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Role of Medical Imaging in Developemental Dysplasia of Hip
Dr. Muhammad Bin ZulfiqarAlnoor Diagnostic Centre
Aims• Brief introduction• Tests• Anatomy• Ultrasound • Radiograph• CT• MRI
DEVELOPMENTAL DYSPLASIA OF HIP (DDH)• CONGENITAL DYSPLASIA OF HIP• Deformity of acetabulum due to disrupted relationship between
femoral head and acetabulum• DDH is composed of two elements: • (1) instability and • (2) abnormal morphology.
• M:F—1:4 - 1:8
DDH—Types• Normal hip• Lax = subluxable hip• Concentric dislocatable unstable hip• Decentered subluxed hip• Eccentric dislocated hip
Ortolani’s sign• Hold the knees and abduct the hip while
lifting up on the greater trochanter• A positive test is feeling the dislocated hip
clunk into the acetabulum.
Barlow Provocative / dislocation test• Adduct and push posteriorly on
the hip• A positive test is feeling the hip out
of the acetabulum
Asymmetrical thigh folds• Indicative of abnormal hips• Also seen in infants with abnormal hips
• Widened perineum• Prominent greater trochanter
Galleazzi’s / Allis sign• Allis sign = Galeazzi sign = affected knee is
lower with knees bent in supine position• In bilateral hip abnormality asymmetry is
not a feature.
Lines and Angles
Line of Hilgenreiner
• Line connecting superolateral margins of triradiate cartilage
Perkin's line
• Vertical line to Hilgenreiner's line through the lateral rim of acetabulum
Shenton's curved line
• Arc formed by inferior surface of superior pubic ramus(= top of obturator foramen)+ medial surface of proximal femoral metaphysis to level of lesser trochanter• Disruption of line (DDx: coxa
valga)
Acetabular angle I index
• Slope of acetabular roof= angle that lies between Hilgenreiner's line and a line drawn from most superolateral ossified edge of acetabulum to superolateral margin of triradiate cartilage
Center-edge angle of Wiberg• Angle subtended by one line drawn from the acetabular edge to
center of femoral head+ second line perpendicular to line connecting centers of femoral heads• <25° suggests femoral head instability
• Fig. 2—Measurement of center-edge angle. A, Drawing shows center-edge angle (CEA), which is measured by drawing line through center of both femoral heads on well-centered anteroposterior pelvis radiograph perpendicular line in femoral head of interest and line through lateral margin of acetabulum and femoral head. Angle formed between perpendicular and lateral margin of acetabulum is CEA. B, Anteroposterior pelvis radiograph in 38-year-old woman shows dysplastic left hip (CEA < 20°).
Ultrasound• Reference standard in an infant before 6 months• It is a nonionizing, quick, and portable examination • Both Dynamic and Standard static views.
• American College of Radiology recommends • Coronal view in the standard planes at rest • Transverse view of the flexed hip with and without stress.
Coronal View• AC—acetabular cartilage• C---Capsule• GT---greater trochanter• H---cartilaginous femoral head• IL---ilium• L---labrum• LT / P---Ligamentum teres / pulvinar
complex• M---femoral metaphysis• Tr---triradiate cartilage
Coronal View• The ultrasound transducer is placed
parallel to the lateral aspect of infants hip
Coronal Ultrasound Image• C---Capsule• G---gluteus muscles• GT---greater trochanter• H---cartilaginous femoral head• IL---ilium• IS---ischium• L---labrum• Tr---triradiate cartilage
Transverse anatomic illustration• AC—acetabular cartilage• G---gluteus muscle• GT---greater trochanter• H---cartilaginous femoral head• C---Capsule• Is---ischium• IL---ilium• L---labrum• LT / P---Ligamentum teres / pulvinar complex• M---femoral metaphysis• Tr---triradiate cartilage
Transverse flexion view• The hip and knee are flexed 90 and the
ultrasound transducer is placed perpendicular to the lateral aspect of the infants hip.
Transverse flexion view• G---gluteus muscle• H---cartilaginous femoral head• IS---ischium• L---labrum• FS---femoral shaft• M---femoral metaphysis
Alpha and Beta Angles
Alpha angle• Angle between straight lateral edge of
ilium and bony acetabular margin (coronal view); determines sonographic hip type
• Coronal ultrasound of a normal right hip. Note how the echogenic iliac bone bisects the femoral head. The alpha angle in this study is measured to be > 60 degrees.
Beta angle• Angle between straight lateral edge of
ilium and fibrocartilaginous acetabulum—determines nuances of sonographic hip type
Sonographic Findings• Screening period: >2 weeks and up to 4-6 months of age• @ Relationship of femoral head & acetabulum• Femoral head position at rest in neutral position• Hip instability under motion + stress maneuvers• Dislocated(= eccentric) hip can be reduced (Ortolani positive):• Hypoechoic femoral head not centered over triradiate cartilage
between pubis+ ischium (on transverse view)
Sonographic Findings• Increased amount of soft-tissue echoes ("pulvinar") between femoral
head and acetabulum• Cartilaginous acetabular labrum interposed between head and
acetabulum (inverted labrum)• Posterior+ superior dislocation of head against ilium• Equator sign = <50% of femoral head lies medial to line drawn along
iliac bone (on coronal view): >58% coverage is normal ; 58% to 33% coverage is indeterminate; <33% coverage is abnormal
• Ultrasound images with developmental dysplasia of hip shows α angle (dashed line) is abnormal, measuring 45° and 43° respectively. Acetabulum is shallow and femoral head is laterally dislocated. There is pulvinar fat hypertrophy (arrowhead) and blunting of bony acetabulum (thick solid arrow).
Coronal sonogram of the hip with calculation of the d / D ratio. Coverage of 58% or greater is considered normal
DDH with normal alpha angle• Alpha angle is 62
Sonographic Findings• Femoral head• Disparity in size of directly visualized unossified femoral head• Disparity in presence+ size of ossific nucleus
Sonographic Findings• Acetabulum• Delayed ossification of acetabular corner• Wavy contour of bony acetabulum with only slight curvature• Abnormally acute alpha angle ( = angle between straight lateral edge
of ilium+ bony acetabular margin)• a >60° in an infant is normal• a 55-60° can be normal <4 weeks of age• a <55° occurs in an immature acetabulum• 4°-6° interobserver variation!
• Coronal ultrasound of the left hip in an infant shows a shallow acetabulum , fatty stpulvinar between the femoral head and deepest acetabulum st, and lateral subluxation of the femoral head . (Right) Transverse ultrasound confirms the shallow acetabulum st , stfatty pulvinar st, and lateral subluxation of the femoral head st. Dynamic investigation is used to demonstrate whether or not the femoral head is reducible or unstable. Ultrasound is the imaging modality of choice for DDH in an infant.
st.
, stst,
DDH—Types• Normal hip• Lax = subluxable hip• Subluxability up to 6 mm is normal in newborns (still under influence
of maternal hormones); decreasing to 3 mm by 2nd day of life
DDH—Types• Concentric dislocatable unstable hip• = joint laxity allowing non displaced femoral head to become subluxed
I dislocated under stress• • Barlow positive• slight increase in femoral anteversion• mild marginal abnormalities in acetabular cartilage• early labral eversion• Prognosis: 60% will become stable after I week; 88% will become
stable by age of 2 months
DDH—Types• Decentered subluxed hip• femoral head shallow in location• loss of femoral head sphericity• increased femoral anteversion• early labral inversion• shallow acetabulum
DDH—Types• Eccentric dislocated hip• femoral head frankly displaced out of acetabulum• (a) reducible = Ortolani positive• (b) irreducible= Ortolani negative• accentuated flattening of femoral head• shallow acetabulum• limbus formation(= inward growth+ hypertrophy of labrum)• "hip click" = usually result of joint capsule and tendon stretching+
snapping (often confused with "hip clunk")
Plain Radiograph• AP pelvic radiograph: >4- 6 months of age (von Rosen view = legs
abducted 45° + thighs internally rotated)• Not reliable first 3 months of life!• Proximal + lateral migration of femoral neck:• eccentric position of proximal femoral epiphysis (position estimated
by a circle drawn with a diameter equivalent to width of femoral neck)• Interrupted discontinuous arc of Shenton's line
Normal Radiograph• B, Normal anteroposterior radiograph of hips in
2-year-old boy shows α angles of right and left hips are normal for age, measuring 18° and 20°, respectively. Note how contour of acetabula changes with age. Ossified femoral epiphyses are symmetric and well seated within acetabula. Hilgenreiner (long-dashed line), Perkins (short-dashed line), and Shenton (dotted line) lines are superimposed. Femoral epiphysis is appropriately situated in inferomedial quadrant. Center edge angle is formed by vertical line through center of femoral head and line from center to lateral acetabular roof (solid lines).
Normal Acetabular Angle• Normal anteroposterior
radiograph of hips in 6-month-old boy shows acetabular angles in right and left hip (lines) are normal for age, measuring 22° and 24°, respectively.
• A, Anteroposterior radiograph obtained at 6 months of age shows shallow left acetabulum with steep roof, compatible with DDH.
• B, Anteroposterior radiograph obtained at 1 year of age shows interval growth of left femoral epiphysis; however, it remains smaller relative to right femoral epiphysis. Left acetabular dysplasia persists.
• A, Initial radiograph shows superolateral subluxation of right femoral head, valgus deformity, and acetabular dysplasia.
• B, Postoperative radiograph after iliac osteotomy and femoral varus osteotomy shows interval healing and improved acetabular roof coverage of femoral head. Previous valgus deformity has been corrected.
• Frontal radiograph of the pelvis in a 1-year-old child with a dislocated right hip. The degree of ossification of the femoral head on the dislocated side is decreased compared with that of the normally located left hip. The abnormally located hip articulates with a false neoacetabulum.
Plain Radiograph• Line drawn along axis of femoral shaft will not pass through upper
edge of acetabulum but intersect the anterior-superior iliac spine (during Barlow maneuver)• Apex of metaphysis lateral to edge of acetabulum• femoral shaft above horizontal line drawn through the Y-
synchondrosis• Unilateral shortening of vertical distance from femoral ossific nucleus
I femoral metaphysis to Hilgenreiner's line
Plain Radiograph• Femoral ossific nucleus I medial beak of femoral metaphysis outside
inner lower quadrant of coordinates established by Hilgenreiner's + Perkin's lines• Acetabular dysplasia= shallow incompletely developed acetabulum:• Acetabular angle >30° strongly suggests dysplasia• Development of false acetabulum• Delayed ossification of femoral epiphysis (usually evident by 4 months
(range, 2nd to 8th months) of life
• Frontal radiograph of the pelvis obtained with the legs in the frog-leg position indicates that the plane of the femoral projection is toward the triradiate cartilage, suggesting that the hips are reducible.
• 16M/F Healed Salter Osteotomy After three years
10-week-old female, bilateral DDH.
Bilateral Hip Dislocation.
Fluoroscopic image from arthrography in 15-month-old girl with left developmental dysplasia of hip shows contrast material within joint. Femoral head is seated in dysplastic acetabulum.
Arthrography
• performed intraoperatively at the time of reduction. • Identify Obstacles to successful reduction,
such as limbus eversion,• Arthrography during reconstructive
osteotomy helps obtain concentric reduction of the hip.
• Arthrogram of congenital hip dysplasia. (A) Arthrogram of the right hip in the neutral position in a 1-year-old girl with congenital subluxation of the hip shows the typical displacement of the hip lateral to, but below the acetabular labrum. There is accumulation of contrast agent in the stretched capsule (arrow), and the ligamentum teres is elongated. (B) In the frog-lateral position, the head moves more deeply into the acetabulum, but subluxation is still present.
• Arthrogram of congenital hip dislocation. (A) Anteroposterior radiograph of the right hip in an 8-year-old girl demonstrates complete superolateral dislocation of the femoral head. Note the shallow acetabulum. (B) Arthrogram of the hip shows a deformed cartilaginous limbus and stretching of the ligamentum teres. The femoral head lies superior and lateral to the edge of the cartilaginous labrum. Note the accumulation of contrast agent in the loose joint capsule.
CT Scan• CT (during cast treatment I attempted closed reduction):• Sector angle = angle between line drawn from center of femoral head
to acetabular rim+ horizontal axis of pelvis (=reflection of acetabular support)• Anterior acetabular sector angle <50°• Pposterior acetabular sector angle <90°• Horizontal acetabular sector angle <140
• CT of congenital hip dislocation. Axial section through the proximal femora and hips of a 6-month-old boy shows posterolateral dislocation of the left hip. The right hip is normal.
AASA, PASA & HASA• Anterior acetabular sector angle is created by drawing lines through
centers of femoral heads and line tangential to anterior lip of acetabulum. Adequate anterior acetabular coverage is present when anterior acetabular sector angle is greater than 50°.• PASA is measured by drawing lines through centers of femoral heads and
line tangential to posterior lip of acetabulum. Adequate posterior acetabular coverage is present when PASA is greater than 90°.• HASA is measured by drawing lines from anterior lip of acetabulum
through center of femoral head and posterior lip of acetabulum. Adequate global acetabular coverage is present when HASA is greater than 140°.
• Drawing shows measurement of anterior acetabular sector angle (AASA), posterior acetabular sector angle (PASA), and horizontal acetabular sector angle (HASA). Values are measured on axial CT one cut above greater trochanters.
• Mild right hip dysplasia. AP pelvic view shows lateral CE angle measuring less than 20º (lateral CE angle = 19º, considered diagnostic of hip dysplasia); and axial CT image shows deficient anterior, posterior and global acetabular coverage with decreased AASA, PASA and HASA (AASA = 46º , PASA = 87º ad HASA = 133º).
• CT image in 29-year-old woman shows dysplastic hip with deficient anterior coverage (anterior acetabular sector angle < 50°), deficient global coverage (HASA < 140°), and borderline deficient posterior coverage (normal PASA > 90°).
• A, Preoperative radiograph showing left DDH.• B, Postoperative CT image was obtained to
evaluate relocation of left hip after iliac and femoral varus osteotomy.
• Treatment of congenital hip dysplasia. (A) Anteroposterior radiograph of the pelvis in a 1-year-old boy demonstrates the typical appearance of congenital dislocation of the left hip. (B) After conservative treatment with a Pavlik harness at age 2, there is still subluxation. Note the broken Shenton-Menard arc. At age 3, after further conservative treatment by skin traction and application of a spica cast, there is almost complete reduction of subluxation, as demonstrated by contrast arthrography (C). (D) CT scan, however, demonstrates some minimal residual lateral displacement of the femoral head, as evidenced by the medial accumulation of contrast.
Role of MRI• Reserved for difficult cases• The major advantage of MRI is the ability to delineate soft-tissue
structures as well as osseous structures without ionizing radiation• Many MRI studies are ordered in the postoperative period, usually
after reduction and spica cast placement.
• Fig. 8—Fat-suppressed equivalent T1-weighted image in normal left hip in 11-month-old girl with left developmental dysplasia of hip with structures routinely identified by MRI: A = triradiate cartilage, B = labrum, C = ilio-psoas tendon, D = un-ossified femoral head, E = ossified femoral head, F = acetabular cartilage, G = acetabulum. Note dysplastic right hip with subluxed femoral head (arrow).
• 11-month-old girl with hip click (patient B). A, Anteroposterior radiograph shows lateral dislocation of right hip. Right acetabulum is steep and shallow. Right femoral head ossification is delayed. B and C, MRI was performed immediately after right hip arthrogram, closed reduction, and adductor release. Axial T1-weighted images show interval reduction of right hip with mild persistent posterior subluxation. Acetabulum is shallow. Compared with normal left side (solid arrow, C), right femoral head ossification is delayed (long solid arrow, B). Anterior labrum is mildly inverted (short solid arrow, B). Significant pulvinar hypertrophy (dotted arrow, B) was noted. D, Radiograph obtained 6 months after surgery shows interval improvement with mild persistent subluxation of right hip. However, right acetabulum is still dysplastic with abnormal acetabular angle. Right acetabular angle measures 34° and left acetabular angle is 23°.
E F G H • Fig. 9 (continued)—11-month-old girl with hip click (patient B). E and F, Follow-
up MRI was performed to assess whether second operation was indicated. Axial (E) and coronal (F) fat-suppressed equivalent T1- weighted images show hypertrophic acetabular cartilage and good morphology of cartilage portion of right femoral head, overall improved since prior MRI. G and H, Coronal non–fat-suppressed (G) and fatsuppressed (H) equivalent T1-weighted images show mild right pulvinar fat hypertrophy (arrow) with improved position of femoral head relative to acetabulum since prior MRI.
• I and J, Coronal T1-weighted images with fat saturation show superimposed bony acetabular index angle (I) and cartilaginous acetabular index angle (J). Bony acetabular index measures 39.6°, which is fairly concordant with 34° acetabular angle measured on radiographs. Hypertrophic acetabular cartilage contributes to 15° cartilaginous acetabular index, which is still abnormal but relatively closer to normal range (mean cartilaginous acetabular index in 2-year-old is 8.2 ― 1.9 [40]) compared with measured bony acetabular index. This examination served as guide for further orthopedic management. Compared with radiographs, femoral head appears more concentrically located in acetabulum. Surgeon subsequently elected to treat more conservatively.
Complications• Degenerative joint disease• Avascular necrosis of femoral head
Treatment• (1) Flexion-abduction-external rotation brace (Pavlik harness) I splint I
spica cast• (2) Femoral varus osteotomy• (3) Pelvic (Salter) I acetabular rotation• (4) Increase in acetabular depth (Pemberton)• (5) Medialization of femoral head (Chiari)
• A, Anteroposterior radiograph shows shallow steep dysplastic left acetabulum (long arrow), lateral subluxation of left hip, and delayed ossification of left femoral head (short arrow). Radiopaque objects seen at bottom of image are buttons overlying patient.
• B, Axial T2-weighted image with fat saturation obtained after interval reduction and with spica cast in place shows mild residual subluxation of left femur and fibrofatty pulvinar hypertrophy with small effusion. Note signal intensity loss of fibrofatty pulvinar with fat saturation (long arrow). Anterior labrum is inverted (short arrow). Right hip appears normal with normal-sized spherical femoral head compared with small and aspherical left femoral head.
• C, Coronal T1-weighted image shows lateral subluxation of left femoral head and fibrofatty pulvinar hypertrophy (arrow). Note delayed ossification and aspherical shape of left femoral head.
Inverted Superior Labrum
Inverted Superior Labrum
Inverted Posterior Labrum
Inverted Posterior Labrum
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