1887

The shoulder joint and scapula

image of The shoulder joint and scapula
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Abstract

Shoulder lameness, although a common condition in the dog, can be difficult to localize. Even when the lameness has been localized to the shoulder, identifying the precise cause can be frustrating. Occasionally it will difficult to determine the whether a specific structure is normal or abnormal. Numerous anatomical variants of the skeletal system exist that can easily be diagnosed erroneously as disease. In such cases, it is often helpful to take a radiograph of the contralateral shoulder for comparison or to consult radiographs of other animals of similar age and breed. This chapter covers indications; radiography; normal anatomy; contrast studies; alternative imaging techniques and abnormal image findings.

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Figures

Image of 12.1
12.1 (a) ML view with scapula positioned dorsal to the vertebral column. (b) ML view with scapula superimposed on the cranial lung field. (c) CdCr view.
Image of 12.2
12.2 ML views of the shoulder joint. (a) Skeletally immature dog. (b) Skeletally mature dog: 1 = coracoid process; 2 = supraglenoid tubercle; 3 = glenoid cavity; 4 = acromion; 5 = scapular spine; 6 = humeral head; 7 = lesser tubercle; 8 = intertubercular groove; 9 = greater tubercle; 10 = humeral neck. (c) Skeletally immature cat. Note the presence of the clavicle.
Image of 12.3
12.3 CdCr views of the shoulder joint. (a) Positioning for the CdCr view of the shoulder. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission. (b) Skeletally mature dog: 1 = shoulder joint; 2 = greater tubercle; 3 = lesser tubercle; 4 = intertubercular groove; 5 = deltoid tuberosity; 6 = humeral shaft; 7 = acromion; 8 = supraglenoid tubercle; 9 = supraspinous and infraspinous fossae superimposed; 10 = scapular spine. (c) Cat. Note the presence of the clavicle.
Image of 12.4
12.4 CrPr-CrDiO view of the intertubercular groove. (a) Diagrams of positioning illustrating direction of the primary X-ray beam. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission. (b) Radiograph of the intertubercular groove in a skeletally immature dog.
Image of 12.5
12.5 Sketch of skeletally immature shoulder region, illustrating centres of ossification in an immature dog. A = supraglenoid tubercle; B = humeral head; C = greater tubercle. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission.
Image of 12.6
12.6 ML view of the shoulder joint of a skeletally immature dog. Note the physeal line of the supraglenoid tubercle (arrowed), which should not be mistaken for a fracture line.
Image of 12.7
12.7 ML view of the shoulder joint of a large dog. Note the rudimentary clavicle (arrowed).
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12.8 CdCr view of the shoulder joint of a large dog. Note the rudimentary clavicle, which is just visible as a mineralized structure medial to the humerus (arrowed).
Image of 12.10
12.10 Illustrations of the different bursae and pouches around the shoulder joint. (a) ML view. (b) CdCr view. 1 = acromial bursa of infraspinatus muscle; 2 = subtendinous bursa of infraspinatus muscle; 3 = synovial tendon sheath of coracobrachialis muscle; 4 = subscapular recess; 5 = supraspinous recess; 6 = intertubercular synovial tendon sheath. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission.
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12.11 Normal positive-contrast arthrogram in the dog. (a) ML view. (b) CdCr view.
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12.12 ML view of a negative-contrast arthrogram of a humeral OC lesion. The articular cartilage can be visualized but a distinction between a loose flap and thickened cartilage is not possible.
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12.13 ML view of a double-contrast arthrogram of a humeral OCD lesion. The detached flap is clearly visible.
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12.14 Mineralization of the supraspinatus tendon of insertion. (a) Plain radiograph. (b) Positive-contrast arthrogram. (c) Transverse CT image in a bone window. Two mineral-like opacities are visible within the supraspinatus tendon. The arthrogram is helpful in localizing the opacities to outside the intertubercular groove. On the transverse CT image the location and shape of these opacities is clearly defined.
Image of 12.15
12.15 Transverse CT image in a bone window of new bone formation in the bicipital groove (*) due to bicipital tenosynovitis.
Image of 12.16
12.16 Early proximal right humeral primary bone neoplasm. (a) ML view showing an area of bony lysis surrounded by sclerosis (arrowed). (b) Transverse CT image in which the extent and exact location of the lesion are better appreciated in the medial aspect of the humerus.
Image of 12.17
12.17 (a) Transverse and (b) sagittal arthro-CT images in a bone window, and (c) transverse and (d) sagittal T2-weighted arthro-MRI images of a normal shoulder. H = humerus; S = scapula; 1 = joint space; 2 = medial glenohumeral ligament; 3 = lateral glenohumeral ligament; 4 = caudal pouch; 5 = joint cartilage; 6 = biceps tendon/silhouette; 7 = biceps tendon sheath; 8 = supraspinatus tendon; 9 = infraspinatus muscle; 10 = subscapularis muscle; 11 = supraspinatus muscle.
Image of 12.18
12.18 T1-weighted MRI of an OCD lesion. The extent and severity of subchondral bone involvement can clearly be appreciated. Although discontinuity in the delineation of the caudal humeral head can be detected, the detached flap cannot be demonstrated.
Image of 12.19
12.19 Ultrasonographic images of a normal canine shoulder joint. (a) The humeral head is visible as a hyperechoic convex curvilinear line with a strong acoustic shadow, and the cartilage as an anechoic layer covered by the joint capsule and superficial muscles. The thickness of the articular cartilage is 0.6 mm. (b–c) Evaluation of the bicipital tendon sheath with (b) cross-sectional images at the level of the bicipital groove and (c) longitudinal images at the level of the attachment on the supraglenoid tubercle. Note the homogeneous structure of the normal biceps tendon.
Image of 12.20
12.20 Intra-articular avulsion fracture of the supraglenoid tubercle. (a) ML view. (b) CdCr view. Both views are necessary to evaluate the degree of displacement and the extent of the fracture.
Image of 12.21
12.21 ML view of the shoulder joint of an immature dog with an avulsion fracture of the supraglenoid tubercle. This fracture line should not be confused with the normal physis (see Figure 12.6 ).
Image of 12.22
12.22 Salter–Harris type I fracture of the proximal physis of the humerus in a cat. (a) ML view. (b) CdCr view. The two views are necessary to evaluate the full extent of the fracture.
Image of 12.23
12.23 Traumatic medial shoulder luxation in a dog. (a) ML view. (b) CdCr view. Note the fracture of the medial glenoid rim (arrowed), which will probably preclude closed reduction.
Image of 12.24
12.24 ML view of a positive-contrast arthrogram of a traumatic biceps tendon rupture. The arthrogram reveals leakage of contrast medium from the tendon sheath (arrowed) and loss of the normal proximal tendon filling defect. Effusion in the area of the caudal pouch can also be appreciated.
Image of 12.25
12.25 Longitudinal ultrasonographic view of a traumatic partial rupture of a biceps tendon. H = humerus; SGT = supraglenoid tubercle. Note the inhomogeneous and hypoechoic areas within the tendon (arrowed) in comparison with Figure 12.19c .
Image of 12.26
12.26 Congenital medial shoulder luxation in a 5-month-old Cavalier King Charles Spaniel. (a) ML view. (b) CdCr view. Note the flattened, abnormal form of the glenoid cavity.
Image of 12.27
12.27 Joint mice in the distal bicipital tendon sheath. (a) ML view. (b) CdCr view. Mineralized opacities within the supraspinatus muscle are also visible (arrowed).
Image of 12.28
12.28 ML view of a radiopaque joint mouse (arrowed) within the caudal pouch of the shoulder joint. The subchondral defect and OCD at the caudal aspect of the humeral head are clearly visible.
Image of 12.29
12.29 ML view of the shoulder of a dog showing a radiopaque joint mouse within the subscapular bursa (arrowed), which is an uncommon finding.
Image of 12.30
12.30 ML view of the shoulder, showing a small OC lesion with adjacent sclerosis involving the caudal aspect of the humeral head.
Image of 12.31
12.31 ML view of a classical shoulder OC lesion: flattening and an irregular radiolucent subchondral defect involving the caudal aspect of the humeral head can be seen.
Image of 12.32
12.32 ML view of the shoulder showing an OCD calcified cartilage flap overlying a subchondral defect.
Image of 12.33
12.33 (a) ML view of an osteochondrotic shoulder joint with a vacuum phenomenon; the articular cartilage is seen as a grey line superimposed on the subchondral bone. A joint mouse within the bicipital tendon sheath is visible (arrowed), as well as arthritic changes. (b) Close-up view.
Image of 12.34
12.34 ML shoulder view of a positive-contrast arthrogram of a clinical OCD lesion. Contrast medium is seen underneath the cartilage, which correlates with signs of pain and lameness. Artefactual air bubbles, mimicking small joint mice (arrowed), are also present. They have a round and smooth appearance, in contrast to real joint mice (see Figures 12.38 and 12.39 ).
Image of 12.35
12.35 ML shoulder view of a positive-contrast arthrogram of a non-clinical OC lesion. Thick cartilage is covering the subchondral defect with no contrast medium visible underneath the cartilage.
Image of 12.36
12.36 ML shoulder view of a positive-contrast arthrogram showing a detached cartilage flap lodged in the caudal pouch of the joint capsule (arrowed). In most cases, such a finding is associated with no clinical signs and can be left untreated.
Image of 12.37
12.37 ML shoulder view of a positive-contrast arthrogram showing a detached cartilage flap migrating towards the caudal pouch. Notice also the joint effusion. Such dogs are presented with an acute severe lameness.
Image of 12.38
12.38 ML view of a positive-contrast arthrogram with a joint mouse in the bicipital tendon sheath. This large joint mouse hinders the mechanical action of the biceps tendon and should be removed. Notice also that the cartilage flap looks fragmented (arrowed), meaning that smaller cartilage fragments may break off and form joint mice.
Image of 12.39
12.39 ML shoulder view of a positive-contrast arthrogram showing a joint mouse in the bicipital tendon sheath within a larger pouch (arrowed). This joint mouse is not hindering the biceps tendon and can be left untreated.
Image of 12.40
12.40 (a) Arthroscopic image of a confirmed OCD-like lesion at the glenoid cavity. (b) On the corresponding ML view of the shoulder this finding was not visible. (c) ML view of the shoulder of another dog, a 5-month-old Dobermann, with an osseous cyst-like lesion with adjacent sclerosis. Note the oval focal radiolucency just caudal to the acromion (arrowed). (c, Courtesy of Kragga Kamma Veterinary Hospital, Port Elizabeth, South Africa)
Image of 12.41
12.41 Longitudinal ultrasound image of a clinical OCD lesion. Note the presence of a second hyperechoic line at the bottom of the subchondral defect, which is a pathognomonic sign for the presence of a flap. 1 = joint effusion; 2 = normal articular cartilage cranial of the lesion; 3 = subchondral bed of the OCD lesion; 4 = hyperechoic line representing the detached flap.
Image of 12.42
12.42 ML view showing shoulder dysplasia. The glenoid cavity, because of the lack of support by a convex humeral head, has failed to form and has therefore developed into a convex surface, which is incongruent with the flattened humerus.
Image of 12.43
12.43 ML view of the shoulder showing a separate ossification centre of the caudal rim of the glenoid. It appears radiologically as a small radiopaque projection located just caudal to the glenoid. Note also the presence of an arthrotic spur at the caudal end of the humeral head, probably an incidental finding.
Image of 12.44
12.44 ML view of an ossification centre of the caudal rim of the glenoid with the appearance of a fracture. This dog was presented with clinical shoulder lameness.
Image of 12.45
12.45 (a) ML view of a positive-contrast shoulder arthrogram of the dog shown in Figure 12.44 , demonstrating impingement of the joint capsule. Lameness occurred when the fragment became loosely embedded in the joint capsule. The fragment is visible as a filling defect (arrowed). (b) The corresponding arthroscopic view shows an unstable fragment acting as a free body in the joint and causing synovitis and pain.
Image of 12.46
12.46 ML view of a shoulder joint with osteoarthrosis. It is characterized by osteophytes on the caudal glenoid rim and caudal articular margin of the humeral head. Osteophytes in the cranial (white arrow) and caudal (black arrow) intertubercular regions are present, as well as superimposed on the humeral head.
Image of 12.47
12.47 ML view of a shoulder joint with bicipital tenosynovitis. Sclerosis is visible along the bicipital groove and supraglenoid tubercle, as well as irregular delineation of the tubercle.
Image of 12.48
12.48 ML view of a shoulder joint with biceps tendon pathology. Radiological signs include dystrophic calcification of the tendon (arrowed) and new bone formation in the area of its attachment.
Image of 12.49
12.49 ML view of a shoulder joint showing an avulsion fracture of the attachment of the biceps tendon. Demineralization of the supraglenoid tubercle, osteophytes in the intertubercular groove and signs of osteoarthrosis are also visible.
Image of 12.50
12.50 ML view of a positive-contrast shoulder arthrogram demonstrating incomplete filling of the synovial sheath, filling defects and absence of delineation of the bicipital attachment due to partial avulsion of the biceps tendon. Effusion can also be appreciated.
Image of 12.51
12.51 The corresponding longitudinal ultrasonographic view of the shoulder of the patient in Figure 12.50 , demonstrating the fragment (arrowed) within the avulsed biceps tendon. Hum = humerus; SGT = supraglenoid tubercle.
Image of 12.52
12.52 Arthroscopic view of a chronic partial rupture of the biceps tendon. Fibres and hypertrophied stumps (arrowed) at the attachment of the biceps block the view. SGT = supraglenoid tubercle.
Image of 12.53
12.53 ML view of a proximal humerus with osteomyelitis. An osteolytic area surrounded by osteosclerosis and a proliferative periosteal reaction are visible. The radiological features should be differentiated from those of a primary bone neoplasm.
Image of 12.55
12.55 ML views of a shoulder joint with synovial osteochondromatosis. (a) The plain film radiograph shows multiple mineralized nodules within the joint capsule and its recesses. (b) Positive-contrast arthrogram. Radiolucent nodules appear as filling defects within the joint.
Image of 12.56
12.56 CdCr view of a shoulder joint with infraspinatus muscle contracture, revealing narrowing of the lateral scapulohumeral joint space (arrowed).
Image of 12.57
12.57 Transverse ultrasonographic image showing heterogeneous aspect of the supraspinatus muscle (white arrow). Hyperechoic foci, representing mineralization, are seen within the tendon (black arrow).
Image of 12.58
12.58 ML view of the shoulder joint of a cat suffering from hypervitaminosis A, revealing proliferative new bone formation around the shoulder joint.

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