So our first speaker is going to be Dr. Alexander Zank. He's a board-certified physician in physical medicine and rehabilitation and sports medicine and carries a designation of registered in musculoskeletal ultrasound. For the past five years, he's been serving our nation's veterans at the Minneapolis VA Medical Center and is a mentor to medical trainees through his service as a leading medical educator at the University of Minnesota. So please join me in welcoming Dr. Zank. Thank you. Okay, so it looks like my slides are up. Please let me know if there's any technical difficulties. I'm really excited to join you this morning though to kind of talk about the shoulder. I will do an anatomy review and then delve into some of the physiology with it. I have no financial disclosures to share. I will not be discussing any off-label use under unapproved use of devices or commercial products, but I do have to mention that the topics discussed today are my personal interpretations and do not necessarily reflect that of Uncle Sam. So our objectives for today are really to re-familiarize ourselves with the shoulder anatomy. As you guys have gone through medical school and done your training in PM&R, you guys are more than adept at knowing the shoulder, but it's always good to have a quick refresher. We'll also be talking a little bit about the approach to our shoulder examination. Really, we want to make sure that we're avoiding any potential pitfalls and that we know how to kind of adapt according to our clientele. And then last but not least, we really want to kind of take a closer look at how this exam in the shoulder's overall range of motion and function is going to play into the daily lives of our patients. And in particular, we're going to be looking at our wheelchair population. So I feel like as an MSK specialist and physiatrist, those seem to go hand in hand and people always expect us to know everything about our wheelchair using population. So first off, our shoulder, this is our ball and socket joint that everyone thinks about and then its design actually allows us to have the most degrees of range of motion of any of our joints. And these graphics here demonstrate how we have shoulder flexion, shoulder extension, abduction, internal, external rotation, and then also our cross abduction and then kind of backwards motion there. Collectively, this is all able to happen by the system of over 17 different muscles attaching to our scapula and the remainder of our thorax. When we think about testing our range of motion, we can do it in a variety of different ways. We can estimate it just by, you know, a good ball's eye or eyeball perspective, or we could use a goniometer to try to be more precise. But if you really want to get the most precise range of motion assessment, that'd be in a motion analysis lab, but that's available to you in your clinics. Another one that I like to use, especially in clinic, is actually using points of reference on the person. So if I have them doing internal rotation as demonstrated in the middle bottom third picture, you can kind of correlate it where you think their vertebral level is or where they are touching or able to reach in their scapula. With those 17 muscles attaching to the scapula, we're able to do quite a few different motions with this as well. So we're able to elevate our scapula, we're able to depress it, we're able to abduct it or kind of bring it back towards its contralateral part, and we're able to protract as if we're kind of squeezing our shoulders and anteriorly together. And then we also have rotation. And so depending on people's different pathology that they may be presenting with, you may see medial wing, you may see lateral wing, you may see alterations in the rotation. We may see differences in how these shoulder blades move in concert, which would be more concerning for something like scapular dyskinesia, which I feel is probably understated in our general population. So together, as these are moving, we have something called our scapular humeral rhythm. We expect there to be about a two to one ratio in favor of the humeral motion. That's going to be started with your first zero to 30 degrees of shoulder flexion or abduction. And then from 30 to 90 degrees, excuse me, you're going to have more motion through the scapula and then the remainder 90 to 180 degrees, you're going to see about a two to one difference with the glenohumeral movement more than the scapula. And what this does is it really enhances our shoulder stability as we get above that 90 degrees of shoulder abduction. This all works great until it doesn't. And so there's a lot of different reasons why a person may have alterations in their movement patterns or their kinetic chain of their shoulder. Some are more common than others, but what we know for certain is that in general, shoulder pain is very common. So of all of us attending here, about a quarter of us have had a shoulder issue in the past year, at least that's what the stats say. And then all of us collectively have about a two thirds chance of having some kind of shoulder pathology. The leading diagnosis for most of these conditions is going to be what I just try to do a bucket label of RCD, whether it's disease, disorder, dysfunction, and that can include your tendinosis, that could include your partial thickness tears or your other injuries to the rotator cuff. And this is what's going to be your most common resenting shoulder complaint. So now that we have kind of talked a little bit about why we're talking about this today, let's dive into the anatomy. So here's our bony anatomy. On the far left, we have our anterior, middle, superior, and then far right is our posterior. The shoulder is actually comprised of four joints. And the way that I remember that is the four rotator cuff muscles. So we have our glenohumeral joint, which is highlighted by the yellow stars. We have our acromioclavicular joint highlighted by the blue star. We have our sternoclavicular highlighted by the red star. And then the one that's most commonly forgotten is our scapular thoracic joint. And this is more of a junction, however, it still falls within that joint category for anatomy purposes. So this is an area where people might have some clicking, bumping, if there's any kind of alteration between the scapula and the thorax. There is a bursa there that can get quite inflamed and be problematic for people. Looking at the ligaments. So the shoulder is a very complex joint spanned by many different ligaments across it. And when we're thinking about the scapula, it goes all the way from the anterior perspective, from the corporeal process, all the way posterior to the body. And there you are going to have stability from it, from directly connecting to the humeral head, as well as the clavicle through ligamentous bodies. So this is why if a person has acromioclavicular arthropathy and they are undergoing a disoclavical excision with their surgical colleagues, why they still have a lot of stability as it becomes a kind of more of a suspension bridge format there. When we're looking at the different ligamentous structures, we also need to keep in mind our capsule, as a lot of times we see people coming into us with issues like frozen shoulder adhesive capsulitis. If you see acute injuries, this could be compromised or the anterior band of the inferior glenohumeral ligament could be compromised after an anterior shoulder dislocation. When we're thinking about those 17 muscles that attach, we'll run through to the scapula, we'll run through those real quick. So we have our deltoid here, this is going to be innervated by our axillary nerve. We have our supraspinous innervated by our suprascapular nerve. Our infraspinatus also innervated by the suprascapular nerve. Going down to the teres minor, innervated by the axillary nerve. Our teres major innervated by the lower subscapular nerve primarily, also a little bit of a component of the thoracodorsal nerve as well. Then we have our trapezius muscles innervated by the accessory nerve. Then we have our rhomboid major innervated by the dorsal scapular nerve. Our rhomboid minor also innervated by the dorsal scapular nerve. We have our levator scapula or the dark levator as my former chair used to always call it, also innervated by the dorsal scapular nerve. And then the one that people, one of the ones that people kind of forget is the long head of the triceps brachii. That's going to be innervated by a radial nerve. Looking a little bit more interiorly here, we have our biceps brachii innervated by the musculocutaneous nerve. Our latissimus dorsi, this is innervated by our thoracodorsal nerve. And then here's another one that is commonly forgotten, our omohyoid. So this is innervated by the inferior root of the anterior cervicalis. And then the ones that we couldn't see from that picture, we have our subscapularis running along the anterior body of the scapula. And this is innervated by the upper and lower subscapular nerves. Also anteriorly, we have our corcobrachialis innervated by the musculocutaneous nerve and then the pectoralis minor innervated by the medial pectoral nerve and the anterior pectoralis, which is a communicating branch from the lateral pectoral nerve. And then our serratus anterior nerve innervated by the long thoracic, which historically we think about for some of that scapular wound. For the stability of our shoulder, this is achieved by a couple of different methods. One, our static stabilizers, those include more of our structural components. So our labrum, when we think about our humeral head resting on the glenoid, it is truly kind of like the ice cream cone or that golf ball on the tee. And so the surface contact only accounts for about 30% of that humeral head. And so in order to increase that stability, our labrum is able to increase the diameter or points of contact with the humeral head by up to 75% in the superior-inferior diameter and AP diameter about 50%. And this aids in our proprioception. We talked about the capsule in the anterior bands, specifically the anterior inferior glenohumeral ligament, but also your posterior bands are supportive as well to prevent posterior dislocation. Dynamically, we have our rotator cuff, our sits muscles. If a person has a compromised supraspinatus tendon or a complete tear there, we can sometimes get inferences from it by just looking at the X-ray, as you'll see that cranial-humeral interval be obliterated or be decreased. And so collectively, our rotator cuff actually counteracts the deltoid, which is drawing it up. We'll spend a little bit more time on the rotator cuff since it is such a common etiology. So our supraspinatus, or what I call our primary abductor, it also does extra rotation. And this originates on the medial border of the scapula along the supraspinatus fossa. It's gonna go over and insert laterally along the superfacet of the greater tuberosity. And again, it's innervated by the suprascapular nerve. We see its nerve root level is C5 to C6, primarily C5. And this is, again, one of our main rotator cuff muscles that we use for a lot of our daily functions of life. The most common area that's injured is that anterior distal third. And so if you're evaluating a person, make sure that you're palpating kind of directly adjacent to the bicipolar groove area. Or if you're using ultrasound for evaluation, make sure you're scanning at least to that area. In the infraspinatus muscle, this too originates from the scapula along its medial border, but along infraspinatus fossa. It's gonna go over and travel laterally and it attaches to the middle facet of the greater tuberosity. There is a little bit of overlay of where the infraspinatus kind of crosses over with the supraspinatus. And then it's also innervated by the suprascapular nerve and it's too as primarily a C5 distribution. Functionally, it is our primary external rotator. And one thing I should mention real quick is that the functions that I'm listing are really gonna be your primary movements or actions when a person is kind of in a neutral position. Depending on the person's body position or body habits perhaps, their different muscle activations could perform different activities. That's why if you see someone who comes into clinic, they have an MRI already or an ultrasound examination that demonstrates that they have a complete supraspinatus tear, but they still have intact abduction or shoulder flexion. And it's because they've been able to learn to compensate. And a part of that is their body position. So since those are both inner, the last two muscles are both innervated by suprascapular nerve, we'll take a second to talk more about that. So that's gonna be coming from our C5 to C6 nerve root level. It comes from the superior trunk of the brachial plexus and it does innervate the supraspinatus and infraspinatus. It courses superiorly down and it goes across the suprascapular notch around the base of the supraspinatus fossa and down through the spinal glenodge to innervate that infraspinatus. One of the key functions of it too is that it provides sensation to our acromioclavicular and glenohumeral joints. And that's why we're able to provide people good pain relief with suprascapular nerve blocks, even if they have failed our intra-articular injections, which are gonna be a little bit more specific. Looking at the other rotator cuff muscles, our teres minor, this too originates from the scapula, kind of just subjacent to the infraspinatus and is about, usually about half the size of your infraspinatus. And it runs over and attaches to the infraspinatus facet of the greater tuberosity and it's innervated by our axillary nerve. And it too has the same nerve root level distribution of C5, C6. It is a primary external rotator. Its counterpart, the teres major, which is not considered part of the rotator cuff, that is actually more of an internal rotator as it goes anteriorly and attaches to the intra-tubercular sulcus of the humerus. Excuse me. So our fourth rotator cuff muscle, the subscapularis, and this is more along the anterior portion of the scapula. It runs laterally and attaches to a lesser tuberosity on the anterior aspect of the shoulder, just adjacent to the bicipital groove. And it forms part of that rotator cuff interval that we're talking about with ultrasound, where you have the subscapularis blending over the longhead biceps tendon into the supraspinatus tendon. And so that's kind of the area that you need to really look at to make sure that the longhead biceps tendon is intact and within a bicipital groove, as well as if there is any potential rotator cuff pathology at that insertion of the supraspinatus. This is primarily innervated at the C6 level, and it is our primary interval rotator of the shoulder. A few items that I also want to kind of talk about because of their interesting pathology and correlations. We've talked about the shoulder stability with our ligaments and our dynamic components. Our axillary nerve is actually our most likely nerve to be injured if a person does have the anterior shoulder dislocation while they're in sport or other activity. It originates from the C5, C6 level of the superior trunk of the brachial plexus. And sorry, that is a typo. It does not innervate the supraspinatus or infraspinatus. It innervates the deltoid and teres minor. So please don't pay attention to the slide at that point. It also provides sensation to the lateral shoulder overlying the deltoid region. If you remember from anatomy class, we have our quadrilateral space where the axillary nerve comes out. So it runs with your brachial plexus anteriorly, and then it dives down between and pierces through the quadrilateral space, which you can now see from the posterior aspect on the right. And as it comes through here, we define the boundaries of the quadrilateral space as the humerus laterally, the long head of the triceps medially. We have the superior aspect of the teres minor, and then we have the teres major being kind of the floor or the most inferior portion of it. And so if someone has a dislocation or some other pathology or significant cyst formation in that region, you may have sensory impairment along that lateral shoulder that can kind of cue you in. Belonging in biceps brachii. So it originates and I'm saying it originates from the superior labrum because that's its most cephalad portion. And then it runs distally all the way down beyond the elbow and attaches onto the radial tuberosity. This enables us to do elbow flexion as well as supination. And then it's innervated by our musculocutaneous nerve. This is a very important structure as we commonly see people come in with different labral pathology, including slap lesions. And so understanding where it attaches will help us better recognize it on imaging as well as assess it in exam. One more thing before I move on to the next structure. An interesting factoid about the longhead biceps brachii is that along its origin, where it's in its bicipital groove and extending, we have a tendon sheath in that area. But when you go down distally towards its insertion, there is not a tendon sheath. So when you're planning any potential procedures, keep that in mind. So our pectoralis minor, I like to highlight this specific muscle because it can become quite influential with how a person's arm function is or if they develop any kind of a little bit atypical or aberrant controller arm, any swelling as if it becomes too taut as it overlies the brachial plexus and our neurovascular structures there, it can contribute to both neurovascular and, or sorry, neural and vascular thoracic outlet syndrome. So our pectoralis minor originates from our third and fifth rib, kind of near our costal cartilage, and then it's going to extend cephaloid and lateral to the coracoid process. It is innervated primarily by our medial pectoral nerve, but it does have that communicating branch from the lateral pectoral nerve known as anza pectoralis. It is primarily from our C8 T1 nerve root level, but if you have that communicating branch, you also get from C5, C6, C7. So if you are planning EMG study, that can complicate your interpretation of your results if there's any abnormalities. It helps us to perform several scapular movements, depression, protraction, as well as downward rotation, which would be the medial border, sorry, inferior angle, kind of rotating a little bit cephaloid. So it looks like it's rotating down. For our physical exam, now that we kind of better have a mind construct of our anatomy again. This slide is intentionally busy. In fact, if you were only to look at special testing for the labrum, you can more than fill up this slide. The point I'm trying to make is that we have many options available to us when we're considering or evaluating a person with shoulder pain. So we have to be very diligent with our approach and try to be as systematic as possible. Unfortunately, none of our physical exam maneuvers are infallible. And usually when a person comes out with a new physical exam maneuver, and it usually has a very high sensitivity and fair specificity for the specific injury that they're investigating. But as time goes on and other researchers investigate it, we find that the results just are not consistent. Most of our physical exam maneuvers only have a sensitivity or specificity in the 70s. So how useful these examinations are, are really gonna be probably more dependent on who's performing and how they're performing it. So the important thing here is that we know the relative deficiencies with these exams so that we could better utilize them to aid our patients. And so what we see here is there's multiple studies that look at individual shoulder examinations. And again, they are not that great at finding out or delineating the underlying shoulder pathology. In fact, even when you start to put these multitude of tests together and compile them, it doesn't really help our diagnostic value at all. Because of that, I always like to kind of refer back to this study done by Hermann's in 2013, that was published in JAMA. And what they did was they took experts in the field of MSK and they tried to create an exam, a set of exam, physical exam maneuvers that would help our primary care colleagues. And so they reviewed the literature and then came up with five tests that they thought were most appropriate. And they used tests that were across that spectrum of our strength testing, our provocative tests as far as like stability, and then the combination or composite test, which if you have either weakness or instability, that'd be positive. What they discovered is you really have to take into account age and history, and I suggest also hand dominance. And when they looked at it, they were able to come down to these five tests. So they recommend doing a painful arc as that's going to give you a small increase in your likelihood of diagnosing rotator cuff disorder. You should do internal rotational lag tests. And for those who are unfamiliar with it, if you think about the traditional Gerber liftoff test, where you rest the dorsum of your hand against the small of your back, and then you lift off, what you're actually going to do in this circumstance is you are going to guide the patient through that motion and then when they kind of hit in the range of motion, you're going to ask them to try to keep their hand in that position. If they're unable to, that'd be a positive test. And that would have a moderate increased likelihood for full thickness tears. And then with our external rotational lag, similarly with how that's performed is you have your elbow against your side, elbow flexed about 90 degrees, and then you guide the person into full external rotation. And then you ask them to hold it there. If they are unable to keep their arm in that position and it swings anteriorly, that would be considered a positive test. A lot of times when people are trying these new physical exam maneuvers that they may not be familiar with, referring to the patients, they may not be fully aware of what you're asking them to do. So I try to give them at least two to three tries to see if they're able to hold it back. Because there could be a little bit of a training effect here. And then last but not least, we have our drop arm test, which has a small increase in likelihood of being able to diagnose rotator cuff disorder. For me, I think I've only maybe seen one true drop arm test in my career so far. That's because people have a very strong sense of self-preservation. So be cautious with how you assess your drop arm test. So this is also a table from that study by Hermann's. And what it shows here is we have groups of different tests and you're seeing a whole spectrum of different sensitivities and specificities ranging anywhere from the low 20s up to like near perfect with a sensitivity of 97% and a fair specificity of 83% for internal rotation lag. And then down below, you can see the resistant abduction where the sensitivity is only near 60% and specificity was very low. So due to these variances, again, really proceed with your physical exam with caution, use your knowledge of the anatomy in order to better guide yourself. Some of these differences or changes that we see with sensitivity and specificity over time as different investigators look at it really may be due differences in how the physical exam maneuvers are being performed. And so people have investigated this a little bit too. So Irk and her colleagues in 2016 wanted to look to see, well, how good is Dr. Google? And so they brought up and reviewed 39 different video tutorials that were able to be found online. 36 of the videos were found on resources such as YouTube, ViewMedi, OrthoBullets and G6MD. Of those that they were able to review, 61% were rated as fair to poor. When we look at also what they were, the different tests that they were looking at, there were common ones, ones that we should all feel very comfortable and confident with performing, whether you are an MSK specialist or if you've just gone through your traditional PM&R training. That included Hawkins-Kennedy, O'Brien's and the near impingement test. And respectively, those were inaccurate and they were only performed accurately. 50% of the time for Hawkins-Kennedy, about a third of the time for O'Brien's and only a quarter of the time for nears. When we look at other references for our Hawkins-Kennedy test, we could see that just a description of how they're describing how they perform it varies quite differently. So it can be very easy to get mixed up and that's also why it's so important to make sure that you have internal consistency with your exam as over time, you're gonna build that internal mind construct where you identify pathology and correlate it well with your physical exam, whether you're calling it empty can or jobs or whatever the test may be. So for those who are hard to call out to list, which I am not, but I thought this was a pretty picture, this is Wilton Sage. And so brace yourself for hopefully a little Sage advice. Some of the potential pitfalls that people have when they're evaluating the shoulder is really just asking for appropriate visualization. So make sure that you have the equipment that you need in your clinics in order to do that. And so that may include either gowns or kind of like a tube top version of the gown, asking people to be able to expose their shoulders so you could adequately evaluate is very helpful. Also being able to evaluate both shoulders at the same time, especially when you're looking posterior and looking for those, maybe more nuanced physical exam findings like scapular dyskinesia. We don't wanna miss a subtle finding that can really change the course of a person's care. Other things we wanna make sure to include in our physical exam on the shoulder is don't forget to include the cervical spine, looking at your active range of motion and perform your neurologic testing. This will help us rule out any concurrent or confounding pathologies like radiculopathies or cervical stenosis or referred pain from possibly the facets. Again, there's a multitude of different types of tests. These can be categorized by either strength, is there a presence of weakness when you perform the test? There's provocative tests, so either pain or instability. And then there's composite where if pain or instability are present, then it would be positive. There's significant crossover. And so you may be able to substitute one test for another depending on person's range of motion, as well as their comfort level or pain or anxiety when performing the examination maneuver. The picture here demonstrates a elite swimmer, and it's important to kind of keep in mind that everyone should really function as their own control. Some differences are what you may consider to be an abnormal range of motion. It may actually be more of a training effect that they've intentionally developed over time. Alternatively, it may be that they have a connective tissue disorder, or maybe it's both. So again, make sure that we are using our patients as their own control when possible. Some things to consider avoiding. So this is a illustration where people are trying to assess the stability of the glenohumeral joint. And on the far left, you're seeing the apprehension test. In the middle, you're seeing the Job's Relocation Test, where you're putting some posterior force along the humeral head or along the proximal humerus. And then the far right is called the Surprise Test. That's where you quickly relieve the pressure that you're applying in the Relocation Test. I would suggest avoiding the Surprise Test, just gently kind of letting off some of that pressure with the Relocation Test is more than sufficient to elicit a person's apprehension or pain by just kind of more doing like a rebound test, like we once did with our abdominal exams, that may just lead to more concern on the patient's part and dissatisfaction. Other tests that can kind of compromise a person's shoulder a bit would include the Gerber Liftoff Test. And so with this plane of motion, a lot of people are coming to in pain or who have glenohumeral osteoarthritis or rotator cuff pathology, don't have great internal rotation. And so being placed in this position, that can be painful and feel compromising for them. And so as an alternative, I recommend considering other subscapularis tests. You could do the Bear Hug as demonstrated in the top right corner. You get on the bottom left, you could do the Belly Press, or the Napoleon as it's also referred to. And I really like this because it's easy for people to get into, you just rest their hand against their abdomen, and then you ask them to internally rotate and you kind of coach them through that motion. Most often I will put my hand between their hand and their abdomen, and then I will pull towards myself, so away from their body, and I'm looking to see how they respond to it. A positive test would be either they start adducting their elbow towards their body and then pulling back in order to maintain that, rather than internally rotating to maintain that. The other positive would be they maintain the internal rotation position, but it just lifts off from their abdomen. Okay, so now after hopefully my words of wisdom for you, let's talk about a little bit about how this actually applies. So shoulder pathology, excuse me one second. Okay, so shoulder pathology. Now this is extremely prevalent in our general population as well as our wheelchair using population. You have nearly 4 million wheelchair users in the United States, and 90% of them use manual wheelchairs. Many of those also have shoulder pain. So upwards of three quarters of our wheelchair users have a form of shoulder pain. And when we look at associated factors or risk factors, that includes the number or duration of years of using a wheelchair, their age, and then their body mass index. Excuse me for a second. All right, I'm sorry for that delay. So when we look at our wheelchair users, about two thirds of them have evidence of having a rotator cuff. Most of them occur at that area that we mentioned before, the anterior distal third of the supraspinatus at its insertion. A lot of these can be categorized as either intrasubstance. Dr. Sink? Yes. I think we may have lost your screen share. Was that intentional? No. Do you mind just trying to share that one more time? We've only missed just a moment. Oh, okay. We can hear you loud and clear. I think we just lost your presentation. Okay. Yeah. Oh, there we go. But it seems like everyone's enjoying the presentation so far. Good. Yes. Not bad for the first one. Yeah. Okay. Is it back up and running for you? No. Let me try a few things on my end. Sorry. I do see your face currently. We can see it. We can see it fine. Thank you. Maybe we just lost it in the room. Okay. Thank you all. We'll regain it here in the room. But I'll work on that if you want to continue your presentation. Sorry for the delay. The Zoom is showing up. Okay. Sorry about that. Okay. So there's many reasons why our wheelchair using population could be having these shoulder pains, but it's kind of the most obvious, really overuse. And so when we consider actually how they're using their upper extremities, some people have actually kind of more defined it as the weight bearing shoulder because of how they are using it for their functional mobility. So for our manual wheelchair users, they might do up to 1800 short lasting bi-manual pushes per day to move around. When we advise our patients on how to prevent pressure injuries, we talk about our pressure reliefs performing every 15 minutes, holding that for 30 to 120 seconds each. And that really adds up over the day. And it's not insignificant. So each time they perform those weight reliefs, it is about 100, sorry, it's about 1300 Newtons that they're a force that they are putting through their glenohumeral joint. And so that's quite significant. So if you compare that to other activities like throwing a baseball or a baseball pitcher, that's kind of on par with it. And when we just talk about the wheelchair propulsion, so there's 1800 short lasting pushes, well, that can go to about 350 Newtons worth of glenohumeral joint force reactions. So it can really add up over time. If you also kind of compare the amount of force required to perform that weight relief, another comparable would be that if you were to try to push about 40 to 75 kilograms across your floor, that's the same amount of force that you would have to put in in order to perform that weight relief. When we look at how this affects our different patient populations within our wheelchair users, those glenohumeral contact forces are significantly higher in our tetraplegics than our paraplegics. And part of that is related to how they're performing and which muscle groups that they're relying upon. For our tetraplegics, they're really relying more on that anterior chain in order to perform what we would consider posterior chain-like movements. So, how can we help and help reduce this overburden related to wheelchair use? So we can be mindful of the ergonomics or wheelchair biomechanics, being mindful of the seat position, the hand contact angle, or where you're connecting to apply force through the wheel to propel yourself. The camber or the angle of the wheel can make a difference. And then our scapular resting angle as well. So when we're thinking about our seat backs, making sure that we're not interfering with their scapular motion. The PVA has actually put forth recommendations on how to reduce shoulder injuries because of how prevalent they are. And so these are their recommendations. They recommend trying to perform long, smooth push strokes. So when you do that, that increases your contact angles. Reduce your cadence when possible. When we look at our people who use manual wheelchairs, about 35% of their time within their gait cycle is actually spent pushing. And so if they're able to reduce that, they can promote more recovery and hopefully reduce the number of pushes that they do throughout the day. And then working to minimize peak hindering forces during propulsion. So that can be as simple as making sure that you have the right tire choice, making sure that you have the right tire insufflation for the terrain that you're engaging in. Other thing that we can be mindful of is how we guide our patients to propel their wheelchair. So there's a lot of different hand patterns that they can use. And if you had to choose one of these to guide them, it would be the double loop. And that's going to be more for their open, kind of open field per se motion. So if they're going down a long hallway or they're outdoors on smooth terrain, that double loop is going to give them the largest hand contact angle. It's going to enable them to have the longest recovery time or repositioning within their stroke. And again, reducing the overall number of pushes that they have throughout the day. For the arc, that's going to be their most useful for kind of getting around tiny tight spaces. And then the semicircular can also help to try to reduce some of it and just, sorry, can also help to reduce some of their propulsions throughout the day, but it's just not as effective as the double loop. Other modifications that you could consider for their wheelchair would be where you place their axle, the further anterior it is. You're going to allow them to propel a little bit easier, but you also put them at risk for tipping over backwards. You may consider modes of propulsion force production. So what I mean by that, I mean, let's gear them up just like a bicycle. So if you could improve their mechanical advantage through gears, that can reduce the amount of strain on their shoulders. And then directionality. Some wheelchairs will only go one direction, some go both directions. The reason why you might be interested in a unidirectional wheelchair is if you live in like a really hilly or undulating environment where now you're concerned about like rolling back. And then I already kind of mentioned the wheel choice as far as considerations. Materials can be important. However, different studies vary on whether or not the weight of your wheelchair makes a significant difference to the amount of force that you put through with your propulsions. That's probably going to be mostly dependent again on your train, because if you're trying to go uphill with a heavier wheelchair, you will have to put a lot more effort in. This is just an example of one of the wheelchair designs that's out there. This one was designed at the Minneapolis VA with their Adaptive Design Engineering Group. And it's really a proof of concept. And with this, you can see that they have a geared system to try to reduce that strain. They also have made the axle anterior, and it allows you to have a different contact angle when you're pressing forward. And there's only a very slight camber to the hand arm as well as the wheel. And so collectively, they were trying to, one, make this more comfortable and have less strain and require less range of motion of the shoulder and be able to propel a person forward. When we look at other alternatives, so if you have a patient who's really wanting to get involved with exercise, you can get them, you can hopefully choose alternative exercise equipment for them. And so this is a comparison to the glenohumeral contact forces between a hand cycle in a wheelchair. And when you look at the graphs, it really tells a story, great. So with a hand cycle, you're able to reduce those peak glenohumeral contact forces by over two thirds. And then your muscle selection too, so this is the bottom right corner is more of a EMG, surface EMG. You're able to kind of see where that force production is coming from. And so you're able to reduce the strain on the anterior chain, including your biceps as well as your supraspinatus musculature that you see a much higher peaks in during manual wheelchair use. And so equipping our patients with the best equipment for their purposes can be extremely helpful. Last but not least, consideration of power compulsion can be very helpful too. Covering different national veteran sports programs. This has really enabled a lot of the veterans to be able to get from one site to another and still have the energy and cardiovascular reserve and kind of reserve in their shoulder function and energy to participate in the sport. And so each has their own benefit. These are just examples. I'm not trying to necessarily push you forward in one direction or another, but the Smart Drive is nice. The Smart Drive is in the far right. It's nice because it's relatively lightweight. You can easily put it into a backpack and you just can connect it to your chair. It's something that a lot of manual wheelchair users can do independently to attach it and it will kick in automatically as a need. It can also kind of gear it up so that it can provide constant assistance for them if they're having to go up a long hill or a long passage. The Firefly, which is the top right one, that looks kind of more like a little bit of a motorcycle or bicycle attachment. That's nice because it gives the person more control as far as which direction to go. And it appears very intuitive with its use because of how many people have used such prior sports equipment. And then the bottom left corner is our power assist wheels. And so these help to potentiate the force production. You can dial in how sensitive that is. So they can go really fast, but they tend to be very expensive and they tend to be really heavy. So if you have a person who is independent with their driving and they're getting in and out of their vehicle, that may be a challenge for them depending on their setup. So each has their own purpose and it's really kind of keeping, again, the scenario of the patient in mind. So now that is really kind of the whole story. So after this, I really hope that we've been able to accomplish a few things. First, I hope that we're able to kind of refresh your shoulder knowledge, make you understand the inherent limitations that we have with our physical exam, but also use that knowledge of your shoulder in order to better direct your exam and interpret the results that you get. Let's remember to try to avoid pitfalls, ensure our proper visualization when performing the exam, make sure we don't miss our cervical spine confounding factors here, and then modify our tests when needed according to the patient's tolerance and function. And then last but not least, for our special patient populations, including our wheelchair users, really keep in mind the different demands that they have on their shoulders compared to our ambulatory population. We should really try to best promote their functional mobility and independence by protecting their shoulders. So if you have any questions or you have a difficult case, please feel free to reach out. And again, I want to thank the American Osteopathic College of Physical Medicine and Rehab for allowing me to join you today, as well as the VA and my work with the University of Minnesota. If you have any questions, here's how to contact me. And I know we're going to be doing a little Q&A session, so if there's anything you'd like to answer afterwards, this is how to do it. And here is my bibliography for the studies I did not include information on earlier. Thank you so much, Dr. Zenk. That was really excellent and very thorough presentation. We are able to take live questions, if there's any questions. Dr. Brooks has a microphone in the back, just raise your hand, we can bring that around so Dr. Zenk can hear you. Dr. Zenk, there's one question, we're just bringing the microphone up here. Good morning. I just have a question about, I may have missed it, but the innervation to the shoulder in terms of, and there's a lot of people now, you know, doing peripheral nerve stimulation and pulse RF and various modalities to address intractable shoulder pain. Do you have any comment on that? Yes. So I do not perform peripheral nerve stimulation, but I am very interested in trying to delve into that field. So I think when you're considering different peripheral nerve stimulation or addressing the nerves in order to provide shoulder relief, I think that's wonderful. I think that could be a really great opportunity for people to get the relief that they're seeking while also trying again to preserve their joints. When we think about the different injectors that we use for our joint injections, we know that anesthetics are chondrotoxic, the steroids are also detrimental to the joint. So if we can address the pain somewhere else downstream or upstream, I think that is quite advantageous to our patient population. The one downside to doing it, for instance, I do a lot of suprascapular nerve blocks with either prolotherapy or corticosteroid injections and people get great relief. And then if that's successful but not as durable, then we do refer them over for pulse radiofrequency ablation. The downside is that it's less specific. So if you're really trying to use your injections more for diagnostic value, you might want to continue to do that until you definitely have a clear definitive working diagnosis and then pursue your steroid sparing or joint sparing procedures. But yeah, I totally support that. Thanks for the question. Great. Thanks, Dr. Zink. There's another question from Zoom that says, do you find that insurance companies cover the motor assist for the wheelchairs? Oh, I am sorry. I am the absolute worst person to ask that question to. My career has primarily been at the VA, so I am afforded the luxury of not having to do the prior authorizations. I'm sorry. I wish I had a better answer for you. If I may, it's Larry Prokop. Number one, excellent lecture, very well needed, wonderful topic. Number two, if I may throw out a thought to the person who asked the question about insurance coverage. For the high level motion assist and type modifications, it's difficult if it's straight commercial insurance, if it's under accident or injury policy, much easier. Here's one thought that people often don't think of. Every state in the country, like we know, has a vocational rehabilitation program. They will often pay for these modifications if it aids the person going back to work. Those are three possibilities to take a look at for the folks that aren't under the VA. The VA is, in my mind, probably one of the best to cover good wheelchair modifications. Think about that and don't forget vocational rehab. Thank you again. Excellent talk. Thank you. Thank you for that information. I will definitely keep that in my back pocket, too. And then, Dr. Zink, one more question from Zoom. How long would you hold for the ER and IR lag tests, or do you see an immediate positive sign if there's pathology? Yeah, it's usually pretty obvious and quick. So by the time you get them into that position, they are usually unable to hold it. If they kind of have a slow, gradual swing in or drop towards their back with internal rotational lag, I would just reset and ask them really to hold it there, and if they're able to hold it there for a good second or two, I would consider that normal. And that the reason that they are swinging or dropping towards their back is probably more fatigability rather than an ability to perform it. Great. Any other questions? Great. Thank you so much, Dr. Zink. That was really excellent. Thank you so much. Thank you.

shoulder anatomy

wheelchair users

shoulder pathology

ergonomic wheelchairs

power assist devices

propulsion techniques

shoulder injuries

musculoskeletal structure

nerve stimulation