Shoulder and Elbow cases posterior labrum tear
A 25-year-old, right-hand-dominant man presents to the clinic with right shoulder pain. He is a professional football player and plays as an offensive lineman. Three days ago, he was blocking with his hands with his right elbow fully extended and his shoulder flexed, adducted, and internally rotated. He felt a pop and sharp pain in his right shoulder when making contact with the defender. He was diagnosed with a posterior shoulder dislocation in the ER, which was relocated and he was sent home. He presents as a follow-up in clinic having persistent shoulder pain and the sensation that his shoulder is going to dislocate posteriorly. He is otherwise healthy and takes no medications. On examination of the right shoulder, he has normal passive and active range of motion, but tenderness to palpation over the posterior joint line. He has pain with posterior stress test, and the rest of the examination is normal. X-rays show a small bone fragment next to the posterior glenoid rim with a normal humeral head contour.
What is the most likely diagnosis?
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Posterior labrum tear
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SLAP tear
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Anterior shoulder dislocation
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Rotator cuff tear
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Supraglenoid notch ganglion cyst
Discussion
The correct answer is (A). Posterior shoulder dislocations classically occur when the patient’s shoulder is the recipient of trauma while it is flexed, adducted, and internally rotated (as in this case). When the shoulder dislocates posteriorly or when the shoulder relocates, the humeral head can tear the posterior labrum and sometimes avulse off part of the posterior glenoid with the labrum (reverse Bankart lesion), which is present in this case as shown by the small bone fragment on the xray. The glenoid can also collapse part of the anterior humeral head articular surface, resulting in a reverse Hill–Sachs lesion, which is not present in this case as shown by the normal humeral head contour on the x-ray. This can lead to posterior instability due to the lack of a functional posterior labrum, which normally helps to deepen the joint and act as a mechanical block, preventing the humeral head from displacing posteriorly. Patients also experience shoulder pain over the posterior joint line, where the tear is located.
SLAP tears (Answer B) occur usually due to compression or traction injuries, not posterior dislocations, and result in pain and mechanical symptoms (popping, clicking, and catching) of the shoulder. They normally do not result in posterior instability or pain over the posterior joint line.
Anterior shoulder dislocations (Answer C) usually occur with the shoulder flexed, abducted, and externally rotated. They can result in or be caused by anterior instability, and one may find a Bankart (chip fracture of the anterior glenoid) or Hill–Sachs (compression of posterior articular surface of the humeral head) lesion on radiographs. Reverse Bankart and reverse Hill–Sachs lesions are called “reverse” because they are similar lesions that occur on the opposite side of the glenoid and humeral head, respectively.
Rotator cuff tears (Answer D) are usually a result of chronic degeneration, occur insidiously, happen in older patients, and classically present with night pain and pain with overhead motion. This does not fit with the picture presented in the current case.
Supraglenoid notch ganglion cysts (Answer E) cause compression of the
suprascapular nerve as it passes around the lateral border of the scapular spine by the spinoglenoid notch. Posterior labral tears can sometimes result in formation of a cyst in the spinoglenoid notch, which can compress the suprascapular nerve. At this point, innervation to the supraspinatus has already occurred, so compression at the spinoglenoid notch would result in infraspinatus dysfunction with normal supraspinatus function. This patient has normal motion with no evidence of neuropathy or infraspinatus pathology. He likely has a posterior labral tear with a reverse Bankart and not a compressive spinoglenoid notch cyst.
Which of the following physical examination maneuvers is not used to diagnose a posterior labrum tear?
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Posterior stress test
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Jerk test
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Posterior load and shift test
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Kim test
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Apprehension test
Discussion
The correct answer is (E). The apprehension test is used to diagnose anterior instability. It is performed by having the patient lie supine and the examiner passively abduct and externally rotate the patient’s shoulder. If the patient feels as if the shoulder is going to dislocate anteriorly, the test is positive.
Physical examination maneuvers to test for a posterior labral tear overlap with those for posterior instability because the former can be one of the causes of the latter. The posterior stress test is performed by: lying the patient supine, flexing the shoulder and elbow to 90 degrees, internally rotating the shoulder then putting a posteriorly directed force on the flexed elbow down the shaft of the humerus with one hand, and palpating any posterior subluxation or dislocation of the humerus out of the glenoid with the other hand against the posterior shoulder (see Fig. 2–24). The test is positive if any subluxation or dislocation is palpated.
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Figure 2–24 Posterior stress test. (From Millett PJ, Clavert P, Hatch GFR, Warner JJP. Recurrent posterior shoulder instability. J Am Acad Orthop Surg. 2006;14(8):464–476.)
The jerk test (Answer B) is performed with the patient in a sitting position. The examiner flexes the shoulder to 90 degrees, fully internally rotates the shoulder, and flexes the elbow to 90 degrees. The examiner then pushes on the flexed elbow in a posterior direction down the shaft of the humerus (see Fig. 2–25). A positive test is when the shoulder subluxes or dislocates posteriorly. If the shoulder dislocates, the shoulder is then extended, and the humeral head will relocate with a jerking motion, hence the name of the test.
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Figure 2–25 Jerk test. (From Millett PJ, Clavert P, Hatch GFR, Warner JJP. Recurrent posterior shoulder instability. J Am Acad Orthop Surg. 2006;14(8):464–476.)
The posterior load and shift test (Answer C) is performed with the patient seated and the arm at the side. The examiner holds with one hand the patient’s humerus by gripping anteriorly and posteriorly just below the greater tuberosity. The examiner pushes the humeral head into the glenoid while attempting to displace the humerus posteriorly (see Fig. 2–26). The test is positive if there is a greater than 50% displacement of the humeral head out of the glenoid.
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Figure 2–26 Load and shift test. (From Millett PJ, Clavert P, Hatch GFR, Warner JJP. Recurrent posterior shoulder instability. J Am Acad Orthop Surg. 2006;14(8):464–476.)
What is the diagnostic study of choice for a posterior labrum tear?
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CT scan
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Arthroscopy
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MRI
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MR arthrogram
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X-ray
Discussion
The correct answer is (D). MRI (Answer C) is exceptional at imaging soft tissue structures, including the labrum (see Fig. 2–27). Adding contrast dye into the glenohumeral joint with an MR arthrogram increases the sensitivity, specificity, and accuracy for diagnosis of a labral tear even further, making this the test of choice. In a patient with a posterior dislocation without an associated fracture of the humerus, obtaining an MRI/MR arthrogram is essential. Injury to the posterior labrum occurs in 58% of these cases. If a patient has an irreducible, posterior shoulder dislocation, it is usually due to soft tissue interposition, and MRI/MR arthrogram can identify what structure is blocking the relocation.
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Figure 2–27 Axial T1 MR arthrogram of right shoulder showing posterior Bankart lesion. (From Rouleau DM, Hebert-Davies J, Robinson CM. Acute traumatic posterior shoulder dislocation. J Am Acad Orthop Surg. 2014;22(3):145–152.)
A CT scan (Answer A) is very useful for preoperative planning in case of fractures associated with dislocations or if there is a reverse Hill–Sachs lesion. This would not be as good as MRI for imaging soft tissues.
Arthroscopy (Answer B) would be more invasive than MR arthrogram, carrying with it surgical risks. MR arthrogram is an excellent modality for diagnosing posterior labrum tear, and is the gold standard. However, if MR arthrogram fails to make a diagnosis and a posterior labral tear is still highly suspected, performing an arthroscopy should be considered for diagnostic and therapeutic purposes.
X-rays (Answer E) were already obtained in this case and would not be helpful in diagnosing a posterior labral tear.
If surgery is required, what is the preferred treatment for an isolated, posterior labrum tear?
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Arthroscopic labrum repair
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Open repair
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Physical therapy, NSAIDs, and glenohumeral joint corticosteroid injections
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Arthroscopic capsular shift
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Open reconstruction
Discussion
The correct answer is (A). Of patients with posterior shoulder instability, those with reverse Bankart lesions are ideal candidates for arthroscopic repair. Arthroscopic repair is relatively contraindicated in those who have had prior arthroscopic repairs that failed, avulsion of the glenohumeral ligaments off of the humerus, and those with symptomatic multidirectional instability in patients with connective tissue disease such as Ehlers–Danlos. This is not contraindicated, however, if a patient with a connective tissue disease is symptomatic only posteriorly. In patients with posterior instability who have malformed glenoid bone, either eroded or retroverted, arthroscopic repair is absolutely contraindicated because a bone-altering surgery is required.
One can perform the arthroscopy with three or four portals, putting one or two posteriorly and two anteriorly, making sure the posterior portal is lateral enough to access the posterior glenoid rim. An anterosuperior portal is used for the camera and a mid-anterior portal is used for instruments and suture passing. Both anterior portals are placed in the rotator interval. To repair the reverse Bankart, suture anchors are passed through the mid-anterior portal and used to reattach the labrum.
Open repair (Answer B) can be used to repair many causes of posterior shoulder instability including posterior capsular shifts or bony repairs but is not the preferred method to repair a posterior labral injury. Conservative treatment (Answer C) should not be tried if surgical treatment is required, as the question stem stated. However, a trial conservative treatment should be tried in patients with posterior instability because of its low morbidity and high efficacy. Studies have shown that nonsurgical treatment is effective for 65% to 80% of cases of posterior instability.
Arthroscopic shifts (Answer D) can be used to tighten the posterior capsule if that is the etiology of posterior instability. However, in this case, the patient has instability due to a posterior labrum tear, so tightening the posterior capsule would not be as effective as repairing the labrum tear.
Reconstructive surgeries (Answer E) are not normally required to treat cases of posterior instability associated with posterior labrum tears because the labrum can normally be repaired. They can be used if there is a focal defect in the glenoid bone, though.
Objectives: Did you learn...?
Diagnose a posterior labrum tear based on history and physical examination? Surgically treat a posterior labrum tear?