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Dr/Ahmed Bahnassy Consultant Radiologist Riyadh Military hospital

Hip dysplasia imaging

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The presentation explains the different theories of DDH and the proper imaging ultrasound technique.

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Page 1: Hip dysplasia imaging

Dr/Ahmed Bahnassy

Consultant Radiologist

Riyadh Military hospital

Page 2: Hip dysplasia imaging

What is DDH

• The natural history of DDH dictates that this is not necessarily a simple task.

• DDH is composed of two elements:

• (1) instability and

• (2) abnormal morphology.

Page 3: Hip dysplasia imaging

Assesment

• The technique for performing an infant hip sonogram may vary depending upon one's belief as to pathophysiology.

• Initial focus of hip sonography by Graf was on acetabular morphology, using a single static sonographic view.

• Harcke et al, on the other hand, emphasized assessment of instability in addition to morphology and advocated a dynamic sonographic technique.

Page 4: Hip dysplasia imaging

• The current recommendation for sonographic examination of the infant hip incorporates assessment of both instability and morphology so the pathophysiology issue is resolved with respect to performance of the sonographic examination .

Page 5: Hip dysplasia imaging

Hip sonographyTABLE 1 -- HIP SONOGRAPHY FOR DEVELOPMENTAL DYSPLASIA OF THE HIP

View Key Feature Comment

Coronal neutral* A Acetabular morphology Measurement optional

Coronal flexion A Acetabular morphology Measurement optional

Stability (if stressed) Stress optional

Used with Pavlik harness

Transverse flexion A Stability Stress required (except during treatment)

Used with Pavlik harness

Transverse neutral Femoral head position Optional view

Data from Harcke HT, Grissom LE: Performing dynamic sonography of the infant hip. AJR Am J Roentgenol 155:837-844, 1990; with permission.

Page 6: Hip dysplasia imaging

Correct coronal view

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Correct transverse view

Page 8: Hip dysplasia imaging

I-Morphological assesment

• This system is based upon the appearance of the acetabulum in a coronal neutral position and describes measurement of acetabular slope (alpha angle) and position of the acetabular labrum (beta angle).

Page 9: Hip dysplasia imaging

Benefits

• It is a well-recognized feature of DDH that the condition changes with time.

• It is greater at birth and decrease spontaneously in the first few months of life without treatment.

Page 10: Hip dysplasia imaging

• Of particular relevance is the distinction of normal and abnormal in the first few weeks of life. It is recognized that a large number of newborns have a mild instability that has been described as physiologic laxity. In association with this is mild acetabular dysplasia consisting of a slightly increased angulation of the bony acetabulum as determined by Graf alpha angles (type 2A).

Page 11: Hip dysplasia imaging

How to make good exam

• The proper coronal view, whether the femur is in neutral or in flexion, contains three elements .

• (1) The echoes from the bony ilium should be in a straight line parallel to the surface of the transducer.

• (2) The transition from the os ilium to the triradiate cartilage must be seen definitively.

• (3) Finally, the echogenic tip of the cartilage labrum needs to be present in the same plane that contains the other two elements.

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Model view

Page 13: Hip dysplasia imaging

Take your measurements

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Page 15: Hip dysplasia imaging

• Graf classification of infant hips based on the depth and shape of the acetabulum as seen on coronal ultrasonograms.

• Type I: normal; characterized by a well-formed acetabular cup with the femoral head beneath the acetabular roof.

• Type II: immature in infants less than three months of age and mildly dysplastic in infants older than three months; characterized by a shallow acetabulum with a rounded rim.

• Type III: subluxated; characterized by a very shallow acetabulum with some displacement of the femoral head.

• Type IV: dislocated; characterized by a flat acetabular cup and loss of contact with the femoral head.

Page 16: Hip dysplasia imaging

Angle values

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Dislocated Type III

• Lateral displacement of femoral head.

• Soft tissue between femoral haead and acetabulum

cross sectional view

normal

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Dislocated hip type IV

coronal view

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II- Stability assesment• The assessment of instability incorporates

dynamic technique in two views that include application of stress.

• Both views are performed with the hip flexed: the transducer orientation is coronal for one view and axial for the other.

Page 20: Hip dysplasia imaging

Relax your patient

• Assessing the hip when the infant is not relaxed masks the presence of instability.

• To ensure a cooperative infant, it is recommended that a sonogram be performed in a quiet, semidarkened environment with a parent present and visible to the child.

• Bottle feeding the infant during the examination is helpful.

Page 21: Hip dysplasia imaging

• Examination by ultrasound is modeled after the clinical examination and is based upon the provocative test for dislocation of an unstable hip (Barlow test) or the reduction of a dislocated hip (Ortolani test).

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• With subluxation and lesser degrees of instability, the flexed hip tends to seat with abduction.

• Displacement is noted during adduction and stress.

Page 23: Hip dysplasia imaging

• The key feature of instability is the lateral movement (toward the transducer) of the femoral head along the ischium. This results in increased echogenic soft tissue medially.

• Whereas a normal hip shows slight changes in the appearance of the medial tissues between abduction and adduction, with instability, the thickness more than doubles

Page 24: Hip dysplasia imaging

Dynamic testing

• At rest :Normal.• With stress

subluxation occurs and B angle increases.

Page 25: Hip dysplasia imaging

Summary• Ultrasonic evaluation of DDH includes:

• I-Morphology assesment (Graf angles)

• II-Stability assesment (dynamic exam )

• Acquired data depend on proper technique.

Page 26: Hip dysplasia imaging