Measuring tears within the shoulder

It is a great question Vrutti,

In the long axis bird beak view, if it is a partial tear you are measuring the length of the supraspinatus tendon retraction. In the short axis view (transverse) you are measuring the width of the tear.

I consider supraspinatus to be 15mm wide, so 5mm anterior, 5mm mis and 5mm posterior in the short axis / transverse view.

So if a tear is 10mm wide and begins adjacent to the long head of biceps tendon I would say the tear is 10 wide and involves the anterior and mid portions of the SST with preservation of the posterior fibers.

If it is 15mm wide I say it is a complete tear of SST and if it is 25mm wide I say it is a complete tear of SST with some involvement of the anterior fibers of infraspinatus.

So I think these measurements in the short axis / transverse plane are really important.

The measurements in the long axis birds beak view I think are less important. Sure in a partial tear like a PASTA tear (partial thickness articular surface tear) it gives an idea of the size of the tear and I think this is important.

But with full thickness enthesis based tears the measurement is a bit binary with only 2 common patterns.

The first pattern is when the infraspinatus and the rotator cuff cable (deep reflection of the coracohumeral ligament) are still attached to the torn SST it will be held in place with the stump sitting right above the junction of the hyaline cartilage of the humeral head and the enthesis. You can measure the retraction here, but it is a bit tricky to know where to put the distal calliper. The measurement is always around 15mm (the length of the enthesis).

The other pattern is when the connection between the SST and infraspinatus and the rotator cuff cable have failed and then the retraction is much larger and the tendon stump disappears under the acromion where I cannot see it and hence can’t measure the retraction.

So in clinical practice I find myself giving detailed explanations of the width of these tears and the components of SST they involve, but for full thickness tears where the SST has been stripped from the enthesis (the most common type) I comment that the SST stump is held in place and visible at the proximal end of the enthesis (15mm retraction), or that the tendon stump has retracted beneath the acromion and is not visible.

I suspect the first option is worth seeking a surgical opinion depending on other circumstances, however the second option is likely not to be a surgical candidate.

The reason for this is that if the connections between the SST stump and the infra / rotator cuff cable are intact the muscle will have less atrophy as muscle activation is possible through the humeral attachments of the other two structures. Once these are destroyed the SST is completely detached and the muscle has no purchase and atrophy will be rapid.

I have some new schematics that I have made to explain this concept.

I just checked and they are not in the MSK fundamental webinar so I have recorded a new webinar this afternoon and I will upload it in the Fundamental MSK collection for you.

Thanks for the awesome question,

Happy scanning,

Steve.