Chapter 5: Upper Limb

Detailed Chapter Overview

Chapter 5 provides an exhaustive guide to the radiography of the upper limb, covering the digits, hand, wrist, and forearm. This region is one of the most frequently x-rayed due to its high incidence of injury. A mastery of its complex anatomy is therefore essential for any radiographer. The chapter meticulously details the bones of the hand and wrist, from the phalanges and metacarpals to the intricate arrangement of the eight carpal bones. Understanding the specific articulations and joint classifications—such as the sellar joint of the thumb or the ellipsoidal nature of the radiocarpal joint—is critical for performing specialized projections and evaluating image quality. The chapter emphasizes the radiographic significance of soft tissues, particularly the fat pads of the wrist and elbow, which serve as crucial indicators of underlying joint pathology. Positioning is a primary focus, with detailed, step-by-step instructions for a wide array of projections, from routine PA and oblique views to specialized techniques like the Stetcher method for the scaphoid and the Coyle method for the radial head. Technical factors are carefully considered, highlighting the need for low-to-medium kVp to achieve high-contrast images that display both soft tissue and fine bony detail. For each projection, stringent evaluation criteria are established, training the radiographer to critically assess for rotation, joint space visualization, and proper landmark alignment, ensuring that every image produced is of the highest diagnostic value.

In-Depth Study Guide

Anatomy of the Hand and Wrist

The hand and wrist are comprised of 27 bones, categorized into phalanges, metacarpals, and carpals.

Phalanges (Digits):

• There are 14 phalanges in each hand. Digits 2 through 5 each have three phalanges: **proximal, middle, and distal**.
• The first digit (thumb) has only two phalanges: **proximal and distal**.
• Each phalanx consists of a head (distal end), a body (shaft), and a base (proximal end).

Metacarpals:

• Five metacarpals form the palm of the hand. They are numbered 1 through 5, starting with the thumb side.
• Like phalanges, they consist of a distal head, a body, and a proximal base. The metacarpal heads are commonly known as the "knuckles".

Carpals:

The eight carpal bones of the wrist are arranged in two transverse rows.

• Proximal Row (from lateral to medial): Scaphoid, Lunate, Triquetrum, Pisiform. The pisiform is a small, pea-shaped bone situated anterior to the triquetrum.
• Distal Row (from lateral to medial): Trapezium, Trapezoid, Capitate, Hamate. The hamate is distinguished by its prominent hook-like process, the hamulus.
• The **scaphoid** is the most frequently fractured carpal bone. The **capitate** is the largest carpal bone.
• A helpful mnemonic for the carpals (lateral to medial, proximal then distal) is: "Some Lovers Try Positions That They Can't Handle".

Anatomy of the Forearm and Distal Humerus

• Radius: The bone on the lateral (thumb) side of the forearm. Proximally, it features the head, neck, and radial tuberosity. Distally, the **styloid process** is a key landmark.
• Ulna: The bone on the medial (pinky) side of the forearm. Proximally, it forms the main part of the elbow joint with the **olecranon process** and **trochlear notch**. Distally, it has a head and a styloid process.
• Distal Humerus: The distal end of the humerus articulates with the radius and ulna. Key structures include the medial and lateral epicondyles, the **trochlea** (articulates with ulna), and the **capitulum** (articulates with radius).

Joints of the Upper Limb

All joints of the upper limb are classified as synovial (freely movable) and diarthrodial. They are further classified by their type of movement.

• Interphalangeal (IP) Joints: Ginglymus (hinge) joints. Allow only flexion and extension.
• Metacarpophalangeal (MCP) Joints: Ellipsoidal (condyloid) joints. Allow flexion, extension, abduction, and adduction.
• Carpometacarpal (CMC) Joints:
  • The 1st CMC joint (thumb) is a **sellar (saddle)** joint, allowing a wide range of motion.
  • The 2nd-5th CMC joints are plane (gliding) joints with limited movement.
• Radiocarpal (Wrist) Joint: An ellipsoidal joint, formed by the articulation of the radius with the scaphoid and lunate.
• Elbow Joint: A ginglymus (hinge) joint comprised of three individual joints between the humerus, radius, and ulna.

Radiographically Important Soft Tissues

Fat pads are collections of soft tissue that can be visualized on radiographs. Their displacement can be the only indication of an occult (hidden) fracture.

• Wrist Fat Stripes:
  • Scaphoid Fat Stripe: Located laterally to the scaphoid. Its absence or displacement may indicate a scaphoid fracture.
  • Pronator Fat Stripe: Located on the anterior aspect of the distal radius. Displacement can indicate a fracture of the distal radius.
• Elbow Fat Pads: Displacement of the anterior and posterior fat pads of the distal humerus is a reliable indicator of joint effusion, which is often caused by an intra-articular fracture (e.g., radial head fracture).

Positioning and Technical Factors

• kVp Range: A low-to-medium kVp (50-70 kV) is used for the upper limb to produce high contrast (short-scale) images, which provide excellent visualization of bone detail.
• SID: A standard SID of 40 inches (102 cm) is used.
• Patient Care: Always explain the procedure. Handle injured parts with care, supporting the limb at both joints. Place markers and collimate accurately.

Routine and Special Projections

Digits (2-5)

• PA, Oblique, and Lateral: The three standard projections. The oblique is performed with a 45-degree foam wedge. The lateral is performed with the digit rotated 90 degrees from the PA.

Thumb (Digit 1)

• AP and Lateral: The PA hand position places the thumb in a natural oblique, so an AP projection is required to see the joint spaces open.

Hand

• PA, Oblique, and "Fan" Lateral: The oblique is performed with the hand rotated 45 degrees. The fan lateral separates the phalanges to visualize individual bones, while a lateral in extension is better for localizing foreign bodies.

Wrist

• PA, Oblique, and Lateral: The oblique demonstrates the scaphoid and trapezium well. The lateral must have the radius and ulna superimposed.
• Special View (Stetcher Method): A PA projection with the wrist elevated on a 20-degree sponge or with a 20-degree CR angle toward the elbow. This elongates the scaphoid, freeing it from foreshortening and making fractures easier to see.

Forearm

• AP and Lateral: The hand must be supinated for the AP view to prevent the radius and ulna from crossing over. For the lateral, the elbow must be flexed 90 degrees. Both the wrist and elbow joints must be included.