G Model EURR-5474; No. of Pages 8 ARTICLE IN PRESS European Journal of Radiology xxx (2011) xxx–xxx Contents lists available at ScienceDirect European Journal of Radiology journal homepage: www.elsevier.com/locate/ejrad Hip ultrasound Carlo Martinoli a,∗, Isabella Garello a, Alessandra Marchetti a, Federigo Palmieri a, Luisa Altafini a, Maura Valle b, Alberto Tagliafico c a Radiologia, DISC, Università di Genova, Largo Rosanna Benzi 8, I-16132 Genoa, Italy b Radiologia, Gaslini Children Hospital, Genova, Italy c Radiologia, National Institute for Cancer Research, Genoa, Italy article info abstract Article history: In newborns, US has an established role in the detection and management of developmental dys- Received 16 February 2011 plasia of the hip. Later in childhood, when the limping child is a major diagnostic dilemma, US is Accepted 22 March 2011 extremely helpful in the identification of the varied disease processes underlying this condition, as transient synovitis, septic arthritis, Perthes disease and slipped femoral capital epiphysis. In adoles- Keywords: cent practicing sporting activities, US is an excellent means to identify apophyseal injures about the Hip joint pelvic ring, especially when avulsions are undisplaced and difficult-to-see radiographically. Later on, in Ultrasound the adulthood, US is an effective modality to diagnose tendon and muscle injuries about the hip and Developmental dysplasia of the hip Irritable hip pelvis, identify effusion or synovitis within the hip joint or its adjacent bursae and guide the treatment Apophyseal injuries of these findings. The aim of this article is to provide a comprehensive review of the most common Hip tendon disorders pathologic conditions about the hip, in which the contribution of US is relevant for the diagnostic Hip joint synovitis work-up. US-guided interventional procedures © 2011 Elsevier Ireland Ltd. All rights reserved. Owing to its anatomic complexity, the hip is a challenging site specific clinical contexts in which US plays a key role in the diag- for evaluation with ultrasound (US). In children, US is the technique nosis and patient management. of choice for screening, diagnosis and treatment of developmental dysplasia of the hip, it plays an important role in the assessment of 1.1. Developmental dysplasia of the hip the irritable hip and hip infection as well as in detection of sporting injuries causing apophyseal avulsion about the pelvic ring. In the Developmental dysplasia of the hip is a condition involving adult population, US is increasingly used mainly to detect intraar- deformity of the acetabulum at various degrees, possibly lead- ticular joint effusion and to evaluate paraarticular masses, tendon ing to subluxation or dislocation of the femoral head [1]. The and nerve disorders. This article provides an overview of the role reported incidence of this condition accounts for approximately of US to examine a wide range of disorders about the hip that can 2–6:1000 live newborns [1]. Several constitutional (e.g., female occur in children and adults. gender, white race), mechanical (e.g., oligohydramnios, breech delivery) and functional (e.g., maternal estrogen levels, familiar- ity) factors seems to be predisposing. In the newborn, reducing 1. Paediatric hip a prenatal dislocation may lead a stable hip to develop. How- ever, if dislocation is not recognized early, some adaptive changes US is an extremely efficient imaging modality to examine the make the femoral head more difficult to reduce. An early diagno- paediatric hip, as an exquisite depiction of the immature skele- sis of developmental dysplasia of the hip is, therefore, critical for ton with large amounts of cartilaginous bone can be obtained in establishing a proper treatment [2]. Physical examination is based children in a well-tolerated and noninvasive way. In addition, this on inspection and two basic stress tests, the Ortolani and Barlow technique is very sensitive to detect hip joint effusion and can aid manoeuvres [1]. The accuracy of physical examination is, however, joint aspiration in a variety of clinical settings. Developmental dys- not absolute with <1% reported misdiagnoses [3]. Owing to intrinsic plasia of the hip, irritable hip and apophyseal traction injuries are limitations of radiography related to the use of ionizing radiations and the unossified status of the relevant bony landmarks, US has been proposed as an efficient alternative to diagnose developmen- ∗ Corresponding author. Tel.: +39 3355614449; fax: +39 010 555 6620. tal dysplasia of the hip. Basically, two methods have been developed E-mail address: [email protected] (C. Martinoli). to image the neonatal hip with US: static (Graf, Morin, modified 0720-048X/$ – see front matter © 2011 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ejrad.2011.03.102 Please cite this article in press as: Martinoli C, et al. Hip ultrasound. Eur J Radiol (2011), doi:10.1016/j.ejrad.2011.03.102 G Model EURR-5474; No. of Pages 8 ARTICLE IN PRESS 2 C. Martinoli et al. / European Journal of Radiology xxx (2011) xxx–xxx Fig. 2. Irritable hip. (A) Transient synovitis. Long-axis US image over the ante- rior femoral neck in a 8 year-old child demonstrates a fluid-filled anterior recess (arrows) with convex anterior wall. The iliopsoas muscle (IP) is located superficial Fig. 1. Developmental dysplasia of the hip. (A) Standard coronal US image of the to this recess. (B) Septic arthritis. Long-axis US image over the anterior aspect of the normal infant hip shows the relevant anatomical structures for evaluation of hip hip joint in a 5 year-old child demonstrates overdistension of the anterior recess dysplasia. They are: the hypoechoic rounded femoral head (FH) centered over the (arrowheads) by pseudo-solid echogenic material. The joint capsule is thickened hypoechoic triradiate cartilage (3), the promontory (empty arrow), represented by (arrowheads). Note the femoral head consisting of the ossification center of the the junction between the iliac wing (a) and the bony acetabular roof (b), and the epiphysis (1), the physis (2) and the metaphysis (3) covered by cartilage (4). The fibrocartilaginous labrum (c) in continuity with the acetabular hyaline cartilage (1). iliopsoas muscle (5) lies superficial to the joint. More superficially, the gluteus medius (Gme) is seen. During US examination, the iliac bone must be always kept parallel to the probe, otherwise inaccurate measure- ments will be made. (B) Frank hip dislocation. Standard coronal US image reveals discloses many immature or unstable hips that will resolve spon- a dislocated femoral head (FH) that does not fit within the cup of the acetabulum. taneously [19,21]. Overall, the question of whether US screening Note the deeper position of the promontory (empty arrow) relative to the femoral head. for developmental dysplasia of the hip is effective and justified is sure to remain a subject of much debate and further research. Morin (Terjesen)) and dynamic (Harcke), as well as a combination of the two (modified Graf (Rosenthal)) [4–7]. These methods have 1.2. Irritable hip proved to be effective and highly accurate in establishing the diag- nosis, even if the dynamic technique seems requiring more training The irritable (painful) hip represents a common clinical occur- and practice [8–10] (Fig. 1). In the last decades, US has been selected rence in children [22]. This condition may be related to a variety as the screening procedure for developmental dysplasia of the hip of disorders, including transient synovitis, septic synovitis, Perthes in many countries [5,6,11–15]. Both universal and selective (limited disease and slipped capital femoral epiphysis. This clinical entity to infants with known risk factors) screening programs have been typically presents with acute pain about the hip and the groin, limp- established. In this field, US has proved to be able to detect one third ing and non-weightbearing, limitation of movement and fever. In more abnormalities than the clinical examination [16,17]. Univer- combination with clinical and laboratory parameters, US can play sal screening using the Graf’s method showed that approximately an important role for the diagnostic work-up. Transient synovitis is 75–85% of infants have normal hips, 13–25% have immature hip a benign, self-limiting disorder of unknown origin which represents and 2–4% have dysplastic hips [18,19]. Concerning the association the most prevalent cause for hip pain in children aged 3–8 years. between morphology and stability, 0.1% of normal hips, versus 0.6% Preceding infection of the upper respiratory tract, increased viral of the immature type, 64% of slightly dysplastic and almost 100% antibody titres and some allergic predisposition are linked to this of severely dysplastic undergo dislocation [19]. On the other hand, condition. In these cases, US reveals hip joint effusion distending selective screening limited to infants with risk factors or unstable the anterior recess of the hip joint [23–25]. The fluid distending hip at physical examination was unable to eradicate the onset of the joint is anechoic and not associated with synovial thicken- late cases (accounting for approximately 0.025–0.035%) that occur ing [26] (Fig. 2A). The effusion is considered pathologic when its in a population with normal physical examination around birth and amount is >2 mm in thickness [27]. Patients with transient synovi- no documented risk factors [17,20]. As regard the optimal timing tis have increased risk of developing Perthes disease [28]. Because for screening, it is accepted that scanning too early (4–6 weeks) the ascending cervical arteries pass underneath the anterior joint Please cite this article in press as: Martinoli C, et al. Hip ultrasound. Eur J Radiol (2011), doi:10.1016/j.ejrad.2011.03.102 G Model EURR-5474; No. of Pages 8 ARTICLE IN PRESS C. Martinoli et al. / European Journal of Radiology xxx (2011) xxx–xxx 3 recess, some pressure exerted on these vessels by the effusion in transient synovitis might be possibly predisposing the femoral head to ischemia.