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US hip dysplasia

  1. 1. REAL-TIME ULTRASOUND IN THE DIAGNOSIS OF CONGENITAL DISLOCATION AND DYSPLASIA OF THE HIP N. M. P. CLARKE. H. THEODORE HARCKE, PETER McHUGH, MYUNG 500 LEE, PATRICIA F. BORNS, G. DEAN MAcEWEN From the Alfred I. duPont Institute, Wilmington, Delaware A technique of examining the infant hip joint with real-time ulfrasound is described. Since the cartilaginous femoral head is clearly imaged by ultrasound, anatomical structures and their relationships can be accurately determined. Dislocated hips are easily detected and subluxations also can be visualised. We report our experience with 131 examinations in 104 patients, comprising 259 single hip studies. Of 83 patients who were previously untreated, there were 178 hip studies with three false-negative and four false- positive ulfrasound results. No dislocations were missed. Twenty-seven patients who were already being treated were examined to assess hip location, comprising a total of 81 hip studies. In some cases the patients were examined while in an abduction device, cast, or Pavlik harness. In one case a disloction was not detected. The method of examination using real-time ultrasound is considered to be reliable, accurate, and a useful adjunct to radiography. The advantages are that it is non-invasive, portable, and involves no exposure to radiation.The diagnosis of instability and dysplasia in the hip of definitely abnormal. At present, clinical and radio-the newborn infant remains difficult. Although clinical graphic examinations are used to complement eachexamination is recognised as an effective screening other. A single examination by itself may be unsatis-method for dislocations, there remains a small popula- factory, and invasive arthrography may, in sometion of neonates in whom a confirmatory image is patients, be the only means of obtaining a clear imagedesirable. Radiographs are, of course, helpful in the of the developing hip joint.assessment of unstable hips (Bertol, Macnicol and Since Kleinberg and Lieberman (1936) introducedMitchell 1982) or frankly dislocated hips. However, the the acetabular index as a possible means of identifyingexact indications for and limitations of radiographic abnormal hips, confusion and controversy have existedexamination of the neonatal hip are still unclear. Un- and many attempts to clarify the exact radiographiccertainties arise in the interpretation of radiographs of indices for dysplasia have been made (Caffey et a!. 1956;the immature pelvis, regardless of the intended position Laurenson 1959). In some methods of evaluation,of the hip; indeed, position may be an important cause of complicated calculations are required (Tonnis I 976;simulated abnormality (Blank 1981). Wientroub 1981). Misinterpretation arises because the only structures In the context of this diagnostic dilemma, ultra-imaged by radiographs are the ossified portions of the sound has obvious potential for examining the infantpelvis. It therefore becomes necessary to extrapolate the hip. It requires no exposure to radiation and clearlyimage of the cartilaginous structures. Clearly this has images the cartilaginous structures that are so poorlydisadvantages, and a radiograph only contributes signifi- delineated by radiography.cantly to the diagnosis and management ofthe hip ifit is Graf(1983) was the first to realise this potential. He used a fixed-arm B-scanning unit to obtain sonographic images ofinfant hipjoints. His technique was necessarily complicated because of the equipment he used, and itN. M. P. Clarke, FRCS. Senior Registrar took considerable expertise and time to obtain a satis-Royal Orthopaedic Hospital, Woodlands, Northfield, Birmingham factory examination. Real-time ultrasound is muchB3l 2AP, England.H. T. Harcke. MD, Director, Department of Medical Imaging simpler to operate and is portable, and the ultrasoundP. McHugh, Research Student image changes rapidly enough to portray movement.M. S. Lee, MD, Radiologist. Department of Medical Imagingp. F. Borns, MD, Radiologist, Department of Medical Imaging Images are obtained by placing a transducer on the skinG. D. MacEwen, MD, Medical Director and scanning a specific sector of the anatomy. The sectorAlfred I. duPont Institute, P0 Box 269, Wilmington, Delaware19899, USA. is varied by moving the transducer, allowing simulta-Requests for reprints should be sent to Mr N. M. P. Clarke. neous images to be viewed on a screen. Novick, Ghelman,i_) 1985 British Editorial Society of Bone and Joint Surgery and Schneider (1983) examined a small number of infant0301-620X/85/3051 $2.00 hips using real-time ultrasound and were encouraged by406 THE JOURNAL OF BONE AND JOINT SURGERY
  2. 2. REAL-TIME ULTRASOUND IN DIAGNOSING CONGENITAL HIP DISLOCATION AND DYSPLASIA 407the views that they obtained. This led us to undertake a cies were tried, but most examinations were performedprospective study of a group of infants referred for hip with the 3 MHz scan head. The technique that wasevaluation. developed has been reported elsewhere (Harcke et a!. The aims of this study were: to establish that real- 1984) but it is appropriate to describe it briefly here.time ultrasound was a reliable method of identifying Studies were first performed on the hip joint of ananatomical structures and their relationships; to develop anaesthetised infant pig. Simultaneous fluoroscopic anda technique for routine examination; and to ascertain sonographic examinations allowed correlation of ana-whether ultrasound could differentiate between normal tomical landmarks. This was facilitated by the insertionand abnormal hips. of a needle into key points within the joint, such as the ossific nucleus. We established that the femoral head MATERIALS AND METHODS appears as an area of few echoes while the bony ilium is aA total of 122 patients referred to the Alfred I. duPont bright echogenic structure except where the triradiateInstitute for evaluation of their hips have been studied. cartilage is present and produces few echoes. The gapAll were examined clinically by an orthopaedic surgeon created by the cartilage allows the transmission of soundfor instability or dislocation of the hip. A conventional into the pelvis in the zone where bone has producedanteroposterior radiograph was then obtained, followed acoustic real-time ultrasound examination of the hips. Theultrasound studies were performed without knowledge Table 1. Analysis of patients examined by ultrasoundof the preceding clinical and radiographic findings. Inthose instances where the infant was already being Total Number of Repeat numbertreated, or had returned for a follow-up visit, it was Reason for evaluation examinations examinations of hipsobvious that there was some clinical problem. However, Untreated (83 patients)at the time of ultrasound examination, the examiner was Hip click 10 2 24not aware of either the side or the type of involvement Subluxation 18 2 40 Dislocation* 9 0 18which had been diagnosed. Hip check 12 1 26 Table I details the patient population. At review, 19 Foot disorders 25 0 50 Torsional deformity 5 1 12examinations in I 8 patients were excluded: one patient Multiple 4 0 8(two examinations) had had multiple previous surgical abnormalitiesprocedures; in I 5 there were no radiographs available for Total 83 6 I 78comparison; in one patient there was a technical failure; Treated (27t patients)and in one osteogenesis imperfecta prohibited a satis- Pavlik harness 18 9 54factory examination. There remained I 31 examinations Nil 7 1 16 In cast l 2 5in 104 patients (259 individual hip studies) which form In brace I I 4the basis of this report. Twenty-seven patients were In traction 0 2 2already being treated, most of them in a Pavlik harness. Total 27 15 81Eighty-three patients were referred either for confirma- Exclusions (18 patients) 18 38tion of a diagnosis of hip dislocation or dysplasia, or forinitial assessment. The average age at examination was * Positive Barlow or Ortolani signs t 6 patients originally examined before treatment were examined again22 weeks (range 4 days to 2 years 6 months). There were after treatment started, 4 once and 2 patients three times37 boys and 67 girls. The ultrasound findings were Only 16 examinations in 10 patients were performed with the baby actually in the harnesscompared with the clinical examination and with the § Signifies only one hip examinedradiographic appearance (which was reported indepen-dently by a radiologist). A computer was employed toanalyse the information. With children, several views of the infant hip were Patients being actively treated were assessed only obtained by placing the transducer in different positions.for hip location. In untreated patients, the sonogram was A combination of two views was eventually selected asstudied for evidence of hip dislocation or subluxation being most reliable in the identification of the anatomicaland for acetabular dysplasia. This was compared with structures. This involved a series of two-plane examina-radiographic evidence of dislocation, subluxation, lateral tions which, when considered together, yielded a three-displacement and dysplasia. Clinical examination was dimensional representation of the hip. Displacement ofused to identify any limitation of abduction, and to the femoral head in any direction could therefore bedistinguish subluxatable, dislocatable and dislocated determined.hips. In both views, the images are obtained by placingUlfrasound technique. The sonographic examinations the transducer laterally in the region of the greaterwere performed using an Advanced Technology Labora- trochanter. In the view designated as “transverse-tory M K I 00 sector scanner and were recorded on neutral” the infant is supine and the hip is in the neutralvideotape. Both 3 MHz and 5 MHz transducer frequen- position. The image is effectively a transverse section ofVOL. 67-B, No. 3, MAY 1985
  3. 3. Figures 1 to 3 Figure I-The “transverse-neutral view.” The sector scanned by the ultrasound is a transverse section of the hip joint which is in the neutral position. Figures 2 and 3-The image obtained from the “transverse-neutral” view of a left hip with a corresponding diagram to identify the anatomical landmarks. Fig. I LAT. ANT. P01 Acetabulum Femoral Head Triradiate Cartilage Fig. 2 Fig. 3 Figures 4 to 6 Figure 4-The “coronal-flexion” view. The ultrasound sector effectively scans a coronal section of the hip joint. The femur is in the flexed position and the transducer is rotated through 90 when compared with the “transverse-neutral” view. Figures 5 and 6- The image obtained from the “coronal- flexion” view with a corresponding diagram to identify the anatomical landmarks. Fig. 4 LA T. Pelvis sup. INF. Fig. 6Figures I to 6 are reproduced with permission from Harcke et al. J U/trasound Med 1984;3: 13 1-7.
  4. 4. REAL-TIME ULTRASOUND IN DIAGNOSING CONGENITAL HIP DISLOCATION AND DYSPLASIA 409the hip joint, femoral head and neck (Fig. 1). Figure 2 view. In. a few cases infants who were being treated inshows the actual image obtained, with a corresponding casts were examined after cutting a lateral windowdiagram of the anatomical landmarks (Fig. 3). The through the plaster.femoral head lies against the bony acetabular floor withthe triradiate cartilage clearly seen as a defect in the RESULTSbright echoes. The concentric relationship of the femoral Of the 83 patients being evaluated for the first time, 89head to the triradiate cartilage in this view is crucial, examinations were performed comprising 178 individualsince failure to visualise it is indicative of displacement. hip studies. These studies were evaluated by comparisonThe femoral shaft serves as a reference point for the with both clinical and radiographic examinations (Tableexaminer. By moving the transducer in a cephalad II). There were I 36 true-negative and 22 true-positivedirection, the femoral head is revealed. Lateral displace- results.ment is seen as a gap between the femoral head and the Of the true positives there were eight subluxations,acetabular floor. Superior displacement will cause the 10 dislocations, and four hips with acetabular dysplasia.acetabulum to be obscured by echoes from the femoral For the purposes ultra- of this study, a false-negativeshaft and the triradiate cartilage will not be visualised. sound result was deemed to have occurred when ultra- In the second view, known as the “coronal-flexion” sound missed an abnormal hip detected by both clinicalview, the infant remains supine, the hip is flexed to 90#{176}examination and radiography. Similarly, a false-positive and the transducer is also rotated through 90#{176}. area The ultrasound result occurred when ultrasound was inter- scanned is effectively a coronal section of the flexed hip preted as showing an abnormal hip when clinical andjoint (Fig. 4). Figure 5 shows the actual image obtained radiographic examinations were both normal. There and Figure 6 is the corresponding diagram. The position were three false-negative and four false-positive results Table II. Hip evaluations in previously untreated patients True True False False Reason for evaluation negative* positivet negative positive ConflictsL Hipclick 19 2 1 1 1 Subluxation 26 6 1 1 6 Dislocation 7 8 0 1 2 Hipcheck 18 3 1 1 3 Foot disorder 48 2 0 . 0 0 Torsional deformity 12 0 0 0 0 Multiple abnormalities 6 1 0 0 1 Total 136 22 3 4 13 * Normal clinical, radiographic, and ultrasound examinations t Abnormal clinical, radiographic, and ultrasound examinations Abnormal clinical and radiographic examinations; normal ultrasound examination § Normal clinical and radiographic examinations; abnormal ultrasound examination U Inconsistent clinical and radiographic resultsof the bright echoes of the ilium superiorly reflect (Table III). No frank dislocations were missed. Ultra-acetabular depth and, therefore, coverage of the femoral sound missed a unilateral dysplastic hip in one patient; inhead. The greater the cover, the less the radiographic two other patients, each with bilateral subluxation,acetabular index, thus enabling an assessment to be ultrasound diagnosed only unilateral subluxation. Nomade ofacetabular dysplasia. Again, the femoral shaft is dislocations were falsely diagnosed. In three of the false-a reference point. It lies anteriorly because of the flexed positive results, clinical or radiographic examinations position ofthe hip. By moving the transducer posteriorly, had suggested unilateral abnormality, but ultrasound the femoral head and acetabulum will come into view. demonstrated bilateral involvement. Femoral head displacement will again cause the acet- Table II also details the 13 hip studies in which theabulum to be obscured by the echogenic femoral shaft. clinical and radiographic examinations did not agree; Most ultrasound examinations in this series were these are categorised as “conflicts” In seven hips, the . performed using a combination of the two views de- radiographic and ultrasound examinations were ab- scribed. Evaluation of infants in the Pavlik harness, normal but clinical examination was normal; in five the however, was based only upon the “coronal-flexion” radiographic results were abnormal but both clinical and VOL. 67-B. No. 3. MAY 1985
  5. 5. 410 N. M. P. CLARKE, H. T. HARCKE, P.McHUGH, M. S. LEE, P. F. BORNS, G. D. MACEWENTable III. False-negative and false-positive evaluations in untreated patients (178 hips examined) ClassificationPatient Reason fornumber evaluation Clinical examination Radiograph Ultrasound Left hip Right hipFalse negatives 5 Hip click Bilateral hip clicks Bilateral lateral Left-not concentrically True positive False negative Possible subluxation displacement reduced Right-normal 83 Hip check Left adduction Left dysplasia Normal bilaterally False negative True negative contracture 99 Subluxation Bilateral Bilateral lateral displace- Left-subluxated True positive False negative positive Barlow test ment with abnormal Right-normal acetabulaFalse positives I3 Dislocation Left positive Barlow test Normal Bilateral subluxation Conflict False positive 39 Subluxation Normal Right lateral displace- Bilateral dysplasia False positive Conflict ment 89 Hip check Normal Normal Left not concentrically False positive True negative reduced 1 18 Hip click Normal Left dysplasia Left-subluxated Conflict False positive Right-not concentrically reducedultrasound examinations were normal; and in one, clini- DISCUSSIONcal and ultrasound examinations were abnormal although We have established that real-time ultrasound can, inradiographs were normal. Excluding these “conflicts”, fact, be used to image the infant hip. Anatomicalthe specificity* for ultrasound in the untreated structures and their relationships are clearly visualised,group was 97% and the sensitivity* was 88%. and the capacity for imaging the cartilaginous femoral In the group of 27 patients already receiving head offers an important advantage over conventionaltreatment at the time of initial ultrasound examination, radiography. The technique for ultrasound examination42 examinations were made, comprising 81 individual that we have described is reliable for hips in infants up tohip studies. There were 75 true-negative studies (showing the age of about one year.that the hip was normally located), and four true- Our experience has shown that one limiting factorpositives. Three of these true-positives were hip disloca- for accurate interpretation of the image is the size of thetions (one in an abduction brace and two in the Pavlik ossific nucleus of the femoral head. When the bonyharness) and one was a severely dysplastic hip being nucleus is present, a zone of acoustic shadowing appearstreated in a Pavlik harness. There were no false-positives medially and may be mistaken for the triradiate car-in the treated group, but one false-negative result and tilage. The crucial sector in the transverse-neutral view isone “conflict” did occur. The “conflict” was in a patient one which demonstrates concentric reduction of thebeing followed for unilateral hip dysplasia in whom femoral head against the acetabular floor while at theultrasound was interpreted as normal but the radio- same time imaging for the triradiate cartilage. It is clearlygraphic appearances were equivocal. The only false- important that any artefactual triradiate cartilage is notnegative study was in a patient in an abduction brace mistaken for the actual triradiate cartilage. When thewith a dislocation that was missed by ultrasound. In this ossific nucleus is less than 10 mm in its transversepatient, initial radiographs had been reported as normal, diameter, the ultrasound beam can be directed at anbut suspicion led to confirmation of the diagnosis by angle that bypasses this nucleus and enables the triradi-computerised tomography. ate cartilage to be viewed. However, larger bony nuclei will obscure medial structures by virtue of the diminished cartilaginous space between the nucleus and the femoral metaphysis (Fig. 7). The combination of two views-the transverse- neutral and the coronal-flexion--was chosen because easily identifiable landmarks were consistently visible.* Specificity . . = True ___________________________ negatives These landmarks could not be misrepresented by a True negatives + false positives change in projection, hence normality was always quickly . . . True positives and reliably established. These two views allow dis- Sensitivity = . True positives + false negatives placement in any direction to be detected, and acetabular THE JOURNAL OF BONE AND JOINT SURGERY
  6. 6. REAL-TIME ULTRASOUND IN DIAGNOSING CONGENITAL HIP DISLOCATION AND DYSPLASIA 411dysplasia can be diagnosed by studying the coronal The ability of ultrasound to image the cartilaginoussection. The flexed posture of the hip in the coronal- femoral head-rather than the ossified femoralflexion view reflects the position used during the clinical metaphysis-in relation to the acetabulum makes it aexamination; this view also permits infants to be very attractive imaging tool. However, its sensitivityexamined while retained in a Pavlik harness or abduction must be viewed with caution. Barlow (1962) has statedbrace, when proper location of the hip is of prime that more than 60% of unstable hips recover sponta-interest. neously in the first week of life. We have seen several instances in which ultrasound images of neonatal hips have displayed slight subluxation of the femoral head (Fig. 8) which shows as a gap between the head and the acetabular floor. We have performed an insufficient number of hip studies in such patients to establish whether this appearance resolves spontaneously at the same time as the clinical laxity, or whether it is a true pathological entity. Clearly, before ultrasound can be used with certainty as a screening tool for congenital hip dislocation or dyspiasia, the natural history of this type of appearance will have to be defined. In our series, 27 infants were examined while retained in either a brace or a cast. Those in casts were examined through a lateral window, using the landmarks of the coronal-flexion view to assess hip location. Hips retained in a brace were subject to the difficulties of examination caused by abduction. The one missed Fig. 7 dislocation was such a case: the femoral head was veryTransverse-neutral view of a right hip illustrating how a large ossificnucleus may obscure medial structures by virtue ofacoustic shadowing small, the acetabulum very shallow, and the posterior (arrow). dislocation was only clearly seen with the aid of com- puterised tomography. We have found that an adduction contracture of thehip makes the examination easier, in that the ultrasound“aperture” is effectively enlarged; an abduction contrac-ture closes the “aperture” and makes the examinationmore difficult. Several aspects of our results merit further dis-cussion. First, the standards by which we judged theaccuracy of ultrasound-clinical and radiographicexamination-are themselves open to question. Thesubtleties of the lax or clicking hip on physical examina-tion have long been recognised as complicating thedefinitive diagnosis of hip dislocation. Likewise, radio-graphic studies do not always reveal mild degrees ofdislocation, subluxation or, even more obscure, sub-luxatability. Hence the ultrasound “false-positive” re- Fig. 8suits may conceivably reflect true pathology, particularly Transverse-neutral view ofa right hip in a neonate. The femoral head iswhen consideration is given to the fact that three patients not concentrically seated, as evidenced by a gap between the head andwith false-positive ultrasound studies each had a con- acetabular floor medially (arrow). There is also slight posterior displacement of the femoral head.tralateral hip in which the clinical and radiographicresults were in conflict (Table III). Those examinations classified as “conflicts”, inwhich the clinical and radiographic assessments differed, No mention has yet been made of the potential forare a testimony to the difficulties that may be encoun- dynamic examination offered by real-time ultra-tered in diagnosing hip dislocation and dysplasia. We sonography. One dislocatable hip was examined in suchhave not included these results in our final calculations a way that the hip could be viewed in both the locatedbecause we cannot, except in extreme cases, objectively and the dislocated positions. While this case effectivelydetermine whether the clinical or radiographic results are demonstrated the possibility of dynamic study, the realactually correct. value of such an examination lies in its ability to imageVOL. 67 B. No. 3. MAY 1985
  7. 7. 412 N. M. P. CLARKE, H. T. HARCKE, P.McHUGH, M. S. LEE, P. F. BORNS, G. D. MAcEWENhips with less distinct abnormalities. Ultrasound offers may be a non-invasive alternative to the measurement ofgreat advantages over conventional radiographs in the angles or distances on a radiograph, since the relation-detection of hip abnormalities, certainly as an adjunct to ships of the cartilaginous femoral head are defined inradiographic evaluation (both diagnostic and follow-up three dimensions. As such, sonographic imaging maystudies), and possibly even as a screening tool. Ultra- contribute significantly to the understanding of thesound could also eventually replace some of the multiple natural history and pathological anatomy of the spec-radiographs required to assess relocation during treat- trum ofjoint abnormality encompassing congenital hipment, thus reducing exposure to radiation. Ultrasound dislocation and dysplasia. REFERENCESBarlow TG. Early diagnosis and treatment of congenital dislocation of Harcke HT, Clarke NMP, Lee MS, Bores PF, NiacEwen GD. the hip. J Bone Joint Surg [BrJ l962;44-B:292.-301. Examination of the infant hip with real-time ultrasound. JBertol P, Macnicol MF, Mitchell GP. Radiographic features of Ultrasound Med 1984:3: 13 1-7. neonatal congenital dislocation of the hip. J Bone Joint Surg [Brl Kleinberg S, Lieberman HS. The acetabular index in infants in relation 1982;64-B: 176-9. to congenital dislocation of the hip. Arch Surg l936;32: 1049-54.Blank E. Some effects of position on the roentgenographic diagnosis of Laurenson RD. The acetabular index: a critical review. J Bone Joint dislocation at the infant hip. Skeletal Radiol 198 1 ;7(l): 59-61. Surg [Br] 1959;4l-B:702-lO.Caffey J, Ames R, Silverman WA, Ryder Cl’, Houaji G. Contradiction Novick G, Ghelman B, Schneider M. Sonography of the neonatal and of the congenital dysplasia-predislocation hypothesis of con- infant hip. AJR l983;141(4):639-45. genital dislocation of the hip through a study of the normal T#{212}nniS Normal D. values ofthe hipjoint for the evaluation ofx-rays in variation in acetabular angles at successive periods in infancy. children and adults. C/in Orthop 1976; 1 19: 39-47. Pediatrics 1956; 17:632-40. Wientroub S, Tardiman R, Green 1, Salama R, Weissman SL TheGraf R. New possibilities for the diagnosis of congenital hip joint development of the normal infantile hip as expressed by radio- dislocation by ultrasonography. J Pediatr Orthop l983;3:354-9. logical measurements. mt Orthop 1981 ;4(4):239-41. THE JOURNAL OF BONE AND JOINT SURGERY