Chapter 4: Elbow Anatomy and Imaging

Overview

• Lecture focuses on Chapter 4 of the positioning book (9th edition).
• Elbow anatomy and imaging discussed, referencing images and details found in the textbook.

Anatomy of the Elbow

• Components: Distal humerus, proximal radius, and ulna form the elbow joint.
• Acronym: RCUT - Radius articulates with the Capitulum, Ulna articulates with the Trochlea.
• Key landmarks:
  • Medial and lateral epicondyles (important for positioning).
  • Coronoid fossa and radial fossa.
  • Radial tuberosity, proximal radioulnar joint.
  • Trochlear sulcus/groove.

AP Elbow (Page 133, Fig 4.16)

• Position: Hand supinated, palm out (anatomical position).
• Radius (thumb side), Ulna (fifth digit side).

Lateral Elbow View (Page 133)

• Key Features:
  • Radial head, olecranon process, semilunar notch.
  • Concentric arcs (trochlear sulcus, ridges of the capitulum/trochlea, trochlear notch).
• Indicator: Three concentric arcs assure a perfectly lateral elbow.
• Other elements:
  • Radial head, tuberosity, proximal radioulnar joint, olecranon process, distal humerus.
  • Posterior depression: Olecranon fossa (fits the olecranon process when arm extended).
  • Soft tissue detail: Fat pads (indicator of trauma).

Fat Pads (Page 137)

• Types: Anterior fat pad (C), posterior fat pad, supinator fat stripe (E).
• Indicator: Positive fat pad sign usually indicates trauma/facture.
• Example: Fracture of olecranon process visible with positive fat pad signs.

AP Elbow, Internal and External Rotation (Page 134)

• AP Elbow: Medial and lateral epicondyles, trochlea, radial head, neck, and tuberosity.
  • Indicator: Superimposition of radial head, neck, and tuberosity over the ulna.
• Lateral Elbow Demonstrates:
  • Medial and lateral epicondyles.
  • Trochlear sulcus, trochlear notch (second arc), double outer ridges of capitulum/trochlea.

Fat Pad Signs and Elbow Joint Types

• Joint Types:
  • Elbow: Synovial joint (contains synovial fluid), diarthrodial joint, hinge joint.
  • Proximal radioulnar joint: Pivot type (allowing pronation/supination).
• Fat Pad Signs: AP with superimposition vs. indicators of rotation (external vs. internal).

Routine Elbow Imaging

• Standard Positions:
  • AP
  • 45° internal/medial oblique
  • 45° external/lateral oblique
  • Lateral
• Indicators for Rotation:
  • External: Radial head, neck, tuberosity free of ulnar superimposition.
  • Internal: Coronoid process in profile.
• Technique: 70 kVp at 2 mAs.

Trauma Considerations

• Incomplete Extension:
  • Two AP views (humerus parallel, forearm parallel).
  • Central ray perpendicular to mid-elbow for both.
  • Common interview question: Handling patients with incomplete extension.
• Lateral Elbow:
  • Flexed to 90°, humerus and forearm parallel to IR.
  • Central ray at mid-elbow.

Marker Placement and Imaging Details

• AP View: Marker lateral to part (thumb side is lateral).
• Lateral View: Includes humerus, forearm flexion, and soft tissue.
• Ensuring Correct Plane:
  • Shoulder, elbow, and wrist must be in the same plane for all positions (adjust table or patient position).
• Additional Views (Page 173-174): For trauma (Coyle method) or radial head/neck fractures.

Key Takeaways

• Ensure proper alignment and rotation indicators for accurate imaging
• Identify fat pad signs indicative of trauma
• Use the correct imaging technique and marker placement
• Adjust positioning based on patient’s ability to extend the elbow