9.3 Shoulder Girdle
Key Takeaways
- AP shoulder with external rotation profiles the greater tubercle laterally; internal rotation profiles the lesser tubercle medially—both require correct hand position and inclusion of the entire shoulder girdle region ordered.
- Grashey (AP oblique) opens the glenohumeral joint in profile; scapular Y and axillary/inferosuperior projections assess dislocation direction and glenoid relationships.
- On scapular Y, anterior dislocation projects the humeral head beneath the coracoid; posterior dislocation projects it beneath the acromion—and AP alone can miss posterior dislocation.
- Clavicle exams use AP and AP axial (cephalic angle); AC joints are imaged bilaterally with and without weights when ordered and not contraindicated.
- Scapula AP (arm abducted) and lateral demonstrate body and processes; choose trauma-safe projections when fracture or dislocation limits movement.
9.3 Shoulder Girdle
Quick Answer: Shoulder imaging is a projection toolkit, not a single AP. External rotation AP shows the greater tubercle in profile; internal rotation AP shows the lesser tubercle. Grashey opens the glenohumeral joint. Scapular Y and axillary / inferosuperior projections decide dislocation direction. Clavicle needs AP + cephalic axial; AC joints are often bilateral with/without weights; scapula needs AP (arm abducted) and lateral. On the exam, posterior dislocation is the classic miss when only a poorly critiqued AP is accepted.
The shoulder girdle (proximal humerus, scapula, clavicle, AC and SC joints) is a high-mobility complex. General radiography must show bony relationships under stress positions the patient can safely achieve. RTR.4 procedure competence and RTR.6 analysis competence merge: wrong rotation hides the greater tubercle; wrong oblique closes the glenoid; missing a Y-view leaves dislocation direction ambiguous.
Shoulder — Routine & Special Projections
| Projection | Position & rotation | CR | Evaluation criteria |
|---|---|---|---|
| AP external rotation | Erect preferred; arm slightly abducted; hand supinated / epicondyles parallel to IR | 1 in (2.5 cm) inferior to coracoid (or mid-glenohumeral per protocol) | Greater tubercle in profile laterally; scapulohumeral joint visualized; proximal humerus, lateral 2/3 of clavicle, upper scapula |
| AP internal rotation | Back of hand against thigh / full internal rotation; epicondyles perpendicular to IR | Same centering | Lesser tubercle in profile medially; proximal humerus in lateral-like profile |
| AP oblique (Grashey) | Rotate body 35–45° toward affected side (posterior oblique); arm neutral or slightly abducted | Glenohumeral joint | Open glenoid cavity in profile; glenohumeral joint space visible without humeral head superimposition over glenoid |
| PA oblique scapular Y | Rotate 45–60° so mid-coronal plane of scapula is perpendicular to IR (affected shoulder against IR for PA oblique) | Scapulohumeral joint | Scapula forms a Y: vertical stem = body; upper limbs = acromion & coracoid; humeral head over glenoid if reduced |
| Inferosuperior axial (Lawrence) | Supine; arm abducted ~90° if possible; head turned away; IR above shoulder | Horizontal CR through axilla, 15–30° medially to glenoid | Glenohumeral relationship; coracoid points anterior; lesser tubercle often anterior; hill-sachs/impression defects may be seen |
| Transthoracic lateral (Lawrence) | Affected arm at side; unaffected arm raised; true lateral thorax | Surgical neck through thorax | Proximal humerus projected through thorax; used when abduction/rotation impossible |
Dislocation clues (must-know)
| Finding | Interpretation |
|---|---|
| Humeral head inferior to coracoid on scapular Y | Anterior dislocation (vast majority) |
| Humeral head inferior to acromion on scapular Y | Posterior dislocation |
| Humeral head centered over “Y” intersection | Likely reduced / normal alignment on that view |
| AP shows humeral head with internal rotation, vacant glenoid, or “lightbulb” appearance | Suspect posterior dislocation — obtain Y or axillary confirmation |
Anterior dislocations are common after abduction–external rotation trauma. Posterior dislocations are less common (seizure, electric shock, FOOSH with internal rotation) and are frequently missed on a single AP if the technologist and reviewer do not insist on an orthogonal projection. Your job is to produce the orthogonal view safely—not to diagnose in place of the radiologist—but exam stems test whether you recognize which image answers the clinical question.
Axillary vs transthoracic vs Y
- Axillary / inferosuperior: excellent glenohumeral relationship if the patient can abduct; contraindicated or modified if abduction risks further injury.
- Scapular Y: minimal arm movement; excellent for dislocation direction and for some proximal humeral/scapular relationships.
- Transthoracic: when the arm cannot leave the side and proximal humerus is the target; higher technique, breathing blur of lungs, careful collimation.
Clavicle
| Projection | Setup | CR | Evaluation |
|---|---|---|---|
| AP | Erect preferred, arms at sides | Mid-clavicle | Entire clavicle from SC to AC joints; minimal rotation |
| AP axial | Same; reduce lordosis if possible | Mid-clavicle angled 15–30° cephalad (thinner patients often need more angle toward 30°; larger patients less) | Clavicle projected above thorax/ribs; AC and SC joints included |
PA axial options exist (caudal angle with patient PA) in some departments—know the principle: angle to throw the clavicle off the lung apices and reduce superimposition. Trauma: do not force shoulder motion; AP and AP axial with the arm as found are standard.
AC Joints
| Projection | Setup | CR | Notes |
|---|---|---|---|
| Bilateral AP without weights | Erect, arms at sides | Midway between AC joints (or separate unilateral images) | Establish baseline joint spaces |
| Bilateral AP with weights | Equal weights in each hand (department protocol, often 2.5–5 kg / 5–10 lb) | Same | Demonstrates AC separation; contraindicated if fracture suspected or patient cannot hold weights safely |
Markers and “with/without weights” annotation are mandatory. Compare sides; unilateral imaging is used when bilateral is impractical, but bilateral remains the classic teaching standard for AC stress views.
Scapula
| Projection | Setup | CR | Evaluation |
|---|---|---|---|
| AP | Erect or supine; arm abducted to right angle, elbow flexed, hand supinated if possible (draws scapula laterally) | Mid-scapula (≈5 cm inferior to coracoid) | Entire scapula; lateral border free of rib superimposition as much as possible |
| Lateral (body of scapula) | Erect; arm position varies by body vs acromion/coracoid interest; body rotated until scapula true lateral (often 45–60°) | Mid-medial border of protruding scapula | Scapular body in profile; ribs and lung free of scapular body; acromion and coracoid relationships depending on arm placement |
Arm position on lateral scapula is purposeful: hand on opposite shoulder vs arm across chest vs arm overhead changes which processes superimpose. Follow the requisition (body vs acromion/coracoid process).
Putting Trauma Protocols Together
A typical “shoulder trauma” series in many Canadian departments includes:
- AP neutral (arm as found—do not force external rotation through a fracture).
- Scapular Y or transthoracic / axillary as the orthogonal view based on what the patient can do and what is ordered.
- Additional Grashey, clavicle, or scapular views if the injury pattern expands.
Care-provider overlay: Support the elbow, watch for neurovascular symptoms, never pull longitudinal traction unless directed by the authorized provider in a reduction setting, and communicate pain levels. Immobilization devices (slings, vacuum splints) stay on when protocol and image quality allow; remove only metal that obliterates the region of interest after assessing risk.
Technique & Image Quality
Shoulders and transthoracic projections often need higher kVp and sometimes grids; AEC chambers must match the anatomy under the photocell (center chamber over glenohumeral joint—not air medial to the thorax). Breathing technique for transthoracic laterals requires coaching: slow gentle breathing versus suspended respiration depending on protocol. Collimate to the shoulder girdle—do not default to a full chest field for a shoulder order.
Digital processing can equalize the thick shoulder and thin acromion region, but poor positioning (closed glenoid on a “Grashey,” rotated Y) cannot be fixed by the histogram. Critique before the patient leaves the room.
CAMRT Application Focus
- External vs internal rotation AP — identify which tubercle is in profile; if the stem shows a “lateral” proximal humerus on an AP label, the arm was internally rotated.
- Grashey — joint space open; if the humeral head still sits over the glenoid fossa face, rotation was insufficient.
- Dislocation direction — use Y or axillary anatomy, not guesswork from a single AP.
- Clavicle axial — cephalic angle projects clavicle above the apices; insufficient angle leaves the midshaft buried in thorax.
- AC weights — know when they are used and when fracture suspicion makes them inappropriate.
Master this projection library and Chapter 9 becomes a coherent upper-extremity block: distal injuries demand scaphoid-aware wrist work; mid-limb injuries demand joint-to-joint forearm/humerus coverage; proximal injuries demand dislocation-safe shoulder girdle views—all under Canadian RTR entry-to-practice expectations for general radiography skeletal procedures.
On an AP shoulder with the hand supinated and the epicondyles parallel to the IR, which structure should be demonstrated in profile?
A scapular Y projection shows the humeral head projected beneath the coracoid process. What does this indicate?
What is the primary purpose of the AP axial clavicle projection with a cephalic central-ray angle?
Which statement about the Grashey method is most accurate?