So this is the final part in my series on the unstable shoulder looking at the last sub group on the Stanmore Classification, the Type III's, the adverse muscle patterning shoulders. For a catch up on the other parts click here for Type I's the traumatic unstable shoulders, here for Type II's the non traumatic unstable shoulders and here for a general introduction into unstable shoulders.
Now the first thing to say about true Type III shoulders where there is absolutely NO structural reason for the instability and it's solely due to adverse muscle patterning alone is that they are rare… very rare, and if we are being honest little is truly known about them, both in the research and in clinical practice as to what causes them and what's the best way to identify, manage and treat them. Most of these types of shoulder tend to be managed and treated in dedicated multidisciplinary shoulder rehab centres, meaning that most of us won't get to see them!
However, just as with the Type II non traumatic unstable shoulders, where there was a blurring of the boundaries with the traumatic Type I's, so the same is true here with Type IIIs becoming mixed up with Type II unstable shoulders as in some cases these can display adverse muscle patterning so are classed as Type II/III shoulders. This means there is a structural issue but there is also adverse muscle patterning, these are seen more often in regular clinical practice, and these are the one's you may come into contact with.
What is adverse muscle patterning and why does it cause unstable shoulders.
Well simply put, it's what it says it is, it's where it's thought the muscles around the shoulder contract in an adverse way as to pull the humeral head off the centre of the Glenoid during movement, the two main culprits are thought to be the Pecotralis Major muscle pulling anteriorly and the Latissimus Dorsi muscle pulling posteriorly (and perhaps anteriorly as well, read on for more info on this!).
We know that strong muscle contractions are sufficient enough to dislocate a shoulder as this is often seen in those who dislocate their shoulders when suffering fits or seizures, the power of the muscle contractions are strong enough to overwhelm the passive restraints and so dislocate the shoulder joint, usually posteriorly. Now some adverse muscle patterners can truly dislocate their shoulders but most will only produce enough force to sublux or produce sensations of instability in the shoulder, it is this action that is then thought to lead to sensations of pain and discomfort, possibly directly related to the adverse muscle action causing pain, or via repetitive micro trauma.
Another important issue to mention here now I think, is what do we mean by the term 'adverse' muscle patterning. For example, I have seen many, many shoulders that could be classed as moving 'adversely' when compared to the general population, but to the shoulders owner it feels perfectly normal and they are blissfully happy with no pain or issues, so is this adverse, no of course it isn't, instead 'adverse' has to apply both to the observer and more importantly to the shoulders owner, i.e. it is causing them pains or functional limitations. So please do not start classifying shoulders as adverse movers just because YOU think they move weirdly.
This is a lovely video example of this exact situation here it's of a so called adverse or dysfunctional shoulder moving seen under a CT scanner, it's clear that the shoulder joint is doing some funky wobbly stuff, and it doesn't when she is asked to actively contracted or tense her shoulder muscles. Ok, so that's a clear example of an adverse shoulder muscle patterner right, well no it isn't, as when you read the case this lady had NO shoulder pain or dysfunctions, this is just how she moves, so do we try to correct it or let it be… tricky hey!
Diagnosing an adverse muscle patterning shoulder
So with that in mind who are the adverse or dysfunctional muscle patterners is there any commonality, well in my experience there is, they tend to be young females with age ranges from between 20-30 with usually some other structural issue affecting the shoulder as well such as hypermobility or a capacious shoulder capsule so classed as Type II/III's, they also tend to display signs of multidirectional instability rather than just either/or one direction, just to complicate matters further.
These patients can also be, rather harshly, labelled as “mad, bad and sad” ie having underlying psychosocial issues which are thought to drive the adverse neuromusclar patterning, but, in my experience and opinion, this isn't the case for most. True there is normally an element of psychological factors that I see in these patients such as fear, depression and anxiety, but in my opinion this is usually as a consequence of the instability rather than a driving factor behind it, but these issues must be recognised and managed.
Identifying adverse muscle patterning is, in my opinion, really easy as it's normally bleeding obvious just watching them move that something adverse is occurring.
But do we have any other methods apart from observation to diagnose adverse muscle patterning, as we all know observation isn't a reliable method. Well there has been some research on the use of EMG in an attempt to diagnose adverse muscle action in unstable shoulders, but due to the limitations of surface EMGs with cross talk and the challenges of interpreting what's 'over active' from 'normal' means that this method isn't, in my opinion, any more reliable, in fact I think it can lead us down completely the wrong paths, as confirmed by this paper again using EMG to find which muscles are 'over active' in either anterior or posterior instability, and all they got was a confusing mess with Latissimus Dorsi being found to be 'over active' in both anterior and posterior instability?
However, I actually don't think it matters what muscles are so called 'over' or 'under' active, instead what is important is what's driving the altered patterning during the movement and how can we improve it? To put it simpler, we shouldn't be looking to treat the muscles, instead we should be looking to improve the movement.
There are, in my experience, some common styles or types of 'adverse' patterns of movement I see that I feel either contribute to or are as a result of pain and dysfunction, and they fit into three broad sub groups or categories, now these are my own very unscientific categories, I hasten to add, based on my experience alone, so take them with a ouch of salt, they are what I call the stop-starters, jerkers, or splinters.
Stop-starters are what I call those who I see that have a pattern of movement that is just that… stopping and starting, it's not smooth or fluid, something mechanical, neurological, psychological or all three, halts their movement before allowing it to continue again, it can occur in any direction or range, but it's usually in forward or sideways elevations
Jerkers again are just that, I see them jerk their way through the movement, different from stop staters in that the jerking happens through out the range of movement.
Splinters are where I see a screwed up scapulo-humeral rhythm with earlier scapular movement and hitching or elevation of the shoulder girdle, they can feel and appear stiff and restricted but actually have no loss of movement.
Treating an adverse muscle patterning shoulder
Yet again there is little to no evidence as to what to do with these patients as personified by this latest systematic review here looking at interventions in shoulders with multidirectional instability, with the only recommendation being that exercise or movement therapy is needed. There are a few case studies, but these add little, so my approach with these patients is, as with most things, keep it simple.
I think a major point in managing these patients is not just the exercises or movements but the other underlying pyschosocial factors, best investigated through an open and frank discussion with the patient on what their thoughts, feelings and fears are with their shoulder. Together try and explore where the adverse muscle patterning maybe coming from, is it fear, is it protection, is it something else.
For example, I had one patient eventually tell me she thought her arm would fall off if she moved it differently after she suffered a couple of dislocations in a short time period, and one other patient who said her shoulder pain only really started after her ex partner told her she moved her arm weirdly, so in an effort to please him she told me tried moving differently! These omissions took a while to dig out from the patients but once aired the relief was clear to see and improvements made, so my first bit of advise is to spend a little longer talking to these patients and get to know them better, make them feel relaxed and able to share this information with you.
This information then I feel, helps build a frame work for where the patients movement patterns maybe coming from, and from here we can start with treatment, and this maybe nothing more than simple advice, reassurance and education to help dispel any myths or misconceptions they may have, then it can lead into planning exercises as well as other ways and methods to help improve movement.
Those ways and methods are highly unscientific, individual and only found out through trial and error, as there is no research to say otherwise.
Generally, and I mean really, really generally, I find that for 'stop starters' distraction techniques work well, not joint distractions but mental distractions i.e. getting them doing something else with their other arm hand to occupy their thoughts as they also do movements with the affected side! For 'jerkers' I find generally closed kinetic chain movements seem to reduce the 'jerking' effects, and finally the for the 'splinters' these being the toughest to treat I haven't found one method better than another…
For example the lady who thought her arm was going to fall off was a splinter, solid tense and appeared stiff as a board when she tried to move her arm, gaurding and scared, she had all sorts of weird pains and sensations including into her neck and back as a result of this splinting. So I thought we should start with some simple closed chain movements on her hands and knees, stuff that I thought would help her feel more secure and comfortable in moving her shoulder and help her relax her neck and back muscles, but in fact she hated this, it gave her more pain? So we the tried some pendulum hangs and swings with very small movements, which I thought would be horrid for her, but it did the opposite and gave her some sensations of relief, so we progressed this to her holding light weights whilst doing the pendulums, and then moved into different positions eg standing, hanging over edge or bed etc, we reinforced this with her doing active assisted and fully active low load high repetition movements immediately afterwards. A few weeks of doing this her pains had reduced significantly and movement improved! Just one case but the point is there is no fixed method when working with these shoulders.
Another treatment option for dealing with these shoulders I have come across is an orthopaedic approach of using Botox injections to temporarily paralyse an 'over active' muscle for a few months, again there have been a few case studies in the literature and I have come across one or two patients who have tried this, but they didn't help, in fact in one case it actually made the situation a whole lot worse, and thankfully I haven't heard or seen it used for the last year.
So in summary true Type III unstable shoulders with no structural reason for instability just pure adverse muscle patterning are very, very rare and you will unlikely ever see one. However Type II/III unstable shoulders where there is a structural cause triggering 'adverse' muscle patterning are more common. Remember that adverse muscle patterning is highly subjective and it can be a chicken or egg scenario in as much if it's a cause or effect, defense or defect. Management of these shoulders is individual and on a trial and error basis until, if ever, we have more evidence of a best approach.
As always thanks for your time reading my stuff
Until next time