Essentials of Orthopedic Surgery, third edition / 08-The Shoulder

334 R.M. Carroll

FIGURE 8-1. Anterior view of the shoulder demonstrates the skeletal anatomy and two of the four articulations, the glenohumeral and acromioclavicular joints.

are responsible for maintaining joint stability and congruity while allowing a tremendous range of motion. These soft tissue stabilizers include the joint capsule, glenohumeral ligaments, glenoid labrum, long head of the biceps tendon, and the rotator cuff musculature. The burden placed upon these soft tissues leads to the majority of degenerative and traumatic conditions affecting the shoulder girdle.

The Glenohumeral Ligaments

The capsule of the shoulder is a specialized structure that contains distinct thickenings referred to as ligaments (Fig. 8-2). The glenohumeral ligaments are named for their origin from the glenoid rim. This ligamentous complex includes the superior glenohumeral ligament (SGHL), the middle glenohumeral ligament (MGHL), the anterior band of the inferior glenohumeral ligament (AIGHL), and the posterior band of the inferior glenohumeral ligament (PIGHL). These ligaments function as static stabilizers of the glenohumeral joint. The SGHL is the primary restraint to inferior translation and external rotation with the arm in adduction. The MGHL is the primary

336 R.M. Carroll

The Labrum

The labrum is a fibrous structure of variable anatomy that attaches to the rim of the glenoid cartilage through a fibrocartilaginous zone, increasing the depth of the glenoid concavity by 50%. The labrum functions to increase the surface contact area with the humeral head; to act as a static stabilizer through a buttress effect; and to serve as an attachment site for the shoulder capsule, glenohumeral ligaments, and long head of the biceps tendon. The labrum has a variable cross-sectional anatomy, the superior aspect of the labrum being more triangular shaped and well defined and the inferior aspect of the labrum more rounded and less distinct. Common anatomic variations include a sublabral hole (foramen) or an absent labrum in the anterosuperior quadrant of the glenoid. The combination of a cordlike MGHL and absent anterosuperior labrum has been termed a Buford complex. Additionally, the labrum may attach directly to the rim of the surface of the glenoid cartilage or it may have a reflected, or meniscal-type, attachment.

The Rotator Interval

The rotator interval is the triangular region between the superior aspect of the subscapularis tendon and the anterior aspect of the supraspinatus tendon whose base is the coracoid. The rotator interval includes a number of fibrous structures including the coracohumeral ligament, the SGHL, and the transverse humeral ligament. The coracohumeral ligament (CHL) is the most significant structure in the rotator interval and is extraarticular. It originates from the lateral base of the coracoid, fanning out to envelop the supraspinatus tendon inserting on the greater tuberosity and to envelop the subscapularis tendon inserting on the lesser tuberosity. The CHL is a primary restraint to inferior translation and external rotation in the adducted arm. The transverse humeral ligament forms the apex of the rotator interval and contributes to the superior soft tissue sling that stabilizes the long head of the biceps tendon as it passes through the interval to enter (or exit) the glenohumeral joint.

The Long Head of the Biceps Tendon

The long head of the biceps tendon (LHBT) remains somewhat enigmatic with respect to its function in the shoulder girdle, but it is nonetheless a potential source of pain and disability. The long head of the biceps enters/ exits the glenohumeral joint at the rotator interval by way of the bicipital groove and is an intraarticular structure. The LHBT originates from the superior glenoid tubercle and blends with the fibers of the superior labrum. This intimate relationship of the LGBT with the superior labrum is a significant source of morbidity in the throwing athlete. Although there are

conflicting data, the long head of the biceps is thought to be a humeral head depressor and may contribute to glenohumeral instability. Potentially more relevant is the theory of the “peel-back” mechanism of superior labral tears or SLAP (superior labrum anteroposterior) tears. This theory suggests that the LHBT and superior labrum detach from the superior glenoid in the late cocking position of a baseball pitch as the LHBT becomes taut and “peels back” the superior labrum off the glenoid rim. Whether or not this theory is correct, SLAP tears can be a significant problem in the throwing athlete. Tendonitis of the LHBT is also a common source of morbidity in the shoulder and is often a component of the impingement syndrome.

The Rotator Cuff

The rotator cuff consists of four muscle–tendon units including the subscapularis, supraspinatus, infraspinatus, and teres minor. These muscles originate on the scapula and insert onto the tuberosities of the proximal humerus. The subscapularis originates on the anterior surface of the scapula and inserts onto the lesser tuberosity. The remaining rotator cuff muscles originate from the posterior surface of the scapula and insert along the greater tuberosity. The roles of the rotator cuff are to keep the humeral head centered in the glenoid fossa throughout the range of shoulder motion and to contribute to the rotation and elevation of the extremity. As such, the rotator cuff is the primary dynamic stabilizer of the glenohumeral joint. Traumatic and overuse injuries to the rotator cuff are the most common problems in the shoulder girdle.

The Subacromial Space

The subacromial space is a potential space beneath the acromion and above the rotator cuff. The subacromial bursa outlines the subacromial space and provides frictionless gliding of the rotator cuff beneath the acromion and coracoacromial arch. Bony osteophytes on the undersurface of the anterior acromion have been postulated to narrow the subacromial space, irritate the subacromial bursa, and contribute to rotator cuff tears.

The Acromioclavicular Joint

The acromioclavicular (AC) joint is a true diarthrodial joint containing a fibrocartilaginous disk. The AC joint helps link the appendicular skeleton with the axial skeleton through the clavicle. Because there is little intrinsic bony stability to the AC joint, a number of ligaments and other soft tissues serve to stabilize this articulation (Fig. 8-3). The superior AC ligament is the most important horizontal stabilizer. The coracoclavicular (CC) ligaments, consisting of the conoid ligament (medial) and the trapezoid

FIGURE 8-3. In this anterior view, note the acromioclavicular joint surrounded by the capsule (acromioclavicular ligament), in addition to the supporting coracoclavicular ligaments, the conoid and trapezoid. (From Rockwood CA Jr, Matsen FA III (eds) The Shoulder, vol 1. Philadelphia: Saunders, 1990. Reprinted by permission.)

ligament (lateral), provide the primary restraint to vertical displacement of the clavicle. A significant amount of rotation occurs in the clavicle throughout the arc of elevation of the upper extremity. Approximately 10% of this rotation occurs at the acromioclavicular joint.

The Sternoclavicular Joint

The sternoclavicular (SC) joint is the only bony connection between the upper appendicular skeleton and the axial skeleton and has the least bony stability of any major joint. The majority of clavicular rotation occurs at the sternoclavicular joint, but less than 50% of the bulbous medial clavicle is in contact with the shallow sternal articular fossa. Thus, the soft tissues provide stability to the sternoclavicular joint. The ligamentous anatomy of the SC joint includes the intraarticular disk ligament, the costoclavicular

340 R.M. Carroll

For example, a high-school athlete with activity-related shoulder pain is more likely to have instability or labral pathology than a rotator cuff tear. Conversely, a 65-year-old who has shoulder pain with activities of daily living is more likely to have rotator cuff disease than a labral tear or instability. The physical examination is used to narrow the differential diagnosis and make the definitive diagnosis. Most of the time an accurate diagnosis can be made using only the history and physical examination. Indiscriminate use of imaging studies and additional testing is not recommended.

Before ordering additional studies, the examiner must have a clear understanding of how the study will contribute to the evaluation and treatment of the patient.

History

Patients with shoulder pathology most often complain of pain, stiffness, instability, and weakness. When pain is the chief complaint, the examiner must characterize the pain, with particular attention to location. Pain from the glenohumeral joint and its surrounding soft tissues typically is localized to the anterosuperior aspect of the shoulder. Localization of the pain to the deltoid insertion in the arm is common in rotator cuff or subacromial pathology. Pain emanating from the neck or to the posterior scapular region is often due to cervical spine disease. Pain and crepitation in the periscapular region, however, may be related to scapulothoracic bursitis.

The timing and frequency of shoulder pain must also be given careful consideration. Activity-related pain can provide valuable clues as to the underlying diagnosis. Pain with overhead activities of daily living is common in rotator cuff pathology. Pain with sporting activities such as swimming, throwing, or serving is often related to the labrum or glenohumeral ligaments. Night pain is often reported with shoulder girdle pathology, especially in the setting of rotator cuff tears. Patients often report the inability to sleep on the affected side. Rest pain is uncommon but may occur with severe arthropathy or radicular pain from the cervical spine. If rest pain is the predominant complaint, the examiner should consider infection or malignancy as a possible source of pain.

The relationship of pain to injury is important to establish. Pain that begins with a traumatic event such as a fall on an outstretched hand, direct blow to the shoulder, or shoulder dislocation may represent significant damage to the rotator cuff, ligaments, or bony structures. Pain that begins days or weeks after a seemingly innocuous event such as shoveling snow; trimming hedges, or painting may represent tendonitis or early capsulitis.

Pain that begins more insidiously or over time is more likely to be related to degenerative lesions of the shoulder girdle such as rotator cuff tears or osteoarthritis.

Complaints of shoulder instability are relatively common. The patient may describe the shoulder “slipping out of place” or “getting stuck” in

extreme positions. It is important to establish whether a frank shoulder dislocation was ever documented. True traumatic shoulder dislocations are the result of significant trauma and require a manipulative reduction. Unfortunately, subsequent dislocations may occur with less trauma. Patients who have shoulders that “slip out of place” and “slide back in” on their own are more likely to have multidirectional instability as opposed to traumatic instability.

Weakness or loss of shoulder function is an infrequent complaint. In the absence of pain, a neurologic origin of the deteriorating function should be considered. Insidious onset of pain with deteriorating function may represent a degenerative condition of the shoulder or adhesive capsulitis.

A careful review of systems is important to document as there are a number of disease processes remote from the shoulder girdle that can result in shoulder pain. Cervical spine pathology, cardiac disease, gallbladder disease, and lung disease (pancoast tumor) can present with shoulder pain. A history of cancer is also important to document because metastatic cancer can present with shoulder pain and lesions in the shoulder girdle.

Functional Assessment

In addition to establishing the history of present illness, it is imperative to establish the functional status of the patient. Important patient factors to note include the handedness (right, left, or ambidextrous) of the patient; the vocation of the patient; extracurricular/sporting activities enjoyed by the patient, and, most importantly, the expectations of the patient with regard to the shoulder problem. Understanding the patient’s functional demands and expectations allows the clinician to prescribe appropriate treatment regimens and to provide reasonable expectations for functional recovery.

Inspection

The physical examination begins with inspection of the shoulder girdle. The region must be adequately exposed for the examination. The inspection begins with assessment of symmetry between the involved and uninvolved shoulder girdles. Gross deformity such as distal clavicle prominence in an AC separation, prior surgical incisions, skin discoloration, or open wounds are readily appreciated. A more subtle finding is muscle atrophy, which may be the result of disuse or injury. Patients with long-standing rotator cuff tears often have atrophy of the supraspinatus and infraspinatus fossae, resulting in prominence of the spine of the scapula. Traumatic injuries can produce subtle deformities. In the setting of an anterior dislocation, the anterior aspect of the shoulder may appear “full” and the posterior aspect may lose its normal contour, making the posterior acromion

342 R.M. Carroll

appear more prominent. Inspection should continue through the entire exam as some deformities such as scapular winging may only be revealed during provocative testing.

Palpation

The primary importance of palpation is to localize the source of pain. Palpation of bony prominences and superficial joints yields the most information. In the absence of trauma, palpation includes the SC joint, AC joint, the greater and lesser tuberosities, and the intertubercular or bicipital groove. Tenderness on palpation at any of these sites can be a valuable clue in making a diagnosis. When the presenting complaint is neck or periscapular pain, palpation of the posterior elements of the cervical spine and bony elements of the scapula is warranted. In the setting of trauma, palpation of all bony structures and areas of deformity is critical to localize the zone of injury.

Range of Motion

The evaluation of range of motion is straightforward. The examiner directs the motions and observes for symmetry. The standard motions include forward elevation, external rotation, internal rotation, and abduction. Forward elevation occurs in the plane of the scapula and is a combination of scapulothoracic and glenohumeral motion. Loss of glenohumeral motion can lead to scapulothoracic substitution and scapular winging. External rotation is evaluated with the arms at the side to prevent scapulothoracic contribution to rotation. Internal rotation is evaluated by having the patient place his hands as high as possible along the midline of the back. Internal rotation is graded by the approximate vertebral level the patient is able to reach. Assessment of abduction, including internal and external rotation in abduction, is critical for unmasking subtle losses of motion. Baseball pitchers often lose some internal rotation in abduction while gaining external rotation in abduction in their throwing arm. There is no net loss of motion, only a resetting of the range of motion relative to the nonthrowing shoulder.

When loss of active motion is identified, the examiner must assess the passive range of motion. If there is loss of active and passive motion, there is likely a soft tissue contracture or a physical block to motion (dislocation, loose body, or osteophyte). In the absence of trauma, loss of both active and passive motion usually represents adhesive capsulitis (frozen shoulder) or arthropathy. If there is loss of active motion with preserved passive motion, the examiner must consider tendon (rotator cuff) rupture or, potentially, nerve damage. When examining the rotator cuff muscles, the examiner must appreciate lag signs.