Rotator Cuff and Impingement Lesions

Historical Perspective

A description of rotator cuff pathology is found in the earliest surgical text, the Edwin Smith Papyrus (c.1500 bce ). Subsequently, throughout ancient and modern history, multiple authors have written about the rotator cuff, its disease, and its nonoperative and operative treatment. Monro penned the first modern case report and illustration of a rotator cuff tear in 1788 in his treatise, A Description of All the Bursae Mucosae of the Human Body . John Gregory Smith reported the first cases series of seven rotator cuff tears in a letter to the editor of the London Medical Gazette , and Muller described a rotator cuff repair in 1889. However, it was the publication of Ernest Amory Codman's landmark book, The Shoulder , in 1934 that ushered the rotator cuff, its pathology, and its treatment into mainstream medical discourse and consciousness. Codman was a Boston general surgeon who dedicated a tremendous amount of his energy, talent, skill, and clinical practice to the study of the shoulder and its maladies. The foundation of contemporary care of rotator cuff disease—and arguably the care of surgical patients in general—can be traced to the principles described in this book. Although Codman's book and the works of other authors have shed light on the subject, many questions regarding the care of the rotator cuff remain, and nowhere is this more relevant than in the rotator cuff of the athlete.

The years following the publication of Codman's book saw a rapid proliferation of active study of the shoulder by authors such as Harrison McLaughlin, Carter Rowe, and Charles Neer. The pioneering work of Charles Neer set the stage for the contemporary discussion and debate of how to best care for the rotator cuff. Neer expanded on the concept of outlet impingement first elucidated by Meyer in 1937. Neer vigorously investigated subacromial outlet impingement and argued that impingement was the basis of a spectrum of disease, encompassing most disorders involving the rotator cuff.

Neer proposed three stages of impingement. Initially, in stage I, there is inflammation and edema within the cuff. This is followed by the fibrosis and tendinitis seen in stage II. Finally, there is partial or complete tearing of the rotator cuff in stage III. Neer eventually came to argue that a vast majority, if not all, lesions of the rotator cuff were due to subacromial impingement. This argument generated vigorous and vocal opposition from other surgeons who argued that the etiology of rotator cuff disease is more degenerative in nature. The debate of extrinsic impingement versus intrinsic degeneration as the etiology of rotator cuff tears continues to this day. In reality, rotator cuff tears are likely the result of a multifactorial combination of these two sources.

Anatomy

The glenohumeral joint is the most mobile in the body, allowing for precise positioning of the hand in space. The glenohumeral joint also acts as a fulcrum for the upper extremity, absorbing the majority of forces in activities that require propulsive action. Vitally linked to these motions in terms of precision, propulsion, and stability is the rotator cuff. The cuff is composed of the confluent tendons of the supraspinatus, infraspinatus, subscapularis, and teres minor muscles, which originate from the anterior and posterior aspects of the scapula and insert as a composite onto the greater and lesser tuberosities of the humerus. The cuff envelops and blends with the glenohumeral capsule on all sides except at the redundant inferior pouch.

The biceps tendon originates at the supraglenoid tubercle and traverses the glenohumeral joint as an intra-articular but extrasynovial structure. The biceps passes deep to the interval between the supraspinatus and subscapularis (the “rotator interval”) and exits the joint in the intertubercular sulcus, which is bound by the coracohumeral (CH) ligament superiorly and the confluence of the superior tendinous slip of the subscapularis and superior glenohumeral ligament (SGHL) inferiorly. These ligaments, along with the tendinous slip of the subscapularis, form a pulley for the biceps tendon as it enters the intertubercular groove. The groove has a variable shape and depth, and the bony anatomy of the supratubercular region has been implicated in degenerative lesions of the biceps tendon.

The rotator interval is an anatomic space defined by the inferior edge of the supraspinatus tendon and the superior edge of the subscapularis tendon. The superficial roof of the rotator interval is the CH ligament and the floor of the interval is the SGHL. The biceps tendon occupies this interval as it enters the shoulder joint, with the CH ligament and SGHL forming a pulley for the biceps tendon ( Fig. 47.1 ). The rotator interval functions, biomechanically, as a suspensory structure for the humeral head. Lesions of the rotator interval have been recognized as an important pathology in the genesis of shoulder pain.

The vascular supply of the biceps and rotator cuff has been studied extensively. Anatomic studies have demonstrated that the vascular supply of the rotator cuff comes from six branches of the axillary artery, with the largest contributions arising from the suprascapular and the anterior and posterior humeral circumflex arteries. Previous belief held that there is an area of relatively poor vascularity known as the “critical zone.” This area lies within the supraspinatus tendon immediately proximal to its insertion onto the greater tuberosity, where most degenerative changes and degenerative rotator cuff tearing begin. However, recent intraoperative Doppler flowmetry studies failed to show a critical zone of decreased vascularity in normal supraspinatus tendons, although there is a demonstrated decrease in overall tendon vascularity with increasing age. The biceps tendon also demonstrates an area of hypovascularity in its intra-articular portion related to tension or pressure from the humeral head when the tendon is in the anatomic position. With arm abduction, these areas demonstrate complete vascular filling.

Superficial to the rotator cuff is the deltoid and coracoacromial (CA) arch. The acromion is an extension of the spine of the scapula and has a variable shape and slope that form the posterolateral bony roof of the arch. The acromion serves as the origin of the deltoid laterally and articulates with the clavicle anteriorly and medially, its undersurface creating a finite space for the rotator cuff tendons superior to the humeral head. The CA ligament extends from the outer edge of the coracoid and widens to insert on the anteromedial aspect and undersurface of the acromion. The CA ligament encompasses the anterior extent of the CA arch and, with the anteroinferior edge of the acromion and the coracoid process, is implicated in classical extrinsic impingement of the rotator cuff. Some authors have suggested that the shape and slope of the acromion may be related to extrinsic rotator cuff pathology. However, whether the variability in acromial shape is the result or the cause of the underlying cuff degeneration remains controversial ( Fig. 47.2 ).

Deep to the CA arch lies the subacromial bursa. It is a filmy synovium-lined sac that attaches at its base to the greater tuberosity with its roof fixed to the undersurface of the acromion and CA ligament. The remaining superior and inferior surfaces of the bursa articulate loosely with the deltoid and rotator cuff, respectively. The roof and base of the bursa are separated by a thin interface of synovial fluid that allows relatively frictionless motion between the cuff and the overlying deltoid and CA arch.

Biomechanics

The biomechanics of the shoulder involve a complex interaction between several “joints,” including the scapulothoracic, glenohumeral, acromioclavicular, and sternoclavicular articulations. The most relevant to this topic are the scapulothoracic and glenohumeral articulations.

Rotator Cuff Function

Because the glenohumeral joint lacks inherent bony stability, it relies heavily on both static and dynamic soft tissue stabilizers for its stability and function. The muscles of the rotator cuff contribute to glenohumeral motion. But much more importantly, they help maintain a stable fulcrum at the glenohumeral joint around which the other muscles of the shoulder girdle can effectively act on the humerus.

Although previously believed to initiate abduction, the supraspinatus is currently considered to function primarily as a stabilizer of the glenohumeral joint. Its orientation 70 degrees from the plane of the glenoid means it provides a compressive force driving together the humeral head and the glenoid cavity ( Fig. 47.3 ). By maintaining the articular congruity through concavity compression, a stable fulcrum is created for the more powerful muscles of the shoulder girdle. The powerful deltoid, for example, requires this stability at the glenohumeral joint to function effectively. Without the stabilizing, synergistic action of the supraspinatus the humeral head would displace superiorly as the deltoid contracts, resulting in impingement of the rotator cuff between the humeral head and the undersurface of the acromion.

By virtue of their orientation, the action of the infraspinatus and teres minor muscles is external rotation of the arm and depression of the humeral head, with the infraspinatus being the primary depressor. The subscapularis muscle also depresses the humeral head and acts as an internal rotator of the arm. The infraspinatus and subscapularis act as a “force couple,” stabilizing the glenohumeral joint, especially during eccentric contraction and overhead activity. The rotator cuff provides stability through eccentric contraction, whereas the large superficial muscles around the glenohumeral joint (such as the deltoid, trapezius, latissimus dorsi, and pectoralis major) provide the propulsion for movements of the shoulder by their powerful concentric contractions.

With concentric muscular contraction producing motion in one direction, there is a concomitant eccentric muscular contraction on the opposite side of the joint that produces stability. These eccentric contractions are provided by the muscles of the rotator cuff and point to their essential role in shoulder stability. For example, with external rotation of the arm, the infraspinatus contracts concentrically while the subscapularis shows significant electromyographic (EMG) activity as it contracts eccentrically. In this case, the infraspinatus produces the propulsive power on one side of the joint while the subscapularis produces a counteracting, stabilizing force on the opposite side of the joint. This balance is biomechanically important for fine-tuning the movements in the athlete's shoulder.

Biceps Function

The long head of the biceps, long thought of as a humeral head depressor, is most likely a passive player during most shoulder motions ( Fig. 47.4 ). Yamaguchi and colleagues used electromyography to assess the activity of the long head of the biceps with shoulder-related activity. They controlled elbow function with the use of a brace that locked the elbow at 100 degrees of flexion and neutral forearm rotation. With elbow motion thus eliminated, they demonstrated that the long head of the biceps is essentially inactive during shoulder-related activities in normal shoulders. Furthermore, they showed that the presence of a rotator cuff tear results in the same lack of activity. Rodosky et al. demonstrated in an in vitro cadaveric model that the long head of the biceps may passively contribute to anterior stability of the glenohumeral joint in the abducted and externally rotated position by increasing the resistance of the shoulder to torsional forces. More recent studies have shown a complex interaction between the shoulder and the elbow, including the biceps tendon. Loading of the biceps tendon and changes in elbow position lead to changes in shoulder motion and shoulder muscle recruitment.

History

A thoughtful, concise history and physical examination remain the most important components in establishing the diagnosis in an individual with shoulder symptoms. Treating the shoulder can be significantly complex; imaging studies, examination under anesthesia (EUA), and arthroscopy can sometimes be used to help clarify the clinical picture and make an accurate diagnosis. Such studies, however, should only be a supplement to a good history and physical exam.

The history can begin by questioning the patient. What bothers you about your shoulder? How did it start bothering you? When did it start? Do you have pain? Does your shoulder feel unstable? Is there a history of trauma? What specific activities exacerbate the pain or exacerbate the difficulties with your shoulder? If the shoulder is painful during a throwing motion or other type of athletic motion, at what phase of the motion does the pain occur? What specific modalities or activities alleviate or exacerbate what is bothering you? Is there a history of previous shoulder surgery? It is also important to exclude other diagnoses such as cervical radiculopathy. Pain that stems from a cervical origin may often radiate distal to the elbow and into the hand, and consequently, the patient should be asked about such symptoms. These questions, coupled with a standard medical history, can help point the surgeon toward the diagnosis.

Physical Examination

Because shoulder pathology can be complex, the specific physical exam tests that may elicit these symptoms can be specific and quite subtle, even when positive. As such, it is not useful to apply the “shotgun” approach to diagnosis, in which every test described for the shoulder is performed on every shoulder. The differential-directed approach, as in the history-taking part of the examination, helps direct the physical exam toward the tests that will either confirm or refute the tentative diagnosis. The physical examination should nonetheless be organized and thorough.

At the start of the physical exam, an initial impression is taken regarding the athlete's age, overall health, and level of specific distress related to the shoulder problem. Inspection, palpation, range of motion (ROM), strength testing, and neurologic and vascular stability assessment constitute an orderly sequence.

Inspection considers symmetry (taking into account that overhead athletes may have unilateral drooping of the dominant shoulder) or deformities such as old acromioclavicular injuries and muscle wasting, which is most often located in the infraspinatus fossa with a rotator cuff tear ( Fig. 47.5 ). A proximally ruptured biceps tendon shows the characteristic bulging distally with muscle contraction or “Popeye” sign ( Fig. 47.6 ).

The location and degree of tenderness found on palpation often provide a reliable physical sign leading to an accurate diagnosis. Tenderness in the bicipital groove (2 to 5 cm distal to the anterior acromion and midway between the axilla and the lateral deltoid with the arm in the anatomic position) is a reliable sign of bicipital tendonitis ( Fig. 47.7 ). Tenderness in this region with palpation and passive external rotation of the arm (rolling the bicipital groove under the examiner's fingers) is another reliable sign of bicipital pathology. The supraspinatus insertion (Codman's point) is palpated through the deltoid just distal to the anterolateral border of the acromion with the shoulder extended and internally rotated. Maximal tenderness over the acromioclavicular joint may also indicate specific pathology.

Active and passive ROM should be documented in all planes. This includes elevation in the scapular plane and external rotation with the arm at the side, which can be recorded in degrees. It is also important, especially in athletes, to document external rotation (particularly passively) in the 90-degree abducted position in the coronal plane. This position represents a more functional measure of external rotation. Internal rotation can be recorded as the most cephalad vertebral level obtainable by the “hitchhiking thumb” or index finger ( Fig. 47.8 ).

Strength is considered along with ROM. Although assessment of strength is part of the neurologic examination, it is particularly important in patients with rotator cuff pathology. Objective weakness beyond that which can be attributed to pain or a neurologic deficit is a highly specific sign of rotator cuff deficiency. The remainder of the neurologic examination helps rule out pathology such as a cervical root, brachial plexus, or peripheral nerve lesion.

Examination of the regional vascular supply is necessary as a baseline and also to evaluate for conditions such as thoracic outlet syndrome.

Finally, a number of special tests should be considered. The signs of impingement are characteristic of rotator cuff tendinitis and tears. These include a painful arc of abduction between 60 and 120 degrees, pain on forced forward flexion in which the greater tuberosity is forced against the anterior acromion (Neer's sign), and pain on forcible internal rotation of the 90-degree forward flexed arm (Hawkins' sign, or the impingement reinforcement test) ( Figs. 47.9 and 47.10 ). The latter maneuver causes impingement of the anterosuperior rotator cuff and biceps against the coracoid and CA ligament. Biceps tendon involvement is demonstrated by Speed's test, in which pain is reproduced on resisted forward elevation of the humerus against an extended elbow. The lift-off test assesses for subscapularis pathology and involves bringing the patient's hand to the lumbar spine region with the palm facing outward. An inability to lift the hand away from the back in this internally rotated position indicates subscapularis pathology ( Fig. 47.11 ). Another method of isolating the subscapularis muscle involves internally rotating the arm across the patient's chest and testing strength ( Fig. 47.12 ). Jobe's test for supraspinatus weakness or impingement involves abducting the patient's arm to 90-degrees, angling forward 30-degrees (thereby bringing the arm into the scapular plane), and internally rotating so the thumb points to the floor ( Fig. 47.13 ). Pain with the Jobe's test indicates supraspinatus tendinopathy, whereas gross weakness likely indicates a supraspinatus tear. The examiner then presses down on the arm while the patient resists movement. Any elicited pain or weakness indicates supraspinatus pathology. Assessment of the infraspinatus muscle is performed by testing external rotation strength with the arm in neutral abduction/adduction ( Fig. 47.14 ). Yergason's test is performed with the elbow flexed to 90 degrees and the forearm pronated. The examiner grasps the wrist and resists active supination by the patient. Pain in the area of the bicipital groove is suggestive of pathology in the long head of the biceps. The active compression test (O'Brien's test, with resisted elevation and the arm at 90 degrees of forward flexion and 10 to 15 degrees of adduction) may also be positive with pathology of the long head of the biceps without a superior labral-anterior posterior (SLAP) lesion.

Biceps tendon instability (medial subluxation or dislocation) can be determined by passively abducting the shoulder to 80 to 90 degrees and eliciting a palpable snap in the region of the bicipital groove with internal and external rotation. This is a rare presentation as an isolated entity and usually indicates a lesion to the superior fibers of the subscapularis tendon and/or the SGHL.

Imaging

Diagnostic imaging for rotator cuff lesions has advanced significantly in recent years. The most commonly used methods to evaluate the cuff are detailed here.

Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) has become the gold standard for the assessment of rotator cuff pathology, with sensitivity and specificity exceeding 90% in most current series ( Fig. 47.15 ). MRI can demonstrate the size, location, and characteristics of the cuff pathology—and whether full thickness, partial thickness, or intratendinous. Furthermore, MRI allows for the assessment of rotator cuff muscle atrophy, fat infiltration, and the presence of concomitant pathology such as acromioclavicular arthrosis or biceps tenosynovitis. The evaluation of muscle quality is essential as this may allow the physician to more accurately counsel the patient as to the reparability of the rotator cuff and expected outcomes. There are drawbacks to MRI, however. Patients are occasionally unable to tolerate the exam because of claustrophobia or inability to remain still for the period necessary to obtain a useful scan. The presence of metallic implants may interfere with image acquisition, and other implants such as pacemakers or recently placed vascular clips may preclude MRI evaluation.

Decision-Making Principles

The key principle in treating a patient with a rotator cuff injury is the judicious correlation of a patient's history, physical examination, imaging studies, and, if necessary, intraoperative findings to make an accurate diagnosis of the etiology of the patient's complaint. When an accurate diagnosis has been made, the surgeon and patient can have an informed discussion of treatment options and determine the most effective way to help the patient achieve the patient's goals.

First and most important in the management of any individual with a rotator cuff, impingement, or biceps problem is establishing the correct diagnosis. We place strong emphasis on a careful history, thorough physical examination, plain radiographs, and the judicious use of diagnostic injections. Further investigation (usually in the form of MRI) is reserved for individuals with an atypical presentation, those who are older, those with a significant traumatic episode, and those in whom a lesion requiring surgery is suspected.

The diagnosis and treatment of the rotator cuff or biceps injury is based on the etiology, as outlined below. The type of management used follows from the etiologic classification. Of note, the focus of treatment is nonoperative in the great majority of individuals.