Over the last decade, increasing numbers of rheumatologists have incorporated musculoskeletal ultrasound (MSUS) as a valuable diagnostic tool into their clinical practice. Some countries have established training programmes for MSUS. The European League Against Rheumatism has developed education guidelines for the content and conductance of MSUS courses and it would be useful to standardise rheumatology MSUS training worldwide. A thorough knowledge of anatomy, US physics and technology, US scanning methods, US pattern of normal and pathological musculoskeletal tissues, definitions for US pathology, artefacts and pitfalls in both greyscale and Doppler modalities is necessary to perform efficient MSUS. MSUS training includes attending theoretical–practical and online courses, as well as studying textbooks and using digital video discs (DVDs). Having access to US equipment and performing supervised normal and pathological MSUS examinations for a training period are mandatory for consolidating MSUS learning. A proposal to accredit and certificate competence in MSUS is now being discussed.
Musculoskeletal ultrasound basis
Ultrasonography (US) is an imaging technique based on the emission and reception of mechanical sound waves with a frequency greater than the hearing frequency range of the human ear (i.e., 20 kilohertz (kHz)) by piezoelectric crystals located inside the transducer or probe. Ultrasound wave frequencies of diagnostic US systems range from 3 megahertz (MHz) to 25 MHz. Ultrasound waves transmit differently through different media depending on their composition and are reflected at the interfaces between materials of different acoustic impedance. The reflection of ultrasound through the body tissues generates US images that consist of varying degrees of black-and-white images. The US technique includes greyscale imaging of anatomic structures and blood-flow detection by Doppler technique. Doppler US is based on the alteration of the frequency of a sound beam reflected back to the source when it encounters a moving object.
For the last 50 years, the medical applications of Doppler US have included diagnosis of abdominal, pelvic, obstetric, breast and cardiac pathologies. More recently, musculoskeletal ultrasonography (MSUS) has progressively become an established imaging technique for evaluating peri-articular and intra-articular structures involved in musculoskeletal conditions, including rheumatic diseases. The use of high-resolution transducers improves the visualisation of different anatomic structures and permits the assessment of a wide range of inflammatory and structural abnormalities. The use of appropriate probe frequencies is mandatory for the correct imaging of musculoskeletal structures and optimises the US detection of local pathology. At higher frequencies, the image resolution will be greater but the tissue penetration will be lower. Therefore, higher-frequency linear transducers (e.g., 10–18 MHz) should be used for superficial anatomic structures, such as the small joints of the hand and feet, whereas lower-frequency transducers (e.g., 5–10 MHz) can be used for deeper joints, such as the hip, ankle and shoulder. In addition, a correct machine setting markedly increases the sensitivity of the equipment in assessing a number of abnormalities, both by using greyscale and Doppler modalities.
US is a routinely available, dynamic, non-invasive and relatively inexpensive bedside imaging method that consent a multiplanar assessment of musculoskeletal system, with high patient acceptability. The technique facilitates the scanning of all peripheral joints as many times as required at the time of consultation. In addition, a multi-joint assessment can be performed during the same scanning session.
Applications of MSUS in rheumatology
Recent advances in technology have led to an extraordinary improvement in the quality and level of US equipment, with production of machines that consent a good visualisation of most superficial and deep musculoskeletal structures. Particularly, the great resolution of anatomic details at the level of superficial musculoskeletal structures offered by high-frequency transducers has promoted an increasing use of MSUS both in rheumatologic routine clinical practice and in research settings. In addition, the enhanced sensitivity for detecting low-velocity flow in small synovium, tendon and enthesis vessels achieved by recent colour Doppler and power Doppler techniques has led to the incorporation of Doppler US in rheumatology. The difficulties in detecting abnormalities within deep joints by physical examination facilitate the applications and use of US also in the assessment of pathology at the level of large joints.
MSUS allows an immediate correlation between imaging findings and clinical data, which improves diagnosis and management of patients with a range of rheumatic diseases from inflammatory arthritis, vasculitis or osteoarthritis to soft-tissue diseases . MSUS has demonstrated more sensitivity than clinical evaluation in assessing joint inflammation . There have been an increasing number of studies on the validity of Doppler US for evaluating inflammatory activity in arthritic joints . Greyscale and Doppler US have an increasing role in therapy monitoring in inflammatory arthritis as well as in the evaluation of sub-clinical MSUS-detected synovitis, which can predict structural damage progression and disease relapse in patients with rheumatoid arthritis in clinical remission . In addition ultrasound is a bedside tool for performing accurate and safe musculoskeletal injections .
Applications of MSUS in rheumatology
Recent advances in technology have led to an extraordinary improvement in the quality and level of US equipment, with production of machines that consent a good visualisation of most superficial and deep musculoskeletal structures. Particularly, the great resolution of anatomic details at the level of superficial musculoskeletal structures offered by high-frequency transducers has promoted an increasing use of MSUS both in rheumatologic routine clinical practice and in research settings. In addition, the enhanced sensitivity for detecting low-velocity flow in small synovium, tendon and enthesis vessels achieved by recent colour Doppler and power Doppler techniques has led to the incorporation of Doppler US in rheumatology. The difficulties in detecting abnormalities within deep joints by physical examination facilitate the applications and use of US also in the assessment of pathology at the level of large joints.
MSUS allows an immediate correlation between imaging findings and clinical data, which improves diagnosis and management of patients with a range of rheumatic diseases from inflammatory arthritis, vasculitis or osteoarthritis to soft-tissue diseases . MSUS has demonstrated more sensitivity than clinical evaluation in assessing joint inflammation . There have been an increasing number of studies on the validity of Doppler US for evaluating inflammatory activity in arthritic joints . Greyscale and Doppler US have an increasing role in therapy monitoring in inflammatory arthritis as well as in the evaluation of sub-clinical MSUS-detected synovitis, which can predict structural damage progression and disease relapse in patients with rheumatoid arthritis in clinical remission . In addition ultrasound is a bedside tool for performing accurate and safe musculoskeletal injections .
Education and training in MSUS
Within the last years, increasing numbers of rheumatologists have incorporated MSUS into their clinical practice as a valuable imaging and research tool. Recent technological developments in the US systems resulting in the increasing utility of MSUS in rheumatology, the growing interest of rheumatologists in MSUS and the decreasing cost of sonographic machines have led to a great demand for appropriate education in this technique among rheumatologists worldwide. As MSUS is the most operator-dependant imaging modality – mainly because of the intrinsic real-time nature of US image acquisition – appropriate training is highly important to ensure skilled and safe use of MSUS by rheumatologists.
In a survey of rheumatologists by the British Society for Rheumatology, the principal reason given for not performing MSUS was the lack of training in MSUS (75% of respondents) . More recently, a European survey responded by representative from 31 countries showed that in most countries few rheumatologists perform MSUS in clinical practice and that training in this technique varies widely from country to country, with low implementation of competency assessment . A number of European countries run national training programmes for MSUS for rheumatologists. MSUS schools for rheumatologists, which can be supported by the national rheumatology societies or universities , have been created in some countries. In addition, MSUS has been incorporated into fellowship programmes and postgraduate rheumatology training in some European countries . However, there are probably still not enough rheumatologists and/or rheumatology centres able to provide MSUS training and most countries need to train new rheumatologist trainers in MSUS.
At present, many approaches are taken to teach MSUS. There is no standardised educational training programme in MSUS and no standard, accredited assessment of competency for rheumatologists performing MSUS. There are also not enough data on the outcome of training in MSUS, and the validity of current MSUS educational models has not been demonstrated. Thus, there is a need for a standardised curriculum, education guidelines and competency assessment in MSUS.
Fortunately, over the last years, a number of relevant papers on ultrasound education, curriculum and competency for rheumatologists have been published. These have contributed to the development of essential issues, MSUS training method and competency assessment in rheumatology . More recently, training in ultrasound-guided injections for rheumatologists among countries has been tested and results demonstrated that the percentage of rheumatologists receiving training in the field is <10% in over 70% of countries that participated in the survey .
Knowledge and skills necessary to become a musculoskeletal ultrasonographer
The knowledge and skills necessary to perform efficient and safe MSUS are shown in Box 1 . A thorough knowledge of sectional anatomy, ultrasound physics and technology, joint sonographic scanning methods, the ultrasound pattern of normal and pathological musculoskeletal tissues, artefacts, diagnostic criteria and Doppler technique is all necessary for the correct performance of MSUS. FLOAT NOT FOUND
In 2001, the first guidelines for performing MSUS in rheumatology were published by the European League Against Rheumatism (EULAR) Working Group for Musculoskeletal Ultrasound . These guidelines provided useful information on the technical basis for MSUS, equipment specifications, scanning methods and image acquisition along with the main pathological findings in each anatomical area.
Later on, Brown et al. produced an international interdisciplinary consensus on the specific indications, anatomic areas and knowledge and skills required by rheumatologists performing MSUS .
A knowledge of the applications, indications and limitations of MSUS in rheumatology should be the starting point in MSUS education. A basic theoretical knowledge of ultrasound physics and technology is necessary to understand the diagnostic capabilities of this technique. After a short period of practical training, trainees can easily recognise the US pattern of the different musculoskeletal tissues. MSUS examination is the most difficult aspect of training and requires long practical sessions. The standardised and systematic scanning methods of peri-articular and intra-articular structures accessible by US – the shoulder, elbow, wrist and hand, hip, knee, ankle and foot – should be learnt in practical training after a solid understanding of joint sectional anatomy has been acquired. Multiplanar with longitudinal and transverse scans of musculoskeletal anatomic structures should be performed to acquire maximal morphological information. Dynamic examination provides functional assessment of musculoskeletal structures that facilitates diagnosis of abnormalities. The target joint structures for rheumatologists are tendons, bursae, synovial recesses, articular cartilages and bony cortex. Knowledge of US examination of ligaments, muscle and peripheral nerves enhances an overall US investigation of the musculoskeletal system. Holding the probe correctly and optimising the greyscale settings of the sonographic system are mandatory for an appropriate learning curve. MSUS artefacts and pitfalls should be learnt to avoid misdiagnosis of MSUS pathologies.
In most MSUS training programmes, 50–100 US scans of each anatomic area in normal subjects are strongly recommended before starting US diagnosis of musculoskeletal abnormalities. This educational approach enables trainees to acquire a skilled enough scanning technique and to acquire experience in normal anatomic variants before using MSUS as a diagnostic method.
Diagnostic applications of MSUS for rheumatologists are focussed in those pathological conditions in which MSUS has proven clinical value. Basic MSUS training for rheumatologists must comprise the ability to detect joint synovitis, bursitis, tenosynovitis, bone erosions and osteophytes, as well as the differentiation of fluid from synovial hypertrophy ( Fig. 1 ). Moreover, trainees should be able to identify by US different tendon pathologies such as enthesopathy, tendon tear, tendinosis and tendon calcification. Articular cartilage lesions, peri- and intra-articular microcrystal deposits, myositis and joint and tendon ganglia and cysts should also be included in the MSUS curriculum for rheumatologist ultrasonographers.
In addition to greyscale MSUS, trainees should learn colour and power Doppler physics and technology, along with their application, indications and limitations in rheumatology. They need knowledge of the colour and power Doppler settings and artefacts. Rheumatologist ultrasonographers should be trained in the detection and quantification of synovial, tenosynovial and entheseal inflammatory activity by Doppler US ( Figs. 2 and 3 ). Additionally, at an advanced level, they could learn the role of US in vasculitis and be trained in the evaluation of target vessels and detection of vasculitis by US.
US-guided musculoskeletal interventional procedures, mainly peri-articular and articular injections, are a recommended skill for rheumatologists.
Pathological findings more common in other musculoskeletal specialities, such as peripheral nerve entrapment, ligament and fibrocartilage lesions, muscle injuries, soft-tissue masses and loose and foreign bodies, could be learnt optionally by rheumatologist ultrasonographers. MSUS in paediatric rheumatic diseases is a new and rapidly developing area for rheumatologists involved in this field. Finally, correct image documentation and appropriate reporting of ultrasound findings and diagnoses are important aspects of MSUS training.
The musculoskeletal pathologies included in the MSUS training curriculum for rheumatologists according to the recommendations for the content and conduct of EULAR MSUS courses are listed in Table 1 . They are classified in three levels of training: basic, intermediate and advanced.
| Basic level | Intermediate level | Advanced level |
|---|---|---|
| Joint synovitis | Tendon calcification | Peripheral nerve entrapment and lesions |
| Joint effusion | Enthesopathy | Ligament lesions |
| Synovial hypertrophy | Tendinosis | Fibrocartilage lesions |
| Bursitis | Paratenonitis | Myopathy |
| Tenosynovitis | Tendon subluxation/luxation | Myositis |
| Intrasubstance tendon lesions | Muscle injury | |
| Tendon impingement | Soft-tissue masses | |
| Complete tendon tear | Loose bodies | |
| Partial tendon tear | Foreign bodies | |
| Bone erosions |
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