Proliferative Tenosynovitis In Digit Of Dogs

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Erosive osteoarthritis of the distal interphalangeal joint.The arrowhead indicates a bone erosion at the head of the middle phalanx depicted both on longitudinal (a) and transverse (b) dorsal sonograms. dp = distal phalanx; mp = middle phalanx

5.2 Rheumatoid arthritis

US in patients with rheumatoid arthritis demonstrates a wide range of anomalies [21-31]. It provides detailed information on the quantity and characteristics of the fluid collection, the presence of synovial proliferation and the integrity of articular 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. Exudative synovitis of the proximal interphalangeal joint of the dominant hand. Longitudinal volar scan depicting anechoic joint cavity widening (*). mp = middle phalanx; pp = proximal phalanx; t = extensor tendon
Proliferative Tenosynovitis

Rheumatoid arthritis. Proliferative synovitis of the second metacarpophalangeal joint of the dominant hand. Longitudinal 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

US makes it possible to document the presence of even minimal distension of the joint capsule and of intra and peri-articular synovial fluid collection (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 mildly 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). Highly vascularized synovial pannus can predict radi-olographic damage in rheumatoid arthritis and therefore the presence of synovial proliferation represents an important element in the classification of early arthritis.

Bone erosions

Over the last few years, several studies in rheumatoid 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. Longitudinal 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

This higher sensitivity in the detection of erosions depends both on the high spatial resolution of the high-frequency transducers and on the possibility of carrying out multiplanar examination (Fig. 5.14 a-d).

Bone erosions are viewed on US as an interruption 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 locations where 'micro-erosions' in 'early arthritis' can

Proliferative Tenosynovitis
Rheumatoid arthritis. Proliferative synovitis of the second metacarpophalangeal joint of the dominant 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
Proliferative Tenosynovitis
Fig. S.14 a-d

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 radiography. pp = proximal phalanx; m = metacarpal bone be recognized [25]. In both areas longitudinal scans should be integrated with transverse scans both in order to confirm the findings and to ensure exploration 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 Active Erosion

Rheumatoid arthritis. Proliferative synovitis of the second metacarpophalangeal joint of the dominant hand. Lateral (on the radial 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

Rheumatoid arthritis. Proliferative synovitis of the second metacarpophalangeal joint of the dominant hand. Lateral (on the radial 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 a a

Rheumatoid arthritis. Semi-quantitative scoring system for intraarticular power Doppler signal. a Grade 0; no intra-articular signal. b Grade 1; single intra-articular signal. c Grade 2;confluent intra-artic-ular signals. d Grade 3; huge amount of intra-articular signals

Rheumatoid arthritis. Semi-quantitative scoring system for intraarticular power Doppler signal. a Grade 0; no intra-articular signal. b Grade 1; single intra-articular signal. c Grade 2;confluent intra-artic-ular signals. d Grade 3; huge amount of intra-articular signals

Tendon involvement

US is particularly useful in the study of tendon involvement in early rheumatoid arthritis, which often accompanies and in some cases precedes evidence of the disease at joint level. The range of tendon 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 widening is the hallmark of early tendon involvement in rheumatoid arthritis and other conditions characterized by synovial inflammation. Several US patterns of tendon sheath widening can be characterized by the extent of the widening, amount of syn-

Doppler Activity Tenosynovitis

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

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

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 dramatic, 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 frequency transducers allows for the detection of synovial 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 fundamental aims of US examination. Circumscribed abnormalities of the homogenous distribution of the intratendinous connective fibers are the unequivocal expression of anatomical damage mediated 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).

Doppler Activity Tenosynovitis

Rheumatoid arthritis.Wrist pain. Lateral transverse (a, b) and longitudinal (c, d) scans showing active proliferative tenosynovitis of the extensor carpi ulnaris tendon (t) with partial tendon rupture (arrowheads). e Conventional radiography

Rheumatoid arthritis.Wrist pain. Lateral transverse (a, b) and longitudinal (c, d) scans showing active proliferative tenosynovitis of the extensor carpi ulnaris tendon (t) with partial tendon rupture (arrowheads). e Conventional radiography

Where 'tendon erosion' is suspected, this diagnosis 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 differentiate between partial tendon tear and tendon degeneration. The term 'intrasubstance abnormality' or 'intrasubstance tear' is often used to describe irregular areas of very low echogenicity 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 verified 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 especially 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 document hyperemia associated with the phases of active inflammation, also at the level of the tendon.

Rheumatoid arthritis.Wrist pain. Lateral transverse (a) and longitudinal (b) scans showing proliferative tenosynovitis of the extensor carpi ulnaris tendon (t) with pannus (+) invading the tendon texture (arrowheads). u = ulna; tr = triquetrum

Rheumatoid arthritis.Wrist pain. Lateral transverse (a) and longitudinal (b) scans showing proliferative tenosynovitis of the extensor carpi ulnaris tendon (t) with pannus (+) invading the tendon texture (arrowheads). u = ulna; tr = triquetrum

Rheumatoid arthritis. Finger flexor tendons.Tenosynovitis and tendon tears. Longitudinal (a) and cross-sectional (b-e) volar scanning 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)

Doppler Activity Tenosynovitis

Rheumatoid arthritis.Shoulder pain.Transverse (a) and longitudinal (b) anterior scans at the bicipital groove.Proliferative subdeltoid bursitis and tenosynovitis of the long head of biceps tendon (f). h = humerus; d = deltoid

Bursitis

Finally, ultrasonography allows clear documentation of involvement of synovial bursae in rheumatoid arthritis. A significant increase in the volume of synovial fluid makes the bursa, which quite often contain signs of synovial hypertrophy, easily visible (Fig. 5.21).

5.3 Seronegative spondylarthritis

The US imagery present in psoriatic arthritis is similar to that seen in rheumatoid arthritis.

Distal interphalangeal involvement can be accurately documented with probes of frequencies greater than 10 MHz. Distension of the joint capsule is easily detected together with edema of the periarticular soft tissues (Fig. 5.22).

US can distinguish between soft tissue swelling and the presence of bony swelling in a Heberden node [19].

The 'sausage' finger, which is a common finding in psoriatic arthritis, is characterized by the following US features [37,38]:

1. distension of the flexor sheath;

2. distension of the joint capsule of the proximal interphalangeal joints;

3. edema along the entire thickness of the soft tissues.

The presence of tenosynovitis has been confirmed frequently in the 'sausage' finger, but in some cases may be entirely absent (Fig. 5.23).

Involvement of tendons without a synovial sheath (Achilles tendon, patellar tendon), together with pathology located at the enthesis and aponeurosis, can have a wide range of characteristic US features [39-45].Achilles tendonitis is characterized by thickening of the tendon that can adopt a fusiform appearance and show hypoechogenici-ty secondary to edema. In addition, peritendinitis (hypoechogenicity at the level of the peritenon) and edema of soft tissues can co-exist (Fig. 5.24). The detection of distension of the deep retrocal-caneal bursa is particularly common.

Enthesitis can be depicted in all stages of its evolution by US. In the early stages, the bone profile shows no significant change whilst the area of the enthesis and the adjacent portion of the tendon show hypoechogenicity. In more advanced phases, discontinuity of the bone profile at the point of insertion is more clearly depicted and can evolve into wide areas of re-absorption (Fig. 5.25).

As enthesitis advances even further, entheso-phytes can be identified with a characteristic posterior acoustic cone of shadow. In the plantar fascia,

Psoriatic arthritis. Distal interphalangeal joint.Dorsal longitudinal scan showing joint cavity widening and clear signs of synovial proliferation (+). dp = distal phalanx; mp = middle phalanx; t = extensor tendon

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