Pediatric Musculoskeletal Ultrasonography

Part IFundamentals of Pediatric Musculoskeletal US

© Springer Nature Switzerland AG 2020

Y. El Miedany (ed.)Pediatric Musculoskeletal Ultrasonographyhttps://doi.org/10.1007/978-3-030-17824-6_1

1. Musculoskeletal US in Pediatrics: Physics and Techniques

Silvia Magni-Manzoni¹   and Domenico Barbuti²  

(1)

Pediatric Rheumatology, IRCCS Bambino Gesù Children’s Hospital, Rome, Italy

(2)

Radiology Department, IRCCS Bambino Gesù Children’s Hospital, Rome, Italy

Silvia Magni-Manzoni (Corresponding author)

Email: [email protected]

Domenico Barbuti

Email: [email protected]

Keywords

Musculoskeletal ultrasoundChildrenPhysicsEquipmentTechniques

Introduction

Musculoskeletal ultrasound (MSUS) represents an imaging tool particularly suited in pediatrics due to several advantages over other imaging modalities [1]. In the past decades, the developments in transducer technology and advances in the quality and presentation of MSUS images particularly favored knowledge and new insights in the appearance of joints at different developmental ages [2-6]. The awareness on the underlying physics and the use of appropriate technique specific for the musculoskeletal assessment in children and adolescents are fundamental for the correct acquisition and interpretation on MSUS findings [7, 8]. The present chapter will present the basic physical concepts, techniques, and main pitfalls in the use of MSUS.

Ultrasound Waves and Their Properties

Ultrasound (US) imaging is based on mechanical (sound) waves with frequencies ranging from 1 to 20 MHz. The waves are created by an electric current applied to piezoelectric crystals located on the footprint of a transducer, which is used for emitting sound waves and for receiving reflected echoes.

As all mechanical waves, sound waves are characterized by a frequency (the number of a complete wave cycle per second, expressed in Hertz, Hz), a length (the distance, in meters, between two close peaks of compression or rarefaction), and an intensity (amplitude of the peaks, usually measured as watt/cm², Pascal or deciBel). The higher the frequency, the shorter the wave length.

The velocity of the sound waves depends on the density of the material they encounter along their pathway: the higher the density, the higher the sound waves velocity.

US waves in tissues are handled differently between different tissue layers. They can be partially absorbed, partially transmitted, and reflected on border of different tissues, depending on their density and, therefore, their acoustic impedance: tissue with high density need less energy to start undulating than tissue with little density. An impedance change arises when US waves cross borders between tissues of different acoustic impedance, creating different grades of reflection, absorption and deflection of the waves. This is the base for the generation of echoes (Fig. 1.1).

Fig. 1.1

Physical mechanisms which occur when an US wave crosses the border between medium with acoustic impedance #1 and medium with acoustic impedance #2

The US waves are gradually weakened when crossing media (absorption). The loss depends on tissue density and content and is proportional to the US frequency: the higher the frequency, the greater the loss and the lesser the penetration of the US wave.

Reflection is observed when the US waves meet the layer between tissues of different impedance; the degree of reflection depends on the surface structure (smooth versus rough, straight or bent) and on the angle between the US beam and the tissue surface. Finally, scattering of the US beam provokes deflection of the US waves, which can be responsible of artifacts [9].

Focus

In transducers, multiple crystals create multiple individual waves that run in a bundle which converges proportionally to the dimensions of the crystals in the proximal part (Fresnel’s zone) and diverge in the distal part (Fraunhofer’s zone); the focus represents the point of transition between the proximal and the distal zone and acts as a lens (Fig. 1.2).

Fig. 1.2

Shape of the bundle of US waves, which converges in the proximal part and diverges in the distal part. The focus is the area of transition between the two parts, where the highest resolution is reached

In modern transducers, multiple lens, or focuses, can be used and need to be constantly optimized during the US assessment to create detailed images of the area/areas of interest, located at different depth from the surface (or the transducers’ footprint) [10–12].

Resolution

Resolution defines the minimal distance between two neighboring structures that can still be perceived separated. The lateral resolution represents the discrimination of objects side by side at same depth, and is mostly dependent on the beam width; the longitudinal and axial resolution is the discrimination of objects in direction of the US beam and are mostly dependent on the frequency. The higher the frequency, the smaller the depth and the better the resolution (Fig. 1.3).

Fig. 1.3

Spatial resolution of the ultrasound beam

US Equipment and Properties

US devices usually consist of transducers, which emit and receive US waves; cables to connect transducers to the system, made of hardware and software, for the processing of the US signals; a display monitor; a keyboard; a storage system; and documentation facilities.

The transducers crystals are responsible of the US beam emission and represent the sensitive part of the transducers. A good contact of the transducer to the skin with enough US gel (or surrogate) to eliminate air is mandatory for optimal transmission of US waves into the tissue and acquisition of correct images. The waves are then partially absorbed; some US waves, particularly at the border of different tissues, are partially reflected. At this point, the crystals act as US wave receivers: reflected US waves create an electric signal within the crystals, with an amount of energy dependent on the energy of the reflected waves and amplified accordingly. More reflected waves will impact the crystals with more energy and will be represented as a brighter signal (more echogenic); moderate reflection will show poor echo; no reflection will not be detected and will appear as echo-free or anechoic.

The spatial location of the reflecting structure is defined by the time interval between the emission and the reception of the US waves: the deeper the structure, the longer the US beam needs to travel to it and back form it; the longer the US beam takes to travel, the deeper the position of the corresponding structure. The US image is composed by the representation on the display of the processing of US signals, which depends on their energy and time interval to and from the different structures encountered.

US Parameters

The gain defines the overall amplification of the incoming US signals (echoes) and depends on the output gain, the size of the subject, and the area under investigation.

Since reflected echoes from deeper structures have to pass through much more tissue than those from the superficial structures, they undergo much more absorption. To compensate the signal loss due to this effect, the signal can be proportionally amplified through the time gain compensation (TGC) , which therefore should be constantly optimized during the US assessment. Of note, recent equipments may include automatic TGC.

The speed of the image update defines the persistence , or frame rate . Higher frame rates, with fast series of individual images, reduce the susceptibility to motion artifacts, but are usually coupled with a reduced resolution. More persistent image update allows the creation of a final displayed image through series of individual images, with increasing tissue density information and resolution, but at the cost of a slower displayed image.

The US signal can undergo a pre-processing, during the US assessment, with modulation of the signal quality and the sensitivity of crystals. Depending on the characteristics of the US manufacturer, there might be a post-processing, after the acquisition of the image, by modulating contrast, gray gain, etc., on frozen images.

Color and Power Doppler

A relevant aspect of MSUS examination is the possibility to detect synovial, tendinous, or muscular inflammatory hyperemia, which can be detected through color and/or power Doppler examination. It is worth to note that specific knowledge and experience are required when examining children by US, for not confusing physiological vascularization, within and around musculoskeletal structures, with pathological hyperemia.

The Doppler effect is a physical phenomenon in which the frequency of a wave that hits a moving body undergoes a variation that is directly related to the speed of the body itself. The Doppler technique compares the two frequencies and measures the difference between them. The obtained information can be represented as dot-by-dot color spots on the image elaborated in B-mode in an area defined in a box. Depending on the manufacturer, the size of the color/power Doppler box is predefined or can be decided by the operator. The box should always include the area of interest up to the skin surface. Since the main interest in rheumatologic diseases is in detecting low flows eventually present in synovial hypertrophy, Doppler parameters should be adjusted to assess low flows with low speed, applying low wall filters (WF) and pulse repetition frequency (PRF) between 700 Hz and 1 MHz. The gain should be progressively increased until random Doppler signal (also called noise) appears in the color/power box, and then progressively decreased to reach a value just under the noise threshold. The flow inside the vessels appears as color spots that can be visualized in different scales, according to manufacturer features and the operator preferences. While the power Doppler scales generally show only the presence of blood flow, the color scales display also the direction from and toward the transducer [13, 14].

Transducers

Transducers’ features [15] are of most importance for the investigation of small and relatively superficial sites, such as the musculoskeletal structures in pediatrics.

Modern transducers usually use a range of frequencies (multifrequency probes) and, therefore, allow the study of both superficial and deep structures in children at the same time, combining good penetration and resolution. The most recent generation of ultrasound equipment, with frequencies up to 20 MHz, allows highly detailed depiction of submillimetric structures located just a few millimeters from the probe footprint. For investigating deeper musculoskeletal structures, a good option is the use of a multifrequency probe at about 6–13 MHz.

Currently, linear-array transducers at variable sizes are available for musculoskeletal examinations, including large (>40 mm), medium-sized (<40 mm), and small-field-of-view (hockey-stick-shaped) probes. The selection of the most appropriate transducer primarily relies on the frequency to be used for the examination of a specific musculoskeletal area or structure. In case of small superficial structure with possibility of little contact to the skin, hockey-stick probes are particularly suited; on the contrary, for imaging deeper structures, high-frequency large-diameter transducers have the best potential, since they maintain the US beam shape to greater depths with less divergence, whereas they tend to have a large near-field beam width and a poor lateral resolution at shallow depths.

Handling

During evaluation of the musculoskeletal system, the probe should be handled with maximum stability over the region of interest, avoiding compression as much as possible. The stability of the transducer can be obtained by placing the long, ring, and little fingers of the examining hand directly on the patient’s skin or on a stable surface while holding the probe with the thumb and the index finger. With this grip, the examiners can easily translate the probe along its short axis at a given angle minimizing rotational changes [16].

Probe Positioning

The patient must be positioned in a proper way to make the examination comfortable both for the patient and the operator, regardless of the examined anatomical region [17, 18]. The angle of the ultrasound beam must be perfectly perpendicular to the examined structure, for avoiding artifacts and granting the acquisition of a correct image. It is recommended to perform longitudinal and transverse scans, and sometimes also oblique and unconventional scans, for a detailed assessment of the musculoskeletal structures. Recommended standard probe positioning for specific musculoskeletal sites are presented in the corresponding chapters.

US Software

In the recent years, different softwares improved the visualization of US images. They have different characteristics depending on the manufacturer, and their potential values still need to be extensively explored in children.

In compounding mode, the digital beam former steers the US beam at several steering angles during real-time acquisition rates [10], therefore reducing image artifacts (e.g., speckle, clutter, noise, angle-generated artifacts) and showing a sharper delineation of tissue interfaces and better discrimination of lesions over the background, especially in structures composed of specular echoes, such as tendons and muscles [9]. The beam steering function has been applied to B-mode imaging to obtain a parallelogram format with lateral sides parallel but oblique instead of a rectangular field of view. Oblique lines-of-sight run along the depth axis and can better display anisotropic structures, such as tendons or ligaments, in their oblique course from surface to depth.

Even when examining the relatively small musculoskeletal structures in children, it may be useful the widening of the field of view, which is often limited to 4 cm or less, due to the size of the best-suited transducers. The extended field-of-view technology uses specific image registration analysis to track probe motion and reconstruct a large composite image during real-time scanning over long distances and curved body surfaces. For instance, it allows to show large fluid collections and overview of the examined area.

In the recent years, the 3D technology has been applied to US [10, 19, 20]. Dedicated 3D-volume transducers sweep the US beam throughout the tissue volume by tilting the scan-head with a mechanized drive along the z-axis; after volume scan acquisition, the monitor displays reconstructed slices according to longitudinal, transverse, and coronal planes, which can be oriented within the volume block for detailed analysis by shifting around any of the spatial axes. This technology might be useful in a better understanding of physiological findings and vascularization in children’s joint; however, 3D probes are usually larger and more difficult to handle than standard probes, and experiences in this regard in children’s joints are scarce.

An additional innovative technique is the elastosonography , first used by Krouskop et al. in 1987, which allows to obtain information on the hardness and elasticity of soft tissues, particularly useful in the case of nodules or muscular lesions. It represents a sort of electronic palpation and is based on a simple principle: the compression of the tissue examined with the ultrasound probe produces a distortion, less in hard tissues and greater in soft tissues, which can be detected and quantified through a reprocessing of data obtained by US. The software displays an elastographic image in which the framed lesion is colored depending on its hardness, according to a chromatic scale usually ranging from red/green, in structures with greater deformability (i.e., soft nodules), to blue, in those with minimal or no distortion (i.e., hard and inelastic nodules). This technique, initially mainly used in diffuse hepatic changes and in thyroid nodules, proved to be very useful in the study of suspected tendons’, muscles’, and synovium alterations and of soft tissues in general [21].

Artifacts

Ultrasonographers should be aware of several artifacts that can occur and may be useful in the interpretation of findings, or, on the contrary, contribute to misinterpretation. Artifacts can be due to physical phenomena or to faulty scanning technique.

In fact, while some artifacts reduce the diagnostic power of the scan (reverberation, mirror effect, partial volume, doubling, empty tendon artifact), some others can be extremely helpful in the differential diagnosis (posterior acoustic enhancement, acoustic shadowing, comet tail, ring down and rain artifacts) [14, 22, 23]. Some artifacts can be avoided if the scan is performed in a proper way and the US equipment is properly set; others are caused by physical characteristics that cannot be changed. Nonetheless, they must be understood in order to avoid diagnostic mistakes.

Here is presented a list of US artifacts with their main features.

Posterior acoustic enhancement: an increase in echo intensity in tissues posterior to a fluid collection. It may not be detected when the fluid collection is small or spread over a large area (Fig. 1.4).

Fig. 1.4

Posterior acoustic enhancement is marked by *, deep to the fluid collection, marked by #, in a proliferative and essudative bursitis in a 10-year-old girl with juvenile idiopathic arthritis

Acoustic shadowing: a weakening or absence of echoes posterior to a gas collection (high absorption of the beam), a bone surface (high reduction of the beam) or calcification. Lateral acoustic shadowing: it occurs when the ultrasound beam is tangential to tissues with different acoustic impedance. The wider the impedance difference, the more visible is the artifact (Fig. 1.5).

Fig. 1.5

Lateral acoustic shadowing aside a Baker’s cyst (arrows) in a 5-year-old boy

Rain effect: a reverberation artifact due to the gain curve. This is an important sign because it occurs when soft tissue overlies a fluid collection. It appears as a band of low-to-medium echoes lying parallel to the transducer and apparently arising from the soft tissue and moving down through the fluid.

Reverberation artifact: due to its appearance, this artifact is also referred to as ring-down artifact and comet tail artifact. It is caused by the reflection of the ultrasound beam several times back and forth between two nearby interfaces. The multiple echoes thus created reach the transducer before the next pulse transmission and produce multiple copies of the anatomy.

Reverberation artifacts are commonly seen at soft tissue-to-gas/bone/metal interfaces.

Mirror artifact: a duplication of the image occurring when the beam meets a highly reflective interface causing reflection and reverberation phenomena (Fig. 1.6).

Fig. 1.6

Mirror artifact with specular reverberation of the metacarpal head, the distal diaphysis of the metacarpal and of the proximal part of the proximal phalanx of the III digit in a 9-year-old boy

Partial volume artifact: a noise that occurs when the US beam is wider than the scanned structure or the structure itself is just partially sectioned so that it is surrounded by tissues with different acoustic impedance. For example, if the beam sections a fluid collection that is narrower than the beam itself, a partial volume artifact will occur.

Duplication and triplication: occurs when the US beam crosses two tissues with different acoustic impedance. It appears as a duplication or a triplication of the image when the structure measures less than one centimeter and as a deformation, enlargement, or interruption when the object is larger (Fig. 1.7).

Fig. 1.7

Duplication and triplication (arrows) of the bone profile of the III right proximal phalanx in a 9-year-old boy with tenosynovitis of the flexor digiti propri tendon

Empty tendon artifact: occurs when the ultrasound beam is not perpendicular to the tendon, on both longitudinal and axial scans. The tendon appears, homogeneously or in some parts, hypoechoic without the normal fibrillar echotexture or totally anechoic (anisotropy), because of the relative obliqueness of the US beam to the fibrillar texture. The peculiar fibrillar pattern can be easily documented by slightly tilting the US beam perpendicular to the tendon course (Fig. 1.8).

Fig. 1.8

Empty tendon artifact

References

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Spannow AH, Pfeiffer-Jensen M, Andersen NT, Herlin T, Stenbøg E. Ultrasonographic measurements of joint cartilage thickness in healthy children: age- and sex-related standard reference values. J Rheumatol. 2010;37:2595–601.Crossref

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Roth J, Jousse-Joulin S, Magni-Manzoni S, et al.; Outcome Measures in Rheumatology Ultrasound Group. Definitions for the sonographic features of joints in healthy children. Arthritis Care Res (Hoboken). 2015;67:136–42.Crossref

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Van Holsbeeck MT, Introcaso JH. Musculoskeletal ultrasound. 2nd ed. St. Louis: Mosby; 2001.

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Teefey SA, Middleton WD, Yamaguchi K. Shoulder sonography: state of the art. Radiol Clin N Am. 1999;37:767–85.Crossref

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© Springer Nature Switzerland AG 2020

Y. El Miedany (ed.)Pediatric Musculoskeletal Ultrasonographyhttps://doi.org/10.1007/978-3-030-17824-6_2

2. Standardized Musculoskeletal Ultrasound in Pediatric Rheumatology: (normal Age-Related Ultrasound Findings)

Paz Collado¹   and Esperanza Naredo²  

(1)

Department of Rheumatology, Transitional Care Clinic, Hospital Universitario Severo Ochoa, Madrid, Spain

(2)

Department of Rheumatology, Bone and Joint Research Unit, Hospital Universitario Fundación Jiménez Díaz, IIS-FJD, UAM, Madrid, Spain

Paz Collado (Corresponding author)

Esperanza Naredo

Email: [email protected]

Keywords

Musculoskeletal ultrasoundStandardisationJoint anatomyPaediatric rheumatology

Abbreviations

JIA

Juvenile idiopathic arthritis

MCP II

Second metacarpophalangeal joint

MSUS

Musculoskeletal ultrasound

OMERACT

Outcome Measures in Rheumatology

Introduction

Imaging is among the most rapidly evolving fields within medicine. In the last 30 years, clinical practice has been transformed by the rapid expansion of sophisticated new technologies in that field offering a large range of instruments for better identifying and monitoring rheumatic diseases.

Among the various imaging modalities, musculoskeletal ultrasonography (MSUS) has been shown to be a readily available, reliable, and friendly tool for the assessment of inflammatory disease activity, particularly in children [1–11]. MSUS has demonstrated a higher sensitivity for detecting synovitis and tenosynovitis as compared to clinical examination in children [3–5]. One of the main problems is the lack of standardised procedures for validating this imaging modality before its widespread application. An additional problem is related to the unique anatomy of the growing skeleton in the child that is different from adult. Thus, the simple use of standards established for adults should be taken with caution.

The Outcome Measures in Rheumatology (OMERACT) Ultrasound Task Force is an international collaborative group of experts aiming to investigate the applicability of MSUS in rheumatology and to develop its metric properties for clinical trials. Among the different aspects of MSUS validation, the paediatric field has been considered as one of the main areas. With the aim of improving the validity of MSUS for the diagnosis and management of synovitis in juvenile idiopathic arthritis (JIA) , a new subtask force was created. This task force has developed a stepwise process: first, the development and validation, using the Delphi process, of definitions for US findings in healthy children and patients with JIA, and, second, creating a consensus agreement on a precise scanning method in different age groups, with the collection of images showing the sonographic appearance of physiologic vascularisation in several joints [12–16].

Here we describe briefly the main joint components in the healthy child as well as a systematic examination method (i.e. patient position, transducer placement, and joint positioning) for joint in children that can be easily reproducible among different sonographers and US machines.

Joint Components

MSUS examinations in paediatric rheumatology tend to focus mainly on peripheral skeleton, particularly synovial joints . Synovial joints are composed of several tissues, such as the articular bone surface, joint capsule, synovial membrane, and hyaline cartilage. Nevertheless, children differ significantly from adults in their bony anatomy as seen on US image; depending on the age and stage of maturity, their bones will not be completely ossified yet. At birth, the primary ossification centre is present in most of the long bone (diaphysis); meanwhile it is not present in most of the short bones. Throughout the first years, the secondary ossification centres will become apparent in the epiphyseal ends of the long bones [15, 17]. Because children with JIA may have abnormal US findings associated with inflammation and hyperaemia of affected joints, the knowledge of age-related US characteristics of healthy joints of children is essential to avoid misinterpretation.

Definitions for the US appearance of joints in healthy children were successfully developed through a consensus process and validated in practical exercises in two studies carried out by the OMERACT US group [12, 14]. The definitions are shown in Table 2.1.

Table 2.1

The definitions of the components of the paediatric joint detected on B-mode and Doppler US image in healthy children

Given the unique anatomy of the growing skeleton, it was not surprising that the development of those definitions, particularly, those related to the presence of joint Doppler signal, was more difficult to achieve. Since periarticular Doppler signal or that within joints may be a source of uncertainty or misinterpretation for inexperienced sonographers in paediatric MSUS, it seems mandatory to include the definition of physiological vascularity as one more component of the paediatric joint. The interpretation of the Doppler signal in the paediatric joint was the most challenging issues for the investigator group. As a result of the complexity of defining physiological vascularity, several separate statements for Doppler-detected normal joint vascularisation were provided instead of a full definition (Table 2.2).

Table 2.2

Final statements regarding final definition of physiological vascularity

Despite the fact that ossification is not a structural component of joint, ossification process in the child was an aspect to be taken into account during the development of those definitions. Ossification is an age- and joint-dependent process. A detailed knowledge about sonographic changes in the appearance of physeal and epiphyseal cartilages through the childhood is essential [17, 18]. Moreover, bone landmarks are important for proper image acquisition in children even though those are detected as unossified hyaline cartilage (Fig. 2.1).

Fig. 2.1

Elbow. Anterior joint recess . Br, brachialis muscle; arrow, anterior coronoid recess; FP, anterior fat pad

Standardisation of MSUS

General Comments

High-resolution US equipment is essential for paediatric MSUS work-up. The choice of the transducer depends on the type of examination. Higher-frequency transducers provide better spatial resolution, but these transducers have less penetration depth than a lower-frequency transducer. In children, high-frequency (7.5–18 MHz) linear transducers are generally appropriate for superficial and deeper joints. However, in obese patients, lower-frequency transducer may help the examination. The size of the footprint (the surface area of the transducer in contact with the skin) is also an important factor in the examination technique for paediatric patients. The hockey stick transducer (the smaller footprint) allows better angulations in small joints, particularly in the youngest children, reducing risk of artefacts.

The practical use of colour Doppler/power Doppler is the detection of increased joint and soft tissue perfusion, reflecting usually vascular abnormalities and active inflammation. However, Doppler signals should be carefully considered due to the presence of feeding vessels in growing skeleton as physiological vascularity [14, 15].

Last but not least, image documentation is another important aspect of MSUS. In general, every examination should be carefully documented, particularly descriptions regarding the age-related variations in the growing skeleton. All displayed structures should be documented in a standardised fashion to ensure an optimal reproducibility of these results. The orientation of the transducer in the standardised MS examination must be taken into account when documenting the reports with images. In longitudinal scan, the proximal part of the examined joint should be located on the left side of the screen, whereas the distal part of the joint should be located on the right side of the screen. In transverse scan, the medial/ulnar/tibial structures are usually shown on the left side of the screen, whereas the lateral/radial/fibular structures are shown on the right side of the screen.

US Examination Technique

Over the last years, a huge number of studies focused on paediatric MS conditions have been published, which have described patient positioning and US examination technique used in those studies. To overcome a strong operator dependence and the lack of standardised scanning protocols, the OMERACT US Task Force has recently published a systematic method for US examination of the four most commonly involved joints in JIA , i.e. wrist, second metacarpophalangeal joint (MCP II), knee and ankle joint. Additionally, one reference book published by the authors of this chapter provides information regarding patient positioning and transducer placement, as well as the sonographic appearance of each joint in different age groups [19].

The authors of this chapter have attempted to include the screening protocols considered essential for detecting joint synovitis in the paediatric population, in particular, patients with JIA , based on the clinical findings of JIA and the most common MSUS descriptions published in the literature (Table 2.3).

Table 2.3

Description of standard scans for evaluating the paediatric joint recesses

aThe glenohumeral joint normally has several recesses that preferentially distend with joint fluid, which include the biceps brachii long head tendon sheath, the posterior glenohumeral joint recess, the subscapularis recess and the axillary recess. A small amount of joint fluid can be seen in the biceps tendon sheath. Thus, an anterior approach of long head of the biceps brachii tendon may be recommended in children. The rotator cuff damage is uncommon in children

bAs the dorsal approach allows an excellent view of the anechoic/hypoechoic profile of unossified epiphyseal cartilage of bones forming the dorsal recess of radiocarpal and midcarpal joints, the volar approach is not usually included in children

cThe lateral approach is only possible on the 2nd metacarpophalangeal joint

dMedial aspect: the transducer should be longitudinally placed on the tibialis anterior tendon (used as a landmark). Midline aspect: the transducer should be placed at the sagittal midline of the ankle on the extensor hallucis longus and extensor digitorum tendons with the distal end of the transducer positioned on the talar dome (used as a landmark). Lateral aspect: the transducer should be longitudinally placed on the extensor digitorum tendon (used as a landmark)

eSo far, there is no universal agreement on how to approach the subtalar joint. The authors include the lateral and posterior based on literature and personal view [22]

Fig. 2.2

Scan approach of posterior glenohumeral joint recess . The child is sitting on the parent’s lap with the child’s hand on their opposite shoulder held by parent

Fig. 2.3

Scan approach of posterior elbow joint recess . The child is lying supine on the stretcher with the child’s hand on their opposite shoulder held by parent

Fig. 2.4

Subtalar. Lateral joint recess . Calcaneofibular ligament (Lig); arrow, joint recess

Fig. 2.5

Subtalar. Posterior joint recess. Asterisk, anechoic hyaline cartilage; arrow, joint recess; fhl, flexor hallucis longus muscle

Among extra-articular structures, the entheses have been attracting a growing interest for paediatric rheumatologists working in the field of MSUS imaging. A few detailed descriptions of US-assessed entheseal involvement in JIA patients have been provided. The first study was published by Jousse-Joulin et al. in 2011 [7] followed by the study of Weiss et al. in 2014 and Chauvin et al. in 2015 [20, 21]. The first authors described grey-scale and Doppler US abnormalities of lower limb enthesitis (i.e. quadriceps tendon insertion, proximal and distal patellar tendon insertions, Achilles tendon insertion and plantar fascia insertion on the medial calcaneal tubercle) of juvenile spondyloarthritis (JSpA). The second authors studied a wider enthesis spectrum, including several entheses of the upper limbs (common extensor tendon on lateral humerus epicondyle and common tendon flexor on medial humerus epicondyle). The third study established the normal appearance of the entheses in children. However, there is no consensus on which entheses should be evaluated in JIA and what approaches may be used in children yet.

Since children are usually restless, for US examination of the joint recess, the longitudinal axis was the first axis used in nearly all described scanning approaches (with the parapatellar recess being the exception) to identify each structure and image orientation, whereas the short (transverse) axis was usually used to scan tendons. In the knee, the transverse view of the parapatellar recess allows detection of a minimum amount of fluid, which may be not detected by sweeping the transducer from the medial to lateral side of the knee joint, using only the longitudinal suprapatellar approach (Fig. 2.6).

Fig. 2.6

Knee. Anterior parapatellar joint recess . Asterisk, lateral parapatellar recess; arrowhead, patellar retinaculum; F, femur; P, patella

Although the positioning of patient depends on the examined joint and varies according to the experience of different examiners, in the youngest children (e.g. 5 years), it is currently recommended to perform the US examination with the child lying supine/prone on the stretcher, or the child may sit on the parent’s lap in order to keep them calm. Whenever possible, in the case of a newborn/baby, it is preferable to scan them while sleeping. The patient position will be detailed in each joint throughout the chapter.

Care should be taken to examine the child for the detection of synovial effusion because of the high ratio of anechoic hyaline cartilage to bone in paediatric joint, which can be mistaken for fluid. Dynamic imaging during joint movement can improve the assessment of synovial fluid. As in adults, pathological findings should be documented in two perpendicular planes. Moreover, joints must be examined in their full length. It is mandatory to place the transducer in the axial plane and sweep it up and down over the dorsal/volar (palmar) of the peripheral joints to visualise as much as possible all joint components.

In general, we examine the child supine with arms placed near the side of the body and palms upward or downward in order to explore the anterior aspect of the elbow and shoulder and the volar and dorsal aspects of the joints of the hands. To explore the posterior aspect of the shoulder, the child is sitting on the parent’s lap with the child’s hand on their opposite shoulder held by parent. To explore both the knee and ankle, the child is lying in a supine position with the knee in flexion, around 45 degrees, and the foot resting on the surface of the examination bed.

References

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Colebatch-Bourn AN, Edwards CJ, Collado P, D’Agostino M-A, Hemke R, Jousse-Joulin S, et al. EULAR-PReS points to consider for the use of imaging in the diagnosis and management of juvenile idiopathic arthritis in clinical practice. Ann Rheum Dis. 2015;74:1946–57.Crossref

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Windschall D, Trauzeddel R, Haller M, Krumrey-Langkammerer M, Nimtz-Talaska A, Berendes R, et al. Pediatric musculoskeletal ultrasound: age- and sex-related normal B-mode findings of the knee. Rheumatol Int. 2016;36:1569–77.Crossref

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© Springer Nature Switzerland AG 2020

Y. El Miedany (ed.)Pediatric Musculoskeletal Ultrasonographyhttps://doi.org/10.1007/978-3-030-17824-6_3

3. FUNDAMENTALS OF MUSCULOSKELETAL Sonoanatomy in adults

Ingrid Möller¹, ²  , Maribel Miguel-Pérez¹   and Yasser El Miedany³, ⁴  

(1)

Unit of Human Anatomy and Embryology, Department of Experimental Pathology and Therapeutic, Faculty of Medicine and Health Sciences (C.Bellvitge), University of Barcelona, Barcelona, Spain

(2)

Instituto Poal de Reumatologia, Barcelona, Spain

(3)

Medway Foundation Trust, King’s College London, London, Kent, UK

(4)

Rheumatology and Rehabilitation, Ain Shams University, Cairo, Egypt

Ingrid Möller

Email: [email protected]

Maribel Miguel-Pérez (Corresponding author)

Email: [email protected]

Yasser El Miedany

Keywords

SonoanatomySonopathologyUSMusculoskeletalTendonJointLigamentRetinaculaFascia

Introduction

Anatomy is a basic science of knowledge concerned with the study of the organisms’ structure and their parts. The triad of human anatomy, physiology and pharmacology represents the three basic disciplines considered to be most relevant to daily clinical activity by both surgery and medicine healthcare professionals [1]. In the medical profession, anatomy is essential for performing precise physical examination and making a diagnosis, especially in soft tissue alterations, as well as for the interpretation of the images taken on scanning the affected body organ(s). During the last few decades, there has been an explosion of new techniques for imaging anatomy in living patients. Examples range from endoscopy and laparoscopy to ultrasonography, computed tomography and magnetic resonance imaging, together with new technology for three-dimensional visualization. The emergence of these sophisticated imaging