Notes
3
Glenohumeral Instability
Glenohumeral instability is defined as pathological increased translation of the humeral head from the glenoid cavity.1,2 Instability includes both subluxation (partial dislocation with spontaneous reduction) and dislocation, when the humeral head completely escapes the glenoid cavity, and special maneuvers are required to reduce the shoulder back into the socket. Additionally, instability can be classified by the direction of the translation of the humeral head: anterior, posterior, or multidirectional.2-5 Instability is described as either traumatic or atraumatic.2-5 Traumatic instability results from a forceful contact event that damages a previously structurally intact glenohumeral joint, while atraumatic instability occurs in the absence of trauma. Atraumatic instability may occur because the shoulder has already sustained extensive structural damage, or because of ligamentous laxity.
The glenohumeral joint allows significant degrees of motion in multiple directions and, therefore, is particularly susceptible to instability. Glenohumeral instability is a very common condition, as dislocations affect 1.7 percent of the global population.6 Notably, dislocations predominantly affect younger patients, and the highest rate of dislocations occurs in individuals between twenty and thirty-nine years of age.7 In addition to age, risk factors for the development of traumatic shoulder instability include male sex and participation in athletic activities or contact sports.7,8 Anterior glenohumeral instability comprises over 95 percent of shoulder instability events.9 In contrast, posterior instability makes up 2 to 5 percent of glenohumeral instability events, while the frequency of multidirectional instability is less common.10,11 Patients who suffer an anterior dislocation have a high likelihood of recurrence. Notably, younger age, male sex, hyperlaxity, and participation in contact/collision sports greatly increase the risk of recurrence after anterior dislocation.12,13
Anatomy
The glenohumeral joint is composed of static and dynamic restraints that contribute to stability.5,14 Static restraints to the glenohumeral joint include the bony anatomy of the humerus and glenoid, the joint capsule, ligamentous structures, the glenoid labrum, and the inherent negative intra-articular pressure of the glenohumeral joint. The capsuloligamentous structures include the superior, middle, and inferior glenohumeral ligaments, all of which are important static stabilizers at various ranges of motion. The superior glenohumeral ligament specifically functions as an inferior stabilizer of the shoulder in adduction. The middle glenohumeral ligament confers anterior stability in 45 to 90 degrees of abduction, while the inferior ligament protects from excessive anterior and inferior translation of the humerus in the apprehensive position of 90 degrees abduction and 90 degrees external rotation.15 Dynamic restraints to the glenohumeral joint include the rotator cuff, the long head of the biceps tendon, and the pericapsular muscles. Dynamic stabilizers are active when the shoulder is in motion, while static stabilizers are always in use even when the shoulder is at rest. Together, static and dynamic stabilizers allow the humeral head to translate just 1 millimeter during active range of motion in the normal shoulder.16 Glenohumeral instability occurs when there is a violation of the static or dynamic stabilizers of the joint, which enables excessive translation of the humeral head on the glenoid.
Pathophysiology
Anterior shoulder instability occurs when a force is placed on the shoulder when the arm is in an abducted, externally rotated position.5 Anterior dislocation commonly results in detachment of the anteroinferior labrum and the anterior band of the inferior glenohumeral ligament, resulting in a Bankart lesion. Horst et al. noted that 73 percent of anterior shoulder dislocations are associated with Bankart lesions.17 Further, a Hill-Sachs lesion, or an osteochondral compression fracture in the posterolateral humeral head, is the other major pathology associated with anterior shoulder dislocations. The Hill-Sachs lesion occurs when the posterolateral humeral head engages with the glenoid rim and occurs in 84 percent of anterior shoulder dislocations.17 Posterior shoulder instability occurs when a force is placed on the shoulder in a flexed, adducted, and internally rotated position.10 Similar to anterior shoulder dislocations, posterior shoulder dislocations are associated with additional soft tissue and bony injuries. These include a reverse Bankart lesion, or detachment of the posterior labrum, and reverse Hill-Sachs lesion, or an osteochondral compression fracture in the anteromedial humeral head.10 Multidirectional shoulder instability, which is defined as glenohumeral instability in two or more planes of motion (anterior, posterior, or inferior), occurs through two mechanisms.11,18 First, repetitive activities and overuse result in microtrauma, which ultimately causes laxity in the capsular and ligamentous stabilizers of the glenohumeral joint. Alternatively, general ligamentous laxity, most often from connective tissue disorders such as Marfan syndrome, Ehlers-Danlos syndrome, or hypermobility joint syndrome, can result in multidirectional instability. Lastly, pan-labral injuries, which involve simultaneous injuries to the anterior, posterior, and superior labrum, are generally the result of trauma or contact sports.19
History
A detailed history is crucial in the evaluation and diagnosis of glenohumeral instability. It is important to inquire about the cause (major trauma, minor trauma, no trauma), direction (anterior, posterior, or multidirectional), degree (subluxation or dislocation), and chronology (acute, recurrent, or chronic) of instability. With regard to the direction of instability, some patients may accurately report the direction of their dislocation. For others, the position of the arm at the occurrence of injury or at maximal pain may help distinguish between anterior and posterior shoulder instability. The physical exam is critical in determining directionality of instability. For anterior shoulder instability, pain or the dislocation event typically occurs in an abducted, externally rotated arm.5 For posterior instability, pain or the dislocation event typically occurs in a flexed, adducted, and internally rotated arm.10 Further, it is important to gather information about functional limitations from instability and about nighttime symptoms, which may indicate more severe disease. Details of prior management, nonoperative or operative, should be gathered. Lastly, it is important to gather key elements of medical and social history, including the presence of seizure disorders, psychiatric illness, connective tissue disorders, occupation, and sport participation.
Physical Examination
The physical examination of glenohumeral instability begins with inspection of the shoulder and upper extremity.2,3,5,9-11 The shoulders should be compared for asymmetry, and any evidence of obvious deformity, atrophy of the deltoid or rotator cuff musculature, and scapular winging should be noted. Next, palpation of both the unaffected and affected shoulder should be performed. In the case of an acute dislocation, it may be possible to palpate the humeral head anteriorly, posteriorly, or inferiorly based on the direction of dislocation. Furthermore, a soft tissue concavity may be both visible and palpable.5 Range of motion and strength assessment with respect to forward elevation, abduction, external rotation at the side, external rotation in abduction, internal rotation in abduction, and internal rotation to vertebral height should then be performed in both the unaffected and affected shoulder. A thorough neurological exam is critical before and after reduction of any dislocation as there are often coexistent nerve injuries.20 Atrophy or weakness of the deltoid and teres minor muscle and changes in sensation to the lateral shoulder may be suggestive of injury to the axillary nerve.21
Special Tests for Anterior Instability
Provocative maneuvers used in the assessment of anterior glenohumeral instability include the apprehension, relocation, and anterior release tests, which are typically performed in succession, and the anterior load and shift test.22,23 For the apprehension, relocation, and anterior release tests, the patient is supine with the shoulder in 90-degrees abduction, the shoulder in full external rotation, and the elbow in 90 degrees of flexion (figure 3.1; video 3.1). The apprehension test is positive if the patient feels discomfort or a sense of instability in this position. Next, the relocation test is performed with the patient in the same position. The examiner applies a posterior force to the affected shoulder, and the test is positive if the patient no longer feels a sense of instability. Lastly, the anterior release test is performed with the examiner’s hand starting on the humeral head, reducing the shoulder as it is placed into the apprehension position. The examiner’s hand is then removed, and the test is positive if the patient has a sense of anterior apprehension.
Video 3.1: Apprehension, Relocation, and Anterior Release Tests. The examiner performs the apprehension, relocation, and anterior release tests for anterior shoulder instability in succession.
The anterior and posterior load and shift test is an important maneuver used in the assessment of anterior and posterior glenohumeral instability (video 3.2; figure 3.2).23,24 The patient is placed supine to stabilize the scapula with the shoulder in 45 to 90 degrees of abduction, the shoulder in full external rotation, and the elbow in 90 degrees of flexion. Alternatively, the test can be performed with the patient upright if the scapula can be stabilized manually. The examiner holds and gently translates the humerus. For anterior instability, the examiner gently applies an axial force to the patient’s humerus into the glenoid, while simultaneously applying an anterior translational force. For posterior instability, the examiner gently applies an axial force to the patient’s humerus into the glenoid, while simultaneously applying a posterior translational force. The test is graded on a scale of 0 to 3, representing various degrees of humeral head shifting relative to the glenoid.23 Table 3.1 outlines the grading scale for instability.
| Grade | Description |
|---|---|
| 0 | Little to no movement of the humeral head |
| 1+ | Shift to the edge of the glenoid |
| 2+ | Head shifts past the edge of the glenoid with spontaneous relocation |
| 3+ | Head shifts past the edge of the glenoid without spontaneous relocation |
A positive value indicates anterior direction, while a negative value indicates posterior direction.
Grade 0 denotes little or no movement of the humeral head. Grade 1+ represents a shift to the edge of the glenoid. Grade 2+ is when the head shifts past the edge of the glenoid with spontaneous relocation. Grade 3+ is the same as Grade 2+ but without spontaneous relocation. Notably, a patient’s shoulder can be dislocated and then relocated with this maneuver in someone with a high grade of instability (figure 3.3). A positive value indicates anterior direction, while a negative value indicates posterior direction.
Video 3.2: Anterior Load and Shift Test for Anterior Instability. The examiner demonstrates the appropriate technique for the anterior load and shift test with the patient in the lateral decubitus position in the operating room. The patient’s scapula is stabilized by a bean bag. The examiner gently applies an axial load to the humerus into the glenoid fossa while also applying an anterior force. The grade of instability is determined by the amount of anterior translation of the humerus compared to the glenoid. Here, the anterior load and shift test displays Grade 2+ translation.
Video 3.3: Anterior Load and Shift Test. In this patient with anterior instability of the shoulder, the examiner can dislocate the humeral head from the glenoid cavity with an anterior force. The examiner can also relocate the humeral head back into the glenoid cavity with a posterior force. This finding is consistent with a 3+ anterior load and shift test.
Alternatively, another physical examination maneuver to help diagnose instability of the shoulder is the Gagey test.25,26 In this test, the examiner stabilizes the patient’s shoulder girdle and then passively abducts the shoulder. Shoulder abduction greater than 105 degrees while the scapula is stabilized is considered a positive test and is indicative of laxity in the inferior glenohumeral ligament (figure 3.3).
Special Tests for Posterior Instability
The posterior stress test is a provocative maneuver used for the examination of posterior instability (video 3.4).27 The patient is supine on the examiner’s table to stabilize the scapula, with the shoulder flexed to 90 degrees, adducted, and internally rotated and the patient’s elbow flexed to 90 degrees. A test result is positive if there is pain or a sense of instability when the examiner applies a posteriorly directed force in this position.
Video 3.4: Posterior Stress Test. The examiner demonstrates the appropriate technique for the posterior stress test with the patient lying supine on the examination table to stabilize the scapula. The patient’s shoulder is flexed to 90 degrees, adducted, and internally rotated with the patient’s elbow flexed to 90 degrees. The examiner then applies a posteriorly directed force to the humeral head. A test is considered positive if there is pain or a sense of instability with the maneuver.
Further, the posterior load and shift test is used in the assessment of posterior instability as well (video 3.5).23,27 The examiner applies an axial force to the patient’s humerus into the glenoid, while simultaneously applying a posterior force. Notably, the posterior load and shift uses the same grading scale as anterior load and shift, with a minus sign to signify a posterior direction (video 3.6–3.7; figure 3.4).
Video 3.5: Load and Shift Test for Anterior and Posterior Instability. The examiner demonstrates the appropriate technique for the anterior and posterior load and shift tests with the patient lying supine on the examination table in order to stabilize the scapula. The patient’s shoulder is placed in approximately 45 degrees of abduction and external rotation. First, the examiner applies an axial load to the humerus into the glenoid fossa then applies an anterior force, performing the anterior load and shift. Next, the examiner applies an axial load to the humerus into the glenoid fossa while also applying a posterior force, performing the posterior load and shift. A test is graded, on a scale of 0 to 3, depending on the degree of increased anterior or posterior translation of the humerus compared to the glenoid. Here, the patient exhibits pain and increased translation upon the posterior load and shift maneuver.
Video 3.6: Load and Shift Test for Posterior Instability. The examiner demonstrates the appropriate technique for the posterior load and shift test with the patient in the operating room. The examiner applies an axial load to the humerus into the glenoid fossa while also applying a posterior force. This test is graded on a scale of 0 to 3, with 3 indicating movement of the humeral head beyond the glenoid edge without spontaneous relocation. Here, the shoulder can be dislocated posteriorly, and there is no spontaneous relocation of the shoulder, indicating a test result of 3-.
Video 3.7: Posterior Load and Shift Test. A patient suffering from recurrent posterior dislocations of the right shoulder is placed in the lateral decubitus position in the operating room and stabilized with a bean bag. The examiner performs the posterior load and shift test on the patient’s right shoulder. With one hand, the examiner stabilizes the right forearm, and, with the other hand, the examiner provides a posterior force to the right upper arm. There is significant posterior translation of the humerus past the edge of the glenoid in this patient with spontaneous reduction, indicating a test result of 2-.
In some cases, dislocations may occur with proximal humerus fractures, resulting in fracture dislocations. The clinical examination and radiographs of a patient with bilateral posterior fracture dislocations are shown in video 3.8 and figure 3.5.
Video 3.8: Examination of a Patient with Bilateral Posterior Fracture Dislocations. The patient presents with posterior fracture dislocations of the bilateral proximal humerus. The patient can only forward elevate his right arm to 50 to 60 degrees and is then unable to externally rotate his right arm when it is at his side. Similarly, the patient can forward elevate his left arm to only 40 to 50 degrees and is also unable to externally rotate his left arm when it is at his side. The patient is attempting to compensate by moving his scapulothoracic articulation.
Special Tests for Multidirectional Instability
Lastly, multidirectional glenohumeral instability denotes instability in two or more directions. It is important to first perform both the anterior and posterior maneuvers for instability when assessing for this pathology. In addition, the sulcus sign is a technique for the assessment of capsular laxity (video 3.9).28 The examiner applies an inferiorly directed gentle traction force to the patient’s arm starting in a neutral position. (video 3.10; figure 3.6). Next, the examiner externally rotates the arm to see if the sulcus disappears or remains. A persistent sulcus in external rotation indicates a positive test result and abnormal capsular laxity. Further, the sulcus sign can be classified, based on the acromiohumeral distance produced by inferior traction, into Grade I (<1.0 cm), Grade II (1.0 to 2.0 cm), and Grade III (>2.0 cm).28 Higher grades are associated with MDI and capsular laxity.28
Video 3.9: The Sulcus Sign. The examiner demonstrates the appropriate technique for the sulcus test. The patient is positioned with the arms resting at the sides. The examiner applies an inferiorly directed force to the patient’s arm starting in a neutral position. The test result is negative if no sulcus or groove appears at the superior aspect of the humeral head.
Video 3.10: Positive Sulcus Sign in the Shoulders. The examiner performs the sulcus test on a patient’s bilateral shoulders. The test is considered positive if a sulcus or groove appears between the acromion and the superior aspect of the humeral head and does not diminish with external rotation. A positive test indicates insufficiency of the capsular restraints. Here, the patient displays a positive sulcus sign in both her left and her right shoulder.
The Beighton score is used to assess the patient for generalized hypermobility and ligamentous laxity, which can be caused by connective tissue disorders (figure 3.7).23 A score between 5 and 9 is considered positive for generalized joint laxity, while a score between 0 and 4 is considered negative for generalized joint laxity. The scoring system is depicted in table 3.2.
| Assessment Site for Joint Laxity | Right | Left |
|---|---|---|
| Hyperextension of the small finger >90° | 1 | 1 |
| Ability to oppose the thumb to the forearm | 1 | 1 |
| Knee hyperextension >10° | 1 | 1 |
| Elbow hyperextension >10° | 1 | 1 |
| Ability to place palms on the floor with the knees extended while standing | 1 (both palms must touch) | |
Notably, 80 percent of patients with hypermobile Ehlers-Danlos Syndrome and on the hypermobility disorder spectrum present with pain or instability of the shoulder.29 Thus, it is important to perform a thorough assessment of joint hypermobility on these patients (video 3.11).
Video 3.11: General Examination for a Patient with Joint Hypermobility. The examiner demonstrates a general exam for a patient with joint hyperlaxity. In order, the examiner assesses MCP joint hyperextension, elbow extension, passive external rotation at the side, and passive external rotation at 90 degrees.
Sensitivities and specificities for all examinations described in chapter 3 are outlined in table 3.3.26,30-33
| Test | Sensitivity | Specificity |
|---|---|---|
| Apprehension Test31,33 | 66% | 95% |
| Relocation Test26 | 65% | 90% |
| Anterior Release Test32 | 82% | 86% |
| Anterior Load and Shift Test32 | 38% | 89% |
| Gagey Test26 | 46% | 38% |
| Posterior Stress Test30 | 19% | 99% |
| Posterior Load and Shift Test30 | 94% | 95% |
| Sulcus Sign33 | 28% | 97% |
Key Terminology
Instability of the humeral head in the anterior, or frontward, direction. ↵
Apprehension, Relocation, and Anterior Release Tests
Physical examination maneuvers for anterior shoulder instability. The patient is supine with the shoulder in 90-degrees abduction, the shoulder in full external rotation, and the elbow in 90 degrees of flexion. The apprehension test is positive if the patient feels discomfort or a sense of instability in this position. The relocation test is performed with the patient in the same position. The examiner applies a posterior force to the affected shoulder with their hand, and the test result is positive if the patient no longer feels a sense of instability. The anterior release test is performed with the examiner’s hand now removed from the shoulder. A positive test result occurs if the patient again has a sense of anterior apprehension. ↵
Instability that occurs in the absence of trauma, such as in a shoulder that has already sustained extensive structural damage, or because of ligamentous laxity. ↵
Humeral head has totally come out of the socket. ↵
Musculature, including the rotator cuff and the pericapsular muscles, that provide stability to the glenohumeral joint while it is in motion. ↵
Physical examination maneuver for inferior laxity of the shoulder. The examiner stabilizes the patient’s shoulder girdle and then passively abducts the shoulder. A positive test result is indicated by shoulder abduction greater than 105 degrees and is indicative of laxity in the inferior glenohumeral ligament. ↵
Pathological increased translation of the humeral head from the glenoid cavity. ↵
Physical examination maneuver used to assess anterior and posterior instability. The examiner applies an axial load to the humerus into the glenoid fossa while also applying either an anterior or posterior force. A test is graded on a scale of 0 to 3 based on whether there is increased anterior or posterior translation of the humerus compared to the contralateral side. ↵
Multidirectional Shoulder Instability
Instability in two or more planes of motion (anterior, posterior, or inferior). ↵
Posterior Shoulder Instability
Instability of the humeral head in the posterior, or backward, direction. ↵
Physical examination maneuver used for the examination of posterior instability. The patient is placed supine on the examiner’s table to stabilize the scapula, with the shoulder flexed to 90 degrees, adducted, and internally rotated, and the patient’s elbow flexed to 90 degrees. A test is positive if there is pain or a sense of instability when the examiner applies a posteriorly directed force in this position. ↵
Bony, capsular, cartilaginous, and ligamentous structures that provide stability to the glenohumeral joint. ↵
Partial dislocation with spontaneous reduction. ↵
Physical examination technique for the assessment of glenohumeral capsular laxity. The examiner applies a gentle, inferiorly directed traction force to the patient’s arm, starting in a neutral position, then externally rotates the arm. A positive test result is indicated by the appearance of a sulcus, or groove, that does not diminish with external rotation. ↵
Instability that arises from a forceful contact event that damages a previously structurally intact glenohumeral joint. ↵
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