chapter 14

Introduction to the Wrist Chapter

  • Discussing the significance of the wrist joint compared to other parts of the upper extremity
  • Emphasis on understanding bones over muscles, though both are important
  • Importance of studying guides prior to class and how it helps engagement with class material

Overview of the Wrist Joint

  • Definition: The wrist joint is the articulation between the radius, the ulna, and the carpal bones.
    • The wrist is crucial for functional motion.
    • Motion is essential for many daily activities.

Anatomy of the Wrist Joint

  • Articulation details:

    • Radius and ulna interact with carpal bones
    • Articular disc located between the ulna and carpal bones, offering additional space
    • Olecranon process is a notable structure on the ulna

  • Carpal Bones:

    • Comprised of eight distinct bones: (not focusing on specific shapes)
    1. Scaphoid
    2. Lunate
    3. Triquetrum
    4. Pisiform
    5. Trapezium
    6. Trapezoid
    7. Capitate
    8. Hamate
    • Examination of the proximal row and distal row of carpal bones
    • Importance of knowing name and position, but not the intricate shapes unless specializing in hand therapy

Types of Joints in the Wrist

  • Key joints involved in wrist motion:
    • Radiocarpal Joint:
    • Articulation between the distal end of the radius and the proximal row of carpal bones (with the articular disc)
    • Biaxial joint allowing for flexion, extension, radial and ulnar deviation
    • Mid-carpal Joint:
    • Located between proximal and distal carpal bones
    • Articulation that supports joint motion
    • Carpometacarpal joints (between carpal bones and metacarpals)
    • Phalangeal joints (where metacarpals touch the phalanges)

Motion at the Wrist

  • Motion types and their definitions:
    1. Flexion and Extension
    • Flexion: 0 to 80 degrees; Extension: 0 to 70 degrees (less for extension).
    1. Radial Deviation (movement towards the thumb): 20 degrees;
    2. Ulnar Deviation (movement towards the pinky): 30 degrees.
  • Concept of circumduction as a combination of all joint movements.

Structural Characteristics of the Wrist

  • Distal end of the radius is concave.
  • The proximal carpal bones are convex.
  • Understanding SA to differentiate between convex and concave movement in wrist function.

Range of Motion and Stability

  • Closed Pack Position:
    • Occurs during full extension and slight radial deviation—everything tightly packed.
  • Open Pack Position:
    • Neutral wrist position, where movement is easier and less strain occurs on the ligaments.

Carpal Bones Preparation

  • An emphasis on learning the carpal bones and their specific locations and relations, utilizing mnemonics for retention:
    • Mnemonic example: "Sally Likes To Push The Toy Car Hard"
    • Corresponds to: Scaphoid, Lunate, Triquetrum, Pisiform, Trapezium, Trapezoid, Capitate, Hamate
  • How to approach labeling based on anatomical positioning and spatial organization of the wrist.

Bony Landmarks of the Humerus and Ulna

  • Medial and lateral epicondyles as attachment points for muscles controlling the wrist.
  • Overview of muscle attachments at the elbow that influence wrist motion:
    • Muscles affecting wrist flexion and extension originate from either the medial or lateral epicondyle.

Ligaments of the Wrist

  • Key Ligaments to Note:
    • Radial Collateral Ligament: Limits ulnar deviation, supports the radial side.
    • Ulnar Collateral Ligament: Limits radial deviation, supports the ulnar side.
    • Palmar Radiocarpal Ligament: Limits wrist extension.
    • Dorsal Radiocarpal Ligament: Limits wrist flexion.
    • Transverse Carpal Ligament: Forms a roof over the carpal tunnel and is relevant in carpal tunnel syndrome.

Carpal Tunnel Syndrome

  • Carpal tunnel syndrome is caused by compression of the median nerve, resulting in numbness or tingling.
  • It occurs often due to repetitive hand motions or swelling, especially during pregnancy.
  • Flexor retinaculum may be cut during surgery to relieve pressure around the median nerve, counteracting bowstringing.

Summary of Muscles Function in the Wrist

  • Common Flexor Tendon is on the medial epicondyle affecting flexors and median nerve.