Unstable Shoulder Current Concepts

#1: Unstable shoulder explained.
#2: Our goal is to give an up to date definition an understanding of what is unstable shoulder and hopefully provide some anatomic correlates to contributors of shoulder instability. We will also review diagnostic keys we utilized in preparing for effective surgical repair. And of course will review many different aspects of successful treatment for unstable shoulder which in the current state of the art allows treatment of both soft tissue and bony injury.
#3: This skeleton video is an excellent reminder of the complex global coordinated movements required to maintain shoulder stability and to perform activities like throwing a baseball for example. 

Unstable Shoulder from ShoulderPain

Click here to watch a video about Shoulder Girdle Throwing Motion.

#4: The shoulder is the loosest joint in the body because we have a flat bony socket that provides minimal inherent stability so all of the soft tissues including the labrum and capsule ligaments muscles and neuromuscular control of these have to provide support.
#5: Once we understand this and the fact that the entire shoulder girdle is essentially only connected to the rest of the skeleton at the sternum or breastbone and clavicle, we realize that a delicate coordinated balance of all these tissues is required to keep the shoulder stable. Injury or overuse or compensation that disrupts this balance results in the bodies inability to maintain a stable center of rotation meaning an unstable shoulder.
#6: The circle concept of the shoulder was described by Dr. Russell Warren in the 1970s and in essence outlines that injury to one side of the circle results in obligate injury to the opposite side of the circle. I also like to think of the shoulder as multiple concentric circles like layers of an onion, and if the deepest layer cannot perform its function adequately then the next outer layer comes at increasing risk. An excellent example of this is that patients with chronic unstable shoulders can eventually develop rotator cuff tears.
#7: So the very 1st or deepest layer is the bumper cushion or labrum which converts to a flat bony socket into a socket that more closely matches the curvature of the humeral head.
#8: There’s a lot of variability in ways to define clinical instability even among shoulder surgeons. Given that historically all treatment was performed with open surgery many classic definitions are based on a single direction such as anterior, posterior, multidirectional, etc. With increasing skill and knowledge utilizing arthroscopic treatment and a better understanding and validation of the circle concept the more state of the art definition of shoulder instability is the inability of the body to maintain a stable center of rotation that cannot be effectively compensated any longer.
#9: To help highlight this I want to focus on the classic descriptions of posterior instability which the textbooks tend to feel is responsible for a very small percentage of all instability. However when we look at this computed tomography scan showing arthritis with asymmetric wear of the posterior glenoid we are reminded that the largest radiographic finding in arthritic shoulders is asymmetric posterior wear which probably means that many patients have had an occult posterior shoulder instability with or without pain contributing to the development of shoulder arthritis.
#10: One of the reasons posterior instability and perhaps instability in general can be difficult to diagnose is that pain is often the only complaint. Patients with a lot of underlying laxity can also have primary neurologic complaints rather than a sensation that the shoulder is unstable.
#11: Although no single physical exam test is 100 percent accurate for reliable we do find the combination of multiple tests and the overall evaluation of the patient is the most critical factor in making the diagnosis. I still feel that the history and detailed physical examination provide me with 99 percent of the clinical decision making an diagnosis and more advanced testing like an MRI with arthrogram, EMG/NCV, etc. are confirmatory and supportive rather than the primary diagnostic tools.
#12: I believe it’s important to learn to read your own diagnostic shoulder imaging tests such as CT scans and MRIs. Here to examples of a posterior labrum tear with a loose body and an inferior labrum tear with a fleck of bone attached sometimes called the bony Bankart.
#13: Here are 2 more imaging studies with reports that were read as normal but we can clearly see the 1st scan shows posterior subluxation with blunting of the posterior labrum and the 2nd scan shows posterior labrum tear without significant displacement and posterior subluxation.
#14: One of the other under appreciated contributors to shoulder instability is nerve pathology. We see a rich network of nerves that leave the cervical spine and crossed the shoulder on their way to supplying other areas of the upper extremity and any sort of injury including repetitive traction or torque can result in both pain in that nerve distribution and also weakness to the musculature supplied by those nerves. As the shoulder is a circle it easy to imagine if one set of muscles is weakened by nerve pathology and the ability to maintain a stable center of rotation can be compromised.
#15: Along with the axillary nerve we also notice a significant involvement of the suprascapular nerve with shoulder pathology including unstable shoulders and SLAP lesions. Here we see to potential areas of compression or restriction for the suprascapular nerve along its course. The MRI here shows a large para-labral cyst often seen with hidden or occult posterior superior quadrant labrum tears that also involves suprascapular nerve pathology.
#16: Here we see a bony roof or bony notch which results in increased risk for compression of the nerve and on the RIGHT we see a typical ligament that being cut decompressing the nerve. We published arthroscopic decompression of a bony suprascapular foramen in the Arthroscopy Journal in 2009. The typical patient in that study had had 3 or 4 previously failed shoulder operations which reminds us that it’s important to get the RIGHT diagnosis before proceeding with an operation.
#17: One of the great advantages of arthroscopic repair is that it allows us the opportunity of global evaluation and treatment and is inherently flexible to create a customized repair/solution for each unique patient. Because with increasing understanding we realize that pathology can exist anywhere around the circle you want her surgeon to feel comfortable being able to handle anything anywhere for each case.
#18: These I consider as never events and would encourage patients to avoid including intra-articular pain pump placement as there are much better and safer ways to address surgical pain control without the risk of destroying the joint cartilage. We also recommend seeking out a surgeon that places and ties sutures rather than using many of the available knotless devices because they are inherently less flexible and in a prospective randomized study demonstrated a 5 fold increased rate of failure when the only variable changed between the 2 groups was a standard tying implant versus a knotless implant. We also recommend running as fast as possible away from surgeons utilizing thermal shrinkage or the use of electrical energy to help shrink tissue for instability as this not only has high failure rates and potential catastrophic complications but there are much better ways of treating unstable shoulders.
#19: Many patients and surgeons also falsely believe that a spur in the shoulder is gradually destroying their rotator cuff. This is dated knowledge from the 1970s prior to the advantage of MRIs and advanced arthroscopic techniques. While an acromioplasty is a relatively simple procedure to perform, current thinking is consistent with the body creating ossification or turning the CA ligament to bone in response to something that creates abnormal movement of the humeral head so we don’t addressed the reason for the abnormal movement such as rotator cuff tearing or a pinched nerve, simply performing an acromioplasty will not be beneficial for the patient.
#20: Here we see a drawing outlining that the spur is actually not out in space but represents bone formation in the coracoacromial ligament which typically is not visible on an x-ray and is vitally important in completing the circle in the anterior superior portion of the shoulder so we recommend not resecting this ligament
#21: Another point to keep in mind is that the subscapularis which is often considered the hidden portion of the rotator cuff can also be responsible for unstable shoulder and in our experience a subscapularis tear is present in approximately 1/3 of rotator cuff repairs performed. Because most orthopedic surgeons rarely performs subscapularis repairs, especially arthroscopically, we know these lesions are frequently missed
#22: So moving into the repair side we also note that it’s important to restore balance to the entire cervical and not just perform a labrum repair. Speaking of labrum repair this drawing from an excellent article outlines the importance of restoring the labrum so that he can do its work as a bumper cushion/speed bump. This article also highlighted the fact that success requires multiple points of fixation and shoulder surgeries for unstable shoulder using just one or 2 anchors have high failure rates
#23: This slide shows a global labrum tear and about a 3rd of the repairs we do for unstable shoulder involve global tears. I want to reiterate that state of the art repair require sutures and tying knots and we recommend patients avoid thermal shrinkage and knotless anchors.
#24: Now as we look at treatment of different types of pathology at different places around the circle we start in the superior quadrant and tears of the labrum in this region are typically called SLAP lesions standing for superior labrum anterior posterior. It may be helpful to know that a segment of the biceps that inserts here has very poor blood supply and recent articles demonstrate that repairing the SLAP lesion by itself without addressing the potential problem with the biceps resulted in failure in greater than a 3rd of patients. This is one of the reasons why we prefer to combine a SLAP lesion repair with biceps tenodesis shown in the upper RIGHT slide because this removes the potential for the biceps pulling the labrum off again and also avoid the issue of scarring and further tearing of the biceps portion that does not get great blood supply.
#25: Another variant in the superior quadrant and especially within the superior quadrant the anterior superior area has a lot of variability and it’s important to understand that there can be a normal foramen or opening that should not be repaired. Patients with a Buford complex have an unusual finding of a very thick ligament that appeared a lot like the biceps and our preferred method of treating this is to combine DT tenodesis with conversion of this ligament to a bumper cushion/labrum anteriorly. This restores stability to the joint and also maintains full range of motion.
#26: Bone loss can also be an issue and cause for an unstable shoulder. An easy way to think about this is to imagine about all sitting on a Tee and if a portion of the Tee is broken off it becomes that much harder to maintain the ball’s stability. We therefore recommend restoring bone loss and in the acute setting as shown here on this slide we repair the bone back anatomically. Modern arthroscopic techniques also allow us to graft bone loss when present utilizing either the patient’s own bone or allograft.
#27: Here we see the large bony fragment seen in the previous slide reduced and repaired anatomically
#28: As we mentioned earlier successful treatment means restoring balance to the entire circle and evaluating the entire joint
#29: This can sometimes mean having a combination of factors including a stretched out and thin capsule combined with a bumper cushion that could not down and healed medially as shown in the right-hand picture.
#30: So successful treatment means being able to get anywhere and everywhere within the shoulder and restoring global balance to the capsule, ligament, and recreating the bumper cushion as shown here all the way around
#31: We will talk about recurrent injury a bit more later but we also have to keep in mind that because were going to have multiple points of fixation we want to use a method of fixation that does not result in its own complications in the future. We utilized suture anchors that are made of purely suture and to not drill large holes in the glenoid so that if there is a recurrent injury all of the options available for the 1st time are still available to us making a revision procedure much easier.
#32: Aside from just stretching of the capsule and ligaments we can also have tearing as shown in these 2 slides where the aerobic demonstrates leakage of the white fluid through the tear
#33: These tears are called HAG L lesions standing for humeral avulsion glenohumeral ligament and we see an arthroscopic picture where we are repairing this with needle and thread
#34: Here is the completed repair and please make note of the fact that this patient had both the ligament tear and labrum tear so we can just stop 1 we find one thing wrong and we have to make sure and address the entire spectrum of pathology.
#35: Bone loss on the humeral side is sometimes called a Hill-Sachs lesion and the rotator cuff and capsule can be stripped resulting in a partial tear here. These images demonstrate that a part of the circle has been depressed and with the RIGHT position we can see that this would result in increased risk of unstable shoulder.
#36: One elegant technique for a dressing both the partial tear and rotating this bone defect out of the joint space to reduce instability is shown here arthroscopically. This series of pictures demonstrates freshening up the bone defect and then percutaneously placing anchors through the rotator cuff into the bone and then tying these on the outside of the rotator cuff to remove the defect from engaging. Recent studies looking at outcomes of this procedure called a Remplissage have been excellent as has our own experience over many years.
#37: This slide demonstrates a video of a large Hill-Sachs lesion being treated with the Remplissage procedure
#38: Here are 2 images of an MRI performed at 2 years following surgery demonstrating excellent healing of the rotator cuff into the lesion with it being rotated out of the joint and we can see the ball is sitting nicely centered on the glenoid
#39: Here is a short video of the patient with posterior instability that outlines the importance of restoring balance and not just focusing on a focal area of labrum repair. Notice the extent of bumper re creation from the anterior inferior quadrant all the way up to the posterior superior quadrant including restoring native tension in the capsule and ligament as well as the bumper cushion/containment. 

Click here to watch a video about Unstable Shoulder Repair.

#40: Keep in mind that multiple points of fixation also bring into the spotlight the methods of fixation. We already recommended avoiding knotless anchors and as there are much better implants available today I would recommend avoiding metal anchors in the glenoid to minimize bone loss, and the potential for 3rd body wear/chondrolysis if the implant is proud or becomes proud
#41: Here our x-rays of the patient treated with a single knotless metal anchor that brings up another problem with metal devices
#42: That problem is metal artifact. Unfortunately, this patient had instability and multiple directions and as we already previously discussed a 1 anchor repair has no hope of success and as this was a metal anchor it creates enough artifact that an MRI can be difficult to read. Here however we can clearly see that the patient has extensive labrum tearing and subluxation of the humeral head posteriorly consistent with persistently unstable shoulder
#43: Absorbable anchors can also present a problem in that they don’t always uniformly resorb and may result in cavitary defects such as shown here
#44: So we mention earlier that our preferred implants in the glenoid are made of suture only and we have studied these with MRIs performed at 2 years following repair showing excellent healing of the tracts and maintenance of bone volume. Notice how the ball is nicely centered on the tee.
#45: Here are some other patients with different views again demonstrating the multiple anchors were able to place next to each other without creating a problem.
#46: So our hope in this presentation has been to present the circle concept of instability and, way with a better understanding that an unstable shoulder represents a spectrum of pathology and successful treatment requires the ability to be able to address each and every one of these. We recommend getting a shoulder 2nd opinion if the recommendation after evaluation has been to perform an acromioplasty as the primary procedure, your given impingement as the primary diagnosis, a biceps tenodesis only has been recommended, the surgeon utilizes knotless anchors for labrum repair, if you are having persistent shoulder problems and previously had a repair would just 1 or 2 anchors, and prior to undertaking repeat shoulder surgery always consider an independent 2nd opinion from a shoulder surgeon in a different practice.

Author
Vivek Agrawal, MD

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