European Journal of Radiology 69 (2009) 331–338 Intra-articular distribution pattern after ultrasound-guided injections in wrist joints of patients with rheumatoid arthritis Mikael Boesen a,∗ , Karl Erik Jensen b,1 , Søren Torp-Pedersen a , Marco A. Cimmino c,2 , Bente Danneskiold-Samsøe a , Henning Bliddal a a The Parker Institute, Frederiksberg Hospital, Nordre Fasanvej 57, 2000 Frederiksberg, Copenhagen, Denmark b State Hospital, Department of Radiology, MRI Division, Copenhagen, Denmark c Rheumatologic Clinic, Department of Internal Medicine, University of Genoa, Italy Received 26 June 2007; received in revised form 16 August 2007; accepted 31 August 2007 Abstract Objective: To investigate the distribution of an ultrasound-guided intra-articular (IA) injection in the wrist joint of patients with rheumatoid arthritis (RA). Methods: An ultrasound-guided IA drug injection into the wrist joint was performed in 17 patients with 1 ml methylprednisolone (40 mg/ml), 0.5 ml Lidocaine® (5 mg/ml) and 0.15 ml gadolinium (Omniscan 0.5 mmol/ml). The drug solution was placed in the central proximal part of the wrist between the distal radius and the lunate bone. Coronal and axial MRI sequences were performed after the injection to visualize the distribution. Carpal distribution (radio-carpal, inter-carpal, and carpo-metacarpal) as well as radio-ulnar distribution was recorded. Full distribution in one compartment was given the value 1, partial distribution 0.5 and no distribution 0. A sum of the total distribution for all four compartments was calculated and correlated to the clinical parameters and the MRI OMERACT scores. Results: No uniform pattern was seen in the distribution of the contrast. Only two patients had full contrast distribution to all four compartments, and the mean distribution count for all patients was 2.4 (range 0.5–4). The distribution count correlated with the MRI OMERACT synovitis score (r = 0.60, p = 0.014), but not with the erosions, bonemarrow oedema scores or any clinical parameters. Conclusion: The distribution of contrast on MRI showed patient specific and random patterns after IA injections in active RA wrist joints. The degree of distribution increased with the MRI synovitis score, while no association was found with the erosion- and bonemarrow oedema score. These results indicate that a single injection into a standard injection site in the proximal part of the wrist cannot be assumed to distribute – and treat – the whole joint. © 2007 Elsevier Ireland Ltd. All rights reserved. Keywords: Intra-articular; Arthrography; Gadolinium; Distribution; Low-field MRI; Ultrasound 1. Introduction Intra-articular (IA) glucocorticosteroid injections have been widely used in rheumatoid arthritis (RA), since Hollander introduced this technique in the 1950’s [1], to obtain a more concentrated effect on the target joint and reduce the possibility of systemic adverse effects. IA glucocorticosteroid injections are especially used in the treatment of joints refractory to systemic Corresponding author. Tel.: +45 38164155; fax: +45 38164159. E-mail addresses: parker@frh.regioh.dk (M. Boesen), karl.erik.Jensen@rh.regionh.dk (K.E. Jensen), cimmino@unige.it (M.A. Cimmino). 1 Tel.: +45 35452299/3545. 2 Tel.: +39 0103537900; fax: +39 0103538638. ∗ 0720-048X/$ – see front matter © 2007 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ejrad.2007.08.037 therapy or as adjunct to this [2], however long-term, repeated use, may cause adverse effects [3]. Correct placement of the injections has also been a matter of concern [4], but this problem may be overcome by the use of ultrasound (US) [5]- or fluoroscopic guidance to ensure correct intra-articular injections [6]. By injecting drugs into a joint using one standard injection site, the clinicians assume that the drug is evenly distributed in all the joint compartments. This assumption is true for singlechambered and larger joints such as the hip, knee, shoulder and elbow joints [7]. In contrast, the wrist consists of six small synovial articulations linked by semi-permeable connecting channels and bound tightly together by intrinsic and extrinsic ligaments [8]. Thus, in the wrist, the distribution of IA injected drugs or contrast material may be inhibited in parts of the joint distant to the injection site due to this complex individual 332 M. Boesen et al. / European Journal of Radiology 69 (2009) 331–338 anatomy. This notion is supported by the pioneer arthrographic studies on cadavers and randomly selected subjects showing that between 10 and 50% of the “normal” population have communication between the radio-ulnar and the radio-carpal joint [9–12] and 13–60% have communication between the radio-carpal and inter-carpal joints [9,10,12–14]. In general the degree of communication increases with age most likely due to degeneration and “wear and tear” of ligaments and cartilage [10]. Based on this, some radiologists have suggested a triple injection technique before MR wrist arthrography to obtain an equal distribution of contrast for proper evaluation of ligamentous injury [15,16]. The usual technique in rheumatology is to perform a single injection in the proximal central- or the ulnar part of the wrist joint when an IA drug injection is needed [17]. This approach is based on experiences from arthrographic studies of wrist joints showing a communication between joint compartments in up to 90% of patients with RA [12,18,19]. The theory is that especially in persistent RA the ligamentous connections have been destroyed by the inflammatory process, which would allow fluid to pass between the proximal and distal wrist compartments [12,18,20]. However, even if this were the case, the distribution of a small IA fluid volume might be blocked by pannus and the aim of this study was to investigate the distribution of a drug solution in the wrist joint using MRI arthrography after an ultrasound-guided IA injection in patients with persistent RA. 2. Materials and methods Seventeen patients (Table 1) with active RA according to the ACR criteria were included from the outpatient clinic at the Department of Rheumatology and the Parker Institute, Frederiksberg Hospital. All patients were treated with DMARDS (9 methotrexate, 9 sulphasalazine, one with infliximab, two with oral prednisolone), however, due to wrist arthritis resistant to the systemic treatment, the clinician referred them to an ultrasoundguided IA injection of methylprednisolone. The mean age was 54 years (range 26–78), female/male ratio was 14/3, mean disease duration was 7 years (range 2–24), mean CRP concentration was 3 mg/dl, and IgM rheumatoid factor (RF) was present in 11/17. All patients were seen after 2 weeks and possible adverse events were recorded after clinical inspection of the wrist area. In our study, the wrist joint was defined according to published standards for MRI studies in rheumatology [21] and comprises the radio-ulnar joint, the radio-carpal joint, the inter-carpal joints and the four ulnar carpo-metacarpal joints (Fig. 1). 2.1. Ultrasound (US) All ultrasound (US) examinations were performed by a trained specialists in musculoskeletal US using a Sequioa® (Mountainview, CA, USA) with an 8–13 MHz linear array transducer or a Logiq 9 (General Electric, Milwaukee, IL, USA) with a 14 MHz transducer. Following the baseline MRI examination, the patient had an US-guided IA drug injection into the space between the central part of the radius and the lunate bone in the wrist (Fig. 2). The drug solution contained 1 ml Depomedrole® (40 mg/ml), 0.5 ml Lidocaine® (5 mg/ml) and 0.15 ml gadolinium (Omniscan 0.5 mmol/ml). The US-guided injection was performed according to recommended standard from the dorsal side of the wrist with the transducer in the sagittal plane showing the distal end of the radius and the proximal part of the lunate bone as well as an extensor digitorum tendon in the image plane. Needle insertion was performed perpendicularly to the transducer with Table 1 The OMERACT MRI scores and the distribution count for each patient Patient no. Sum MRI erosion Sum MRI oedema Sum MRI synovitis D RU D1 D2 D3 D Flex D Ext Sum distribution 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 25 9 11 9 16 16 14 7 20 22 4 17 10 12 20 22 18 12 5 11 7 0 5 35 1 32 4 2 7 13 8 7 6 10 3 3 6 6 4 8 9 4 8 4 3 3 4 5 5 5 4 0.5 0 0 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0.5 0.5 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 1 1 1 1 1 1 0 0.5 1 1 1 1 1 0 0 0 0 1 0 0 1 0 0 0.5 0 0.5 0.5 0 1 0.5 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.5 0.5 1.5 4 3 3 4 3 3 2.5 1.5 2.5 2.5 2 3 2.5 1 Mean Minimum Maximum 14.2 4.0 22.0 9.6 0.0 35.0 5.1 3.0 9.0 0.4 0.0 1.0 0.9 0.5 1.0 0.7 0.0 1.0 0.3 0.0 1.0 0.06 0.0 1.0 0.06 0.0 1.0 2.4 0.5 4.0 MRI: OMERACT MRI score; D RU: distribution to the radio-ulnar joint; D 1: distribution to the radio-carpal joint; D 2: distribution to the inter-carpal joint; D 3: distribution to the carpo-metacarpal joint; D Flex: distribution to the flexor tendons; D Ext: distribution to the extensor tendons; 0: no distribution to the joint space; 0.5: partial distribution to the joint space; 1: full distribution. M. Boesen et al. / European Journal of Radiology 69 (2009) 331–338 333 subsequent MR images on both high and low field (data not shown). The chosen dose of gadolinium ranged from 0.1 to 0.15 ml taken from a standard gadolinium solution (Omniscan 0.5 mmol/ml), which gave good enhancement in a pilot examination and was easy to apply to the drug solution for the clinician performing the US-guided injection without prior dilution. This gave a gadolinium concentration of approximately 45–50 mmol/l in the injected solution which is approximately 10 times higher than the recommended MR arthrography solution on low-field scanners according to a recent publication [22]. The high concentration did leave room for further dilution after injection without loosing signal, as we suspected a dilution of the injected gadolinium due to possible existing effusion as well as washout from the joint cavity; there was a delay of 20–30 min between the US-guided injection and the subsequent MRI. 2.3. MRI Fig. 1. The wrist joint compartments. The wrist joint is, in our study, defined as RU: the radio-ulnar joint, RC: the radio-carpal joint, IC: the inter-carpal joints and CMC: the four ulnar carpo-metacarpal joints. skin penetration in a 30–40◦ angle from the radial or ulnar side of the joint pushing the needle forward until the tip was visible in the image plane. Drug injection was documented by recording an image-clip during injection with the needle tip in the image plane. 2.2. Gadolinium dose The gadolinium dose was chosen after a minor in vitro pilot experiment where performed testing different doses (0.1, 0.15, 0.2, 0.3 ml Omniscan 0.5 mmol/ml) of the gadolinium compound added to 2 ml saline. In addition we tried to use a prediluted gadolinium solution of 2 mmol/l (Magnevist® , Schering, Germany) but adding 0.15 ml of this solution to the injected methylprednisolone was too low a dose to be recognized on the Fig. 2. Ultrasound-guided injection. It is a longitudinal image with proximal oriented left. The needle tip (arrow) is seen with comet tail artefact between radius (R) and lunate (L). The injected fluid is seen as a hyperechoic cloud (arrowheads) spreading distally from the needle tip into the synovial duplication of the radio-carpal joint (S). On ultrasound, the fluid does not continue into the synovial duplication of the inter-carpal joint cavity (SS). General Electric, Logiq 9 with 14 MHz linear array matrix transducer. MRI was performed at baseline and 20–30 min after USguided IA injection of methylprednisolone. All patients were examined using a 0.2 T musculoskeletal dedicated extremity MR-scanner (E-scan® , Esaote Biomedica, Genoa, Italy). The first five patients were also scanned after the IA injection on a high-field MR-scanner (Philips Intera® 1.5T, Philips, Eindhoven Nederland) in order to evaluate whether low-field MRI had equal sensitivity compared to high-field MRI in tracing the distribution pattern of the injected drug. The patients were examined in supine position with the hand along the side of the body. For signal collection a receive-only cylindrical solenoid wrist coil was used. The following pulse sequences were applied; gradient-echo scout, coronal STIR (TR/TE/TI: 1310/24/85, fov/matrix: 200 mm × 170 mm/192 × 163, slice thickness 3.0 mm) and axial/coronal turbo 3D T1 gradient echo (TR/TE: 38/16, fov/matrix: 180 mm × 180 mm × 100 mm/192 × 160 × 72, slice thickness 0.8 mm). After these images were acquired an intravenous injection of gadolinium (Omniscan 0.5 mmol/ml GE/AMERSHAM)) was given in a dose of 0.2 mmol/kg of body weight. And the coronal and axial T1 weighted 3D pulse sequences mentioned above were repeated. Total scan time was 45 min. The patient received the i.v. gadolinium injection in order to calculate the OMERACT RAMRIS synovitis score [23]. Twenty to thirty minutes following the US-guided steroid injection (40 mg Depomedrole) with 0.15 ml gadolinium (Omniscan 0.5 mol/ml), the patient had an additional MRI of the same wrist to track the distribution of the injected drug using the same coronal and axial T1 weighted 3D pulse sequences as mentioned above. All patients were investigated within the advocated 45 min after injection [24]. Even though the patient had a baseline MRI with the use of i.v. gadolinium, the distribution pattern of IA gadolinium was clearly defined due to the very high intensity signal achieved after the IA application as well as the fact that there were approximately 1.5–2 h between the baseline i.v. dose and the IA injection. 334 M. Boesen et al. / European Journal of Radiology 69 (2009) 331–338 Fig. 3. Distribution to the radio-carpal and radio-ulnar joint compartments coronal (A) and axial (B) and reconstructed sagittal (C) turbo 3D T1 gradient echo images after IA treatment. This patient is an example of distribution to the radio-ulnar joint and the radio-carpal joint. Note that pannus tissue seems to block further spread of the gadolinium contrast to the more distal parts of the wrist joint. Note the big erosion in the lunate bone is well filled with the contrast agent giving a possible T2 effect in the image. In the first five patients an additional MRI was performed on the high-field scanner using a wrap-around sense coil with the hand placed above the head. The following sequences were applied: gradient echo scout, 3D coronal and axial Gradient echo T1 FFE SPIR with SENSE (TR/TE: 39/5.2, fov/matrix: 150 mm × 150 mm × 100 mm/512 × 256 × 166, slice thickness 1.5 mm). Five patients had an additional MRI performed on the lowfield scanner the following day to examine whether the injected gadolinium still was detectable in the images. All low-field MR-images were evaluated on the scannerprocessing console using the standard ESAOTE software programme. High-field images were evaluated on the Philips workstation Viewforum® , software version 9.4. oedema and erosions [23]. The same observer (MB) scored all images and in cases of doubt, the OMERACT reference atlas was used as reference for scoring [21]. 2.4. Image evaluation US-guided injection of gadolinium is a well-known and accepted clinical examination for diagnostics purposes. The injections of methylprednisolone in this study were all performed as part of the routine therapy in our outpatient clinic. The extra MRI scans were considered as part of a pilot study and not evaluated by the ethical committee. The images were evaluated by two trained viewers in musculoskeletal MRI (a radiologist (MB) and a rheumatologist (MC)) using qualitative comparison between the T1 weighted MR images before and after IA injection, in order to detect the distribution pattern (Figs. 2–5). The distribution pattern of each patient was recorded regarding distribution to the radio-ulnar joint, radio-carpal joint, the inter-carpal joints and the carpo-metacarpal joints. Spread to the tendon sheaths was also recorded. A full distribution in one joint compartment was given the value 1, partial distribution to a single joint compartment was given the value 0.5 and no distribution was given the number 0 (Table 1). A sum of the total distribution count for all four compartments was calculated. The inflammatory activity was scored according the OMERACT RAMRIS evaluation standard for synovitis, bone marrow 2.5. Statistics In the 17 patients with RA, relationships between the distribution sum for all four compartments and the different OMERACT scores, duration of disease, RF status and CRP concentration, and the patient evaluated treatment response were calculated using Spearman’s two-tailed correlation. p-Values <0.05 were considered significant. 2.6. Ethics 3. Results The OMERACT MRI scores and the distribution count for each patient are listed in Table 1. There were no differences in sensitivity, between the five patients examined on both high- and low-field MRI regarding the detection of the drug distribution (mean distribution score 2.2 on both modalities). We were not able to compare the OMERACT scores from the different MRI modalities because the high-field protocol was not designed for this purpose. M. Boesen et al. / European Journal of Radiology 69 (2009) 331–338 335 Fig. 4. Distribution to the radio-ulnar joint, the radio-carpal joint and the inter-carpal joints. Coronal (A) and axial (B) turbo 3D T1 gradient echo images after i.a. treatment. This patient is an example of distribution to the radio-ulnar joint, the radio-carpal joint and the inter-carpal joints. Note the arrow in (A) pointing at a disrupted intrinsic carpal ligament between the lunate and the scaphoid bones compared to an intact ligament between the lunate and the triquetrum. The line in (A) indicate the image level in (B) where the arrowhead point at the ultrasound-guided injection site. No universal pattern was seen in the distribution of the contrast. Only two patients had a full spread of contrast to all four joint compartments, and the mean distribution count for all patients was 2.4 (range 0.5–4). One patient had only contrast in the radio-ulnar joint, three patients had full or partial spread of contrast to the proximal carpal row and 10 patients had full or partial spread of contrast to both the proximal and inter-carpal rows (Figs. 3–5) (Table 1). The OMERACT synovitis score correlated with the distribution count (r = 0.60, p = 0.014), while no association was found between the distribution pattern and the erosion score (p = 0.70) or the bone marrow oedema score (p = 0.35). There was no cor- relation between the MRI distribution pattern of the drug and the following parameters: age, disease duration, IgM RF status, and CRP value. We saw evidence of a communication between the wrist compartment and inflamed tendon sheaths in two patients. In one case distribution to the extensor tendons was seen, and in one patient a signal enhancement was seen in the flexor tendons. In five patients an additional low-field MRI the following day (18–26 h after injection) found no MRI signal alterations typical for remnants of a previously injected gadolinium solution. Clinical inspection at baseline and at 2 weeks follow-up revealed no side effects after the injection. Fig. 5. Distribution to all wrist joint compartments. Coronal turbo 3D T1 gradient echo images after i.a. treatment in two patients (A) and (B). Both patients are examples of distribution to the all compartments (n = 3) of the wrist including the radio-ulnar joint. Note the arrow in (A) pointing at a disrupted intrinsic carpal ligament between the lunate and the scaphoid bones compared to an intact ligament between the lunate and the triquetrum. 336 M. Boesen et al. / European Journal of Radiology 69 (2009) 331–338 4. Discussion The present study confirmed the well-known anatomic fact of a large diversity regarding the complex anatomy and intercommunication of the multiple joints comprising the wrist joint. The different distribution patterns in this cohort of patients with RA, may be due to “normal” variation [10,12,14] or may be caused by arthritic changes [18,19,20]. A higher degree of joint communication could be caused by destruction of the interposed septa as indicated in some patients (Figs. 4A and 5A). Here, the contrast passes through the intrinsic ligament of the lunate and scaphoid bones as an indication of damage to this structure. If this were the explanation, a larger degree of communication might be expected in long-standing arthritis, which was, however, not observed in our series. On the other hand we found a correlation to the OMERACT synovitis score indicating that patients with more synovitis have a better distribution of the drug to the various joint compartments. In contrast to this finding, it may also be speculated that expanding pannus might lead to a lower degree of joint communication by blocking the distribution between compartments of small fluid volumes, as could be seen in the patient in Fig. 3. Our data support the in vivo arthrographic findings in RA patients by Trentham et al. [10] showing that the distribution pattern of contrast in the wrist joint varies, which is in conflict with the previous anatomical and arthrographic findings in cadavers [18,19] showing that patients with RA in 90% of the cases have communication between most wrist compartments. The distribution pattern may be different when tested in vivo and with a smaller volume as the 2 ml used in our study; which also is in accordance with the conclusions in the paper by Trentham et al. using conventional arthrography after injection of 2 ml X-ray contrast (Renografin 60) [10]. Whatever the reason for the different distribution patterns, our study show that in most cases a drug injection into the radiocarpal joint will be insufficient as treatment for the all the joints comprising the wrist. An explanation for non-response in some patients to an IA injection of a potent anti-inflammatory drug such as glucocorticoid, is the fact that injections without guidance may not hit the joint cavity at all [4]. In our series this possibility was overcome by giving all injections guided by US with documentation of the placement of the injected substance into the joint space between the distal radius and the lunate in the proximal wrist compartment. The placement was in all cases confirmed on the subsequent MRI. The US technique does not, however, ensure a distribution of the drug into all relevant areas of activity, which could be one of the reasons for treatment failure with injections into the wrist. To our knowledge, our study is the first to address this potential problem using MRI to trace the drug distribution, and our results support the conclusion that communication between the various compartments within the wrist joint varies between patients. Our results also showed distribution to the tendon sheaths in two patients, which indicate that there is a direct communication between the wrist compartment and the tendon sheaths in some patients. This distribution could be due to an abnormal capsule communication or a reflux of the injected drug through the injection canal, which was, however, not seen using real-time US. Our standard is to make sure that the extensor tendons and tendon sheaths are seen clearly on the screen and are kept out of range from the needle (Fig. 2). Also, in one patient a distribution to the flexor tendons was observed after a dorsal injection far from these tendon sheaths. Accordingly, as only few patients have communication between the tendon sheaths and the wrist joint, tenosynovitis seems not to be treated along with the wrist joint and significant inflammation in the tendon sheaths should be treated separately. It has until now been our routine to give IA injections in the wrist in the space between the central part of the distal radius and the lunate bone. Our present series shows that this approach is inadequate and we suggest further studies to develop the optimum injection strategy for the wrist joint. One strategy suggested by Koski and Hermunen may overcome this by injecting into both the radio-carpal joint and the inter-carpal joints, which in their study showed a better response than a single injection into the standard site [25]. According to our results, listed in Table 1, the radio-carpal joint was reached to a large extent by one injection in the majority of patients (16 of 17). One patient had contrast enhancement only in the radio-ulnar joint suggesting that the US-guided injection into the radio-carpal joint applied the treatment in this joint space without further distribution to the rest of the wrist. The inter-carpal joint was reached in 12 of the 16 patients with successful delivery of treatment to the radio-carpal joint; however, the carpo-metacarpal joints did not receive any contrast in most of the patients (11 of 17) and was thus not treated sufficiently. With the use of US Doppler, most active areas in the wrist may be distinguished and possibly partitioned injections should be guided into these by US to optimize the effect of the steroid. It must be noted, however, that in some cases an injection placed directly in the pannus may give rise to unpleasant tension in the tissue. To avoid this, a small pre-injection of air to ensure the position of the needle tip free in the joint cavity has been used, however this method does not allow a full description of the distribution apart from an immediate verification of the positioning of the needle [5]. Finally we found an indication that high-field MRI and lowfield MRI seems to reveal similar sensitivity to the distribution of the IA contrast, supporting the use of dedicated extremity MR-scanners to track the distribution pattern, as this modality is more patient friendly and the costs of the examinations are lower [26]. A larger study designed to compare the high- and low-field scanner performance in this perspective is desirable. The chosen gadolinium dose was in the high range (50 mmol/l) compared to previously published arthrographic studies in the wrist on both 1.5 T [27] and 0.2 T [28] using up to 8 ml of injected solution. As the current study was designed to trace the distribution of the injected drug using a standard 1.5–2.0 ml volume, and was not considered to be a diagnostic arthrography of the wrist, no direct comparison can be made. A recent in vitro publication has shown the optimal gadolinium dose to be in the area between 2 and 5 mmol/l in the 0.2 T low-field scanner when injecting approximately 20 ml into a shoulder joint of cadavers [22]. In contrast to that study, we had no imaging problems with tracing the distribution pattern M. Boesen et al. / European Journal of Radiology 69 (2009) 331–338 using the 10 times higher concentration even though one patient revealed a signal drop within a large erosion of the lunate bone that could be due a concentration dependent T2 effect (Fig. 3). Finally, our observation that the gadolinium was not seen in the MR images the following day is in accordance with the previous reports and reviews of the temporal behavior of IA gadolinium injections concluding that the IA gadolinium have left the joint cavity within 24 h [29,30]. The small volume injected and the use of a low-field MR scanner may also account for the lack of visible gadolinium on the 1-day follow-up MR scan [29]. In retrospect our concentration of gadolinium was high. However, when we started the data collection of the current pilot study no studies had addressed the optimal gadolinium dose for the presented arthrographic procedure in wrists using a low-field scanner. Our preliminary results revealed good visualization in the MRI images and as the injected volume was low compared to standard arthrography volumes we continued this pilot experiment with the above-mentioned solution. Regarding the safety aspects of the procedure the literature state that for IA injection of gadolinium, the total amount rather than the local concentration of gadolinium in one joint is of importance for possible toxicity [29]. The range of concentrations optimal for tracing the drug distribution in the wrist on the low-field scanner remains to be determined, as well as the cost effectiveness of the suggested MR arthrography method versus a more conventional fluoroscopically guided arthrography method. We choose to use MR arthrography in our study to trace the drug distribution, as many rheumatologists increasingly use MRI to monitor therapy response and we wanted to reduce the lifetime radiation dose of the involved patients to a minimum. In conclusion the distribution of the injected drug solution with added gadolinium contrast showed patient specific and random patterns in the MR images after IA injections in active RA wrist joints. The degree of distribution correlated with the MRI synovitis score, while no association was found with the MRI erosion- and bonemarrow oedema scores or any clinical scores. The results indicate that injection into the proximal central part of the wrist cannot be regarded as sufficient to treat the whole wrist joint. The diversity of distribution patterns among patients could be an explanation of the variation in treatment responses seen with IA injections [17,31] and based on our results we suggest that patients, who do not respond sufficiently to IA injections into the wrist joint, should have their distribution pattern examined and might benefit from additional injections elsewhere in the joint. Conflict of interest None. Acknowledgements We thank the Oak foundation and the Meyer’s foundation for their financial support and the technologists at the Departments of Radiology at Frederiksberg hospital for their aid in obtaining the MRI. 337 References [1] Hollander JL. Hydrocortisone and cortisone injection into arthritic joints. Comparative effects of and use of hydrocortisone as a local antiarthritic agent. JAMA 1951;147:1629–35. 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