At which end of the radius is the radial head located?

Location of the Radial Head

The radial head is located at the proximal end of the radius bone, forming part of the elbow joint and superior radioulnar joint. 1, 2

Anatomical Details of the Radial Head

• The radial head is situated at the proximal end of the radius, where it articulates with:

  • The capitellum of the humerus (forming part of the elbow joint)
  • The lesser sigmoid notch of the ulna (forming the superior radioulnar joint) 3

• Anatomical characteristics:

  • Average height of the radial head: 0.91 cm at the medial end and 0.76 cm at the lateral end 2
  • Average diameter: 2.09 cm (anteroposterior) and 2.02 cm (transverse) 2
  • Most common shapes: circular (59%) or elliptical (34%) 2

Clinical Significance

The radial head has important clinical implications:

1. Safe Zone for Surgical Fixation

   • The radial head has a "safe zone" (non-articulating portion) located posterolaterally when the forearm is in full supination 3
   • This safe zone encompasses approximately 113 degrees of the radial head circumference 3
   • This area is crucial for surgical placement of hardware during fracture fixation 4

2. Radiocapitellar Articulation

   • The radius of curvature of the radial head's peripheral cartilaginous rim closely matches that of the capitellum 5
   • This congruent articulation is essential for proper elbow function and forearm rotation

3. Morphological Variations

   • The proximal radius shows different morphological types at the safe zone:
     • Type A: flat profile (25% of cases)
     • Type B: low concave curvature (64%)
     • Type C: marked concave curvature (11%) 6
   • These variations are important to consider during surgical fixation of proximal radius fractures

Practical Identification

For practical purposes, the radial head can be identified as:

• The proximal end of the radius (opposite to the distal end which has the radial styloid process)
• The circular/elliptical portion that articulates with both the humerus and ulna
• The portion that can be palpated on the lateral aspect of the elbow, especially during forearm rotation

Understanding the location and anatomy of the radial head is essential for proper diagnosis and management of elbow injuries, particularly distal radius fractures and radial head fractures.