4 Ultrasound
Stefano Bianchi and Carlo Martinoli
S. Bianchi, MD
Institut de Radiologie, Clinique des Grangettes, 7 Chemin des Grangettes, 1224 Chêne-Bougeries, Switzerland
C. Martinoli, MD
Professor of Radiology, Istituto di Radiologia, Università di Genova, Largo Rosanna Benzi 1, 16100 Genova, Italy
4.2
Technique of Examination and Normal US Appearance
Prior to a US examination, two steps are funda- mental. Firstly, a basic history must be obtained and a physical examination carried out since these are important to accurately target the US examina- tion. This usually takes no more then a couple of minutes and can be performed with the patient on the examining bed. Location, type and intensity of pain, as well as worsening during the night or when performing daily activities must be investigated, followed by an assessment of range of movements and palpation of the periarticular region to iden- tify joint stiffness and pinpoint tenderness. Specific maneuvers are only performed if a definite diagno- sis is suspected. For example, if a tendinopathy of the gluteus medius is assumed, resisted abduction of the lower extremity with the knee extended can corroborate the suspicion by showing local peritro- chanteric pain. Secondly, a careful review of the previous imaging examinations must be performed.
The opportunity to review a recent, well performed pelvis radiograph and oblique view of the affected hip is a prerequisite for a correct US examination.
Standard radiographs can show bones, coxofemo- ral, sacroiliac and symphysis pubis joints, as well as calcific deposits located within the periarticular areas. CT scan and MR imaging are rarely available before US.
The patient is examined lying supine on the examining bed. Adequate exposure of the hip region is essential. A description of the US exami- nation technique is simpler, particularly for the novice sonographer, if the region is divided into several areas. We usually start a routine examina- tion with the anterior region, with the patient lying supine. Then the lateral region is studied while the patient turns on the opposite side. Finally the posterior structures are investigated in the prone position.
4.1
Introduction
In the past ultrasound examinations of the hip were largely performed in infant hips to rule out devel- opmental hip dysplasia. Improvement of new trans- ducers and the widespread awareness of the useful- ness of US for assessing musculoskeletal disorders have resulted in a growing number of hip exami- nations. Due to its recognized increased capacity to image this region, US is increasing used mainly to detect intraarticular joint fluid, and to evaluate of para-articular masses and tendon disorders. As in other areas of the body, accurate knowledge of the normal and abnormal US anatomy is a definite prerequisite for a successful US assessment. This chapter describes the examination technique and normal US appearance of the hip region. Since the US examination technique for the adult hip differs significantly from that of the pediatric hip, this will be described in chapter 8.
CONTENTS
4.1 Introduction 49
4.2 Technique of Examination and Normal US Appearance 49
4.2.1 Anterior Aspect 50 4.2.2 Lateral Aspect 53 4.2.3 Posterior Aspect 56 References 58
cranial to caudal.
Transverse images of the anterosuperior iliac spine (ASIS) region show the spine as a regular hyper- echoic line with posterior shadowing (Fig. 4.1). Since the spine is located very superficial and close to the skin, an adequate amount of gel must be deployed in thin patients for its proper assessment. The thin sar- torius muscle (SA) can be detected medially, while the larger tensor fascia lata muscle (TFL) is found laterally. Both have short triangular-shaped tendons that are best evaluated by tilting the transducer in the sagittal plane. Longitudinal sonograms over the tendons show them as hyperechoic structures inserting into the hyperechoic outline of the ASIS (Fig. 4.2). The mean thickness of the TFL tendon was 2.1 mm in a group of 40 healthy asymptomatic sub- jects with no difference between the right and left side (Bass and Connel 1992). Both tendons must be accurately examined since they can be affected by
riorly to insert into the anterior border of the fascia lata (FL). Compared to the adjacent muscles, its distal portion contains a larger amount of fat depos- ited among muscle fascicles which is responsible for its more echogenic appearance (Bass and Connel 1992). The distal insertion can be easily evaluated by longitudinal scans and presents a pointed appear- ance due to gradual distal tapering of the muscle.
This appearance resembles that of the distal inser- tion of the rectus femoris and gastrocnemius medial head. A globular appearance, even if localized, must be interpreted as a distal myotendinous avulsion.
The transducer is then moved to a more medial location where transverse sonograms reveal the intrapelvic portion of the iliopsoas (IP) muscle lying over the anterior face of the iliac wing (Fig. 4.3).
In thin subjects US can detect the intramuscular tendon as a hyperechoic structure surrounded by the muscle fibers. This region must always be ana-
Fig. 4.1a–e. Anterior aspect. a Probe positioning for transverse examination. b–e Corresponding sonograms obtained from cranial to caudal. TFL, tensor fascia lata muscle; Sa, sartorius muscle; RF, rectus femoris muscle; arrow, tendon of the rectus femoris muscle; AIIS, anterior inferior iliac spine; FH, femoral head; Fem, femur
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lyzed in case of IP bursa fluid enlargement since in these cases the bursa can continue inside the pelvis and present as a pelvic mass (Bianchi et al. 2002a).
The internal echostructure of the IP muscle must be carefully examined, particularly in patients with total hip replacement. Any anomaly of the IP muscle due to partial tears and associated hematoma can be
seen in symptomatic patients if the posterior face of the muscle impinges against a protruding acetabu- lar cup (Rezig et al. 2004).
After completing examination of the cranial part of the anterior aspect, the transducer is then moved distally to image the anteroinferior iliac spine (AIIS). The spine can be easily detected as a
Fig. 4.2a–e. Anterior aspect. a Probe positioning for transverse examination. b–e Corresponding sonograms. b,c Sagittal sono- grams obtained over the tensor fascia lata muscle (TFL). GMi, gluteus minimus muscle; VL, vastus lateralis muscle; ASIS, anterior superior iliac spine. d,e Sagittal and transverse sonograms obtained over the rectus femoris tendon. IT, indirect tendon; arrow- heads, posterior shadowing of the indirect tendon; arrows, direct tendon; FH, femoral head; AIIS, anterior inferior iliac spine
Fig. 4.3a,b. Anterior aspect. a Probe positioning for transverse examination. b Corre- sponding sonogram. I, iliac muscle; PS, psoas muscle; FA, femoral artery; FN, femoral nerve; arrow, iliopsoas tendon
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ing from the superior aspect of the acetabulum and joining the lateral aspect of the direct tendon and the reflex tendon that is directed upward and medi- ally to merge with the hip anterior capsule. While the reflex tendon is not detectable on US, the main direct tendon is easily assessed by transverse and sagittal sonograms obtained just distal of the AIIS (Figs. 4.1, 4.2). It appears as a thick, hyperechoic, oval structure. The sonographer must be aware that the normal tendon can display a posterior shadow- ing, particularly in transverse images, and this must not be interpreted as an intratendinous calcifica- tion. The reason for this phenomenon is unknown although we believe that it can be related to changes in fiber direction due to joining of the indirect and direct tendon. It must be noted that, although in adults scanning must be chiefly directed to the tendons inserting into the iliac spines, in children attention must be paid to the bone during examina-
the transducer is rotated inferiorly until the typical bone outline of the femoral neck is evident. Images obtained in this plane are well suited to image the anterior synovial recess and detect intraarticular effusion. The anterior hip synovial recess has been well described by Robben et al. (1999) who corre- lated US appearance with anatomic and histologi- cal appearance in cadavers. The anterior recess lies between the deep fascia of the IP muscle and the femoral neck and is composed by an anterior and a posterior layer. The two layers correspond to the cul-de-sac of the capsule which, after leaving the anterior border of the acetabulum, runs inferolater- ally to reach the intertrochanteric line. At this level the most superficial fibers continue with the peri- osteum while the deepest reflect and travel upward to insert into the junction between the head and the neck at the caudal edge of the articular carti- lage. Each layer is made up of a thick fibrous and a
Fig. 4.4a–d. Anterior aspect. a Probe positioning for examination of the psoas muscle and tendon (b,c) and of the anterior joint recess of the hip joint (d). b,c Corresponding sonograms. PM, psoas muscle; arrow, psoas tendon; white arrowhead, anterior joint capsule; void arrowhead, cartilage of the femoral head; FH, femoral head; Ac, acetabulum. d FH, femoral head; FN, femoral nerve; FA, femoral artery; arrowheads, anterior joint recess
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thin synovial component. The fibrous component, composed histologically of collagen fibers, appears on US as a 2 to 4 mm hyperechoic band while the normal one- to three-cell thick synovial lining is too thin to be detected. The anterior fibrous layer is thicker then the posterior layer, probably because the anterior capsule is reinforced by the iliofemo- ral ligament. The two layers are separated, in the absence of intraarticular effusion, by a hyperechoic line that represents an interface between the layers corresponding to the collapsed recess. This sign has been referred by to by Robben et al. (1999) as the stripe sign. In adults the diagnosis of adult hip effu- sion is made when the anterior synovial recess is distended by greater then 7 mm (Koski et al. 1989).
Nevertheless it must be noted that differentiation of the two layers with US is easier in infant hips and can be more difficult, if at all possible, in adults (Wey- bright et al. 2003). Obese patients are particularly difficult to examine because of the deeper position of the joint and use of lower frequency transducers can be of only partial aid. Attention must be made not to confuse the anterior and posterior capsule layers with an effusion since the capsule can appear hypoechoic when imaged not perpendicularly to the US bean. The fibrocartilaginous acetabular labrum can be detected as a hyperechoic homogeneous tri- angle that present the same aspect of the glenoid labrum or knee menisci. Its assessment requires accurate positioning of level of focalization and seldom utilization of 5 MHz transducers.
Transverse sonograms can accurately disclose the structures superficial to the articular plane. The muscles are best imaged by transverse and longitu- dinal scans. The muscles detected at this level from lateral to the medial are: the TFL, RF, SA, IP and the pectineus (PE) muscles.
Overlying the joint space the IP muscle is found lying in a lateral position while the femoral nerve, artery and vein are found in a more medial position (Fig. 4.4). The IP muscle lies just superficial to the capsule plane. Its posterior fascia is closely related with the anterior hip capsule and the two structures are barely discernible at US. The hyperechoic tendon is located inside the posterior part of the muscle and can be detected at both at transverse and sagittal plane running anteriorly to the acetabular labrum. A synovial bursa, the IP bursa, is located between the tendon and the anterior capsule. The main function of the bursa is reduction of IP tendon friction over the hip joint during muscle activation and joint move- ments (Ginesty et al. 1998). With respect of the ana- tomic situation the IP bursa is similar to the gastroc-
nemius-semimembranous synovial bursa. Both are located close to the joint capsule and separate it from a paraarticular tendon. In both cases a communica- tion with the joint space can be found particularly in adult. Communication with the hip joint is found in 15% of subjects and can be congenital or acquired. In pathologic cases in which large joint effusions rise the intraarticular pressure the two bursae can be filled by fluid and lessen tension on the adjacent joint. Like the majority of other bursae, the IPB is normally collapsed and can not be detected by US. On the other hand, US has proved to be an efficient and easy modality to detect and evaluate intrabursal effusion and syno- vial hypertrophy (Bianchi et al. 2002a). Once the IP muscle and tendon are examined, the transducer is displaced medially to image the femoral neurovas- cular pedicle (Fig. 4.5). The femoral nerve, artery, and vein are then imaged from lateral to medial. The femoral nerve presents the typical internal fascicular pattern that can only be well imaged proximally since it divides into the terminal branches just after leav- ing the pelvic cavity. The normal femoral vein is of larger diameter than the artery and collapses under the pressure of the transducer. This maneuver must be part of all hip US examinations. Calcific plaques inside the artery wall are frequently noted in elderly patients. Detailed evaluation of internal flow neces- sitates use of the color Doppler technique.
A more distal assessment of the cranial aspect of the RF muscle clearly depicts its peculiar inter- nal architecture made by a central tendon continu- ing the indirect tendon and a superficial tendon lamina arising from the direct tendon (Bianchi et al. 2002b). This US appearance correlates well with cadaver studies and MR imaging data (Bianchi et al. 2002; Hasselman et al. 1995) and can explain the occurrence of intrasubstance incomplete tear (Hughes et al. 1995).
4.2.2
Lateral Aspect
The superficial gluteus medius muscle (GMe) and the deep gluteus minor (GMi) are found in the lat- eral hip region (Figs. 4.6–4.8). The GMi originates from the anterior portion of the lateral aspect of the iliac wing to extend inferiorly. The GMe has a wider surface of insertion originating from the posterior two thirds of the iliac wing and covers most of the GMi. Both muscles act as abductors and in addi- tion flexors (posterior part of the GMe) and exten- sors (GMi) of the lower extremity. They insert in the
Fig. 4.5a–d. Anterior aspect. a Probe positioning for examination of the anterior vessels and nerves. b Transverse sonogram. c–e Sagittal sonograms. b–e Corresponding sonograms. PE, pectineus muscle; FN, femoral nerve; FA, femoral artery; FV, femoral vein; arrowheads, parietal valves
Fig. 4.6a–d. Lateral aspect. a Probe positioning for transverse examination. b–d Corresponding sonograms obtained from cra- nial to caudal. GMe, gluteus medius; GMi, gluteus minimus; 1, GMi tendon; 2, GMe anterior tendon; 3, GMe posterior tendon;
GT, greater trochanter
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greater trochanter (GT), a large apophysis located at the superolateral aspect of the femoral proximal metaphysis that presents an anterior, a lateral, and a superoposterior facet. The GMi muscle continues in a strong tendon that is directed downward to insert into the anterior facet. The posterior portion of the GMe muscle continues into a strong tendon that inserts into the superolateral facet. The anterior and middle part continues into a thin tendinous lamina that inserts, together with muscle fibers, into the inferior aspect of the lateral facet (Pffirmann
et al. 2001). The fascia lata (FL) is a thick fibrous band located superficial to the GMe cranially and to the lateral aspect of the trochanter distally. The anterior portion of the GMa and the TFL insert into the FL. Several synovial bursae found in the region allow smooth gliding among the tendons and fascia lata and the GT. The most common bursa is the trochanteric, followed by the GMe and the GMi bursae. The first is located between the under-sur- face of the GMa and the posterior facet of the GT and the lateral aspect of the GMe tendon. The GMe
Fig. 4.7a,b. Lateral aspect. a Probe positioning for coronal examination. b Correspond- ing sonogram. GMe, gluteus medius; GMi, gluteus minimus; 1, GMi tendon; FL, fascia lata; GT, greater trochanter
Fig. 4.8a–c. Lateral aspect. a Probe posi- tioning for coronal examination. b,c Cor- responding sonograms. GMa, gluteus maximus; GMe, gluteus medius; 2, GMe anterior tendon; 3, GMe posterior tendon;
GT, greater trochanter b
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obtained cranial to the greater trochanter show the GMe and GMi muscles whose anterior margins blend together. To localize the anterior portion of the GMi the sonographer must first visualize the TFS, then, by moving the transducer posteriorly, the anterior margins of both muscles can be recog- nized. Similarly, posterior images over the anterior portion of the large GMa are first obtained to help identification of the posterior part of the GMe. In a more superficial location the thick hyperechoic FL is detected as a hyperechoic band that joins the anterior portion of the GMa and the posterior part of the TFS and lies on the lateral aspect of the GMe.
Deep to the muscle plane the hyperechoic line cor- responding to the lateral aspect of the iliac bones is found. Once the muscle bellies have been evaluated the transducer is moved inferiorly at the level of the GT. Due to the different orientation of the GMe and GMi muscles an optimal assessment of their tendons can be obtained only by evaluating each tendon sep- arately. The GMi tendon can be seen at the anterior level as a hyperechoic structure that arises from the deep part of the muscle and inserts into the ante- rior GT facet. Images obtained over the lateral facet shows the lateral tendon of the GMe tendon as a curvilinear band. Moving the transducer more pos- teriorly allows visualization of anterior part of the GMa muscle covering the oval posterior component of the GMe tendon. Images are then obtained at the supratrochanteric and trochanteric region by tilt- ing the transducer in the coronal plane. The more superficial distal tendons are more easily evaluated.
Moving the probe from anterior to posterior enables assessment of the GMi, as well as the lateral por- tion and posterior part of the GMe. The tendons can be properly evaluated by tilting the probe parallel to their long axis in order to avoid anisotropy. The bone attachment into the different GT facets can be detected. Because of the small amount of synovial fluid, the peritrochanteric bursae are not visualized by US in normal conditions.
Coronal images are the best suited to demonstrate the FL that appears as a uniform hyperechoic band with smooth borders overlying the GMe muscle cra- nially, and the lateral GMe tendon distally.
the transverse and sagittal oblique plane. The entire muscle can be imaged from its medial origin to its lateral insertion into the femur and FL.
The deeper structures are more difficult to evalu- ate (Cohen 2002) (Figs. 4.9–4.11). First the medial
Fig. 4.9a,b. Posterior aspect. a Probe positioning for trans- verse examination. b corresponding sonogram. GMa, gluteus maximus; IFT, ischiofemoral tendons; SN, sciatic nerve; Isch, ischiatic tuberosity; Fem, femur
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structures are examined. For this purpose the most useful landmark is the hyperechoic ischial tuberos- ity. Once detected the cranial part of the ischiocrural tendons can be demonstrated inserting on its lateral aspect. Usually the different tendons, the semimem- branosus (SM) and the semitendinosus-biceps (ST- B) tendon cannot be distinguished. In a more lateral location, surrounded by fat, the sciatic nerve can be seen lying between the deep quadratus femoris and the superficial GMa muscle. The nerve has an oval to flattened appearance and presents the typical internal fascicular echotexture. More caudally the conjoined tendon of the ST-B can be seen in a more
superficial and lateral position with respect to the SM tendon. The two hyperechoic tendons, together with the lateral sciatic nerve, form a hyperechoic tri- angle known as the “Cohen triangle” from the author that first described it (Cohen 2002). Detection of the triangle is very helpful since it allows a correct indi- vidualization of the main anatomic structure of the area. More caudally the ST-B appears as a comma shaped structure located between the medial ST muscle, the fibers of which originate more cranial than those of the B muscle, and the lateral SM mus- cles. The SM tendon continues in a large aponeuro- sis that directs medially and posteriorly. No fibers of
Fig. 4.10a,b. Posterior aspect. a Probe positioning for transverse examination. b Corresponding sonogram. GMa, gluteus maxi- mus; STM, semitendineus muscle; CT, common tendon of the biceps tendon and semitendinosus tendon; SMT, semimembra- nosus tendon; SN, sciatic nerve; Isch, ischiatic tuberosity
Fig. 4.11a,b. Posterior aspect. a Probe positioning for trans- verse examination. b Corresponding sonogram. STM, = semi- tendinous muscle; BM, biceps muscle; SMT, semimembranous tendon and tendon lamina (arrowhead); SN, sciatic nerve
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tendon. These tendons insert into the lateral aspect of the ischial tuberosity rather then into the inferior face. Transverse caudal images show that the first muscle that appears is the ST followed by the lateral B and in a more distal location by the medial SM.
The sciatic nerve is always located laterally to the tendons. Cranially it forms the anterolateral corner of the Cohen triangle, in a more distal location it can be detected just below the biceps muscle. The poste- rior aspect of the hip joint and deep muscles are very difficult to assess and differentiate.
References
Bass CJ, Connel DA (2002) Sonographic findings of tensor fascia lata tendinopathy: another cause of anterior groin pain. Skeletal Radiol 31:143–148
Bianchi S, Martinoli C, Keller A et al (2002a) Giant iliopsoas
Hasselman CT, Best TM, Hughes C 4th, Martinez S, Garrett WE Jr (1995) An explanation for various rectus femoris strain injuries using previously undescribed muscle architec- ture. Am J Sports Med 23:493–499
Hughes C 4th, Hasselman CT, Best TM, Martinez S, Garrett WE Jr (1995) Incomplete, intrasubstance strain injuries of the rectus femoris muscle. Am J Sports Med 23:500–506 Koski JM, Anttila PJ, Isomaki HA (1989) Ultrasonography of
the adult hip joint. Scand J Rheumatol 18:113-117 Pffirmann CWA, Chung CB, Theumann NH et al (2001) Greater
trochanter of the hip: attachment of the abductor mecha- nism and a complex of three bursae-MR imaging and MR bursography in cadavers and MR imaging in asymptom- atic volunteers. Radiology 221:469–477
Rezig R, Copercini M, Montet X et al (2004) Ultrasound diagnosis of anterior iliopsoas impingement in total hip replacement. Skeletal Radiol 33:112–116
Robben SGF, Lequin MH, Diepstraten AFM et al (1999) Ante- rior joint capsule of the normal hip in children with tran- sient synovitis: US study with anatomic and histology correlation. Radiology 210:499–507
Weybright PN, Jacobson JA, Murry KH et al (2003) Limited effectiveness of sonography in revealing hip joint effu- sion: preliminary results in 21 adult patients with native and postoperative hips. AJR 181:215–218
