Diagnostic imaging of the shoulder joint

4

Diagnostic imaging of the shoulder joint

ANGE L A J O N E S I A I N W A T T

All the imaging techniquesused elsewhere in the body have been used in the shoulder joint with varying efficacy. The first part of this chapter discusses the individual imaging modalities and seeks to explain their relative merits. In the second part, their application to articular and periarticular disorders of the shoulder is reviewed with suggested approaches in clinical usage.

As is generally the case, plain radiography is the most commonly used technique; its variant of observation under fluoroscopic screening may be very helpful in specific instances.

Computerized tomography (CT) has largely replaced linear tomography in this as in many other areas of the body and provides more readily interpretable information. Details of the surrounding soft tissues are also shown on CT, unlike plain tomography.

Arthrography may be performed by the injection of positive and/or negative contrast media into the joint space or into one of the adjacent bursae (bursography). Imaging of the joint by ordinary X-ray or CT then provides additional information, particularly about surrounding soft tissues such as the rotator cuff, and of the intra-articular soft tissues such as the cartilage and synovium. Arthrography is also useful in the diagnosis of intra-articular loose bodies.

Ultrasound has also been used to good effect in some hands to image the surrounding soft tissues and fluid-filled spaces adjacent to the shoulder joint. It will not image the bones of the shoulder girdle.

Scintigraphy with bone-seeking radioisotope agents is used to give a more physiological image of the state of the shoulder. Although non-specific, this is a very sensitive imaging technique which may reveal soft tissue lesions and clarify pathology by imaging other asymptomatic but abnormal areas of the skeleton.

The advent of magnetic resonance imaging (MRI) has revolutionized visualization of the soft tissues surrounding the joint as well as the cartilage within the joint. Soft tissues are particularly important in pathology of the shoulder joint and to a much greater extent than in other joints.

Bailli~re's Clinical Rheurnatology--Vol. 3, No. 3, December 1989 475

476 A. JONES AND I, WATT

I M A G I N G M O D A L I T I E S U S E D T O A S S E S S S H O U L D E R D I S E A S E

Plain f i lm r a d i o g r a p h y

P la in r a d i o g r a p h y s h o u l d b e t h e first i n v e s t i g a t i o n r e q u e s t e d in t h e assess- m e n t o f any j o i n t ( T a b l e 1). T h e usua l ru les app ly in i n v e s t i g a t i o n o f t h e

Table 1. Disorders of the shoulder which may be seen on plain radiography.

Trauma Fracture (old or new) Dislocation of glenohumerai or acromioclavicular joint Bony deformities typical of specific lesions, the Hill-Sachs deformity associated with

recurrent dislocations, intra-articular loose bodies

Rotator cuff disease Calcification of tendons, ligaments, cartilage, or joint fluid Superior subluxation of humeral head (distance between humeral head and acromion

< 7 mm) or other changes of impingement

Other Erosions of inflammatory arthritis, infection Loss of joint space associated with cartilage disease, infection Presence of a joint effusion Signs of a neoplasm, either primary or secondary, with or without evidence of soft tissue

involvement

Figure 1. AP view. Erect (p/eferably) or supine facing tube, rotated 30 ~ until scapula parallel to film, centred to coracoid. Elbow flexed with forearm facing forward (neutral), forearm on abdomen (internal rotation) or palm facing forward (external rotation). The rotation of the patient from the AP position enables the glenohumeral and subacromial spaces to be seen in profile.

DIAGNOSTIC IMAGING 477

shoulder: namely, that the minimum initial requirement is for two views at right angles to each other.

The standard anteroposterior (AP) view of the shoulder is often taken incorrectly, without rotation of the patient. The glenohumeral joint space is not then shown in profile and assessment of the joint space is difficult. The congruity of the joint may appear grossly abnormal simply due to projection. A rotated AP (Figure 1) is a more informative view and should be performed whenever possible. A true lateral of the glenohumeral joint, showing the joint space in profile, is obtained by the standard axial view (Figure 2) or special (Stripp) axial view (Figure 3), taken with a long object-to-film distance. The latter is easier to obtain than the standard axial view in the presence of joint disease because of the patient's reluctance to abduct the arm sufficiently. The axial view shows most clearly the AP relationship of the joint and, in particular, whether there is any AP shift. If even the Stripp axial view is impossible then an unsatisfactory compromise may have to be made, with a lateral scapular or transthoracic lateral view being substituted; however, these views are inadequate for any purpose other than acute trauma.

The second joint at the shoulder, the acromioclavicular joint, requires a different approach. It is often well seen on AP shoulder views, although it may be overexposed due to the lack of overlying soft tissue. Definition may be improved by the use of a ( 'banana') wedge or lead-rubber over the

Figure 2. Axial (inferosuperior) view. Arm abducted (elbow flexed) with film lying on top of shoulder and beam directed into axilla from below, centred to head of humerus. Alternatively superoinferior view with curved cassette placed in axilla, beam centred to head of humerus. In addition to the profiled glenohumeral joint, the acromioclavicular joint is well seen in this projection.

478 A. JONES AND I. WATT

shoulder. This joint, overlying the head of the humerus, is well shown by the axial view. The assessment of abnormali ty of the acromioclavicular joint may also require stress views. Compar ison should be made between resting and stress views of both the affected and normal sides. Weighted strapping applied to the wrists is the simplest way to apply stress to the acromioclavicular joints.

In the assessment of rotator cuff disease (probably the most common abnormali ty affecting the shoulder joint), an axial view will usually enable determination of whether any calcification present is anterior or posterior. It may also show any AP shift of the humeral head in relation to the glenoid (an indicator of rota tor cuff instability). Additional views may be needed to show the precise site of calcification by assessing the position of calcification at different degrees of rotation.

In the diagnosis of recurrent dislocation, Stryker 's view (Figure 4) may be helpful in visualizing the presence of a compression fracture of the posterior aspect of the humeral head (Hill-Sachs lesion).

Most diseases affecting the shoulder joint present changes late on the plain film. Such changes may be difficult to interpret for various reasons,

Figure 3. Stripp axial view. Patient sits on stool and leans back, with shoulder rotated backwards. Cassette is placed over shoulder at 35 ~ , beam directed straight up. This view is useful when a patient is unable to abduct his arm.


including inadequate visualization, subtlety and the fact that the majori ty of the changes occur in the soft tissues. This rarely causes much of a problem in rheumatological differential diagnosis as the shoulder tends to be involved late in the disease and rarely in isolation. In such cases the diagnosis is made from the more characteristic appearances in other joints and investigation of the shoulder is purely to confirm or exclude involvement or local compli- cation.

Plain film radiography may be augmented by the use of fluoroscopic screening of the pat ient while actively and passively moving the shoulder joint. This is of particular use in the assessment of rotator cuff disease and the painful arc syndrome. In these circumstances, mechanical abnormali ty within the joint, such as bony impingement , may be directly related to the onset of symptoms. Instability of the soft tissues and the presence of superior subluxation of the humeral head may also be assessed.

CT of the shoulder is rarely used as an initial investigation but may be

Figure 4. Stryker's view. Patient supine, palm on top of head, elbow pointing forwards. Beam centred to coracoid. For recurrent dislocation, to visualize presence of the Hill-Sachs lesion (compression fracture of posterior aspect of humeral head).

480 A. J O N E S A N D I. WATT

helpful in t rauma, either when a fracture is not clearly seen on the plain film or to delineate the ana tomy more clearly. Axial imaging of both shoulders may be degraded by severe artefacts in larger patients. Better images may be obtained by imaging only one shoulder with the patient lying obliquely in the gantry. The thickness of the cartilage may be assessed in three dimensions and the labrum is also well outlined, although these may both be bet ter seen on CT arthrography than plain CT.

Arthrography Two major techniques of shoulder ar thrography exist: images may be taken conventionally and with CT (Tables 2 and 3).

Table 2. Indications for arthrography.

Evaluation of rotator cuff (nearly 60% of some series: 2/3 of these had pain and diminished range of movement, 1/3 had definite clinical evidence of rotator cuff tear; Berquist, 1986)

Adhesive capsulitis (diagnosis and treatment) Impingement syndrome Chronic subluxation/instability Postoperative or post-trauma, including demonstration of loose bodies Demonstration of synovial or cartilage disease

Table 3. Arthrographic techniques.

Single positive contrast arthrography--to show extent of grossly distended capsule --to show rupture of capsule (particularly in

rheumatoid arthritis) Double contrast arthrography --assessment of rotator cuff

--synovial or cartilage disorder -----chronic instability

Double contrast CT arthrography --trauma -----chronic instability --loose bodies

Single positive contrast bursography --used as a complementary procedure to arthrography

Arthrography of the shoulder joint is per formed with the patient supine on a screening table, the hand of the shoulder to be examined lying palm upward. A small gauge spinal needle is advanced vertically downwards under screening control slightly lateral to the joint space profiled on the screen (i.e. towards the humeral head). This ensures that the needle will not be deflected by the labrum but that if it hits the humeral head it will be deflected medially into the joint space. When the needle meets the resistance of the humeral head, local anaesthetic instilled into the joint should flow freely. If it does not, the needle should be slightly withdrawn.

Non-ionic contrast medium is then injected (initially under X-ray control to ensure an intra-articular position). For a double contrast conventional ar throgram, 6 ml are injected and the joint capsule is then distended with air (usually 10-15 ml), the needle removed and the shoulder manipulated to distribute the contrast medium. For CT arthrography, only a very small


volume (usually I ml) of a positive contrast medium is injected, with 10-- 12ml of air. This is adequate because of the improved contrast definition possible with CT. In single positive contrast arthrography, sufficient contrast is injected to show rupture of the joint capsule (usually in rheumatoid arthritis).

Non-ionic contrast media are preferred to ionic media as the latter may be painful. For the same reason it is better not to use adrenaline, the use of which makes little discernible difference to the quality of the examination.

After injection under screening control the joint is imaged with plain films or by CT in the axial plane with contiguous 5 mm slices. Reconstructions in the sagittal or coronal planes may also be performed subsequently, if required. Problems with artefacts on CT images may result postoperatively if metal screws or prostheses are in situ.

Subacromial bursography

This is performed with the patient in the same position on the screening table as for arthrography (Lie and Mast, 1982). The tip of the acromial process may be marked with a metal marker. A fine gauge needle is advanced towards the under-surface of the acromial process after preparation by aseptic technique and infiltration of local anaesthetic. When local anaesthetic flows freely into the tissues, with no feeling of resistance, the tip is within the bursa and contrast medium is injected. Approximately 5ml contrast medium will be easily injected. The joint capsule is not opacified unless there has been a rupture of the rotator cuff. Films are taken in the AP position in internal rotation and then in external rotation and abduction.

Ultrasonography

Since 1984, high frequency (10 MHz) ultrasonography has been extensively used in the diagnosis of rotator cuff pathology by Crass and his group who claim considerable success in predicting the presence and extent of tears at arthroscopy and/or surgery. For this technique the patient is scanned with the arm behind the back and the probe placed behind the acromion process. Scanning is performed in the sagittal and transverse planes. The normal rotator cuff is seen as a band of low echogenicity between the deltoid muscle and the bone of the humeral head.

Scintigraphy

If local images of the shoulder joint are required, the best views are obtained by imaging from behind because overlying ribs and distance from the detector detract from the quality of the anterior image. A gamma camera is used and early (perfusion) and late (3 h) images are usually recorded. Imaging is generally performed with the bone-seeking isotope 99mTc-hydroxymethylene diphosphonate (HMDP). Other radioisotopes used are 67Ga-citrate and rain-labelled white cells in infection.

Increased uptake of isotope is commonly seen in relation to the gleno-


humeral and acromioclavicular joints on the late-phase images, particularly in elderly individuals. This is so common that it is rarely commented upon, but serves to show how widespread such 'degenerat ive ' change is (Figure 5). Asymmetry in the appearances and, more particularly, involvement of adjacent bone raise the possibility of more significant pathology in these regions.

Magnetic resonance imaging

MRI is a technique unlike most of the others available for imaging the shoulder joint. It is able to image the soft tissues within and surrounding the joint directly, rather than by indirect means (for example, the appearance of the bones and filling defects within the joint capsule). The only other imaging techniques which directly image the soft tissues are real-time ultra-

Figure 5. Whole body [99mTc]HMDP scan. There is increased symmetrical uptake related to the acromioclavicular and sternoclavicular joints and coracoid processes: a normal appearance. Increased uptake related to the knees is also symmetrical and normal. The increased uptake in the skull and right os calcis is due to Paget's disease.

DIAGNOSTIC IMAGING. 483

sound and CT, neither of which is as easy to interpret or as accurate as MRI. Both CT and MRI have the advantage over ultrasound of not being operator dependent.

Visualization of the soft tissues is even more significant in the shoulder than in other joints as the most common primary abnormalities are those of the soft tissues, especially the rotator cuff.

MRI is a more versatile technique than CT, allowing imaging in any three planes without movement of the patient. Both shoulders may be imaged at the same time and direct comparison made in both the coronal and transverse planes. If only one shoulder is being investigated, however, the images will be of superior quality if a closely applied surface coil and small field of view with offset centre of field are employed. Angled coronal images (equivalent to the angled AP image in plain radiography) are also prefer- able. Imaging in transverse and coronal planes will usually give adequate information but the option of sagittal scanning is also available.

The choice of sequences required varies slightly depending on the pathology under investigation. However, in most cases, contiguous 5 mm cuts with T1 weighted (short TR, short TE, spin echo sequence) scans in both planes for anatomical information and T2 weighted (long TR, long TE, spin echo) scans in the coronal plane for further tissue characteristics will give optimal information. In malignant disease the short tau inversion recovery (STIR) sequence may be helpful in highlighting abnormal tissue.

IMAGING ABNORMALITIES IN DISORDERS OF THE SHOULDER

Trauma

Early

Imaging in trauma may be difficult because of immobility and pain; it is often in these circumstances that the unsatisfactory views such as the transthoracic lateral are taken, compounding the diagnostic difficulty. It is important to be wary of the impacted humeral neck fracture and the posteriorly dislocated humeral head. As in other joints, the presence of a lipohaemarthrosis on a horizontal beam film may be a pointer to important pathology.

Some fractures of the humeral neck may be difficult to detect even on adequate plain radiography. These tend to be the impacted fractures, often occurring in an elderly osteoporotic female patient. CT may help in interpre- tation of difficult plain films (Figures 6 and 7) and show small fractures not seen on such films, particularly those involving the glenoid. Comminuted fractures may be assessed more easily on CT, as artefacts from overlying soft tissues do not cause confusion. A normal isotope scan makes the presence of even an impacted fracture unlikely.

Late

In the presence of recurrent anterior dislocation, plain film abnormalities

484 A. JONES A N D I, WATT

may be seen, although these are often more easily appreciated on manipulation under screening control, which may also demonstrate evidence of glenohumeral instability (Figure 8).

The hatchet deformity is a compression fracture of the posterolateral humeral head caused by impingement beneath the glenoid. It is suggestive of recurrent dislocation but may occur after a single episode. Recurrent dislocation may be caused by an intra-articular loose body associated with the Bankart lesion (a bony defect of the glenoid resulting from detachment of part of the glenoid labrum). This will cause restriction of full movement on manipulation. If the fractured fragment is purely labral it will be non- opaque and will not be seen on plain radiography, but it may be visualized as a filling defect on arthrography or seen directly on CT (Figure 9). Other arthrographic indicators of recurrent dislocation are stripping of the capsule from its bony attachments and capsular redundancy.

CT arthrography may be useful as a first investigation in glenohumeral instability because the thickness of the cartilage is more easily assessed in three dimensions. It has a high overall sensitivity for labral abnormality (96 %) when compared with surgical or arthroscopic findings (Deutsch et al, 1984). Bony lesions and intra-articular loose bodies leading to glenohumeral instability are readily detected. CT arthrography may be particularly useful in

Figure 6. AP film. This elderly man was admitted after a fall. His film was difficult to interpret, with an unusual appearance of the humeral head.


Figure 7. Axial CT (same patient as in Figure 6). A 'hatchet' type deformity of the internally rotated articular surface of the humeral head (between small arrows) is seen, resulting from impaction against the posterior glenoid; note the deformity of the glenoid (large arrow). The mechanism and result of the trauma is now much easier to interpret.

(a)

Figure 8 (a) and (b). Fluoroscopic screening of the shoulder during manipulation. Superior subluxation of humeral head on manipulation under fluoroscopic screening with erosion of underside of acromion. Note position of head at rest (b).

(b)


Figure 9. CT arthrogram; Bankart lesion. The bony and labral (soft tissue) components of the fracture can be seen with the associated laxity of the capsule. Note impression into contrast medium made by normal labrum on opposite side of glenoid (arrow).

imaging the joint after surgical repair has failed, when ordinary arthrography is often difficult to interpret (Singson et al, 1987).

The anatomical changes present in recurrent anterior dislocation are said to be equally well visualized with MRI as on CT arthrography (Kieft et al, 1988a), obviating the need for injection of contrast medium. However, as the cortex returns no signal, the bony loose bodies resulting from these defects are not well seen and there is no place for using MRI in the investigation of acute trauma or when searching for intra-articular loose bodies. The anterior joint capsule may also be difficult to assess unless distended by a joint effusion.

Recurrent posterior dislocation is rare as it is caused by unusual force. The clinical and radiographic problems in this case are those of recognition and reduction at the time of injury.

Periarticular disorders

Calcification within the soft tissues around the shoulder joint is a common abnormality. It is most usual within the tendons of the rotator cuff but may also be seen in the enthesopathies when it is present in a periarticular location. Tophaceous gout may occasionally occur in the shoulder, with well defined erosions being associated with the calcified soft tissue masses. Soft tissue calcification also occurs in scleroderma, dermatomyositis and myositis ossificans.

Tendon calcification may be due to acute calcific tendinitis when it is of low density, amorphous and ill-defined, and may resolve. More commonly, it is


Figure 10. Fluoroscopic screening of the shoulder during manipulation. Calcification in supraspinatus tendon with early irregularity of underlying bone.

Figure 11. Axial view. Extensive well defined calcification in supraspinatus tendon with irregularity of underlying bone.


Figure 12. AP view. Very extensive calcification in supraspinatus tendon with extension into subdeltoid bursa; note fluid level and underlying 'pseudotumour' of greater trochanter, a normal appearance.

Figure 13. View for the bicipital groove. Palm against thigh, bending slightly forward. Cassette against top of shoulder, beam centred to upper aspect of humeral head and angled parallel to shaft of humerus.


due to chronic disease and is extremely dense and organized. Initial investigation should determine within which tendon the calcification lies. That lying within the supraspinatus tendon (Figure 10) is diagnosed most easily as it is usually projected clear of bone in the AP view. Axial views and AP views taken with internal and external rotation of the humerus will separate calcification anterior to the humeral head (supraspinatus tendon) (Figures 11 and 12) from that posterior (infraspinatus or teres minor tendon). Bicipital groove views (Figure 13) should reveal calcification within the biceps tendon (Figures 14 and 15).

Tendinous calcification may be associated with superior subluxation of the humeral head due to complete or partial rupture of the rotator cuff (Figure 16). This is defined as a distance of less than 7 mm between the inferior surface of the acromion and superior surface of the humeral head on the AP film of the shoulder. Subluxation should not be diagnosed on other films showing the shoulder joint, such as a chest X-ray. There may also be concavity rather than the normal convexity of the inferior surface of the acromion due to pressure erosion (Figure 16). This is usually associated with irregularity of the superior surface of the humeral head, an early change in rotator cuff disease.

Rupture of the rotator cuffallows contrast medium and air to extend from the synovial capsule of the shoulder joint superiorly into the subacromial

Figure 14. AP with external rotation. Extensive, well defined calcification in biceps tendon.


Figure 15. AP with internal rotation. Calcification in biceps tendon.

Figure 16. AP view. Bony impingement of the humeral head on the acromial process due to complete rotator cuff tear; marked concavity of the underside of the acromion.


bursa on arthrography (Figures 17 and 18). This may be via a small irregular defect in the acute stages but in longstanding disease little of the rotator cuff may remain, with obvious subluxation and impingement of the humeral head. Partial rupture will not allow leakage but the tear should be outlined by contrast medium. Contrast medium will also extend medially into the subcoracoid bursa after rupture of the rotator cuff.

Subacromial bursography will also outline tendon rupture by leakage of contrast medium into the joint space (Lie and Mast, 1982). CT arthrography may be helpful in imaging the joint after failure of surgical treatment

Figure 17. Double contrast arthrogram; rotator cuff tear. Contrast medium tracks through the ruptured supraspinatus tendon into the subacromial bursa, outlining both sides of the tendon (tear arrowed). Note concavity of acromion process.

Figure 18. Double contrast arthrogram. Contrast medium and air outline the normal joint and the underside of the supraspinatus tendon, showing normal thickness of articular cartilage.


(Singson et al, 1987). Ordinary arthrography may be difficult to interpret in these cases as an abnormal arthrogram after surgical repair of the rotator cuff is very common, even in the absence of symptoms (Calvert et al, 1986). Intrasubstance tears cannot be detected by these methods.

On ultrasound, the normal rotator cuff tissues are seen as a band of low echogenicity between the deltoid muscle and the bone of the humeral head. Inflammatory change and small tears are seen as areas of increased echogenicity within this band. Large tears show as an echo-free region bounded by echogenic edges. Massive tears show as defects with the deltoid

Figure 19. T1 weighted spin echo MRI scan; inclined coronal plane. Normal appearances of muscle and insertion of supraspinatus tendon (arrow) shown in relation to glenohumeral joint and acromion process.

Figure 20. T1 weighted spin echo MRI scan; inclined coronal plane. Large region of calcification in the supraspinatus tendon shown as area of low signal intensity (arrowed).


muscle sitting directly on the humeral head, although care must be taken not to confuse the insertion of the deltoid into the greater trochanter with the humeral head itself (Crass et al, 1984, 1988; Middleton et al, 1985).

The individual muscles and tendons of the rotator cuff can be seen in all planes on M R I (Middleton et al, 1987; Seeger et al, 1987) (Figure 19). Tendon calcification visible on a plain film may not always be seen, however, as both tendons and calcification return a similar low signal intensity on both T1 and T2 sequences (Figure 20). A slight decrease in intensity in an already low signal region may be impossible to detect.

However , T1 weighted imaging is highly sensitive to abnormali ty within tendons and underlying bone (Figures 21-23), with increased signal intensity occurring in tendinitis and partial tears. The differentiation of

Figure 21. T1 weighted spin echo MRI scan; inclined coronal plane. Tendinitis (increased signal) in supraspinatus tendon (confirmed on T2 imaging) with underlying changes in subchondral bone; increased water content of bone marrow due to inflammation.

Figure 2~. T1 weighted spin echo MRI scan; axial plane (same patient as in Figure 17). Decreased signal intensity in subchondral bone again shown.


Figure 23. AP view. Marked subchondral bone changes due to rotator cuff disease; loss of cortex, bony erosion and cyst formation. Similar changes would be seen on the plain film of the patient in Figures 21 and 22.

Figure 24. T1 weighted spin echo MRI scan; inclined coronal plane. Two regions of increased signal intensity within supraspinatus tendon (arrowed) may be due to tear of rotator cuff or tendinitis.


partial tear f rom inf lammatory change is made on T2 weighted scans, tears giving increased signal intensity and inf lammation being less likely to produce increased signal (Figures 24 and 25). Even intrasubstance tears may be detected by increased signal intensity on MRI . Comple te tears of the ro ta tor cuff are simpler to diagnose, having characteristic anatomical as well as signal changes on both T1 and T2 weighted scans (Evancho et al, 1988; Seeger et al, 1988a,b; Zlatkin et al, 1988).

Figure 25. T2 weighted spin echo MRI scan; inclined coronal plane (same patient as Figure 24). Only one region of increased signal intensity, corresponding to that at straight arrow on T1 scan; therefore there is a coexisting tear (straight arrow) and tendinitis (curved arrow).

Figure 26. AP view. Extensive new bone formation at site of impingement of humeral head on underside of acromion, associated with marked superior subluxation and changes in glenohumeral joint; rotator cuff disease complicated by calcium pyrophosphate deposition disease.


Figure 27. Fluoroscopic screening of the shoulder during manipulation. Normal relationship of humeral head and acromion showing position and thickness of the rotator cuff on active elevation of the arm.

Figure 28. Fluoroscopic screening of the shoulder during manipulation. Abnormal relationship of humeral head and acromion showing impingement of the thinned rotator cuff on active elevation of the arm. Note concavity of acromion process.


At the present time, MRI is not widely enough available in the UK to permit scanning of all patients in whom rotator cuff disease is suspected but it may be helpful if other investigations have been exhausted without a diagnosis being confirmed.

In the shoulder impingement syndrome several abnormalities may be present on the plain film. The most common of these are subacromial bony proliferation (Figure 26) and degenerative changes in the greater tuberosity of the humerus or the acromioclavicular joint, each present in about two- thirds of patients studied by Hardy et al (1986). In this same group of patients, only 5% had normal plain radiographs. Bony impingement associated with clinical symptoms may be detected on manipulation of the shoulder under screening control (Figures 27 and 28).

The impingement syndrome may be elegantly shown by bursography; arthrography is often unhelpful in this condition. AP images of the shoulder are taken at different degrees of shoulder abduction in external rotation. Increasing distension of the subacromial bursa as the humeral head is elevated implies impingement. In the normal condition, the bursa remains as a semicrescent of contrast medium. As the pain in this syndrome is caused by impingement of the soft tissues of the rotator cuff and subacromial bursa itself between the bone of the humeral head and acromion process, this investigation may be particularly helpful when no subluxation of the humeral head is present.

Signal changes in the tendons of the rotator cuff occur on MRI in patients with clinical evidence of impingement syndrome, T1 weighted imaging being highly sensitive to abnormality of the supraspinatus tendon and producing increased signal intensity (Kieft et al, 1988b; Seeger et al, 1988a; Zlatkin et al, 1988). Inflammatory change is less likely to produce increased signal intensity on T2 weighted scans.

The distensibility of the capsule may be markedly reduced in frozen shoulder (adhesive capsulitis) to the extent of rendering needling of the joint for arthrography virtually impossible. The patient often experiences severe pain after the injection of only a small amount of contrast or air. If this occurs, the injection of further contrast medium will rupture the capsule and often produce relief of symptoms (so-called 'tension' arthrography). Subse- quent vigorous physiotherapy of the joint is necessary for continued relief.

Articular disorders

The early erosions of rheumatoid arthritis may be difficult to see in the glenohumeral joint, especially if the projection is not optimal. Both marginal and articular surface erosions are present, affecting both glenoid and humerus. Ill defined erosions denote current disease activity. Well defined erosions are also usually due to active inflammatory (including septic) arthritis but may be due to pressure erosion, such as occurs in gout, particularly if they have a periarticular location or demonstrate cloudy calcification.

The diagnosis is usually made with reference to the history as the shoulder is unlikely to be the first joint involved in rheumatoid or other arthritides.

4 9 8 A. JONES AND I. WATT

Late changes in rheumatoid arthritis usually include rupture of the chronic- ally inflamed rotator cuff and may therefore resemble degenerative rotator cuff disease. Marked bony resorption of the humeral head may occasionally occur in rheumatoid or psoriatic arthritis, a neuropathic joint or the caries sicca of an old tuberculous arthritis (Figures 29 and 30) being the only other likely causes of this appearance. Bony fragmentation is common in Charcot joints and calcification may be related to previous tuberculosis. At this site a Charcot joint is almost always due to syringomyelia (Figure 31).

In contrast to the late involvement of the shoulder joint, rheumatoid erosions are frequently present in the acromioclavicular joint and tapering of the lateral end of the clavicle is an important indicator of rheumatoid arthritis.

The differential diagnosis of other inflammatory arthritides affecting the shoulder, such as psoriasis or ankylosing spondylitis, is usually made from the pattern of joint disease elsewhere. The enthesopathies are more likely to result in erosions affecting the greater tuberosity than the joint margins. Proliferative erosions are common in these seronegative arthritides.

Figure 29. AP view. Early TB arthritis; caries sicca. Note loss of joint space, effusion, superior subluxation of humeral head and ill-defined erosions of humeral head corresponding to site of attachment of synovium.

DIAGNOSTIC I M A G I N G 499

There is usually marked periarticular osteoporosis in infective arthritis. The joint space narrowing caused by cartilage destruction in infection

requires that the joint space is well seen in profile. The erosions underlying the destroyed cartilage may be very large and are typically rapidly progressive (Figure 32). It is always important to bear in mind that joint infection occurs in joints affected by rheumatoid arthritis and other arthritides more commonly than in normal joints (Figure 33).

Inflammation within the joint, whether due to arthritis or infection, will increase uptake of bone-seeking isotopes on both vascular and late-phase images. There is also, of course, increased uptake of agents used specifically to demonstrate infection, but this is present even in non-infective inflammation. Scintigraphy is thus often more useful in confirming that the shoulder joint is involved in a systemic disease, such as rheumatoid arthritis, rather than in distinguishing the cause of a symptomatic shoulder.

Huge, well defined erosions may also occur as a result of the synovial hypertrophy of haemophilia and, less commonly, of pigmented villonodular synovitis.

Degenerative changes related to the shoulder joint occur in association with rotator cuff disease. This may lead to superior subluxation of the humeral head with bony impingement of the head on the under-surface of

Figure 30. AP view (same patient as in Figure 29). Progression of changes with more extensive erosions now also involving glenoid.


the acromio, r~ process. An osteophyte may appear at this site and bony eburnation is common. This is rarely initially associated with glenohumeral involvement, although this may subsequently appear.

True osteoarthritis occurs rarely in the glenohumeral joint but is more often seen in the acromioclavicular joint. The changes of osteoarthritis in both joints are similar to those in other joints, with narrowing of the joint space due to cartilage destruction, bony sclerosis, subarticular cysts and marginal osteophytosis. Changes in the glenohumeral joint are often due to underlying abnormality, such as previous trauma, rotator cuff disease, arthritis or congenital abnormality.

Non-erosive arthritis may also be due to the deposition of crystals of calcium pyrophosphate or hydroxyapatite, causing calcification within the shoulder joint. This is most commonly seen in the chondrocalcinosis (Figure 34) of calcium pyrophosphate deposition disease; this results in an arthritis which resembles osteoarthritis. Distinguishing features include the chondrocalcinosis, the presence of large cysts and prominent osteophytes and a tendency to progressive fragmentation and collapse of the humeral head, unusual in true osteoarthritis (Figure 35).

Figure 31. AP view. Syringomyelia causing progressive painless destruction of the joint with loss of joint space, prominent new bone formation and loose bony fragments with preservation of bone density. Wiring of previous fracture of acromion.


Figure 32. AP view. Osteomyelitis of the glenoid with extensive subarticular erosion, ~ortical destruction and extension into the joint space with inferior subluxation of the humeral head.

Figure 33. [67Ga]citrate isotope scan. Markedly increased uptake in left shoulder in patient with otherwise quiescent rheumatoid arthritis and fever. Infection confirmed by aspiration.


Figure 34. AP view. Early chondrocalcinosis over humeral head.

Figure 35. AP view. Severe changes of calcium pyrophosphate deposition disease, with prominent osteophytes, loss of joint space, irregularity and inferior subluxation of humeral head.


The intra-articular deposition of hydroxyapatite is less common than the extra-articular deposition commonly seen within the tendons of the rotator cuff, with which it is usually associated. This may cause a rapidly progressive, although often relatively painless, destructive arthropathy. It is distin- guished by decreased joint space, sclerosis, bony destruction with intra-articular debris and marked disorganization and deformity, aggravated by the coexistent rotator cuff disease (Figures 36-38). Cyst formation and osteophytes are infrequent. Hydroxyapati te and calcium pyrophosphate crystals may both be present in joint fluid and in these cases the severely destructive arthropathy tends to predominate.

Synovial chondromatosis may affect the shoulder joints relatively commonly (Figure 39). The loose bodies of synovial chondromatosis are initially not calcified and are therefore not radio-opaque. At this stage, arthrography may be essential to make the diagnosis. Even when some of the synovial masses have calcified by the time of presentation, many more may be revealed by arthrography. Secondary degenerative change is very common.

Figure 36. AP view (same patient as in Figure 35). Two years later: severe destructive changes in acromion and lateral clavicle, with resorption of osteophytes. Subsequent deposition of hydroxyapatite has led to idiopathic destructive arthropathy (atrophic osteoarthritis). Note large subdeltoid effusion. Crystal content of synovial fluid confirmed on both occasions by aspiration.


Other painful disorders

Adjacent disease may cause referred pain to the shoulder joint (Figure 40). Primary and secondary bone disorders occur here as elsewhere, with features characteristic of the disease rather than the site (Figures 40-44).

The most common indication for radioisotope scanning of the skeleton is in the assessment of malignant disease, usually for the detection of metastases. Both primary and secondary malignant disease of the bone will cause increased uptake of isotope on the late-phase scan. The most common differential diagnosis of markedly increased uptake is Paget's disease of bone. The pattern of isotope uptake may suggest this diagnosis~ rather than metastases, but there is rarely difficulty in differential diagnosis after taking a plain X-ray.

Pain in the shoulder region in the presence of malignant breast disease (usually ipsilateral) is a frequently encountered symptom. This may have several causes which are often difficult to distinguish on plain radiography. Degenerative disease of the rotator cuff affects this, as every other, group of patients. Radiotherapy of the breast often affects the bones comprising the shoulder joints, and metastatic disease, whether within the bone itself or the

Figure 37. AP view. Idiopathic destructive arthritis with huge subdeltoid effusion; changes indistinguishable from those in previous film with known pre-existing calcium pyrophosphate deposition disease.


soft tissues of the axilla, will also cause considerable pain. Algoneural dystrophy may follow mastectomy and disuse due to pain in the shoulder. The distribution of isotope uptake may help to distinguish these conditions from each other.

Malignant disease will cause a focal region of increased uptake. Other areas of the skeleton will often show similar increases in uptake of isotope, increasing the likelihood of this diagnosis. Postradiotherapy changes will lead to a larger area of increased uptake, corresponding only to the treated area. Thus, adjacent ribs will almost certainly also have increased uptake. Soft tissue malignant disease may show little change on scintigraphy and in these circumstances the investigation of choice is MRI.

Algoneural dystrophy may follow disuse due to trauma or other illness, such as myocardial infarction, as well as mastectomy. Patchy demineraliza- tion is present on plain films in both simple disuse and algoneural dystrophy, but soft tissue changes are only present in algoneural dystrophy. These may be predominantly either oedematous swelling or wasting. This will also usually lead to extensive abnormality on the bone scan with increased

Figure 38. AP view. End stage idiopathic destructive arthritis. Extensive bony destruction, superior subluxation of humeral head with resorption of the shaft due to impingement on the glenoid.


Figure 39. AP view. Large joint effusion and extensive calcification/ossification due to synovial chondromatosis.

Figure 40. AP view. Sclerotic expanding lesion within mid-clavicle causing pain in shoulder; young patient with histiocytosis X.


uptake, particularly in the periarticular regions, on both the early and late-phase images. The entire skeleton of the upper limb often shows these changes.

MRI may be invaluable in the assessment of secondary malignant disease, particularly in the follow-up of breast carcinoma; it may delineate otherwise undiagnosable soft tissue disease and help in the differential diagnosis of postradiotherapy changes and secondary disease. It is more sensitive than both plain radiography and isotope scanning in the early diagnosis of metastatic disease, particularly with the use of a sensitive sequence, such as STIR.

Figure 41. [99mTc]MDP isotope scan. Increased uptake at lateral end of right clavicle; unknown cause of pain.

Figure 42. AP view (same patient as in Figure 41). Expansile lytic lesion at lateral end of clavicle; aneurysmal bone cyst.

5 0 8 A. JONES AND I. WATT

The diagnosis of most bony malignant disease is made on the plain film characteristics but MRI is now the imaging method of choice in the local staging and follow-up of primary malignancy within the bones around the shoulder, as in all other regions of the skeleton. The anatomy of the lesion can be clearly seen in all planes and extension within bone marrow and into the soft tissues are shown optimally. CT of the chest and scintigraphy of the skeleton are used for the detection of more distant metastases.

In avascular necrosis of the humeral head, whatever the underlying cause, reduced uptake of isotope is present on both images. Scintigraphy, particularly with the use of a pinhole collimator and [99mTc]-labelled nanocolloid, is the most sensitive and earliest method of diagnosis of this condition in the shoulder, as in other joints.

Avascular necrosis may be clearly shown on MRI but only after it has been present for about 8 weeks. Although MRI is not as sensitive as scintigraphy in the early detection of this condition, it delineates the affected area more clearly. Like scintigraphy, it is unable to determine the underlying cause. In these circumstances, simultaneous coronal imaging of the contralateral asymptomatic shoulder may be more helpful than the more elegant images

Figure 43. AP view. Destructive expansile lesion of humeral head; plasmacytoma.


Figure 44. AP view. Lytic lesion of medial metadiaphysis with generally increased bony density; pre-epiphyseal fusion. Brown tumour in patient with hyperparathyroidism.

o b t a i n e d wi th the sma l l e r field of v iew n e e d e d for d i agnos i s o f r o t a t o r cuff d isease . M R I m a y show ea r l i e r changes t h a n s c i n t i g r a p h y in the s u b a c u t e ava scu l a r nec ros i s d u e to h igh doses of s t e ro ids (as fo l lowing r e n a l t r ans - p l a n t a t i o n ) .

REFERENCES

General reading Berquist TH (1986) Imaging of Orthopaedic Trauma and Surgery. Philadelphia: WB Saunders. Clark KC (1974) Positioning in Radiography, 9th edn. London: Heinemann Medical. Galasko CSB & Isherwood I (eds) (1989) Imaging Techniques in Orthopaedics. London:

Springer-Verlag. 2nd edn. Resnick D & Niwayama G (eds) (1988) Diagnosis of Bone and Joint Disorders.

Philadelphia: WB Saunders.

Calvert PT, Packer NP, Stoker D J, B ayley JIL & Kessel L (1986) Arthrography of the shoulder after operative repair of the torn rotator cuff. Journal of Bone and Joint Surgery 68B(1): 147-150.

Crass JR, Craig EV, Thompson RC & Feinberg SB (1984) Ultrasonography of the rotator cuff: surgical correlation. Journal of Clinical Ultrasound 12: 487-492.

Crass JR, Craig EV & Feinberg SB (1988) Ultrasonography of rotator cuff tears: a review of 500 diagnostic studies. Journal of Clinical Ultrasound 16: 313-327.

Deutsch AL, Resnick D, Mink JH et al (1984) Computed and conventional arthrotomography of the glenohumeral joint: normal anatomy and clinical experience. Radiology 153" 603-609.


Evancho AM, Stiles RG, Fajman WA et al (1988) MR imaging diagnosis of rotator cuff tears. American Journal of Roentgenology 151: 751-754.

Hardy DC, Vogler JB & White RH (1986) The shoulder impingement syndrome: prevalence of radiographic findings and correlation with response to therapy. American Journal of Roentgenology. 147: 557-561.

Kieft G J, Bloem JL, Rozing PM & Obermann WR (1988a) MR imaging of recurrent anterior dislocation of the shoulder: comparison with CT arthrography. American Journal of Roentgenology 150: 1083-1087.

Kieft GJ, Bloem JL, Rozing PM & Obermann WR (1988b) Rotator cuff impingement syndrome: MR imaging. Radiology 166: 211-214.

Lie S & Mast WA (1982) Subacromial bursography. Technique and Clinical Application. Radiology 144: 626-630.

Middleton WD, Edelstein G, Reinus WR, Melson GL, Totty WG & Murphy WA (1985) Sonographic detection of rotator cuff tears. American Journal of Roentgenology 144: 349-353.

Middleton WD, Kneeland JB, Carrera GF et al (1987) High resolution MR imaging of the normal rotator cuff. American Journal of Roentgenology 148: 559--564.

Seeger LL, Ruszkowski JT, Bassett LW, Kay SP, Kahmann RD & Ellman H (1987) MR imaging of the normal shoulder: anatomic correlation. American Journal of Roentgenology 148: 83-91.

Seeger LL, Gold RH & Bassett LW (1988b) Shoulder instability: evaluation with MR imaging. Radiology 168: 695-697.

Seeger LL, Gold RH, Bassett LW & Ellman H (1988a) Shoulder impingement syndrome: MR findings in 53 shoulders. American Journal of Roentgenology 150: 343-347.

Singson RD, Feldman F, Bigliani LU & Rosenberg ZS (1987) Recurrent shoulder dislocation after surgical repair: double-contrast CT arthrography. Radiology 164: 425-428.

Zlatkin MB, Reicher MA, Kellerhouse LE, McDade W, Vetter L & Resnick D (1988) The painful shoulder: MR imaging of the glenohumeral joint. Journal of Computer Assisted Tomography 12(6): 995-1001.

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Diagnostic imaging of the shoulder joint