The Shoulder Girdle and Thoracic Cage

THE SCAPULA

FIGURE 5-1, Premature appearance of the ossification centers of the acromion and coracoid in a 1-month-old child. The coracoid process is not usually seen until the third month or later, and the secondary center for the acromion is not usually seen until age 10 to 12 years.

FIGURE 5-2, The coracoid processes seen as separate bones in a 2-year-old child.

$FIGURE 5-3, Development of the acromion processes as separate centers in a 1-year-old girl. This appearance is not to be mistaken for the acromial fracture associated with child abuse.$

FIGURE 5-4, Normal appearance of the coracoid processes during growth. A, A 13-year-old boy before appearance of the secondary ossification center. B, A 15-year-old boy. Note secondary ossification centers for coracoid and acromion processes.

$FIGURE 5-5, Appearance of the ossification center of the coracoid process in adolescence before fusion occurs. It may be mistaken for a fracture. A, Axillary projection. B, Arm elevated.$

FIGURE 5-6, Two examples of the secondary apophysis of the tip of the coracoid process.

FIGURE 5-7, Nonunion of the ossification center of the distal coracoid. A, Plain film. B, CT scan.

FIGURE 5-8, Accessory ossification center at the synchondrosis at the base of the coracoid in a 14-year-old boy. A, AP projection. B, Abduction film.

FIGURE 5-9, The same entity as described in Figure 5-8 .

FIGURE 5-10, The normal closing acromial apophysis in a 13-year-old boy. The irregularity of the apophyseal line is normal. The distal end of the acromion ossifies irregularly in infants and may be misinterpreted as evidence of child abuse.

FIGURE 5-11, Normal irregularity of the acromion in a 12-year-old boy that was mistaken for a pathologic process.

FIGURE 5-12, Multiple centers of ossifications of the acromial apophysis in a 12-year-old girl on CT scan.

FIGURE 5-13, The apophysis of the acromion in a 14-year-old boy, shown in axillary projection. This apophysis closes at age 18 to 20 years.

FIGURE 5-14, Remnant of the line of closure of secondary ossification center for the acromion in an 18-year-old man.

FIGURE 5-15, Un-united accessory ossification center for the acromion in a 38-year-old man.

FIGURE 5-16, The same entity illustrated in Figure 5.15 .

$FIGURE 5-17, Two examples of the os acromiale. This secondary ossification center persists into adult life as a separate bone and is often mistaken for a fracture of the acromion process when seen in the axillary projection. It is usually, but not invariably, bilateral.$

FIGURE 5-18, The os acromiale seen in the tangential view of the scapula.

$FIGURE 5-19, A, Os acromiale visible on frontal film simulating a fracture. B, Axillary projection demonstrates the os acromiale.$

FIGURE 5-20, Un-united secondary apophysis of the coracoid in frontal projection.

FIGURE 5-21, Acromial pseudospur produced by positioning. A, AP projection. B, Patient has assumed a kyphotic position.

FIGURE 5-22, A 13-year-old boy showing the normal irregularity of the glenoid seen before the secondary centers develop.

FIGURE 5-23, The ring apophysis of the glenoid in a 10-year-old boy.

FIGURE 5-24, Two examples of remnants of the ring apophysis in adults.

$FIGURE 5-25, Secondary ossification centers for the glenoid, which should not be mistaken for fractures.$

FIGURE 5-26, Ossicle at inferior aspect of the glenoid fossa as a remnant of the ring apophysis. A, A 32-year-old man. B, A 57-year-old man.

FIGURE 5-27, Persistent glenoid apophysis.

FIGURE 5-28, Small ossicle at the superior margin of the glenoid in an adult. This may be mistaken for calcific tendinitis of the long head of the biceps tendon.

$FIGURE 5-29, Un-united portion of the glenoid apophysis seen in the axial projections may be mistaken for a fracture fragment.$

FIGURE 5-30, Persistence of the glenoid apophysis in an adult.

FIGURE 5-31, Small ossicle at the anterior margin of the glenoid.

FIGURE 5-32, Apparent lucencies in the neck of the scapula caused by end-on projection of the coracoid (←). Note the position of coracoid tip ( ).

FIGURE 5-33, The coracoid process seen in the oblique projection of the shoulder.

$FIGURE 5-34, The coracoid process projected over the glenoid, simulating a fracture.$

FIGURE 5-35, Three examples of developmental defects in the glenoid. Such defects may be similar in origin to the acetabular notch.

FIGURE 5-36, Normal excrescences of the lower margin of the neck of the scapula that may be mistaken for periostitis.

FIGURE 5-37, Normal radiolucency of the wing of the scapula, which may resemble a lytic lesion.

FIGURE 5-38, Normally wide acromioclavicular joint and apparent malalignment in a 14-year-old girl (←). This appearance, if not compared with the opposite side, may be mistaken for an acromioclavicular separation. Note also the secondary ossification center for the tip of the acromion process ( ).

FIGURE 5-39, Apparent widening of the acromioclavicular joint resulting from positioning. A, Anteroposterior projection with internal rotation. B, A 30 degree right posterior oblique projection with external rotation.

FIGURE 5-40, Same phenomenon as in Figure 5.39 . Note also the apparent malalignment of the clavicle and acromion (right).

FIGURE 5-41, Positioning of the arms in children may produce an appearance simulating acromioclavicular separation. A, External rotation. B, Internal rotation.

FIGURE 5-42, Variations in configuration of the acromioclavicular joint. A, In most normal individuals, the inferior aspect of the clavicle is at the same level as the inferior aspect of the acromion. B, C, In a small percentage of normal individuals, however, the distal end of the clavicle lies above, as in this case, or below the acromion and this appearance might be interpreted as an acromioclavicular separation. This variation emphasizes the value of examining both sides.

FIGURE 5-43, Unusually wide acromioclavicular joints in a normal individual. These measurements exceed the quoted normal range. Examination of both shoulders resolves the question of possible separation.

FIGURE 5-44, Two examples of secondary ossification centers (infrascapular bone) of the inferior angle of the scapula in 16-year-old boys. These usually fuse by age 20 years.

FIGURE 5-45, A, B, Failure of development of an apophysis at the angle of the scapula on the right.

FIGURE 5-46, Developmental notchlike defects on the superior margins of the scapulae.

FIGURE 5-47, A, B, Unusual notch on the lateral margin of the scapula, which is best seen on internal rotation.

$FIGURE 5-48, A, B, Bilateral simulated fractures of the upper margins of the scapulae.$

$FIGURE 5-49, A, B, Two examples of simulated fractures of the scapulae produced by the spine of the scapula.$

FIGURE 5-50, Clasplike cranial margin of the scapula, which produces a pseudoforamen. The thin sheet of bone that forms the fossa supraspinata appears to be absent.

FIGURE 5-51, Examples of calcification of the transverse superior ligament of the scapula.

FIGURE 5-52, A, B, Deep notch on the superior margin of the scapula (←). Note also partial formation of a coracoclavicular articulation ( ) in A .

FIGURE 5-53, Foramina-like defects in the superior border of the scapula.

FIGURE 5-54, Sclerotic margins of the scapular fossae.

FIGURE 5-55, Irregularity of the entity seen in Figure 5.54 .

FIGURE 5-56, Normal lucencies in the neck of the scapula that may be mistaken for destructive lesions. They probably represent the lucency of the cancellous bone of the glenoid marginated by the coracoid process.

FIGURE 5-57, Striking example of the entity shown in the preceding figure mistaken for a true lesion. Note that it is not seen on the straight frontal projection (top right).

FIGURE 5-58, Developmental defects of the scapula that may be mistaken for a pathologic process.

FIGURE 5-59, Fossa in the neck of the scapula.

FIGURE 5-60, “Fractures” of the scapula simulated by a superimposition of the free margin of the scapula.

FIGURE 5-61, Normal lateral curvature of the distal end of the scapula.

$FIGURE 5-62, Simulated fracture of the neck of the scapula produced by trabecular pattern.$

$FIGURE 5-63, Fat stripe of chest wall simulating a fracture of the scapula.$

$FIGURE 5-64, Two examples of vascular channels that might be mistaken for fractures.$

FIGURE 5-65, Prominent vascular channel in the wing of the scapula.

FIGURE 5-66, Two examples of articulations between the scapula and adjacent ribs.

FIGURE 5-67, Examples of the normal “vacuum” phenomenon in the shoulder joint.

$FIGURE 5-68, A, B, “Vacuum” phenomenon in both shoulder joints. When the lucency is seen overlying only bone, as in B, it may be mistaken for fracture.$