02/09/2023 at 9:14 pm #53256Jayeta ChoudhuryParticipant
The other day I got a case of snapping hip. I could feel the snap under my probe but couldn’t demonstrate the tendon moving on ultrasound. Some tips from you would be helpful.
04/09/2023 at 11:12 am #53279Stephen BirdKeymaster
These can be challenging.
With snapping hip, there are 3 types.
If it is an intra-articular snapping hip the scan will be normal as there is nothing we can see as the cause.
If it is an internal snapping hip we can see the snap.
You need to scan the femoral neck in long axis, so you have the transducer pointing to the patients opposite shoulder in the standard hip picture, then rotate the transducer exactly 90 degrees , so you are not axial , but rather 90 degrees to the neck of the femur. Then you need to slide the transducer up the femoral neck, onto the femoral head where you will see the dome of the femoral head covered by hyaline cartilage, and then keep going until you reach the next bony landmark which is the ilio-pectineal eminence (or if the like the anterior rim of the acetabulum). At this location you will see the echogenic iliopsoas tendon immediately on the bone and anterior to it you will see a crescent shaped muscle which is the medial fibers of iliacus. These are the main players in the internal snapping hip. Stop here and then ask the patient to go from their neutral position into hip flexion and abduction. So bring the knee towards the chest and outwards. When you do this you will see the iliopsoas tendon rotate with the medial fibers of iliacus (MFI) and rest in a position anterior to the MFI. Then ask the patient to move into extension and adduction (back where they started) and the iliopsoas tendon will rotate again on the MFI and should rest smoothy back on the bone of the iliopectineal eminence where it started. When you get a snap the returning movement is not smooth. The iliopsoas tendon gets caught on top of the MFI muscle and then rapidly snaps off of it, descending abruptly and crashing down on the iliopectineal eminence , causing the snap. The iliopsoas bursa lives on the iliopectineal eminence at this location and hence becomes inflamed if it occurs frequently.
You would think the scanning would be impossible with all of that hip flexion, extension, abduction and adduction going on, but it is not that bad as your transducer position is actually slightly above the hip joint. It is a little tricky and it is good to take the patient through a few practice maneuvers first as this teaches them what I require and also conforms that this provocative test actually makes the snap happen. Once they are practiced, they can do it for you and you can concentrate on scanning.
The last type of snapping hip is the lateral snapping hip. This is where the iliotibial band (ITB) gets caught on the greater trochanter and snaps forwards and backwards.
In my experience these patients usually have a large gluteus minimus tendon and this is the structure causing the catching. G-min is variable and can be larger or smaller in individuals. When it is congenitally large it catches the deep fascia of the ITB and the superficial fascia keeps moving (The ITB is a bilaminar structure). Then the superficial fascia of the ITB snaps to catch up and there is your snap.
They usually need to be standing and doing a “pelvic thrust” movement for the snap to occur, so it is often amusing.
They are the tips I have for you.
Have a great week scanning up there is beautiful Durgapur in West Bengal, India.
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