neonatal hip normal
ultrasound image the ilium must be horizontal. you should see a sharp ilium-roof angle and a centrally located, rounded femoral head.
a line drawing of the image to the right.
ultrasound image normal= >= 55%. most manufacturers provide a software calculation package that will automatically calculate the % coverage after the baseline/ and femoral head are drawn.
ultrasound image in transverse view during abduction and the less stable, adduction.
ultrasound image. subluxed superiorly. note the rounded/indented ilium-acetabular roof angle (green). the abnormally elevated labrum (yellow) and femoral head(red circle) would produce an abnormally shallow alpha angle.
role of ultrasound
to ensure the correct development and stability of neonatal hips.
- clicky hip
- assymmetrical creases
- family history congenital hip dysplasia/dislocation (9:1 f:m)
- breech lie during the pregnancy
- limited abduction
- deformities of the foot
if the baby is greater than 6 months, the hips may be too ossified to examine adequately with ultrasound. if the baby is 12 months or greater and presents with symptoms, an xray should also be performed.
it is recommended that the most accurate time to scan the baby is over 6 weeks .this is because the hips are more mature and not lax. otherwise false positives can occur as the baby’s hips initially have some natural laxity.
the nappy can be left on and just open the tabs on the side you are scanning to get access to the hip coronally.
- this depends on the age and size of the child.
- a 12mhz linear array probe can be used for a newborn but as the child grows a 7mhz will be required to get adequate penetration. if the tri-radiate cartilage cannot be seen, you will need to decrease the frequency.
- the scan can only be performed when the ossification of the proximal femoral epiphyses is not too far advanced.
- a machine with cine capabilities and a foot switch is helpful as you can keep your hands on the baby to capture the correct image.
the baby’s hip must be dynamically scanned with coronal and transverse evaluation with the hip in:
- flexion with and without stress
there are numerous ways that you can scan the baby.
- lie the baby supine (have the baby’s feet facing you).
- the baby can lie decubitus with a pillow/towel rolled up at the back to give them support.
- using a specific ‘cradle’. *
*please note that we feel a cradle is not ideal to use as it does not allow movement of the baby’s leg to assess dislocation with stress in adduction ,abduction, flexion or extension.
the graf chd classification
this method is adopted less commonly with the dynamic assessment and depth of coverage seen more favourable using modern equipment. a coronal view of the hip is obtained with:
- the ilium horizontal.
- a sharp, well defined acetbular roof.
- a rounded femoral head.
- the baseline: along the ilium, through the femoral head.
- the roof line: along the acetablular roof intersecting the baseline.
- the inclination line: across the top of the femoral head, through the labrum and intersecting the 1st two lines.
- subluxable: yes/no
- laxity: yes/no
- bony coverage of fce : _____% (most manufacturers have a %coverage calculator on the machine)
- alpha angle: ____ � beta angle: ____ �
- acetabular promontory: angular/rounded/flat
basic hardcopy imaging
a neonatal series should include the following minimum images of each hip;
- coronal with % coverage
- coronal with alpha/beta angles
- transverse abduction
- transverse adduction
- stress view