Injuries to the shoulder in athletes.

The shoulder is a very complex structure. Although we generally focus on the glenohumeral joint when evaluating the shoulder, we should not forget that the shoulder girdle is composed of the sternoclavicular joint, the clavicle, the acromioclavicular joint, the glenohumeral joint, the scapula, and the scapulothoracic joint. These articulations must work in concert in order for the shoulder to function effectively, with a high degree of freedom and a satisfactory level of stability. Any alterations in the anatomy or function of any of these structures could significantly alter the mechanics of the shoulder as a whole, leading to injury.

When focusing on the shoulder in athletes, especially those engaged in overhead sports such as baseball, softball, tennis, volleyball, and swimming, we must understand that the shoulder is often subjected to great stresses over prolonged periods of time. These stresses often lead to injuries within the soft tissues of the shoulder, such as the rotator cuff and capsule of the glenohumeral joint. These overuse injuries have become quite commonplace, and are frequent problems seen in clinics across the country.

Over the last several decades, our understanding of the shoulder has increased dramatically. Technological advances in imaging and arthroscopy have paved the way for our ever-improving knowledge of the shoulder. Despite these recent advances, the shoulder remains a difficult challenge in diagnosis and treatment within the medical community. In this article, we briefly review anatomy, function, and injuries of the shoulder girdle, and present the newest information on diagnosis and treatment of the more common shoulder injuries found in sports.

Anatomy, Function and Pathophysiology of the Shoulder Girdle

The sternoclavicular joint is formed by the articulation of the medial end of the clavicle with the sternum (Fig. 1). Although it is generally considered a static articulation, this joint allows approximately 40[degrees] rotation along its long axis and 40[degrees] translation in the coronal and axial planes. (1) Traumatic dislocations, either anterior or posterior, are the most common injuries seen at this joint. Anterior dislocations can usually be treated with observation. Posterior dislocations, which fortunately are less common than anterior dislocations, are much more problematic due to the potential for compression of the large neurovascular structures just posterior to this joint. These injuries are treated with a prompt closed or open reduction, often under general anesthesia, with the availability of a general or thoracic surgeon in the event of injury to the neurovascular structures. As a caveat, the medial clavicle epiphysis is the last epiphysis to close, usually around 25 years of age. Therefore, many supposed sternoclavicular joint dislocations are, in fact, physeal plate fractures. (2)

The clavicle is a bony strut connecting the trunk via the sternum to the remainder of the shoulder girdle and upper extremity (Fig. 1). In addition to its support role, it also functions to protect the brachial plexus, subclavian and axillary vessels, and the superior lung. The middle third of the clavicle is the most common location for fractures. The vast majority of these fractures can be treated with a sling or figure-of-eight sling. Indications for operative intervention for mid-third clavicle fractures include severe displacement, open fractures, compromise of the skin, neurovascular injuries, and nonunions. Fractures of the middle and distal thirds of the clavicle can be complicated, and more commonly require operative intervention. (3)

Acromioclavicular joint

The articulation of the distal end of the clavicle with the acromial process of the scapula forms the acromioclavicular (AC) joint (Fig. 1). This joint is surrounded by thick ligaments, the acromioclavicular ligaments, which provide horizontal stability to this joint. Vertical stability is provided by the two coracoclavicular ligaments, the conoid and trapezoid ligaments (Figs. 1 and 2). These two ligaments extend from the inferior surface of the distal third of the clavicle to the coracoid process of the scapula and, in effect, function to support the upper extremity to the clavicle and trunk.

Acromioclavicular dislocations, also known as shoulder separations, are common injuries and are classified into six types (Fig. 3). In AC injury types I and II, the acromioclavicular ligaments are sprained or torn, but the coracoclavicular ligaments are intact. As a result, the AC joint is not significantly disrupted on radiographs. Treatment of these injuries is initial rest, ice, and gentle range of motion exercises, followed by more aggressive range of motion and strengthening exercises as symptoms decrease. Athletes can usually return from these injuries within 2 to 6 weeks.

[FIGURE 1 OMITTED]

A type III injury occurs when both the acromioclavicular and coracoclavicular ligaments are torn. On radiographs, the distal end of the clavicle is displaced above the superior border of the acromion. Although the displacement of the AC joint appears to be secondary to superior migration of the clavicle, in fact, the downward sag of the upper extremity including the scapula and acromial process is responsible for this finding. Treatment of these injuries is controversial, but, in general, these injuries are treated nonoperatively in inactive, nonlaboring, or recreational athletes, especially if the injury is to the nondominant shoulder. Operative intervention is considered in heavy laborers and young, athletic patients.

Type V AC dislocations are similar to type III injuries, with the difference being a more severe displacement of the clavicle in relation to the acromion. These injuries are treated operatively. Type IV and type VI AC joint injuries are extremely rare and require operative intervention. (4)

Glenohumoral joint

The glenohumeral joint is the articulation of the humeral head with the small, flat glenoid fossa of the scapula. This articulation is the source of numerous injuries in athletes, especially overhead athletes. In order for the shoulder to function effectively, it must be allowed to undergo extremes in range of motion. This is possible because there exists very little bony congruity between the humeral head and glenoid. The tradeoff to this freedom of motion is that the glenohumeral joint largely relies on soft tissues to provide stability. These soft tissues are subjected to great stresses as they attempt to hold the humeral head against the glenoid while the humeral head is being rotated through these extreme ranges of motion. It is these soft tissues that are the source of injury in the athlete's shoulder.

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The stability of the glenohumeral joint is both static and dynamic. The static stabilizers include the joint surfaces, the negative intraarticular pressure, and the capsulolabral complex, which is formed by the fibrocartilagenous labrum that surrounds the periphery of the glenoid, and the glenohumeral ligaments (Fig. 2). There are three primary glenohumeral ligaments, the superior, middle, and inferior. The inferior ligament is divided into an anterior and posterior band. The anterior band of the inferior glenohumeral ligament is the most important static stabilizer, and is most commonly injured with anterior shoulder dislocations.

[FIGURE 3 OMITTED]

The dynamic stabilizers of the glenohumeral joint include the rotator cuff muscles and the scapular rotator muscles. The rotator cuff muscles are the subscapularis, supraspinatus, infraspinatus, and teres minor (Fig. 2). The scapular rotator muscles are the levator scapulae, trapezius, rhomboids, and serratus anterior. These latter muscles position the bony glenoid in concert with the humeral head to insure that the bony articulations and muscle actions of the shoulder girdle are optimized to provide stability to the glenohumeral joint.

Scapulothoracic articulation

The scapulothoracic articulation plays a crucial role in the stability and mobility of the shoulder, especially the glenohumeral joint, as it directly affects the position of the glenoid. Any malfunction of the scapular stabilizing muscles can disrupt the articulation of the glenoid with the humeral head, leading to a loss of stability or mobility. Such pathology can also affect the functioning of the dynamic stabilizers of the glenohumeral joint, leading to asynchronous muscle actions, which may also lead to a loss of stability or mobility of the glenohumeral joint. Any abnormality in the normal position or motion of the scapula during coupled scapulohumeral movements is termed scapular dyskinesis. (5) Scapular dyskinesis has been linked to numerous injury patterns around the shoulder, including acromioclavicular joint pain, subacromial impingement syndrome, glenohumeral instability, and rotator cuff pathology. Scapular dyskinesis must be considered when evaluating these injuries. Often, these injuries can be managed effectively with nonoperative treatment. One of the mainstays of nonoperative treatment around the shoulder is physical therapy. One of the major goals of physical therapy is to assess and treat any abnormalities in scapular motion or position. If dysfunction of scapulohumeral motion is identified, physical therapy can often help restore normal shoulder function, thereby alleviating the source of symptoms.

Of the numerous injuries to the shoulder incurred in athletics, rotator cuff injuries and glenohumeral instability are extremely common. In the following section, we will explore these two subjects in more detail.

Rotator Cuff Injuries

Although traumatic ruptures of the rotator cuff tendons do occur in athletes, the most common cause for injury to the rotator cuff within this population is chronic overuse, especially in those individuals engaged in overhead athletics. We shall use the baseball throw as an example of the injuries seen in overhead athletes (Fig. 4). The primary function of the rotator cuff muscles is to stabilize the humeral head within the glenoid. This can be an extremely difficult task. When a baseball pitcher throws a baseball, huge forces are created at the glenohumeral joint. These forces function to translate the humeral head anteriorly on the glenoid with a magnitude of one's own body weight. The anterior capsular tissues provide a static resistance to this anterior translation; whereas the rotator cuff muscles provide dynamic resistance. As a pitcher repetitively throws over the course of a baseball season, the rotator cuff muscles become fatigued. This leads to tendonitis of the rotator cuff muscle tendons. If a pitcher continues to throw with this injury, not allowing proper rest time for these tissues to heal, chronic injury to the tendons may occur. Further stresses to the rotator cuff complex lead to partial-thickness rotator cuff tears, and possibly full-thickness tears. These injuries are further accentuated by any congenital or acquired instability of the glenohumeral joint, as these static and dynamic restraints must work harder to stabilize the humeral head within the glenoid. Athletes will often attempt to compensate for the malfunction of their rotator cuff by altering their pitching mechanics. This leads to scapula dyskinesis, which further affects the function of the rotator cuff. This cycle of chronic overuse injury to the rotator cuff is extremely common in baseball, but also is seen in softball players, swimmers, volleyball players, tennis players, javelin throwers, and other overhead athletes (Fig. 5). (6)

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The vast majority of rotator cuff injuries can be treated nonoperatively. At the initial examination, it is important to make certain the athlete does not have a significant partial-thickness rotator cuff tear or full-thickness tear. These may require more aggressive treatment. In most instances, athletes with rotator cuff tendonitis or tendonosis, or a small partial-thickness rotator cuff tear will have normal or near-normal strength with abduction, internal rotation, and external rotation of the shoulder. If significant weakness is found with these exams, a more severe tear of the rotator cuff must be considered.

[FIGURE 5 OMITTED]

Nonoperative treatment for rotator cuff pathology consists of a period of active rest, antiinflammatory medication, physical therapy, and occasionally subacromial injections with corticosteroids. If an athlete fails a prolonged period of nonoperative treatment, surgical intervention may be warranted in the form of a diagnostic arthroscopy. Various techniques are being developed for treatment of partial-thickness rotator cuff tears, including debridement of these tears (as opposed to attempted repair for more severe lesions). For full-thickness rotator cuff tears, debate exists as to which is the most effective technique for repair of these injuries, either arthroscopic or open.

Open or mini-open repair of rotator cuff tears has traditionally been the standard of care for these injuries; however, over the last several years, arthroscopic repairs have become extremely popular. A traditional open rotator cuff repair requires a large split of the deltoid muscle to allow access to the injured rotator cuff. A mini-open repair also requires a split in the deltoid muscle to access the injured rotator cuff, although this split is much less than in traditional techniques. The violation of the deltoid muscle with these techniques can lengthen the rehabilitation period and produce more pain following a rotator cuff repair surgery. Arthroscopic techniques require only puncture holes within the deltoid muscle. As compared to open rotator cuff repairs, arthroscopic repairs usually result in less injury to the deltoid muscle, less post-operative pain, and more rapid rehabilitation. These arthroscopic techniques, however, can be extremely technically demanding, and require a certain proficiency with performing complex arthroscopic techniques. Although more biome-chanical and clinical outcome studies are needed to evaluate the short- and long-term differences between open and arthroscopic rotator cuff repairs, recent literature suggests that arthroscopic techniques can provide good outcomes in select patients with rotator cuff tears. (7,8) In the future, most rotator cuff repairs will likely be done with minimally invasive arthroscopy, as orthopaedic surgeons become more familiar with these techniques. (9)

Glenohumeral Instability

The causes of glenohumeral joint instability have traditionally been classified into traumatic, atraumatic, or acquired via repetitive microtrauma. Traumatic instability results from acute injury to the capsulolabral tissues, usually leading to a unidirectional pattern of laxity. The classic example is a football player who sustains an anterior shoulder dislocation. Atraumatic instability occurs secondary to congenitally lax glenohumeral capsular tissues, leading to a pattern of multidirectional laxity. The classic example is a teenage girl with bilateral shoulder pain, "loose" shoulders and generalized ligamentous laxity. Acquired instability usually occurs in overhead athletes as they repetitively stretch the glenohumeral capsular tissues leading to laxity of the glenohumeral joint over time. The classic example is a professional baseball player with pain of his throwing shoulder only in the cocking phase of the pitch, with subtle anterior shoulder laxity. Although it is convenient to separate these mechanisms of instability into distinct entities, in reality there is often significant overlap among these groups, and the most effective treatment will depend on determining the exact nature of the instability.

Arthroscopic versus open surgical management. Just as there is debate regarding the best method of surgical fixation of full-thickness rotator cuff tears, debate exists as to whether or not instability is best managed with arthroscopic or open techniques. The gold standard for treatment of traumatic anterior shoulder instability is an open procedure called a Bankart procedure. A Bankart lesion is a soft tissue avulsion of the anterior-inferior glenoid labrum, or bony fracture of the anterior-inferior glenoid rim secondary to a traumatic anterior shoulder dislocation. This technique requires a fairly extensive exposure of the anterior shoulder, leading to trauma of the soft tissues.

Over the last several years, arthroscopic stabilization of athletes with traumatic anterior shoulder instability has become more commonplace, especially with acute injuries. As with arthroscopic rotator cuff repairs, this technique is associated with less surgical trauma to the soft tissues around the shoulder. As a result, patients have less postoperative pain, improved cosmesis, and possibly improved ranges of motion of the shoulder. Although the initial results of this procedure showed poorer results than open stabilization, advances in patient selection, implant technology, arthroscopic techniques, and postoperative rehabilitation will most likely lead to improving results with arthroscopic intervention for these injuries. Regardless of surgical technique, orthopaedic surgeons have become more aggressive in treating traumatic shoulder instability surgically, especially in the younger population. Numerous studies have documented a high rate of recurrent shoulder dislocations following a traumatic dislocation in younger athletes. Early surgical intervention has been shown to significantly lessen the risk of recurrent dislocations in this population. (10) It is important for orthopaedic surgeons to be involved in the care of patients with traumatic shoulder instability early so that all of the options can be discussed, and the proper treatment protocol recommended.

Atraumatic multidirectional instability can be difficult to manage effectively. Prolonged physical therapy remains the mainstay of treatment for individuals with this diagnosis. For those patients who have failed nonoperative treatment, surgical intervention may be warranted. The gold standard for treatment of these patients has been an open anterior capsular shift, in which the capsular tissues are sutured upon themselves in a tightened configuration. Arthroscopic techniques are becoming more popular for treatment of patients with multidirectional instability.

Thermal capsulorrhaphy. Thermal capsulorrhaphy is one such technique that has been used to stabilize shoulders with multidirectional instability. In this technique, heat is applied to the capsular tissues that are lax around the glenohumeral joint. The heat destabilizes the collagen molecules that give these capsular tissues their stiffness, resulting in an abnormal, disordered arrangement of these molecules. In theory, tissues heal from this thermal insult with more stiffness secondary to the reformation of bonds between the collagen molecules. In effect, the capsular tissues shrink, thereby decreasing the volume of the joint capsule, and increasing the stability of the glenohumeral joint. Although this initially appeared to be a promising technique to deal with the very difficult problem of multidirectional instability, the results have been quite variable. More studies are needed to evaluate the true effects of thermal energy on the shoulder. (11)

Capsular plication. The more recent arthroscopic techniques designed to treat multidirectional instability are focused on capsular plication. This technique involves placing sutures in the capsular tissues of the glenohumeral joint to decrease the laxity of these capsular tissues. The ultimate efficacy of this surgical technique will need to be evaluated in clinical studies.

Acquired instability. Acquired instability occurs secondary to repetitive stresses placed upon the capsular tissues of the glenohumeral joint, leading to stretching of these tissues by way of microtrauma. This instability is primarily found in overhead athletes who complain of pain during their overhead activity. The physical exam in these patients may often reveal little in the way of distinct pathological laxity of the glenohumeral joint. Thus, this instability pattern is usually a dynamic process. Only during the stresses of the overhead sport will the forces be large enough to produce the abnormal glenohumeral motion.

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Acquired instability is often seen in concert with other glenohumeral pathology, including labral tears, superior labrum anterior and posterior (SLAP) lesions, internal impingement, and undersurface rotator cuff tears. SLAP lesions are tears of the superior labrum-biceps tendon complex (Fig. 6). (12) These may occur secondary to repetitive stress to these tissues, as with baseball pitching, or a distinct trauma (ie, a baseball player diving for a ball and landing on an outstretched arm). Internal impingement has, over the past decade, been identified as a source of pain in overhead athletes. It involves a partial undersurface tear of the rotator cuff secondary to the rotator cuff being compressed against the posterior glenoid and labrum (Fig. 7). (13) Both SLAP lesions and internal impingement have been associated with acquired instability, although the exact relationship is still being investigated.

The initial treatment of athletes suspected of having acquired instability is a period of active rest, anti-inflammatory medication, and physical therapy. Physical therapy is critical to improve the strength of the rotator cuff and scapular kinetics. If an athlete fails nonoperative treatment, an examination under anesthesia followed by a diagnostic arthroscopy is warranted. Any intraarticular pathology is addressed, such as a partial undersurface rotator cuff tear or SLAP lesion. The nature of the instability is then addressed. At this time surgical options to limit the pathologic glenohumeral motion of acquired instability include thermal capsulorrhaphy and capsular plication.

Conclusion

Shoulder injuries are very common in athletes both young and old at all levels of competition. Often the diagnosis and treatment of shoulder injuries can be difficult, especially in athletes engaged in repetitive overhead activities. Although the vast majority of overuse injuries to the shoulder can be treated nonoperatively--emphasizing rest from a particular sport and physical therapy--surgical intervention may be necessary. Arthroscopy has clearly proven to be beneficial in the diagnosis and treatment of shoulder injuries. Although many arthroscopic techniques have become mainstream, others remain unproven. Yet it is certain that arthroscopic techniques will continue to evolve as our ever-changing understanding of the complexity of the shoulder joint evolves.

When a man sits with a pretty girl for an hour, it seems like a minute.
But let him sit on a hot stove for a minute--and it's longer than any
hour. That's relativity.
--Albert Einstein

Accepted May 21, 2004.

References

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10. Stein DA, Jazrawi LM, Rosen JE et al. Arthroscopic stabilization of anterior shoulder instability: a historical perspective. Bull Hosp Jt Dis 2001;60:124-129.

11. Anderson K, Warren R, Altchek DW, et al. Risk factors for early failure after thermal capsulorrhaphy. Am J Sports Med 2002;30:XXX-XXX.

12. Snyder SJ, Karzel RP, Del Pizzo W, et al. SLAP lesions of the shoulder. Arthroscopy 1990;6:274-279.

13. Walch G, Boileau P, Noel E, et al. Impingement of the deep surface of the supraspinatus tendon on the posterosuperior glenoid rim: an arthroscopic study. J Shoulder Elbow Surg 1992;1:238-245.

Christopher G. Mazoue, MD, and James R. Andrews, MD

From the Department of Orthopaedic Surgery, University of South Carolina School of Medicine, Columbia, SC, and the Alabama Sports Medicine Institute, Birmingham, AL.

Reprint requests to Christopher Mazoue, MD, Two Medical Park, Suite 404, Columbia, SC 29203.