Abstract

It is critical to diagnose multidirectional instability (MDI) because standard surgical procedures used to treat traumatic anterior shoulder instability are oftentimes inadequate to address MDI. This diagnosis can be made challenging due to the similarity between laxity and instability. The most common cause of MDI is congenital redundancy or laxity, but poor rotator cuff control or periscapular weakness can be common predisposing risk factors as well. Diagnosis procedure includes a thorough history for recurrent factors, and a multitude of physical exams such as, load and shift test, jerk test, Kim test, strength test, and range of motion test. Imaging techniques including radiograph, MRI, and CT scan can be useful in identifying possible anatomic variations or pathologic causes leading to MDI.

Multidirectional Instability

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  Epidemiology

  
  
  
  
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    Multidirectional instability (MDI) is characterized by symptomatic glenohumeral translation, subluxation, or dislocation in more than one direction that leads to functional impairment.

    
    
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    The relative incidence and prevalence of the disease are unknown, but it is most commonly seen in young female athletes who regularly perform overhead activities.

  
  
  
  
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  Mechanism of Injury

  
  
  
  
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    Repetitive microtrauma and selective stretching to the shoulder capsule over time distend the joint and can lead to instability.

    
    
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    Muscular imbalance is a contributing factor in MDI with poor rotator cuff control or periscapular weakness leading to subjective shoulder instability.

  
  
  
  
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  History and Physical Examination

  
  
  
  
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    Patients report insidious onset of shoulder pain and often subluxation without an emergency department (ED) visit.

    
    
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    A complete physical examination of the upper extremities should include inspection, palpation, range of motion of the bilateral shoulders, a neurologic examination, rotator cuff evaluation, and a stability assessment.

    
    
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    Diagnosis is largely based on clinical examination.

  
  
  
  
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  Imaging

  
  
  
  
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    MDI is largely a clinical diagnosis; however, radiography and magnetic resonance imaging (MRI) and magnetic resonance arthrography (MRA) can be helpful to identify bony dysplasia, labral abnormalities, and possibly capsular redundancy, particularly involving the inferior pouch.

  
  

Epidemiology

The term multidirectional instability was first coined by Neer and Foster in 1980 ( ) in their description of the inferior capsular shift operation. At the time, these patients were differentiated from patients with standard anterior instability because it was emphasized that the inferior component of the instability was the major pathoanatomic feature, and any success with surgical treatment required elimination of the inferior capsular redundancy. Similarly, divided patients with recurrent glenohumeral instability into one of two categories. The first group tends to have a traumatic, unidirectional dislocation resulting in a Bankart lesion that would require surgical repair (TUBS). The second group has atraumatic MDI that is often bilateral and can be managed with rehabilitation but requires an inferior capsular shift for surgical treatment (AMBRI). characterized MDI as symptomatic global laxity of the shoulder with increased capsular volume and a rotator interval capsular deficiency. It is important to recognize patients with MDI and capsular hyperlaxity because the standard surgical procedures used to treat traumatic anterior instability are often not adequate to address the pathology involved in MDI ( ). However, it is difficult to determine which patients have MDI and which do not because there is certainly overlapping pathology. Furthermore, there is no accepted universal criteria for diagnosing MDI.

When discussing MDI, it is important to differentiate between laxity and instability of the shoulder. Laxity describes the amount of humeral head translation with respect to the glenoid, which is intrinsic to an individual’s normal anatomy and is asymptomatic. Put another way, certain patients have lax shoulders that have demonstrable physical examination findings (e.g., sulcus sign) without symptoms. Instability, on the other hand, is symptomatic glenohumeral translation, subluxation, or dislocation that leads to functional impairment ( ). reviewed 18 different shoulder instability classification schemes and proposed a new FEDS classification based on the f requency, e tiology, d irection, and s everity of instability. In this classification system, Kuhn proposed eliminating the term MDI because of a lack of an agreed-upon definition. However, the term is firmly entrenched in orthopaedic teaching worldwide and continues to imply certain patient characteristics summarized in Box 3A.1 .

There is a paucity of literature evaluating the epidemiology of MDI. Three recent meta-analyses evaluating the surgical and nonsurgical management of MDI highlight the dearth of high-quality prospective literature evaluating the condition ( ). In these studies, the average age of the pooled group of patients was the mid 20s, and the unifying physical examination findings were a positive sulcus sign and load and shift test. In addition, nearly all of the literature on MDI consisted of retrospective case series (level 4) evaluating the results of a specific treatment. Therefore the relative incidence and prevalence of MDI as a condition or group of conditions is unknown; thus long-term prospective data re needed.

Mechanism of Injury

The most common reason for MDI is thought to be a congenital redundancy or laxity of the shoulder capsule ( ). Asymptomatic shoulders can also have this capsuloligamentous laxity, which is why multiple factors can contribute to the pathophysiology of MDI. Box 3A.2 summarizes some prevailing theories as to the pathophysiology of MDI. Generalized joint laxity can be caused by a multitude of factors and is present in 40% to 70% of patients with MDI ( ). Most patients with hyperlaxity do not have an identifiable syndrome or condition, but patients with collagen abnormalities such as Ehlers-Danlos and Marfan syndromes are important to identify because these patients are known to have poorer surgical outcomes after stabilization procedures ( ).

The scapular stabilizers and rotator cuff provide dynamic stability to the shoulder. Recent studies have identified muscular imbalance as a contributing factor in MDI with poor rotator cuff control or periscapular weakness leading to subjective shoulder instability ( ). For this reason, sedentary individuals and women with poor muscular development present with MDI ( ). Last, labral hypoplasia or abnormalities in glenoid size may diminish the congruency and static stability of the glenohumeral joint, contributing to instability ( ).

Overhead athletes in sports such as swimming, volleyball, and gymnastics are susceptible to MDI ( ). MDI is thought to develop in response to repetitive microtrauma and selective stretching of the shoulder capsule, resulting in increased glenohumeral joint volume and capsular redundancy ( ). These patients may not present with generalized laxity and may not have laxity of the opposite shoulder.

History and Physical Examination

In contradistinction to a traumatic anterior dislocation, the clinical presentation of MDI is often insidious, or a trivial mechanism may be identified leading to the onset of shoulder pain and subluxation without an ED visit ( ). Patient age is typically the teens or 20s. In those with generalized hyperlaxity, there may be no identifiable inciting event. Trauma, athletic overuse, or inactivity can contribute to the onset of symptoms with MDI. It is important to remember that a history of a significant traumatic event does not exclude a patient from having MDI ( ). A single traumatic event can result in labrum injury, rendering athletes with lax shoulders to begin with more unstable ( ). Overhead athletes can present with pain, subluxation, or neurologic symptoms such as numbness and paresthesias ( ). Last, intentional or volitional instability of the shoulder should be identified because it certainly affects the potential for treatment success. Box 3A.3 summarizes our approach to taking a history on a patient with suspected MDI. In addition, although there is frequently global capsular laxity, in the clinical setting most patients complain of pain or instability with primarily an anteroinferior or posteroinferior presentation. In other words, for a patient with primarily an anteroinferior instability pattern, the patient will often complain that putting the arm in a position of abduction and external rotation provokes the greatest degree of symptoms. Conversely, those with primarily a posteroinferior problem will complain that placing the arm into forward flexion and adduction precipitates symptoms.

Box 3A.4 summarizes the physical examination checklist in MDI. First, the entire shoulder girdles of both shoulders need to be visible both anteriorly and posteriorly to compare the symptomatic and asymptomatic sides. Throughout the patient’s physical examination, reproduction of the patient’s symptoms is critical to note. The overall physical examination of the upper extremities should include inspection, palpation, range of motion of the bilateral shoulders, a neurologic examination, rotator cuff evaluation, and a stability assessment.

Begin by inspecting the shoulders for posture, scapular position, muscle atrophy, and symmetry. Next, the patient’s degree of generalized ligamentous laxity should be determined using the Beighton scale ( Box 3A.5 ) ( ). Generalized ligament laxity can be associated with connective tissue disorders such as Ehlers-Danlos syndrome or Marfan syndrome. It is important to recognize these connective tissue disorders because patients with them have poorer results after surgical stabilization ( ).

Next, palpation of the anterior and posterior glenohumeral joint lines should be evaluated, noting any pain or fullness. Tenderness with palpation of either the anterior or posterior joint line is a common finding that can sometimes help differentiate anterior or posterior instability when present in isolation ( ). It is a nonspecific finding that can represent capsular stretching, labral pathology, or cuff pathology. Routine palpation to assess for concomitant pathology of the AC joint and biceps tendon is performed as well. Patients with MDI can also have tenderness to palpation at the medial angle of the scapula ( ).

Range of motion is then tested. A standard evaluation includes forward elevation in the frontal and scapular planes. External rotation at the side is measured; greater than 90 degrees of external rotation with the elbows at the side is common in MDI and hyperlaxity. Internal rotation behind the back is documented as the highest spinal level that the patient can reach. Internal and external rotation should also be measured at 90 degrees of abduction in the supine position. The hyperabduction test described by can be used as well. The glenohumeral abduction is compared between the asymptomatic and symptomatic shoulders, and a difference of greater than 20 degrees is a positive finding. Hyperabduction past 180 degrees is representative of MDI.

Scapular motion and dyskinesis should be observed from behind the patient during arm elevation. Asymmetry in scapular motion should be noted ( Fig. 3A.1 ). Scapular winging can also be observed by having the patient do a standing pushup against the wall. Scapulothoracic motion asymmetry is associated with MDI.

Scapular dyskinesis where the inferior angle is prominent and the scapular position is protracted and internally rotated.

Courtesy of George F. Rick Hatch, III, MD.

Strength testing is performed, beginning with the evaluation of deltoid strength in abduction. The empty can test evaluates the supraspinatus. External rotation strength evaluates the posterior rotator cuff. Liftoff, bear hug, and the belly press tests evaluate the internal rotation strength of the subscapularis. Although there is a low association of rotator cuff tears along with MDI, strength of the rotator cuff should be evaluated as well because of its dynamic stabilizing effect in MDI ( ). A complete neurovascular examination should be performed, including evaluation of the integrity and symmetry of the patient’s motor and sensory examination. In addition, concomitant pathology such as thoracic outlet syndrome should be ruled out in patients with paresthesias or numbness by using the Adson test. A positive test result is indicated by a diminished radial pulse provoked by head rotation while abducting and externally rotating the shoulder.

The final portion of the physical examination is the stability assessment. This portion includes both laxity tests, which examine the degree of humeral head translation, and provocative maneuvers, which attempt to reproduce the patient’s instability symptoms. Inferior laxity is assessed first with the sulcus sign ( ) ( Fig. 3A.2 ). The sulcus sign is performed with the patient sitting upright with the shoulder in neutral rotation and the arm at the side. Axial traction is then applied to the upper arm and the amount of inferior subluxation of the humeral head in relation to the acromion is measured ( ). Grade 1 is a distance of less than 1 cm, grade 2 is 1 to 2 cm, and grade 3 is more than 2 cm. The sulcus sign is pathognomonic for inferior instability if it reproduces the patient’s symptoms of apprehension and pain, but a sulcus sign can also be present in asymptomatic individuals ( ). The sulcus sign is repeated with the arm in external rotation; persistent sulcus sign in external rotation can indicate a deficient rotator interval capsule ( )

A and B demonstrates the sulcus sign, in the anteroposterior and lateral views, respectively. One hand stabilizes the scapula while the other hand, not pictured, performs axial traction.

The load and shift test can be performed in both the anterior and posterior directions to measure the amount of humeral head translation in relation to the glenoid. This test is difficult to perform in a symptomatic, nonrelaxed patient. With the patient in a supine position, the patient’s arm should be in approximately 20 degrees of abduction, 20 degrees of forward flexion, and neutral rotation. The humeral head is then axially loaded, and the examiner pushes the humeral head either anteriorly or posteriorly. The amount of translation of the humerus is graded 1 with 0 to 1 cm translation up the glenoid face, graded 2 with translation to the glenoid rim, and graded 3 with translation over the glenoid rim ( ).

Anterior instability can be assessed with the apprehension test. This test is performed with the patient supine. The patient’s shoulder is placed at 90 degrees of abduction while the arm is brought into maximum external rotation ( ). Reproduction of the patient’s symptoms of apprehension in this position is an indicator of anterior instability. In patients with a positive apprehension test result, the relocation test can be performed as an adjunct in the diagnosis of instability. With the patient in the same position, a posteriorly directed force is applied to the humeral head, relieving the symptoms and allowing the patient to tolerate more external rotation with the shoulder in abduction ( ).

Posterior instability is best evaluated using the jerk test. The jerk test can be performed with the patient standing, supine, or in the lateral decubitus position. The examiner stabilizes the scapula by grasping the distal clavicle and the scapular spine with one hand and holds the patient’s elbow with the other while placing the arm in 90 degrees of forward flexion and internal rotation. The flexed elbow is pushed posteriorly while the shoulder girdle is pushed anteriorly. A positive test result reproduces symptoms or provokes a sudden jerk as the humeral head slides over the glenoid rim ( ). Posterior instability can also be reproduced by having the patient place her or his arm in a position of instability in adduction and forward flexion, creating discomfort, and transition to abduction and extension, leading to relief and reduction of the shoulder. The Kim test ( Fig. 3A.3 ) is another useful test for evaluating posterior instability. With the patient seated, the arm is brought into 90 degrees of abduction. The examiner holds the patient’s elbow and lateral aspect of the proximal arm while simultaneously applying an axial loading force and a 45-degree upward diagonal elevation to the distal arm and an inferior and posterior force to the proximal arm. The arm is then brought into adduction. A sudden onset of posterior shoulder pain is a positive result ( ). O’Brien’s test, or the active compression test, is performed by adduction of the shoulder in the standing position with the forearm pronated (thumb down). The arm is then loaded inferiorly, and pain is reproduced. In a positive test result, the pain is then relieved by supination of the forearm. This test is sensitive but not specific for superior labral tears.

Demonstration of the Kim test. Position A is the patient’s arm in abduction with the examiner applying an axial load and inferior posterior force on the proximal arm. As the patient’s arm is brought into adduction, as seen in position B, the patient feels the onset of posterior shoulder pain.

Imaging

Multidirectional instability is largely a clinical diagnosis; however, imaging is important for identifying possible anatomic variations or pathologic causes. Routine radiographs in three views are standard (anteroposterior, scapular Y, and axillary). In the setting of acute trauma, it may be difficult to obtain an axillary view, so a Valpeau view can be obtained. Radiographs are reviewed for bone defects about the glenoid rim or humeral head. Anatomic variations in glenoid version, or glenoid dysplasia, can also be evaluated. A shallow or hypoplastic glenoid can be seen on the axillary view. If a bony defect is identified or suspected, computed tomography (CT) can help further delineate the osseous injury. CT is the best modality for evaluating glenoid bone loss and dysplasia.

Magnetic resonance imaging and specifically MRA are the best modalities for evaluating the soft tissue structures of the shoulder, including the labrum and the capsuloligamentous complex. Patients with multidirectional instability typically do not have frank labral detachment, and many have no labral pathology at all. However, there may be subtle labral abnormalities visualized on MRI or at arthroscopy. These can include labral splits, cracks, chondrolabral retroversion, or a redundant joint capsule ( ). Multiple studies have attempted to quantify increased space within the joint capsule by measuring the width of the rotator interval or widening of the capsular space; however, these measurements are often not reliable based on the position of the shoulder and the volume of intraarticular contrast given ( ). According to , bulging of the rotator interval with contrast is pathognomonic for MDI.

If labral injuries are present, they can be identified on axial MRA or MRI views. Structural pathology leading to posterior instability can be seen at the posterior glenoid, including posterior labral tears, labrocapsular avulsions, or humeral avulsion of the glenohumeral ligament. This can lead to posterior translation of the humeral head within the glenoid, which is also seen on this view ( ).

Specific positioning of the arm can facilitate viewing of more subtle injuries if suspected. Positioning the arm in abduction and external rotation facilitates viewing of the anterior labrum and anterior capsuloligamentous structures, and flexion, adduction, and internal rotation allows visualization of the posterior shoulder ( ). Evaluation for other injuries, including rotator cuff tear, Bankart lesions, Hill-Sachs lesions, impaction fractures, and articular cartilage abnormalities, is also important to identify and although not associated with MDI can lead to shoulder pain and be a separate cause of instability.

Conclusion

The diagnosis of MDI is suspected in patients who develop atraumatic shoulder instability in their teens or 20s. A variety of causes lead to capsular laxity or redundancy. The key physical examination findings in MDI that identify this laxity, in our opinion, are the sulcus sign, glenohumeral hypermobility, generalized hyperlaxity, and the load and shift test. The presence or absence of the aforementioned physical examination findings can then be interpreted with the history and imaging to establish the degree, direction, and severity of the instability. Patients with MDI present with variable pathology and varying degrees of symptoms. Understanding the epidemiology, pathophysiology, and physical examination of these patients will result in an accurate diagnosis and lead to clinical success in nonoperative and surgical treatments to be discussed in the next section.

Abstract

The gold standard for the initial treatment of multidirectional instability (MDI) is conservative nonoperative rehabilitation, with the targeting of scapulothoracic dyskinesis as one of the primary goals. However, there exists a reliable, conservative surgical alternative for patients with recalcitrant MDI disability, and the alternative is arthroscopic capsular plication and shift. The technique utilizes the horizontal mattress suture (nonabsorbable) configuration multiple times to help secure the joint. The major goal of plication surgery is to allow a degree of structural stability that avhieves the previous balance of proprioception and dynamic and static stabilizing mechanisms.

Introduction

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  Since Neer and Foster’s seminal work on multidirectional instability (MDI) ( ), basic science and clinical research have helped to establish a better understanding of the basis for laxity, symptomatic laxity, and reestablishing glenohumeral stability in the management of this complex disorder ( ).

  
  
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  The diagnosis and treatment of patients with symptomatic MDI remains a challenging clinical entity for treating physicians ( ). The multiple static and dynamic stabilizers, including glenoid shape and version, labral configuration, and glenohumeral ligament integrity, as well as the delicate balance of scapulothoracic musculature, rotator cuff strength, and proprioceptive control, all contribute to a perplexing clinical presentation. These factors can make it difficult to select the most appropriate and effective treatment.

  
  
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  After this challenging diagnosis has been made, a conservative, nonoperative program to include lifestyle changes and therapeutic shoulder strengthening exercises should first be used in an effort to manage symptoms.

  
  
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  reported excellent and good outcomes in more than 80% of patients with atraumatic instability treated with a conservative strengthening program. reported improvement in symptoms after rehabilitation exercises and permanent activity modifications were implemented.

  
  
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  In contrast, a more recent study by followed symptomatic MDI patients undergoing nonoperative management over an average of 4 years and found that one third of the patients still had moderate to total disability.

  
  
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  Despite these revelations, a nonoperative rehabilitation program remains the gold standard for the initial treatment of MDI, with the targeting of scapulothoracic dyskinesis as one of the primary goals ( ). It is noteworthy that in longitudinal study, it was determined that if after 3 months of sound conservative care no significant progress was noted and symptoms persisted; further conservative measures were unlikely to be productive. In this setting, arthroscopic capsular plication becomes a reasonable alternative for patients with symptomatic MDI.

  
  
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  Arthroscopic capsular plication is currently considered a reliable surgical alternative for patients with recalcitrant MDI disability ( ), and its efficacy in the difficult athletic population has also been reported ( ).

  
  
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  An arthroscopic capsular plication can achieve the same goals of the time-honored open approach, and this has been elucidated in numerous studies focusing on volumetric measurements and surgical technique ( ).

  
  
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  The most difficult aspect of treating patients with symptomatic MDI is selecting the correct patients for more aggressive measures. The following section outlines the surgical technique in detail ( Video 3B.1 ).

• Video 3B-1
  

  Arthroscopic Capsular Plication

Surgical Technique: Arthroscopic Capsular Plication

Step 2

A posterior portal (PP) is placed slightly lateral to avoid limitations imposed by the glenoid rim. Diagnostic arthroscopy is then undertaken to avoid missing any cogent associated pathology. In most cases, the labrum is intact or slightly frayed because MDI is a primary capsular pathology. In the late stages, labral tearing may be present. The rotator interval is commonly patulous, and the articulating surfaces and rotator cuff are typically intact. A markedly positive drive-through sign is often encountered ( Fig. 3B.1 ). Dual anterior portals are established with the anterior-inferior portal (AIP) occupying the most inferior dimension of the rotator interval and the anterior-superior portal (ASP) at the most cephalad aspect of the interval.

Viewing from a posterior portal in a right shoulder in the lateral decubitus position, capsulitis (small arrows) is readily evident with a significant drive-through sign present (large arrows). (All subsequent images are in the same lateral position.) HH, Humeral head; L, labrum.

Step 3

Viewing from the ASP and using the AIP and PP as working portals, the capsule is carefully rasped to generate a healing response ( Fig. 3B.2 ). Aggressive shavers and suction are to be avoided for fear of damaging the often thin capsular tissue, especially posteriorly. After the capsule has been roughened, a 60-degree angled suture hook is passed from the posterior portal, targeting the most inferior aspect of the capsule at the 6 o’clock position ( Fig. 3B.3 ). Using the Snyder pinch-tuck technique, the inferior capsule is penetrated 1 cm from the labral edge, and the tip is brought through the capsule tissue only ( Fig. 3B.4 ). The hook is then advanced onto the glenoid labrum, which is pierced ( Fig. 3B.5 ), shifting tissue superiorly and allowing the absorbable shuttling suture to be wheeled into the joint. If the labrum is of potentially poor quality, a suture anchor is placed in lieu of the labrum to ensure proper fixation of the shifted capsule. The shuttling suture is collected and then retrograded with a high strength, nonabsorbable suture in tow ( Fig. 3B.6 ). A second pass is then made to complete a horizontal mattress suture configuration ( Fig. 3B.7 ). The suture tails are passed such that the suture knots can be tied farthest from the articulating surfaces. Although the suture can theoretically be tied as a sliding knot, alternating half hitches and posts are used to complete the plication stitch in an effort to avoid traumatizing the compromised tissue with the potential abrasion associated with sliding knots ( Fig. 3B.8 ).

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