Week 8: Shoulder Girdle Anatomy

• The shoulder girdle consists of the clavicle and scapula.
• The shoulder girdle articulates with:
  • Head of the humerus at the shoulder joint
  • Manubrium of the sternum at the sternoclavicular (SC) joint
  • Each other at the acromioclavicular (AC) joint
• The shoulder girdle connects the upper limb to the trunk of the body.
• The humerus is not considered part of the shoulder girdle.
• Proximal humeral anatomy is considered in the evaluation of shoulder joint images because the upper portion articulates with the shoulder girdle.
• The shoulder joint is a diarthrodial classification by function
• The shoulder joint is a synovial classification by anatomy (structure).
• The shoulder joint is a ball-and-socket type, capable of all motions.

Clavicle

• The clavicle is classified as a long bone
• It lies just above the first rib.
• The acromial extremity (lateral end) articulates with the acromion on the scapula at the AC joint.
• The sternal extremity (medial end) articulates with the manubrium of the sternum at the SC joint.
• The clavicle has a double curve to the body
• The curve of the clavicle is more pronounced in males than in females

Scapula

• Classified as a flat bone.
• Forms the posterior portion of the shoulder girdle
• Triangular in shape.
• The scapula has two surfaces:
  • Costal (anterior)
  • Dorsal (posterior)
• The scapula has three borders:
  • Lateral
  • Medial
  • Superior
• The scapula has three angles:
  • Superior
  • Inferior
  • Lateral

General Procedural Considerations

• Patient preparation requires the removal of radiopaque artifacts from the anatomy of interest such as jewelry or bra hooks
• Patient possessions should be secured in a designated manner and location
• Shoulder procedures can be performed in upright or recumbent positions, with patient comfort the priority
• The textbook contains recommended radiation field parameters and most common IR sizes for shoulder girdle procedures
• Source image receptor distance (SID) is standardized as part of the procedural protocol at 40' or 102 cm.
• It is important to consider the use of lead to absorb scatter and how it affects side marker placement when using ID markers
• Avoid using digital annotation to place side markers on images
• Patients should be protected from unnecessary radiation through proper collimation and lead shielding between the gonads and radiation source, when necessary
• Other radiation protection measures include close collimation and optimum technique factors.

Radiologic Procedures for AC Joints

• AP projection (Pearson method)

AP AC Joint - Pearson Method

• An upright position is required because a supine position will reduce dislocation, if present.
• For part position:
  • Arms should be hanging by the side, unsupported
  • Shoulders should be in the same horizontal plane
• Make separate exposures:
  • One without patient’s arms weighted
  • One with weights affixed to patient’s arms
• For the central ray(CR):
  • Perpendicular to the midline of the body at the level of AC joints if a bilateral image is obtained
  • Perpendicular to individual AC joints if separate images are required
• For Collimation:
  • Single: 6 × 8 inches (15 × 20 cm)
  • Bilateral: 6 × 17 inches (15 × 43 cm)
• Image evaluation criteria:
  • Evidence of proper collimation
  • Both AC joints, with and without weights, entirely included on one or two single images
  • No rotation or leaning by patient
  • Right or left and weight or nonweight markers
  • AC joint separation, if present, clearly seen on the images with weights

Essential Projections for the Clavicle

• AP
• PA
• AP axial
• PA axial.
• PA projections are preferred because of reduced OID and improved image quality
• AP projections are used on recumbent patients.
• All clavicle projections use the same collimation: 8 × 12 inches (18 × 30 cm) radiation field.
• Include 1.5 inch (3.8 cm) above the shoulder, 1 inch (2.5 cm) beyond the lateral aspect of the shoulder, and the entire clavicle

AP Clavicle

• Patient can be upright or supine.
• Center the clavicle to the image receptor (IR).
• Position the arms at the sides and shoulders in the same horizontal plane.
• The central ray (CR) should be perpendicular to the midshaft of the clavicle.
• An exposure should be made at the end of exhalation

PA Clavicle

• The patient position is Standing, seated upright facing vertical Bucky, or prone
• Center the clavicle to the midline of the Bucky
• The part position is achieved with Arms relaxed by the patient’s side
• Shoulders are placed in the same transverse plane
• The CR is perpendicular, exiting the midshaft of the clavicle
• Make exposure upon the end of exhalation

AP Axial Clavicle

• If possible, the patient position is upright, lordotic
• If lordotic position is not possible, position the patient supine with their shoulders in the same plane
• The part position is:
  • Center clavicle to center of the IR
  • Arms along the sides of the body
  • Shoulders to in the same horizontal plane
• For the central ray (CR):
  • Standing: Angle 15 to 30 degrees cephalic
  • Standing and Lordotic position: Angle 0 to 15 degrees cephalic
  • Supine position: Angle 15 to 30 degrees cephalic
  • Amount of angle varies with patient thickness, thinner patients require = more angle
  • The CR enters the midshaft of clavicle
• Make exposure at the end of full inspiration

PA Axial Clavicle

• The patient position is Standing facing the vertical grid device or prone
• For the central ray (CR): Angle15 to 30 degrees caudal, exiting midshaft of the clavicle
• Image evaluation criteria include: --Evidence of proper collimation, -- Entire Clavicle centered on the image, --Lateral half of the clavicle above the Scapula superimposing the thorax, --Bony trabecular detail and surrounding soft tissue

AP/PA Axial Clavicle

• Image evaluation criteria:
  • Evidence of proper collimation
  • Two-thirds of the clavicle (lateral) projecting above the ribs and scapula with the end (medial) superimposing the thorax
  • Clavicle in a horizontal orientation
  • Entire clavicle along with AC and SC joints
  • Bony trabecular detail and surrounding soft tissues

Radiologic Procedures for the Scapula

• Essential Projections: - AP - Lateral

AP Scapula

• The patient position is:
  • Consider the patient's comfort first
  • Upright or supine
• The part position:
  • Center affected scapula to grid
  • Abduct arm to right angle
  • Flex elbow
• CR:
  • Perpendicular to point 2 inches (5 cm) inferior to coracoid process
• Collimation:
  • Radiation field 10 × 12 inch (24 x 30 cm)
  • Include 1.5 inch (3.8cm) above the shoulder, 2 inches (5cm) beyond the lateral aspect of the shoulder, the lateral half of the clavicle, and 1 inch (2.5cm) below the inferior angle of the scapula
• Exposure: during slow breathing to obliterate lung detail

Lateral Scapula

• The patient position is
  • Standing or seated in RAO or LAO
  • 45 to 60 degrees anterior oblique position
  • Posterior oblique positions can be used, but scapula will be magnified
  • Affected scapula is in contact and centered to grid
• Part position to demonstrate acromion and coracoid
  • Flex elbow and place back of hand on posterior thorax
  • Adjust to ensure humerus does not overlap scapula
  • Lateral and medial borders of body perpendicular to the plane of the IR
• Part position to demonstrate body
  • Extend arm upward and rest forearm on the head
  • Bring arm across upper anterior chest and grasp opposite shoulder
  • Lateral and medial borders of body perpendicular to the plane of the IR
• CR:
  • Perpendicular to midmedial border of the scapula
• Collimation:
  • Radiation field of twelve (12) inches (30cm) in length on the collimator, 1.5 inch (3.8cm) above the shoulder, and 1 inch (2.5 cm) beyond the lateral shadow.

Image Evaluation Criteria for an AP Scapula

• Evidence of proper collimation
• Lateral portion of the scapula free of superimposition from the ribs
• Scapula horizontal and not slanted
• Scapular detail through the superimposed lung and ribs (shallow breathing should help obliterate lung detail)
• Acromion and inferior angle
• Bony trabecular detail and surrounding soft tissues

Image Evaluation Criteria for a Lateral Scapula

• Evidence of proper collimation
• Lateral and medial scapular borders superimposed
• No superimposition of the scapular body on the ribs
• No superimposition of the humerus on the area of interest
• Inclusion of the acromion and inferior angle
• Bony trabecular detail and surrounding soft tissues