Hi Diane,
Lovely images again, and very common appearances so great to discuss them.
These tears are what I call atritive tears and they are just like an old piece of rope mooring a boat. The tendon (rope) frays and progressively loses its volume and strength as each little insult damages it further and the attachment to the mooring (greater tuberosity enthesis) also progressively becomes damages from years of small traumatic events. This is a common way the supra fails with a lifetime of small insults leading to a thin and weak tendon and then one last often trivial event leads to the full thickness failure.
I agree there is very likely to be a full thickness tear communication in this patient even if it is difficult to define and measure a clear defect the loss of tendon volume and general ysrepair of the enthesis make the diagnosis practically inevitable.
I think in the compression image you can see the tendon stump displaced from the greater tuberosity and staying in place as it is not a full complete width tear, however it is highly suggestive of a full thickness tear. The stump has some scar tissue between it and the enthesis (which has failed) and I think it is only granulation tissue stopping the fluid from moving into this space. If you scanned it acutely after that injury you would have seen blood / fluid passing through that space.
The supra long anterior image shows tendon thinning, heterogeneity and enthesis irregularity all suggestive of a progressing chronic attrition process leading to inevitable tendon failure.
I agree that tears in the mid / posterior supra are really common and like you I question the old teaching that “most” tears start anteriorly.
Enthesopathy is an integral component of supra failure and the presence of bony enthesis irregularity is a feature of virtually all supra tears (except critical zone and MTJ tears). So when I see enthesis irregularity I call it enthesopathy and I look at the adjacent tendon which will always look abnormal in some way. It doesn’t have to be a “tear” but may be some attrition which will eventually lead to a tear. Supra is an enthesis failing tendon and so I am always questioning a “tear” if there is a normal enthesis as I think this is rare except for critical zone and MTJ failures.
The patellar tendon cannot really be compared to the supra at the patella end as the patella is a sesamoid so it is not really an enthesis that can be compared. Each tendon has its own personality and way of failing commonly. The supra fails at the enthesis where as the peroneus brevis almost never does, nor does tib post so you need to understand their personalities and weaknesses (like humans!)
The AC joint lump is a classic AC joint ganglion arising from degeneration of the AC joint. They are worse if the arise on the undersurface as they impact on the subacromial space.
Lovely work,
Steve