SLAP Lesions and AC Sprains

Today Austin takes us through types of SLAP lesions and AC sprains with a special focus on relevant anatomy, classifications, and testing.

Transcript

Copy Transcript Copied

Hello to all of our calm and confident listeners who will soon be taking the OCS exam. We’re down to the wire and you are keeping it cool. Okay, maybe you are a little anxious, but hopefully our podcasts and resources have helped curb that anxiety into a healthy anticipation. You’ve got this!  

Today’s quick episode will continue our series on the shoulder and cover a couple miscellaneous diagnoses that have not fit well in other podcasts, with discussion on SLAP tears, long head of biceps tendon issues, and AC joint injuries. 

Here’s a little pre-test: do you know which types of SLAP tear involve the long head of biceps tendon? Do you know what structures would be involved in a Rockwood grade II AC joint sprain? If so, great, if not, hang out a few minutes and we’ll get that taken care of. 

The name SLAP tear, S-L-A-P, stands for superior labrum anterior to posterior. SLAP tears occur somewhere between 10 and 2 o’clock on the glenoid, though the can occur as continuations of other types of labral tears. SLAP tears can involve the attachment of the long head of the biceps tendonDue to its attachment at the superior glenoid and the superior labrum,. The mechanism of injury typically involves trauma or repetitive overhead activity, such as throwing and overhead hitting and is thus very common in baseball pitchers. Subjective history of a shoulder with a SLAP tear that is symptomatic would typically involve vague deep shoulder pain, “dead arm” feeling especially after overhead activity, feeling of posterior shoulder tightness, mechanical symptoms like catching/locking/popping, and pain exacerbated by overhead activity. Go figure, sounds like a lot of people with shoulder pain. There are 4 main types of SLAP tear: Types 1 and 3 involve the labrum only, while 2 and 4 involve the superior labrum and biceps tendon attachment. Remember this by the fact that 2 and 4 are multiples of 2, and have 2 structures involved. Type one is isolated fraying of the superior labrum, without detachment of the labrum and without biceps involvement. Type two includes detachment of the superior labrum and biceps tendon attachment together from the superior glenoid, and looks as if the biceps tendon pulled the superior labrum from the glenoid. Types three and four are both bucket handle types with the labral tissue detached and flapped down, but type 3 will be isolated superior labrum, while type 4 will have the superior labrum and long head of biceps tendon detached together and flapped down into the glenoid. So, Type 1–fraying of superior labrum; type 2–detachment or stripping of the superior labrum and biceps tendon together; Type three–isolated bucket handle tear of the superior labrum; and type 4–bucket handle tear of both the biceps tendon and superior labrum together. Now that I’ve given the classic information about SLAP tears, you should know that it is often what my colleague David would call a “garbage diagnosis,” especially in middle-aged individuals. SLAP tears are kind of like the degenerative rotator cuff tear and the bulging intervertebral disc of the labrum–MRI studies have shown that SLAP tears are present in as many as 55-72% of asymptomsatic shoulders among individuals 45-60  years old. As such, rehabilitation is the first-line treatment of choice, and surgery is reserved for failure of conservative rehabilitation. Now when I say surgery, that does not necessarily mean repair. Surgical options include debridement of the torn labral tissue, biceps tenodesis, or now in less common cases, repair of the superior labrum and biceps tendon anchor if involved. Partly due to learning of the prevalence of asymptomatic SLAP tears and the development of easier, less rehab-intensive procedures such as the biceps tenodesis, the number of SLAP repairs done have decreased significantly. SLAP repair will typically be reserved for younger, higher level overhead athletes, while the general population, especially older individuals, will typically be managed with debridement of the superior labrum and biceps tenodesis where the long head of biceps tendon is clipped and anchored to the humerus outside of the glenohumeral joint. You should also note that these are very commonly performed along with other surgical repairs such as a rotator cuff repair. 

Clinical diagnosis of SLAP tears is difficult, as our special tests are not very good and the diagnosis is debated as being the cause of pain in the first place. The most studied special tests for SLAP tear include the Obrien’s test (also known as active compression test), Speed’s test, Anterior slide test, and crank test. The Obrien (or active compression) test is the most sensitivity at 67%, but has terrible specificity at 37%. The O’Brien test is performed in two steps. First the shoulder is brought to 90 degrees of flexion and adducted 15 degrees and internally rotated, theoretically to put greater stress on superior labral structures. The patient is asked to resist downward force in the position. Reproduction of deep pain in the shoulder is considered positive for a SLAP lesion, while superficial pain over the AC joint is considered positive for AC joint pathology. Part two of the test is to take the shoulder out of internal rotation and repeat with palm up, which is supposedly supposed to now be less painful. If it sounds like that would be positive with just about any painful shoulder, you’re right, which is probably why the specificity is so bad. Speeds, anterior slide, and crank which each have terrible sensitivity, but decent specificity with Speeds at 78%, anterior slide at 86%, and the crank test at 75%. The Speeds test is basically a shoulder flexion manual muscle test, but with the palm up to make the biceps work and put greater stress on the long head of the biceps tendon. You can see how it could also reproduce pain with biceps tendinopathy. The anterior slide test is performed by having the patient put their hand on their iliac crest with shoulder extended and elbow bent. The examiner puts a superoanterior force through the humerus via the elbow.  A painful click or clunk in the front of the shoulder is considered a positive test. Finally the crank test is performed with the patient supine with the shoulder fully elevated and elbow bent. The examiner puts axial force through the humerus via the elbow while internally and externally rotating the shoulder. Pain with or without a clunk would be considered a positive test. Obviously with the poor diagnostic accuracy of any of these tests, you are only going to use them with a history and presentation that leads you to suspect a SLAP lesion. It would be great if we had a specific cluster that was more accurate, but we do not yet have consensus on a specific cluster that you can rely on. From this I would remember that the obrien test is the more sensitive test for SLAP (though it is still trash), while speeds, anterior slide, and crank are the more specific tests. Thus you could kinda maybe consider ruling out SLAP lesion with a negative obrien’s (combined with a history that does not match SLAP tear), and you could potentially rule IN a SLAP tear with some combination of Speeds, anterior slide, and/or the crank test (again, combined with a history that matches a slap tear.

Now, before we leave the SLAP discussion, you should know many of the test used to investigate SLAP lesions have also been used and studied to investigate long head of biceps tendinopathy. Biceps tendinopathy is yet another one of our less trusted diagnoses, and I won’t spend near as much time on it. The long head of biceps tendon has been blamed for a lot of anterior shoulder pain that it probably isn’t responsible for, but you should at least be familiar with it. A few different issues can occur with the LHB tendon, such as tendinitis or tendinosis, partial or full thickness tear, or tear of the transverse humeral ligament, which could cause instability of the biceps tendon where it is able to sublux in and out of the bicipital groove. Long head of biceps tendinopathy is often considered with a report of anterior shoulder pain in a line along the bicipital groove potentially extending down into the biceps. Pain should be worse with shoulder motions that also involve biceps contraction, and there may be isolated tenderness along the bicipital groove. But, don’t trust that considering you are also palpating through the anterior deltoid to get there, and have you seen just how many things attach along the bicipital groove? Go figure, pain with bicipital palpation is not a reliable test for biceps tendinopathy, or a SLAP lesion for that matter. There are a myriad of tests said to test for this including the aforementioned slap tests and other tests such as yergason’s, biceps load 1 and 2, upper cut etc, blah blah blah and suffice it to say, they are trash. Know they exist so that you don’t get thrown off by seeing them mentioned in a question or answer, but I wouldn’t spend my time knowing all the properties of those tests. 

AC joint separation

The other diagnosis we will cover today is acromioclavicular joint sprain, or what is commonly called a separated shoulder. First, the anatomy. The AC joint is a plane type synovial joint and thus lacks any bony stability in itself. There are two, well, three really, main ligaments of the AC joint. The acromioclavicular ligament, which envelopes the joint provides some stability and is the first to be injured in an AC joint sprain. However the primary stability of the joint comes from extrinsic ligaments. The coracoclavicular ligament, extending from the coracoid process to the inferior surface of the distal clavicle, is actually two distinct ligaments: the trapezoid and the conoid ligament. Beyond these ligaments, deltoid and trapezius muscles also provide some stability to the joint via their attachment to the acromion and the clavicle. The most common mechanism of injury for an AC joint separation is a fall on the tip of the shoulder, such as with a fall off a bicycle or rugby tackle, as with both mechanisms you often are not able to reach out and brace your fall due to holding handlebars or a ball. So while you may avoid a FOOSH injury by not reaching out when falling, you could still get a fall-not-on-outstreatched-hand or FNOOSH injury. The most accepted classification system for AC joint sprain is the Rockwood classification which we will discuss next. Each type, 1-6, will be classified by which ligaments are involved, and the extent and location of clavicle displacement.

A Type I sprain involves a sprain of the acromioclavicular ligament only without involvement of the other ligaments. There would be no elevation of the clavicle in relation to the acromion, and thus there would be no radiographic evidence of injury. Short of an MRI, diagnosis would thus be made based on mechanism of injury, tenderness to palpation of the AC joint, and positive provocation testing such as the Obrien’s active compression test, which actually has very high specificity for AC joint pain but low sensitivity, or the cross body adduction test, where the arm is passively taken into full horizontal adduction with overpressure, which should reproduce pain in the AC joint.  

A Type II sprain will have elevation of the distal clavicle in relation to the acromion on radiographs, but not above the superior border of the acromion. The AC ligament and joint capsule will be ruptured, and the coracoclavcular ligaments will be sprained but not ruptured. To the trained eye there could thus be a mild step-off deformity between the distal clavicle and acromion compared to the uninvolved side. 

Type III sprains of course have rupture of the AC ligament, and will have full rupture of the the coracoclavicular ligaments as well. It will have significant elevation of the clavicle above the superior border of the acromion, but to be type III must be less than twice normal distance from the clavicle to coracoid process. Type III would have an obvious step-off deformity.  

Types IV through VI are really just more severe variations on a type III injury as they will also have full rupture of all ligaments, but will have different clavicle locations. Type IV will involve posterior displacement of the clavicle into the trapezius muscle. Type V is most similar to Type III with significant elevation of the clavicle, but will have greater than twice the patient’s normal coracoclavicular distance. Type VI  is rare and will have inferior displacement of the clavicle into the subcoracoid or subacromial space and will commonly involve neural injury.

In case the test were to get picky on imaging knowledge, the required radiographs for diagnosis and classification of AC joint injuries traditional bilateral AP views, lateral axillary view, and what is called a “Zanca” view, which is an AP view that is angulated upward or cephalad 10-15 degrees to eliminate overlap between the clavicle and scapular and thus allows better visualization of the AC joint. 

 How do we manage AC joint injuries? The general consensus is that non-surgical therapy is the primary treatment for grade I and II injuries, and there is significant debate and conflict over whether or not surgery is indicated for grade III injuries. However, outcomes are about the same in those treated primarily with rehabilitation vs surgery, and there is no risk associated with delaying surgery with grade II injuries, so the general trend has been away from surgery for grade III injuries and the real indications are persistent pain and limited function even with conservative management and, of course, cosmetic concerns. Apparently some people don’t like the bump on the shoulder. Surgery is much more likely to be indicated for types IV-VI due to the clavicle disrupting other structures and presenting mechanical issues with functional movement.  

Before we finish I should mention fractures. The main differential diagnoses with a mechanism of injury that would cause an AC joint injury is a distal clavicle fracture or  and avulsion fracture of the of the coracoid process, both of which can present very similar to an AC joint separation, Thus if you do have a case that is suspicious for an AC joint sprain, especially with a step off deformity, radiographs are going to be indicated. 

Question: 

The patient is a 32 year old male referred to outpatient orthopedics 3 weeks following a fall off of a bicycle with a diagnosis of right acromioclavicular joint sprain. The radiographs included in the referral demonstrate the right clavicle elevated in relation to the acromion compared to the left side, but not above the superior border of the acromion. Clinical exam reveals the following: right shoulder flexion active range of motion limited to 130 degrees by pain at the AC joint, weak and painful right shoulder flexion manual muscle testing, tenderness to palpation of the right AC joint, and a slight step off deformity on the right compared to the left. Of the following, which is the most likely level of injury to each structure?

 A. Acromioclavicular ligament sprained; conoid ligament ruptured; and trapezoid ligament ruptured
B. Acromioclavicular ligament ruptured; conoid ligament sprained; and trapezoid ligament sprained
C. Acromioclavicular ligament sprained; conoid ligament spared; trapezoid ligament spared 
D. Acromioclavicular ligament ruptured; conoid ligament spared; trapezoid ligament ruptured.  

This question is a good example of how information in this podcast could be used to test you in the areas of human anatomy and physiology, which is 10% of the exam, or pathology and pathophysiology, which is also 10% of the exam. Without knowing the details of the case you should actually be able to eliminate options A and D. A because you should know that the in the progression of AC joint sprains, the acromioclavicular ligament will be injured first, and if the ligaments of the coracoclavicular ligament are ruptured, the AC ligament would have to be ruptured as well. D can be eliminated as you should know that the conoid and trapezoid ligaments are the two distinct bands of the coracoclavicular ligament and would most likely both be injured together if one is involved. Options B and C are then left, which requires you to know that the case describes a type II AC joint sprain, and that would involve rupture of the AC ligament, and sprain of the coracoclavicular ligament. The fact that the answers only mention the components of the coracoclavicular ligament rather than just saying the coracoclavicular ligament is, well, being a little bit mean.