Indian J Pediatr DOI 10.1007/s12098-015-1957-2
REVIEW ARTICLE
Ultrasound Examination of Pediatric Musculoskeletal Diseases and Neonatal Spine Alka Sudhir Karnik 1
&
Alpana Karnik 2,3 & Alpana Joshi 4
Received: 31 May 2015 / Accepted: 8 November 2015 # Dr. K C Chaudhuri Foundation 2016
Abstract Ultrasound (US) is a simple, non-invasive imaging modality which allows high-resolution imaging of the musculoskeletal (MSK) system. Its increasing popularity in pediatrics is due to the fact that it does not involve radiation, has an ability to visualize non-ossified cartilaginous and vascular structures, allows dynamic imaging and quick contralateral comparison. US is the primary imaging modality in some pediatric MSK conditions like infant hip in developmental dysplasia (DDH), hip joint effusion, epiphyseal trauma and evaluation of the neonatal spine. US is the modality of choice in infants with DDH, both in the initial evaluation and posttreatment follow-up. US has a sensitivity equivalent to MRI in evaluation of the neonatal spine in experienced hands and is a good screening modality in neonates with suspected occult neural tube defects. In other MSK applications, it is often used for the initial diagnosis or in addition to other imaging modalities. In trauma and infections, US can often detect early and subtle soft tissue abnormalities and a quick comparison with the contralateral side aids in diagnoses. Dynamic imaging is crucial in evaluating congenital instabilities and dislocations,
Electronic supplementary material The online version of this article (doi:10.1007/s12098-015-1957-2) contains supplementary material, which is available to authorized users. * Alka Sudhir Karnik [email protected] 1
Department of Radiology, Dr Balabhai Nanavati Hospital, Mumbai, Maharashtra 400056, India
2
Sonosight Imaging Center, Mumbai, India
3
Department of Radiology, Holy Family Hospital, Mumbai, India
4
Shobha Diagnostic Center, Mumbai, India
soft tissue and ligamentous injuries, epiphyseal injuries and fracture separations. High-resolution imaging along with color Doppler (CD) is useful in the characterization of soft tissue masses. This article reviews the applications of US in pediatric MSK with emphasis on conditions where it is a primary modality. Limitations of US include inability to penetrate bone, hence, limited diagnosis of intraosseous pathology and operator dependency. Keywords Pediatric musculoskeletal ultrasound . Developmental dysplasia of the hip (DDH) . Epiphyseal injuries . Neonatal spine
Introduction Usage of ultrasound (US) in the evaluation of diseases of the musculoskeletal (MSK) system has gained considerable popularity. The ability of US to depict soft tissues, cartilaginous and vascular structures makes it an ideal modality in the pediatric age group and more so in neonates to visualize unossified cartilage. No radiation, better patient compliance, less need for sedation and real-time imaging with easy comparison of the contralateral side also makes US a favourable imaging modality. In addition, Color Doppler (CD) helps evaluate hyperemia in inflammatory and neoplastic conditions. Currently US is the primary modality of choice in evaluation of the neonatal hip for developmental dysplasia and to look for joint effusion. It is the initial modality in evaluation of general abnormalities involving muscles, tendons, joints, soft tissue tumors, foreign bodies and the neonatal spine. This article reviews the current role of US in imaging pediatric MSK diseases with emphasis on conditions where US is essential in making a diagnosis.
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Fig. 1 On Coronal view of the hip, three lines are drawn: Baseline tangential to the iliac wing; Acetabular roof line- joining the promontory to the deepest edge of the acetabulum; Labral line- drawn
from promontory to middle of fibrocartilaginous labrum. Alpha angle is the angle between the first and second lines and beta angle between the first and third lines
Hip Ultrasound
femoral head. There are two major components of DDH, instability and abnormal acetabular morphology. The static method assesses acetabular and femoral head morphology, location of the femoral head, appearance of the labrum and presence of fatty pulvinar in the hip joint. The dynamic method evaluates joint stability. Morphological evaluation of the infant hip incorporates two orthogonal views -coronal (Fig. 1) and transverse. Measurements are made on the coronal view, static images without stress.
The first successful application in MSK, hip US was introduced in the 1980’s by Graf in Germany [1] and by Harcke et al. in the United States [2], at about the same time. Today, use of real-time US to assess congenital dislocation and/or dysplasia in infants has gained acceptance world over. The ability of US to see the femoral head and acetabulum when they are composed of unossified hyaline cartilage is a clear advantage over conventional radiographs. In older children, a well-formed ossific nucleus in the femoral head prevents adequate imaging of the acetabulum and radiographic evaluation is then preferred. US of the hip is practical only upto 1 y of age, unless there is delayed ossification of the femoral head [1, 3].
DDH is a malformation of the ball and socket joint of the hip which ranges from mild acetabular dysplasia and a reducible subluxation to irreducible subluxation and dislocation of the
1. Alpha and Beta angles (Fig. 1): Alpha angle denotes slope of the bony acetabulum and is normally greater than 600. Alpha angle less than 550 is considered abnormal. Graf’s classification system grades hips from Type 1 - mild acetabular dysplasia (Fig. 2) through to Type 4 - irreducible dislocation of femoral head (Fig. S1). Beta angle measures slope of unossified acetabulum and increases with displacement of the labrum by the subluxated femoral head. It is not widely used in clinical practice.
Fig. 2 a On Coronal view, baseline is drawn tangential to the iliac wing and projected through the femoral head. D (yellow line) indicates the maximum diameter of the femoral head; d (double arrow) is measured
from the baseline to medial aspect of the femoral head. Normal D/d ratio is 50 %. b In an unstable hip, application of stress maneuver showing lateral subluxation of the femoral head with reduction of D/d to 32 %
Developmental Dysplasia of the Hip (DDH)
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2. Femoral head coverage (FHC) or D/d ratio (Fig. 2a): The lower limit of FHC in infants more than 1 mo is 50 %.
A dynamic evaluation is essential in the initial examination for DDH but discouraged during follow-up in the midst of treatment with abduction splinting. In dynamic evaluation, movement of the femoral head out of the acetabulum is analyzed and quantified (Fig. 2b). Stress application is similar to the provocative Barlow’s test (hip in flexion, abduction with gentle posterior push). Reduction of the head is studied by movements similar to the Ortolani’s test (gradual abduction of the flexed hip till the head reduces). US in first 4 wk of life often reveals minor degrees of instability and acetabular immaturity i.e., ‘Functional immaturity of hips’. Nearly all of these resolve on follow-up; thus it is recommended that US studies be performed when infants are 4–6 wk of age. US Evaluation of Hip Effusion Imaging work-up of a child with painful hip begins with a plain radiograph. Presence of effusion is a valuable but nonspecific indicator of joint pathology. US can detect very small amounts of intra-articular fluid and rules out other causes like subcutaneous edema, abscesses, tenosynovitis [4, 5]. A quick contralateral comparison is an added advantage (Fig. 3a). A hip effusion with internal echoes, synovial irregularity and capsular thickening suggests septic arthritis (Fig. 3b). US cannot always differentiate between septic, traumatic and sterile effusions and guided diagnostic and therapeutic aspirations can be undertaken. Follow-up US showing reduction in joint effusion indicates positive response to therapy.
Fig. 3 a US in a child with right hip pain showing a small effusion with increased thickness of the iliofemoral recess. Quick comparison with the asymptomatic left side. b US in a child with right hip pain and high fever showing a large effusion with irregular synovial thickening and thick fluid with internal echoes as seen in septic arthritis
Other Congenital Abnormalities Musculoskeletal Infections Proximal Focal Femoral Deficiency (PFFD) US can differentiate between different types of PFFD by confirming presence of a cartilaginous femoral head and its connection with the shaft [6].
US is the primary imaging modality in infections of soft tissues, muscles and joint spaces. In osteomyelitis, it is an additional study to look for fluid collections.
Congenital Hyperextension of the Knee in Neonates
Cellulitis
To assess relationship of the femur and tibia at rest and also demonstrate subluxation or dislocation of the tibia with motion (Fig. S2) [7].
US shows increased thickness and echogenicity of subcutaneous soft tissues and small areas of poorly defined fluid collection. Sometimes hypoechoic striations are seen due to inflammatory exudates dissecting through tissue planes (Fig. 4), with hyperemia of the affected tissues on CD [9, 10]. US helps to evaluate the extent of clinically apparent cellulitis, assess complications like abscess formation and in guided aspirations.
Congenital Talipes Equino Varus US has been used successfully to study correction during Ponsetti treatment [8].
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Fig. 4 Cellulitis showing thickened subcutaneous tissues with hypoechoic striations due to inflammatory exudates dissecting through the tissue planes
Necrotizing Fasciitis It is a rare infection occurring mostly in immuno-compromised patients, which spreads along the fascial planes with involvement of the deep fascia and muscles and severe systemic toxicity. US appearances are similar to cellulitis with fascial thickening, poorly-defined or absent fascial boundaries between the soft tissues and underlying muscles and localized fluid collections along the fascia [11]. Potentially a life-threatening condition, early recognition and differentiation from cellulitis is crucial. Further evaluation with cross-sectional imaging such as CT or MRI is indicated to establish involvement of deep fascia.
Abscesses Localized suppurative changes are seen on US as hypoechoic pus collections with well-defined or poorly-defined margins, internal echoes and septations (Fig. S3). CD shows hyperemia in the walls and absence of flow in the necrotic areas. Presence
Fig. 6 Cysticercosis: Thin walled anechoic intramuscular cyst with a central echogenic scolex (arrow) within is characteristic of cysticercosis. The surrounding muscle shows an altered hypoechoic echotexture secondary to inflammatory changes
of reflective specks indicates presence of gas [9]. US-guided therapeutic drainage can also be attempted. Pyomyositis Infection of muscle mass with abscess formation most commonly affects the thigh, calf and buttock muscles. It may occur following local trauma or in immunocompromised patients. US appearance in initial stages is of thickened echogenic muscle with loss of the normal fibrillary pattern and interspaced ill-defined hypoechoic areas [12]. In later stages, abscess formation with intramuscular fluid collection (Fig. 5) and increased peripheral flow on CD is seen. Parasitic infections like cysticercosis can also cause an intramuscular inflammation (Fig. 6). Osteomyelitis Typically metaphyses of long bones are involved with infection spreading along the medullary cavity, subperiosteal space
Fig. 5 Pyomyositis (a) Normal fibrillary pattern of the vastus lateralis muscle for comparison (b and c) Mildly thickened vastus medialis muscle with an ill defined hypoechoic area within suggesting myositis (arrow)
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and into soft tissues. MRI is ideal for early visualization of both osseous and soft tissue involvement. In initial stages, the US findings are non-specific with soft tissue swelling around the involved bone. As US does not penetrate the bone, osseous involvement is not seen and hence a normal US does not exclude an osteomyelitis. In later stages, fluid collections with internal echoes are seen partly subperiosteal, with a convex periosteal elevation and extending along the long axis of the bone [12] (Fig. 7a and b). Cortical irregularity and destruction may also be seen (Fig. S4) [12]. Surrounding hypoechoic soft tissue collections with internal debris and septations are seen extending parallel to the long axis of the bone (Fig. S4). In chronic osteomyelitis, soft tissue collections and sinuses can also be demonstrated. Tuberculosis can present as a chronic osteomyelitis or infective arthritis, with secondary soft tissue involvement and cold abscess formation (Fig. S5) [13]. Osteomyelitis and septic arthritis often coexist in the younger age group especially, neonates. Presence of joint fluid, synovial thickening and hyperemia on CD are seen in septic arthritis (Fig. 3b). Infectious Tenosynovitis Infection of tendon sheaths most often involves digital flexor sheaths of the hand and wrist [12, 14] and follows a penetrating injury.US shows presence of pus within the tendon sheath with associated thickening of the tendon and hyperemia on CD due to tendonitis. In some cases a foreign body may be visualized and removed under US-guidance. Bursitis It is seen as fluid collection in expected location of bursae with or without wall thickening and hyperemia on CD. US cannot differentiate between infectious and
Fig. 7 Osteomyelitis (a and b) Convex periosteal elevation (straight arrows) extending along the long axis of the bone is typical of a subperiosteal collection. Surrounding soft tissue abscess extending on either side
Fig. 8 Hypoechoic thickening of the tendon sheaths and fluid surrounding the tendons in tenosynovitis of the wrist in a case of JRA
non-infectious bursitis and a diagnostic US-guided aspiration may be helpful. Non Infectious Tenosynovitis and Bursitis US findings of tenosynovitis are often similar in infection, inflammatory arthropathies like Juvenile rheumatoid arthritis (JRA) and overuse syndromes where cumulative microtrauma leads to inflammation of tendon and tendon sheaths. Thickening of the tendon and tendon sheath with presence of fluid surrounding the tendon (Fig. 8) and hyperemia on CD are salient features [15]. Inflammatory bursitis has similar US features as an infectious bursitis. Synovitis US shows fluid collection in the joint with synovial thickening (Fig. S6) and hyperemia on CD similar to infective synovitis (Fig. 9) [15, 16], and laboratory workup and guided diagnostic aspiration help in determining etiology. Focal synovial thickening is seen as irregularity and focal nodular
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buttocks and elbow. History of trauma may not always be present especially in athletic teenagers. In early stages (7– 14 d) an oval hypoechoic intramuscular mass with a thin echogenic rim is seen [18], US appearance similar to a hematoma or abscess. This is followed by typical peripheral or internal calcifications and dense acoustic shadowing in the mature phase [18]. Myositis ossificans may sometimes be misdiagnosed as a malignant mass such as rhabdomyosarcoma and a correlation with plain radiographs and if required, MRI can help in differentiation. Fig. 9 Suprapatellar bursitis with synovitis in a patient with JRA: Suprapatellar bursal fluid showing internal echoes and septae
Fractures
Formation of heterotopic ossification, often close to the parent bone following direct trauma, occurs commonly in the thigh,
US appearance of a fracture is seen as discontinuity of the echogenic cortex (Fig. 11). US helps in detecting subtle fractures which are difficult to see on plain radiographs [19]. US can also detect new bone formation before it is evident on plain radiographs and has been used in bone lengthening techniques. Associated complications like hematomas, tendinous and nerve disruption, pseudoaneurysms, arteriovenous fistulas can also be diagnosed. Fracture separation of the distal humeral epiphysis (Salter Harris type I fracture) in newborns is a rare entity, usually following traumatic delivery. On radiographs it mimics elbow dislocation due to the absence of epiphyseal ossification. The ability of US to clearly visualize the cartilaginous distal humeral and proximal radial epiphyses (Fig. 12a) makes it an important diagnostic tool [20]. In distal humeral fracture separation, the distal humeral epiphysis and proximal radial epiphysis are visualized as one unit, together displaced medially and posteriorly, in relation to distal shaft of humerus (Fig. 12b). This is in contrast to elbow dislocation where distal humeral shaft and epiphysis together are displaced from the proximal radial epiphysis with disruption of radiocapitellar articulation (Fig. 12c).
Fig. 10 Normal muscle of the left arm (line arrow) and an intramuscular hematoma in the right arm seen as a heterogeneous ill defined echogenic area (open arrow)
Fig. 11 US in a newborn with incessant crying and inability to move the right leg shows a fracture with discontinuity of the echogenic cortex (arrow) in mid femoral diaphysis and associated soft tissue hematoma
projections into the joint cavity and, though rare in children the possibility of a pigmented villo-nodular synovitis needs to be considered [17].
Trauma Hematoma Blunt or penetrating trauma is the commonest cause of soft tissue hematoma. Other causes include bleeding diathesis and anticoagulant therapy. US appearance of hematoma varies with age of the bleed, with acute hematoma appearing as an ill-defined mass with increased echogenicity (Fig. 10). Within weeks the hematoma liquefies and appears heterogeneous with internal echoes and septations. Myositis Ossificans
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Fig. 12 a Normal elbow b Transphyseal separation of distal humeral epiphysis: where the epiphysis of the distal humerus is separated from the metaphysis and the radiocapitellar articulation remains intact. c
Dislocation of elbow: where the distal shaft of the humerus and epiphysis together separate from proximal radial epiphysis and radiocapitellar articulation is disrupted
Similarly slipped capital femoral epiphysis, a common Salter Harris type I injury of hip occurring in adolescents can be identified on US by measuring width of the physeal step [21].
tendon trauma in children involves the tendo-osseous junction (Fig. 14). Acute injuries may result in partial or complete detachment of the apophysis at the tendinous insertion with physeal widening and associated soft tissue abnormalities [24]. US has great advantage as it allows dynamic examination. Chronic injuries (repeated microtrauma) lead to osseous or cartilage fragmentation and calcification which are seen on US (Fig. 15) [24]. Ligament injuries in adolescents are seen as full thickness tears with interruption of the ligamentous fibers and partial tears with thickened irregular ligaments surrounded by fluid.
Pulled Elbow In this condition the annular ligament slips over the radial head resulting in rotational instability of radiocapitellar joint. US can identify this by measuring the increased radiocapitellar distance when the arm is pronated [22] and also visualize the thickened or torn annular ligament (Fig. 13) [22, 23].
Other Musculoskeletal Conditions Tendons and Ligaments Limb Enlargement Unlike in adults, the weakest point of muscle-tendon-bone unit is not the myotendinous junction, but the attachment of the tendon to the non-ossified cartilage. Hence, most Fig. 13 Pulled elbow: Anterior transverse US at the level of the radial neck reveals an echogenic band seen anterior to the radial head which represents the normal annular ligament on the right side. On the symptomatic left side, this appears to be thickened and hypoechoic
US with CD can differentiate vascular abnormalities like hemangiomas and vascular malformations from other soft
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Vascular Masses
Fig. 14 Hamstring tear: US examination of the ischial tuberosity in child reveals hypoechoic fluid collection at the tendo-osseous junction of the hamstring tendon suggesting a tear
tissue causes of limb enlargement like hemihypertrophy and Beckwith –Weidmann syndrome. A rare cause of limb enlargement, lipofibromatosis [25] presents as diffuse echogenic soft tissue mass composed of fibrofatty tissue (Fig. 16). Soft Tissue Masses US plays an important role in the initial evaluation and characterization of soft tissue masses. US evaluation includes confirming the presence of a mass vs. pseudo mass, determining its origin, size and morphology to help in narrowing a differential diagnosis and assessing whether a mass is more likely to be benign or malignant. CD helps in identifying vascular lesions, differentiating solid vs. cystic lesions and determining vascular pattern of solid masses which aids in predicting their nature. MRI is superior in further characterization and determining the extent of larger lesions.
Infantile hemangioma is the most common childhood tumor and US is widely used in its diagnosis, as it can avoid an MRI that needs anesthesia in most children. Hemangiomas are infantile and congenital and the imaging appearance and vascularity varies with the phase of evolution. In the proliferative phase, US appearance is usually that of a well-defined soft tissue mass of variable echogenecity with a high-vessel density on CD (Fig. 17) [26]. Variable amount of fibrofatty infiltration is seen in the involuting phase. According to the new ISSVA (International Society for the Study of Vascular Anomalies Classification System) classification, vascular malformations are divided into slow-flow and high-flow lesions. Presence of prominent feeding arteries, draining veins and arteriovenous shunting differentiates high-flow arteriovenous malformations from hemangiomas [27]. Differentiating the two is important since the treatment options differ. Slow-flow malformations include venous, capillary, lymphatic and mixed malformations. Venous malformations are seen as well-circumscribed, spongelike vascular spaces or poorly marginated collections of veins [27]. Presence of calcified phleboliths within invariably indicates a venous malformation. Capillary malformations present clinically as the classical port-wine stain and rarely warrant imaging. Lymphatic malformations have been described below. Vascular aneurysms and pseudoaneurysms are seen as cystic structures arising from and communicating with the underlying vessel which can be confirmed on CD. Non Vascular Solid Masses Enlarged lymph nodes, a common cause of pediatric palpable masses can easily be identified and characterized on US. Normal lymph nodes appear as flattened hypoechoic structures with varying amounts of hilar fat on US [28, 29]. Most inflammatory nodes appear rounded, hypoechoic with a maintained hilar vascularity on CD (Fig. S7) [30] and malignant nodes are associated with increased peripheral vascularity [30]. Surrounding inflammation favors an inflammatory lymphadenopathy and conglomeration favors a tuberculous etiology [30]. Associated cold abscesses may also arise from tuberculous nodes [13]. Subcutaneous Lipomas
Fig. 15 US in a child with recurrent tibial tuberosity pain reveals multiple echogenic calcific fragments at the tibial insertion of the patellar tendon and fluid in the infrapatellar bursa (arrow) as is seen in Osgood Schlater’s
They are typically well encapsulated masses brighter than surrounding muscle on US, compressible on transducer pressure with a paucity of vessels on CD (Fig. 18). Deep seated
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Fig. 16 US in a neonate with painless limb enlargement revealed a diffuse thickening of the subcutaneous tissues involving almost the entire lower limb with a predominant echogenic fatty appearance. Few
hypointense septae were seen within. No internal vascularity on CD. Subsequent MRI confirmed both fibrous and fatty tissue within this area suggesting a lipofibromatosis
lipomas have a firmer consistency and may appear more hypoechoic, often similar to the muscle [31]. Peripheral nerve sheath tumors appear as well marginated hypoechoic masses with continuity with the involved nerve (Fig. S8) [32].
Malignant Tumors
Non Vascular Cystic Masses US is ideal for differentiating solid from cystic masses. Lymphatic malformations are common cystic masses in the pediatric age group, mostly occuring in the neck. US appearance is a multi-septated avascular cystic lesion often large in size with fluid levels and septae of variable thickness. Septal vascularity may been seen (Fig. 19) [27, 33]. Intraarticular and periarticular cystic masses are also common usually around the knee joint (Fig. S9) and include parameniscal cysts, ganglion cysts and the most common periarticular cyst is the Baker’s cyst with deeper intraarticular communication.
Rhabdomyosarcomas are solid hypo to isoechoic masses with well-defined or invasive margins and increased vascularity on CD. Imaging features of rhabdomyosarcoma and other sarcomas are non-specific and benign processes i.e., acute hematomas, abscesses and benign neoplasms, can also have a similar appearance (Fig. 20) and tissue sampling is needed for a specific histologic diagnosis [6]. Other tumors are fibrosarcoma, synovial cell sarcoma, malignant histiocytoma, neurofibrosarcoma and Ewing’s sarcoma with large extraskeletal component (Fig. 21).
Spinal Ultrasound (SUS) SUS is becoming increasingly accepted as a first line screening test in neonates with lower spinal cutaneous stigmata and suspected of spinal dysraphism. Posterior elements are unossified in newborns, allowing an excellent imaging of
Fig. 17 Chest wall hemangioma in a 7-mo-old child seen as an echogenic lesion with a high vessel density on CD
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Fig. 18 Subcutaneous lipoma seen as a well marginated echogenic lesion
intraspinal contents. The advent of new-generation US machines with high-frequency Lenier array transducers and extended field-of-view capability now permit diagnostic sensitivity equal to MRI imaging in young babies. However advancing age and ossification of the posterior elements limits visualization. Results are best upto 6 mo of age. On US, the Spinal cord is seen as a hypoechoic tubular structure with an echogenic central canal surrounded by subarachnoid space and dura (Fig. 22). The cord tapers to form the conus medullaris, which continues as the echogenic cord-like filum terminale into the distal sacral canal and is surrounded by echogenic nerve roots (Fig. 22). A conus below the level of L2-3 is diagnostic of a tethered cord. In addition, on real-time scanning there is reduction in amplitude or loss of oscillation of the cord and cauda equina [34, 35]. Spinal Dysraphism
Fig. 19 Multiseptated cystic subcutaneous mass with no perfusion seen on CD; US findings typical of a lymphatic malformation
Spina-bifida-aperta, a non-skin covered open defect, is usually clinically apparent and imaging is limited. A cranial US to look for associated defects like hydrocephalus is usually done. SUS is excellent in evaluation of occult spinal dyspraphism. Skin covered lesions with subcutaneous mass like simple meningocele (Fig. 23a), lipomyelocele, lipomeningocele (Fig. 23b) and myelocystocele [35, 36] are visualized in detail. Skin covered lesions without subcutaneous mass including caudal-mass anomalies like thick filum terminale, fibrolipoma of filum terminale (Fig. 24), caudal regression syndrome,
Fig. 20 Clinically a hard lump felt in the right thigh. US showing a hypoechoic solid intramuscular mass with an irregular anterior margin and increased vascularity seen on CD. Differentials include an
inflammatory lesion/neoplasm. MRI done to rule out neoplastic lesion, revealed similar findings. Histopathology showing a granulomatous lesion
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spine is equivalent to MRI in experienced hands [37]. SUS can characterize nearly all spinal anomalies sufficiently in the early neonatal period. This allows clinical determination of whether the lesion requires urgent intervention or further radiologic evaluation with studies such as MRI can be delayed until therapeutic intervention is more imminent [35, 36].
Conclusions
Fig. 21 Clinically, a hard lump felt in the hypoechoic solid soft tissue mass arising (marked as B) with spiculated echogenic periosteal reaction (arrow). CD shows confirmed Ewing’s sarcoma with large component
right thigh. US showing a from the underlying bone areas within suggesting a vascularity within. MRI extra osseous soft tissue
sacrococcygeal teratoma (Fig. 25) and anomalies of the cord like a split-cord and diastomatomyelia (Fig. 26) can be seen [35, 36]. US also helps in detecting tumors, vascular malformations and cases of trauma. Advantage of SUS is that it can be performed portably and needs no sedation. Real-time imaging visualizes oscillation of the cord and nerve roots, anteroposterior and longitudinal movement of the cord during crying and flexion and extension of the spine. The sensitivity of SUS in evaluating neonatal
Fig. 22 Spinal cord is seen as a hypoechoic tubular structure with an echogenic center representing the central canal. Anteriorly is the anterior subarachnoid space, anterior dura and the vertebral bodies. Posteriorly is the posterior subarachnoid space and posterior dura. The cord tapers to form the conus medullaris, which continues as the echogenic cord like filum terminale (arrow) into the distal sacral canal and is surrounded by echogenic nerve roots
US is a portable, fast, simple, non-invasive imaging modality which does not involve radiation to the patient, does not require sedation, allows high-resolution and above all, is a dynamic imaging of the soft tissues, non–ossified cartilaginous and vascular structures, making it a ideal modality for evaluation of the MSK diseases in the pediatric age group. A quick comparison with the contralateral asymptomatic side is an added advantage. Some applications are typical to the pediatric age group like infant hip in DDH, hip joint effusion, epiphyseal trauma and evaluation of the neonatal spine. Other applications are a transition from the adult applications. The sensitivity of SUS in evaluating neonatal spine is equivalent to MRI in experienced hands, however limited in older children after the posterior spinal elements ossify. The diagnostic yield of US is directly related to the experience of the sonologist and this operator dependency is one of the limitations of US. The other limitation is inability to penetrate bone, limiting the diagnosis of intra-osseous pathology.
Indian J Pediatr Fig. 23 Skin covered lesion with a mass in lower lumbar region: a Predominantly fluid filled mass suggesting a small meningocele b Presence of echogenic fat within the mass (arrow) suggests a lipomeningocele
Fig. 24 Tethered cord with an echogenic lipoma of the filum terminale (arrow)
Fig. 25 Sacrococcygeal teratoma-Type II- a Scanning posteriorly in the left gluteal region shows predominant external mass (M). b Pelvic component seen in presacral region (M)
Fig. 26 Transverse section of the spinal cord: a Normal comparison b Diastomatomyelia with a classic spitting of the cord
Indian J Pediatr Acknowledgments The authors appreciate help of Dr. Ashwin Lawande for his contribution to a few images in the musculoskeletal trauma section.
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18. Contributions Article composed, written and finalized by ASK. Section on musculoskeletal trauma contributed by AJ. Section on musculoskeletal infections and mass lesions and formatting of article, references and images done by AK. ASK will act as guarantor for the paper. Compliance with Ethical Standards Conflict of Interest None.
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Source of Funding None 22.
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References 24. 1.
2.
3. 4. 5. 6.
7.
8.
9. 10. 11. 12. 13.
14. 15.
16.
Graf R The diagnosis of congenital hip-joint dislocation by the ultrasonic combound treatment. Arch Orthop Trauma Surg. 1980;97:117–33. Harcke HT, Clarke NM, Lee MS, Borns PF, MacEwen GD. Examination of the infant hip with real-time ultrasonography. J Ultrasound Med. 1984;3:131–7. Novick G, Ghelman B, Schneider M. Sonography of the neonatal and infant hip. AJR Am J Roentgenol. 1983;141:639–45. Karnik A Hip utrasonography in infants and children. Indian J Radiol Imaging. 2007;17:280–9. Alexander JE, Seibert JJ, Glasier CM, et al. High-resolution hip ultrasound in the limping child. J Clin Ultrasound. 1989;17:19–24. Siegel MJ. Musculoseletal system & vascular imaging. In: Siegel MJ, editor. Pediatric sonography. 4th edition. Philadelphia: Lippincott Williams; 2011. p. 613–5, 24. ISBN 978-1-60547-665-0. Siegel MJ. Musculoseletal system & vascular imaging. In: Siegel MJ, editor. Pediatric sonography. 3rd Edition. Philadelphia: Lippincott Williams; 2002. p. 643. ISBN 0-7817-2753-7. Desai S, Aroojis A, Mehta R. Ultrasound evaluation of clubfoot correction during ponseti treatment: a preliminary report. J Pediatr Orthop. 2008;28:53–9. Bureau NJ, Chhem RK, Cardinal E. Musculoskeletal infections: US manifestations. Radiographics. 1999;19:1585–92. Chao HC, Lin SJ, Huang YC, Lin TY. Sonographic evaluation of cellulitis in children. J Ultrasound Med. 2000;19:743–9. Chao HC, Kong MS, Lin TY. Diagnosis of necrotizing fasciitis in children. J Ultrasound Med. 1999;18:277–81. Chau CL, Griffith JF. Musculoskeletal infections: ultrasound appearances. Clin Radiol. 2005;60:149–59. De Backer AI, Vanhoenacker FM, Sanghvi DA. Imaging features of extraaxial musculoskeletal tuberculosis. Indian J Radiol Imaging. 2009;19:176–86. Canoso JJ, Barza M. Soft tissue infections. Rheum Dis Clin N Am. 1993;19:293–309. Ramos PC, Ceccarelli F, Jousse-Joulin S. Role of ultrasound in the assessment of juvenile idiopathic arthritis. Rheumatology (Oxford). 2012;51:vii10–2. Sureda D, Quiroga S, Arnal C, Boronat M, Andreu J, Casas L. Juvenile rheumatoid arthritis of the knee: evaluation with US. Radiology. 1994;190:403–6.
25.
26.
27.
28. 29. 30. 31.
32.
33. 34.
35.
36.
37.
Neubauer P, Weber AK, Miller NH, McCarthy EF. Pigmented villonodular synovitis in children: a report of six cases and review of the literature. Iowa Orthop J. 2007;27:90–4. Abate M, Salini V, Rimondi E, et al. Post traumatic myositis ossificans: sonographic findings. J Clin Ultrasound. 2011;39: 135–40. Graif M, Stahl-Kent V, Ben-Ami T, Strauss S, Amit Y, Itzchak Y. Sonographic detection of occult bone fractures. Pediatr Radiol. 1988;18:383–5. Jacobsen S, Hansson G, Nathorst-Westfelt J. Traumatic separation of the distal epiphysis of the humerus sustained at birth. J Bone Joint Surg (Br). 2009;91:797–802. Kallio PE, Lequesne GW, Paterson DC, Foster BK, Jones JR. Ultrasonography in slipped capital femoral epiphysis. Diagnosis and assessment of severity. J Bone Joint Surg (Br). 1991;73:884–9. Kosuwon W, Mahaisavariya B, Saengnipanthkul S, Laupattarakasem W, Jirawipoolwon P. Ultrasonography of pulled elbow. J Bone Joint Surg (Br). 1993;75:421–2. Kim MC, Eckhardt BP, Craig C, Kuhns LR. Ultrasonography of the annular ligament partial tear and recurrent "pulled elbow". Pediatr Radiol. 2004;34:999–1004. Vandervliet EJ, Vanhoenacker FM, Snoeckx A, Gielen JL, Van Dyck P, Parizel PM. Sports-related acute and chronic avulsion injuries in children and adolescents with special emphasis on tennis. Br J Sports Med. 2007;41:827–31. Greene AK, Karnes J, Padua HM, Schmidt BA, Kasser JR, Labow BI. Diffuse lipofibromatosis of the lower extremity masquerading as a vascular anomaly. Ann Plast Surg. 2009;62:703–6. Dubois J, Garel L, David M, Powell J. Vascular soft-tissue tumors in infancy: distinguishing features on Doppler sonography. AJR Am J Roentgenol. 2002;178:1541–5. Navarro OM, Laffan EE, Ngan BY. Pediatric soft-tissue tumors and pseudo-tumors: MR imaging features with pathologic correlation: part 1. Imaging approach, pseudotumors, vascular lesions, and adipocytic tumors. Radiographics. 2009;29:887–906. Torabi M, Aquino SL, Harisinghani MG. Current concepts in lymph node imaging. J Nucl Med. 2004;45:1509–18. Ying M, Ahuja A. Sonography of neck lymph nodes. Part I: normal lymph nodes. Clin Radiol. 2003;58:351–8. Ahuja A, Ying M. Sonography of neck lymph nodes. Part II: abnormal lymph nodes. Clin Radiol. 2003;58:359–66. Paunipagar BK, Griffith JF, Rasalkar DD, Chow LT, Kumta SM, Ahuja A. Ultrasound features of deep-seated lipomas. Insights Imaging. 2010;1:149–53. Reynolds DL Jr, Jacobson JA, Inampudi P, Jamadar DA, Ebrahim FS, Hayes CW. Sonographic characteristics of peripheral nerve sheath tumors. AJR Am J Roentgenol. 2004;182:741–4. Kapoor R, Saha MM, Talwar S. Sonographic appearances of lymphangiomas. Indian Pediatr. 1994;31:1447–50. Hill CA, Gibson PJ. Ultrasound determination of the normal location of the conus medullaris in neonates. AJNR Am J Neuroradiol. 1995;16:469–72. Lowe LH, Johanek AJ, Moore CW. Sonography of the neonatal spine: part 2, spinal disorders. AJR Am J Roentgenol. 2007;188: 739–44. Siegel MJ. Spinal ultrasound. In: Siegel MJ, editor. Pediatric sonography. 4th Edition. Philadelphia: Lippincott Williams; 2011. p. 647–75. ISBN 978–1-60547-665-0. American Institute of Ultrasound in Medicine; American College of Radiology; Society for Pediatric Radiology; Society of Radiologists in Ultrasound. AIUM practice guideline for the performance of an ultrasound examination of the neonatal spine. 2011. Available at: http://www.aium.org/resources/guidelines/neonatalspine.pdf).
REVIEW ARTICLE
Ultrasound Examination of Pediatric Musculoskeletal Diseases and Neonatal Spine Alka Sudhir Karnik 1
&
Alpana Karnik 2,3 & Alpana Joshi 4
Received: 31 May 2015 / Accepted: 8 November 2015 # Dr. K C Chaudhuri Foundation 2016
Abstract Ultrasound (US) is a simple, non-invasive imaging modality which allows high-resolution imaging of the musculoskeletal (MSK) system. Its increasing popularity in pediatrics is due to the fact that it does not involve radiation, has an ability to visualize non-ossified cartilaginous and vascular structures, allows dynamic imaging and quick contralateral comparison. US is the primary imaging modality in some pediatric MSK conditions like infant hip in developmental dysplasia (DDH), hip joint effusion, epiphyseal trauma and evaluation of the neonatal spine. US is the modality of choice in infants with DDH, both in the initial evaluation and posttreatment follow-up. US has a sensitivity equivalent to MRI in evaluation of the neonatal spine in experienced hands and is a good screening modality in neonates with suspected occult neural tube defects. In other MSK applications, it is often used for the initial diagnosis or in addition to other imaging modalities. In trauma and infections, US can often detect early and subtle soft tissue abnormalities and a quick comparison with the contralateral side aids in diagnoses. Dynamic imaging is crucial in evaluating congenital instabilities and dislocations,
Electronic supplementary material The online version of this article (doi:10.1007/s12098-015-1957-2) contains supplementary material, which is available to authorized users. * Alka Sudhir Karnik [email protected] 1
Department of Radiology, Dr Balabhai Nanavati Hospital, Mumbai, Maharashtra 400056, India
2
Sonosight Imaging Center, Mumbai, India
3
Department of Radiology, Holy Family Hospital, Mumbai, India
4
Shobha Diagnostic Center, Mumbai, India
soft tissue and ligamentous injuries, epiphyseal injuries and fracture separations. High-resolution imaging along with color Doppler (CD) is useful in the characterization of soft tissue masses. This article reviews the applications of US in pediatric MSK with emphasis on conditions where it is a primary modality. Limitations of US include inability to penetrate bone, hence, limited diagnosis of intraosseous pathology and operator dependency. Keywords Pediatric musculoskeletal ultrasound . Developmental dysplasia of the hip (DDH) . Epiphyseal injuries . Neonatal spine
Introduction Usage of ultrasound (US) in the evaluation of diseases of the musculoskeletal (MSK) system has gained considerable popularity. The ability of US to depict soft tissues, cartilaginous and vascular structures makes it an ideal modality in the pediatric age group and more so in neonates to visualize unossified cartilage. No radiation, better patient compliance, less need for sedation and real-time imaging with easy comparison of the contralateral side also makes US a favourable imaging modality. In addition, Color Doppler (CD) helps evaluate hyperemia in inflammatory and neoplastic conditions. Currently US is the primary modality of choice in evaluation of the neonatal hip for developmental dysplasia and to look for joint effusion. It is the initial modality in evaluation of general abnormalities involving muscles, tendons, joints, soft tissue tumors, foreign bodies and the neonatal spine. This article reviews the current role of US in imaging pediatric MSK diseases with emphasis on conditions where US is essential in making a diagnosis.
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Fig. 1 On Coronal view of the hip, three lines are drawn: Baseline tangential to the iliac wing; Acetabular roof line- joining the promontory to the deepest edge of the acetabulum; Labral line- drawn
from promontory to middle of fibrocartilaginous labrum. Alpha angle is the angle between the first and second lines and beta angle between the first and third lines
Hip Ultrasound
femoral head. There are two major components of DDH, instability and abnormal acetabular morphology. The static method assesses acetabular and femoral head morphology, location of the femoral head, appearance of the labrum and presence of fatty pulvinar in the hip joint. The dynamic method evaluates joint stability. Morphological evaluation of the infant hip incorporates two orthogonal views -coronal (Fig. 1) and transverse. Measurements are made on the coronal view, static images without stress.
The first successful application in MSK, hip US was introduced in the 1980’s by Graf in Germany [1] and by Harcke et al. in the United States [2], at about the same time. Today, use of real-time US to assess congenital dislocation and/or dysplasia in infants has gained acceptance world over. The ability of US to see the femoral head and acetabulum when they are composed of unossified hyaline cartilage is a clear advantage over conventional radiographs. In older children, a well-formed ossific nucleus in the femoral head prevents adequate imaging of the acetabulum and radiographic evaluation is then preferred. US of the hip is practical only upto 1 y of age, unless there is delayed ossification of the femoral head [1, 3].
DDH is a malformation of the ball and socket joint of the hip which ranges from mild acetabular dysplasia and a reducible subluxation to irreducible subluxation and dislocation of the
1. Alpha and Beta angles (Fig. 1): Alpha angle denotes slope of the bony acetabulum and is normally greater than 600. Alpha angle less than 550 is considered abnormal. Graf’s classification system grades hips from Type 1 - mild acetabular dysplasia (Fig. 2) through to Type 4 - irreducible dislocation of femoral head (Fig. S1). Beta angle measures slope of unossified acetabulum and increases with displacement of the labrum by the subluxated femoral head. It is not widely used in clinical practice.
Fig. 2 a On Coronal view, baseline is drawn tangential to the iliac wing and projected through the femoral head. D (yellow line) indicates the maximum diameter of the femoral head; d (double arrow) is measured
from the baseline to medial aspect of the femoral head. Normal D/d ratio is 50 %. b In an unstable hip, application of stress maneuver showing lateral subluxation of the femoral head with reduction of D/d to 32 %
Developmental Dysplasia of the Hip (DDH)
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2. Femoral head coverage (FHC) or D/d ratio (Fig. 2a): The lower limit of FHC in infants more than 1 mo is 50 %.
A dynamic evaluation is essential in the initial examination for DDH but discouraged during follow-up in the midst of treatment with abduction splinting. In dynamic evaluation, movement of the femoral head out of the acetabulum is analyzed and quantified (Fig. 2b). Stress application is similar to the provocative Barlow’s test (hip in flexion, abduction with gentle posterior push). Reduction of the head is studied by movements similar to the Ortolani’s test (gradual abduction of the flexed hip till the head reduces). US in first 4 wk of life often reveals minor degrees of instability and acetabular immaturity i.e., ‘Functional immaturity of hips’. Nearly all of these resolve on follow-up; thus it is recommended that US studies be performed when infants are 4–6 wk of age. US Evaluation of Hip Effusion Imaging work-up of a child with painful hip begins with a plain radiograph. Presence of effusion is a valuable but nonspecific indicator of joint pathology. US can detect very small amounts of intra-articular fluid and rules out other causes like subcutaneous edema, abscesses, tenosynovitis [4, 5]. A quick contralateral comparison is an added advantage (Fig. 3a). A hip effusion with internal echoes, synovial irregularity and capsular thickening suggests septic arthritis (Fig. 3b). US cannot always differentiate between septic, traumatic and sterile effusions and guided diagnostic and therapeutic aspirations can be undertaken. Follow-up US showing reduction in joint effusion indicates positive response to therapy.
Fig. 3 a US in a child with right hip pain showing a small effusion with increased thickness of the iliofemoral recess. Quick comparison with the asymptomatic left side. b US in a child with right hip pain and high fever showing a large effusion with irregular synovial thickening and thick fluid with internal echoes as seen in septic arthritis
Other Congenital Abnormalities Musculoskeletal Infections Proximal Focal Femoral Deficiency (PFFD) US can differentiate between different types of PFFD by confirming presence of a cartilaginous femoral head and its connection with the shaft [6].
US is the primary imaging modality in infections of soft tissues, muscles and joint spaces. In osteomyelitis, it is an additional study to look for fluid collections.
Congenital Hyperextension of the Knee in Neonates
Cellulitis
To assess relationship of the femur and tibia at rest and also demonstrate subluxation or dislocation of the tibia with motion (Fig. S2) [7].
US shows increased thickness and echogenicity of subcutaneous soft tissues and small areas of poorly defined fluid collection. Sometimes hypoechoic striations are seen due to inflammatory exudates dissecting through tissue planes (Fig. 4), with hyperemia of the affected tissues on CD [9, 10]. US helps to evaluate the extent of clinically apparent cellulitis, assess complications like abscess formation and in guided aspirations.
Congenital Talipes Equino Varus US has been used successfully to study correction during Ponsetti treatment [8].
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Fig. 4 Cellulitis showing thickened subcutaneous tissues with hypoechoic striations due to inflammatory exudates dissecting through the tissue planes
Necrotizing Fasciitis It is a rare infection occurring mostly in immuno-compromised patients, which spreads along the fascial planes with involvement of the deep fascia and muscles and severe systemic toxicity. US appearances are similar to cellulitis with fascial thickening, poorly-defined or absent fascial boundaries between the soft tissues and underlying muscles and localized fluid collections along the fascia [11]. Potentially a life-threatening condition, early recognition and differentiation from cellulitis is crucial. Further evaluation with cross-sectional imaging such as CT or MRI is indicated to establish involvement of deep fascia.
Abscesses Localized suppurative changes are seen on US as hypoechoic pus collections with well-defined or poorly-defined margins, internal echoes and septations (Fig. S3). CD shows hyperemia in the walls and absence of flow in the necrotic areas. Presence
Fig. 6 Cysticercosis: Thin walled anechoic intramuscular cyst with a central echogenic scolex (arrow) within is characteristic of cysticercosis. The surrounding muscle shows an altered hypoechoic echotexture secondary to inflammatory changes
of reflective specks indicates presence of gas [9]. US-guided therapeutic drainage can also be attempted. Pyomyositis Infection of muscle mass with abscess formation most commonly affects the thigh, calf and buttock muscles. It may occur following local trauma or in immunocompromised patients. US appearance in initial stages is of thickened echogenic muscle with loss of the normal fibrillary pattern and interspaced ill-defined hypoechoic areas [12]. In later stages, abscess formation with intramuscular fluid collection (Fig. 5) and increased peripheral flow on CD is seen. Parasitic infections like cysticercosis can also cause an intramuscular inflammation (Fig. 6). Osteomyelitis Typically metaphyses of long bones are involved with infection spreading along the medullary cavity, subperiosteal space
Fig. 5 Pyomyositis (a) Normal fibrillary pattern of the vastus lateralis muscle for comparison (b and c) Mildly thickened vastus medialis muscle with an ill defined hypoechoic area within suggesting myositis (arrow)
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and into soft tissues. MRI is ideal for early visualization of both osseous and soft tissue involvement. In initial stages, the US findings are non-specific with soft tissue swelling around the involved bone. As US does not penetrate the bone, osseous involvement is not seen and hence a normal US does not exclude an osteomyelitis. In later stages, fluid collections with internal echoes are seen partly subperiosteal, with a convex periosteal elevation and extending along the long axis of the bone [12] (Fig. 7a and b). Cortical irregularity and destruction may also be seen (Fig. S4) [12]. Surrounding hypoechoic soft tissue collections with internal debris and septations are seen extending parallel to the long axis of the bone (Fig. S4). In chronic osteomyelitis, soft tissue collections and sinuses can also be demonstrated. Tuberculosis can present as a chronic osteomyelitis or infective arthritis, with secondary soft tissue involvement and cold abscess formation (Fig. S5) [13]. Osteomyelitis and septic arthritis often coexist in the younger age group especially, neonates. Presence of joint fluid, synovial thickening and hyperemia on CD are seen in septic arthritis (Fig. 3b). Infectious Tenosynovitis Infection of tendon sheaths most often involves digital flexor sheaths of the hand and wrist [12, 14] and follows a penetrating injury.US shows presence of pus within the tendon sheath with associated thickening of the tendon and hyperemia on CD due to tendonitis. In some cases a foreign body may be visualized and removed under US-guidance. Bursitis It is seen as fluid collection in expected location of bursae with or without wall thickening and hyperemia on CD. US cannot differentiate between infectious and
Fig. 7 Osteomyelitis (a and b) Convex periosteal elevation (straight arrows) extending along the long axis of the bone is typical of a subperiosteal collection. Surrounding soft tissue abscess extending on either side
Fig. 8 Hypoechoic thickening of the tendon sheaths and fluid surrounding the tendons in tenosynovitis of the wrist in a case of JRA
non-infectious bursitis and a diagnostic US-guided aspiration may be helpful. Non Infectious Tenosynovitis and Bursitis US findings of tenosynovitis are often similar in infection, inflammatory arthropathies like Juvenile rheumatoid arthritis (JRA) and overuse syndromes where cumulative microtrauma leads to inflammation of tendon and tendon sheaths. Thickening of the tendon and tendon sheath with presence of fluid surrounding the tendon (Fig. 8) and hyperemia on CD are salient features [15]. Inflammatory bursitis has similar US features as an infectious bursitis. Synovitis US shows fluid collection in the joint with synovial thickening (Fig. S6) and hyperemia on CD similar to infective synovitis (Fig. 9) [15, 16], and laboratory workup and guided diagnostic aspiration help in determining etiology. Focal synovial thickening is seen as irregularity and focal nodular
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buttocks and elbow. History of trauma may not always be present especially in athletic teenagers. In early stages (7– 14 d) an oval hypoechoic intramuscular mass with a thin echogenic rim is seen [18], US appearance similar to a hematoma or abscess. This is followed by typical peripheral or internal calcifications and dense acoustic shadowing in the mature phase [18]. Myositis ossificans may sometimes be misdiagnosed as a malignant mass such as rhabdomyosarcoma and a correlation with plain radiographs and if required, MRI can help in differentiation. Fig. 9 Suprapatellar bursitis with synovitis in a patient with JRA: Suprapatellar bursal fluid showing internal echoes and septae
Fractures
Formation of heterotopic ossification, often close to the parent bone following direct trauma, occurs commonly in the thigh,
US appearance of a fracture is seen as discontinuity of the echogenic cortex (Fig. 11). US helps in detecting subtle fractures which are difficult to see on plain radiographs [19]. US can also detect new bone formation before it is evident on plain radiographs and has been used in bone lengthening techniques. Associated complications like hematomas, tendinous and nerve disruption, pseudoaneurysms, arteriovenous fistulas can also be diagnosed. Fracture separation of the distal humeral epiphysis (Salter Harris type I fracture) in newborns is a rare entity, usually following traumatic delivery. On radiographs it mimics elbow dislocation due to the absence of epiphyseal ossification. The ability of US to clearly visualize the cartilaginous distal humeral and proximal radial epiphyses (Fig. 12a) makes it an important diagnostic tool [20]. In distal humeral fracture separation, the distal humeral epiphysis and proximal radial epiphysis are visualized as one unit, together displaced medially and posteriorly, in relation to distal shaft of humerus (Fig. 12b). This is in contrast to elbow dislocation where distal humeral shaft and epiphysis together are displaced from the proximal radial epiphysis with disruption of radiocapitellar articulation (Fig. 12c).
Fig. 10 Normal muscle of the left arm (line arrow) and an intramuscular hematoma in the right arm seen as a heterogeneous ill defined echogenic area (open arrow)
Fig. 11 US in a newborn with incessant crying and inability to move the right leg shows a fracture with discontinuity of the echogenic cortex (arrow) in mid femoral diaphysis and associated soft tissue hematoma
projections into the joint cavity and, though rare in children the possibility of a pigmented villo-nodular synovitis needs to be considered [17].
Trauma Hematoma Blunt or penetrating trauma is the commonest cause of soft tissue hematoma. Other causes include bleeding diathesis and anticoagulant therapy. US appearance of hematoma varies with age of the bleed, with acute hematoma appearing as an ill-defined mass with increased echogenicity (Fig. 10). Within weeks the hematoma liquefies and appears heterogeneous with internal echoes and septations. Myositis Ossificans
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Fig. 12 a Normal elbow b Transphyseal separation of distal humeral epiphysis: where the epiphysis of the distal humerus is separated from the metaphysis and the radiocapitellar articulation remains intact. c
Dislocation of elbow: where the distal shaft of the humerus and epiphysis together separate from proximal radial epiphysis and radiocapitellar articulation is disrupted
Similarly slipped capital femoral epiphysis, a common Salter Harris type I injury of hip occurring in adolescents can be identified on US by measuring width of the physeal step [21].
tendon trauma in children involves the tendo-osseous junction (Fig. 14). Acute injuries may result in partial or complete detachment of the apophysis at the tendinous insertion with physeal widening and associated soft tissue abnormalities [24]. US has great advantage as it allows dynamic examination. Chronic injuries (repeated microtrauma) lead to osseous or cartilage fragmentation and calcification which are seen on US (Fig. 15) [24]. Ligament injuries in adolescents are seen as full thickness tears with interruption of the ligamentous fibers and partial tears with thickened irregular ligaments surrounded by fluid.
Pulled Elbow In this condition the annular ligament slips over the radial head resulting in rotational instability of radiocapitellar joint. US can identify this by measuring the increased radiocapitellar distance when the arm is pronated [22] and also visualize the thickened or torn annular ligament (Fig. 13) [22, 23].
Other Musculoskeletal Conditions Tendons and Ligaments Limb Enlargement Unlike in adults, the weakest point of muscle-tendon-bone unit is not the myotendinous junction, but the attachment of the tendon to the non-ossified cartilage. Hence, most Fig. 13 Pulled elbow: Anterior transverse US at the level of the radial neck reveals an echogenic band seen anterior to the radial head which represents the normal annular ligament on the right side. On the symptomatic left side, this appears to be thickened and hypoechoic
US with CD can differentiate vascular abnormalities like hemangiomas and vascular malformations from other soft
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Vascular Masses
Fig. 14 Hamstring tear: US examination of the ischial tuberosity in child reveals hypoechoic fluid collection at the tendo-osseous junction of the hamstring tendon suggesting a tear
tissue causes of limb enlargement like hemihypertrophy and Beckwith –Weidmann syndrome. A rare cause of limb enlargement, lipofibromatosis [25] presents as diffuse echogenic soft tissue mass composed of fibrofatty tissue (Fig. 16). Soft Tissue Masses US plays an important role in the initial evaluation and characterization of soft tissue masses. US evaluation includes confirming the presence of a mass vs. pseudo mass, determining its origin, size and morphology to help in narrowing a differential diagnosis and assessing whether a mass is more likely to be benign or malignant. CD helps in identifying vascular lesions, differentiating solid vs. cystic lesions and determining vascular pattern of solid masses which aids in predicting their nature. MRI is superior in further characterization and determining the extent of larger lesions.
Infantile hemangioma is the most common childhood tumor and US is widely used in its diagnosis, as it can avoid an MRI that needs anesthesia in most children. Hemangiomas are infantile and congenital and the imaging appearance and vascularity varies with the phase of evolution. In the proliferative phase, US appearance is usually that of a well-defined soft tissue mass of variable echogenecity with a high-vessel density on CD (Fig. 17) [26]. Variable amount of fibrofatty infiltration is seen in the involuting phase. According to the new ISSVA (International Society for the Study of Vascular Anomalies Classification System) classification, vascular malformations are divided into slow-flow and high-flow lesions. Presence of prominent feeding arteries, draining veins and arteriovenous shunting differentiates high-flow arteriovenous malformations from hemangiomas [27]. Differentiating the two is important since the treatment options differ. Slow-flow malformations include venous, capillary, lymphatic and mixed malformations. Venous malformations are seen as well-circumscribed, spongelike vascular spaces or poorly marginated collections of veins [27]. Presence of calcified phleboliths within invariably indicates a venous malformation. Capillary malformations present clinically as the classical port-wine stain and rarely warrant imaging. Lymphatic malformations have been described below. Vascular aneurysms and pseudoaneurysms are seen as cystic structures arising from and communicating with the underlying vessel which can be confirmed on CD. Non Vascular Solid Masses Enlarged lymph nodes, a common cause of pediatric palpable masses can easily be identified and characterized on US. Normal lymph nodes appear as flattened hypoechoic structures with varying amounts of hilar fat on US [28, 29]. Most inflammatory nodes appear rounded, hypoechoic with a maintained hilar vascularity on CD (Fig. S7) [30] and malignant nodes are associated with increased peripheral vascularity [30]. Surrounding inflammation favors an inflammatory lymphadenopathy and conglomeration favors a tuberculous etiology [30]. Associated cold abscesses may also arise from tuberculous nodes [13]. Subcutaneous Lipomas
Fig. 15 US in a child with recurrent tibial tuberosity pain reveals multiple echogenic calcific fragments at the tibial insertion of the patellar tendon and fluid in the infrapatellar bursa (arrow) as is seen in Osgood Schlater’s
They are typically well encapsulated masses brighter than surrounding muscle on US, compressible on transducer pressure with a paucity of vessels on CD (Fig. 18). Deep seated
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Fig. 16 US in a neonate with painless limb enlargement revealed a diffuse thickening of the subcutaneous tissues involving almost the entire lower limb with a predominant echogenic fatty appearance. Few
hypointense septae were seen within. No internal vascularity on CD. Subsequent MRI confirmed both fibrous and fatty tissue within this area suggesting a lipofibromatosis
lipomas have a firmer consistency and may appear more hypoechoic, often similar to the muscle [31]. Peripheral nerve sheath tumors appear as well marginated hypoechoic masses with continuity with the involved nerve (Fig. S8) [32].
Malignant Tumors
Non Vascular Cystic Masses US is ideal for differentiating solid from cystic masses. Lymphatic malformations are common cystic masses in the pediatric age group, mostly occuring in the neck. US appearance is a multi-septated avascular cystic lesion often large in size with fluid levels and septae of variable thickness. Septal vascularity may been seen (Fig. 19) [27, 33]. Intraarticular and periarticular cystic masses are also common usually around the knee joint (Fig. S9) and include parameniscal cysts, ganglion cysts and the most common periarticular cyst is the Baker’s cyst with deeper intraarticular communication.
Rhabdomyosarcomas are solid hypo to isoechoic masses with well-defined or invasive margins and increased vascularity on CD. Imaging features of rhabdomyosarcoma and other sarcomas are non-specific and benign processes i.e., acute hematomas, abscesses and benign neoplasms, can also have a similar appearance (Fig. 20) and tissue sampling is needed for a specific histologic diagnosis [6]. Other tumors are fibrosarcoma, synovial cell sarcoma, malignant histiocytoma, neurofibrosarcoma and Ewing’s sarcoma with large extraskeletal component (Fig. 21).
Spinal Ultrasound (SUS) SUS is becoming increasingly accepted as a first line screening test in neonates with lower spinal cutaneous stigmata and suspected of spinal dysraphism. Posterior elements are unossified in newborns, allowing an excellent imaging of
Fig. 17 Chest wall hemangioma in a 7-mo-old child seen as an echogenic lesion with a high vessel density on CD
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Fig. 18 Subcutaneous lipoma seen as a well marginated echogenic lesion
intraspinal contents. The advent of new-generation US machines with high-frequency Lenier array transducers and extended field-of-view capability now permit diagnostic sensitivity equal to MRI imaging in young babies. However advancing age and ossification of the posterior elements limits visualization. Results are best upto 6 mo of age. On US, the Spinal cord is seen as a hypoechoic tubular structure with an echogenic central canal surrounded by subarachnoid space and dura (Fig. 22). The cord tapers to form the conus medullaris, which continues as the echogenic cord-like filum terminale into the distal sacral canal and is surrounded by echogenic nerve roots (Fig. 22). A conus below the level of L2-3 is diagnostic of a tethered cord. In addition, on real-time scanning there is reduction in amplitude or loss of oscillation of the cord and cauda equina [34, 35]. Spinal Dysraphism
Fig. 19 Multiseptated cystic subcutaneous mass with no perfusion seen on CD; US findings typical of a lymphatic malformation
Spina-bifida-aperta, a non-skin covered open defect, is usually clinically apparent and imaging is limited. A cranial US to look for associated defects like hydrocephalus is usually done. SUS is excellent in evaluation of occult spinal dyspraphism. Skin covered lesions with subcutaneous mass like simple meningocele (Fig. 23a), lipomyelocele, lipomeningocele (Fig. 23b) and myelocystocele [35, 36] are visualized in detail. Skin covered lesions without subcutaneous mass including caudal-mass anomalies like thick filum terminale, fibrolipoma of filum terminale (Fig. 24), caudal regression syndrome,
Fig. 20 Clinically a hard lump felt in the right thigh. US showing a hypoechoic solid intramuscular mass with an irregular anterior margin and increased vascularity seen on CD. Differentials include an
inflammatory lesion/neoplasm. MRI done to rule out neoplastic lesion, revealed similar findings. Histopathology showing a granulomatous lesion
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spine is equivalent to MRI in experienced hands [37]. SUS can characterize nearly all spinal anomalies sufficiently in the early neonatal period. This allows clinical determination of whether the lesion requires urgent intervention or further radiologic evaluation with studies such as MRI can be delayed until therapeutic intervention is more imminent [35, 36].
Conclusions
Fig. 21 Clinically, a hard lump felt in the hypoechoic solid soft tissue mass arising (marked as B) with spiculated echogenic periosteal reaction (arrow). CD shows confirmed Ewing’s sarcoma with large component
right thigh. US showing a from the underlying bone areas within suggesting a vascularity within. MRI extra osseous soft tissue
sacrococcygeal teratoma (Fig. 25) and anomalies of the cord like a split-cord and diastomatomyelia (Fig. 26) can be seen [35, 36]. US also helps in detecting tumors, vascular malformations and cases of trauma. Advantage of SUS is that it can be performed portably and needs no sedation. Real-time imaging visualizes oscillation of the cord and nerve roots, anteroposterior and longitudinal movement of the cord during crying and flexion and extension of the spine. The sensitivity of SUS in evaluating neonatal
Fig. 22 Spinal cord is seen as a hypoechoic tubular structure with an echogenic center representing the central canal. Anteriorly is the anterior subarachnoid space, anterior dura and the vertebral bodies. Posteriorly is the posterior subarachnoid space and posterior dura. The cord tapers to form the conus medullaris, which continues as the echogenic cord like filum terminale (arrow) into the distal sacral canal and is surrounded by echogenic nerve roots
US is a portable, fast, simple, non-invasive imaging modality which does not involve radiation to the patient, does not require sedation, allows high-resolution and above all, is a dynamic imaging of the soft tissues, non–ossified cartilaginous and vascular structures, making it a ideal modality for evaluation of the MSK diseases in the pediatric age group. A quick comparison with the contralateral asymptomatic side is an added advantage. Some applications are typical to the pediatric age group like infant hip in DDH, hip joint effusion, epiphyseal trauma and evaluation of the neonatal spine. Other applications are a transition from the adult applications. The sensitivity of SUS in evaluating neonatal spine is equivalent to MRI in experienced hands, however limited in older children after the posterior spinal elements ossify. The diagnostic yield of US is directly related to the experience of the sonologist and this operator dependency is one of the limitations of US. The other limitation is inability to penetrate bone, limiting the diagnosis of intra-osseous pathology.
Indian J Pediatr Fig. 23 Skin covered lesion with a mass in lower lumbar region: a Predominantly fluid filled mass suggesting a small meningocele b Presence of echogenic fat within the mass (arrow) suggests a lipomeningocele
Fig. 24 Tethered cord with an echogenic lipoma of the filum terminale (arrow)
Fig. 25 Sacrococcygeal teratoma-Type II- a Scanning posteriorly in the left gluteal region shows predominant external mass (M). b Pelvic component seen in presacral region (M)
Fig. 26 Transverse section of the spinal cord: a Normal comparison b Diastomatomyelia with a classic spitting of the cord
Indian J Pediatr Acknowledgments The authors appreciate help of Dr. Ashwin Lawande for his contribution to a few images in the musculoskeletal trauma section.
17.
18. Contributions Article composed, written and finalized by ASK. Section on musculoskeletal trauma contributed by AJ. Section on musculoskeletal infections and mass lesions and formatting of article, references and images done by AK. ASK will act as guarantor for the paper. Compliance with Ethical Standards Conflict of Interest None.
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Source of Funding None 22.
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References 24. 1.
2.
3. 4. 5. 6.
7.
8.
9. 10. 11. 12. 13.
14. 15.
16.
Graf R The diagnosis of congenital hip-joint dislocation by the ultrasonic combound treatment. Arch Orthop Trauma Surg. 1980;97:117–33. Harcke HT, Clarke NM, Lee MS, Borns PF, MacEwen GD. Examination of the infant hip with real-time ultrasonography. J Ultrasound Med. 1984;3:131–7. Novick G, Ghelman B, Schneider M. Sonography of the neonatal and infant hip. AJR Am J Roentgenol. 1983;141:639–45. Karnik A Hip utrasonography in infants and children. Indian J Radiol Imaging. 2007;17:280–9. Alexander JE, Seibert JJ, Glasier CM, et al. High-resolution hip ultrasound in the limping child. J Clin Ultrasound. 1989;17:19–24. Siegel MJ. Musculoseletal system & vascular imaging. In: Siegel MJ, editor. Pediatric sonography. 4th edition. Philadelphia: Lippincott Williams; 2011. p. 613–5, 24. ISBN 978-1-60547-665-0. Siegel MJ. Musculoseletal system & vascular imaging. In: Siegel MJ, editor. Pediatric sonography. 3rd Edition. Philadelphia: Lippincott Williams; 2002. p. 643. ISBN 0-7817-2753-7. Desai S, Aroojis A, Mehta R. Ultrasound evaluation of clubfoot correction during ponseti treatment: a preliminary report. J Pediatr Orthop. 2008;28:53–9. Bureau NJ, Chhem RK, Cardinal E. Musculoskeletal infections: US manifestations. Radiographics. 1999;19:1585–92. Chao HC, Lin SJ, Huang YC, Lin TY. Sonographic evaluation of cellulitis in children. J Ultrasound Med. 2000;19:743–9. Chao HC, Kong MS, Lin TY. Diagnosis of necrotizing fasciitis in children. J Ultrasound Med. 1999;18:277–81. Chau CL, Griffith JF. Musculoskeletal infections: ultrasound appearances. Clin Radiol. 2005;60:149–59. De Backer AI, Vanhoenacker FM, Sanghvi DA. Imaging features of extraaxial musculoskeletal tuberculosis. Indian J Radiol Imaging. 2009;19:176–86. Canoso JJ, Barza M. Soft tissue infections. Rheum Dis Clin N Am. 1993;19:293–309. Ramos PC, Ceccarelli F, Jousse-Joulin S. Role of ultrasound in the assessment of juvenile idiopathic arthritis. Rheumatology (Oxford). 2012;51:vii10–2. Sureda D, Quiroga S, Arnal C, Boronat M, Andreu J, Casas L. Juvenile rheumatoid arthritis of the knee: evaluation with US. Radiology. 1994;190:403–6.
25.
26.
27.
28. 29. 30. 31.
32.
33. 34.
35.
36.
37.
Neubauer P, Weber AK, Miller NH, McCarthy EF. Pigmented villonodular synovitis in children: a report of six cases and review of the literature. Iowa Orthop J. 2007;27:90–4. Abate M, Salini V, Rimondi E, et al. Post traumatic myositis ossificans: sonographic findings. J Clin Ultrasound. 2011;39: 135–40. Graif M, Stahl-Kent V, Ben-Ami T, Strauss S, Amit Y, Itzchak Y. Sonographic detection of occult bone fractures. Pediatr Radiol. 1988;18:383–5. Jacobsen S, Hansson G, Nathorst-Westfelt J. Traumatic separation of the distal epiphysis of the humerus sustained at birth. J Bone Joint Surg (Br). 2009;91:797–802. Kallio PE, Lequesne GW, Paterson DC, Foster BK, Jones JR. Ultrasonography in slipped capital femoral epiphysis. Diagnosis and assessment of severity. J Bone Joint Surg (Br). 1991;73:884–9. Kosuwon W, Mahaisavariya B, Saengnipanthkul S, Laupattarakasem W, Jirawipoolwon P. Ultrasonography of pulled elbow. J Bone Joint Surg (Br). 1993;75:421–2. Kim MC, Eckhardt BP, Craig C, Kuhns LR. Ultrasonography of the annular ligament partial tear and recurrent "pulled elbow". Pediatr Radiol. 2004;34:999–1004. Vandervliet EJ, Vanhoenacker FM, Snoeckx A, Gielen JL, Van Dyck P, Parizel PM. Sports-related acute and chronic avulsion injuries in children and adolescents with special emphasis on tennis. Br J Sports Med. 2007;41:827–31. Greene AK, Karnes J, Padua HM, Schmidt BA, Kasser JR, Labow BI. Diffuse lipofibromatosis of the lower extremity masquerading as a vascular anomaly. Ann Plast Surg. 2009;62:703–6. Dubois J, Garel L, David M, Powell J. Vascular soft-tissue tumors in infancy: distinguishing features on Doppler sonography. AJR Am J Roentgenol. 2002;178:1541–5. Navarro OM, Laffan EE, Ngan BY. Pediatric soft-tissue tumors and pseudo-tumors: MR imaging features with pathologic correlation: part 1. Imaging approach, pseudotumors, vascular lesions, and adipocytic tumors. Radiographics. 2009;29:887–906. Torabi M, Aquino SL, Harisinghani MG. Current concepts in lymph node imaging. J Nucl Med. 2004;45:1509–18. Ying M, Ahuja A. Sonography of neck lymph nodes. Part I: normal lymph nodes. Clin Radiol. 2003;58:351–8. Ahuja A, Ying M. Sonography of neck lymph nodes. Part II: abnormal lymph nodes. Clin Radiol. 2003;58:359–66. Paunipagar BK, Griffith JF, Rasalkar DD, Chow LT, Kumta SM, Ahuja A. Ultrasound features of deep-seated lipomas. Insights Imaging. 2010;1:149–53. Reynolds DL Jr, Jacobson JA, Inampudi P, Jamadar DA, Ebrahim FS, Hayes CW. Sonographic characteristics of peripheral nerve sheath tumors. AJR Am J Roentgenol. 2004;182:741–4. Kapoor R, Saha MM, Talwar S. Sonographic appearances of lymphangiomas. Indian Pediatr. 1994;31:1447–50. Hill CA, Gibson PJ. Ultrasound determination of the normal location of the conus medullaris in neonates. AJNR Am J Neuroradiol. 1995;16:469–72. Lowe LH, Johanek AJ, Moore CW. Sonography of the neonatal spine: part 2, spinal disorders. AJR Am J Roentgenol. 2007;188: 739–44. Siegel MJ. Spinal ultrasound. In: Siegel MJ, editor. Pediatric sonography. 4th Edition. Philadelphia: Lippincott Williams; 2011. p. 647–75. ISBN 978–1-60547-665-0. American Institute of Ultrasound in Medicine; American College of Radiology; Society for Pediatric Radiology; Society of Radiologists in Ultrasound. AIUM practice guideline for the performance of an ultrasound examination of the neonatal spine. 2011. Available at: http://www.aium.org/resources/guidelines/neonatalspine.pdf).
