Chapters Transcript Glenohumeral Instability with Bone loss: Diagnosis and Surgical Treatment Course: NYU Langone Orthopedics Webinar: Glenohumeral Instability: Evidence-Based Practices and Treatment Strategies The next uh talk is on instability with bone loss, diagnosis and surgical treatment. Now, uh, as pointed out by other speakers, you know, a shoulder has an excellent mobility and flexibility, but it comes at the expense of instability. Shoulder is a joint with a maximum range of motion compared to any other joint in the body, but it is also the most unstable joint. Now, uh, Doctor De Bernard has pointed out why a glenormal joint, even though called a ball and socket joint, is different than a true ball and socket hip joint. Now, shoulder is non-constrained. It's a round ball on a flat socket. So-called an articular surface mismatch. The circumference of humor head is much more than that of the glenoid, and these two factors provide not just rotation on the humal head, but also result in increased translation, which adds to instability. Three key players in shoulder instability ligament, labrum, rotator cuff, and glenoid and humal head bone stock, which is what I'm going to focus on for this talk. Now, when we evaluate a patient with glenohumal instability, whether it's a first-time dislocator or uh a recurrent instability, we wanna know what is the risk of recurrence of instability in these patients. Is surgery necessary to minimize the risk of recurrence? And what kind of surgery will give us the least risk of recurrence um in that particular patient? Now, bone loss and shoulder instability comes in all shapes and sizes, unipolar, affecting either the hummo head or the glenoid, or bipolar combined as shown in these 3D reconstruction images of multiple patients. Now when we evaluate a patient with recurrent instability in the setting of bone loss, there are certain characteristics in history and physical examination that will point out to this particular phenomenon. Patients with bone loss tend to have a higher frequency of instability events. They have a relatively greater degree of apprehension, which results in instability at low angles of abduction. They will complain that their shoulders is coming out with simple tasks like pulling a bed sheet over them. And they will also complain of instability during sleep. When we look at the mechanism. You know, instability with bone loss, especially on the glenoid side, can present with a mid-range instability. If you look at this figure in the bottom panel on the left, it shows you a humeral head on a patient who has 20 to 30% of the glenoid missing. This patient is going to dislocate at 2030, 40 degrees of abduction even without external rotation. With simple tasks like, you know, uh, reaching out for something, trying to put the shirt on, and the very common activities of daily living. With bone loss, you can also have an end range instability, especially if the bone loss is largely restricted to the hill sac side in which the hill sac is very medially placed, in which cases the engagement of hill sac with the anterior glenoid rim is what is going to cause instability and can be present, can present in higher degrees of abduction and external rotation compared to mid-range instability. As pointed out by Doctor De Bernardis, you know, imaging plays an important role in deter determining what is critical or significant bone loss. Plain radiographs can give you an idea that this patient may have bone loss based on the lack of radio density at the, below the equator on the anterior glenoid. Loss of anterior glenoid rim on a Bernejo view, if you are getting that, it's not mandatory. But finally, 3D CT scan is the gold standard for estimating glenn bone loss, both on the, uh sorry, estimating bone loss both on the glennard side and on the you know head side. Now, on the Glennard side, the critical bone loss numbers continue to be debatable. Everyone agrees more than 20 to 25% isolated is critical, but many others believe that lesser degree of bone loss in association with other factors can become critical as well. There's less consensus on the human head side. When we start talking about bipolar bone loss, then, you know, things change a little bit. And uh in order to improve our understanding, the concept of glenohumeral contact and glenoid track was introduced. We know that only a part of the humeral head circumference articulates with the glenoid at a given time. And that track on the humeral head is called a glenno track, which is basically a contact zone between the humeral head and glenoid in abduction as shown in the pictures down at the bottom of this slide. Now it is dynamic. That means it moves from the inferior medial to a superior lateral location as shown in the last diagram on this slide, and it moves approximately with abduction and external rotation. Now, Glenn track helps us to understand the interplay between the Hillsacks lesion and Glenn bone loss. One thing to remember is that being on track is protective for Hillsack's lesion. If you look at this figure on the far left and the bottom panel, you can see this gray shaded area which is actually the Glenn Track. You can measure this from. The width of the glenoids, so glenno tract roughly corresponds to 83% of the width of the glenoid. Now if this hill sack lesion, which is the dotted line, is on this track, it is less likely to engage with routine activities of daily living and abduction and external rotation. But if this Hill sacks lesion starts moving off the glennart track, it is going to engage and dislocate. But all Hill sacks lesion will eventually engage irrespective of their size and location. If the original injury mechanism and the provocative shoulder position is created because the Hill sack lesion was created as a part of instability. Now, risk of engagement increases with the anterior glenoid bone loss because the glenoid tract will become narrow, as shown in this figure. Similarly, if the Hillsacks lesion is bigger or more medially placed as shown in the bottom right, it is likely to become an engaging lesion in routine ranges of motion. Any kind of laxity, whether it comes from a capsular tear like haggle or if it comes from a pre-existing laxity, can increase the risk of engagement. Now, critical bone loss is a strong independent risk factor for recurrence, not only prior to an arthroscopic surgery, but even after arthroscopic arthroscopic bankcard repair, which is why a bone block procedure came into vote. The mechanism is to increase the glenno arc. By increasing the glenno arc, we are actually improving the glenoid tract by increasing the width of it and decreasing the risk of engagement. Now, bone block procedure can be the latterge procedure, or you could use an autograph like iliac crest or an allograft like fresh osteochondral allograft. Now, Laterge procedure is probably one of the more popular or commonly performed uh bone block procedure, which basically involves transfer of the coracoid onto the anterior glenoid neck. And it works, it's known to work with uh what we call it as a triple blocking effect. It has a bony effect in which basically you're increasing the glenoid arc, a sling effect, which is actually an interplay between the conjoined tendon and the lower half of the subscapularis through which an anterior inferior buttress is created. And lastly, the ligament or the bumper effect, which is basically the CA ligament reinforcing, uh, the anterior capsule. This, this is a surgical technique. I'm gonna try to go through it, uh, relatively quickly. Uh, so, uh, this is an open, uh, larage procedure. We do it through a deltopectoral approach. Uh, the goal is to expose the conjoint tendon and the coracoid. Uh, here you can see the CA ligament and the, the conjoint tendon being released. A stump of the CA ligament has been taken, and now the dissection is gonna be performed medially in order to do a coracoid osteotomy. I typically take around 2 centimeters of the coracoid. And uh once the osteotomy is done, uh, preparation of the Cora cord graft is performed, uh, and two drill holes are made into the coracoid graft. Once the preparation of the core cord graft is done, uh, we move on to uh preparing the glenoid for uh receiving the graft. I do a subscapularis split in which the core cord is then transferred through the split and fixed with two screws. Uh, in the essence of time, I'm gonna skip this forward. I do want to touch upon the indications, uh, of, uh, larage or any bone block procedure for me. If there is an isolated glenoid bone loss, more than 20 to 25%, that patient is getting larage. If there's an off-track lesion with a lower glenoid bone loss, even up to 12, 13%, that patient is getting a Laroche. And in selected cases, that patient may get an arthroscopic bank cord with remless sarge like the case I showed you before. Revision surgery, if there's a failed prior bankcor repair, he's most likely getting a larige in my hands. Relative contraindications of voluntary dislocation or multidirectional instability. Uh, bone block procedures are less forgiving than arthroscopic surgeries, largely because of neurovascular injury and hardware complications. There is a risk of arthritis, especially if the graft is proud. But it has bone block procedures have an effective long-term track record. Less than 5% instability, uh, is shown in multiple studies. And overall, a bone block procedure, including a lager procedure, is an excellent operation for treating shoulder instability in the setting of bone loss. It has a very low recurrence rate with excellent outcomes, but remember, it is less forgiving compared to an arthroscopic bankcor repair with respect to complications. And critical value of bone loss, bipolar bone loss, and interplay of other factors like shoulder laxity as an indication for latterge are areas of ongoing debate. Published May 19, 2025 Created by
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