Orthopedics and Orthopedics Surgery

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Shoulder Instability

The GH joint is inherently lax or loose, based on its osseous configuration. It exhibits the greatest amount of motion found in any joint in the body. The shoulder sacrifices stability for mobility and, as a result, is the most common joint dislocated, with over 90% of dislocations occurring anteriorly. “Shoulder instability” is an all encompassing term that includes the entire range of disorders such as dislocation, subluxation, and “pathologic” laxity. To understand the terminology related to shoulder instability, the various terms commonly associated with this condition must be defined. Translation is the movement of the humerus with respect to the glenoid articular surface. Laxity is the amount of translation that occurs. Some laxity is expected in normal shoulders. In fact, more than a centimeter of posterior laxity is common, especially in athletes. Consequently, instability must be defined as unwanted translations of the GH joint experienced by the patient. The ability of the examiner to translate the humerus greater than one cm or on to the rim of the glenoid is not equal to instability. However, if that maneuver reproduces the patient’s symptoms, which they may describe as “slipping” or “giving-way” or “painful,” then this is supportive evidence of GH joint instability. Finally, a shoulder dislocation is defined as the complete loss of the articulation between the humeral head and the glenoid socket. Subluxation refers to a partial loss of the GH joint articulation to the extent that symptoms are produced.

The stability of the GH joint is dependent on its static and dynamic stabilizers. The static stabilizers, such as the glenoid labrum and articular congruity, can be affected only by surgical means, not rehabilitation. However, the dynamic stabilizers, which primarily consist of the rotator cuff and the coordination between scapular movement and humeral movement, can be dramatically influenced by a proper rehabilitation program. Strengthening of the musculature around the shoulder is the foundation of all rehabilitation programs for shoulder instability.

We have already focused on the diagnosis and treatment of overhead athletes who have underlying microinstability that may predispose them to secondary impingement, internal impingement, rotator cuff tendinitis, and/or rotator cuff tears. This section focuses on the diagnosis and treatment of patients with symptomatic anterior, posterior, and multidirectional instability.

Anterior Shoulder Instability
Anterior shoulder instability is the most common type of GH joint instability and can be caused by a traumatic dislocation or repetitive microtrauma resulting in symptomatic episodes of subluxations. Over 90% of shoulder dislocations occur anteriorly, usually with the arm in abduction and external rotation. This represents the “weakest position of the glenohumeral joint biomechanically,” and is the “classic position” for anterior instability.

The diagnosis of traumatic anterior dislocation is usually straightforward when one takes a detailed history, including the position of the arm at the time of injury and the mechanism of injury, and performs a detailed physical examination. The mechanism of injury usually involves an indirect levering of the humeral head anteriorly with the shoulder positioned in a combination of abduction and external rotation. Less commonly, the dislocation can be caused by a direct blow to the posterior shoulder with the force directed anteriorly.

Physical Examination

The affected shoulder usually is held in slight abduction and external rotation, with the forearm cradled by the unaffected arm.

There may be a palpable fullness in the anterior shoulder.

Internal rotation and adduction may be limited.

Evaluation for neurologic injuries is critical before any relocation maneuver is performed. The axillary nerve is most commonly injured with an anterior dislocation. This risk increases with patient age, duration of dislocation, and the amount of trauma that caused the dislocation.

Critical in the evaluation process is a complete radiographic “trauma shoulder series” to rule out concomitant fracture.

Initial treatment includes a reduction procedure with some form of analgesic control, with radiographs after reduction to confirm successful relocation and a repeat neurologic examination to ensure no nerve injury or entrapment during the reduction.

Recurrent anterior instability is the most common problem after a primary anterior dislocation. The most consistent and significant factor influencing recurrence is age at primary dislocation, but in reality, this may be a reflection of the activities more common in a younger population than an older population. Patients younger than 30 years have an average risk of approximately 70% of recurrent dislocation when treated with a nonsurgical rehabilitation program. Overall, the average recurrence rate is approximately 50% with nonoperative management. Recurrent instability is diagnosed by history and confirmed with a thorough physical examination with patients demonstrating a positive apprehension sign (see Fig. 3–23) and positive relocation test (see Fig. 3–25). The natural history of recurrent anterior instability is altered if early operative stabilization is performed. In a prospective, randomized study, Kirkley and coworkers (1999) showed a significant difference in the rate of recurrent anterior dislocations in two groups of patients, average age 22 years. One group was treated with a rehabilitation program and had a redislocation rate of 47%, and the other group was treated with an arthroscopic stabilization procedure and had a redislocation rate of 15% with an average follow-up of two years.

Nonoperative Treatment
Conservative management of anterior shoulder instability has been associated with a more successful outcome in patients older than 30 years. Younger patients treated conservatively usually require a longer course of immobilization in hopes of achieving a successful outcome. However, it should be recognized that the length of immobilization has been only loosely associated with decreasing the risk of recurrence, with further scientific studies needed to prove its value. Because recurrence is the most common complication, the goal of the rehabilitation program is to optimize shoulder stability. Avoidance of any provocative maneuvers and careful muscle strengthening are important components of the rehabilitation program as outlined in the following protocol.

Operative Treatment
Operative stabilization is indicated in patients with irreducible dislocations, displaced tuberosity fractures, and glenoid rim fractures involving 25% or more of the anterior-inferior glenoid rim. Patients who experience three or more instability events in a year (recurrent) or instability during rest or sleep also are appropriate candidates for surgical management. A relative indication for surgical intervention is a younger patient, especially an athlete who desires continued participation in sports or work activities. In this population, early surgical intervention will reduce the risk of recurrent instability and allow a return to sport. The problem with conservative treatment in this patient group is that it is less likely to alter the natural history of the shoulder instability. The athlete may have fewer or no episodes of instability with a conservative treatment program during the “off-season” from her or his sport. However, with the return of the next season, if the instability becomes symptomatic, the athlete will risk losing two seasons, which essentially ends competitive participation, especially for the high-level athlete.

The traditional open Bankart repair is the standard of care for open stabilization procedures with a recurrence rate of less than 5%. Recurrence after arthroscopic stabilization procedures has been highly variable, with early reports suggesting recurrence rates anywhere from 0 to 45%. The higher failure rates are likely the result of poor surgical technique and an accelerated rehabilitation program that ignored the normal biology of tissue repair, which is the same for both operative procedures. Recent literature has shown a recurrence rate of 8 to 17% after arthroscopic Bankart repairs, which is related to better surgical technique and more traditional postoperative rehabilitation. The advantages of arthroscopic stabilization procedures include cosmetic incisions, less postoperative pain, and earlier recovery of external rotation.

The operative technique chosen depends on which technique the surgeon is most comfortable with. Like arthroscopic rotator cuff repairs, arthroscopic stabilization procedures are technically more challenging and require a clear understanding of the pathoanatomy. Rehabilitation after stabilization procedures is detailed on p. 203. The rehabilitation program is essentially the same for open and arthroscopic techniques because the biology of healing tissue is the same, and the consideration of subscapularis tendon healing is contained within the time-frame of healing for the GH capsulolabral complex.

Complications after Shoulder Stabilization Surgery
Numerous complications may develop after shoulder stabilization surgery for instability and may include:

Limitation of motion.

Recurrent instability.

Inability to return to preinjury level of play in sport.

Development of osteoarthritis.
The most common complication after shoulder stabilization surgery is loss of motion (especially external rotation).
For these reasons, the goals of rehabilitation after shoulder stabilization are:
1.       Maintenance of the integrity of the surgically correct stability.
2.       Gradual restoration of full functional ROM.
3.       Enhancement of dynamic stability (of muscles surrounding shoulder).
4.       Return to full unrestricted activity and sport.

Posterior Shoulder Instability
Posterior instability is much less common than anterior instability. Posterior dislocations are most commonly caused by a generalized muscle contraction after a seizure, which can be related to epilepsy, alcohol abuse, or severe electric shock. Patients with a posterior shoulder dislocation hold the arm in adduction and internal rotation. A fullness may be palpable in the posterior shoulder, and abduction and external rotation may be limited. A complete radiographic evaluation of the shoulder is required, especially an axillary lateral view. If an axillary lateral radiograph cannot be obtained, a CT scan of the GH joint should be done. In approximately 80% of patients with posterior dislocation of the GH joint, the diagnosis is not made by the initial treating physician because of incomplete radiographic evaluation. This is why all shoulder injuries must have an axillary lateral view as part of the radiograph series.

Posterior instability in athletes commonly results in subluxation, usually because of repetitive microtrauma. For example, an offensive lineman in football may develop this condition because of the forward-flexed and internally rotated shoulder position needed for blocking. On physical examination, patients with posterior instability demonstrate increased posterior translation on posterior draw testing. Symptoms are reproduced when a posteriorly directed force is placed on the patient’s arm in the adducted forward-flexed position.

Treatment of Traumatic Posterior Dislocation
Treatment of a traumatic posterior dislocation that is successfully reduced usually begins with immobilization in a brace that maintains the shoulder in external rotation and neutral to slight extension. Immobilization is continued for 6 weeks, and then a structured rehabilitation program is followed similar to the one outlined on page 210. Variations may be required depending on the position of immobilization, positions for recurrent instability, freedom of full external rotation, and restriction of internal rotation.
The basic premise of treating an unstable shoulder with physical therapy is to strengthen the dynamic stabilizers (muscles and tendons) while the static stabilizers (including the glenoid labrum) heal.
Indications for surgical stabilization of a posterior shoulder dislocation include:

A displaced lesser tuberosity fracture.

A posterior glenoid rim fracture of more than 25%.

An impaction fracture of the anterior-superior humeral articular surface (reverse Hill-Sachs lesion) of more than 40%.

An irreducible dislocation.

Recurrent posterior dislocations.

An unstable reduction (usually associated with a reverse Hill-Sachs lesion of 20 to 40%).

Patients with unstable reductions may have pathology similar to that after an anterior dislocation, with avulsion of the capsule and labrum from the posterior glenoid rim. This can be repaired with an open or arthroscopic technique. The rehabilitation protocol after surgical repair of the capsulolabral complex after posterior dislocation is outlined on page 212.

Patients who have symptomatic posterior instability with no history of a traumatic dislocation usually benefit from a rehabilitation program that focuses on strengthening of the dynamic stabilizers. Patients who do not improve after following an organized rehabilitation program for 3 to 6 months may require surgical treatment. These patients usually have a lax posterior capsule, which can be treated with an arthroscopic technique (capsular suture plication, electrothermal capsulorrhaphy [shrinkage]) followed by rehabilitation as outlined on page 211 or with an open posterior stabilization procedure followed by rehabilitation as outlined on page 212.

Multidirectional Instability
Multidirectional shoulder instability is not the result of a traumatic injury, but is associated with hyperlaxity of the GH joint capsule in association with rotator cuff weakness. Multidirectional shoulder instability can be simply defined as symptomatic instability in more than one direction. Patients may have a history of laxity in other joints, demonstrated by frequent ankle sprains or recurrent patellar dislocations. Physical examination often finds generalized joint laxity, but the key to the diagnosis is the reproduction of symptoms with unwanted GH joint translation. Patients demonstrate increased laxity in multiple directions and have a positive sulcus sign or varying degrees of inferior translation of the GH joint.

Treatment
Multidirectional instability is treated conservatively with a rehabilitation program focused on strengthening of the rotator cuff, the scapular stabilizers, and the deltoid muscles. Surgical stabilization is considered if an extensive trial of rehabilitation for at least 6 months fails to relieve symptoms. If conservative treatment fails, an open inferior capsular shift from an anterior approach is recommended. The goal of this procedure is to balance tension on all sides of the GH joint and surgically reduce capsular volume. The postoperative rehabilitation protocol is outlined on this page. Arthroscopic treatment for multidirectional instability is currently evolving. Two techniques for reducing capsular volume with promising results are suture capsular plication and electrothermal capsulorrhaphy (shrinkage). The postoperative rehabilitation protocol is outlined on page 217.

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