Hand Vascular Anatomy and Arthrokinematics

Principles of Arthrokinematics

Arthrokinematics refers to the specific movements occurring between joint surfaces, such as roll and glide. When a joint moves, the surfaces do not simply slide; they roll (like a tire on a road) and glide (the sliding motion that prevents the bones from simply rolling off one another). The direction of these movements depends heavily on whether the moving surface is convex or concave.

Exam Tip: Remember that for most synovial joints, the glide occurs in the opposite direction of the roll when a convex surface moves on a stable concave surface.

Joint-Specific Arthrokinematics

The Forearm and Wrist

The transition from the forearm to the hand involves several distinct joint types:

• Distal Radioulnar Joint: This is a pivot joint where the ulnar notch of the radius moves on the ulnar head of the ulna. This allows for the rotation required for pronation and supination.

  

• Radiocarpal Joint: This is a condyloid joint where the proximal carpal row sits on the radius. Its movements follow specific patterns:
  • Palmar (volar) abduction: Anterior roll with a posterior glide.
  • Palmar (volar) adduction: Posterior roll with an anterior glide.
  • Radial/Ulnar movements: These involve corresponding radial/lateral or ulnar/medial rolls and glides.

The Thumb (1st CMC and 1st MCP)

The thumb is unique due to its high degree of mobility, facilitated by two different joint types:

• 1st CMC Joint: Located between the 1st metacarpal and the trapezium, this is a saddle joint.
  • Palmar abduction: Anterior roll with a posterior glide.
  • Palmar adduction: Posterior roll with an anterior glide.
• 1st MCP Joint: This is a condyloid joint between the base of the proximal phalanx and the head of the 1st metacarpal. It utilizes anterior/palmar rolls and glides or posterior/dorsal rolls and glides.

The Fingers (2nd-5th MCP and IP Joints)

The remaining digits rely on condyloid mechanics for flexion and extension:

• 2nd-5th MCP Joints: These are condyloid joints between the proximal phalanx and the metacarpal heads.
  • Abduction/Adduction: The direction of roll and glide depends on the specific digit and the surface geometry. For example, in the 2nd digit, abduction involves a lateral/radial roll and glide.
• Interphalangeal (IP) Joints: Including the PIP and DIP joints, these are also condyloid joints. They utilize anterior/palmar rolls and glides or posterior/dorsal rolls and glides during flexion and extension.

Clinical Note: In IP joints, flexion involves an anterior (palmar) roll and an anterior (palmar) glide, while extension involves a posterior (dorsal) roll and a posterior (dorsal) glide.