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Chapter 4: Upper Limb

Overview of the Upper Limb Structures

  • The upper limb is broken down into different segments:

    • Shoulder Girdle: Connects the upper limb to the trunk.

    • Arm: Contains the humerus.

    • Forearm: Composed of the radius and ulna.

    • Hand and Wrist: Includes the various bones of the hand and wrist.

Bones of the Right Hand and Wrist

  • Bone Groups: The bones of the hand and wrist can be categorized into three main groups:

    1. Phalanges (fingers):

    • Distal Phalanx: The bone at the tip of each finger.

    • Middle Phalanx: The bone between the distal and proximal phalanges (not present in the thumb).

    • Proximal Phalanx: The bone closest to the hand.

    1. Metacarpals: The five long bones of the hand.

    2. Carpals: The eight small bones in the wrist.

    • Arrangement: From lateral to medial, along two rows:

      • Proximal row: Scaphoid, Lunate, Triquetrum, Pisiform.

      • Distal row: Trapezium, Trapezoid, Capitate, Hamate.

Joints of the Hand and Wrist

  • Interphalangeal (IP) Joints: Joints between individual phalanges, allowing bending and straightening movement.

  • Metacarpophalangeal (MCP) Joints: The articulation between the metacarpals and phalanges.

    • 1st MCP joint is specifically for the thumb and is classified as a condyloid joint.

  • Carpometacarpal (CMC) Joints:

    • 1st CMC joint (base of the thumb): Sellar (saddle) joint, allows for thumb opposition.

    • 2nd to 5th CMC joints: Plane (gliding) joints.

  • Types of Joints:

    • Ginglymus (hinge) joints for IP joints.

    • Ellipsoidal (Condyloid) joints for MCP joints.

Wrist Structure and Movements

  • Carpals - Posterior View: Details of carpal bones are vital for identification and imaging.

  • Carpal Canal (Sulcus): A tunnel through which the median nerve travels into the hand.

  • Wrist Movements:

    • Radial Deviation: Movement of the wrist toward the thumb side.

    • Ulnar Deviation: Movement of the wrist toward the little finger side.

Anatomy Review of the Forearm

  • Forearm Components: Comprised of the Radius and Ulna.

    • Key landmarks on the radius include:

    • Radial tuberosity: Site for muscle attachment.

    • Head and Neck of the radius.

    • Styloid process: Provides pivot points.

    • On the ulna, focus on:

    • Olecranon process: Forms the elbow's bony tip.

    • Coronoid process: Stabilizes the forearm.

    • Radial notch: Socket for the radius near the elbow.

Elbow Anatomy and Movements

  • Elbow Joint: Primarily a hinge joint formed by the articulation of the humerus, radius, and ulna.

    • Proximal Radioulnar Joint: A pivot type joint allowing for forearm rotation.

  • Movement Types:

    • Flexion: Bending at the elbow.

    • Extension: Straightening the arm.

  • Elbow Imaging:

    • Specific positioning for imaging different areas of the elbow is essential.

Positioning Principles for Upper Limb Imaging

  1. Gonadal shielding: Importance in preventing radiation exposure.

  2. Four-sided collimation: Improve image quality and limit radiation exposure.

  3. Long axis alignment: Position the long axis of the part to the long axis of the image receptor (IR).

  4. Visibility of Patient ID and side marker: Crucial for proper documentation.

Trauma Terminology and Implications

  • Dislocation: Complete displacement from joint alignment.

  • Subluxation: Partial dislocation, which may reduce range of motion.

  • Sprain: Injury to ligaments causing swelling and pain.

  • Fracture (fx): Different classifications:

    • Simple: Closed fracture without skin penetration.

    • Compound: Open fracture breaking through skin.

    • Comminuted: Bone shattered into multiple pieces.

    • Impacted: Fragments pressed into each other.

  • Common Injuries:

    • Mallet (Baseball) fracture: Distal phalanx avulsion.

    • Boxer's fracture: Fracture of the fifth metacarpal.

    • Colles’ fracture: Distal radius injury from a fall on the outstretched hand.

Positioning of Fingers, Hand, and Wrist

  • CR Positioning: Critical to ensure accurate imaging of specific areas:

    • PA Finger: Central ray (CR) directed to the proximal interphalangeal (PIP) joint.

    • Lateral Finger: Ensure digit is parallel to the IR with CR to PIP.

    • AP Thumb: CR to first metacarpophalangeal joint.

Evaluation Criteria for Imaging Protocols

  • Criteria for evaluating the quality of hand and wrist imaging, ensuring all parts are visible and appropriately positioned:

    • Entire digit or area demonstrated with proper alignment and exposure levels.

    • No rotation of phalanges or metacarpals evident.

Special Projections and Techniques for Examination

  • Various specialized methods include:

    • Gaynor-Hart Method: Angled CR for tangential views of the carpal canal.

    • AP Axial with Modified Robert’s Method: Identifying Bennett’s fractures with specific CR angling.

Quiz Questions for Self-Assessment

  1. Identify Carpal Bone Position: e.g., Locate the third carpal in proximal row from a lateral aspect.

  2. CR Angles: Understanding different required angles for various projections like the Gaynor-Hart and modified Roberts projections.

  3. Clinical Importance of Projections: Knowing which imaging methods are best suited to visualize specific fractures or injuries in the upper limb.

Conclusion

  • Proper understanding of the anatomical structures of the upper limb, joint classifications, imaging techniques, and trauma terminology are essential for effective diagnosis and treatment of upper limb conditions.