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Joint Bone Spine 73 (2006) 527–531

Original article

* CE

1297doi:1

Extrasynovial ultrasound abnormalities in the psoriatic finger.

Prospective comparative power-doppler study versus rheumatoid arthritis

Bernard Fournié a,*, Nathalie Margarit-Coll a, Thibaud Lalande Champetier de Ribes b,Laurent Zabraniecki a, Anne Jouan a, Véronique Vincent a, Hélène Chiavassa b, Nicolas Sans b,

Jean-Jacques Railhac b

a Service de Clinique de Rhumatologie, CHU de Purpan, TSA 40031, 31059 Toulouse cedex 9, Franceb Service d’Imagerie Médicale, CHU de Purpan, TSA 40031, 31059 Toulouse cedex 9, France

Received 16 May 2005; accepted 18 January 2006Available online 19 April 2006

Abstract

We prospectively compared power Doppler ultrasound findings in 25 fingers with rheumatoid arthritis (RA) and 25 fingers with psoriaticarthritis (PsA). Erosive synovitis and tenosynovitis were seen in both groups. Extrasynovial changes were found in 21/24 (84%) fingers with PsAversus none of the fingers with RA. Of the 21 PsA fingers exhibiting extrasynovial changes, 15 (15/25, 60%) also had synovial changes. Theextrasynovial changes reflected enthesitis or soft tissue inflammation, with the main patterns being capsular enthesophyte, juxtaarticular periostealreaction, enthesopathy at the site of deep flexor tendon insertion on the distal phalanx, and subcutaneous soft tissue thickening of the finger pador entire finger. In four fingers, ultrasonograhy showed pseudotenosynovitis, an underrecognized abnormality characterized by diffuse inflamma-tion of the digital soft tissues. Pseudotenosynovitis may play a pivotal role in dactylitis (sausage digit), which is defined as diffuse uniformswelling of the entire finger. Our findings suggest that inflammation of the fibrous skeleton of the finger may lead to the clinical and radiologicalfeatures that distinguish PsA from RA of the finger.© 2006 Elsevier Masson SAS. All rights reserved.

Keywords: Ultrasonography; Dactylitis; Psoriatic arthritis; Enthesopathy

1. Introduction

The fingers are common sites of involvement in both rheu-matoid arthritis (RA) and psoriatic arthritis (PsA). The synovialmembrane of the joints and tendon sheaths is affected in bothconditions. Selective involvement of the distal fingers consis-tent with enthesitis, in contrast, occurs in PsA but not in RA [1,2]. We used ultrasonography to look for evidence of fingerenthesitis in PsA, comparatively with RA. Ultrasonography isa simple and noninvasive tool capable of imaging the bonecontours, synovial membrane, tendons, and soft tissues.

2. Methods

We prospectively included 21 patients meeting AmericanCollege of Rheumatology criteria for RA [3] and 20 patientsmeeting Fournié criteria for PsA [4]. In the RA group, therewere 16 women and five men (ratio, 3.2) with a mean age of

orresponding author.-mail address: fournie.b@chu-toulouse.fr (B. Fournié).

-319X/$ - see front matter © 2006 Elsevier Masson SAS. All rights reserved.0.1016/j.jbspin.2006.01.019

52.9 years and mean disease duration of 10.5 years. The PsAgroup comprised nine women and 11 men (ratio, 0.8) with amean age of 42.8 years and mean disease duration of90.3 years. The inclusion criterion was presence of symptomsin one or more fingers, without evidence of local inflammatorydisease other than RA or PsA.

In each patient, radiographs and ultrasonography were ob-tained within 48 hours of the physical examination done atstudy inclusion. The following were recorded during the phy-sical examination: synovitis, tenosynovitis, inflammation of thefinger pads, deformities, motion range limitation, joint mala-lignment, and skin changes. A plain radiograph of the handswas examined for bone and joint abnormalities. All ultrasoundscans were performed by the same experienced radiologistusing a high-frequency 13.5-MHz linear transducer (SiemensSonoline Elegra, Cheshire, CT, USA), a water-filled bag, soft-ware appropriate for imaging the fingers, and an acoustic en-ergy source. The symptomatic finger was compared to theother fingers in each patient. The dorsal, volar, and lateral as-pects of the finger were imaged. Evidence of synovitis, teno-synovitis, erosions, and enthesitis was noted.

B. Fournié et al. / Joint Bone Spine 73 (2006) 527–531528

The objective of the study was to compare ultrasound find-ings in fingers with symptoms of RA versus PsA. Our workinghypothesis was that abnormalities are confined to the synovialmembrane in RA but involve both the synovial membrane andthe entheses in PsA.

3. Results

We studied 25 fingers in the 21 patients with RA (one fin-ger in 18 patients, two in two patients, and three in one patient)and 25 fingers in the 20 patients with PsA (one finger in 15patients and two in five patients) (Table 1).

Synovial abnormalities were consistently seen in the fingerswith RA (Figs. 1 and 2). A close correlation was noted in theRA group between the clinical manifestations and the ultra-sound findings. A positive Doppler signal from foci of synovi-tis was found in eight fingers. Ultrasonography was more sen-sitive than standard radiography for detecting joint erosions,which were located at sites of contact with synovial abnormal-ities: erosions were visualized in four radiologically normaljoints, and nine new erosions were seen. The lesions were lo-cated in the metacarpophalangeal and proximal interphalangealjoints. The distal part of the fingers was spared in most of thepatients with RA (18/21); the only exceptions were two pa-tients with Heberden’s nodes and one patient with advancedRA in whom ultrasonography disclosed synovitis of a distal

Table 1Ultrasound imaging of the fingers in patients with PsA or RA. Comparison of phy

Number of f(25)

Synovitis Physical 19Ultrasound 19

Tenosynovitis Physical 8Ultrasound 4

Joint erosions Radiograph 12Ultrasound 13

Extrasynovial ultrasoundfindings

Periosteal reaction 9Capsular enthesophyte 3Enthesopathy of distal phalanx 4Soft tissue thickening 8Doppler signal from finger pad 2Doppler signal from nail 2Irregular sesamoid bones 2

Fig. 1. RA. Ultrasound image of the dorsal aspect of the finger. Synovitis of theproximal interphalangeal joint with distension, synovial membrane thickening,and joint effusion.

interphalangeal joint. No extrasynovial lesions affecting thejuxtaarticular bone or adjacent soft parts were seen in the pa-tients with RA.

In the group with PsA, synovial abnormalities and joint ero-sions were less common than in the group with RA. Synovitiswith a positive Doppler signal was noted in five fingers. In 14fingers, the physical examination and plain radiographsshowed signs suggestive of PsA, including finger pad inflam-mation (N = 3), erosive arthritis of the distal interphalangealjoint (N = 3), interphalangeal osteolysis (N = 2), interphalan-geal fusion (N = 2), osteoperiostitis of the distal phalanx as partof psoriatic onychopachydermoperiostitis (N = 1), and juxtaar-ticular periostitis (N = 9). Psoriatic lesions were visible on fivefingers (nail changes in all five cases and periungual lesions intwo cases). Ultrasound imaging showed synovial abnormalitiesin four (16%) fingers, both synovial and extrasynovial abnorm-alities in 15 (60%) fingers, and extrasynovial abnormalities insix (24%) fingers. The synovial abnormalities were similar tothose seen in the fingers with RA. Interestingly, of the eightfingers with evidence of tenosynovitis by physical examina-tion, four had no evidence of tenosynovitis by ultrasonography,which instead showed diffuse thickening of the soft tissues(pseudotenosynovitis).

Extrasynovial abnormalities (Figs. 3–6) were as follows, inorder of decreasing frequency:

sical, radiographic, and ultrasonographic findings in the two groups

PsA RAingers Number of joints

(75)Number of fingers(25)

Number of joints(75)

26 25 3227 25 36

1111

14 15 1916 19 28125

Fig. 2. RA. Ultrasound image of the volar aspect of the finger. Tenosynovitis ofthe flexor tendon. Hypoechoic double line along the tendon.

Fig. 3. PsA. Ultrasound image of the volar aspect of the finger. Periostealreaction at a distance from the proximal interphalangeal joint (double arrow).

Fig. 4. PsA. Ultrasound image of the volar aspect of the finger. Bony spicule atthe site of attachment of the capsule of the proximal interphalangeal joint(arrow).

Fig. 5. PsA. Ultrasound image of the volar aspect of the finger. Ossification ofthe distal attachment site of the deep flexor tendon to the base of the distalphalanx (arrow).

Fig. 6. PsA. Ultrasound image of the volar aspect of the finger. Thickening ofthe soft tissues of the distal finger and Doppler signal enhancement indicatingfinger pad inflammation.

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● Juxtaarticular periosteal reaction in 12 fingers, includingfive generating a positive Doppler signal and three not visi-ble on the plain radiographs.

● Soft tissue thickening in eight fingers, which was either dif-fuse or confined to the finger pad, including the four fingerswith pseudotenosynovitis and the three fingers with fingerpad inflammation.

● Fine bony spicules at the capsule attachment site in fivefingers.

● Remodeling of the distal attachment site of the deep flexortendon at the base of the distal phalanx, with hypoechogeni-

city of the end of the tendon and haziness of the adjacentcortex.

● Sesamoid bone unevenness not visible on the plain radio-graphs, in two fingers.

● Positive Doppler signal from the finger pad in two fingers,both with finger pad inflammation (in one case of finger padinflammation, the Doppler signal was negative).

● And positive Doppler signal from the base of the nail in thetwo fingers with periungual psoriatic lesions.

4. Discussion

Ultrasound imaging detected extrasynovial abnormalitiesthat may be specific of PsA of the fingers. In keeping withearlier publications [5–15], we found no extrasynovial abnorm-alities in the fingers with RA. In a study of ultrasound imagingof the distal phalanx in patients with various rheumatic dis-eases, Grassi et al. [16] noted abnormal signals at the site offlexor tendon attachment in patients with PsA. Jevtic et al. [17]used magnetic resonance imaging to study the fingers of 11patients with RA and 13 with PsA. They found extrasynovialinflammatory abnormalities affecting the periarticular soft tis-sues and juxtaarticular fibrous structures in half the patientswith PsA. In contrast, no such finger abnormalities are de-scribed in the reports by Kane et al. [18] of ultrasound findingsin patients with PsA or by Olivieri et al. [19,20] of magneticresonance imaging findings in patients with spondyloarthropa-thies.

In our study, extrasynovial abnormalities were visible in84% of symptomatic fingers. After exclusion of sesamoid boneirregularity, which is difficult to interpret on sonograms, theseabnormalities fell into three categories. Abnormalities denotingenthesitis included juxtaarticular periosteal reaction, capsularenthesophytes, and enthesopathy at the attachment of the deepflexor tendon on the distal phalanx (Fig. 7). The second cate-gory consisted in thickening of the soft tissues, indicating in-flammation. Thickening was either diffuse or confined to thefinger pad (Fig. 7). Psoriatic onychopachydermoperiostitis ofthe great toe reflects regional inflammation of the distal greattoe. In one patient, histological examination disclosed an in-flammatory lymphocytic infiltrate around the blood vessels ofthe subcutaneous tissue in the pad [1]. Similarly, psoriatic in-

Fig. 7. Diagram showing the four extrasynovial ultrasound abnormalities seen in fingers with PsA.

B. Fournié et al. / Joint Bone Spine 73 (2006) 527–531530

volvement of the finger may denote presence of an infiltratethroughout the subcutaneous tissue. The third category is di-rectly related to cutaneous psoriasis. It consists in a Dopplersignal from the base of the nail, which indicates periungualpsoriatic involvement.

The finger contains an abundance of fibers and, therefore, ofentheses. Tubiana and Thomine [21] described a well-devel-oped flexible “fibrous skeleton” that ensures the stability andmobility of the finger segments, anchors the skin to the under-lying structures in areas used for pincer grip, ensures protectionand cushioning of the finger, aligns the tendons and connectsthem to one another, and prevents excessive mobility. This fi-brous skeleton is made up of ligaments, fibrous capsular bands,palmar fasciae, and fibrous sheaths that attach to the bone ordermis. The fibrous scaffolding is particularly well-developedat the tip of the finger, where the flexor tendon, extensor ten-don, and connective tissue septae that support the finger padand nail attach to the distal phalanx and distal interphalangealjoint. Our finding that extrasynovial abnormalities are commonin the psoriatic finger is consistent with these anatomic charac-teristics and with the selective vulnerability of entheses to PsA[22,23]. We previously incriminated digital enthesitis in anumber of manifestations that suggest PsA of the finger, suchas involvement of the distal phalanx and distal interphalangealjoint, the occurrence of osteolysis followed by fusion of theinterphalangeal joints, and presence of a periosteal reactionaround the joint lesions [1,2,4,22].

Pseudotenosynovitis due to diffuse inflammation of the softtissues is an underrecognized ultrasound manifestation of PsAof the finger. We found four cases of pseudotenosynovitis inour study. Pseudotenosynovitis may play a central role in thegenesis of psoriatic dactylitis (sausage digit), which is definedas diffuse inflammation of the finger [24]. Dactylitis does notoccur in patients with RA, in which the inflammation is con-fined to the synovial membrane of the joints and tendonsheaths. Additional inflammation of extrasynovial structures

must be present for dactylitis to occur. This extrasynovial in-flammation may manifest as distal enthesitis, finger pad in-flammation, or pseudotenosynovitis.

5. Conclusion

The findings from this study support the concept that PsA ofthe finger results both in synovial membrane abnormalities thatresemble those seen in RA (erosive synovitis and tenosynovi-tis) and in enthesopathy of the fibrous skeleton of the finger.The involvement of the fibrous skeleton distinguishes clearlyPsA from RA of the finger.

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