Anatomy and Radiographic Procedures of the Shoulder Girdle

Exam Tip: When evaluating radiographic images of the shoulder, always consider the proximal humeral anatomy in conjunction with the girdle. Even though the humerus is not part of the girdle, its relationship to the scapula is critical for diagnosing shoulder joint issues.

The Shoulder Joint

The articulation between the scapula and the humerus is known as the shoulder joint. This is a highly mobile joint that allows for a vast range of motion.

• Anatomical Classification: It is a synovial joint.
• Functional Classification: It is a diarthrodial joint.
• Structural Type: It is a ball-and-socket type joint.

Radiographic Procedures and Guidelines

Performing radiographic procedures on the shoulder girdle requires careful patient positioning and technical precision to visualize specific structures like the AC joints, clavicle, or scapula.

General Procedural Guidelines

Before beginning any shoulder procedure, certain standard protocols must be followed to ensure image quality and patient safety:

• Patient Preparation: Remove all radiopaque artifacts, such as jewelry or clothing fasteners (e.g., bra hooks).
• Positioning: Patients can be positioned upright or recumbent; however, clinician priority should always be patient comfort.
• Technical Factors: The standard Source-to-Image Receptor Distance (SID) is 102 cm (40 inches).
• Identification: Correct right or left side markers must be included in the final image and should not be added via digital annotation later.
• Radiation Protection: Use close collimation and appropriate gonad shielding.

Routine Projections of the Shoulder

Different views are used depending on the suspected pathology:

1. AP Projections: These can be performed in internal rotation, external rotation, or a neutral position.
   • In Internal Rotation, the lesser tubercle is seen in profile pointing medially.
   • In External Rotation, the greater tubercle is seen in profile on the lateral aspect of the humerus.
2. AP Oblique (Grashey Method): This view is specifically designed to visualize the scapulohumeral joint with an open joint space.
3. PA Oblique (Scapular Y): This is a vital view for diagnosing shoulder dislocations. In a normal shoulder, the humeral head is superimposed over the junction of the "Y" formed by the acromion and coracoid process.
4. Inferosuperior Axial (Lawrence Method): This method uses a horizontal central ray to project the AC joint, acromion, and the humeral head.

Specialized Projections

• AC Joints (Pearson Method): To evaluate for dislocation or separation of the AC joints, an upright AP bilateral projection is used. Often, two exposures are made: one without weights and one with weights affixed to the arms to demonstrate the functional stability of the joint.
• Clavicle Projections: Common views include AP, PA, and axial projections (AP or PA axial). PA projections are often preferred due to reduced Object-to-Image Receptor Distance (OID) and improved image quality.
• Scapula Projections: Routine views include AP and Lateral projections. The lateral scapula view is used to demonstrate the lateral and medial borders of the scapular body.

Clinical Note: For trauma cases where the patient cannot move their arm, the AP Neutral position is used, leaving the arm in its position of comfort, often with the palm resting against the thigh.