collection may depend on the presence of a fibrinous component within the inflammatory exudate, which can be particu- larly abundant in relapsing collections and can be Pyrophosphate arthropathy of the knee joint.a,b US images.c X-ray. Lateral (a) and medial (b) longi- tudinal US scans demonstrate the presence of calcification of both the menisci (arrowheads).f = femur; t = tibia Fig. 4.9 a-c a b c Sonographic and power Doppler semeiotics in MSKD 117Chapter 4 visualized as arranged echogenic and inhomoge- neous clusters, with a scirrhous conformation. Pyarthrosis occurs in bacterial arthritis, which is usually rare in patients with normal immune sys- tems, while it is common in children, in immuno- suppressed patients, in diabetics and in patients on dialysis. In acute infections with joint fluid col- lection, it is necessary to sample the fluid in order to prescribe the most appropriate antibiotic ther- apy. In chronic infections the fluid collection is usu- ally poor and it is often associated with consider- able synovial thickening. In infections the fluid is usually hypoechoic, but it may appear hyperechoic in more superficial joints. In such cases, the syn- ovial hyperemia can be well-depicted with the use of Doppler techniques as a complement to gray scale US [17, 18]. However, it should be kept in mind that synovial hyperemia in bacterial arthritis is not a mandatory finding, because it depends on the patient’s age, on the duration of the infection and on the immune status. Therefore, since there is no certainty in differentiating septic from aseptic inflammation and it is more suitable to perform a biopsy when clinical suspicion is high. Hemarthrosis exhibit a peculiar US pattern that changes with time similar to hematoma. Hemor- rhagic fluid collections are in fact homogeneously echogenic within the first two to three days from onset, due to the presence of a corpuscular con- tent. After the third day, the hemarthrosis shows a progressive reduction in echogenicity due to lytic enzyme release. Eventually, US shows echogenic branches, corresponding to fibrinous clots, cross- ing the anechoic-appearing zone [14, 15]. Occasionally, the post-arthrocentesis follow-up examination demonstrates the presence of pneu- mohydrarthrosis. The presence of gas in the joint cavity produces a highly reflective mist within the anechoic fluid collection, forming an air-fluid level that changes together with the patient’s position. When assessing hydrarthrosis and pneumohy- drarthrosis, color and power Doppler techniques do not demonstrate significant vascular changes [3, 17, 18]. Lipohemarthrosis is easily identified by means of US and it appears as a dual-phase collection, showing a fluid-fluid level. The overlying echogenic fraction corresponds to the lipid content, while the underlying fraction is hemorrhagic.When lipohe- marthrosis is found in a post-traumatic limb, the presence of a joint fracture can be suspected. Synovial thickening Hypertrophic or hyperplasic synovial thickening is a condition found in several long-standing inflammatory arthropathies and it can be the cause of bone and cartilage erosion in the joint. US nowadays can identify inflammatory syn- ovial thickening more accurately than clinical exam- ination, especially when small joints such as the metacarpophalangeal and interphalangeal joints are affected, commonly observed in chronic pol- yarthropathies. Synovial thickening is character- ized by heterogeneous echotexture varying from hypoechoic to hyperechoic, depending on the amount of water contained in the synovial tissue a US scan of medial paracondylar recess.Anechoic reactive fluid collection containing a thin septum (physiological medio-patel- lar plica, arrowheads). b Axial fat suppression sequence magnetic resonance (MR) scan confirms the presence of mediopatellar plica (arrowheads), which appear as low signal bundle within the hyperintense articular fluid collection Fig. 4.10 a, b a b 118 Musculoskeletal Sonography (Figs. 4.11, 4.12). In larger joints, such as the knee, the synovial thickening appears as a succession of irregularly proliferating branches, mildly echoic, jutting out from the synovia into the articular cav- ity; the assessment of synovial pannus is consid- erably easier when associated with a fluid collec- tion because it works as a contrast agent [1, 14-16] (Fig. 4.13). In pigmented villonodular synovitis, the syn- ovial hypertrophy is usually overabundant, made of thick fusiform villi and gross nodules, with a winding outline surrounded by abundant fluid col- lection. A similar appearance can be observed in joints affected by relapsing hemarthrosis in hemo- philic arthropathies. The continual presence of hemorragic effusion irritates the synovial mem- brane and determines the formation of pannus that starts as a simple thickening and then turns into villous hypertrophy. The sonographer should always Longitudinal sonogram of wrist, dorsal side. Patient affected by rheumatoid arthritis. In this case, synovial proliferation (arrowheads) has a hyperechoic appearance Fig. 4.12 Longitudinal US scan of supra-patellar recess showing large amount of anechoic fluid collection with hyperechoic syn- ovial proliferation (*). TQ = quadricipital tendon; F = femur Fig. 4.13 Longitudinal sonogram of wrist, dorsal side in a patient affected by rheumatoid arthritis. Synovial proliferation appears hypoechoic (*). T = extensor tendons Fig. 4.11 Sonographic and power Doppler semeiotics in MSKD 119Chapter 4 Longitudinal US scan of wrist, dorsal side. Patient affected by rheumatoid arthritis.a Gray-scale scan and (b) power Doppler scan.The use of power Doppler allows the amount of synovial proliferation to be assessed more than MR without contrast (spin echo T1 (SET1), short T1 inversion recovery (STIR)) (c, d) or a plain film (e) Fig. 4.14 a-e a b c e d 120 Musculoskeletal Sonography keep in mind that synovial hypertrophy is a non- specific finding and that the differentiation between a non-specific synovitis and a synovial tumor can be very tricky (hemangioma, synovial sarcoma) [14-16]. A fibrinous exudate can make it difficult to detect the thickened synovial membrane con- tour, especially when it is abundant, because it may simulate the US pattern of synovial hyperplasia. In these cases, when fluid and hypertrophic synovia cannot be differentiated it is possible to use dynam- ic and compressive maneuvers. Such a technique allows the fluid to be “squeezed out” from the hypertrophic synovial wall and the differentiation of the two articular contents [1, 14, 16]. When doubt persists with gray-scale US, power and color Doppler techniques can be applied to dif- ferentiate the fluid from the proliferating tissue, with the presence or absence of vascular signals [17-20] (Fig. 4.14 a-e). The role of Doppler techniques for the assess- ment of synovial vascularization in rheumatoid arthritis is very important. In rheumatoid arthritis, the formation of pannus is a crucial event in the pathogenesis of articular degeneration. Neoangio- genesis is an important pathological element in rheumatoid synovitis [21, 22]. Since hypervascu- larization is proportional to the degree of inflam- mation of the synovial pannus, it is fundamental to study and quantify the vascular signals in order to evaluate the aggressiveness of the pannus itself. Power Doppler is able to assess the increased vas- cularization involving synovial hyperplasic tissue and consequently to give information regarding the activity of the synovial pannus [1, 18-20] (Fig. 4.15 a, b). Despite attempts at semiquantitative or quantitative evaluation of the vascularization by means of dedicated software, the technique is lim- ited by the poor reproducibility. Nevertheless, the recent availability of power Doppler techniques in association with the use of contrast agents (Contrast-enhanced Power Doppler – CePD) has allowed a more detailed analysis of the synovial vascularization. It should be considered that the information derived from power Doppler and CePD refer exclusively to the macrovasculature of synovial pannus. Such lim- its have now been overcome by the introduction of new generation contrast agents (SonoVue) that allow quantitative analysis of the synovial microvascularization to be performed by means of gray-scale US (Contrast-enhanced US – CeUS) [23-25] (Fig. 4.16 a-c). Patient with rheumatoid arthritis. a The power Doppler scan shows a high degree of hyperperfusion, an expression of hyperac- tive pannus. b Follow-up during therapy. A significant reduction in flow signal is shown within the pannus (arrows) Fig. 4.15 a, b a b Sonographic and power Doppler semeiotics in MSKD 121Chapter 4 Bursitis Bursae are anatomical entities located near joints (non-communicating bursae) or in direct commu- nication with the joint cavity (communicating bur- sae). The main function of non-communicating bursae, located at the insertional areas of the anchor tendons of several joints, is to reduce the friction between tendon and bone. Communicating bursae, on the other hand, when an abundant intra-articu- lar fluid collection occurs, function by reducing the joint cavity pressure, by expanding and being filled with the fluid coming from the cavity. Bursitis represents the most common bursal pathology and US is the first choice diagnostic technique. Non-communicating bursitis a. Acute traumatic bursitis: affecting several syn- ovial bursae, the bursal expansion follows direct impact or chronic frictional microtrauma. The most commonly involved bursae are the sub- acromial-deltoid bursa, the pre-patellar and deep infra-patellar bursa, the retro-calcaneal and superficialis bursa of the Achilles tendon and the trochanteric bursa. In acute forms, an increase in anechoic fluid within the bursa is observed (a comparison with the controlateral limb may be useful), while the synovial wall keeps its original thickness (Fig. 4.17 a, b). In chronic forms, the fluid often appears hypoe- choic and contains hyperechoic spots consis- tent with microcalcification, and the bursal walls are thickened [26] (Fig. 4.18 a, b). b. Hemorrhagic bursitis: usually following a vio- lent sporting trauma on artificial surfaces and mainly affect the hands and knees. The hem- orrhagic effusion may organize and form adhe- sions or calcifications. Clots and fibrin, appea