Patients with RA who had undergone MRI of the wrist or hand joints were selected for inclusion in this study through a retrospective review of medical records. All patients fulfilled the 2010 American College of Rheumatoid Arthritis classification criteria [18]. A total of 43 patients were enrolled. All patients had received MRI of one wrist. In addition, 36 patients had MCP joint MR images taken, and three patients had received additional MRI of the contralateral wrist and MCP joints. Basic demographic information was obtained for all patients, including their age, gender, disease duration, and treatment prior to the MRI scan. The patients’ laboratory parameters at the time of the MRI scan, including their immunoglobulin M (IgM) rheumatoid factor (RF), anti- cyclic citrullinated peptides antibody (anti-CCP Ab), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) levels, were also collected. This study was approved by the Institutional Review Board for Human Research, Konkuk University Medical Center (KUH 1010815). The informed consent was waived under the IRB authority.

The first-through-to-fifth MCP joints and the wrist of the most painful side—or of the dominant side in cases of equally severe symptoms on both sides—were scanned. The MRI was performed using a 3.0T Impact MRI unit (Skyra, Siemens, Erlangen, Germany) with a dual phased array wrist coil. All the MRI examinations (of the wrists and MCP joints) were carried out with T1-weighted echo and T2-weighted fat suppression sequences without intravenous contrast. The T1 coronal scanning measures were as follows: (1) repetition time (TR) = 600 msec, echo time (TE) = 10 msec, flip angle = 137°; (2) number of excitations (NEX) = 1; (3) field of view (FOV) = 192 × 220 mm; (4) matrix = 450 frequency, 310 phase; and (5) slice thickness = 2 mm, interslice gap = 2 mm. The T2 coronal scanning measures with fat suppression were as follows: (1) TR = 3,010 msec, TE = 55 msec, flip angle = 145°; (2) NEX = 1; (3) FOV = 220 × 220 mm; (4) matrix = 448 frequency, 358 phase; and (5) slice thickness = 2 mm, interslice gap = 2 mm. The T1 axial scanning measures were as follows: (1) TR = 640 msec, TE = 13 msec, flip angle = 134°; (2) NEX = 1; (3) FOV = 121 × 130 mm; (4) matrix = 510 frequency, 380 phase; and (5) slice thickness = 4 mm, interslice gap = 6 mm. The T2 axial scanning measures were as follows: (1) TR = 3,700 msec, TE = 56 msec, flip angle = 150°; (2) NEX = 1; (3) FOV = 121 × 129 mm; (4) matrix = 380 frequency, 250 phase; and (5) slice thickness = 4 mm, interslice gap = 6 mm.

The MR images were evaluated for bone erosion, bone edema, synovitis, and tenosynovitis in consensus by one board certified radiologist and one experienced rheumatologist who were blinded to other clinical information.

The MRI was assessed for the presence/absence and the semiquantitative scores of bone erosion, bone marrow edema, and synovitis according to the OMERACT RAMRIS without contrast injection (Fig. 1A and 1B). The sites included for scoring based on the hand MR images were: the first-through-to-fifth MCP joints, the carpal bones, the distal radius, the distal ulnar, and the radiocarpal, intercarpal, carpometacarpal (CMC), and distal radio-ulnar joints. MRI-detected bone erosion is a sharply marginated bone lesion with correct juxta- articular localization and typical signal characteristics that is visible on two planes, with observation of a cortical break on at least one plane. The bone erosions were scored on a scale of 0 to 10 based on the proportion of eroded bone to the assessed bone volume as judged from all available images, as follows: 0, no erosion; 1, 1% to 10% of bone eroded; 2, 11% to 20% of bone eroded, etc. MRI-detected BME is a lesion in the trabecular bone with ill-defined margins and signal characteristics consistent with increased water content. The BME scale ranged from 0 to 3 and was used to rate the proportion of bone with edema as follows: 0, no edema; 1, 1% to 33% of edematous bone; 2, 34% to 66% of edematous bone; 3, 67% to 100% of edematous bone. Synovitis presents as an area in the synovial compartment that shows an increased signal on T2-weighted fat-suppressed images and a thickness greater than the width of the normal synovium. It was assessed as being present or absent without being graded in 4 wrist regions—the distal radioulnar joint, the radiocarpal joint, the intercarpal joint, and the CMC joint—and in each MCP joint. The MRI-detected tenosynovitis was evaluated as described by Haavardsholm et al. [10]. In MRI, tenosynovitis is visualized as tendon sheath fluid, sheath thickening, and an increased signal on T2-weighted fat-suppressed images. A total of 10 separate anatomical areas of the wrist were assessed for tenosynovitis: the six extensor compartments and four regions on the volar side, namely, the flexor carpi ulnaris, the ulnar bursa including the flexor digitorum profundus and superficialis (FDP/FDS), the flexor pollicis longus in the radial bursa, and the flexor carpi radialis (FCR) (Fig. 1C and 1D).

All statistical analyses were performed with the IBM SPSS version 23.0 (IBM Co., Armonk, NY, USA). The continuous variables were expressed as mean ± standard deviation, and the categorical variables were presented as frequencies and proportions. The results were compared with Pearson chi-square test, Fisher exact test, a chi-square test for trend, ant the Mann Whitney U test or Kruskal-Wallis test as appropriate. A logistic regression analysis was used to control the treatment and disease duration variables associated with MRI-detected abnormalities. A p value < 0.05 was considered significant.

The baseline characteristics of the patients are presented in Table 1. The distributed patterns of bone erosion, BME, synovitis, and tenosynovitis on the MR images were compared between the patients with SPRA and those with SNRA. The patients with SPRA showed longer disease durations than those with SNRA (26.4 ± 29.0 months vs. 13.7 ± 12.5 months, p = 0.044). No difference was observed in the ESR, CRP, and prior treatment of RA of the two groups of patients.

A total of 78.3% and 69.6% of RA patients presented bone erosion and BME at the wrist, respectively. The carpal bones were more frequently affected by bone erosion and BME than the metacarpal or phalangeal bones that compose the MCP joints. The capitate bone was most frequently affected by erosion, followed by the lunate, the triquetrum, the hamate, and the distal radius. BME was most frequent in the 2nd phalangeal base, followed by the lunate, the capitate, the triquetrum, the hamate, and the trapezoid (Fig. 2A). Carpal bone lesions caused by erosion with BME were most frequent in the capitate, followed by the lunate, the triquetrum, the scaphoid, the trapezoid, and the distal radius (data not shown). A total of 34.2% and 29.0% of RA patients had bone erosion and BME at the MCP joint, respectively. In the MCP joints, the 2nd phalangeal base was the most commonly affected by bone erosion and BME, followed by the 2nd, 3rd, and 4th metacarpal heads (data not shown). The results were similar in treatment-naïve RA patients (n = 12). The capitate bone was the bone most frequently affected by erosion and BME, followed by the lunate and the hamate.

For the bone erosion, the average sum scores of the unilateral wrist joints and second to fifth joints were 10.5 and 2.1, respectively. The corresponding values for the BME were 5.3 and 1.5, respectively. The capitate also had the highest RA-MRI bone erosion score, followed by the lunate, the triquetrum, the hamate, the distal ulna, and the radius, whereas the 2nd phalangeal base had the highest RA-MRI BME score, followed by the lunate, the capitate, the 4th metacarpal base, and the triquetrum (Fig. 2B).

The analysis according to the seropositivity status showed that at least one location scored positive for bone erosion in 68.8% of SPRA patients and in 100% of SNRA patients, while the corresponding values for BME were 68.8% and 74.4%, respectively. After controlling for the disease duration and treatment received, there were no differences between the RA-MRI scoring patterns and the bone erosion and BME between SPRA and SNRA patients.

A total of 80.4% of patients presented synovitis at the wrist. The carpal joints were more affected by synovitis than the MCP joints. Synovitis was most frequently detected in the intercarpal joint, followed by the radiocarpal, radioulnar, and CMC joints. Among the MCP joints, the 2nd MCP joint was the most frequently affected, followed by the 3rd, 4th, and 5th MCP joints. Although this is not included in the OMERACT RAMRIS, RA-associated synovitis was also found in 12.8% of the patients’ 1st MCP joints (Fig. 3).

At least one location scored positive for synovitis in 81.4% of SPRA patients and in 92.9% of SNRA patients. After controlling for the disease duration and treatment received, there was no difference in the RA-MRI synovitis scoring patterns of the SPRA and SNRA patients.

A total of 78.3% of patients had tenosynovitis around the wrists; 56.5% had tenosynovitis of the flexor tendons, while 52.2% presented it at the extensor tendons, and 32.6% had both. The FDP/FDS were most frequently affected (43.5%), followed by the tendons of extensor compartments 4, 2, and 6 (Fig. 4A). The results were similar in treatment-naïve RA patients. The FDP/FDS was most frequently affected, followed by the FCR and the tendons of the extensor compartment 2.

Although there was no difference in terms of synovitis, bone erosion, and BME between the SPRA and SNRA patients, those with SNRA had more tenosynovitis than those with SPRA. At least one location scored positive for tenosynovitis in 92.9% of SNRA patients, which represented a higher prevalence than in SPRA patients (71.9%). After controlling for the disease duration and treatment received, SNRA patients also showed significantly more inflammation in both extensor tendons, particularly in the wrist extensor compartments 3 and 4 (78.6%, 35.7%, and 50.0%; p = 0.04, p = 0.04, and p = 0.03, respectively) (Fig. 4B).