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风湿性疾病的肌肉骨骼超声五

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风湿性疾病的肌肉骨骼超声五 Chapter 5 Pathological findings in rheumatic diseases 157 The ability of US to make an accurate evaluation of soft tissue involvement in a wide range of dis- eases of the locomotor system has led to its increas- ing widespread use in the field of rheumatology [1...
风湿性疾病的肌肉骨骼超声五
Chapter 5 Pathological findings in rheumatic diseases 157 The ability of US to make an accurate evaluation of soft tissue involvement in a wide range of dis- eases of the locomotor system has led to its increas- ing widespread use in the field of rheumatology [1-10]. Significant technological progress has been made over the last few years, generating ever more sophisticated and reliable ultrasound machinery. The high resolution is now such that real in vivo histological examination is now possible. The main reason for the relative lack of wide diffusion of its use amongst rheumatologists is that a long training period is necessary in order to acquire full opera- tor independence. Initially, the use of US in rheumatology was limited to the identification of large collections of synovial fluid (popliteal cysts, bursitis) [11]. These collections can be easily identified even with ‘first generation’ US equipment that uses probes with frequencies between 3.5 and 5 MHz. These are, however, inappropriate for the study of superficial soft tissues. With the advent of the ‘sec- ond generation’ US machines, with 7.5 MHz linear probes, US can now explore larger joints. Clinical practice now includes the study of the shoulder, hip and knee has proven useful in the examina- tion of large tendons (Achilles, long head of biceps and patellar tendon). The potential applications of US in rheuma- tology have been further increased with the dawn of the ‘third generation’ US machines, equipped with very high-frequency probes (> 10 MHz). These can reach a spatial resolution of less than a tenth of a millimeter and make it possible to study the finest details of the smaller joints and hand tendons which are involved early on in chronic arthritis. Osteoarthritis. Supra-patellar transverse scan with knee in maximal flexion shows loss of the normal clarity of cartilage layer together with blurring of the superficial margin of the femoral condylar cartilage. f = femur Fig. 5.1 5.1 Osteoarthritis Several sonographic abnormalities may be observed in patients with osteoarthritis. These include changes within cartilage, joint cavity widening resulting from fluid collection with or without syn- ovial proliferation, and osteophytes [12-14]. Changes within cartilage Loss of the thin, sharp contour of the superficial margin of the cartilaginous layer is one of the early features of osteoarthritis. US is exquisitely sensi- tive in detecting structural changes within differ- ent tissues and can reveal fibrillation and cleft for- mation in osteoarthritis (Fig. 5.1) [15]. 158 Musculoskeletal Sonography Increased echogenicity with patchy or diffuse loss of clarity may be seen even in patients with- out any other findings to indicate damage to the cartilage structure. These changes would seem to reflect structural alterations such as fibrillation of cartilage and cleft formation [13]. Particular attention should be paid to distinguish these early findings in osteoarthritis from artifacts caused by inaccurate setting (gain level) or probe posi- tion [16]. A slight increase in cartilage thickness caused by inflammatory edema in the early phases of osteoarthritis has been noted [13]. Variable nar- rowing of the cartilaginous layer is detectable in patients at a more advanced stage of the disease. Cartilage thinning may be focal, or extend along the entire cartilaginous layer (Fig. 5.2). US measurement of femoral condyle articu- lar cartilage thickness could be of practical ben- efit for an early diagnosis of osteoarthritis. Accu- rate quantification of cartilage thickness cannot always be obtained in patients with advanced osteoarthritis because of poor visualization of the cartilage-synovial space interface. Complete cartilage loss can be observed in advanced dis- ease (Fig. 5.3) [12, 13, 17]. Supra-patellar scanning of weight-bearing areas can be difficult in patients with advanced osteoarthritis and/or painful knee, resulting in lim- ited maximal active flexion [15-18]. Diagnostic accuracy in the detection and grading of cartilage abnormalities should be the subject of further research. The knee and the metacarpophalangeal joints are the locations in which US can best demonstrate the various evolutionary phases of cartilage involvement in osteoarthritis. The articular cartilage of the metacarpal head can be evaluated by longitudinal and transverse dorsal scans, with the metacarpophalangeal joint held in maximal active flexion. Standard longitu- dinal dorsal and volar scans may also be useful. Proximal and distal interphalangeal joints are generally evaluated by means of longitudinal and transverse dorsal scans with the finger in a neutral position. US with high frequency probes allows for an in-depth study of these joints, even if only a lim- ited portion of the cartilage can be explored, due to the acoustic barriers (Fig. 5.4 a, b, c) Joint effusion Small to moderate joint effusions are commonly found in patients with osteoarthritis (Figs. 5.5, 5.6, 5.7). Minimal fluid collections that may be missed on clinical examination are easily detect- ed by US. Synovial fluid is usually anechoic. Non- homogeneous echogenicity of synovial fluid and/or echogenic spots with or without acoustic shadowing can be generated by proteinaceous material, cartilage fragments, crystal aggregates and calcified loose bodies. Osteoarthritis.Supra-patellar transverse scan with knee in max- imal flexion demonstrates focal cartilage thinning (arrowhead) and marked irregularity of the subchondral bone. f = femur Fig. 5.2 Osteoarthritis. Supra-patellar transverse scan with knee in maximal flexion shows complete loss of cartilage. f = femur Fig. 5.3 Pathological findings in rheumatic diseases 159Chapter 5 Osteoarthritis. Supra-patellar longitudinal US scan showing widening of the supra-patellar pouch due to synovial fluid (*) and proliferation (+). f = femur; p = upper pole of the patella; t = quadriceps tendon Fig. 5.5 Osteoarthritis. Index finger of the dominant hand. Dorsal lon- gitudinal views.a Distal interphalangeal joint.b Proximal inter- phalangeal joint.c Metacarpophalangeal joint.dp = distal pha- lanx; mp = middle phalanx; pp = proximal phalanx; m = meta- carpal bone; t = extensor tendon; arrowhead = osteophyte Fig. 5.4 a-c a b c Osteoarthritis of the knee. Differ- ent US features of popliteal cysts. a Anechoic with floating echogenic spots. b Areas of synovial prolifer- ation.c Septa and areas of synovial proliferation. d Completely filled by synovial proliferation Fig. 5.6 a-d c d a b 160 Musculoskeletal Sonography Fine particulate debris floating in the synovial fluid is generally observed after long-standing or repeated joint effusions or after intra-articular cor- ticosteroid administration. In patients with asymptomatic Heberden’s nodes, there is usually no detectable joint space widening. Conversely, symptomatic joint involve- ment is frequently associated with variable capsu- lar distension (Fig. 5.8 a, b). Popliteal cysts are a frequent finding in patients with knee osteoarthritis (Fig. 5.6 a-d). US pro- vides structural details about the content of the cyst, its communication with the joint space and possible compression of adjacent vascular struc- tures. Both the size and shape of cysts vary wide- ly, ranging from small (<1 cm) to giant, multi-loc- ulated entities. Synovial proliferation Synovial proliferation in osteoarthritis may display US features similar to those observed in patients with chronic inflammatory arthritis but without the invasive properties of rheumatoid pannus (Fig. 5.7 a, b). Thickened, edematous synovium is fre- quently observed in more severe disease and in patients with recurrent effusions. Osteophytes Osteophytes are easily detected as irregularities of the bone contour. The skyline view of an osteoarthritic joint is characteristic and correlates with conven- tional radiographic changes (Fig. 5.9 a, b). Osteoarthritis of the knee. Later- al longitudinal views of the supra- patellar pouch showing different aspects of synovial proliferation (arrowheads). f = femur Fig. 5.7 a, b a b Heberden’s nodes. Longitudinal dorsal US scan. a Sympto- matic joint. Dorsal subluxation of the distal phalanx with no evidence of joint inflammation. b Symptomatic joint. Joint effusion (*) and osteophytes (arrowheads). dp = distal phalanx; mp = middle phalanx; t = extensor tendon; arrow- head = osteophyte Fig. 5.8 a, b a b Osteophytes in knee osteoarthritis.a Conventional radiogra- phy.b Medial longitudinal US scan showing an osteophyte of the femoral condyle (arrowhead). f = femur; t = tibia Fig. 5.9 a, b a b Pathological findings in rheumatic diseases 161Chapter 5 Erosive osteoarthritis of the distal interphalangeal joint.The arrowhead indicates a bone erosion at the head of the middle pha- lanx depicted both on longitudinal (a) and transverse (b) dorsal sonograms. dp = distal phalanx; mp = middle phalanx Fig. 5.10 a, b a b Erosive osteoarthritis Sonographic findings in patients with erosive osteoarthritis usually combine the aspects of both osteoarthritis (osteophytes and subluxation of the articular surfaces) and inflammatory involvement (joint space widening and intra-articular power Doppler signal) (Fig. 5.10 a, b) [19, 20]. 5.2 Rheumatoid arthritis US in patients with rheumatoid arthritis demon- strates a wide range of anomalies [21-31]. It pro- vides detailed information on the quantity and characteristics of the fluid collection, the presence of synovial proliferation and the integrity of artic- ular cartilage and subchondral bone. Joint effusion Distension of the joint capsule and the increase in volume of synovial fluid are the most common initial US findings. In these embryonic stages of the disease the synovitis is prevalently exudative and the content of the joint space is characterized by its homogenous anechogenicity (Fig. 5.11). Early rheumatoid arthritis. Exu- dative synovitis of the proximal interphalangeal joint of the dom- inant hand. Longitudinal volar scan depicting anechoic joint cav- ity widening (*).mp = middle pha- lanx; pp = proximal phalanx; t = extensor tendon Fig. 5.11 162 Musculoskeletal Sonography US makes it possible to document the presence of even minimal distension of the joint capsule and of intra and peri-articular synovial fluid collec- tion (synovial cysts, bursitis). Synovial proliferation Proliferation of the synovial membrane appears as hypoechoic thickening of the ‘internal capsular wall’ which can be either homogenous or adopt various conformations (villous, polypoid, or bushy appearance) (Fig. 5.12). These appearances can be documented even in early stages of the disease. Synovial hypertrophy should be differentiated from the accumulation of proteinaceous material or leukocytes that are mild- ly echogenic or finely granular with a cloudy appearance that changes upon palpation with the probe over the skin surface. The identification of synovial proliferation in finger joints together with the evaluation of pannus perfusion using power Doppler has heralded the search for pre-erosive changes in rheumatoid arthritis (Fig. 5.13). High- ly vascularized synovial pannus can predict radi- olographic damage in rheumatoid arthritis and therefore the presence of synovial proliferation rep- resents an important element in the classification of early arthritis. Bone erosions Over the last few years, several studies in rheuma- toid arthritis have confirmed that ultrasonography permits accurate and detailed analysis of the anatomical changes induced by the inflammatory process and is more sensitive than conventional X- rays for the detection of bone erosions [24-26]. Rheumatoid arthritis. Proliferative synovitis of the second metacarpophalangeal joint of the dominant hand. Longitu- dinal dorsal scan depicting hyperperfused areas of synovial hypertrophy invading the cartilage layer of the metacarpal head (°). pp = proximal phalanx; m = metacarpal bone; t = extensor tendon Fig. 5.13 Rheumatoid arthritis.Proliferative synovitis of the second metacar- pophalangeal joint of the domi- nant hand. Longitudinal dorsal scan detecting very small areas (less than 1 mm in size) of synovial proliferation (+). pp = proximal phalanx; m = metacarpal bone; t = extensor tendon Fig. 5.12 This higher sensitivity in the detection of ero- sions depends both on the high spatial resolution of the high-frequency transducers and on the pos- sibility of carrying out multiplanar examination (Fig. 5.14 a-d). Bone erosions are viewed on US as an inter- ruption of the sharp hyperechoic bone profile with the wall and the floor, in most cases filled by hyper- perfused synovial pannus. At the level of the metacarpophalangeal joints, US can identify a number of erosions much more frequently than conventional X-ray in patients with early rheumatoid arthritis [26]. The radial aspect of the second metacarpal head and the lateral aspect of the fifth metatarsal head are the anatomical loca- tions where ‘micro-erosions’ in ‘early arthritis’ can Pathological findings in rheumatic diseases 163Chapter 5 be recognized [25]. In both areas longitudinal scans should be integrated with transverse scans both in order to confirm the findings and to ensure explo- ration of a greater surface area of the bone profiles (Figs. 5.14, 5.15). In patients with rheumatoid arthritis the fifth metatarsophalangeal joint is an early target for aggressive synovitis. At this level, US can detect even minimal erosions which are often missed by conventional X-ray. Conventional morphological study should always be integrated with power Doppler study, when seeking to confirm synovitis in an active phase (Fig. 5.16 a-d) [29, 31-35]. Rheumatoid arthritis.Proliferative synovitis of the second metacarpophalangeal joint of the dominant hand. Dorsal longitudinal (a) and transverse (b) scans showing clear signs of synovial proliferation and bone erosion of the metacarpal head (arrowhead). c Intra-articular power Doppler signal. d Conventional radi- ography. pp = proximal phalanx; m = metacarpal bone Fig. 5.14 a-d a b c d 164 Musculoskeletal Sonography Tendon involvement US is particularly useful in the study of tendon involvement in early rheumatoid arthritis, which often accompanies and in some cases precedes evi- dence of the disease at joint level. The range of ten- don change in rheumatoid arthritis is wide and includes distension of the tendon sheath, loss of ‘fibrillar’ echotexture, loss of definition of tendon margins and the partial or complete loss of tendon continuity [36]. US is of very important practical value in the evaluation of finger tendons. Tendon sheath widen- ing is the hallmark of early tendon involvement in rheumatoid arthritis and other conditions charac- terized by synovial inflammation. Several US pat- terns of tendon sheath widening can be character- ized by the extent of the widening, amount of syn- Rheumatoid arthritis.Semi-quan- titative scoring system for intra- articular power Doppler signal. a Grade 0;no intra-articular signal. b Grade 1;single intra-articular sig- nal.c Grade 2;confluent intra-artic- ular signals. d Grade 3; huge amount of intra-articular signals Fig. 5.16 a-d a b c d Rheumatoid arthritis.Proliferative synovitis of the second metacarpophalangeal joint of the dominant hand.Lateral (on the radi- al aspect of the joint) longitudinal (a) and transverse (b) scans showing a large erosion (arrowhead) (maximal distance between the edges of the erosion:4 mm).c,d Using the same scanning planes,power Doppler revealed hyperperfused pannus within the bone erosion. e Conventional radiography. pp = proximal phalanx; m = metacarpal bone Fig. 5.15 a-e a b c d e Pathological findings in rheumatic diseases 165Chapter 5 ovial fluid within the sheath, profile of the tendon sheath, echogenicity of the sheath content and the presence of synovial hypertrophy. The amount of synovial fluid within a widened tendon sheath may vary considerably, ranging from minimal homogeneous widening (difficult to detect if the pressure of the transducer is too high) to dra- matic, balloon-like distension. There is no direct relationship between the extent of tendon sheath widening and clinical symptoms. The profile of a widened tendon sheath can be regular or extremely non-homogeneous with sac- cular or aneurysmal appearance, especially in chronic tenosynovitis. The appearance of sheath content is characteristically anechoic in patients with acute tenosynovitis. Conversely, if synovial fluid is rich in proteinaceous material or has an elevated cellular content, a variable degree of soft echoes can be detected. The use of very high fre- quency transducers allows for the detection of syn- ovial hypertrophy which appears as an irregular thickening of the synovial layer and/or bushy or villous vegetations (Fig. 5.17 a, b) [22]. Analysis of tendon echotexture is one of the fun- damental aims of US examination. Circumscribed abnormalities of the homogenous distribution of the intratendinous connective fibers are the unequivocal expression of anatomical damage medi- ated by the process of chronic inflammation. In the early phases of inflammation the morphological picture is that of ‘tendon erosion’ that can precede a more extended ‘loss of substance’ and evolve into a partial or complete tendon tear (Fig. 5.18 a-e). Rheumatoid arthritis. Proliferative tenosynovitis of the tibialis posterior tendon (tp). Transverse (a) and longitudinal (b) scans showing a tendon sheath filled with pannus (+). ti = tibia Fig. 5.17 a, b a b Rheumatoid arthritis.Wrist pain. Lateral transverse (a, b) and longitudinal (c,d) scans showing active proliferative tenosyn- ovitis of the extensor carpi ulnaris tendon (t) with partial ten- don rupture (arrowheads). e Conventional radiography Fig. 5.18 a-e a b c d e 166 Musculoskeletal Sonography Rheumatoid arthritis.Wrist pain.Lateral transverse (a) and lon- gitudinal (b) scans showing proliferative tenosynovitis of the extensor carpi ulnaris tendon (t) with pannus (+) invading the tendon texture (arrowheads). u = ulna; tr = triquetrum Fig. 5.19 a, b a b Rheumatoid arthritis.Finger flexor tendons.Tenosynovitis and tendon tears.Longitudinal (a) and cross-sectional (b-e) volar scan- ning of the finger flexor tendons (t) at the level of the metacarpophalangeal joint.Tendon tears appear as small anechoic areas (less than 1 millimeter) within tendon echotexture (arrowheads) Fig. 5.20 a-e b a c d e Where ‘tendon erosion’ is suspected, this diag- nosis should always be confirmed by dynamic investigation and comparison with images taken on longitudinal and transverse scans. This is in order to exclude the possibility of artifacts due to altered inclination of the probe rather than a real anatomical alteration. It may be difficult to dif- ferentiate between partial tendon tear and tendon degeneration. The term ‘intrasubstance abnor- mality’ or ‘intrasubstance tear’ is often used to describe irregular areas of very low echogenici- ty within the tendon. More commonly, partial tendon tears appear clearest on transverse views, but the possibility of an artifact should always be kept in mind and the suspicion of a tendon tear on a single field of observation must be ver- ified along contiguous slices with the US beam held perfectly perpendicular to the tendon (Figs. 5.19, 5.20). Inadequate transducer positioning is the most frequent source of false diagnosis of tendon tear. Complete tendon tear is easily detectable especial- ly if tendons with synovial sheaths are involved (empty sheath sign). The edges of the torn tendon are frequently retracted and curled up. Power Doppler studies make it possible to doc- ument hyperemia associated with the phases of active inflammation, also at the level of the tendon. Pathological findings in rheumatic diseases
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