DIFFERENTIAL DIAGNOSIS OF SHOULDER INJURIES IN SPORTS

STEPHEN OWENS, MD, and JOHN M. ITAMURA, MD

The shoulder is very susceptible to injury in sports. Its use as a battering ram in collision sports, frequent falls and direct blows, and the demanding combination of power, flexibility and repetition in overhand sports make this joint highly vulnerable. The complex anatomy of the shoulder creates a challenge for the clinician faced with an injury, be it chronic or acute, and many symptoms overlap. Chronic symptoms are often vague and nonspecific, highlighting the importance of a careful history and physical examination. This review article looks at various shoulder injuries that are relevant to sports, and discusses their differential diagnosis. KEY WORDS: Shoulder, injury, sports, athlete, diagnosis

Athletic injuries to the shoulder are both common and unique, and even for the most experienced examiner they can be difficult to diagnose and manage. Most occur from either direct or indirect trauma or result from repetitive use. Fractures, dislocations, sprains, and tendon ruptures are everyday occurrences in contact sports that produce frequent falls and collisions, whereas chronic injury is the product of strain and fatigue from overuse. Patterns develop across sports that place similar demands on the shoulder and that require similar motion. These injury patterns are most prevalent in overhand throwers. There is an ongoing attempt to better understand these challenging clinical problems, and the treatment of shoulder injuries is an evolving science. The objective of this article is to review the cause of shoulder pain and injury resulting from both trauma in the contact athlete and from overuse in the overhead athlete.

The diagnosis of a shoulder injury requires a detailed, yet focused, history and physical examination, accompa- nied by a fundamental knowledge of the anatomy. These are the most useful tools in eliciting the clinical features of tissue injury, which can be quite subtle. The ability to correlate the history with the physical examination de- pends on understanding the mechanism of injury and being able to reproduce the symptoms clinically. Knowl- edge of the patient's participation, the movement and positions that cause pain, the symptoms described, and their temporal relationships and duration is important, in particular when a chronic injury presents. The age of the patient can help identify certain risk factors. For instance, the older athlete is more prone to degenerative tendinopa- thy of the rotator cuff with subacromial impingement, whereas the younger athlete, with greater tissue laxity, is more prone to instability.

From USC Orthopaedic Surgery Associates, Los Angeles, CA. Address reprint requests to Steve Owens, MD, USC Orthopaedic

Surgery Associates, 1510 San Pablo, Suite 322, Los Angeles, CA 90033-4608.

Copyright 2000 by W.B. Saunders Company 1060-1872/00/0804-0001 $10.00/0 doi:10.1053/otsm.2000.17773

Shoulder pain can be a misleading symptom. Referred pain from cervical radiculopathy is common, and an examination of the cervical spine, including provocative maneuvers such as the Spurling test and cervical traction, as well as a sensory and motor neurologic examination, evaluates these lesions. Cardiac ischemia, pericarditis, intra-abdominal pathologic conditions, or thoracic outlet syndrome can present as shoulder pain, as can carpal tunnel syndrome and other peripheral nerve entrapment syndromes. Bone and soft tissue tumors are often associ- ated with continuous, irregular, deep pain, along with constitutional symptoms such as fever, weight loss, mal- aise, or fatigue. A brief review of systems will help determine the relevance of these entities in the evaluation.

ACUTE SHOULDER INJURIES

Acute injury prevention has greatly improved with the development of sophisticated equipment and protective gear, but the tremendous forces generated in collision sports continue to cause injury. The traumatic shoulder can present a challenging clinical encounter, especially when there is inhibition and guarding. Knowledge about the position of the arm and forearm at the time of injury, the degree of muscle contraction or relaxation, and the direc- tion and momentum of the athlete helps determine the type and severity of the injury. Additionally, information about the mechanism and force of the injury, giving-way sensations, pops or snaps, or numbness and paresthesias helps describe the pathoanatomy. Often a delayed examina- tion is useful to allow the acute swelling and pain to resolve.

Traumatic injuries to the shoulder can be categorized into osseous, soft tissue, and nerve lesions. The clavicle is the most frequently fractured bone and occurs by either a direct or indirect mechanism. A history of a fall directly onto the tip of the shoulder is typical, as is a history of a fall onto the outstretched hand. There is little difficulty in making the diagnosis of a clavicle fracture. Associated soft tissue disruption, particularly that to the coracoclavicular ligaments, can be a troublesome feature of the distal clavicle fracture, and appropriate management mandates

Operative Techniques in Sports Medicine, Vol 8, No 4 (October), 2000: pp 253-257 253

an accurate classification. Proximal humerus fractures occur infrequently. Fracture geometry can be complex, and a computed tomography (CT) scan may be required to realize the extent of the bony injury. A fracture-dislocation involving the greater tuberosity indicates a disruption of the anterior capsulolabral complex and a likely rotator cuff tear.

Fractures of the scapula involving the body, glenoid neck or rim, coracoid, and acromion are uncommon in sports, and usually have associated injuries. An anteropos- terior (AP), axillary, and Y-view are necessary to avoid missing these lesions. Anterior or anteroinferior glenoid rim fractures typically represent a bony Bankart lesion, with associated anterior instability. A history of a disloca- tion confirms this. The acromion fracture occurs after a fall onto the shoulder or a direct blow. Either the West Point or axillary view is most helpful in characterizing these frac- tures. Isolated coracoid process fractures are very uncom- mon and in the literature are described only in case reports. 16 This injury produces pain anteriorly that wors- ens with deep inspiration. Radiographically they are best detected with either the axillary view or a 30 cephalic tilt view. Resisted arm flexion and forearm supination recre- ates pain, and the mechanism of injury appears to be indirect with the arm abducted, extended, and oriented backward.

Stress fractures about the shoulder, though exceedingly rare, are considered when symptoms are vague and atypi- caU 3 Bony tenderness of insidious onset that is slow to resolve may represent such an injury. There have been 2 reported cases of stress fracture to the clavicle, confirmed with bone scan. These were in a javelin thrower and a diver. Scapular stress fractures have been reported, one along the superomedial edge in a jogger who was using hand-held weights, another at the base of the acromion in an offensive lineman, and another at the coracoid base in a trap shooter. Bone scans and magnetic resonance imaging (MRI) scans remain the best radiographic modalities.

Soft tissue injuries caused by blunt or indirect trauma are routine occurrences in contact and collision sports. Soft tissue contusions over the deltoid, and the trapezius at the base of the neck, regularly occur in tacklers, and not uncommonly lead to myositis ossificans. A history of direct trauma to the region associated with local tenderness and ecchymosis helps differentiate these injuries from the more chronic cuff tendonitis, and provocative tests for rotator cuff pathology are generally negative. Myositis, when present, can be exquisitely tender and painful, and radio- graphically appears as lacy peripheral ossification with soft tissue swelling.

An athlete with an acromioclavicular (AC) joint sprain will describe a fall directly onto the shoulder, a direct blow to the shoulder, or a fall on an outstretched arm. Local tenderness and excessive joint mobility are good clinical indicators, but radiographs are needed to rule out a distal clavicle fracture. Weighted radiographs are rarely needed, because a good history and physical examination are usually sufficient to make the diagnosis. Localized pain with elevation of the arm occurs because of the pull of the deltoid and trapezius on the injured joint, and cross-body adduction compresses the joint, causing pain. Nondis- placed type I sprains should be differentiated from rotator

cuff pathology, glenohumeral subluxation, and burner syndrome.

Glenohumeral dislocations are most common anteriorly and inferiorly. The classic traumatic dislocation causes an avulsion of the anterior-inferior labrum and ligamentous restraints and varying degrees of plastic deformation to the anterior capsule. In certain instances, subscapularis tearing occurs. A violent extension of the abducted, externally rotated arm is the most frequent mechanism. Clinically, the arm is held away from the body and externally rotated, and the posterior deltoid contour is flattened or absent. A first-time dislocator occasionally will reduce spontane- ously before treatment, although this is the exception. Axillary nerve injury can be a cause of late deltoid dysfunction, and brachial plexus injuries may occur, so a thoroughneurologic examination before and after interven- tion is warranted. The diagnosis is usually clinical, but orthogonal radiographs in AP and lateral planes are necessary to rule out associated fractures and to determine the direction of dislocation. Either a scapular Y view or a Velpeau lateral is useful when an axillary lateral view is not accomplished. Close attention to the glenoid will avoid missing a bony Bankart lesion. A West Point view will help visualize this, although a CT scan will provide more information about the size and geometry of the fracture, as it will for a large Hill-Sachs lesion.

Posterior dislocations caused by trauma are much less common and usually occur from a fall onto the flexed, adducted, and internally rotated arm. Less deformity is evident, and the same radiographs are necessary to con- firm the diagnosis. The arm is internally rotated and held at the side. This posturing is not unique and contributes to the reported 50% misdiagnosis rate. A good lateral radio- graph, part of every trauma series, cannot be overstated. A reverse Hill-Sachs lesion can be appreciated with an external rotation radiograph, but, again, is best character- ized by a CT scan.

Traumatic rotator cuff tears occur rarely in athletes younger than 35 years and are best understood as a consequence of degeneration and impingement in the older athlete. Acute ruptures result from a violent mecha- nism in which the torn muscle-tendon unit maximally contracts against an eccentric load. Cuff weakness is best shown by the supraspinatus test and resisted external rotation at the side with injury to either the supraspinatus or infraspinatus, respectively. Isolated subscapularis tears show weakness on the lifboff test, which is performed by the patient's hand pushing off from the back. Pain and tenderness are usually found over the greater tuberosity or underneath the anterolateral acromion with a tear of the supraspinatus. Subscapularis tears produce anterior shoul- der pain and tenderness. Anterior instability may be contributory to these latter injuries, and the apprehension sign is commonly positive. A subluxed biceps frequently accompanies a tear of the subscapularis tendon, particu- larly when the tear extends into the rotator interval. An irritated biceps tendon is shown by a positive Yergason and Speed's test combined with direct tenderness along the bicipital groove. O'Brien's test also may be positive. Acute rotator cuff tears, like degenerative tears, commonly produce a dull ache and cause night pain. The differential includes an AC joint sprain, deltoid strain, subluxation,

254 OWENS AND ITAMURA

isolated biceps lesions, or suprascapular neuropathy. It is therefore important to sort out true weakness from painful inhibition.

Acute nerve injuries about the shoulder have been reported in a variety of different sports. Perhaps the most susceptible and troublesome is the axillary nerve, which is injured in 9% to 18% of anterior shoulder dislocations. Blunt trauma and hematoma formation also have been implicated in cases of axillary neuropathy. 2 Deltoid atro- phy occurs as a consequence of chronic denervation, though in the acute setting weakness is the most pro- nounced finding. Sensation is often preserved and is not a reliable indicator of nerve injury. An isolated axillary nerve injury is differentiated from a more proximal lesion along the brachial plexus, and a rotator cuff tear, especially after a traumatic shoulder dislocation. Electromyograph/nerve conduction study (EMG/NCS) are the most useful diagnos- tic tools. 26

The suprascapular nerve may be injured by a blow to the superior shoulder or, more commonly, from acute stretch- ing. The location of the injury defines the motor involve- ment to the supraspinatus and infraspinatus. Clinical similarities with rotator cuff tears make differentiating these two lesions challenging. Suprascapular neuropathy generally produces vague aching pain posterosuperiorly but can coexist with impingement signs and symptoms. Atrophy, weakness, normal sensation, and a preserved deltoid are not unique to either diagnosis. EMG/NCS are needed to confirm the diagnosis.

Scapular winging indicates weakness of the serratus anterior, which is innervated by the long thoracic nerve. Injury to this nerve was first reported in 1937 and has been found to occur in sports ranging from archery to football. TM It is most commonly a traction phenomenon, though contusion from a direct blow is possible. Winging of the scapula is the classic physical examination finding and is best demonstrated by having the patient perform a stand- ing pushup against the wall. Scapular winging may not occur for several weeks after injury until the trapezius stretches out. Thus, the early findings are often limited to aching/burning pain in the posterior shoulder with associ- ated weakness on arm elevation and abduction. EMG/ NCS are, again, the necessary tests.

CHRONIC INJURIES

The mechanism of chronic shoulder injury in overhand athletes is a complicated, and perhaps controversial, topic. The glenohumeral joint is the most mobile joint in the body, and its anatomy is variable and complex. The intricate coordination of motion and stability allows for remarkable athletic versatility. Repetitive motion at or beyond its physiologic range, which is typical of most overhead sports, threatens the integrity of the soft tissue stabilizers in their efforts to maintain joint congruity. Most overuse injuries are now understood as the result of a breakdown in joint stabilization. A large volume of literature has been devoted to understanding the mechanism of shoulder instability in athletes, and our knowledge continues to evolve.

This forceful, repetitive strain combines with muscle fatigue and poor scapulohumeral rhythm to create a spec-

trum of capsulolabral pathology. Excessive translation of the humeral head on the glenoid results. There are varying theories as to the cause of this instability phenomenon, from stretching of the anterior capsule and microinstabil- ity, to the circle concept, with a loss of capsular integrity caused by posterosuperior labral peelback. 19 Labrum, cap- sule, biceps anchor, rotator cuff, and coracoacromial arch pathologic conditions are common in these athletes. Age has significant bearing on the type of lesion seen. Tissue injury in the athlete over age 35 years usually relates to degenerative processes, in contrast to the younger athlete, in whom instability is the primary contributor. Nerve compression also can cause pain and can mimic symptoms associated with cuff and deltoid pathology.

Important aspects of the history, aside from age1 include type of sport, handedness, location, duration and character of pain, mechanical symptoms such as clicking or catching, and the nature of onset. Valuable information is gained from knowing the relationship of pain to the specific activity, as is knowing at what phase during the throwing motion pain occurs and the location of the pain. Also valuable is knowledge about training techniques, which, if unsupervised and performed incorrectly, can propagate the injury.

Numerous lesions cause pain anteriorly in the shoulder. A common consequence of anterior instability is anterior shoulder pain, and pain that occurs in the late cocking or early acceleration phase of the throwing motion is convinc- ing. Varying degrees of laxity may be appreciated on physical examination, but a positive apprehension sign and relocation test is usually diagnostic. Pathologic condi- tions that can be associated with anterior instability or subluxation, aside from a disruption of the anterior labrum and capsule, include a rotator interval tear or even a partial subscapularis tear. Again, biceps instability and tendonitis frequently result from this. These 3 lesions also cause pain anteriorly and are suspected in the face of continued weakness and pain on internal rotation, pain with provoca- tive biceps tests as previously described, and tenderness anteriorly and along the bicipital groove.

Lesions of the superior labrum and biceps anchor may produce pain anteriorly. Commonly the thrower will give a history of painful catching or clicking in the abducted, externally rotated position. Several different maneuvers have been described for identifying these SLAP lesions, most of which create tension along the long head of the biceps with the humerus internally rotated and adducted. Deltoid muscle strains in the anterior head will be point tender over the site of injury and possibly ecchymotic, painful with forward elevation, and the history is usually straightforward. Poorly localized anterior shoulder pain associated with nondermatomal upper extremity paresthe- sias may represent compression of the axillary nerve as it passes through the quadrilateral space. Symptoms are most pronounced when the shoulder is placed in the abducted, externally rotated position. Rare but seen in the young overhead athlete, the quadrilateral space syndrome is best diagnosed with an arteriogram. Occlusion of the posterior humeral circumflex artery, which courses with the axillary nerve, is seen as the arm achieves the position of abduction and external rotation.

Pain over the lateral deltoid and subacromial region

DIFFERENTIAL DIAGNOSIS OF SHOULDER INJURIES 255

raises suspicion for either rotator cuff injury or impinge- ment and bursitis. Overuse in the younger athlete from throwing, swimming, or other overhead activities can fatigue and injure the cuff, causing rotator cuff tendonitis. Increased training, improper mechanics, poor condition- ing, or a combination thereof are suspected. Achy pain made worse with abduction or forward flexion of the arm, tenderness along the cuff insertion and subacromial re- gion, and impingement signs are usually found. Symp- toms that persist despite a course of physical therapy and anti-inflammatories are suggestive of a rotator cuff tear, particularly if the history elicits disruptive night pain.

Other causes of lateral shoulder pain include calcific tendinopathy and suprascapular nerve compression. Cal- cific tendinopathy can be marked by severe, unrelenting burning pain that is either abrupt in onset or more gradual in onset and progressive. Radiographs aid in making this diagnosis. Suprascapular neuropathy from compression at the transverse scapular l igament or the spinoglenoid notch may initially be difficult to distinguish from cuff pathology. Pain is vague but often lateral and posterior, and weakness on elevation and external rotation mimics a rotator cuff tear. The younger athlete with persistent weakness and evolving atrophy of either the infraspinatus or both the infraspinatus and supraspinatus is rarely found to have a large rotator cuff tear, and a suprascapular nerve lesion should be suspected. 2,18,25 The older athlete with this history has a cuff tear until proved otherwise. The appropri- ate imaging and electrodiagnostic studies facilitate the diagnosis.

Posterior shoulder pain can be a symptom of instability, glenohumeral arthritis, posterior deltoid or proximal tri- ceps strain, or lower cervical nerve root compression. Posterior glenohumeral instability, like its anterior counter- part, is a positional phenomenon that is as difficult to manage as it is to diagnose. Offensive linemen who are repeatedly pushing off with their arms against defensive players are prone to developing posterior instability, fre- quently in players who display ligamentous laxity. Pain with the arm flexed to 90 and internally rotated is usually present, and pain with a posterior drawer to the glenohu- meral joint is provocative. Interestingly, subtle anterior instability commonly produces posterior shoulder pain. The abducted, externally rotated arm can pinch the under- surface of the rotator cuff insertion, and even slight anterior translation can drive this insertion into the poste- rior glenoid, damaging the posterior labrum with repeated episodes. On examination, pain posteriorly in this position indicates this pathologic condition.

Posterior pain in the older athlete could represent degenerative joint disease, which may be seen radiographi- cally. Crepitation, stiffness, and atrophy may exist, though cuff strength and integrity is usually preserved. Pain caused by scapular grinding presents posteriorly, and palpable crepitation makes this an easy diagnosis.

Superior shoulder pain that radiates along the trapezius and down the arm to the hand suggests a cervical origin. Spurling's test may contribute to an accurate diagnosis, although hand weakness, dermatomal sensory loss, and diminished reflexes may be the most specific objective findings. An athlete with cervical radiculitis typically displays some degree of neck stiffness. A tender AC joint

combined with pain on flexion and adduction of the humerus is consistent with AC joint arthritis, although distal clavicle osteolysis presents with the same type of symptoms. Radiographs are needed to differentiate these lesions.

SUMMARY

Shoulder injuries are common problems in all types of sports. There can be a good deal of variability in how symptoms are expressed from individual to individual, and part of the challenge in understanding the injury is being able to interpret the athlete's complaints as they relate to examination findings and the conditions that produce the symptoms. The history is particularly impor- tant because the sensitivity and specificity of many aspects of the examination are variable. A relaxed patient and a systematic evaluation is the best way to be thorough. Radiographs and even MRIs are frequently negative in soft tissue problems in the young athlete. This underscores the importance of a good examination. There may be some utility in using contrast-enhanced MRIs to look at labral pathologic conditions, cysts, or ganglions, but this informa- tion is certainly less useful than the patient's description of symptoms and the examiner's findings. With this aware- ness, we can manage these injuries with more confidence.

REFERENCES

1. Anderson T: Difficult sports-related shoulder fractures. Clin Sports Med 9:31-37, 1990

2. Black KP, Lombardo JA: Suprascapular nerve injuries with isolated paralysis of the infraspinatus. Am J Sports Med 18:225-228, 1990

3. Brukner P: Stress fractures of the upper limb. Sports Medicine 26:415-424, 1998

4. Burkhart SS, Morgan CD, Kibler WB: Shoulder injuries in overhead athletes: The dead arm revisited. Clin Sports Med 19:125-155, 2000

5. Ellen MI, Smith J: Musculoskeletal rehabilitation and sports medicine (shoulder and upper extremity injuries). Arch Phys Med Rehabil 80S:50-58,1999

6. Glousman R: Electromyographic analysis and its role in the athletic shoulder. CORR 288:27-34, 1993

7. Gowan ID, lobe FW, Tibone JE, et al: A comparative electromyo- graphic analysis of the shoulder during pitching. Am J Sports Med 15:586-590,1987

8. Hawkins RJ, Kennedy JC: Impingement syndrome in athletes. Am J Sports Med 8:151-158, 1980

9. Ho CP: MR imaging of rotator interval, long biceps, and associated injuries in the overhead-throwing athlete. MRI Clin North Am 7:23-36, 1999

10. Hovelius L, Augustini BG, Fredin OH, et al: Primary anterior dislocation of the shoulder in young patients. J Bone Joint Surg Am 78:1677-1684, 1996

11. Hoyt WA: Etiology of shoulder injuries in athletes. J Bone Joint Surg Am 49:755-766, 1967

12. Huber WP, Putz RV: Periarticular fiber system of the shoulder joint. Arthroscopy 13:680-691, 1997

13. Hulstyn MJ, Fadale PD: Shoulder injuries in the athlete. Clin Sports Med 16:663-679, 1997

14. lobe FW, Bradley JP: The diagnosis and nonoperative treatment of shoulder injuries in athletes. Clin Sports Med 8:419-437, 1989

15. lobe FW, Moynes DR: Delineation of diagnostic criteria and a rehabilitation program for rotator cuff injuries. Am J Sports Med 10:336-339, 1982

16. Mariani PP: Isolated fracture of the coracoid process in an athlete. Am J Sports Med 8:129-130, 1980

256 OWENS AND ITAMURA

17. McMaster WC: Ankerior glenoid labrum damage: A painful lesion in swimmers. Am J Sports Med 14:383-387, 1986

18. Mendoza FX, Main K: Peripheral nerve injuries of the shoulder in the athlete. Clin Sports Med 9:331-341, 1990

19. Morgan CD, Burkhart SS, Patmeri M, et al: Type II SLAP lesions: Three subtypes and their relationships to superior instability and rotator cuff tears. Arthroscopy 14:553-565, 1998

20. Perlmutter GS, Apruzzese W: Axillary nerve injuries in contact sports. Sport Medicine 26:351-361, 1998

21. Redler MR, Juland LJ, McCue FC III: Quadrilateral space syndrome in a throwing athlete. Am J Sports Med 14:511-513, 1986

22. Roger B, Skaf A, Hooper AW, et al: Imaging findings in the dominant shoulder of throwing athletes: Comparison of radiography, arthrogra- ph?, CT arthrography, and MR arthrography with arthroscopic correlation. AJR 172:1371-1380, 1999

23. Rowe CR, Zarins B: Recurrent transient subluxation of the shoulder. J Bone Joint Surg Am 63:863-871, 1981

24. Schickendantz MS, Ho CP, Keppler L, et al: MR imaging of the thrower's shoulder. MRI Clin North Am 7:39-48, 1999

25. Silliman JF, Dean MT: Neurovascular injuries to the shoulder com- plex. J Orthop Sports Phys Ther 18:442-448, 1993

26. Wilbourn AJ: Electrodiagnostic testing of neurologic injuries in athletes. Clin Sports Med 9:229-245, 1990

DIFFERENTIAL DIAGNOSIS OF SHOULDER INJURIES 257