Paed hip – Graf angle caliper placement

[Linh]

Dear Steve,

I got a baby hip with severe dysplasia the other day and found it hard to place my roof and inclination line as there is significant rounding of the acetabulum and ilium junction. Below are my pictures. I did 2 attempts on the LT. Can you critique?

If there is rounding, do you still draw the roof line from the point the ilium becomes rounded or do you draw the roof line tangential to the acetabulum? In that case, how do you draw your inclination line?

Best regards,
Linh

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[Linh]

Dont know why the pics wont show. I reupload the pics in the form of pdf here.

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[Stephen Bird]

Hi Linh,

Personally I like the first image you provided.
Your calliper placement on all images is as I would do them including the % coverage measurements.
I just think your first coronal image is a better scan plane than your second effort.

As far as calliper placement goes I do what you do and that is to put the baseline flat on the ilium. At the point where the ilium dives away from the baseline that is the “intersection point” where I put my inclination line and then line it up against the acetabular roof as you have done.

So I am happy with the first image.

This is a very dysplastic hip requiring an orthopaedic opinion and treatment.

Nice scan Linh.

Steve

[Linh]

Thanks Steve for your critique!

Just out of interest, do you take any further pics for your protocol? Any dynamic stress test?

[Stephen Bird]

I have a lecture on the topic so I will try and record it into a webinar for you.

In my workplace we don’t perform stress tests.

I know that a paediatric sub-specialised sonographer would frown upon this, however in a general radiology setting we are happy to screen the population of patients that are sent to us and characterise the into normal, immature requiring follow up, or dysplastic requiring a formal paediatric orthopaedic opinion and an assessment by a dedicated paediatric ultrasound service.
It is a bit like obstetrics really, if there is an abnormality detected we send it for a formal assessment at the Adelaide Women’s and Children’s Hospital.

When the tertiary level scan is performed stress tests are done.

I am not sure I want to be the one to dislocate a hip, I would rather that be done by a paediatric orthopod or sub-specialised sonographer / radiologist. Also I am not sure if our outcomes would be consistent if we are only performing them occasionally.

This methodology seems to work well.

Steve.

[Linh]

Agreed, I am reluctant to dislocate/subluxate a baby’s hip as a general sono just from the medicolegal standpoint.

Would there be a situation when the Alpha angle is under 60 deg but the coverage is over 50 %? If you are in this situation, what would you do to decide? Would you place more emphasis on the coverage over the Graf angles?

Linh

[Stephen Bird]

For me this is really an issue for the radiologist to decide on management in the report.
The Adelaide Women’s and Children’s Hospital has a chart on alpha angles and %coverage at various ages for hip development.
We would always recommend some follow up by a paediatrician when either measurement is below the expected value.
Then I think the paediatrician clinical examination is also important before deciding on management.

Steve

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