Upper Extremities
Elbow
Anatomy
Students should be able to identify the following structures on radiographic images:
Radius, ulna, humerus, head of the radius, base of the ulna, radial tubercle, capitulum, trochlea, humeral epicondyles, olecranon process, ulnar notch, radial neck, radial notch, trochlear notch, coronoid process, radial fossa, coronoid fossa, olecranon fossa
Routine Projections (ARRT Required)
Elbow – AP Projection
CR Location & Positioning
- SID: 40 inches (102 cm)
- Patient position: Seated at table, shoulder, elbow, and wrist in the same plane (entire limb parallel to tabletop).
- Adjustments: Fully extend the elbow, supinate the hand so the forearm is true AP. Lean laterally if needed until humeral epicondyles and anterior surface of elbow are parallel to IR.
- CR: Perpendicular to the elbow joint; centered midway between epicondyles.
- Pt. Instructions: Suspend breathing; remain still.
- Exposure: Moderate kVp (60–70) with adequate contrast to visualize both bony and soft-tissue detail; ensure soft-tissue visibility for fat-pad evaluation.
Evaluation Criteria
- Coverage: Distal humerus, proximal forearm, and open elbow joint centered to CR.
- Rotation checks: Epicondyles seen in profile (no rotation); radial head, neck, and tuberosity slightly superimposed over proximal ulna; open humeroradial and humeroulnar joint spaces.
- Motion checks: Sharp cortical margins and visible trabecular pattern confirm no motion.
- Technique checks: Even exposure across both bone densities; soft tissue and fat pads visible; no artifacts.
- Clinical aim: Evaluate for fracture/dislocation alignment, joint space narrowing, or pathology indicated by fat-pad displacement.
Elbow – Lateral Projection (Lateromedial)
CR Location & Positioning
- SID: 40 inches (102 cm)
- Patient position: Seated with shoulder, elbow, and wrist in same horizontal plane.
- Adjustments: Flex elbow 90°; forearm and humerus resting on same plane; hand in true lateral position (thumb up). Ensure epicondyles perpendicular to IR. Elevate wrist slightly if forearm is muscular to maintain true lateral alignment.
- CR: Perpendicular to the elbow joint; centered midway between epicondyles.
- Pt. Instructions: Suspend breathing; remain still.
- Exposure: Moderate kVp emphasizing soft-tissue detail to visualize fat pads; exposure must allow differentiation of anterior and posterior fat pads.
Evaluation Criteria
- Coverage: Distal humerus and proximal forearm fully included with elbow flexed 90°.
- Rotation checks:
- Epicondyles superimposed
- Radial head partially superimposing coronoid process
- Olecranon process in profile
- Radial tuberosity facing anteriorly
- Motion checks: Crisp cortical outlines; soft tissue not blurred.
- Technique checks: Visualization of anterior and supinator fat pads (posterior should not be visible unless pathology present); proper contrast for soft-tissue assessment.
- Clinical aim: Demonstrate alignment, displacement, effusion, or occult fractures.
Elbow – AP Oblique Projection (Medial Rotation)
CR Location & Positioning
- SID: 40 inches (102 cm)
- Patient position: Seated at table with arm extended and in contact with tabletop.
- Adjustments: From AP, pronate hand and medially rotate the arm until anterior surface of elbow forms a 45° angle to IR.
- CR: Perpendicular to the elbow joint, midway between epicondyles.
- Pt. Instructions: Hold still; suspend breathing.
- Exposure: Standard kVp range; adjust for forearm thickness; maintain uniform contrast.
Evaluation Criteria
- Coverage: Distal humerus and proximal forearm with open elbow joint centered to CR.
- Rotation checks:
- Coronoid process in profile
- Elongated medial epicondyle
- Ulna partially superimposed by radial head and neck
- Olecranon process within its fossa
- Motion checks: Sharp bone edges, no motion blur.
- Technique checks: Appropriate brightness/contrast to differentiate coronoid and surrounding structures.
- Clinical aim: Evaluate coronoid process and trochlear articulation; assess for fractures or osteophyte formation on the ulna.
Elbow – AP Oblique Projection (Lateral Rotation)
CR Location & Positioning
- SID: 40 inches (102 cm)
- Patient position: Seated at table, arm extended and supinated.
- Adjustments: From AP, laterally rotate hand and arm until posterior surface of elbow is 45° to IR; first and second digits contact table.
- CR: Perpendicular to the elbow joint, centered midway between epicondyles.
- Pt. Instructions: Suspend breathing; remain still.
- Exposure: Similar to AP; optimize contrast for visualization of radial head and capitulum.
Evaluation Criteria
- Coverage: Distal humerus and proximal forearm with open elbow joint.
- Rotation checks:
- Radial head, neck, and tuberosity free of superimposition by ulna
- Elongated lateral epicondyle
- Capitulum in profile
- Motion checks: Sharp bone and soft-tissue margins.
- Technique checks: Appropriate brightness and contrast across joint; no artifacts.
- Clinical aim: Demonstrate radial head and capitulum relationships; identify radial head or neck fractures.
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Hows & Whys of Elbow Radiography
Anatomy
- Which bone articulates most directly with the humerus at the elbow?
The ulna articulates with the trochlea of the humerus to form the primary hinge motion of the elbow. - Which structure of the radius articulates with the humerus?
The radial head articulates with the capitulum of the humerus. - What type of joint is the elbow?
A synovial hinge joint permitting flexion and extension. - What type of joint is the proximal radioulnar articulation?
A pivot joint allowing pronation and supination of the forearm. - What radiographic sign can indicate an occult elbow fracture?
Visualization of the posterior fat pad on a lateral projection.
Positioning
- Why must the shoulder, elbow, and wrist be in the same plane for the AP projection?
To prevent joint distortion and ensure the elbow joint is open and properly centered. - Why is the hand supinated for the AP projection?
Supination prevents the radius and ulna from crossing, giving a true AP view. - Why is the elbow flexed 90° for the lateral projection?
It shows the olecranon process in profile and keeps the posterior fat pad depressed, avoiding false indications of pathology. - Why is the hand placed in true lateral with thumb up for the lateral projection?
This ensures the forearm is in a true lateral position, producing superimposed epicondyles. - Why is the arm rotated medially for the medial oblique projection?
To visualize the coronoid process free of superimposition and profile the trochlea. - Why is the arm rotated laterally for the lateral oblique projection?
To separate the radial head, neck, and tuberosity from the ulna for clearer evaluation.
Technique & Image Evaluation
- How can you tell that the AP elbow is correctly positioned?
Epicondyles appear in profile and the joint space is open, confirming the limb was in the same plane. - How can you tell that the AP projection was not truly supinated?
The radius crosses over the ulna proximally, indicating pronation. - How can you tell the lateral projection is correctly positioned?
Epicondyles are superimposed, the radial head overlaps the coronoid process, and the olecranon is in profile. - How can you confirm correct medial oblique positioning?
The coronoid process is seen in profile with the trochlea; the medial epicondyle appears elongated. - How can you confirm correct lateral oblique positioning?
The radial head and neck are completely free of ulnar superimposition and the lateral epicondyle appears elongated. - How can you tell if motion occurred?
Loss of cortical sharpness or soft-tissue definition, especially at the fat pads. - How can you tell exposure factors were appropriate?
Bony cortices and fat pads visible without overexposure; consistent brightness across both humeral and forearm portions.
Clinical Applications
- Which projection best demonstrates the radial head and neck?
The AP lateral oblique projection. - Which projection best demonstrates the coronoid process in profile?
The AP medial oblique projection. - Why are fat pads important diagnostically?
Displacement of the posterior fat pad or distortion of the anterior fat pad suggests joint effusion or occult fracture. - Which projection provides the best assessment of anterior or posterior fracture displacement?
The lateral projection. - Why is it important to visualize both distal humerus and proximal forearm on each elbow image?
To ensure alignment and exclude combined injuries involving the humerus or radius/ulna.
