Anatomy of the Distal Humerus and Elbow Joint

Distal Humerus

• The expanded distal end of the humerus is called the humeral condyle.
• The medial condyle articulates with the ulna and is shaped like a pulley.
• The medial condyle contains a smooth depressed center called the trochlear sulcus.
• The lateral condyle, referred to as the capitulum, articulates with the radial head.
• The lateral epicondyle, a small projection located above the capitulum, is smaller than the medial epicondyle.
• The medial epicondyle, located on the medial edge of the distal humerus, is larger and more prominent than the lateral epicondyle.
• The coronoid fossa is an anterior depression that receives the coronoid process.
• The radial fossa, an anterior depression, is located lateral to the coronoid fossa and receives the radial head.
• The olecranon fossa, located posteriorly, receives the olecranon process when the arm is fully extended.

Elbow Joints

• The olecranon fossa is one of the structures that form the elbow joint.
• The proximal radioulnar joint is another joint that is located near the elbow.

Fat Pads

• The anterior fat pad is visible on the lateral elbow projection.
• Posterior fat pads are not typically visible on X-rays unless there is trauma or incorrect flexion.
• The supinator fat stripe may indicate a radial head or neck fracture.

Positioning Considerations

• The standard SID for elbow projections is 40 inches.
• Remove all artifacts or jewelry from the patient before radiographic procedures.
• Keep the shoulder and upper extremity on the same plane when positioning.

Routine Projections

• Common routine projections for the elbow include:
  • AP
  • Alternate AP – Partial Flexion
  • Lateral (external)
  • Medial (internal) Oblique
  • Lateral Oblique

AP Projection

• Clinical Indications: Fractures, dislocations, osteomyelitis, and arthritis.
• The elbow should be fully extended with the hands supinated.
• The patient may need to lean laterally for a true AP projection.
• The epicondyles should be parallel to the IR.
• CR is perpendicular to the IR and directed at the mid-elbow joint (3/4 inch distal to the midpoint of the epicondyles).

Alternate AP – Partial Flexion

• Clinical Indications: Fractures, dislocations, osteomyelitis and arthritis.
• Used when the elbow cannot be fully extended.
• Two projections are needed:
  • One with the forearm parallel to the IR.
  • One with the humerus parallel to the IR.
• CR: Perpendicular to the IR, directed at the mid-elbow joint.

Lateral (External) Oblique Projection

• Clinical Indications: Fractures and dislocations, primarily those involving the radial head and neck.
• Best visualizes the radial head and neck of the radius and capitulum of the humerus.
• Arm should be fully extended and on the same plane as the shoulder.
• Hand should be supinated and rotated laterally approximately 45 degrees.
• CR is directed at the mid-elbow joint.
• Evaluation Criteria: The radial head, neck, and tuberosity should not be superimposed by the ulna.

Trauma Axial Laterals (Coyle Methods)

• Clinical Indications: Fractures and dislocations, particularly when the elbow cannot be fully extended for medial and lateral oblique projections.
• Two projections are used:
  • Axial Lateromedial Projection (radial head best visualized)
  • Axial Mediolateral Projection (Coronoid process best visualized)

Axial Lateromedial Projection (Radial Head)

• Clinical Indications: Fractures and dislocations of the radial head.
• Elbow should be flexed 90 degrees if possible.
• Hand should be pronated.
• CR angled 45 degrees toward the shoulder, centered at the radial head and mid-elbow joint.
• Evaluation Criteria: The joint space between the radial head and capitulum should be open, and the radial head, neck, and tuberosity should be free of superimposition.

Axial Mediolateral Projection (Coronoid Process)

• Clinical Indications: Fractures and dislocations involving the coronoid process.
• Elbow should be flexed to 80 degrees, hand pronated.
• CR angled 45 degrees from the shoulder, into the mid-elbow joint.
• Evaluation Criteria: The anterior portion of the coronoid process is elongated in profile, the joint space between the coronoid process and trochlea should be open, and the radial head and neck should be superimposed by the ulna.

Radial Head Laterals (Coyle Method)

• Clinical Indications: Occult fractures of the radial head or neck.
• Elbow flexed 90 degrees.
• Upper extremity and shoulder remain on the same plane.
• Four projections are obtained:
  • Supinate hand and externally rotate as far as tolerated.
  • Place hand in true lateral position.
  • Pronate hand.
  • Internally rotate hand as far as tolerated.
• CR perpendicular to the IR, directed at the radial head.
• Evaluation Criteria: The radial tuberosity should be visualized in different positions, depending on the rotation of the hand.

Common Pathologies

• Osteomyelitis: Infection of the bone or bone marrow, often caused by bacteria and associated with trauma or surgery.
• Bursitis: Inflammation of the bursae, fluid-filled sacs located around joints, resulting in pain and limited range of motion.
• Osteopetrosis: Rare genetic disorder characterized by abnormally dense bone, often referred to as "marble bone."

This quiz explores the detailed anatomy of the distal humerus and its role in the elbow joint. It covers features such as the humeral condyle, epicondyles, and various fossae that contribute to joint movement. Test your understanding of these critical anatomical structures!