Treatment of Recurrent Posterior Shoulder Instability



Treatment of Recurrent Posterior Shoulder Instability


Jeffrey S. Noble

Matthew B. Noble

Robert H. Bell





ANATOMY



  • Posterior instability may be secondary to a tear of the posteroinferior labrum or a patulous posterior capsule.








    Table 1 Classification of Posterior Instability

















    Acute posterior dislocation


    Without impression defect


    With impression defect


    Chronic posterior dislocation


    Locked (missed) with impression defect


    Recurrent posterior subluxation


    Voluntary



    Habitual (willful)


    Muscular control (not willful)


    Involuntary



    Positional (able to demonstrate)


    Nonpositional (unable to demonstrate)



  • Rarely, it can involve a posterior labrocapsular periosteal sleeve avulsion or an avulsion of the posterior glenohumeral ligaments as they insert on the humerus (posterior humeral avulsion of glenohumeral ligament [HAGL] lesion).


  • Recently, Kim et al24 described a concealed and incomplete avulsion of the posteroinferior labrum (type II marginal crack or Kim lesion).


  • Pathology may also be bony in nature and secondary to posterior glenoid avulsions, erosions, increased glenoid retroversion, or large engaging reverse Hill-Sachs impression defects.


PATHOGENESIS



  • A significant percentage of patients (40% to 50%) with recurrent posterior subluxation relate a history of trauma. Usually athletes, these individuals are typically 18 to 30 years of age and are involved in competitive contact sports.


  • Traumatic cases are often associated with an injury where the arm is in a straight and locked position such as in weightlifting or during football while line blocking. A fall or collision with the individual’s arm in the at-risk position (forward elevation, adduction, internal rotation) can also be the cause.


  • Frequently, instead of a traumatic event, subluxation episodes with a poorly defined onset are the initial presentation.


  • In many cases, especially with repetitive overhead endeavors such as swimming, gymnastics, baseball, and volleyball, the athlete recalls first the gradual onset of discomfort, with subluxation episodes occurring later. Such an onset is thought to be atraumatic and involves repetitive “microtrauma” with resultant stretching of the capsular restraints.


PATIENT HISTORY AND PHYSICAL FINDINGS



  • Whether the patient presents with a clear traumatic episode or a longer atraumatic course, he or she often has a feeling of the shoulder “coming out.” Such instability episodes occur when the arm is in the at-risk position of forward elevation, adduction, and internal rotation.


  • Patients often describe a vague discomfort, pain, or weakness as their principal complaint. This actually may lead to misdiagnosis at first.


  • True apprehension or a feeling of “impending doom” when the extremity is placed in the provocative position is less common but can be present.


  • Overhead throwers may complain of a loss of velocity, fatigue, or aching over the posterior shoulder.


  • Usually, there is no obvious asymmetry of the muscles on inspection.







    FIG 1 • Younger patient able to voluntarily demonstrate, with muscular contraction and positioning of the upper extremity, his posterior instability.


  • Palpation may elicit some tenderness along the posterior glenohumeral joint line.


  • Crepitation or a click along the posterior joint line due to labral pathology may be noted.


  • The range of motion is full, often with a decrease in internal rotation and an excess of external rotation.


  • Often, patients, if voluntary subluxators, can reproduce the subluxation episode on command with arm position and selective muscular contraction (FIG 1).


  • Physical examination should include the following:



    • Modified load shift test: documents direction and degree of instability


    • Supine load shift test (Gerber and Ganz16): documents direction and degree of instability


    • Seated load shift test: documents direction and degree of instability


    • Posterior stress test: documents direction and degree of instability


    • Sulcus sign: evaluates for an inferior component of the posterior instability (bidirectional) or a more global instability (ie, multidirectional instability)


    • Scapular compression test: verifies the importance of scapular winging in the patient’s ability to reproduce the instability and proves to the patient the need to strengthen the periscapular musculature to control instability


    • Jerk test: to document instability. A painful jerk test suggests a posteroinferior labral lesion and is a predictor of the success of nonoperative treatment.


    • Kim test: evaluates for the presence of a labral tear posteriorly


    • Pivot shift of the shoulder: documents direction of the instability


IMAGING AND OTHER DIAGNOSTIC STUDIES



  • Radiographic evaluation includes a three-view trauma series of the shoulder, including a true anteroposterior (AP) view of the shoulder, a scapular lateral, and, more importantly, an axillary view.



    • A Velpeau axillary view can be substituted if the attempted axillary view is impossible because of painful abduction of the shoulder.


    • Axillary radiographs of patients with a voluntary component to their instability can be taken while the patient reproduces and maintains the subluxation episode to document the direction (FIG 2A).






      FIG 2A. Axillary radiograph of patient with voluntary posterior instability, reproducing the instability while taking the radiograph. B. CT scan demonstrating significant posterior glenoid retroversion in a patient with posterior instability.


    • A computed tomography (CT) scan can be helpful to evaluate humeral head defects and associated fractures of the tuberosities, humeral shaft, and posterior glenoid rim. Significant posterior glenoid retroversion can also be demonstrated on CT scanning (FIG 2B).


    • Magnetic resonance imaging (MRI) is the imaging modality of choice after plain radiographs to evaluate the posterior capsule and labrum for tears and associated pathology.


    • In certain situations, an MRI arthrogram can help diagnose a posteroinferior labral tear.


DIFFERENTIAL DIAGNOSIS



  • Superior labrum anterior to posterior tear (SLAP)


  • Anterior instability


  • Multidirectional instability


  • Internal impingement


  • Posterior Bennett lesion


NONOPERATIVE MANAGEMENT



  • Nonsurgical treatment of posterior unidirectional instability is reportedly successful in up to 80% of the patients.11,21



    • The physical therapy program consists of concentric and eccentric resistive band exercises that strengthen the external rotators, the deltoid, and the important periscapular musculature.



      • Resistive upright and seated rows, with an emphasis on trying to pinch the medial scapular borders together during the exercise, are key, especially in patients whose scapular winging contributes to their instability.



    • A strengthening program as well as a sport-specific attempt to decrease those activities that place the arm at risk is key.


  • The length of nonoperative treatment must be individualized.



    • Patients who have lower physical demands, are younger, and those with an atraumatic history are treated 6 months or more.


    • Higher level athletes or those who have a traumatic cause with an associated labral tear are more likely to require surgical treatment. Despite their associated labral tears, such elite athletes are often treated with an exercise strengthening program for at least 3 months.


SURGICAL MANAGEMENT



  • Although open procedures have been the mainstay and gold standard in the treatment of patients with recurrent unidirectional posterior subluxation, arthroscopic treatment has become common.



    • As with anterior instability, arthroscopic evaluation in posterior instability patients has led to the diagnosis and treatment of an increasing number of associated soft tissue and articular injuries. Obviously, arthroscopic treatment of posterior capsular avulsions or redundancy in the absence of soft tissue deficiencies or bony abnormalities can have similar success rates without the morbidity of more extensive open surgery.2,7,24,25,27,38


  • Surgical treatment is considered only after an adequate trial of strengthening has failed and the patient remains significantly symptomatic.


  • The ideal surgical candidates are those with recurrent posterior unidirectional subluxation secondary to a traumatic episode. These patients often have an associated traumatic posterior labral tear, which is optimal for arthroscopic repair.



    • Patients with atraumatic subluxation due to capsular redundancy can be managed either through an open procedure or an arthroscopic capsular shift or plication procedure.


    • Patients who have multifactorial causes for their instability or are revision situations may be treated better with an open approach.


Preoperative Planning



  • An extensive history and physical examination are key to establishing the direction and degree of the patient’s instability.


  • All imaging studies are reviewed. Plain films and MRI studies are reviewed for the presence of old fractures, loose bodies, and hardware from previous procedures. More importantly, the MRI establishes whether the instability is due to an associated traumatic posterior labral tear or capsular redundancy.


  • Associated bony pathology (traumatic glenoid avulsions, glenoid retroversion) and soft tissue deficiencies (from previous procedures) should be addressed concurrently.


  • In rare instances, a sizable reverse Hill-Sachs lesion may exist and can be treated in an arthroscopic or open manner.12


  • Examination, this time under anesthesia, should be accomplished before positioning to confirm the direction and degree of the instability.


Jul 22, 2016 | Posted by in ORTHOPEDIC | Comments Off on Treatment of Recurrent Posterior Shoulder Instability

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