Top tips for shallow hips (Part 2 - Dysplasia) - The clinical assessment!

Welcome back – be sure to read the first instalment of this blog before cracking on! READ HERE

Right then, clinical exam time. We are fully equipped with our differential diagnoses and index of suspicion that for Jade is a little higher for DDH than others. What are the things we need to look out for on our exam that will raise it further or nip this thought train in the bud? This is how I would approach it.

• Before I get Jade on the plinth – lets have a look at her Beighton’s score. She is skeletally mature and well into her 20’s so we’re definitely looking for more than a 5 or 6 out of 9 to be suspicious of global soft tissue laxity (there is no universal agreement on cut off). Jade scores a 7, it’s just her elbows that let her down from an A*/100%!
• Usual functional tasks e.g. squatting, bending. I’m not bothered about technique because I’m an ecologically informed therapist and know this doesn’t matter (don’t @ me). I’m more looking at if she is fearful or avoidant of certain positions, how much is she mentally preparing to do these activities. Not so much important for a ‘structural diagnosis’ but an extremely important part of evaluating where Jade is at. She’s only a little hesitant of deep squatting but does it without much thought.
• Range of motion – This bit I value A LOT. A shallow acetabulum and dysplastic femoral head can give rise to a larger than expected ROM profile (REF). I am focusing particularly on the internal and external rotation. In my own experience this is a giveaway, a ‘key piece of evidence’ in our investigation into the hip pain that just won’t go away.

We pick up on a loss of internal rotation at 90 degrees hip flexion quite well because it can indicate underlying advanced hip OA or even a CAM morphology depending on clinical history (Bonus piece of information: if you have someone with a Drehmann sign then that hip is going to be interesting to look at on an X-Ray…)

But excessive internal rotation or external rotation is just as important a clinical finding. It could mean that the bony restraints that usually limit movement aren’t their usual shape. Don’t make the mistake of missing this just because internal rotation isn’t restricted. Jade has 60 degrees internal rotation.

• If I am being perfectly honest. That is enough for me if they are coming up with positive tests and enough subjective history. Maybe throw in a FADDIR test just to make sure it’s not negative (High sensitivity but poor specificity, if it isn’t positive it might not be hip joint related)

Didn’t Jade say she had had an X-Ray? It had been reported as normal but unfortunately at this point in time, unless you know the radiologist or reporting radiographer has a specific awareness and drive to measure the angles they need to, it could be a good idea to get familiar with basics of assessing the lateral centre edge angle (LCEA) as a minimum for acetabular dysplasia.

The above is an example X-Ray from Radiopedia with some drawings of the lateral centre edge angle included.

What do we look to do when eyeballing an X-Ray? In brief, we are checking the film isn’t massively rotated which can make any measurements invalid (draw a line from middle of sacrum straight down, if it doesn’t bisect pubic symphysis we probably need a new X-Ray). Draw a circle of best fit around the femoral head and a line vertically down to the centre of the circle, next line up to the edge of the ‘sourcil’ which is the end of the weight bearing portion of the acetabulum.

Universal agreement has not been reached, however, <24 degrees could be considered borderline acetabular dysplasia and <18-20 degrees can be considered definite global acetabular dysplasia. We will say Jade’s X-Ray is looking about a 20ish from our attempt at measuring.

Does the femoral head look like a well formed sphere? Once you have seen a few dysplastic femoral heads you will know what I mean. Are the trochanters looking fairly symmetrical or could there be some femoral version issues? In fact Jades hip doesn’t look entirely spherical on either side.

At this point it is probably also worth mentioning Wilkin et al (2018) have also contributed to the literature with an understanding of different types of acetabular dysplasia. Having a smaller LCEA on X-Ray can demonstrate likely presence of global instability symptoms, but you can still have a dysplastic hip with a normal LCEA. This is because there are cohorts of patients who will have purely groin, or buttock symptoms relating to anterior and posterior instability respectively due to anterior / posterior acetabular wall deficiency. If the subjective history is still there, but the LCEA is normal, it might still be worth keeping DDH on the mind as it can only truly be ruled out with 3D imaging. (You can keep an eye out for measures of acetabular retroversion [ischial spine sign, posterior wall sign and crossover sign] and anteversion [Acetabular wall indicies] if you are really interested).

We aren’t radiologists or radiographers. For most of us, this level of X-Ray interpretation is not expected but I would argue it is well worth trying to read into more (REF), especially if you can access your local radiology system. At the end of the day, we are looking to flag up if a second opinion is needed on the images, not to get everything perfectly right.

Here ends part 2 of this blog series. Next up, what do we discuss with Jade moving forwards?