Upper Limb Osteology — Comprehensive Study Notes Summary & Study Notes

🎯 Objectives

Briefly: identify and orientate all bones of the upper limb, describe their general characteristics, and understand important clinical applications (fractures, palpation, neurovascular risk). These notes follow standard clinically oriented anatomy sources.

🧭 Overview of the Upper Limb

The upper limb is organized into the pectoral girdle (clavicle, scapula, manubrium), shoulder, arm (humerus), forearm (radius and ulna), and hand (carpals, metacarpals, phalanges). Functionally the clavicle acts as a rigid strut, the scapula provides a mobile platform for the humerus, and the radius/ulna form the forearm articulation allowing pronation/supination and wrist function.

🔩 Clavicle — Orientation & Key Features

The clavicle is an S-shaped long bone (no medullary cavity). The sternal end is triangular and enlarged; the acromial end is flattened. The medial two-thirds curve convex anteriorly, lateral third concave.

Important markings: the conoid tubercle and trapezoid line (ligament attachments), subclavian groove (subclavius muscle), and an impression for the costoclavicular ligament. Palpation: clavicle subcutaneous and easy to feel; jugular notch lies between sternal ends.

Clinical: clavicle fractures commonly occur between the middle and lateral thirds from falls on an outstretched hand or direct shoulder impact. The medial fragment is pulled superiorly by sternocleidomastoid, the lateral fragment is pulled inferior-medially by gravity and adductor muscles. In children, greenstick fractures are common.

🛡️ Scapula — Orientation & Surfaces

The scapula is a flat, triangular bone lying over ribs 2–7 on the posterolateral thorax. Major surfaces are the posterior (spine and fossae) and the costal (subscapular fossa). The lateral surface contains the glenoid cavity which articulates with the humeral head.

Posterior landmarks: spine, acromion (articulates with clavicle), deltoid tubercle, and coracoid process. The spine divides the posterior surface into supraspinous and infraspinous fossae.

Borders and angles: superior, medial (vertebral), and lateral (axillary) borders; superior, lateral, and inferior angles. The coracoid process is palpable deep in the clavipectoral (deltopectoral) triangle.

Clinical: scapular fractures are uncommon; if present they often accompany severe trauma and rib fractures. Little treatment is often needed as the scapula is well protected by surrounding muscle.

🦴 Humerus — General & Landmarks

The humerus is the largest bone of the upper limb. Proximally it articulates with the scapula at the glenohumeral joint; distally with the radius and ulna at the elbow.

Proximal features: head, anatomical neck, surgical neck (common fracture site), greater and lesser tubercles, and the intertubercular groove (bicipital groove). The deltoid tuberosity is lateral on the shaft; the radial groove lies posteriorly (for radial nerve).

Distal features: medial and lateral epicondyles, trochlea (medial, for ulna), capitulum (lateral, for radius), and fossae—coronoid, radial, and olecranon.

Surface anatomy: the head is deep in the axilla; the medial epicondyle is prominent and a landmark for the ulnar nerve.

Fractures & nerve injuries: surgical neck fractures risk the axillary nerve; midshaft fractures in the radial groove risk the radial nerve; distal humeral fractures can injure the median nerve; fractures involving the medial epicondyle or medial condyle can affect the ulnar nerve.

🔗 Ulna — Role & Key Features

The ulna is the medial, longer forearm bone and is the primary stabilizer for elbow flexion/extension. It does not articulate in the wrist joint.

Proximal features: olecranon (forms the point of the elbow), coronoid process, and the trochlear notch (articulates with the humerus). The radial notch on the lateral aspect accommodates the head of the radius.

Distal features: a small head and the ulnar styloid process medially. The olecranon is easily palpated and important clinically for assessing elbow alignment and dislocation.

🔁 Radius — Orientation & Function

The radius is lateral and shorter than the ulna; it transmits forces from the wrist to the elbow and rotates around the ulna to allow pronation/supination.

Proximal: disc-shaped head, neck, and radial tuberosity (biceps attachment). Distal: broad and four-sided with the ulnar notch (for the ulna), radial styloid process, and dorsal tubercle.

Surface anatomy: the distal radius is palpable in the anatomical snuffbox (lateral wrist). Clinically important: the radius bears much of the axial load through the interosseous membrane to the ulna.

Fractures: common patterns include Colles’ fracture—a transverse fracture of the distal 2 cm of the radius from a fall on an outstretched, pronated hand, producing a "dinner-fork" deformity. In children, epiphyseal injuries are possible.

🧵 Interosseous Membrane

The interosseous membrane is a thin fibrous sheet between the interosseous borders of the radius and ulna with an oblique fiber orientation. It transmits forces from the radius to the ulna and stabilizes the forearm during load transfer.

Clinically, isolated fractures of one forearm bone can be associated with dislocation of the nearest joint due to force transmission via the interosseous membrane.

✋ Hand — Carpal Bones, Metacarpals, Phalanges

The hand skeleton comprises the carpus (8 carpals), metacarpals (5), and phalanges (3 per finger, 2 in the thumb).

Carpal arrangement (proximal row lateral to medial): Scaphoid, Lunate, Triquetrum, Pisiform. Distal row (lateral to medial): Trapezium, Trapezoid, Capitate, Hamate. Mnemonics: "Sally Left The Party To Take Cathy Home" or variations help recall order.

The scaphoid is the largest proximal carpal and has a tubercle; it is the most frequently fractured carpal bone. Metacarpals form the palm skeleton; the 1st metacarpal (thumb) is short and robust. Phalanges have a base, shaft, and head.

Fractures: scaphoid fractures result from a fall on the palm with the hand abducted; initial X-rays can be negative and should be repeated after 10–14 days due to risk of avascular necrosis of the proximal pole. Hamate fractures can injure the ulnar nerve or artery. A fracture of the 5th metacarpal neck is a common boxer’s fracture. Phalangeal fractures require precise realignment to preserve function.

🩺 Surface Anatomy & Palpation Landmarks

• Clavicle: easily palpable along its length; jugular notch between sternal ends.
• Scapula: superior angle ~T2, root of spine ~T3, inferior angle ~T7.
• Humerus: greater tubercle palpable laterally under deltoid; medial epicondyle prominent at elbow.
• Olecranon: palpable at the elbow, used to judge joint alignment.
• Radial styloid & anatomical snuffbox: landmarks for distal radius/scaphoid palpation.

⚠️ Clinical Pearls

• Repeat imaging for a suspected scaphoid fracture if initial radiographs are negative.
• Observe deformity patterns (e.g., Colles’ dinner-fork deformity) and correlate with mechanism (FOOSH = fall on outstretched hand).
• Know nerve risks: axillary (surgical neck humerus), radial (midshaft humerus), median (distal humerus), ulnar (medial epicondyle/hamate region).
• In clavicle fractures, expect characteristic displacement: medial fragment superior, lateral fragment inferior-medial.

These notes summarize the anatomy, surface landmarks, common fracture patterns, and key clinical correlations for the bones of the upper limb. Use them alongside dissections, imaging, and clinical cases for mastery.