Skeletal Anatomy of the Upper Extremity — Limited X-Ray / Radiologic Technology

Objective. Students will identify all named bones and major bony landmarks of the hand, wrist, forearm, elbow, humerus, and shoulder girdle on anatomical diagrams and radiographic images.

Introduction

A thorough knowledge of upper extremity skeletal anatomy is essential before you position a single patient. You must know what you are imaging, recognize what you see on the resulting radiograph, and communicate accurately with radiologists, physicians, and other healthcare team members. This lesson covers every named bone and major bony landmark from the fingertips to the shoulder girdle.

The Hand: Phalanges and Metacarpals

Each finger (digits 2–5) contains three phalanges: the proximal, middle, and distal phalanx. The thumb (digit 1) has only two: a proximal and a distal phalanx. Each phalanx has a base (proximal end), a shaft (body), and a head (distal end). The joints between phalanges are the interphalangeal (IP) joints; in digits 2–5, these are named the proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints. The thumb has a single interphalangeal (IP) joint.

The metacarpals are five long bones numbered 1–5 from the thumb side (radial side) to the little-finger side (ulnar side). Each metacarpal also has a base, shaft, and head. The joints between the metacarpal heads and the proximal phalanges are the metacarpophalangeal (MCP) joints.

The Wrist: Carpal Bones

Eight carpal bones are arranged in two rows. The proximal row, from radial to ulnar, consists of the scaphoid (navicular), lunate, triquetrum, and pisiform. The distal row, from radial to ulnar, consists of the trapezium, trapezoid, capitate, and hamate. A helpful mnemonic is: "She Looks Too Pretty, Try To Catch Her." The hamate has a distinctive hook-shaped projection called the hamulus (hook of the hamate), visible on a carpal tunnel projection. The scaphoid is the most commonly fractured carpal bone and is particularly important because its blood supply makes it vulnerable to avascular necrosis if a fracture is missed.

The joint between the proximal carpal row and the radius/ulna is the radiocarpal (wrist) joint. The joint between the two carpal rows is the midcarpal joint.

The Forearm: Radius and Ulna

The forearm contains two bones. The radius is on the thumb (lateral) side. At its proximal end is the radial head and radial neck; just below the neck is the radial tuberosity, where the biceps tendon attaches. The distal radius has a styloid process on the lateral side and the ulnar notch where it articulates with the ulna. The radius bears most of the weight transmitted from the wrist.

The ulna is on the little-finger (medial) side. Its proximal end features the olecranon process (the bony point of the elbow) and the coronoid process, which together form the trochlear notch (semilunar notch)—the deep concavity that grips the humerus. The ulnar styloid process projects from the distal end. The joint between the proximal radius and ulna is the proximal radioulnar joint (PRUJ); distally, the distal radioulnar joint (DRUJ) allows pronation and supination.

The Elbow

The elbow is formed by three articulations involving the distal humerus and the proximal radius and ulna. The distal humerus presents two rounded projections: the medial epicondyle and the lateral epicondyle. Between them, the articular surface has two parts: the trochlea (medial, spool-shaped, articulates with the ulna) and the capitulum (lateral, rounded, articulates with the radial head). Above the trochlea on the anterior surface is the coronoid fossa (receives the coronoid process in flexion); on the posterior surface is the olecranon fossa (receives the olecranon in extension).

The Humerus

The humerus is the single bone of the upper arm. Its proximal end includes the head (articulates with the glenoid cavity), the anatomical neck (the groove just below the head), the greater tubercle (lateral), and the lesser tubercle (anterior/medial). The intertubercular (bicipital) groove runs between the two tubercles. The surgical neck is the narrowed region below the tubercles and is a common fracture site. The shaft of the humerus has a roughened area called the deltoid tuberosity where the deltoid muscle attaches. Distally, the humerus widens into the epicondyles and articular surfaces described above.

The Shoulder Girdle: Scapula and Clavicle

The scapula (shoulder blade) is a flat, triangular bone lying on the posterior thorax. Key landmarks include the body, three borders (medial/vertebral, lateral/axillary, and superior), three angles (superior, inferior, and lateral/glenoid angle), the glenoid cavity (the shallow socket of the glenohumeral joint), the coracoid process (projects anteriorly), and the spine of the scapula (posterior ridge). The spine extends laterally to become the acromion process, which forms the roof of the shoulder and articulates with the clavicle at the acromioclavicular (AC) joint.

The clavicle is an S-shaped bone with a sternal end (articulating with the manubrium at the sternoclavicular joint) and an acromial end (articulating with the acromion). It is the most commonly fractured bone in the body.

Safety and Scope of Practice Notes

Always verify patient identity and the correct side (right or left) before positioning. Misidentifying laterality can result in imaging the wrong extremity—a patient safety error. When handling bone models or positioning patients, be alert to trauma and suspected fractures: never force a limb into a position that causes pain. Immobilization devices or angled tube techniques can achieve diagnostic projections without moving an injured extremity. Accurate anatomy identification directly supports radiation protection: knowing the exact region to be imaged allows precise collimation, reducing unnecessary exposure to the patient and reducing scatter to yourself.

Key terms10

Carpal bonesThe eight small bones of the wrist arranged in two rows: proximal (scaphoid, lunate, triquetrum, pisiform) and distal (trapezium, trapezoid, capitate, hamate).

Olecranon processThe large, posterior projection at the proximal end of the ulna that forms the bony point of the elbow and fits into the olecranon fossa of the humerus in full extension.

Radial tuberosityA roughened oval prominence on the medial aspect of the proximal radius, just below the radial neck, serving as the attachment point for the biceps brachii tendon.

Trochlear notch (semilunar notch)The deep, C-shaped concavity on the proximal ulna formed by the olecranon and coronoid processes; it articulates with the trochlea of the humerus.

Greater and lesser tuberclesTwo bony prominences on the proximal humerus. The greater tubercle is lateral and serves as an attachment for rotator cuff muscles; the lesser tubercle is anterior/medial. The bicipital groove lies between them.

Surgical neck of the humerusThe narrowed region of the proximal humerus just inferior to the tubercles; a frequent site of fracture because of its relative thinness compared to the head region.

Glenoid cavityThe shallow, oval articular fossa located at the lateral angle of the scapula that forms the socket of the glenohumeral (shoulder) joint.

Acromion processThe lateral extension of the spine of the scapula that projects over the shoulder joint and articulates with the acromial end of the clavicle at the acromioclavicular joint.

Metacarpophalangeal (MCP) jointThe articulation between the distal head of a metacarpal bone and the base of the corresponding proximal phalanx; commonly called the knuckle joint.

ScaphoidThe largest carpal bone of the proximal row, located on the radial (thumb) side; the most frequently fractured carpal bone, with risk of avascular necrosis if injury is undetected.

In class: Label blank skeletal diagrams of each upper extremity segment (fingers through clavicle) without reference, then self-correct using Merrill's Atlas and the textbook; record errors for targeted review. · Compare side-by-side printed radiographs and corresponding anatomical diagrams for the hand, wrist, elbow, and shoulder; annotate each radiograph by writing the name of each visible structure directly on the image. · Build a region-by-region anatomy quiz using digital flashcard software (Anki or equivalent), creating at least 60 cards covering bone names, landmarks, and joint names; quiz a classmate and record scores.
Materials: Merrill's Atlas, skeletal anatomy worksheets, printed or projected radiographic images of upper extremity, articulated upper-extremity bone models, digital flashcard software
Check: Score ≥ 80% on a 50-item image-based identification quiz in which students label structures on unlabeled radiographs of the hand, wrist, elbow, and shoulder; must correctly identify all major bones and at least 80% of listed landmarks.

Practice check8

Answer each question, then check it. Nothing is recorded; this is your own practice.