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Children's hip

  1. 1. Imaging, 14 (2002), 179–187 E 2002 The British Institute of RadiologyImaging of children’s hips1 D WILSON, MBBS, BSc, FRCP, FRCR and 2G ALLEN, BM DCH, MRCGP, MRCP, FRCR1Nuffield Orthopaedic Centre, Oxford and 2Royal Orthopaedic Hospital, Birmingham, UK Children may present with hip disease in avariety of ways. In the newborn it may be detected Summaryby routine clinical examination. In the older childpain, stiffness and limping are the primarysymptoms. In the toddler ‘‘going of their feet’’ N Ultrasound is an important tool in thedysplasia and management of developmental detectionmay be the presenting event. of the hip. Most children who complain of pain in the hiphave genuine pathology. It is an unusual location N Universal screening for developmentalfor a child to make up or exaggerate complaints. dysplasia of the hip by ultrasound may be wiseImaging has a pivotal role in the management of but there is currently insufficient evidence tothese patients who may have disease that requires clearly recommend this a national policy.urgent medical or surgical treatment. In most cases a child or infant complaining of a N A painful hip in childhood is a clinical emergency.painful hip should be examined and investigatedas a matter or urgency. Hospitals should provide N Ultrasound is the definitive method foron-call imaging and general practitioners should detecting joint fully aware of local facilities and managementprotocols. N Ultrasound cannot determine whether a joint effusion is due to infection, haemorrhage or transudate.Developmental dysplasia N Imaging has a role in determining the cause of Between 1 and 3 newborns per 1000 live births snapping hips.will be diagnosed as suffering from developmentaldysplasia of the hip (DDH), formerly known ascongenital dislocation of the hip, with a female vehement advocates. In reality, local outcomepreponderance of 9:1. This hides the much larger measures must be the standard by which theseincidence of premature osteoarthritis that devel- techniques are judged. The best method appliedops in young adults who have a shallow and badly or administered ineffectively will be of lessmechanically disadvantaged hip that is not bad use than a less technically demanding method thatenough to have presented in infancy. Many who is used rigorously with top quality clerical andundergo hip replacement in their middle years are management support.undiagnosed cases of DDH. The true incidence ofDDH is therefore much higher, although there areno clear figures in the literature (Figures 1 and 2). There is good evidence that early treatment ofDDH with splint therapy improves prognosis [1].This is only effective in the first 6 months oflife when remodelling is very active. Therefore ifdiagnosis is made early enough, overall popula-tion morbidity may be reduced. It was this rationalethat led to the now universal clinical screeningprotocols using Barlow and Ortolani manoeuvresto detect subtle subluxation and instability of thehip. Unfortunately clinical examination, even inthe best of hands, will overlook a substantialproportion of cases that would benefit from earlytreatment. Ultrasound introduces an additional Figure 1. Plain radiograph of a 28-year-old who hasmethod of screening that considerably improves early osteoarthritis secondary to developmental dys-detection [2–7]. A number of methods have been plasia that was asymptomatic as a child and youngdeveloped and each has strong and sometimes adult.Imaging, Volume 14 (2002) Number 3 179
  2. 2. D Wilson and G AllenFigure 2. Plain radiograph of a pseudarthrosis result-ing from unrecognized dislocation of the hip. Most techniques stem from that developed byProfessor Graf, an Austrian orthopaedic surgeon. Figure 4. Ultrasound of a shallow acetabulum thatGraf uses coronal plane ultrasound to produce a would be treated by a splint or harness.standard section equivalent in orientation to afrontal radiograph of the hip. Lines drawn on the More contentious is deciding upon the popula-image are used to measure the angular depth of tion to be screened. Infants with family history ofthe acetabulum and the cover of the femoral head. hip dysplasia, those born by breech delivery andStrict adherence to the technique is essential as those with other congenital anomalies are at muchsmall variations in measurement will alter classi- higher risk of developing DDH. Screening offication and affect management protocols. Others those at high risk in addition to those who arehave introduced less demanding methods of mea- suspected as being abnormal on routine clinicalsurement, although still requiring discipline in examination is the most common practice in theimage acquisition (Figures 3–5). It has been UK. Others argue that this policy will fail toargued that a static image alone is less sensitive provide the most accurate and sensitive detectionthan a morphological measure plus a dynamic of all who might benefit from early treatment andstress test, and there is evidence that this improves suggest universal screening [11]. In Austria anddetection [8]. In most practices a combination of Germany, child benefit entitlement is linked tostatic and dynamic imaging is employed [9, 10]. attending for screening. One counter to thisFigure 3. Ultrasound of a borderline depth acetabu- Figure 5. Ultrasound of a dislocated hip that requiredlum with measurement using the Morin method. surgical reduction.180 Imaging, Volume 14 (2002) Number 3
  3. 3. Imaging of children’s hipsargument is that required resources are not cost to immediate pain relief [25, 26]. There are noeffective, although this is a difficult line to take in organisms present on Gram stain and culture willwhat is an emotionally charged topic. Indeed be negative.there is evidence that the overall saving in Pain may be treated with analgesia, however,resources is conquerable in all screening strategies this is not very effective. Some advocate skin[12, 13]. More telling is the point that standards of traction and bed rest but this requires hospitaldetection are likely to drop in any universal admission. A diagnostic aspirate of the joint is ascreening project and that there is currently no more effective method of analgesia as there isevidence that overall population outcome is better instant pain relief and restoration of those centres where it is practiced. Further Local anaesthetic jelly and ultrasound guidanceepidemiological research is required before firm allow a safe and rapid joint puncture and preventrecommendations can be made, and current hospital admission in many cases.advice in the UK is to perform ultrasoundscreening in infants in the high risk category only. Septic arthritis In complex congenital hip disorders a combina-tion of ultrasound, plain radiography and MRI Pyogenic organisms may infect the hip via aare indicated, especially for planning surgery [14, blood borne route. Staphylococcus aureus and15]. For example, in deficiency of the proximal haemophylus influenzae are the most commonfemur either ultrasound or MRI may be used to organisms. If infection is untreated the joint willdetect whether there is a cartilage fragment in the be rapidly destroyed. Consequent septicaemiagap and to determine the integrity of the hip joint may be life threatening. The only effective therapy[16]. is a combination of arthotomy with joint lavage Following surgery or splint therapy, MRI is and intravenous antibiotics. Clinical presentationuseful to assess the degree and efficacy of reduc- is often indistinguishable from transient synovitis.tion [17]. In managing pelvic and femoral Fever and serological signs of inflammation areosteotomies the information from cross-sectional often absent. The degree of irritability does notimaging is important [18, 19]. predict diagnosis and ultrasound appearances of septic arthritis are no different from transient synovitis [27]. The only effective means of diag-Irritable hip nosis is aspiration, Gram stain and culture. Children between the ages of 3 years and 12 Fortunately the condition is rare and those whoyears commonly suffer from acute episodes of hip rely on ineffective methods of diagnosis will onlypain. The vast majority are suffering from rarely cause permanent damage.transient synovitis, which is a benign and self-limiting condition. Unfortunately, a small but Perthes diseaseimportant minority have a more serious com-plaint such as septic arthritis and need urgent Osteochondrosis of the hip, Legg–Calve– ´surgical management to minimize long-term Perthes disease, is an uncommon disease ofdisability [20]. The challenges are detecting and unknown cause. The most convincing theory istreating this small subset whilst treating the pain that it is the result of trauma in an immatureand discomfort of the majority in a timely and joint. Again, presentation is with pain andsafe manner. limitation of movement. The child may be older (7–14 years) and there is sometimes a history of previous episodes of pain. Plain radiography isTransient synovitis diagnostic showing fragmentation, roughening, The cause of transient synovitis is not known. flattening and distortion of the femoral capitalThere are postulates that it is traumatic or epiphysis (Figures 6–8). In the early phase theinfective in origin, but neither is proven. The plain radiograph shows widening of the hip jointcondition presents with a short history of pain owing to cartilage overgrowth. Long-term dis-and limping, which typically resolves within 3–4 ability may result owing to alteration in shape anddays. Although MRI, CT and ultrasound will all mechanical stress. Treatment is based arounddetect effusions [21], ultrasound is the established surgery designed to confine the femoral headmethod of choice as it is readily available, easy to within the joint, and often includes pelvic andperform and extremely accurate [22–24]. Ultrasound femoral osteotomies. Ultrasound examination inexamination shows a joint effusion with capsular the early stages of the condition will show jointdistension and a varied amount of synovial thicken- effusion [5, 28–30] and the fragmented epiphysising. A difference of 2 mm or more between the may be visible, but this method should not behips is significant. Joint aspirate will be clear and relied upon. For older children with an irritablestraw coloured and depressurizing the joint leads hip a plain radiograph is mandatory to excludeImaging, Volume 14 (2002) Number 3 181
  4. 4. D Wilson and G Allen predicting osteonecrosis by assessing vascular supply to the epiphysis [38]. MRI also has important roles in surgical planning and in detecting occult disease in the opposite hip. It is also valuable in assessing the late sequelae of Perthes disease [39, 40]. Slipped epiphysis Older children (8–14 years) may suffer from slipped upper femoral capital epiphysis (SUFE). This typically occurs in boys heavier than average and is thought to be the result of mechanical stress on the immature growth plate. Presentation is also with pain and limping of short duration.Figure 6. A frog lateral view of a child with sus-pected slipped upper femoral capital epiphysis; The only effective treatment is surgical fixation,appearances are normal. most commonly achieved by inserting pins into the epiphyses via the femoral neck. If treatment is delayed the slip will worsen with considerably increased risk of osteonecrosis in the displaced epiphysis and severe long-term consequences [41, 42]. Detection and treatment are therefore urgent. Whilst ultrasound will show an effusion in 75% of cases, and may show the step in the contour of the femoral head [43–45], it is not as safe and effective as plain radiograph examination using a frog lateral projection. SUFE represents a Salter– Harris 1 type lesion of the proximal femoral epiphysis. The slip most often occurs in a postero- medial direction and may be difficult to see on anteroposterior (AP) radiography [46]. A frog lateral is mandatory. It is reasonable to omit the conventional AP film to reduce radiation dose toFigure 7. The same child as in Figure 6, 1 month the patient. MRI is useful to asses direction andlater, showing contour changes and sclerosis of severity of the slip, especially in planning surgeryPerthes disease. [47]. It is particularly useful in detecting occult or subtle slip in the opposite asymptomatic hip, which may occur in up to 60% of cases. This examination should be performed prior to surgery on the affected hip as prophylactic pinning under the same anaesthetic is possible [48] (Figures 9–11). Investigation of irritable hip From the above it should be apparent that a child with an irritable hip should be seen as an emergency. The clinician should take a history and confirm the hip as the origin of pain by clinical examination. Ultrasound examinationFigure 8. Established Perthes disease with frag- should be arranged as an emergency [49, 50]. Ifmentation and flattening of the right femoral capital there is no joint effusion plain radiography shouldepiphysis. be undertaken [44, 45]. If this is normal then other causes of pain should be considered, e.g. retro-slipped epiphysis and Perthes disease [31]. Children caecal appendicitis, muscle strain and referredwith recurrent irritable hip should be examined by back pain.MRI as this technique may detect the condition If ultrasound examination shows fluid, awhen plain radiograph changes have not yet therapeutic and diagnostic aspiration should beoccurred [32–37] (Figure 3). Gadolinium (Gd) performed. Fluid should be sent for urgent GramDTPA enhancement may prove to be useful in stain and culture (Figures 12 and 13).182 Imaging, Volume 14 (2002) Number 3
  5. 5. Imaging of children’s hipsFigure 9. Early slipped epiphysis missed as the subtlechanges were not noticed and a lateral view was notperformed. Figure 11. MRI of advanced slipped epiphysis.Figure 10. 6 weeks after the image in Figure 9, theslip was recognized. There is now significant change,the epiphysis being rendered avascular with a pooroutcome. Figure 12. Ultrasound of a normal hip without an effusion. In older children (over 8 years) plain radiog-raphy in a frog lateral should be performed. Presentation varies greatly from an acutely In complex or recurrent cases, MRI should be painful region, immobility and systemic toxicityconsidered as an additional investigation [51, 52]. through to a completely occult disease with minimalIf MRI is not available there is a role for isotope local symptoms and just s general sense of illbone scintigraphy to detect occult bone lesions health.[53]. Acute infection is typified by bone oedema and subperiosteal reaction. The latter may be seen on plain radiography but both are readily apparent on MRI. The oedema extends beyond the areaOsteomyelitis that is histologically identifiable as active inflam- Bone infection may be primary due to blood matory response but it is difficult, if not impossible,borne organisms or secondary due to implantation, to distinguish this margin using imaging. It hassurgery or other forms of trauma. Occasionally been suggested that areas of true infection wouldinfection spreads to bone from septic arthritis. enhance with intravenous Gd DTPA injection onImaging, Volume 14 (2002) Number 3 183
  6. 6. D Wilson and G Allen Juvenile arthritis Juvenile arthropathy may present in the hip, although other joints such as the wrist or knees are more common presenting locations. It should be considered as a possible diagnosis in recurrent or complicated cases where diagnosis of transient synovitis is in doubt. Synovial reaction will be visible on ultrasound as thickening and irregular- ity of the capsule. MRI may be more difficult to interpret as the high signal from fluid in the joint seen on T2 weighted or short tau inversion recovery (STIR) images will be the same signal as exhibited by thickened and oedematous synovium [56] (Figure 14). Intravenous Gd DTPA enhancement would resolve this issue but ultrasound is cheaper, faster and more acceptable to the patient. Ultrasound is the imaging method of choice for detectingFigure 13. Ultrasound of a hip with a substantial effusion and pannus [57] and it has a very usefuleffusion. Aspirate was sterile. The appearances of role in follow-up studies [58].septic arthritis may be identical. TraumaMRI, however, this is not a reliable test and in Fractures and dislocations around the hippractice it is rare for contrast enhancement to are rare in children [59, 60]. They tend to beassist in management. Subperiosteal reaction may associated with high energy injuries. Fracturesbe detected using ultrasound. A positive finding should be apparent on plain radiography buton ultrasound is very specific but a negative study minimally displaced fractures and stress lesionsdoes not exclude acute osteomyelitis. may not. MRI is the definitive test and will show Chronic infection and acute infection after all fractures as low signal lines on T1 weightedantibiotic therapy are best studied by a combina- images surrounded by high signal material on T2tion of plain radiographs to detect bony destruc- weighted or STIR sequences. MRI also has a roletion and sclerosis, with MRI to show the extent of in complex fractures of the acetabulum when CT isdiseased bone, abscess within and outside bone not conclusive [61]. Non-accidental injury shouldand the extent and nature of soft tissue involve-ment [54]. Ultrasound is useful in excluding ordefining soft tissue abscesses [55]. CT is sometimesuseful in defining the shape and extent of scleroticsequestered fragments. The response to drugtreatment and planning of surgical debridementdepends very much on follow up studies. SerialMRI studies are invaluable in deciding timing andextent of surgery. Again, contrast enhancementrarely alters clinical decisions. Tumours may mimic infection and vice versa.In most cases biopsy is indicated and MRI will beimportant in deciding where to biopsy and viawhich route. Infection in bone is notorious for thedifficulty in identifying the organisms. Even inproven and definite osteomyelitis only 30% ofbiopsy specimens will grow organisms. For thisreason it is important to send biopsy material forhistological examination as this is more often themeans by which infection is established. Imageguided needle biopsy is valuable. However, inchildren an open biopsy under general anaesthesiais not only kinder but may also treat symptomsas the marrow oedema may be depressurized, Figure 14. T2 weighted coronal MRI of a joint effu-relieving some of the pain. sion and synovitis in juvenile arthritis.184 Imaging, Volume 14 (2002) Number 3
  7. 7. Imaging of children’s hipsalways be considered in younger age groups. 5. Terjesen T. Ultrasonography in the primary evalua-Ultrasound can also pick up fractures in the tion of patients with Perthes disease. J Pediatr Orthop 1993;13:437–43.younger patient. 6. Terjesen T. Ultrasound as the primary imaging Acute chondral injuries due to sheering forces method in the diagnosis of hip dysplasia in childrenmay cause an acute arthropathy. If there is a aged ,2 years. J Pediatr Orthop B 1996;5:123–8.resulting defect in the articular surface, symptoms 7. Poul J, Bajerova J, et al. Selective treatmentmay persist and fail to resolve. Conventional MRI program for developmental dysplasia of the hip in an epidemiologic prospective study. J Pediatrmay show the lesion especially on T2 weighted fast Orthop B 1998;7:135–7.spin echo images, although it may be necessary to 8. Finnbogason T, Jorulf H. Dynamic ultrasono-perform MR arthrography to be sure. CT arthrog- graphy of the infant hip with suspected instability.raphy is also effective but is less suitable in A new technique. Acta Radiol 1987;38:206–9.children as the radiation burden is large. 9. Joseph KN, Meyer S. Discrepancies in ultrasono- Muscle strains and tears may mimic irritable graphy of the infant hip. J Pediatr Orthop B 1996;5:273–8.hip. They may be invisible on all imaging but 10. Poul J, Garvie D, et al. Ultrasound examination ofsignificant tears will be well seen on ultrasound as neonate’s hip joints. J Pediatr Orthop B 1998;7:59–defect in the myofibrillar structure, oedema and 61.scar tissue. Dynamic stress ultrasound will show 11. Marks D, Clegg J, et al. Routine ultrasoundmuscle tears by the retraction of muscle and screening neonatal hip instability. Can it abolish late-presenting congenital dislocation of the hip.bulging of the margins of the tear. In the acute J Bone Joint Surg 1994;76:534–8.phase, MRI of the affected area may be the most 12. Davids JR, Benson LJ, et al. Ultrasonography andsensitive test. developmental dysplasia of the hip: a cost-benefit Growth plate injuries are a particular problem analysis of three delivery systems. J Pediatr Orthopin children. Their management depends on the 1995;15:325–9. 13. Clegg J, Bache CE, et al. Financial justification forextent and the skeletal age of the child. MRI is routine ultrasound screening of the neonatal hip. Jthe best method of studying the nature of the Bone Joint Surg Br 1999;81:852–7.injury [62]. 14. Exner GU, Frey E. [Hip dysplasia in infancy. Proton spin tomography and computerized tomo- graphy]. Orthopade 1997;26:59–66. (In German.) 15. Tegnander A, Terjesen T. Reliability of ultrasono-Snapping hip graphy in the follow-up of hip dysplasia in children above 2 years of age. Acta Radiol 1999;40:619–24. A variety of clicks and snaps may occur around 16. Court C, Carlioz H. Radiological study of severethe hip. These are most common in teenage girls. proximal femoral focal deficiency. J Pediatr OrthopThey include iliopsoas snaps, iliotibial tract 1997;17:520–4.snapping, greater trochanteric bursitis and glenoid 17. Kashiwagi N, Suzuki S, et al. Prediction oflabral injuries. Static ultrasound will demonstrate reduction in developmental dysplasia of the hip by magnetic resonance imaging. J Pediatr Orthopinflamed bursae and thickening whilst dynamic 1996;16:254–8.ultrasound is much more useful as it will show the 18. Lin CJ, Romanus B, et al. Three-dimensional char-clicking or snapping tendon [63–65]. Local anaes- acteristics of cartilaginous and bony componentsthetic blocks of the snapping tendon guided by of dysplastic hips in children: three-dimensionalimaging are useful in confirming diagnosis when computed tomography quantitative analysis. J Pediatr Orthop 1997;17:152–7.more invasive forms of treatment are being 19. MacDonald J, Barrow S, et al. Imaging strategies inconsidered. 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  9. 9. Imaging of children’s hips64. Wunderbaldinger P, Bremer C, et al. Efficient 67. Grainger AJ, Elliott JM, et al. Direct MR radiological assessment of the internal snapping arthrography: a review of current use. Clin Radiol hip syndrome. Eur Radiol 2001;11:1743–7. 2000;55:163–76.65. Choi YS, Lee SM, et al. Dynamic sonography of 68. Erb RE. Current concepts in imaging the adult hip. external snapping hip syndrome. J Ultrasound Med Clin Sport Med 2001;20:661–96. 2002;21:753–8. 69. Petersilge CA. MR arthrography for evaluation of66. Ghebontni L, Roger B, et al. MR arthrography the acetabular labrum. Skeletal Radiol 2001;30:423– of the hip: normal intra-articular structures and 30. common disorders. Eur Radiol 2000;10:83–8.Imaging, Volume 14 (2002) Number 3 187