SHOULDER IMPINGEMENT: MISNOMER OR MISMANAGEMENT?
MAKING THE CASE FOR ROTATOR CUFF DISEASE
One of our favorite things to say in the physical therapy world is “it depends”. Partly because it’s now a running joke but mostly because it’s absolutely true. No two patients are the same and the biopsychosocial differences mean you shouldn’t treat the same diagnosis in the same manner. But what happens when “it depends” turns into “maybe we’ve been misdiagnosing people for the past 50 years”?
Neer first detailed shoulder impingement in 1972 when he described it in detail as a “painful condition in which the soft tissues of the subacromial space are chronically entrapped and compressed between the humeral head and the subacromial arch” and we’ve more or less stuck with that for 50 years. However recent evidence has shown that this thinking may not be correct and we should re-examine how we evaluate and treat shoulder pain. So let’s take a look at what the evidence says and what that means for how we currently address shoulder pain.
A quick disclaimer: we are specifically looking at subacromial impingement syndrome, this will not be an analysis on internal impingement as that is a different pathology, presentation, and treatment.
the subacromial space
Let’s first look at the subacromial space itself: it’s defined by the humeral head inferiorly, the anterior edge and under surface of the anterior third of the acromion, the coracoacromial ligament, and the acromioclavicular joint superiorly. The height of the space between the acromion and the humeral head ranges from 1.0 to 1.5 centimeters according to measurements taken from radiographs according to this 2012 study on subacromial impingement. For impingement syndrome to be an accurate term, that means that this space would need to be reduced. However, a 2020 systematic review and meta-analysis found that there was no consistent pattern in the correlation between acromiohumeral head distance and pain or disability in those diagnosed with subacromial impingement.
Similarly, a 2021 study found that individuals with subacromial impingement syndrome actually had a larger acromiohumeral head distances. They also found there was greater thickening of the supraspinatus tendon compared to controls suggesting that the symptoms associated with subacromial impingement syndrome were related to the tendon itself rather than the subacromial space. So let’s take a look at the tendon next.
Rotator Cuff tendinopathy
Now we’re starting to get better at moving away from the term tendinitis and towards the term tendinopathy for rotator cuff disorders seeing as there is little evidence of the presence of inflammation. Rather, the histological findings of RTC pathology is more typical of a “failed healing response”. There’s disorganization of collagen fibers, a relatively haphazard proliferation of tenocytes, intracellular abnormalities within these tenocytes, and an increase in non-collagenous matrix. Which is just a lot of words to say that the tendon presents more like it’s aging rather than it undergoing a mechanical breakdown from being impinged. This lines up with the evidence of hypovascularity in the supraspinatus tendon that is consistent with age and evidence that these histological findings increase with age from 5-10% in patients under 20 to 60-65% in patients over 80.
So why do we perform so many subacromial decompression and acromioplasty procedures?
Now proper blog writing etiquette would tell me to keep this light and conversational but there’s just too much evidence to do that so let’s get right to it:
A 2020 meta-analysis found with high certainty that there is no evidence of additional benefit from subacromial decompression surgery over placebo surgery
They also found that subacromial decompression surgery provided no benefit compared to exercise therapy
A 2019 systematic review reported with high-certainty evidence that subacromial decompression does not provide clinically significant benefits over placebo in pain, function, or health-related quality of life
Beard et al randomly assigned patients with subacromial impingement syndrome to decompression surgery, arthroscopy only, and no treatment and found surgical decompression appeared to offer no extra benefit to arthroscopy only
The findings that surgical groups had better outcomes for shoulder pain and function compared to no treatment was not clinically important and the authors hypothesized that this could easily be attributed to the placebo effect of post-op physical therapy.
A 2018 meta-analysis noted that there was no difference in shoulder function or pain scores for patients undergoing rotator cuff repair with and without acromioplasty
A study by Kartus et al determined that arthroscopic acromioplasty and rotator cuff debridement in patients with partial tears did not protect the rotator cuff from undergoing further degeneration, indicating that pathology is more likely due to the aging process than the subacromial space
The evidence isn’t great, maybe we’re performing these procedures more than we actually need to. If this isn’t enough evidence I suggest reading “The Role of Acromioplasty for Management of Rotator Cuff Problems: Where is the Evidence?” as they can summarize much more information better than I ever could.
Is it impingement?
So the consensus? Subacromial decompression and acromioplasty doesn’t appear to do shit because the rotator cuff pathology is due to the aging of tissues and not due to the size of the subacromial space. So that’s a check for shoulder impingement being a misnomer. What about it being mismanaged?
mismanagement of shoulder pain
It’s not exactly fair to say that we’ve been mismanaging treatment because for years the understanding has been that the soft tissue structures have been impinged so therefore we must reduce impingement. But if we re-evaluate the pathology, then we must re-evaluate our approach. A lot of our approach has been aimed at increasing the subacromial space through postural changes, manual treatment, improving scapulohumeral rhythm, and strengthening of the posterior cuff. Unfortunately it’s quite simple: if the pain is not due to an impingement in the subacromial space, then treatment aimed at increasing this space is not addressing the issue. Focusing on minimizing kyphosis, reducing scapular protraction, and improving scapular upward rotation and posterior tilt with overhead motion in an attempt to reduce impingement in the subacromial space isn’t necessarily doing what we think it’s doing.
But my patients with shoulder impingement get better?
That’s the beauty of physical therapy: maybe it’s not as complex as we make it seem. We can come up with fancy new techniques thinking we’re increasing a space that’s not actually reduced or try the latest modality promising to make a huge difference or make some argument about how effective we are at making the shoulder blade move the way we want it to. But most injuries follow the same healing pattern: reduce the load to the irritated tissue, optimize movement, gradually re-introduce the load through progressive overloading to improve strength and tolerance, and provide time for the body to heal. And arguably, most importantly, we make the patient more confident in their ability.
The case for “Rotator Cuff Disease”
So we return to the idea of reframing shoulder impingement to rotator cuff disease. It’s reported that 44-65% of all shoulder pain is diagnosed as shoulder impingement. Obviously we want to shift towards what the research says, we are a profession rooted in evidence and we need to stay up to date on the latest evidence so for that reason alone we must consider the shift to rotator cuff disease. However, another reason to consider is the education of our patients. Fear plays a strong role in pain and a sensation of debility or fragility will only increase pain and the risk of injury. Educating patients on the risk of “pinching your tendon” through certain movements may feed into this dysfunction. Reframing our patient education to discuss the normal aging process of tendons and the importance of movement and strength to maintain a healthy lifestyle might do more for their long term outcomes than focused treatment on increasing the subacromial space.
About The author: Erin Lynch
Follow Erin:
Instagram: @airun.kehlee.suhlevin
Email: elynch@therehabcode.com
Erin became a physical therapist in 2017 and quickly realized her skills were better suited behind a computer screen. So she taught herself graphic design and now she combines her medical knowledge with her creative skills to produce content for Rehab Code. She’s the face behind the curtain and not very active on social media so you won’t find much rehab related content on her instagram. But if you want to see countless posts about her golden retriever, Dave, she’s your girl.
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